diff --git a/.github/ISSUE_TEMPLATE/crash.md b/.github/ISSUE_TEMPLATE/crash.md
index fed16a8d28ac..ea82a9a28642 100644
--- a/.github/ISSUE_TEMPLATE/crash.md
+++ b/.github/ISSUE_TEMPLATE/crash.md
@@ -15,7 +15,7 @@ labels: "crash"
 
 **Traceback**
 
-```
+```python-traceback
 (Insert traceback and other messages from mypy here -- use `--show-traceback`.)
 ```
 
@@ -25,6 +25,11 @@ labels: "crash"
 appreciated.  We also very much appreciate it if you try to narrow the
 source down to a small stand-alone example.)
 
+```python
+# Ideally, a small sample program that demonstrates the problem.
+# Or even better, a reproducible playground link https://mypy-play.net/ (use the "Gist" button)
+```
+
 **Your Environment**
 
 <!-- Include as many relevant details about the environment you experienced the bug in -->
diff --git a/.github/workflows/mypy_primer.yml b/.github/workflows/mypy_primer.yml
index ee868484751e..1ff984247fb6 100644
--- a/.github/workflows/mypy_primer.yml
+++ b/.github/workflows/mypy_primer.yml
@@ -28,7 +28,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        shard-index: [0, 1, 2, 3, 4]
+        shard-index: [0, 1, 2, 3, 4, 5]
       fail-fast: false
     timeout-minutes: 60
     steps:
@@ -63,7 +63,7 @@ jobs:
             mypy_primer \
             --repo mypy_to_test \
             --new $GITHUB_SHA --old base_commit \
-            --num-shards 5 --shard-index ${{ matrix.shard-index }} \
+            --num-shards 6 --shard-index ${{ matrix.shard-index }} \
             --debug \
             --additional-flags="--debug-serialize" \
             --output concise \
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 97fb7755563b..47f725170bd8 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -37,11 +37,6 @@ jobs:
           toxenv: py
           tox_extra_args: "-n 4"
           test_mypyc: true
-        - name: Test suite with py39-windows-64
-          python: '3.9'
-          os: windows-latest
-          toxenv: py39
-          tox_extra_args: "-n 4"
         - name: Test suite with py310-ubuntu
           python: '3.10'
           os: ubuntu-24.04-arm
@@ -64,6 +59,11 @@ jobs:
           toxenv: py
           tox_extra_args: "-n 4"
           test_mypyc: true
+        - name: Test suite with py313-windows-64
+          python: '3.13'
+          os: windows-latest
+          toxenv: py
+          tox_extra_args: "-n 4"
 
         - name: Test suite with py314-dev-ubuntu
           python: '3.14-dev'
diff --git a/CHANGELOG.md b/CHANGELOG.md
index a1470b7d50c3..134d251d90b1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,11 +2,392 @@
 
 ## Next Release
 
-### Remove Support for targeting Python 3.8
+## Mypy 1.18.1
 
-Mypy now requires `--python-version 3.9` or greater. Support for only Python 3.8 is
-fully removed now. Given an unsupported version, mypy will default to the oldest
-supported one, currently 3.9.
+We’ve just uploaded mypy 1.18.1 to the Python Package Index ([PyPI](https://pypi.org/project/mypy/)).
+Mypy is a static type checker for Python. This release includes new features, performance
+improvements and bug fixes. You can install it as follows:
+
+    python3 -m pip install -U mypy
+
+You can read the full documentation for this release on [Read the Docs](http://mypy.readthedocs.io).
+
+### Mypy Performance Improvements
+
+Mypy 1.18.1 includes numerous performance improvements, resulting in about 40% speedup
+compared to 1.17 when type checking mypy itself. In extreme cases, the improvement
+can be 10x or higher. The list below is an overview of the various mypy optimizations.
+Many mypyc improvements (discussed in a separate section below) also improve performance.
+
+Type caching optimizations have a small risk of causing regressions. When
+reporting issues with unexpected inferred types, please also check if
+`--disable-expression-cache` will work around the issue, as it turns off some of
+these optimizations.
+
+- Improve self check performance by 1.8% (Jukka Lehtosalo, PR [19768](https://github.com/python/mypy/pull/19768), [19769](https://github.com/python/mypy/pull/19769), [19770](https://github.com/python/mypy/pull/19770))
+- Optimize fixed-format deserialization (Ivan Levkivskyi, PR [19765](https://github.com/python/mypy/pull/19765))
+- Use macros to optimize fixed-format deserialization (Ivan Levkivskyi, PR [19757](https://github.com/python/mypy/pull/19757))
+- Two additional micro‑optimizations (Ivan Levkivskyi, PR [19627](https://github.com/python/mypy/pull/19627))
+- Another set of micro‑optimizations (Ivan Levkivskyi, PR [19633](https://github.com/python/mypy/pull/19633))
+- Cache common types (Ivan Levkivskyi, PR [19621](https://github.com/python/mypy/pull/19621))
+- Skip more method bodies in third‑party libraries for speed (Ivan Levkivskyi, PR [19586](https://github.com/python/mypy/pull/19586))
+- Simplify the representation of callable types (Ivan Levkivskyi, PR [19580](https://github.com/python/mypy/pull/19580))
+- Add cache for types of some expressions (Ivan Levkivskyi, PR [19505](https://github.com/python/mypy/pull/19505))
+- Use cache for dictionary expressions (Ivan Levkivskyi, PR [19536](https://github.com/python/mypy/pull/19536))
+- Use cache for binary operations (Ivan Levkivskyi, PR [19523](https://github.com/python/mypy/pull/19523))
+- Cache types of type objects (Ivan Levkivskyi, PR [19514](https://github.com/python/mypy/pull/19514))
+- Avoid duplicate work when checking boolean operations (Ivan Levkivskyi, PR [19515](https://github.com/python/mypy/pull/19515))
+- Optimize generic inference passes (Ivan Levkivskyi, PR [19501](https://github.com/python/mypy/pull/19501))
+- Speed up the default plugin (Jukka Lehtosalo, PRs [19385](https://github.com/python/mypy/pull/19385) and [19462](https://github.com/python/mypy/pull/19462))
+- Remove nested imports from the default plugin (Ivan Levkivskyi, PR [19388](https://github.com/python/mypy/pull/19388))
+- Micro‑optimize type expansion (Jukka Lehtosalo, PR [19461](https://github.com/python/mypy/pull/19461))
+- Micro‑optimize type indirection (Jukka Lehtosalo, PR [19460](https://github.com/python/mypy/pull/19460))
+- Micro‑optimize the plugin framework (Jukka Lehtosalo, PR [19464](https://github.com/python/mypy/pull/19464))
+- Avoid temporary set creation in subtype checking (Jukka Lehtosalo, PR [19463](https://github.com/python/mypy/pull/19463))
+- Subtype checking micro‑optimization (Jukka Lehtosalo, PR [19384](https://github.com/python/mypy/pull/19384))
+- Return early where possible in subtype check (Stanislav Terliakov, PR [19400](https://github.com/python/mypy/pull/19400))
+- Deduplicate some types before joining (Stanislav Terliakov, PR [19409](https://github.com/python/mypy/pull/19409))
+- Speed up type checking by caching argument inference context (Jukka Lehtosalo, PR [19323](https://github.com/python/mypy/pull/19323))
+- Optimize binding method self argument type and deprecation checks (Ivan Levkivskyi, PR [19556](https://github.com/python/mypy/pull/19556))
+- Keep trivial instance types/aliases during expansion (Ivan Levkivskyi, PR [19543](https://github.com/python/mypy/pull/19543))
+
+### Fixed‑Format Cache (Experimental)
+
+Mypy now supports a new cache format used for faster incremental builds. It makes
+incremental builds up to twice as fast. The feature is experimental and
+currently only supported when using a compiled version of mypy. Use `--fixed-format-cache`
+to enable the new format, or `fixed_format_cache = True` in a configuration file.
+
+We plan to enable this by default in a future mypy release, and we'll eventually
+deprecate and remove support for the original JSON-based format.
+
+Unlike the JSON-based cache format, the new binary format is currently
+not easy to parse and inspect by mypy users. We are planning to provide a tool to
+convert fixed-format cache files to JSON, but details of the output JSON may be
+different from the current JSON format. If you rely on being able to inspect
+mypy cache files, we recommend creating a GitHub issue and explaining your use
+case, so that we can more likely provide support for it. (Using
+`MypyFile.read(binary_data)` to inspect cache data may be sufficient to support
+some use cases.)
+
+This feature was contributed by Ivan Levkivskyi (PR [19668](https://github.com/python/mypy/pull/19668), [19735](https://github.com/python/mypy/pull/19735), [19750](https://github.com/python/mypy/pull/19750), [19681](https://github.com/python/mypy/pull/19681), [19752](https://github.com/python/mypy/pull/19752), [19815](https://github.com/python/mypy/pull/19815)).
+
+### Flexible Variable Definitions: Update
+
+Mypy 1.16.0 introduced `--allow-redefinition-new`, which allows redefining variables
+with different types, and inferring union types for variables from multiple assignments.
+The feature is now documented in the `--help` output, but the feature is still experimental.
+
+We are planning to enable this by default in mypy 2.0, and we will also deprecate the
+older `--allow-redefinition` flag. Since the new behavior differs significantly from
+the older flag, we encourage users of `--allow-redefinition` to experiment with
+`--allow-redefinition-new` and create a GitHub issue if the new functionality doesn't
+support some important use cases.
+
+This feature was contributed by Jukka Lehtosalo.
+
+### Inferred Type for Bare ClassVar
+
+A ClassVar without an explicit type annotation now causes the type of the variable
+to be inferred from the initializer:
+
+
+```python
+from typing import ClassVar
+
+class Item:
+    # Type of 'next_id' is now 'int' (it was 'Any')
+    next_id: ClassVar = 1
+
+    ...
+```
+
+This feature was contributed by Ivan Levkivskyi (PR [19573](https://github.com/python/mypy/pull/19573)).
+
+### Disjoint Base Classes (@disjoint_base, PEP 800)
+
+Mypy now understands disjoint bases (PEP 800): it recognizes the `@disjoint_base`
+decorator, and rejects class definitions that combine mutually incompatible base classes,
+and takes advantage of the fact that such classes cannot exist in reachability and
+narrowing logic.
+
+This class definition will now generate an error:
+
+```python
+# Error: Class "Bad" has incompatible disjoint bases
+class Bad(str, Exception):
+    ...
+```
+
+This feature was contributed by Jelle Zijlstra (PR [19678](https://github.com/python/mypy/pull/19678)).
+
+### Miscellaneous New Mypy Features
+
+- Add `--strict-equality-for-none` to flag non-overlapping comparisons involving None (Christoph Tyralla, PR [19718](https://github.com/python/mypy/pull/19718))
+- Don’t show import‑related errors after a module‑level assert such as `assert sys.platform == "linux"` that is always false (Stanislav Terliakov, PR [19347](https://github.com/python/mypy/pull/19347))
+
+### Improvements to Match Statements
+
+- Add temporary named expressions for match subjects (Stanislav Terliakov, PR [18446](https://github.com/python/mypy/pull/18446))
+- Fix unwrapping of assignment expressions in match subject (Marc Mueller, PR [19742](https://github.com/python/mypy/pull/19742))
+- Omit errors for class patterns against object (Marc Mueller, PR [19709](https://github.com/python/mypy/pull/19709))
+- Remove unnecessary error for certain match class patterns (Marc Mueller, PR [19708](https://github.com/python/mypy/pull/19708))
+- Use union type for captured vars in or pattern (Marc Mueller, PR [19710](https://github.com/python/mypy/pull/19710))
+- Prevent final reassignment inside match case (Omer Hadari, PR [19496](https://github.com/python/mypy/pull/19496))
+
+### Fixes to Crashes
+
+- Fix crash with variadic tuple arguments to a generic type (Randolf Scholz, PR [19705](https://github.com/python/mypy/pull/19705))
+- Fix crash when enable_error_code in pyproject.toml has wrong type (wyattscarpenter, PR [19494](https://github.com/python/mypy/pull/19494))
+- Prevent crash for dataclass with PEP 695 TypeVarTuple on Python 3.13+ (Stanislav Terliakov, PR [19565](https://github.com/python/mypy/pull/19565))
+- Fix crash on settable property alias (Ivan Levkivskyi, PR [19615](https://github.com/python/mypy/pull/19615))
+
+### Experimental Free-threading Support for Mypyc
+
+All mypyc tests now pass on free-threading Python 3.14 release candidate builds. The performance
+of various micro-benchmarks scale well across multiple threads.
+
+Free-threading support is still experimental. Note that native attribute access
+(get and set), list item access and certain other operations are still
+unsafe when there are race conditions. This will likely change in the future.
+You can follow the
+[area-free-threading label](https://github.com/mypyc/mypyc/issues?q=is%3Aissue%20state%3Aopen%20label%3Aarea-free-threading)
+in the mypyc issues tracker to follow progress.
+
+Related PRs:
+- Enable free‑threading when compiling multiple modules (Jukka Lehtosalo, PR [19541](https://github.com/python/mypy/pull/19541))
+- Fix `list.pop` on free‑threaded builds (Jukka Lehtosalo, PR [19522](https://github.com/python/mypy/pull/19522))
+- Make type objects immortal under free‑threading (Jukka Lehtosalo, PR [19538](https://github.com/python/mypy/pull/19538))
+
+### Mypyc: Support `__new__`
+
+Mypyc now has rudimentary support for user-defined `__new__` methods.
+
+This feature was contributed by Piotr Sawicki (PR [19739](https://github.com/python/mypy/pull/19739)).
+
+### Mypyc: Faster Generators and Async Functions
+
+Generators and calls of async functions are now faster, sometimes by 2x or more.
+
+Related PRs:
+- Speed up for loops over native generators (Jukka Lehtosalo, PR [19415](https://github.com/python/mypy/pull/19415))
+- Speed up native‑to‑native calls using await (Jukka Lehtosalo, PR [19398](https://github.com/python/mypy/pull/19398))
+- Call generator helper directly in await expressions (Jukka Lehtosalo, PR [19376](https://github.com/python/mypy/pull/19376))
+- Speed up generator allocation with per‑type freelists (Jukka Lehtosalo, PR [19316](https://github.com/python/mypy/pull/19316))
+
+### Miscellaneous Mypyc Improvements
+
+- Special‑case certain Enum method calls for speed (Ivan Levkivskyi, PR [19634](https://github.com/python/mypy/pull/19634))
+- Fix issues related to subclassing and undefined attribute tracking (Chainfire, PR [19787](https://github.com/python/mypy/pull/19787))
+- Fix invalid C function signature (Jukka Lehtosalo, PR [19773](https://github.com/python/mypy/pull/19773))
+- Speed up implicit `__ne__` (Jukka Lehtosalo, PR [19759](https://github.com/python/mypy/pull/19759))
+- Speed up equality with optional str/bytes types (Jukka Lehtosalo, PR [19758](https://github.com/python/mypy/pull/19758))
+- Speed up access to empty tuples (BobTheBuidler, PR [19654](https://github.com/python/mypy/pull/19654))
+- Speed up calls with `*args` (BobTheBuidler, PRs [19623](https://github.com/python/mypy/pull/19623) and [19631](https://github.com/python/mypy/pull/19631))
+- Speed up calls with `**kwargs` (BobTheBuidler, PR [19630](https://github.com/python/mypy/pull/19630))
+- Optimize `type(x)`, `x.__class__`, and `<type>.__name__` (Jukka Lehtosalo, PR [19691](https://github.com/python/mypy/pull/19691), [19683](https://github.com/python/mypy/pull/19683))
+- Specialize `bytes.decode` for common encodings (Jukka Lehtosalo, PR [19688](https://github.com/python/mypy/pull/19688))
+- Speed up `in` operations using final fixed‑length tuples (Jukka Lehtosalo, PR [19682](https://github.com/python/mypy/pull/19682))
+- Optimize f‑string building from final values (BobTheBuidler, PR [19611](https://github.com/python/mypy/pull/19611))
+- Add dictionary set item for exact dict instances (BobTheBuidler, PR [19657](https://github.com/python/mypy/pull/19657))
+- Cache length when iterating over immutable types (BobTheBuidler, PR [19656](https://github.com/python/mypy/pull/19656))
+- Fix name conflict related to attributes of generator classes (Piotr Sawicki, PR [19535](https://github.com/python/mypy/pull/19535))
+- Fix segfault from heap type objects with a static docstring (Brian Schubert, PR [19636](https://github.com/python/mypy/pull/19636))
+- Unwrap NewType to its base type for additional optimizations (BobTheBuidler, PR [19497](https://github.com/python/mypy/pull/19497))
+- Generate an export table only for separate compilation (Jukka Lehtosalo, PR [19521](https://github.com/python/mypy/pull/19521))
+- Speed up `isinstance` with built‑in types (Piotr Sawicki, PR [19435](https://github.com/python/mypy/pull/19435))
+- Use native integers for some sequence indexing (Jukka Lehtosalo, PR [19426](https://github.com/python/mypy/pull/19426))
+- Speed up `isinstance(obj, list)` (Piotr Sawicki, PR [19416](https://github.com/python/mypy/pull/19416))
+- Report error on reserved method names (Piotr Sawicki, PR [19407](https://github.com/python/mypy/pull/19407))
+- Speed up string equality (Jukka Lehtosalo, PR [19402](https://github.com/python/mypy/pull/19402))
+- Raise `NameError` on undefined names (Piotr Sawicki, PR [19395](https://github.com/python/mypy/pull/19395))
+- Use per‑type freelists for nested functions (Jukka Lehtosalo, PR [19390](https://github.com/python/mypy/pull/19390))
+- Simplify comparison of tuple elements (Piotr Sawicki, PR [19396](https://github.com/python/mypy/pull/19396))
+- Generate introspection signatures for compiled functions (Brian Schubert, PR [19307](https://github.com/python/mypy/pull/19307))
+- Fix undefined attribute checking special case (Jukka Lehtosalo, PR [19378](https://github.com/python/mypy/pull/19378))
+- Fix comparison of tuples with different lengths (Piotr Sawicki, PR [19372](https://github.com/python/mypy/pull/19372))
+- Speed up `list.clear` (Jahongir Qurbonov, PR [19344](https://github.com/python/mypy/pull/19344))
+- Speed up `weakref.proxy` (BobTheBuidler, PR [19217](https://github.com/python/mypy/pull/19217))
+- Speed up `weakref.ref` (BobTheBuidler, PR [19099](https://github.com/python/mypy/pull/19099))
+- Speed up `str.count` (BobTheBuidler, PR [19264](https://github.com/python/mypy/pull/19264))
+
+### Stubtest Improvements
+- Add temporary `--ignore-disjoint-bases` flag to ease PEP 800 migration (Joren Hammudoglu, PR [19740](https://github.com/python/mypy/pull/19740))
+- Flag redundant uses of `@disjoint_base` (Jelle Zijlstra, PR [19715](https://github.com/python/mypy/pull/19715))
+- Improve signatures for `__init__` of C extension classes (Stephen Morton, PR [18259](https://github.com/python/mypy/pull/18259))
+- Handle overloads with mixed positional‑only parameters (Stephen Morton, PR [18287](https://github.com/python/mypy/pull/18287))
+- Use “parameter” (not “argument”) in error messages (PrinceNaroliya, PR [19707](https://github.com/python/mypy/pull/19707))
+- Don’t require `@disjoint_base` when `__slots__` imply finality (Jelle Zijlstra, PR [19701](https://github.com/python/mypy/pull/19701))
+- Allow runtime‑existing aliases of `@type_check_only` types (Brian Schubert, PR [19568](https://github.com/python/mypy/pull/19568))
+- More detailed checking of type objects in stubtest (Stephen Morton, PR [18251](https://github.com/python/mypy/pull/18251))
+- Support running stubtest in non-UTF8 terminals (Stanislav Terliakov, PR [19085](https://github.com/python/mypy/pull/19085))
+
+### Documentation Updates
+
+- Add idlemypyextension to IDE integrations (CoolCat467, PR [18615](https://github.com/python/mypy/pull/18615))
+- Document that `object` is often preferable to `Any` in APIs (wyattscarpenter, PR [19103](https://github.com/python/mypy/pull/19103))
+- Include a detailed listing of flags enabled by `--strict` (wyattscarpenter, PR [19062](https://github.com/python/mypy/pull/19062))
+- Update “common issues” (reveal_type/reveal_locals; note on orjson) (wyattscarpenter, PR [19059](https://github.com/python/mypy/pull/19059), [19058](https://github.com/python/mypy/pull/19058))
+
+### Other Notable Fixes and Improvements
+
+- Remove deprecated `--new-type-inference` flag (the new algorithm has long been default) (Ivan Levkivskyi, PR [19570](https://github.com/python/mypy/pull/19570))
+- Use empty context as a fallback for return expressions when outer context misleads inference (Ivan Levkivskyi, PR [19767](https://github.com/python/mypy/pull/19767))
+- Fix forward references in type parameters of over‑parameterized PEP 695 aliases (Brian Schubert, PR [19725](https://github.com/python/mypy/pull/19725))
+- Don’t expand PEP 695 aliases when checking node fullnames (Brian Schubert, PR [19699](https://github.com/python/mypy/pull/19699))
+- Don’t use outer context for 'or' expression inference when LHS is Any (Stanislav Terliakov, PR [19748](https://github.com/python/mypy/pull/19748))
+- Recognize buffer protocol special methods (Brian Schubert, PR [19581](https://github.com/python/mypy/pull/19581))
+- Support attribute access on enum members correctly (Stanislav Terliakov, PR [19422](https://github.com/python/mypy/pull/19422))
+- Check `__slots__` assignments on self types (Stanislav Terliakov, PR [19332](https://github.com/python/mypy/pull/19332))
+- Move self‑argument checks after decorator application (Stanislav Terliakov, PR [19490](https://github.com/python/mypy/pull/19490))
+- Infer empty list for `__slots__` and module `__all__` (Stanislav Terliakov, PR [19348](https://github.com/python/mypy/pull/19348))
+- Use normalized tuples for fallback calculation (Stanislav Terliakov, PR [19111](https://github.com/python/mypy/pull/19111))
+- Preserve literals when joining similar types (Stanislav Terliakov, PR [19279](https://github.com/python/mypy/pull/19279))
+- Allow adjacent conditionally‑defined overloads (Stanislav Terliakov, PR [19042](https://github.com/python/mypy/pull/19042))
+- Check property decorators more strictly (Stanislav Terliakov, PR [19313](https://github.com/python/mypy/pull/19313))
+- Support properties with generic setters (Ivan Levkivskyi, PR [19298](https://github.com/python/mypy/pull/19298))
+- Generalize class/static method and property alias support (Ivan Levkivskyi, PR [19297](https://github.com/python/mypy/pull/19297))
+- Re‑widen custom properties after narrowing (Ivan Levkivskyi, PR [19296](https://github.com/python/mypy/pull/19296))
+- Avoid erasing type objects when checking runtime cover (Shantanu, PR [19320](https://github.com/python/mypy/pull/19320))
+- Include tuple fallback in constraints built from tuple types (Stanislav Terliakov, PR [19100](https://github.com/python/mypy/pull/19100))
+- Somewhat better isinstance support on old‑style unions (Shantanu, PR [19714](https://github.com/python/mypy/pull/19714))
+- Improve promotions inside unions (Christoph Tyralla, PR [19245](https://github.com/python/mypy/pull/19245))
+- Treat uninhabited types as having all attributes (Ivan Levkivskyi, PR [19300](https://github.com/python/mypy/pull/19300))
+- Improve metaclass conflict checks (Robsdedude, PR [17682](https://github.com/python/mypy/pull/17682))
+- Fixes to metaclass resolution algorithm (Robsdedude, PR [17713](https://github.com/python/mypy/pull/17713))
+- PEP 702 @deprecated: handle “combined” overloads (Christoph Tyralla, PR [19626](https://github.com/python/mypy/pull/19626))
+- PEP 702 @deprecated: include overloads in snapshot descriptions (Christoph Tyralla, PR [19613](https://github.com/python/mypy/pull/19613))
+- Ignore overload implementation when checking `__OP__` / `__rOP__` compatibility (Stanislav Terliakov, PR [18502](https://github.com/python/mypy/pull/18502))
+- Support `_value_` as a fallback for ellipsis Enum members (Stanislav Terliakov, PR [19352](https://github.com/python/mypy/pull/19352))
+- Sort arguments in TypedDict overlap messages (Marc Mueller, PR [19666](https://github.com/python/mypy/pull/19666))
+- Fix handling of implicit return in lambda (Stanislav Terliakov, PR [19642](https://github.com/python/mypy/pull/19642))
+- Improve behavior of uninhabited types (Stanislav Terliakov, PR [19648](https://github.com/python/mypy/pull/19648))
+- Fix overload diagnostics when `*args` and `**kwargs` both match (Shantanu, PR [19614](https://github.com/python/mypy/pull/19614))
+- Further fix overload diagnostics for `*args`/`**kwargs` (Shantanu, PR [19619](https://github.com/python/mypy/pull/19619))
+- Show type variable name in "Cannot infer type argument" (Brian Schubert, PR [19290](https://github.com/python/mypy/pull/19290))
+- Fail gracefully on unsupported template strings (PEP 750) (Brian Schubert, PR [19700](https://github.com/python/mypy/pull/19700))
+- Revert colored argparse help for Python 3.14 (Marc Mueller, PR [19721](https://github.com/python/mypy/pull/19721))
+- Update stubinfo for latest typeshed (Shantanu, PR [19771](https://github.com/python/mypy/pull/19771))
+- Fix dict assignment when an incompatible same‑shape TypedDict exists (Stanislav Terliakov, PR [19592](https://github.com/python/mypy/pull/19592))
+- Fix constructor type for subclasses of Any (Ivan Levkivskyi, PR [19295](https://github.com/python/mypy/pull/19295))
+- Fix TypeGuard/TypeIs being forgotten in some cases (Brian Schubert, PR [19325](https://github.com/python/mypy/pull/19325))
+- Fix TypeIs negative narrowing for unions of generics (Brian Schubert, PR [18193](https://github.com/python/mypy/pull/18193))
+- dmypy suggest: Fix incorrect signature suggestion when a type matches a module name (Brian Schubert, PR [18937](https://github.com/python/mypy/pull/18937))
+- dmypy suggest: Fix interaction with `__new__` (Stanislav Terliakov, PR [18966](https://github.com/python/mypy/pull/18966))
+- dmypy suggest: Support Callable / callable Protocols in decorator unwrapping (Anthony Sottile, PR [19072](https://github.com/python/mypy/pull/19072))
+- Fix missing error when redeclaring a type variable in a nested generic class (Brian Schubert, PR [18883](https://github.com/python/mypy/pull/18883))
+- Fix for overloaded type object erasure (Shantanu, PR [19338](https://github.com/python/mypy/pull/19338))
+- Fix TypeGuard with call on temporary object (Saul Shanabrook, PR [19577](https://github.com/python/mypy/pull/19577))
+
+### Typeshed Updates
+
+Please see [git log](https://github.com/python/typeshed/commits/main?after=2480d7e7c74493a024eaf254c5d2c6f452c80ee2+0&branch=main&path=stdlib) for full list of standard library typeshed stub changes.
+
+### Mypy 1.18.2
+
+- Fix crash on recursive alias (Ivan Levkivskyi, PR [19845](https://github.com/python/mypy/pull/19845))
+- Add additional guidance for stubtest errors when runtime is `object.__init__` (Stephen Morton, PR [19733](https://github.com/python/mypy/pull/19733))
+- Fix handling of None values in f-string expressions in mypyc (BobTheBuidler, PR [19846](https://github.com/python/mypy/pull/19846))
+
+### Acknowledgements
+
+Thanks to all mypy contributors who contributed to this release:
+
+- Ali Hamdan
+- Anthony Sottile
+- BobTheBuidler
+- Brian Schubert
+- Chainfire
+- Charlie Denton
+- Christoph Tyralla
+- CoolCat467
+- Daniel Hnyk
+- Emily
+- Emma Smith
+- Ethan Sarp
+- Ivan Levkivskyi
+- Jahongir Qurbonov
+- Jelle Zijlstra
+- Joren Hammudoglu
+- Jukka Lehtosalo
+- Marc Mueller
+- Omer Hadari
+- Piotr Sawicki
+- PrinceNaroliya
+- Randolf Scholz
+- Robsdedude
+- Saul Shanabrook
+- Shantanu
+- Stanislav Terliakov
+- Stephen Morton
+- wyattscarpenter
+
+I’d also like to thank my employer, Dropbox, for supporting mypy development.
+
+## Mypy 1.17
+
+We’ve just uploaded mypy 1.17 to the Python Package Index ([PyPI](https://pypi.org/project/mypy/)).
+Mypy is a static type checker for Python. This release includes new features and bug fixes.
+You can install it as follows:
+
+    python3 -m pip install -U mypy
+
+You can read the full documentation for this release on [Read the Docs](http://mypy.readthedocs.io).
+
+### Optionally Check That Match Is Exhaustive
+
+Mypy can now optionally generate an error if a match statement does not
+match exhaustively, without having to use `assert_never(...)`. Enable
+this by using `--enable-error-code exhaustive-match`.
+
+Example:
+
+```python
+# mypy: enable-error-code=exhaustive-match
+
+import enum
+
+class Color(enum.Enum):
+    RED = 1
+    BLUE = 2
+
+def show_color(val: Color) -> None:
+    # error: Unhandled case for values of type "Literal[Color.BLUE]"
+    match val:
+        case Color.RED:
+            print("red")
+```
+
+This feature was contributed by Donal Burns (PR [19144](https://github.com/python/mypy/pull/19144)).
+
+### Further Improvements to Attribute Resolution
+
+This release includes additional improvements to how attribute types
+and kinds are resolved. These fix many bugs and overall improve consistency.
+
+* Handle corner case: protocol/class variable/descriptor (Ivan Levkivskyi, PR [19277](https://github.com/python/mypy/pull/19277))
+* Fix a few inconsistencies in protocol/type object interactions (Ivan Levkivskyi, PR [19267](https://github.com/python/mypy/pull/19267))
+* Refactor/unify access to static attributes (Ivan Levkivskyi, PR [19254](https://github.com/python/mypy/pull/19254))
+* Remove inconsistencies in operator handling (Ivan Levkivskyi, PR [19250](https://github.com/python/mypy/pull/19250))
+* Make protocol subtyping more consistent (Ivan Levkivskyi, PR [18943](https://github.com/python/mypy/pull/18943))
+
+### Fixes to Nondeterministic Type Checking
+
+Previous mypy versions could infer different types for certain expressions
+across different runs (typically depending on which order certain types
+were processed, and this order was nondeterministic). This release includes
+fixes to several such issues.
+
+* Fix nondeterministic type checking by making join with explicit Protocol and type promotion commute (Shantanu, PR [18402](https://github.com/python/mypy/pull/18402))
+* Fix nondeterministic type checking caused by nonassociative of None joins (Shantanu, PR [19158](https://github.com/python/mypy/pull/19158))
+* Fix nondeterministic type checking caused by nonassociativity of joins (Shantanu, PR [19147](https://github.com/python/mypy/pull/19147))
+* Fix nondeterministic type checking by making join between `type` and TypeVar commute (Shantanu, PR [19149](https://github.com/python/mypy/pull/19149))
+
+### Remove Support for Targeting Python 3.8
+
+Mypy now requires `--python-version 3.9` or greater. Support for targeting Python 3.8 is
+fully removed now. Since 3.8 is an unsupported version, mypy will default to the oldest
+supported version (currently 3.9) if you still try to target 3.8.
 
 This change is necessary because typeshed stopped supporting Python 3.8 after it
 reached its End of Life in October 2024.
@@ -17,18 +398,133 @@ Contributed by Marc Mueller
 ### Initial Support for Python 3.14
 
 Mypy is now tested on 3.14 and mypyc works with 3.14.0b3 and later.
-Mypyc compiled wheels of mypy itself will be available for new versions after 3.14.0rc1 is released.
+Binary wheels compiled with mypyc for mypy itself will be available for 3.14
+some time after 3.14.0rc1 has been released.
 
-Note that not all new features might be supported just yet.
+Note that not all features are supported just yet.
 
 Contributed by Marc Mueller (PR [19164](https://github.com/python/mypy/pull/19164))
 
-### Deprecated Flag: \--force-uppercase-builtins
+### Deprecated Flag: `--force-uppercase-builtins`
 
-Mypy only supports Python 3.9+. The \--force-uppercase-builtins flag is now deprecated and a no-op. It will be removed in a future version.
+Mypy only supports Python 3.9+. The `--force-uppercase-builtins` flag is now
+deprecated as unnecessary, and a no-op. It will be removed in a future version.
 
 Contributed by Marc Mueller (PR [19176](https://github.com/python/mypy/pull/19176))
 
+### Mypyc: Improvements to Generators and Async Functions
+
+This release includes both performance improvements and bug fixes related
+to generators and async functions (these share many implementation details).
+
+* Fix exception swallowing in async try/finally blocks with await (Chainfire, PR [19353](https://github.com/python/mypy/pull/19353))
+* Fix AttributeError in async try/finally with mixed return paths (Chainfire, PR [19361](https://github.com/python/mypy/pull/19361))
+* Make generated generator helper method internal (Jukka Lehtosalo, PR [19268](https://github.com/python/mypy/pull/19268))
+* Free coroutine after await encounters StopIteration (Jukka Lehtosalo, PR [19231](https://github.com/python/mypy/pull/19231))
+* Use non-tagged integer for generator label (Jukka Lehtosalo, PR [19218](https://github.com/python/mypy/pull/19218))
+* Merge generator and environment classes in simple cases (Jukka Lehtosalo, PR [19207](https://github.com/python/mypy/pull/19207))
+
+### Mypyc: Partial, Unsafe Support for Free Threading
+
+Mypyc has minimal, quite memory-unsafe support for the free threaded
+builds of 3.14. It is also only lightly tested. Bug reports and experience
+reports are welcome!
+
+Here are some of the major limitations:
+* Free threading only works when compiling a single module at a time.
+* If there is concurrent access to an object while another thread is mutating the same
+  object, it's possible to encounter segfaults and memory corruption.
+* There are no efficient native primitives for thread synthronization, though the
+  regular `threading` module can be used.
+* Some workloads don't scale well to multiple threads for no clear reason.
+
+Related PRs:
+
+* Enable partial, unsafe support for free-threading (Jukka Lehtosalo, PR [19167](https://github.com/python/mypy/pull/19167))
+* Fix incref/decref on free-threaded builds (Jukka Lehtosalo, PR [19127](https://github.com/python/mypy/pull/19127))
+
+### Other Mypyc Fixes and Improvements
+
+* Derive .c file name from full module name if using multi_file (Jukka Lehtosalo, PR [19278](https://github.com/python/mypy/pull/19278))
+* Support overriding the group name used in output files (Jukka Lehtosalo, PR [19272](https://github.com/python/mypy/pull/19272))
+* Add note about using non-native class to subclass built-in types (Jukka Lehtosalo, PR [19236](https://github.com/python/mypy/pull/19236))
+* Make some generated classes implicitly final (Jukka Lehtosalo, PR [19235](https://github.com/python/mypy/pull/19235))
+* Don't simplify module prefixes if using separate compilation (Jukka Lehtosalo, PR [19206](https://github.com/python/mypy/pull/19206))
+
+### Stubgen Improvements
+
+* Add import for `types` in `__exit__` method signature (Alexey Makridenko, PR [19120](https://github.com/python/mypy/pull/19120))
+* Add support for including class and property docstrings (Chad Dombrova, PR [17964](https://github.com/python/mypy/pull/17964))
+* Don't generate `Incomplete | None = None` argument annotation (Sebastian Rittau, PR [19097](https://github.com/python/mypy/pull/19097))
+* Support several more constructs in stubgen's alias printer (Stanislav Terliakov, PR [18888](https://github.com/python/mypy/pull/18888))
+
+### Miscellaneous Fixes and Improvements
+
+* Combine the revealed types of multiple iteration steps in a more robust manner (Christoph Tyralla, PR [19324](https://github.com/python/mypy/pull/19324))
+* Improve the handling of "iteration dependent" errors and notes in finally clauses (Christoph Tyralla, PR [19270](https://github.com/python/mypy/pull/19270))
+* Lessen dmypy suggest path limitations for Windows machines (CoolCat467, PR [19337](https://github.com/python/mypy/pull/19337))
+* Fix type ignore comments erroneously marked as unused by dmypy (Charlie Denton, PR [15043](https://github.com/python/mypy/pull/15043))
+* Fix misspelled `exhaustive-match` error code (johnthagen, PR [19276](https://github.com/python/mypy/pull/19276))
+* Fix missing error context for unpacking assignment involving star expression (Brian Schubert, PR [19258](https://github.com/python/mypy/pull/19258))
+* Fix and simplify error de-duplication (Ivan Levkivskyi, PR [19247](https://github.com/python/mypy/pull/19247))
+* Disallow `ClassVar` in type aliases (Brian Schubert, PR [19263](https://github.com/python/mypy/pull/19263))
+* Add script that prints list of compiled files when compiling mypy (Jukka Lehtosalo, PR [19260](https://github.com/python/mypy/pull/19260))
+* Fix help message url for "None and Optional handling" section (Guy Wilson, PR [19252](https://github.com/python/mypy/pull/19252))
+* Display fully qualified name of imported base classes in errors about incompatible overrides (Mikhail Golubev, PR [19115](https://github.com/python/mypy/pull/19115))
+* Avoid false `unreachable`, `redundant-expr`, and `redundant-casts` warnings in loops more robustly and efficiently, and avoid multiple `revealed type` notes for the same line (Christoph Tyralla, PR [19118](https://github.com/python/mypy/pull/19118))
+* Fix type extraction from `isinstance` checks (Stanislav Terliakov, PR [19223](https://github.com/python/mypy/pull/19223))
+* Erase stray type variables in `functools.partial` (Stanislav Terliakov, PR [18954](https://github.com/python/mypy/pull/18954))
+* Make inferring condition value recognize the whole truth table (Stanislav Terliakov, PR [18944](https://github.com/python/mypy/pull/18944))
+* Support type aliases, `NamedTuple` and `TypedDict` in constrained TypeVar defaults (Stanislav Terliakov, PR [18884](https://github.com/python/mypy/pull/18884))
+* Move dataclass `kw_only` fields to the end of the signature (Stanislav Terliakov, PR [19018](https://github.com/python/mypy/pull/19018))
+* Provide a better fallback value for the `python_version` option (Marc Mueller, PR [19162](https://github.com/python/mypy/pull/19162))
+* Avoid spurious non-overlapping equality error with metaclass with `__eq__` (Michael J. Sullivan, PR [19220](https://github.com/python/mypy/pull/19220))
+* Narrow type variable bounds (Ivan Levkivskyi, PR [19183](https://github.com/python/mypy/pull/19183))
+* Add classifier for Python 3.14 (Marc Mueller, PR [19199](https://github.com/python/mypy/pull/19199))
+* Capitalize syntax error messages (Charulata, PR [19114](https://github.com/python/mypy/pull/19114))
+* Infer constraints eagerly if actual is Any (Ivan Levkivskyi, PR [19190](https://github.com/python/mypy/pull/19190))
+* Include walrus assignments in conditional inference (Stanislav Terliakov, PR [19038](https://github.com/python/mypy/pull/19038))
+* Use PEP 604 syntax when converting types to strings (Marc Mueller, PR [19179](https://github.com/python/mypy/pull/19179))
+* Use more lower-case builtin types in error messages (Marc Mueller, PR [19177](https://github.com/python/mypy/pull/19177))
+* Fix example to use correct method of Stack (Łukasz Kwieciński, PR [19123](https://github.com/python/mypy/pull/19123))
+* Forbid `.pop` of `Readonly` `NotRequired` TypedDict items (Stanislav Terliakov, PR [19133](https://github.com/python/mypy/pull/19133))
+* Emit a friendlier warning on invalid exclude regex, instead of a stacktrace (wyattscarpenter, PR [19102](https://github.com/python/mypy/pull/19102))
+* Enable ANSI color codes for dmypy client in Windows (wyattscarpenter, PR [19088](https://github.com/python/mypy/pull/19088))
+* Extend special case for context-based type variable inference to unions in return position (Stanislav Terliakov, PR [18976](https://github.com/python/mypy/pull/18976))
+
+### Mypy 1.17.1
+* Retain `None` as constraints bottom if no bottoms were provided (Stanislav Terliakov, PR [19485](https://github.com/python/mypy/pull/19485))
+* Fix "ignored exception in `hasattr`" in dmypy (Stanislav Terliakov, PR [19428](https://github.com/python/mypy/pull/19428))
+* Prevent a crash when InitVar is redefined with a method in a subclass (Stanislav Terliakov, PR [19453](https://github.com/python/mypy/pull/19453))
+
+### Acknowledgements
+
+Thanks to all mypy contributors who contributed to this release:
+
+* Alexey Makridenko
+* Brian Schubert
+* Chad Dombrova
+* Chainfire
+* Charlie Denton
+* Charulata
+* Christoph Tyralla
+* CoolCat467
+* Donal Burns
+* Guy Wilson
+* Ivan Levkivskyi
+* johnthagen
+* Jukka Lehtosalo
+* Łukasz Kwieciński
+* Marc Mueller
+* Michael J. Sullivan
+* Mikhail Golubev
+* Sebastian Rittau
+* Shantanu
+* Stanislav Terliakov
+* wyattscarpenter
+
+I’d also like to thank my employer, Dropbox, for supporting mypy development.
+
 ## Mypy 1.16
 
 We’ve just uploaded mypy 1.16 to the Python Package Index ([PyPI](https://pypi.org/project/mypy/)).
diff --git a/README.md b/README.md
index 45b71c8a4824..8040566b18ef 100644
--- a/README.md
+++ b/README.md
@@ -142,6 +142,7 @@ Mypy can be integrated into popular IDEs:
 - Emacs: using [Flycheck](https://github.com/flycheck/)
 - Sublime Text: [SublimeLinter-contrib-mypy](https://github.com/fredcallaway/SublimeLinter-contrib-mypy)
 - PyCharm: [mypy plugin](https://github.com/dropbox/mypy-PyCharm-plugin)
+- IDLE: [idlemypyextension](https://github.com/CoolCat467/idlemypyextension)
 - pre-commit: use [pre-commit mirrors-mypy](https://github.com/pre-commit/mirrors-mypy), although
   note by default this will limit mypy's ability to analyse your third party dependencies.
 
diff --git a/docs/requirements-docs.txt b/docs/requirements-docs.txt
index 747f376a8f5a..09062a635e63 100644
--- a/docs/requirements-docs.txt
+++ b/docs/requirements-docs.txt
@@ -1,3 +1,4 @@
+-r ../mypy-requirements.txt
 sphinx>=8.1.0
 furo>=2022.3.4
 myst-parser>=4.0.0
diff --git a/docs/source/command_line.rst b/docs/source/command_line.rst
index 697e0fb69eed..c1b757a00ef2 100644
--- a/docs/source/command_line.rst
+++ b/docs/source/command_line.rst
@@ -728,9 +728,22 @@ of the above sections.
        if text != b'other bytes':  # Error: non-overlapping equality check!
            ...
 
-       assert text is not None  # OK, check against None is allowed as a special case.
+       assert text is not None  # OK, check against None is allowed
 
 
+.. option:: --strict-equality-for-none
+
+    This flag extends :option:`--strict-equality <mypy --strict-equality>` for checks
+    against ``None``:
+
+    .. code-block:: python
+
+       text: str
+       assert text is not None  # Error: non-overlapping identity check!
+
+    Note that :option:`--strict-equality-for-none <mypy --strict-equality-for-none>`
+    only works in combination with :option:`--strict-equality <mypy --strict-equality>`.
+
 .. option:: --strict-bytes
 
     By default, mypy treats ``bytearray`` and ``memoryview`` as subtypes of ``bytes`` which
@@ -812,6 +825,14 @@ of the above sections.
     Note: the exact list of flags enabled by running :option:`--strict` may change
     over time.
 
+    .. include:: strict_list.rst
+    ..
+        The above file is autogenerated and included during html generation.
+        (That's an include directive, and this is a comment.)
+        It would be fine to generate it at some other time instead,
+        theoretically, but we already had a convenient hook during html gen.
+
+
 .. option:: --disable-error-code
 
     This flag allows disabling one or multiple error codes globally.
diff --git a/docs/source/common_issues.rst b/docs/source/common_issues.rst
index 96d73e5f0399..aa325dd3b05c 100644
--- a/docs/source/common_issues.rst
+++ b/docs/source/common_issues.rst
@@ -218,6 +218,14 @@ daemon <mypy_daemon>`, which can speed up incremental mypy runtimes by
 a factor of 10 or more. :ref:`Remote caching <remote-cache>` can
 make cold mypy runs several times faster.
 
+Furthermore: as of `mypy 1.13 <https://mypy-lang.blogspot.com/2024/10/mypy-113-released.html>`_,
+mypy allows use of the orjson library for handling the cache instead of the stdlib json, for
+improved performance. You can ensure the presence of orjson using the faster-cache extra:
+
+    python3 -m pip install -U mypy[faster-cache]
+
+Mypy may depend on orjson by default in the future.
+
 Types of empty collections
 --------------------------
 
@@ -505,11 +513,15 @@ to see the types of all local variables at once. Example:
    #     b: builtins.str
 .. note::
 
-   ``reveal_type`` and ``reveal_locals`` are only understood by mypy and
-   don't exist in Python. If you try to run your program, you'll have to
-   remove any ``reveal_type`` and ``reveal_locals`` calls before you can
-   run your code. Both are always available and you don't need to import
-   them.
+    ``reveal_type`` and ``reveal_locals`` are handled specially by mypy during
+    type checking, and don't have to be defined or imported.
+
+    However, if you want to run your code,
+    you'll have to remove any ``reveal_type`` and ``reveal_locals``
+    calls from your program or else Python will give you an error at runtime.
+
+    Alternatively, you can import ``reveal_type`` from ``typing_extensions``
+    or ``typing`` (on Python 3.11 and newer)
 
 .. _silencing-linters:
 
diff --git a/docs/source/conf.py b/docs/source/conf.py
index 79a5c0619615..02caa44dce11 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -278,9 +278,9 @@
 intersphinx_mapping = {
     "python": ("https://docs.python.org/3", None),
     "attrs": ("https://www.attrs.org/en/stable/", None),
-    "cython": ("https://docs.cython.org/en/latest", None),
+    "cython": ("https://cython.readthedocs.io/en/stable", None),
     "monkeytype": ("https://monkeytype.readthedocs.io/en/latest", None),
-    "setuptools": ("https://setuptools.readthedocs.io/en/latest", None),
+    "setuptools": ("https://setuptools.pypa.io/en/latest", None),
 }
 
 
diff --git a/docs/source/config_file.rst b/docs/source/config_file.rst
index b4f134f26cb1..934e465a7c23 100644
--- a/docs/source/config_file.rst
+++ b/docs/source/config_file.rst
@@ -834,7 +834,15 @@ section of the command line docs.
    :default: False
 
    Prohibit equality checks, identity checks, and container checks between
-   non-overlapping types.
+   non-overlapping types (except ``None``).
+
+.. confval:: strict_equality_for_none
+
+   :type: boolean
+   :default: False
+
+   Include ``None`` in strict equality checks (requires :confval:`strict_equality`
+   to be activated).
 
 .. confval:: strict_bytes
 
diff --git a/docs/source/dynamic_typing.rst b/docs/source/dynamic_typing.rst
index 304e25c085a8..da40142d377d 100644
--- a/docs/source/dynamic_typing.rst
+++ b/docs/source/dynamic_typing.rst
@@ -1,6 +1,5 @@
 .. _dynamic-typing:
 
-
 Dynamically typed code
 ======================
 
@@ -94,6 +93,8 @@ third party libraries that mypy does not know about. This is particularly the ca
 when using the :option:`--ignore-missing-imports <mypy --ignore-missing-imports>`
 flag. See :ref:`fix-missing-imports` for more information about this.
 
+.. _any-vs-object:
+
 Any vs. object
 --------------
 
diff --git a/docs/source/error_code_list.rst b/docs/source/error_code_list.rst
index 49cb8a0c06c1..6deed549c2f1 100644
--- a/docs/source/error_code_list.rst
+++ b/docs/source/error_code_list.rst
@@ -215,6 +215,35 @@ You can use :py:class:`~collections.abc.Callable` as the type for callable objec
         for x in objs:
             f(x)
 
+.. _code-metaclass:
+
+Check the validity of a class's metaclass [metaclass]
+-----------------------------------------------------
+
+Mypy checks whether the metaclass of a class is valid. The metaclass
+must be a subclass of ``type``. Further, the class hierarchy must yield
+a consistent metaclass. For more details, see the
+`Python documentation <https://docs.python.org/3.13/reference/datamodel.html#determining-the-appropriate-metaclass>`_
+
+Note that mypy's metaclass checking is limited and may produce false-positives.
+See also :ref:`limitations`.
+
+Example with an error:
+
+.. code-block:: python
+
+    class GoodMeta(type):
+        pass
+
+    class BadMeta:
+        pass
+
+    class A1(metaclass=GoodMeta):  # OK
+        pass
+
+    class A2(metaclass=BadMeta):  # Error:  Metaclasses not inheriting from "type" are not supported  [metaclass]
+        pass
+
 .. _code-var-annotated:
 
 Require annotation if variable type is unclear [var-annotated]
diff --git a/docs/source/error_code_list2.rst b/docs/source/error_code_list2.rst
index 784c2ad72819..125671bc2bef 100644
--- a/docs/source/error_code_list2.rst
+++ b/docs/source/error_code_list2.rst
@@ -145,6 +145,29 @@ literal:
     def is_magic(x: bytes) -> bool:
         return x == b'magic'  # OK
 
+:option:`--strict-equality <mypy --strict-equality>` does not include comparisons with
+``None``:
+
+.. code-block:: python
+
+    # mypy: strict-equality
+
+    def is_none(x: str) -> bool:
+        return x is None  # OK
+
+If you want such checks, you must also activate
+:option:`--strict-equality-for-none <mypy --strict-equality-for-none>` (we might merge
+these two options later).
+
+.. code-block:: python
+
+    # mypy: strict-equality strict-equality-for-none
+
+    def is_none(x: str) -> bool:
+        # Error: Non-overlapping identity check
+        #        (left operand type: "str", right operand type: "None")
+        return x is None
+
 .. _code-no-untyped-call:
 
 Check that no untyped functions are called [no-untyped-call]
diff --git a/docs/source/generics.rst b/docs/source/generics.rst
index 5d787d32b005..4755c4f17ec8 100644
--- a/docs/source/generics.rst
+++ b/docs/source/generics.rst
@@ -630,7 +630,7 @@ Let us illustrate this by few simple examples:
 
      my_circles: list[Circle] = []
      add_one(my_circles)     # This may appear safe, but...
-     my_circles[-1].rotate()  # ...this will fail, since my_circles[0] is now a Shape, not a Circle
+     my_circles[0].rotate()  # ...this will fail, since my_circles[0] is now a Shape, not a Circle
 
   Another example of invariant type is ``dict``. Most mutable containers
   are invariant.
diff --git a/docs/source/html_builder.py b/docs/source/html_builder.py
index ea3594e0617b..387f7f13b4c2 100644
--- a/docs/source/html_builder.py
+++ b/docs/source/html_builder.py
@@ -11,16 +11,37 @@
 from sphinx.builders.html import StandaloneHTMLBuilder
 from sphinx.environment import BuildEnvironment
 
+from mypy.main import define_options
+
 
 class MypyHTMLBuilder(StandaloneHTMLBuilder):
+    strict_file: Path
+
     def __init__(self, app: Sphinx, env: BuildEnvironment) -> None:
         super().__init__(app, env)
         self._ref_to_doc = {}
+        self.strict_file = Path(self.srcdir) / "strict_list.rst"
+        self._add_strict_list()
 
     def write_doc(self, docname: str, doctree: document) -> None:
         super().write_doc(docname, doctree)
         self._ref_to_doc.update({_id: docname for _id in doctree.ids})
 
+    def _add_strict_list(self) -> None:
+        strict_flags: list[str]
+        _, strict_flags, _ = define_options()
+        strict_part = ", ".join(f":option:`{s} <mypy {s}>`" for s in strict_flags)
+        if (
+            not strict_part
+            or strict_part.isspace()
+            or len(strict_part) < 20
+            or len(strict_part) > 2000
+        ):
+            raise ValueError(f"{strict_part=}, which doesn't look right (by a simple heuristic).")
+        self.strict_file.write_text(
+            "For this version of mypy, the list of flags enabled by strict is: " + strict_part
+        )
+
     def _verify_error_codes(self) -> None:
         from mypy.errorcodes import error_codes
 
@@ -55,6 +76,7 @@ def _write_ref_redirector(self) -> None:
     def finish(self) -> None:
         super().finish()
         self._write_ref_redirector()
+        self.strict_file.unlink()
 
 
 def setup(app: Sphinx) -> dict[str, Any]:
diff --git a/docs/source/kinds_of_types.rst b/docs/source/kinds_of_types.rst
index 54693cddf953..8e721c0fb321 100644
--- a/docs/source/kinds_of_types.rst
+++ b/docs/source/kinds_of_types.rst
@@ -41,6 +41,11 @@ operations are permitted on the value, and the operations are only checked
 at runtime. You can use ``Any`` as an "escape hatch" when you can't use
 a more precise type for some reason.
 
+This should not be confused with the
+:py:class:`object` type, which represents the set of all values.
+Unlike ``object``, ``Any`` introduces type unsafety — see
+:ref:`any-vs-object` for more.
+
 ``Any`` is compatible with every other type, and vice versa. You can freely
 assign a value of type ``Any`` to a variable with a more precise type:
 
diff --git a/docs/source/metaclasses.rst b/docs/source/metaclasses.rst
index dd77a2f90ed8..e30dfe80f9f9 100644
--- a/docs/source/metaclasses.rst
+++ b/docs/source/metaclasses.rst
@@ -90,3 +90,28 @@ so it's better not to combine metaclasses and class hierarchies:
 * ``Self`` is not allowed as annotation in metaclasses as per `PEP 673`_.
 
 .. _PEP 673: https://peps.python.org/pep-0673/#valid-locations-for-self
+
+For some builtin types, mypy may think their metaclass is :py:class:`abc.ABCMeta`
+even if it is :py:class:`type` at runtime. In those cases, you can either:
+
+* use :py:class:`abc.ABCMeta` instead of :py:class:`type` as the
+  superclass of your metaclass if that works in your use-case
+* mute the error with ``# type: ignore[metaclass]``
+
+.. code-block:: python
+
+    import abc
+
+    assert type(tuple) is type  # metaclass of tuple is type at runtime
+
+    # The problem:
+    class M0(type): pass
+    class A0(tuple, metaclass=M0): pass  # Mypy Error: metaclass conflict
+
+    # Option 1: use ABCMeta instead of type
+    class M1(abc.ABCMeta): pass
+    class A1(tuple, metaclass=M1): pass
+
+    # Option 2: mute the error
+    class M2(type): pass
+    class A2(tuple, metaclass=M2): pass  # type: ignore[metaclass]
diff --git a/docs/source/protocols.rst b/docs/source/protocols.rst
index ed8d94f62ef1..258cd4b0de56 100644
--- a/docs/source/protocols.rst
+++ b/docs/source/protocols.rst
@@ -352,6 +352,53 @@ the parameters are positional-only. Example (using the legacy syntax for generic
    copy_a = copy_b  # OK
    copy_b = copy_a  # Also OK
 
+Binding of types in protocol attributes
+***************************************
+
+All protocol attributes annotations are treated as externally visible types
+of those attributes. This means that for example callables are not bound,
+and descriptors are not invoked:
+
+.. code-block:: python
+
+   from typing import Callable, Protocol, overload
+
+   class Integer:
+       @overload
+       def __get__(self, instance: None, owner: object) -> Integer: ...
+       @overload
+       def __get__(self, instance: object, owner: object) -> int: ...
+       # <some implementation>
+
+   class Example(Protocol):
+       foo: Callable[[object], int]
+       bar: Integer
+
+   ex: Example
+   reveal_type(ex.foo)  # Revealed type is Callable[[object], int]
+   reveal_type(ex.bar)  # Revealed type is Integer
+
+In other words, protocol attribute types are handled as they would appear in a
+``self`` attribute annotation in a regular class. If you want some protocol
+attributes to be handled as though they were defined at class level, you should
+declare them explicitly using ``ClassVar[...]``. Continuing previous example:
+
+.. code-block:: python
+
+   from typing import ClassVar
+
+   class OtherExample(Protocol):
+       # This style is *not recommended*, but may be needed to reuse
+       # some complex callable types. Otherwise use regular methods.
+       foo: ClassVar[Callable[[object], int]]
+       # This may be needed to mimic descriptor access on Type[...] types,
+       # otherwise use a plain "bar: int" style.
+       bar: ClassVar[Integer]
+
+   ex2: OtherExample
+   reveal_type(ex2.foo)  # Revealed type is Callable[[], int]
+   reveal_type(ex2.bar)  # Revealed type is int
+
 .. _predefined_protocols_reference:
 
 Predefined protocol reference
diff --git a/misc/log_trace_check.py b/misc/log_trace_check.py
new file mode 100644
index 000000000000..677c164fe992
--- /dev/null
+++ b/misc/log_trace_check.py
@@ -0,0 +1,85 @@
+"""Compile mypy using mypyc with trace logging enabled, and collect a trace.
+
+The trace log can be used to analyze low-level performance bottlenecks.
+
+By default does a self check as the workload.
+
+This works on all supported platforms, unlike some of our other performance tools.
+"""
+
+from __future__ import annotations
+
+import argparse
+import glob
+import os
+import shutil
+import subprocess
+import sys
+import time
+
+from perf_compare import build_mypy, clone
+
+# Generated files, including binaries, go under this directory to avoid overwriting user state.
+TARGET_DIR = "mypy.log_trace.tmpdir"
+
+
+def perform_type_check(target_dir: str, code: str | None) -> None:
+    cache_dir = os.path.join(target_dir, ".mypy_cache")
+    if os.path.exists(cache_dir):
+        shutil.rmtree(cache_dir)
+    args = []
+    if code is None:
+        args.extend(["--config-file", "mypy_self_check.ini"])
+        for pat in "mypy/*.py", "mypy/*/*.py", "mypyc/*.py", "mypyc/test/*.py":
+            args.extend(glob.glob(pat))
+    else:
+        args.extend(["-c", code])
+    check_cmd = ["python", "-m", "mypy"] + args
+    t0 = time.time()
+    subprocess.run(check_cmd, cwd=target_dir, check=True)
+    elapsed = time.time() - t0
+    print(f"{elapsed:.2f}s elapsed")
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(
+        description="Compile mypy and collect a trace log while type checking (by default, self check)."
+    )
+    parser.add_argument(
+        "--multi-file",
+        action="store_true",
+        help="compile mypy into one C file per module (to reduce RAM use during compilation)",
+    )
+    parser.add_argument(
+        "--skip-compile", action="store_true", help="use compiled mypy from previous run"
+    )
+    parser.add_argument(
+        "-c",
+        metavar="CODE",
+        default=None,
+        type=str,
+        help="type check Python code fragment instead of mypy self-check",
+    )
+    args = parser.parse_args()
+    multi_file: bool = args.multi_file
+    skip_compile: bool = args.skip_compile
+    code: str | None = args.c
+
+    target_dir = TARGET_DIR
+
+    if not skip_compile:
+        clone(target_dir, "HEAD")
+
+        print(f"Building mypy in {target_dir} with trace logging enabled...")
+        build_mypy(target_dir, multi_file, log_trace=True, opt_level="0")
+    elif not os.path.isdir(target_dir):
+        sys.exit("error: Can't find compile mypy from previous run -- can't use --skip-compile")
+
+    perform_type_check(target_dir, code)
+
+    trace_fnam = os.path.join(target_dir, "mypyc_trace.txt")
+    print(f"Generated event trace log in {trace_fnam}")
+
+
+if __name__ == "__main__":
+    main()
diff --git a/misc/perf_compare.py b/misc/perf_compare.py
old mode 100644
new mode 100755
index 025d4065561e..aa05270a8c00
--- a/misc/perf_compare.py
+++ b/misc/perf_compare.py
@@ -1,3 +1,5 @@
+#! /usr/bin/env python
+
 """Compare performance of mypyc-compiled mypy between one or more commits/branches.
 
 Simple usage:
@@ -35,11 +37,24 @@ def heading(s: str) -> None:
     print()
 
 
-def build_mypy(target_dir: str) -> None:
+def build_mypy(
+    target_dir: str,
+    multi_file: bool,
+    *,
+    cflags: str | None = None,
+    log_trace: bool = False,
+    opt_level: str = "2",
+) -> None:
     env = os.environ.copy()
     env["CC"] = "clang"
-    env["MYPYC_OPT_LEVEL"] = "2"
+    env["MYPYC_OPT_LEVEL"] = opt_level
     env["PYTHONHASHSEED"] = "1"
+    if multi_file:
+        env["MYPYC_MULTI_FILE"] = "1"
+    if log_trace:
+        env["MYPYC_LOG_TRACE"] = "1"
+    if cflags is not None:
+        env["CFLAGS"] = cflags
     cmd = [sys.executable, "setup.py", "--use-mypyc", "build_ext", "--inplace"]
     subprocess.run(cmd, env=env, check=True, cwd=target_dir)
 
@@ -110,6 +125,12 @@ def main() -> None:
         action="store_true",
         help="measure incremental run (fully cached)",
     )
+    parser.add_argument(
+        "--multi-file",
+        default=False,
+        action="store_true",
+        help="compile each mypy module to a separate C file (reduces RAM use)",
+    )
     parser.add_argument(
         "--dont-setup",
         default=False,
@@ -127,9 +148,9 @@ def main() -> None:
     parser.add_argument(
         "-j",
         metavar="N",
-        default=8,
+        default=4,
         type=int,
-        help="set maximum number of parallel builds (default=8)",
+        help="set maximum number of parallel builds (default=4) -- high numbers require a lot of RAM!",
     )
     parser.add_argument(
         "-r",
@@ -155,6 +176,7 @@ def main() -> None:
     args = parser.parse_args()
     incremental: bool = args.incremental
     dont_setup: bool = args.dont_setup
+    multi_file: bool = args.multi_file
     commits = args.commit
     num_runs: int = args.num_runs + 1
     max_workers: int = args.j
@@ -185,7 +207,9 @@ def main() -> None:
         print("(This will take a while...)")
 
         with ThreadPoolExecutor(max_workers=max_workers) as executor:
-            futures = [executor.submit(build_mypy, target_dir) for target_dir in target_dirs]
+            futures = [
+                executor.submit(build_mypy, target_dir, multi_file) for target_dir in target_dirs
+            ]
             for future in as_completed(futures):
                 future.result()
 
diff --git a/misc/profile_check.py b/misc/profile_check.py
new file mode 100644
index 000000000000..b29535020f0a
--- /dev/null
+++ b/misc/profile_check.py
@@ -0,0 +1,145 @@
+"""Compile mypy using mypyc and profile type checking using perf.
+
+By default does a self check.
+
+Notes:
+ - Only Linux is supported for now (TODO: add support for other profilers)
+ - The profile is collected at C level
+   - It includes C functions compiled by mypyc and CPython runtime functions
+ - The names of mypy functions are mangled to C names, but usually it's clear what they mean
+   - Generally CPyDef_ prefix for native functions and CPyPy_ prefix for wrapper functions
+ - It's important to compile CPython using special flags (see below) to get good results
+ - Generally use the latest Python feature release (or the most recent beta if supported by mypyc)
+ - The tool prints a command that can be used to analyze the profile afterwards
+
+You may need to adjust kernel parameters temporarily, e.g. this (note that this has security
+implications):
+
+  sudo sysctl kernel.perf_event_paranoid=-1
+
+This is the recommended way to configure CPython for profiling:
+
+  ./configure \
+      --enable-optimizations \
+      --with-lto \
+      CFLAGS="-O2 -g -fno-omit-frame-pointer"
+"""
+
+from __future__ import annotations
+
+import argparse
+import glob
+import os
+import shutil
+import subprocess
+import sys
+import time
+
+from perf_compare import build_mypy, clone
+
+# Use these C compiler flags when compiling mypy (important). Note that it's strongly recommended
+# to also compile CPython using similar flags, but we don't enforce it in this script.
+CFLAGS = "-O2 -fno-omit-frame-pointer -g"
+
+# Generated files, including binaries, go under this directory to avoid overwriting user state.
+TARGET_DIR = "mypy.profile.tmpdir"
+
+
+def _profile_type_check(target_dir: str, code: str | None) -> None:
+    cache_dir = os.path.join(target_dir, ".mypy_cache")
+    if os.path.exists(cache_dir):
+        shutil.rmtree(cache_dir)
+    args = []
+    if code is None:
+        args.extend(["--config-file", "mypy_self_check.ini"])
+        for pat in "mypy/*.py", "mypy/*/*.py", "mypyc/*.py", "mypyc/test/*.py":
+            args.extend(glob.glob(pat))
+    else:
+        args.extend(["-c", code])
+    check_cmd = ["python", "-m", "mypy"] + args
+    cmdline = ["perf", "record", "-g"] + check_cmd
+    t0 = time.time()
+    subprocess.run(cmdline, cwd=target_dir, check=True)
+    elapsed = time.time() - t0
+    print(f"{elapsed:.2f}s elapsed")
+
+
+def profile_type_check(target_dir: str, code: str | None) -> None:
+    try:
+        _profile_type_check(target_dir, code)
+    except subprocess.CalledProcessError:
+        print("\nProfiling failed! You may missing some permissions.")
+        print("\nThis may help (note that it has security implications):")
+        print("  sudo sysctl kernel.perf_event_paranoid=-1")
+        sys.exit(1)
+
+
+def check_requirements() -> None:
+    if sys.platform != "linux":
+        # TODO: How to make this work on other platforms?
+        sys.exit("error: Only Linux is supported")
+
+    try:
+        subprocess.run(["perf", "-h"], capture_output=True)
+    except (subprocess.CalledProcessError, FileNotFoundError):
+        print("error: The 'perf' profiler is not installed")
+        sys.exit(1)
+
+    try:
+        subprocess.run(["clang", "--version"], capture_output=True)
+    except (subprocess.CalledProcessError, FileNotFoundError):
+        print("error: The clang compiler is not installed")
+        sys.exit(1)
+
+    if not os.path.isfile("mypy_self_check.ini"):
+        print("error: Run this in the mypy repository root")
+        sys.exit(1)
+
+
+def main() -> None:
+    check_requirements()
+
+    parser = argparse.ArgumentParser(
+        description="Compile mypy and profile type checking using 'perf' (by default, self check)."
+    )
+    parser.add_argument(
+        "--multi-file",
+        action="store_true",
+        help="compile mypy into one C file per module (to reduce RAM use during compilation)",
+    )
+    parser.add_argument(
+        "--skip-compile", action="store_true", help="use compiled mypy from previous run"
+    )
+    parser.add_argument(
+        "-c",
+        metavar="CODE",
+        default=None,
+        type=str,
+        help="profile type checking Python code fragment instead of mypy self-check",
+    )
+    args = parser.parse_args()
+    multi_file: bool = args.multi_file
+    skip_compile: bool = args.skip_compile
+    code: str | None = args.c
+
+    target_dir = TARGET_DIR
+
+    if not skip_compile:
+        clone(target_dir, "HEAD")
+
+        print(f"Building mypy in {target_dir}...")
+        build_mypy(target_dir, multi_file, cflags=CFLAGS)
+    elif not os.path.isdir(target_dir):
+        sys.exit("error: Can't find compile mypy from previous run -- can't use --skip-compile")
+
+    profile_type_check(target_dir, code)
+
+    print()
+    print('NOTE: Compile CPython using CFLAGS="-O2 -g -fno-omit-frame-pointer" for good results')
+    print()
+    print("CPU profile collected. You can now analyze the profile:")
+    print(f"  perf report -i {target_dir}/perf.data ")
+
+
+if __name__ == "__main__":
+    main()
diff --git a/misc/typeshed_patches/0001-Partially-revert-Clean-up-argparse-hacks.patch b/misc/typeshed_patches/0001-Partially-revert-Clean-up-argparse-hacks.patch
index f76818d10cba..5c31569711e5 100644
--- a/misc/typeshed_patches/0001-Partially-revert-Clean-up-argparse-hacks.patch
+++ b/misc/typeshed_patches/0001-Partially-revert-Clean-up-argparse-hacks.patch
@@ -1,4 +1,4 @@
-From 05f351f6a37fe8b73c698c348bf6aa5108363049 Mon Sep 17 00:00:00 2001
+From 84a9d586544a0408d4654f57f83a93cb048070fb Mon Sep 17 00:00:00 2001
 From: Marc Mueller <30130371+cdce8p@users.noreply.github.com>
 Date: Sat, 15 Feb 2025 20:11:06 +0100
 Subject: [PATCH] Partially revert Clean up argparse hacks
@@ -8,15 +8,15 @@ Subject: [PATCH] Partially revert Clean up argparse hacks
  1 file changed, 5 insertions(+), 3 deletions(-)
 
 diff --git a/mypy/typeshed/stdlib/argparse.pyi b/mypy/typeshed/stdlib/argparse.pyi
-index 95ad6c7da..79e6cfde1 100644
+index b9fa31139..3c3ba116a 100644
 --- a/mypy/typeshed/stdlib/argparse.pyi
 +++ b/mypy/typeshed/stdlib/argparse.pyi
 @@ -2,7 +2,7 @@ import sys
  from _typeshed import SupportsWrite, sentinel
  from collections.abc import Callable, Generator, Iterable, Sequence
  from re import Pattern
--from typing import IO, Any, ClassVar, Final, Generic, NoReturn, Protocol, TypeVar, overload
-+from typing import IO, Any, ClassVar, Final, Generic, NewType, NoReturn, Protocol, TypeVar, overload
+-from typing import IO, Any, ClassVar, Final, Generic, NoReturn, Protocol, TypeVar, overload, type_check_only
++from typing import IO, Any, ClassVar, Final, Generic, NewType, NoReturn, Protocol, TypeVar, overload, type_check_only
  from typing_extensions import Self, TypeAlias, deprecated
  
  __all__ = [
@@ -41,5 +41,5 @@ index 95ad6c7da..79e6cfde1 100644
          default: Any = ...,
          type: _ActionType = ...,
 -- 
-2.49.0
+2.50.1
 
diff --git a/misc/typeshed_patches/0001-Remove-use-of-LiteralString-in-builtins-13743.patch b/misc/typeshed_patches/0001-Remove-use-of-LiteralString-in-builtins-13743.patch
index 9d0cb5271e7d..a47d5db3cd22 100644
--- a/misc/typeshed_patches/0001-Remove-use-of-LiteralString-in-builtins-13743.patch
+++ b/misc/typeshed_patches/0001-Remove-use-of-LiteralString-in-builtins-13743.patch
@@ -1,4 +1,4 @@
-From e6995c91231e1915eba43a29a22dd4cbfaf9e08e Mon Sep 17 00:00:00 2001
+From 805d7fc06a8bee350959512e0908a18a87b7f8c2 Mon Sep 17 00:00:00 2001
 From: Shantanu <12621235+hauntsaninja@users.noreply.github.com>
 Date: Mon, 26 Sep 2022 12:55:07 -0700
 Subject: [PATCH] Remove use of LiteralString in builtins (#13743)
@@ -8,7 +8,7 @@ Subject: [PATCH] Remove use of LiteralString in builtins (#13743)
  1 file changed, 1 insertion(+), 99 deletions(-)
 
 diff --git a/mypy/typeshed/stdlib/builtins.pyi b/mypy/typeshed/stdlib/builtins.pyi
-index 00728f42d..ea77a730f 100644
+index c7ab95482..3e93da36e 100644
 --- a/mypy/typeshed/stdlib/builtins.pyi
 +++ b/mypy/typeshed/stdlib/builtins.pyi
 @@ -63,7 +63,6 @@ from typing import (  # noqa: Y022,UP035
@@ -19,7 +19,7 @@ index 00728f42d..ea77a730f 100644
      ParamSpec,
      Self,
      TypeAlias,
-@@ -453,31 +452,16 @@ class str(Sequence[str]):
+@@ -468,31 +467,16 @@ class str(Sequence[str]):
      def __new__(cls, object: object = ...) -> Self: ...
      @overload
      def __new__(cls, object: ReadableBuffer, encoding: str = ..., errors: str = ...) -> Self: ...
@@ -51,7 +51,7 @@ index 00728f42d..ea77a730f 100644
      def format(self, *args: object, **kwargs: object) -> str: ...
      def format_map(self, mapping: _FormatMapMapping, /) -> str: ...
      def index(self, sub: str, start: SupportsIndex | None = ..., end: SupportsIndex | None = ..., /) -> int: ...
-@@ -493,98 +477,34 @@ class str(Sequence[str]):
+@@ -508,98 +492,34 @@ class str(Sequence[str]):
      def isspace(self) -> bool: ...
      def istitle(self) -> bool: ...
      def isupper(self) -> bool: ...
@@ -150,7 +150,7 @@ index 00728f42d..ea77a730f 100644
      def zfill(self, width: SupportsIndex, /) -> str: ...  # type: ignore[misc]
      @staticmethod
      @overload
-@@ -595,39 +515,21 @@ class str(Sequence[str]):
+@@ -610,39 +530,21 @@ class str(Sequence[str]):
      @staticmethod
      @overload
      def maketrans(x: str, y: str, z: str, /) -> dict[int, int | None]: ...
@@ -190,7 +190,7 @@ index 00728f42d..ea77a730f 100644
 -    @overload
      def __rmul__(self, value: SupportsIndex, /) -> str: ...  # type: ignore[misc]
      def __getnewargs__(self) -> tuple[str]: ...
- 
+     def __format__(self, format_spec: str, /) -> str: ...
 -- 
-2.49.0
+2.50.1
 
diff --git a/misc/typeshed_patches/0001-Revert-Remove-redundant-inheritances-from-Iterator.patch b/misc/typeshed_patches/0001-Revert-Remove-redundant-inheritances-from-Iterator.patch
index 5b30a63f1318..fdcc14cec3c6 100644
--- a/misc/typeshed_patches/0001-Revert-Remove-redundant-inheritances-from-Iterator.patch
+++ b/misc/typeshed_patches/0001-Revert-Remove-redundant-inheritances-from-Iterator.patch
@@ -1,4 +1,4 @@
-From 363d69b366695fea117631d30c348e36b9a5a99d Mon Sep 17 00:00:00 2001
+From 438dbb1300b77331940d7db8f010e97305745116 Mon Sep 17 00:00:00 2001
 From: Marc Mueller <30130371+cdce8p@users.noreply.github.com>
 Date: Sat, 21 Dec 2024 22:36:38 +0100
 Subject: [PATCH] Revert Remove redundant inheritances from Iterator in
@@ -15,7 +15,7 @@ Subject: [PATCH] Revert Remove redundant inheritances from Iterator in
  7 files changed, 34 insertions(+), 34 deletions(-)
 
 diff --git a/mypy/typeshed/stdlib/_asyncio.pyi b/mypy/typeshed/stdlib/_asyncio.pyi
-index 4544680cc..19a2d12d8 100644
+index d663f5d93..f43178e4d 100644
 --- a/mypy/typeshed/stdlib/_asyncio.pyi
 +++ b/mypy/typeshed/stdlib/_asyncio.pyi
 @@ -1,6 +1,6 @@
@@ -26,59 +26,59 @@ index 4544680cc..19a2d12d8 100644
  from contextvars import Context
  from types import FrameType, GenericAlias
  from typing import Any, Literal, TextIO, TypeVar
-@@ -10,7 +10,7 @@ _T = TypeVar("_T")
- _T_co = TypeVar("_T_co", covariant=True)
+@@ -11,7 +11,7 @@ _T_co = TypeVar("_T_co", covariant=True)
  _TaskYieldType: TypeAlias = Future[object] | None
  
+ @disjoint_base
 -class Future(Awaitable[_T]):
 +class Future(Awaitable[_T], Iterable[_T]):
      _state: str
      @property
      def _exception(self) -> BaseException | None: ...
 diff --git a/mypy/typeshed/stdlib/builtins.pyi b/mypy/typeshed/stdlib/builtins.pyi
-index ea77a730f..900c4c93f 100644
+index f2dd00079..784ee7eac 100644
 --- a/mypy/typeshed/stdlib/builtins.pyi
 +++ b/mypy/typeshed/stdlib/builtins.pyi
-@@ -1170,7 +1170,7 @@ class frozenset(AbstractSet[_T_co]):
-     def __hash__(self) -> int: ...
+@@ -1209,7 +1209,7 @@ class frozenset(AbstractSet[_T_co]):
      def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
  
+ @disjoint_base
 -class enumerate(Generic[_T]):
 +class enumerate(Iterator[tuple[int, _T]]):
      def __new__(cls, iterable: Iterable[_T], start: int = 0) -> Self: ...
      def __iter__(self) -> Self: ...
      def __next__(self) -> tuple[int, _T]: ...
-@@ -1366,7 +1366,7 @@ else:
- 
+@@ -1405,7 +1405,7 @@ else:
  exit: _sitebuiltins.Quitter
  
+ @disjoint_base
 -class filter(Generic[_T]):
 +class filter(Iterator[_T]):
      @overload
      def __new__(cls, function: None, iterable: Iterable[_T | None], /) -> Self: ...
      @overload
-@@ -1431,7 +1431,7 @@ license: _sitebuiltins._Printer
+@@ -1469,7 +1469,7 @@ license: _sitebuiltins._Printer
  
  def locals() -> dict[str, Any]: ...
- 
+ @disjoint_base
 -class map(Generic[_S]):
 +class map(Iterator[_S]):
      # 3.14 adds `strict` argument.
      if sys.version_info >= (3, 14):
          @overload
-@@ -1734,7 +1734,7 @@ def pow(base: _SupportsSomeKindOfPow, exp: complex, mod: None = None) -> complex
- 
+@@ -1776,7 +1776,7 @@ def pow(base: _SupportsSomeKindOfPow, exp: complex, mod: None = None) -> complex
  quit: _sitebuiltins.Quitter
  
+ @disjoint_base
 -class reversed(Generic[_T]):
 +class reversed(Iterator[_T]):
      @overload
      def __new__(cls, sequence: Reversible[_T], /) -> Iterator[_T]: ...  # type: ignore[misc]
      @overload
-@@ -1795,7 +1795,7 @@ def vars(object: type, /) -> types.MappingProxyType[str, Any]: ...
+@@ -1840,7 +1840,7 @@ def vars(object: type, /) -> types.MappingProxyType[str, Any]: ...
  @overload
  def vars(object: Any = ..., /) -> dict[str, Any]: ...
- 
+ @disjoint_base
 -class zip(Generic[_T_co]):
 +class zip(Iterator[_T_co]):
      if sys.version_info >= (3, 10):
@@ -107,7 +107,7 @@ index 2c8e7109c..4ed0ab1d8 100644
      restkey: _T | None
      restval: str | Any | None
 diff --git a/mypy/typeshed/stdlib/fileinput.pyi b/mypy/typeshed/stdlib/fileinput.pyi
-index 948b39ea1..1d5f9cf00 100644
+index 910d63814..eb942bc55 100644
 --- a/mypy/typeshed/stdlib/fileinput.pyi
 +++ b/mypy/typeshed/stdlib/fileinput.pyi
 @@ -1,8 +1,8 @@
@@ -116,12 +116,12 @@ index 948b39ea1..1d5f9cf00 100644
 -from collections.abc import Callable, Iterable
 +from collections.abc import Callable, Iterable, Iterator
  from types import GenericAlias, TracebackType
--from typing import IO, Any, AnyStr, Generic, Literal, Protocol, overload
-+from typing import IO, Any, AnyStr, Literal, Protocol, overload
+-from typing import IO, Any, AnyStr, Generic, Literal, Protocol, overload, type_check_only
++from typing import IO, Any, AnyStr, Literal, Protocol, overload, type_check_only
  from typing_extensions import Self, TypeAlias
  
  __all__ = [
-@@ -104,7 +104,7 @@ def fileno() -> int: ...
+@@ -105,7 +105,7 @@ def fileno() -> int: ...
  def isfirstline() -> bool: ...
  def isstdin() -> bool: ...
  
@@ -131,97 +131,102 @@ index 948b39ea1..1d5f9cf00 100644
          # encoding and errors are added
          @overload
 diff --git a/mypy/typeshed/stdlib/itertools.pyi b/mypy/typeshed/stdlib/itertools.pyi
-index d0085dd72..7d05b1318 100644
+index fe4ccbdf8..73745fe92 100644
 --- a/mypy/typeshed/stdlib/itertools.pyi
 +++ b/mypy/typeshed/stdlib/itertools.pyi
-@@ -27,7 +27,7 @@ _Predicate: TypeAlias = Callable[[_T], object]
- 
+@@ -28,7 +28,7 @@ _Predicate: TypeAlias = Callable[[_T], object]
  # Technically count can take anything that implements a number protocol and has an add method
  # but we can't enforce the add method
+ @disjoint_base
 -class count(Generic[_N]):
 +class count(Iterator[_N]):
      @overload
      def __new__(cls) -> count[int]: ...
      @overload
-@@ -37,12 +37,12 @@ class count(Generic[_N]):
-     def __next__(self) -> _N: ...
+@@ -39,13 +39,13 @@ class count(Generic[_N]):
      def __iter__(self) -> Self: ...
  
+ @disjoint_base
 -class cycle(Generic[_T]):
 +class cycle(Iterator[_T]):
      def __new__(cls, iterable: Iterable[_T], /) -> Self: ...
      def __next__(self) -> _T: ...
      def __iter__(self) -> Self: ...
  
+ @disjoint_base
 -class repeat(Generic[_T]):
 +class repeat(Iterator[_T]):
      @overload
      def __new__(cls, object: _T) -> Self: ...
      @overload
-@@ -51,7 +51,7 @@ class repeat(Generic[_T]):
-     def __iter__(self) -> Self: ...
+@@ -55,7 +55,7 @@ class repeat(Generic[_T]):
      def __length_hint__(self) -> int: ...
  
+ @disjoint_base
 -class accumulate(Generic[_T]):
 +class accumulate(Iterator[_T]):
      @overload
      def __new__(cls, iterable: Iterable[_T], func: None = None, *, initial: _T | None = ...) -> Self: ...
      @overload
-@@ -59,7 +59,7 @@ class accumulate(Generic[_T]):
-     def __iter__(self) -> Self: ...
+@@ -64,7 +64,7 @@ class accumulate(Generic[_T]):
      def __next__(self) -> _T: ...
  
+ @disjoint_base
 -class chain(Generic[_T]):
 +class chain(Iterator[_T]):
      def __new__(cls, *iterables: Iterable[_T]) -> Self: ...
      def __next__(self) -> _T: ...
      def __iter__(self) -> Self: ...
-@@ -68,22 +68,22 @@ class chain(Generic[_T]):
-     def from_iterable(cls: type[Any], iterable: Iterable[Iterable[_S]], /) -> chain[_S]: ...
+@@ -74,25 +74,25 @@ class chain(Generic[_T]):
      def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
  
+ @disjoint_base
 -class compress(Generic[_T]):
 +class compress(Iterator[_T]):
      def __new__(cls, data: Iterable[_T], selectors: Iterable[Any]) -> Self: ...
      def __iter__(self) -> Self: ...
      def __next__(self) -> _T: ...
  
+ @disjoint_base
 -class dropwhile(Generic[_T]):
 +class dropwhile(Iterator[_T]):
      def __new__(cls, predicate: _Predicate[_T], iterable: Iterable[_T], /) -> Self: ...
      def __iter__(self) -> Self: ...
      def __next__(self) -> _T: ...
  
+ @disjoint_base
 -class filterfalse(Generic[_T]):
 +class filterfalse(Iterator[_T]):
      def __new__(cls, function: _Predicate[_T] | None, iterable: Iterable[_T], /) -> Self: ...
      def __iter__(self) -> Self: ...
      def __next__(self) -> _T: ...
  
+ @disjoint_base
 -class groupby(Generic[_T_co, _S_co]):
 +class groupby(Iterator[tuple[_T_co, Iterator[_S_co]]], Generic[_T_co, _S_co]):
      @overload
      def __new__(cls, iterable: Iterable[_T1], key: None = None) -> groupby[_T1, _T1]: ...
      @overload
-@@ -91,7 +91,7 @@ class groupby(Generic[_T_co, _S_co]):
-     def __iter__(self) -> Self: ...
+@@ -101,7 +101,7 @@ class groupby(Generic[_T_co, _S_co]):
      def __next__(self) -> tuple[_T_co, Iterator[_S_co]]: ...
  
+ @disjoint_base
 -class islice(Generic[_T]):
 +class islice(Iterator[_T]):
      @overload
      def __new__(cls, iterable: Iterable[_T], stop: int | None, /) -> Self: ...
      @overload
-@@ -99,19 +99,19 @@ class islice(Generic[_T]):
-     def __iter__(self) -> Self: ...
+@@ -110,20 +110,20 @@ class islice(Generic[_T]):
      def __next__(self) -> _T: ...
  
+ @disjoint_base
 -class starmap(Generic[_T_co]):
 +class starmap(Iterator[_T_co]):
      def __new__(cls, function: Callable[..., _T], iterable: Iterable[Iterable[Any]], /) -> starmap[_T]: ...
      def __iter__(self) -> Self: ...
      def __next__(self) -> _T_co: ...
  
+ @disjoint_base
 -class takewhile(Generic[_T]):
 +class takewhile(Iterator[_T]):
      def __new__(cls, predicate: _Predicate[_T], iterable: Iterable[_T], /) -> Self: ...
@@ -229,52 +234,52 @@ index d0085dd72..7d05b1318 100644
      def __next__(self) -> _T: ...
  
  def tee(iterable: Iterable[_T], n: int = 2, /) -> tuple[Iterator[_T], ...]: ...
- 
+ @disjoint_base
 -class zip_longest(Generic[_T_co]):
 +class zip_longest(Iterator[_T_co]):
      # one iterable (fillvalue doesn't matter)
      @overload
      def __new__(cls, iter1: Iterable[_T1], /, *, fillvalue: object = ...) -> zip_longest[tuple[_T1]]: ...
-@@ -189,7 +189,7 @@ class zip_longest(Generic[_T_co]):
-     def __iter__(self) -> Self: ...
+@@ -202,7 +202,7 @@ class zip_longest(Generic[_T_co]):
      def __next__(self) -> _T_co: ...
  
+ @disjoint_base
 -class product(Generic[_T_co]):
 +class product(Iterator[_T_co]):
      @overload
      def __new__(cls, iter1: Iterable[_T1], /) -> product[tuple[_T1]]: ...
      @overload
-@@ -274,7 +274,7 @@ class product(Generic[_T_co]):
-     def __iter__(self) -> Self: ...
+@@ -288,7 +288,7 @@ class product(Generic[_T_co]):
      def __next__(self) -> _T_co: ...
  
+ @disjoint_base
 -class permutations(Generic[_T_co]):
 +class permutations(Iterator[_T_co]):
      @overload
      def __new__(cls, iterable: Iterable[_T], r: Literal[2]) -> permutations[tuple[_T, _T]]: ...
      @overload
-@@ -288,7 +288,7 @@ class permutations(Generic[_T_co]):
-     def __iter__(self) -> Self: ...
+@@ -303,7 +303,7 @@ class permutations(Generic[_T_co]):
      def __next__(self) -> _T_co: ...
  
+ @disjoint_base
 -class combinations(Generic[_T_co]):
 +class combinations(Iterator[_T_co]):
      @overload
      def __new__(cls, iterable: Iterable[_T], r: Literal[2]) -> combinations[tuple[_T, _T]]: ...
      @overload
-@@ -302,7 +302,7 @@ class combinations(Generic[_T_co]):
-     def __iter__(self) -> Self: ...
+@@ -318,7 +318,7 @@ class combinations(Generic[_T_co]):
      def __next__(self) -> _T_co: ...
  
+ @disjoint_base
 -class combinations_with_replacement(Generic[_T_co]):
 +class combinations_with_replacement(Iterator[_T_co]):
      @overload
      def __new__(cls, iterable: Iterable[_T], r: Literal[2]) -> combinations_with_replacement[tuple[_T, _T]]: ...
      @overload
-@@ -317,13 +317,13 @@ class combinations_with_replacement(Generic[_T_co]):
-     def __next__(self) -> _T_co: ...
+@@ -334,14 +334,14 @@ class combinations_with_replacement(Generic[_T_co]):
  
  if sys.version_info >= (3, 10):
+     @disjoint_base
 -    class pairwise(Generic[_T_co]):
 +    class pairwise(Iterator[_T_co]):
          def __new__(cls, iterable: Iterable[_T], /) -> pairwise[tuple[_T, _T]]: ...
@@ -282,6 +287,7 @@ index d0085dd72..7d05b1318 100644
          def __next__(self) -> _T_co: ...
  
  if sys.version_info >= (3, 12):
+     @disjoint_base
 -    class batched(Generic[_T_co]):
 +    class batched(Iterator[tuple[_T_co, ...]], Generic[_T_co]):
          if sys.version_info >= (3, 13):
@@ -307,18 +313,18 @@ index b79f9e773..f276372d0 100644
      def __iter__(self) -> Self: ...
      def next(self, timeout: float | None = None) -> _T: ...
 diff --git a/mypy/typeshed/stdlib/sqlite3/__init__.pyi b/mypy/typeshed/stdlib/sqlite3/__init__.pyi
-index 5d3c2330b..ab783dbde 100644
+index 6b0f1ba94..882cd143c 100644
 --- a/mypy/typeshed/stdlib/sqlite3/__init__.pyi
 +++ b/mypy/typeshed/stdlib/sqlite3/__init__.pyi
-@@ -399,7 +399,7 @@ class Connection:
-         self, type: type[BaseException] | None, value: BaseException | None, traceback: TracebackType | None, /
+@@ -407,7 +407,7 @@ class Connection:
      ) -> Literal[False]: ...
  
+ @disjoint_base
 -class Cursor:
 +class Cursor(Iterator[Any]):
      arraysize: int
      @property
      def connection(self) -> Connection: ...
 -- 
-2.49.0
+2.51.0
 
diff --git a/misc/update-stubinfo.py b/misc/update-stubinfo.py
index beaed34a8a47..4a5b9a40c408 100644
--- a/misc/update-stubinfo.py
+++ b/misc/update-stubinfo.py
@@ -58,7 +58,7 @@ def main() -> None:
     print("Consider removing the following packages no longer in typeshed:")
     print("=" * 40)
     for p in sorted(mypy_p - typeshed_p_to_d.keys()):
-        if p in {"lxml", "pandas"}:  # never in typeshed
+        if p in {"lxml", "pandas", "scipy"}:  # never in typeshed
             continue
         print(p)
 
diff --git a/misc/upload-pypi.py b/misc/upload-pypi.py
index c9db475c14b4..8ea86bbea584 100644
--- a/misc/upload-pypi.py
+++ b/misc/upload-pypi.py
@@ -108,7 +108,7 @@ def tmp_twine() -> Iterator[Path]:
 def upload_dist(dist: Path, dry_run: bool = True) -> None:
     with tmp_twine() as twine:
         files = [item for item in dist.iterdir() if item_ok_for_pypi(item.name)]
-        cmd: list[Any] = [twine, "upload"]
+        cmd: list[Any] = [twine, "upload", "--skip-existing"]
         cmd += files
         if dry_run:
             print("[dry run] " + " ".join(map(str, cmd)))
diff --git a/mypy/applytype.py b/mypy/applytype.py
index e87bf939c81a..dfeaf7752d21 100644
--- a/mypy/applytype.py
+++ b/mypy/applytype.py
@@ -243,7 +243,7 @@ def visit_callable_type(self, t: CallableType) -> Type:
         self.bound_tvars -= set(found_vars)
 
         assert isinstance(result, ProperType) and isinstance(result, CallableType)
-        result.variables = list(result.variables) + found_vars
+        result.variables = result.variables + tuple(found_vars)
         return result
 
     def visit_type_var(self, t: TypeVarType) -> Type:
diff --git a/mypy/argmap.py b/mypy/argmap.py
index 28fad1f093dd..a3e8f7fc8c2e 100644
--- a/mypy/argmap.py
+++ b/mypy/argmap.py
@@ -167,7 +167,7 @@ def __init__(self, context: ArgumentInferContext) -> None:
         # Next tuple *args index to use.
         self.tuple_index = 0
         # Keyword arguments in TypedDict **kwargs used.
-        self.kwargs_used: set[str] = set()
+        self.kwargs_used: set[str] | None = None
         # Type context for `*` and `**` arg kinds.
         self.context = context
 
@@ -241,6 +241,8 @@ def expand_actual_type(
             from mypy.subtypes import is_subtype
 
             if isinstance(actual_type, TypedDictType):
+                if self.kwargs_used is None:
+                    self.kwargs_used = set()
                 if formal_kind != nodes.ARG_STAR2 and formal_name in actual_type.items:
                     # Lookup type based on keyword argument name.
                     assert formal_name is not None
diff --git a/mypy/binder.py b/mypy/binder.py
index d3482d1dad4f..a83e65276ff4 100644
--- a/mypy/binder.py
+++ b/mypy/binder.py
@@ -8,7 +8,16 @@
 
 from mypy.erasetype import remove_instance_last_known_values
 from mypy.literals import Key, extract_var_from_literal_hash, literal, literal_hash, subkeys
-from mypy.nodes import Expression, IndexExpr, MemberExpr, NameExpr, RefExpr, TypeInfo, Var
+from mypy.nodes import (
+    LITERAL_NO,
+    Expression,
+    IndexExpr,
+    MemberExpr,
+    NameExpr,
+    RefExpr,
+    TypeInfo,
+    Var,
+)
 from mypy.options import Options
 from mypy.subtypes import is_same_type, is_subtype
 from mypy.typeops import make_simplified_union
@@ -138,6 +147,10 @@ def __init__(self, options: Options) -> None:
         # flexible inference of variable types (--allow-redefinition-new).
         self.bind_all = options.allow_redefinition_new
 
+        # This tracks any externally visible changes in binder to invalidate
+        # expression caches when needed.
+        self.version = 0
+
     def _get_id(self) -> int:
         self.next_id += 1
         return self.next_id
@@ -158,6 +171,7 @@ def push_frame(self, conditional_frame: bool = False) -> Frame:
         return f
 
     def _put(self, key: Key, type: Type, from_assignment: bool, index: int = -1) -> None:
+        self.version += 1
         self.frames[index].types[key] = CurrentType(type, from_assignment)
 
     def _get(self, key: Key, index: int = -1) -> CurrentType | None:
@@ -168,6 +182,15 @@ def _get(self, key: Key, index: int = -1) -> CurrentType | None:
                 return self.frames[i].types[key]
         return None
 
+    @classmethod
+    def can_put_directly(cls, expr: Expression) -> bool:
+        """Will `.put()` on this expression be successful?
+
+        This is inlined in `.put()` because the logic is rather hot and must be kept
+        in sync.
+        """
+        return isinstance(expr, (IndexExpr, MemberExpr, NameExpr)) and literal(expr) > LITERAL_NO
+
     def put(self, expr: Expression, typ: Type, *, from_assignment: bool = True) -> None:
         """Directly set the narrowed type of expression (if it supports it).
 
@@ -185,6 +208,7 @@ def put(self, expr: Expression, typ: Type, *, from_assignment: bool = True) -> N
         self._put(key, typ, from_assignment)
 
     def unreachable(self) -> None:
+        self.version += 1
         self.frames[-1].unreachable = True
 
     def suppress_unreachable_warnings(self) -> None:
@@ -226,10 +250,12 @@ def update_from_options(self, frames: list[Frame]) -> bool:
         options are the same.
         """
         all_reachable = all(not f.unreachable for f in frames)
-        frames = [f for f in frames if not f.unreachable]
+        if not all_reachable:
+            frames = [f for f in frames if not f.unreachable]
         changed = False
-        keys = {key for f in frames for key in f.types}
-
+        keys = [key for f in frames for key in f.types]
+        if len(keys) > 1:
+            keys = list(set(keys))
         for key in keys:
             current_value = self._get(key)
             resulting_values = [f.types.get(key, current_value) for f in frames]
diff --git a/mypy/build.py b/mypy/build.py
index 355ba861385e..39199b39b6ad 100644
--- a/mypy/build.py
+++ b/mypy/build.py
@@ -40,6 +40,7 @@
 from typing_extensions import TypeAlias as _TypeAlias
 
 import mypy.semanal_main
+from mypy.cache import Buffer
 from mypy.checker import TypeChecker
 from mypy.error_formatter import OUTPUT_CHOICES, ErrorFormatter
 from mypy.errors import CompileError, ErrorInfo, Errors, report_internal_error
@@ -116,6 +117,8 @@
     "abc",
 }
 
+# We are careful now, we can increase this in future if safe/useful.
+MAX_GC_FREEZE_CYCLES = 1
 
 Graph: _TypeAlias = dict[str, "State"]
 
@@ -194,7 +197,7 @@ def default_flush_errors(
         result.errors = messages
         return result
     except CompileError as e:
-        # CompileErrors raised from an errors object carry all of the
+        # CompileErrors raised from an errors object carry all the
         # messages that have not been reported out by error streaming.
         # Patch it up to contain either none or all none of the messages,
         # depending on whether we are flushing errors.
@@ -707,6 +710,8 @@ def __init__(
         # new file can be processed O(n**2) times. This cache
         # avoids most of this redundant work.
         self.ast_cache: dict[str, tuple[MypyFile, list[ErrorInfo]]] = {}
+        # Number of times we used GC optimization hack for fresh SCCs.
+        self.gc_freeze_cycles = 0
 
     def dump_stats(self) -> None:
         if self.options.dump_build_stats:
@@ -802,11 +807,11 @@ def correct_rel_imp(imp: ImportFrom | ImportAll) -> str:
                             res.append((pri, sub_id, imp.line))
                         else:
                             all_are_submodules = False
-                    # Add cur_id as a dependency, even if all of the
+                    # Add cur_id as a dependency, even if all the
                     # imports are submodules. Processing import from will try
                     # to look through cur_id, so we should depend on it.
-                    # As a workaround for for some bugs in cycle handling (#4498),
-                    # if all of the imports are submodules, do the import at a lower
+                    # As a workaround for some bugs in cycle handling (#4498),
+                    # if all the imports are submodules, do the import at a lower
                     # priority.
                     pri = import_priority(imp, PRI_HIGH if not all_are_submodules else PRI_LOW)
                     res.append((pri, cur_id, imp.line))
@@ -929,7 +934,7 @@ def write_deps_cache(
 ) -> None:
     """Write cache files for fine-grained dependencies.
 
-    Serialize fine-grained dependencies map for fine grained mode.
+    Serialize fine-grained dependencies map for fine-grained mode.
 
     Dependencies on some module 'm' is stored in the dependency cache
     file m.deps.json.  This entails some spooky action at a distance:
@@ -943,7 +948,7 @@ def write_deps_cache(
     fine-grained dependencies in a global cache file:
      * We take a snapshot of current sources to later check consistency
        between the fine-grained dependency cache and module cache metadata
-     * We store the mtime of all of the dependency files to verify they
+     * We store the mtime of all the dependency files to verify they
        haven't changed
     """
     metastore = manager.metastore
@@ -1111,7 +1116,7 @@ def read_deps_cache(manager: BuildManager, graph: Graph) -> dict[str, FgDepMeta]
     if deps_meta is None:
         return None
     meta_snapshot = deps_meta["snapshot"]
-    # Take a snapshot of the source hashes from all of the metas we found.
+    # Take a snapshot of the source hashes from all the metas we found.
     # (Including the ones we rejected because they were out of date.)
     # We use this to verify that they match up with the proto_deps.
     current_meta_snapshot = {
@@ -1139,6 +1144,17 @@ def read_deps_cache(manager: BuildManager, graph: Graph) -> dict[str, FgDepMeta]
     return module_deps_metas
 
 
+def _load_ff_file(file: str, manager: BuildManager, log_error: str) -> bytes | None:
+    t0 = time.time()
+    try:
+        data = manager.metastore.read(file)
+    except OSError:
+        manager.log(log_error + file)
+        return None
+    manager.add_stats(metastore_read_time=time.time() - t0)
+    return data
+
+
 def _load_json_file(
     file: str, manager: BuildManager, log_success: str, log_error: str
 ) -> dict[str, Any] | None:
@@ -1259,7 +1275,11 @@ def get_cache_names(id: str, path: str, options: Options) -> tuple[str, str, str
     deps_json = None
     if options.cache_fine_grained:
         deps_json = prefix + ".deps.json"
-    return (prefix + ".meta.json", prefix + ".data.json", deps_json)
+    if options.fixed_format_cache:
+        data_suffix = ".data.ff"
+    else:
+        data_suffix = ".data.json"
+    return (prefix + ".meta.json", prefix + data_suffix, deps_json)
 
 
 def find_cache_meta(id: str, path: str, manager: BuildManager) -> CacheMeta | None:
@@ -1559,8 +1579,13 @@ def write_cache(
         tree.path = path
 
     # Serialize data and analyze interface
-    data = tree.serialize()
-    data_bytes = json_dumps(data, manager.options.debug_cache)
+    if manager.options.fixed_format_cache:
+        data_io = Buffer()
+        tree.write(data_io)
+        data_bytes = data_io.getvalue()
+    else:
+        data = tree.serialize()
+        data_bytes = json_dumps(data, manager.options.debug_cache)
     interface_hash = hash_digest(data_bytes)
 
     plugin_data = manager.plugin.report_config_data(ReportConfigContext(id, path, is_check=False))
@@ -2085,15 +2110,23 @@ def load_tree(self, temporary: bool = False) -> None:
             self.meta is not None
         ), "Internal error: this method must be called only for cached modules"
 
-        data = _load_json_file(
-            self.meta.data_json, self.manager, "Load tree ", "Could not load tree: "
-        )
+        data: bytes | dict[str, Any] | None
+        if self.options.fixed_format_cache:
+            data = _load_ff_file(self.meta.data_json, self.manager, "Could not load tree: ")
+        else:
+            data = _load_json_file(
+                self.meta.data_json, self.manager, "Load tree ", "Could not load tree: "
+            )
         if data is None:
             return
 
         t0 = time.time()
         # TODO: Assert data file wasn't changed.
-        self.tree = MypyFile.deserialize(data)
+        if isinstance(data, bytes):
+            data_io = Buffer(data)
+            self.tree = MypyFile.read(data_io)
+        else:
+            self.tree = MypyFile.deserialize(data)
         t1 = time.time()
         self.manager.add_stats(deserialize_time=t1 - t0)
         if not temporary:
@@ -2481,7 +2514,11 @@ def write_cache(self) -> None:
         ):
             if self.options.debug_serialize:
                 try:
-                    self.tree.serialize()
+                    if self.manager.options.fixed_format_cache:
+                        data = Buffer()
+                        self.tree.write(data)
+                    else:
+                        self.tree.serialize()
                 except Exception:
                     print(f"Error serializing {self.id}", file=self.manager.stdout)
                     raise  # Propagate to display traceback
@@ -3326,8 +3363,31 @@ def process_graph(graph: Graph, manager: BuildManager) -> None:
                 #
                 # TODO: see if it's possible to determine if we need to process only a
                 # _subset_ of the past SCCs instead of having to process them all.
+                if (
+                    not manager.options.test_env
+                    and platform.python_implementation() == "CPython"
+                    and manager.gc_freeze_cycles < MAX_GC_FREEZE_CYCLES
+                ):
+                    # When deserializing cache we create huge amount of new objects, so even
+                    # with our generous GC thresholds, GC is still doing a lot of pointless
+                    # work searching for garbage. So, we temporarily disable it when
+                    # processing fresh SCCs, and then move all the new objects to the oldest
+                    # generation with the freeze()/unfreeze() trick below. This is arguably
+                    # a hack, but it gives huge performance wins for large third-party
+                    # libraries, like torch.
+                    gc.collect()
+                    gc.disable()
                 for prev_scc in fresh_scc_queue:
                     process_fresh_modules(graph, prev_scc, manager)
+                if (
+                    not manager.options.test_env
+                    and platform.python_implementation() == "CPython"
+                    and manager.gc_freeze_cycles < MAX_GC_FREEZE_CYCLES
+                ):
+                    manager.gc_freeze_cycles += 1
+                    gc.freeze()
+                    gc.unfreeze()
+                    gc.enable()
                 fresh_scc_queue = []
             size = len(scc)
             if size == 1:
diff --git a/mypy/cache.py b/mypy/cache.py
new file mode 100644
index 000000000000..08e3b05d1a75
--- /dev/null
+++ b/mypy/cache.py
@@ -0,0 +1,166 @@
+from __future__ import annotations
+
+from collections.abc import Sequence
+from typing import TYPE_CHECKING, Final
+
+from mypy_extensions import u8
+
+try:
+    from native_internal import (
+        Buffer as Buffer,
+        read_bool as read_bool,
+        read_float as read_float,
+        read_int as read_int,
+        read_str as read_str,
+        read_tag as read_tag,
+        write_bool as write_bool,
+        write_float as write_float,
+        write_int as write_int,
+        write_str as write_str,
+        write_tag as write_tag,
+    )
+except ImportError:
+    # TODO: temporary, remove this after we publish mypy-native on PyPI.
+    if not TYPE_CHECKING:
+
+        class Buffer:
+            def __init__(self, source: bytes = b"") -> None:
+                raise NotImplementedError
+
+            def getvalue(self) -> bytes:
+                raise NotImplementedError
+
+        def read_int(data: Buffer) -> int:
+            raise NotImplementedError
+
+        def write_int(data: Buffer, value: int) -> None:
+            raise NotImplementedError
+
+        def read_tag(data: Buffer) -> u8:
+            raise NotImplementedError
+
+        def write_tag(data: Buffer, value: u8) -> None:
+            raise NotImplementedError
+
+        def read_str(data: Buffer) -> str:
+            raise NotImplementedError
+
+        def write_str(data: Buffer, value: str) -> None:
+            raise NotImplementedError
+
+        def read_bool(data: Buffer) -> bool:
+            raise NotImplementedError
+
+        def write_bool(data: Buffer, value: bool) -> None:
+            raise NotImplementedError
+
+        def read_float(data: Buffer) -> float:
+            raise NotImplementedError
+
+        def write_float(data: Buffer, value: float) -> None:
+            raise NotImplementedError
+
+
+# Always use this type alias to refer to type tags.
+Tag = u8
+
+LITERAL_INT: Final[Tag] = 1
+LITERAL_STR: Final[Tag] = 2
+LITERAL_BOOL: Final[Tag] = 3
+LITERAL_FLOAT: Final[Tag] = 4
+LITERAL_COMPLEX: Final[Tag] = 5
+LITERAL_NONE: Final[Tag] = 6
+
+
+def read_literal(data: Buffer, tag: Tag) -> int | str | bool | float:
+    if tag == LITERAL_INT:
+        return read_int(data)
+    elif tag == LITERAL_STR:
+        return read_str(data)
+    elif tag == LITERAL_BOOL:
+        return read_bool(data)
+    elif tag == LITERAL_FLOAT:
+        return read_float(data)
+    assert False, f"Unknown literal tag {tag}"
+
+
+def write_literal(data: Buffer, value: int | str | bool | float | complex | None) -> None:
+    if isinstance(value, bool):
+        write_tag(data, LITERAL_BOOL)
+        write_bool(data, value)
+    elif isinstance(value, int):
+        write_tag(data, LITERAL_INT)
+        write_int(data, value)
+    elif isinstance(value, str):
+        write_tag(data, LITERAL_STR)
+        write_str(data, value)
+    elif isinstance(value, float):
+        write_tag(data, LITERAL_FLOAT)
+        write_float(data, value)
+    elif isinstance(value, complex):
+        write_tag(data, LITERAL_COMPLEX)
+        write_float(data, value.real)
+        write_float(data, value.imag)
+    else:
+        write_tag(data, LITERAL_NONE)
+
+
+def read_int_opt(data: Buffer) -> int | None:
+    if read_bool(data):
+        return read_int(data)
+    return None
+
+
+def write_int_opt(data: Buffer, value: int | None) -> None:
+    if value is not None:
+        write_bool(data, True)
+        write_int(data, value)
+    else:
+        write_bool(data, False)
+
+
+def read_str_opt(data: Buffer) -> str | None:
+    if read_bool(data):
+        return read_str(data)
+    return None
+
+
+def write_str_opt(data: Buffer, value: str | None) -> None:
+    if value is not None:
+        write_bool(data, True)
+        write_str(data, value)
+    else:
+        write_bool(data, False)
+
+
+def read_int_list(data: Buffer) -> list[int]:
+    size = read_int(data)
+    return [read_int(data) for _ in range(size)]
+
+
+def write_int_list(data: Buffer, value: list[int]) -> None:
+    write_int(data, len(value))
+    for item in value:
+        write_int(data, item)
+
+
+def read_str_list(data: Buffer) -> list[str]:
+    size = read_int(data)
+    return [read_str(data) for _ in range(size)]
+
+
+def write_str_list(data: Buffer, value: Sequence[str]) -> None:
+    write_int(data, len(value))
+    for item in value:
+        write_str(data, item)
+
+
+def read_str_opt_list(data: Buffer) -> list[str | None]:
+    size = read_int(data)
+    return [read_str_opt(data) for _ in range(size)]
+
+
+def write_str_opt_list(data: Buffer, value: list[str | None]) -> None:
+    write_int(data, len(value))
+    for item in value:
+        write_str_opt(data, item)
diff --git a/mypy/checker.py b/mypy/checker.py
index 0639340d30bb..12a86fe6fba1 100644
--- a/mypy/checker.py
+++ b/mypy/checker.py
@@ -6,7 +6,18 @@
 from collections import defaultdict
 from collections.abc import Iterable, Iterator, Mapping, Sequence, Set as AbstractSet
 from contextlib import ExitStack, contextmanager
-from typing import Callable, Final, Generic, NamedTuple, Optional, TypeVar, Union, cast, overload
+from typing import (
+    Callable,
+    Final,
+    Generic,
+    Literal,
+    NamedTuple,
+    Optional,
+    TypeVar,
+    Union,
+    cast,
+    overload,
+)
 from typing_extensions import TypeAlias as _TypeAlias, TypeGuard
 
 import mypy.checkexpr
@@ -25,7 +36,14 @@
 from mypy.constraints import SUPERTYPE_OF
 from mypy.erasetype import erase_type, erase_typevars, remove_instance_last_known_values
 from mypy.errorcodes import TYPE_VAR, UNUSED_AWAITABLE, UNUSED_COROUTINE, ErrorCode
-from mypy.errors import ErrorInfo, Errors, ErrorWatcher, LoopErrorWatcher, report_internal_error
+from mypy.errors import (
+    ErrorInfo,
+    Errors,
+    ErrorWatcher,
+    IterationDependentErrors,
+    IterationErrorWatcher,
+    report_internal_error,
+)
 from mypy.expandtype import expand_type
 from mypy.literals import Key, extract_var_from_literal_hash, literal, literal_hash
 from mypy.maptype import map_instance_to_supertype
@@ -72,6 +90,7 @@
     ContinueStmt,
     Decorator,
     DelStmt,
+    DictExpr,
     EllipsisExpr,
     Expression,
     ExpressionStmt,
@@ -100,11 +119,13 @@
     OperatorAssignmentStmt,
     OpExpr,
     OverloadedFuncDef,
+    OverloadPart,
     PassStmt,
     PromoteExpr,
     RaiseStmt,
     RefExpr,
     ReturnStmt,
+    SetExpr,
     StarExpr,
     Statement,
     StrExpr,
@@ -122,6 +143,7 @@
     WhileStmt,
     WithStmt,
     YieldExpr,
+    get_func_def,
     is_final_node,
 )
 from mypy.operators import flip_ops, int_op_to_method, neg_ops
@@ -151,6 +173,7 @@
 from mypy.typeanal import check_for_explicit_any, has_any_from_unimported_type, make_optional_type
 from mypy.typeops import (
     bind_self,
+    can_have_shared_disjoint_base,
     coerce_to_literal,
     custom_special_method,
     erase_def_to_union_or_bound,
@@ -268,6 +291,26 @@ class PartialTypeScope(NamedTuple):
     is_local: bool
 
 
+class LocalTypeMap:
+    """Store inferred types into a temporary type map (returned).
+
+    This can be used to perform type checking "experiments" without
+    affecting exported types (which are used by mypyc).
+    """
+
+    def __init__(self, chk: TypeChecker) -> None:
+        self.chk = chk
+
+    def __enter__(self) -> dict[Expression, Type]:
+        temp_type_map: dict[Expression, Type] = {}
+        self.chk._type_maps.append(temp_type_map)
+        return temp_type_map
+
+    def __exit__(self, exc_type: object, exc_val: object, exc_tb: object) -> Literal[False]:
+        self.chk._type_maps.pop()
+        return False
+
+
 class TypeChecker(NodeVisitor[None], TypeCheckerSharedApi):
     """Mypy type checker.
 
@@ -350,6 +393,9 @@ class TypeChecker(NodeVisitor[None], TypeCheckerSharedApi):
     # functions such as open(), etc.
     plugin: Plugin
 
+    # A helper state to produce unique temporary names on demand.
+    _unique_id: int
+
     def __init__(
         self,
         errors: Errors,
@@ -389,6 +435,8 @@ def __init__(
         self.is_stub = tree.is_stub
         self.is_typeshed_stub = tree.is_typeshed_file(options)
         self.inferred_attribute_types = None
+        self.allow_constructor_cache = True
+        self.local_type_map = LocalTypeMap(self)
 
         # If True, process function definitions. If False, don't. This is used
         # for processing module top levels in fine-grained incremental mode.
@@ -400,6 +448,11 @@ def __init__(
         # argument through various `checker` and `checkmember` functions.
         self._is_final_def = False
 
+        # Track when we enter an overload implementation. Some checks should not be applied
+        # to the implementation signature when specific overloads are available.
+        # Use `enter_overload_impl` to modify.
+        self.overload_impl_stack: list[OverloadPart] = []
+
         # This flag is set when we run type-check or attribute access check for the purpose
         # of giving a note on possibly missing "await". It is used to avoid infinite recursion.
         self.checking_missing_await = False
@@ -413,7 +466,15 @@ def __init__(
         self._expr_checker = mypy.checkexpr.ExpressionChecker(
             self, self.msg, self.plugin, per_line_checking_time_ns
         )
+
+        self._str_type: Instance | None = None
+        self._function_type: Instance | None = None
+        self._int_type: Instance | None = None
+        self._bool_type: Instance | None = None
+        self._object_type: Instance | None = None
+
         self.pattern_checker = PatternChecker(self, self.msg, self.plugin, options)
+        self._unique_id = 0
 
     @property
     def expr_checker(self) -> mypy.checkexpr.ExpressionChecker:
@@ -435,7 +496,6 @@ def reset(self) -> None:
         self.binder = ConditionalTypeBinder(self.options)
         self._type_maps[1:] = []
         self._type_maps[0].clear()
-        self.temp_type_map = None
         self.expr_checker.reset()
         self.deferred_nodes = []
         self.partial_types = []
@@ -487,12 +547,16 @@ def check_first_pass(self) -> None:
                         )
 
     def check_second_pass(
-        self, todo: Sequence[DeferredNode | FineGrainedDeferredNode] | None = None
+        self,
+        todo: Sequence[DeferredNode | FineGrainedDeferredNode] | None = None,
+        *,
+        allow_constructor_cache: bool = True,
     ) -> bool:
         """Run second or following pass of type checking.
 
         This goes through deferred nodes, returning True if there were any.
         """
+        self.allow_constructor_cache = allow_constructor_cache
         self.recurse_into_functions = True
         with state.strict_optional_set(self.options.strict_optional), checker_state.set(self):
             if not todo and not self.deferred_nodes:
@@ -598,26 +662,15 @@ def accept_loop(
             # on without bound otherwise)
             widened_old = len(self.widened_vars)
 
-            # one set of `unreachable`, `redundant-expr`, and `redundant-casts` errors
-            # per iteration step:
-            uselessness_errors = []
-            # one set of unreachable line numbers per iteration step:
-            unreachable_lines = []
-            # one set of revealed types per line where `reveal_type` is used (each
-            # created set can grow during the iteration):
-            revealed_types = defaultdict(set)
+            iter_errors = IterationDependentErrors()
             iter = 1
             while True:
                 with self.binder.frame_context(can_skip=True, break_frame=2, continue_frame=1):
                     if on_enter_body is not None:
                         on_enter_body()
 
-                    with LoopErrorWatcher(self.msg.errors) as watcher:
+                    with IterationErrorWatcher(self.msg.errors, iter_errors):
                         self.accept(body)
-                    uselessness_errors.append(watcher.uselessness_errors)
-                    unreachable_lines.append(watcher.unreachable_lines)
-                    for key, values in watcher.revealed_types.items():
-                        revealed_types[key].update(values)
 
                 partials_new = sum(len(pts.map) for pts in self.partial_types)
                 widened_new = len(self.widened_vars)
@@ -639,29 +692,7 @@ def accept_loop(
                 if iter == 20:
                     raise RuntimeError("Too many iterations when checking a loop")
 
-            # Report only those `unreachable`, `redundant-expr`, and `redundant-casts`
-            # errors that could not be ruled out in any iteration step:
-            persistent_uselessness_errors = set()
-            for candidate in set(itertools.chain(*uselessness_errors)):
-                if all(
-                    (candidate in errors) or (candidate[2] in lines)
-                    for errors, lines in zip(uselessness_errors, unreachable_lines)
-                ):
-                    persistent_uselessness_errors.add(candidate)
-            for error_info in persistent_uselessness_errors:
-                context = Context(line=error_info[2], column=error_info[3])
-                context.end_line = error_info[4]
-                context.end_column = error_info[5]
-                self.msg.fail(error_info[1], context, code=error_info[0])
-
-            #  Report all types revealed in at least one iteration step:
-            for note_info, types in revealed_types.items():
-                sorted_ = sorted(types, key=lambda typ: typ.lower())
-                revealed = sorted_[0] if len(types) == 1 else f"Union[{', '.join(sorted_)}]"
-                context = Context(line=note_info[1], column=note_info[2])
-                context.end_line = note_info[3]
-                context.end_column = note_info[4]
-                self.note(f'Revealed type is "{revealed}"', context)
+            self.msg.iteration_dependent_errors(iter_errors)
 
             # If exit_condition is set, assume it must be False on exit from the loop:
             if exit_condition:
@@ -715,6 +746,12 @@ def _visit_overloaded_func_def(self, defn: OverloadedFuncDef) -> None:
                     # TODO: keep precise type for callables with tricky but valid signatures.
                     setter_type = fallback_setter_type
                 defn.items[0].var.setter_type = setter_type
+                if isinstance(defn.type, Overloaded):
+                    # Update legacy property type for decorated properties.
+                    getter_type = self.extract_callable_type(defn.items[0].var.type, defn)
+                    if getter_type is not None:
+                        getter_type.definition = defn.items[0]
+                        defn.type.items[0] = getter_type
         for i, fdef in enumerate(defn.items):
             assert isinstance(fdef, Decorator)
             if defn.is_property:
@@ -732,7 +769,8 @@ def _visit_overloaded_func_def(self, defn: OverloadedFuncDef) -> None:
         if num_abstract not in (0, len(defn.items)):
             self.fail(message_registry.INCONSISTENT_ABSTRACT_OVERLOAD, defn)
         if defn.impl:
-            defn.impl.accept(self)
+            with self.enter_overload_impl(defn.impl):
+                defn.impl.accept(self)
         if not defn.is_property:
             self.check_overlapping_overloads(defn)
             if defn.type is None:
@@ -741,6 +779,7 @@ def _visit_overloaded_func_def(self, defn: OverloadedFuncDef) -> None:
                     assert isinstance(item, Decorator)
                     item_type = self.extract_callable_type(item.var.type, item)
                     if item_type is not None:
+                        item_type.definition = item
                         item_types.append(item_type)
                 if item_types:
                     defn.type = Overloaded(item_types)
@@ -775,6 +814,14 @@ def _visit_overloaded_func_def(self, defn: OverloadedFuncDef) -> None:
             self.check_explicit_override_decorator(defn, found_method_base_classes, defn.impl)
             self.check_inplace_operator_method(defn)
 
+    @contextmanager
+    def enter_overload_impl(self, impl: OverloadPart) -> Iterator[None]:
+        self.overload_impl_stack.append(impl)
+        try:
+            yield
+        finally:
+            assert self.overload_impl_stack.pop() == impl
+
     def extract_callable_type(self, inner_type: Type | None, ctx: Context) -> CallableType | None:
         """Get type as seen by an overload item caller."""
         inner_type = get_proper_type(inner_type)
@@ -834,8 +881,10 @@ def check_overlapping_overloads(self, defn: OverloadedFuncDef) -> None:
         # At this point we should have set the impl already, and all remaining
         # items are decorators
 
-        if self.msg.errors.file in self.msg.errors.ignored_files or (
-            self.is_typeshed_stub and self.options.test_env
+        if (
+            self.options.ignore_errors
+            or self.msg.errors.file in self.msg.errors.ignored_files
+            or (self.is_typeshed_stub and self.options.test_env)
         ):
             # This is a little hacky, however, the quadratic check here is really expensive, this
             # method has no side effects, so we should skip it if we aren't going to report
@@ -1301,7 +1350,11 @@ def check_func_def(
                     )
 
                 if name:  # Special method names
-                    if defn.info and self.is_reverse_op_method(name):
+                    if (
+                        defn.info
+                        and self.is_reverse_op_method(name)
+                        and defn not in self.overload_impl_stack
+                    ):
                         self.check_reverse_op_method(item, typ, name, defn)
                     elif name in ("__getattr__", "__getattribute__"):
                         self.check_getattr_method(typ, defn, name)
@@ -1362,7 +1415,7 @@ def check_func_def(
                 if typ.type_is:
                     arg_index = 0
                     # For methods and classmethods, we want the second parameter
-                    if ref_type is not None and (not defn.is_static or defn.name == "__new__"):
+                    if ref_type is not None and defn.has_self_or_cls_argument:
                         arg_index = 1
                     if arg_index < len(typ.arg_types) and not is_subtype(
                         typ.type_is, typ.arg_types[arg_index]
@@ -1376,49 +1429,19 @@ def check_func_def(
                         )
 
                 # Store argument types.
+                found_self = False
+                if isinstance(defn, FuncDef) and not defn.is_decorated:
+                    found_self = self.require_correct_self_argument(typ, defn)
                 for i in range(len(typ.arg_types)):
                     arg_type = typ.arg_types[i]
-                    if (
-                        isinstance(defn, FuncDef)
-                        and ref_type is not None
-                        and i == 0
-                        and (not defn.is_static or defn.name == "__new__")
-                        and typ.arg_kinds[0] not in [nodes.ARG_STAR, nodes.ARG_STAR2]
-                    ):
-                        if defn.is_class or defn.name == "__new__":
-                            ref_type = mypy.types.TypeType.make_normalized(ref_type)
-                        if not is_same_type(arg_type, ref_type):
-                            # This level of erasure matches the one in checkmember.check_self_arg(),
-                            # better keep these two checks consistent.
-                            erased = get_proper_type(erase_typevars(erase_to_bound(arg_type)))
-                            if not is_subtype(ref_type, erased, ignore_type_params=True):
-                                if (
-                                    isinstance(erased, Instance)
-                                    and erased.type.is_protocol
-                                    or isinstance(erased, TypeType)
-                                    and isinstance(erased.item, Instance)
-                                    and erased.item.type.is_protocol
-                                ):
-                                    # We allow the explicit self-type to be not a supertype of
-                                    # the current class if it is a protocol. For such cases
-                                    # the consistency check will be performed at call sites.
-                                    msg = None
-                                elif typ.arg_names[i] in {"self", "cls"}:
-                                    msg = message_registry.ERASED_SELF_TYPE_NOT_SUPERTYPE.format(
-                                        erased.str_with_options(self.options),
-                                        ref_type.str_with_options(self.options),
-                                    )
-                                else:
-                                    msg = message_registry.MISSING_OR_INVALID_SELF_TYPE
-                                if msg:
-                                    self.fail(msg, defn)
-                    elif isinstance(arg_type, TypeVarType):
+                    if isinstance(arg_type, TypeVarType):
                         # Refuse covariant parameter type variables
                         # TODO: check recursively for inner type variables
                         if (
                             arg_type.variance == COVARIANT
                             and defn.name not in ("__init__", "__new__", "__post_init__")
                             and not is_private(defn.name)  # private methods are not inherited
+                            and (i != 0 or not found_self)
                         ):
                             ctx: Context = arg_type
                             if ctx.line < 0:
@@ -1472,7 +1495,19 @@ def check_func_def(
                     # TODO: Find a way of working around this limitation
                     if _is_empty_generator_function(item) or len(expanded) >= 2:
                         self.binder.suppress_unreachable_warnings()
-                    self.accept(item.body)
+                    # When checking a third-party library, we can skip function body,
+                    # if during semantic analysis we found that there are no attributes
+                    # defined via self here.
+                    if (
+                        not (
+                            self.options.ignore_errors
+                            or self.msg.errors.file in self.msg.errors.ignored_files
+                        )
+                        or self.options.preserve_asts
+                        or not isinstance(defn, FuncDef)
+                        or defn.has_self_attr_def
+                    ):
+                        self.accept(item.body)
                 unreachable = self.binder.is_unreachable()
                 if new_frame is not None:
                     self.binder.pop_frame(True, 0)
@@ -1568,6 +1603,69 @@ def check_func_def(
 
             self.binder = old_binder
 
+    def require_correct_self_argument(self, func: Type, defn: FuncDef) -> bool:
+        func = get_proper_type(func)
+        if not isinstance(func, CallableType):
+            return False
+
+        # Do not report errors for untyped methods in classes nested in untyped funcs.
+        if not (
+            self.options.check_untyped_defs
+            or len(self.dynamic_funcs) < 2
+            or not self.dynamic_funcs[-2]
+            or not defn.is_dynamic()
+        ):
+            return bool(func.arg_types)
+
+        with self.scope.push_function(defn):
+            # We temporary push the definition to get the self type as
+            # visible from *inside* of this function/method.
+            ref_type: Type | None = self.scope.active_self_type()
+            if ref_type is None:
+                return False
+
+        if not defn.has_self_or_cls_argument or (
+            func.arg_kinds and func.arg_kinds[0] in [nodes.ARG_STAR, nodes.ARG_STAR2]
+        ):
+            return False
+
+        if not func.arg_types:
+            self.fail(
+                'Method must have at least one argument. Did you forget the "self" argument?', defn
+            )
+            return False
+
+        arg_type = func.arg_types[0]
+        if defn.is_class or defn.name == "__new__":
+            ref_type = mypy.types.TypeType.make_normalized(ref_type)
+        if is_same_type(arg_type, ref_type):
+            return True
+
+        # This level of erasure matches the one in checkmember.check_self_arg(),
+        # better keep these two checks consistent.
+        erased = get_proper_type(erase_typevars(erase_to_bound(arg_type)))
+        if not is_subtype(ref_type, erased, ignore_type_params=True):
+            if (
+                isinstance(erased, Instance)
+                and erased.type.is_protocol
+                or isinstance(erased, TypeType)
+                and isinstance(erased.item, Instance)
+                and erased.item.type.is_protocol
+            ):
+                # We allow the explicit self-type to be not a supertype of
+                # the current class if it is a protocol. For such cases
+                # the consistency check will be performed at call sites.
+                msg = None
+            elif func.arg_names[0] in {"self", "cls"}:
+                msg = message_registry.ERASED_SELF_TYPE_NOT_SUPERTYPE.format(
+                    erased.str_with_options(self.options), ref_type.str_with_options(self.options)
+                )
+            else:
+                msg = message_registry.MISSING_OR_INVALID_SELF_TYPE
+            if msg:
+                self.fail(msg, defn)
+        return True
+
     def is_var_redefined_in_outer_context(self, v: Var, after_line: int) -> bool:
         """Can the variable be assigned to at module top level or outer function?
 
@@ -2092,6 +2190,9 @@ def check_method_override(
 
         Return a list of base classes which contain an attribute with the method name.
         """
+        if self.options.ignore_errors or self.msg.errors.file in self.msg.errors.ignored_files:
+            # Method override checks may be expensive, so skip them in third-party libraries.
+            return None
         # Check against definitions in base classes.
         check_override_compatibility = (
             defn.name not in ("__init__", "__new__", "__init_subclass__", "__post_init__")
@@ -2195,7 +2296,14 @@ def check_method_override_for_base_with_name(
         else:
             override_class_or_static = defn.func.is_class or defn.func.is_static
         typ, _ = self.node_type_from_base(defn.name, defn.info, defn)
-        assert typ is not None
+        if typ is None:
+            # This may only happen if we're checking `x-redefinition` member
+            # and `x` itself is for some reason gone. Normally the node should
+            # be reachable from the containing class by its name.
+            # The redefinition is never removed, use this as a sanity check to verify
+            # the reasoning above.
+            assert f"{defn.name}-redefinition" in defn.info.names
+            return False
 
         original_node = base_attr.node
         # `original_type` can be partial if (e.g.) it is originally an
@@ -2442,8 +2550,9 @@ def check_override(
 
                 override_ids = override.type_var_ids()
                 type_name = None
-                if isinstance(override.definition, FuncDef):
-                    type_name = override.definition.info.name
+                definition = get_func_def(override)
+                if isinstance(definition, FuncDef):
+                    type_name = definition.info.name
 
                 def erase_override(t: Type) -> Type:
                     return erase_typevars(t, ids_to_erase=override_ids)
@@ -2552,6 +2661,8 @@ def visit_class_def(self, defn: ClassDef) -> None:
         for base in typ.mro[1:]:
             if base.is_final:
                 self.fail(message_registry.CANNOT_INHERIT_FROM_FINAL.format(base.name), defn)
+        if not can_have_shared_disjoint_base(typ.bases):
+            self.fail(message_registry.INCOMPATIBLE_DISJOINT_BASES.format(typ.name), defn)
         with self.tscope.class_scope(defn.info), self.enter_partial_types(is_class=True):
             old_binder = self.binder
             self.binder = ConditionalTypeBinder(self.options)
@@ -2956,23 +3067,18 @@ def check_metaclass_compatibility(self, typ: TypeInfo) -> None:
         ):
             return  # Reasonable exceptions from this check
 
-        metaclasses = [
-            entry.metaclass_type
-            for entry in typ.mro[1:-1]
-            if entry.metaclass_type
-            and not is_named_instance(entry.metaclass_type, "builtins.type")
-        ]
-        if not metaclasses:
-            return
-        if typ.metaclass_type is not None and all(
-            is_subtype(typ.metaclass_type, meta) for meta in metaclasses
+        if typ.metaclass_type is None and any(
+            base.type.metaclass_type is not None for base in typ.bases
         ):
-            return
-        self.fail(
-            "Metaclass conflict: the metaclass of a derived class must be "
-            "a (non-strict) subclass of the metaclasses of all its bases",
-            typ,
-        )
+            self.fail(
+                "Metaclass conflict: the metaclass of a derived class must be "
+                "a (non-strict) subclass of the metaclasses of all its bases",
+                typ,
+                code=codes.METACLASS,
+            )
+            explanation = typ.explain_metaclass_conflict()
+            if explanation:
+                self.note(explanation, typ, code=codes.METACLASS)
 
     def visit_import_from(self, node: ImportFrom) -> None:
         for name, _ in node.names:
@@ -3024,6 +3130,8 @@ def visit_block(self, b: Block) -> None:
                     break
             else:
                 self.accept(s)
+                # Clear expression cache after each statement to avoid unlimited growth.
+                self.expr_checker.expr_cache.clear()
 
     def should_report_unreachable_issues(self) -> bool:
         return (
@@ -3050,7 +3158,7 @@ def is_noop_for_reachability(self, s: Statement) -> bool:
             if isinstance(s.expr, EllipsisExpr):
                 return True
             elif isinstance(s.expr, CallExpr):
-                with self.expr_checker.msg.filter_errors():
+                with self.expr_checker.msg.filter_errors(filter_revealed_type=True):
                     typ = get_proper_type(
                         self.expr_checker.accept(
                             s.expr, allow_none_return=True, always_allow_any=True
@@ -3150,7 +3258,7 @@ def check_assignment(
                         else:
                             self.check_getattr_method(signature, lvalue, name)
 
-                if name == "__slots__":
+                if name == "__slots__" and self.scope.active_class() is not None:
                     typ = lvalue_type or self.expr_checker.accept(rvalue)
                     self.check_slots_definition(typ, lvalue)
                 if name == "__match_args__" and inferred is not None:
@@ -3329,6 +3437,12 @@ def get_variable_type_context(self, inferred: Var, rvalue: Expression) -> Type |
                     type_contexts.append(base_type)
         # Use most derived supertype as type context if available.
         if not type_contexts:
+            if inferred.name == "__slots__" and self.scope.active_class() is not None:
+                str_type = self.named_type("builtins.str")
+                return self.named_generic_type("typing.Iterable", [str_type])
+            if inferred.name == "__all__" and self.scope.is_top_level():
+                str_type = self.named_type("builtins.str")
+                return self.named_generic_type("typing.Sequence", [str_type])
             return None
         candidate = type_contexts[0]
         for other in type_contexts:
@@ -3447,6 +3561,7 @@ def check_compatibility_all_supers(self, lvalue: RefExpr, rvalue: Expression) ->
                     continue
 
                 base_type, base_node = self.node_type_from_base(lvalue_node.name, base, lvalue)
+                # TODO: if the r.h.s. is a descriptor, we should check setter override as well.
                 custom_setter = is_custom_settable_property(base_node)
                 if isinstance(base_type, PartialType):
                     base_type = None
@@ -3711,6 +3826,9 @@ def check_assignment_to_slots(self, lvalue: Lvalue) -> None:
             return
 
         inst = get_proper_type(self.expr_checker.accept(lvalue.expr))
+        if isinstance(inst, TypeVarType) and inst.id.is_self():
+            # Unwrap self type
+            inst = get_proper_type(inst.upper_bound)
         if not isinstance(inst, Instance):
             return
         if inst.type.slots is None:
@@ -3999,7 +4117,7 @@ def check_multi_assignment_from_union(
                 for t, lv in zip(transposed, self.flatten_lvalues(lvalues)):
                     # We can access _type_maps directly since temporary type maps are
                     # only created within expressions.
-                    t.append(self._type_maps[0].pop(lv, AnyType(TypeOfAny.special_form)))
+                    t.append(self._type_maps[-1].pop(lv, AnyType(TypeOfAny.special_form)))
         union_types = tuple(make_simplified_union(col) for col in transposed)
         for expr, items in assignments.items():
             # Bind a union of types collected in 'assignments' to every expression.
@@ -4400,9 +4518,9 @@ def set_inferred_type(self, var: Var, lvalue: Lvalue, type: Type) -> None:
         refers to the variable (lvalue). If var is None, do nothing.
         """
         if var and not self.current_node_deferred:
-            # TODO: should we also set 'is_ready = True' here?
             var.type = type
             var.is_inferred = True
+            var.is_ready = True
             if var not in self.var_decl_frames:
                 # Used for the hack to improve optional type inference in conditionals
                 self.var_decl_frames[var] = {frame.id for frame in self.binder.frames}
@@ -4412,9 +4530,25 @@ def set_inferred_type(self, var: Var, lvalue: Lvalue, type: Type) -> None:
                     self.inferred_attribute_types[lvalue.def_var] = type
             self.store_type(lvalue, type)
             p_type = get_proper_type(type)
-            if isinstance(p_type, CallableType) and is_node_static(p_type.definition):
-                # TODO: handle aliases to class methods (similarly).
-                var.is_staticmethod = True
+            definition = None
+            if isinstance(p_type, CallableType):
+                definition = p_type.definition
+            elif isinstance(p_type, Overloaded):
+                # Randomly select first item, if items are different, there will
+                # be an error during semantic analysis.
+                definition = p_type.items[0].definition
+            if definition:
+                if is_node_static(definition):
+                    var.is_staticmethod = True
+                elif is_classmethod_node(definition):
+                    var.is_classmethod = True
+                elif is_property(definition):
+                    var.is_property = True
+                    if isinstance(p_type, Overloaded):
+                        # TODO: in theory we can have a property with a deleter only.
+                        var.is_settable_property = True
+                        assert isinstance(definition, Decorator), definition
+                        var.setter_type = definition.var.setter_type
 
     def set_inference_error_fallback_type(self, var: Var, lvalue: Lvalue, type: Type) -> None:
         """Store best known type for variable if type inference failed.
@@ -4534,7 +4668,7 @@ def check_simple_assignment(
                 # may cause some perf impact, plus we want to partially preserve
                 # the old behavior. This helps with various practical examples, see
                 # e.g. testOptionalTypeNarrowedByGenericCall.
-                with self.msg.filter_errors() as local_errors, self.local_type_map() as type_map:
+                with self.msg.filter_errors() as local_errors, self.local_type_map as type_map:
                     alt_rvalue_type = self.expr_checker.accept(
                         rvalue, None, always_allow_any=always_allow_any
                     )
@@ -4580,7 +4714,7 @@ def check_member_assignment(
         self,
         lvalue: MemberExpr,
         instance_type: Type,
-        attribute_type: Type,
+        set_lvalue_type: Type,
         rvalue: Expression,
         context: Context,
     ) -> tuple[Type, Type, bool]:
@@ -4597,23 +4731,21 @@ def check_member_assignment(
         if (isinstance(instance_type, FunctionLike) and instance_type.is_type_obj()) or isinstance(
             instance_type, TypeType
         ):
-            rvalue_type, _ = self.check_simple_assignment(attribute_type, rvalue, context)
-            return rvalue_type, attribute_type, True
+            rvalue_type, _ = self.check_simple_assignment(set_lvalue_type, rvalue, context)
+            return rvalue_type, set_lvalue_type, True
 
         with self.msg.filter_errors(filter_deprecated=True):
             get_lvalue_type = self.expr_checker.analyze_ordinary_member_access(
                 lvalue, is_lvalue=False
             )
 
-        # Special case: if the rvalue_type is a subtype of both '__get__' and '__set__' types,
-        # and '__get__' type is narrower than '__set__', then we invoke the binder to narrow type
+        # Special case: if the rvalue_type is a subtype of '__get__' type, and
+        # '__get__' type is narrower than '__set__', then we invoke the binder to narrow type
         # by this assignment. Technically, this is not safe, but in practice this is
         # what a user expects.
-        rvalue_type, _ = self.check_simple_assignment(attribute_type, rvalue, context)
-        infer = is_subtype(rvalue_type, get_lvalue_type) and is_subtype(
-            get_lvalue_type, attribute_type
-        )
-        return rvalue_type if infer else attribute_type, attribute_type, infer
+        rvalue_type, _ = self.check_simple_assignment(set_lvalue_type, rvalue, context)
+        rvalue_type = rvalue_type if is_subtype(rvalue_type, get_lvalue_type) else get_lvalue_type
+        return rvalue_type, set_lvalue_type, is_subtype(get_lvalue_type, set_lvalue_type)
 
     def check_indexed_assignment(
         self, lvalue: IndexExpr, rvalue: Expression, context: Context
@@ -4646,6 +4778,8 @@ def replace_partial_type(
     ) -> None:
         """Replace the partial type of var with a non-partial type."""
         var.type = new_type
+        # Updating a partial type should invalidate expression caches.
+        self.binder.version += 1
         del partial_types[var]
         if self.options.allow_redefinition_new:
             # When using --allow-redefinition-new, binder tracks all types of
@@ -4727,6 +4861,42 @@ def visit_return_stmt(self, s: ReturnStmt) -> None:
         self.check_return_stmt(s)
         self.binder.unreachable()
 
+    def infer_context_dependent(
+        self, expr: Expression, type_ctx: Type, allow_none_func_call: bool
+    ) -> ProperType:
+        """Infer type of an expression with fallback to empty type context."""
+        with self.msg.filter_errors(
+            filter_errors=True, filter_deprecated=True, save_filtered_errors=True
+        ) as msg:
+            with self.local_type_map as type_map:
+                typ = get_proper_type(
+                    self.expr_checker.accept(
+                        expr, type_ctx, allow_none_return=allow_none_func_call
+                    )
+                )
+        if not msg.has_new_errors():
+            self.store_types(type_map)
+            return typ
+
+        # If there are errors with the original type context, try re-inferring in empty context.
+        original_messages = msg.filtered_errors()
+        original_type_map = type_map
+        with self.msg.filter_errors(
+            filter_errors=True, filter_deprecated=True, save_filtered_errors=True
+        ) as msg:
+            with self.local_type_map as type_map:
+                alt_typ = get_proper_type(
+                    self.expr_checker.accept(expr, None, allow_none_return=allow_none_func_call)
+                )
+        if not msg.has_new_errors() and is_subtype(alt_typ, type_ctx):
+            self.store_types(type_map)
+            return alt_typ
+
+        # If empty fallback didn't work, use results from the original type context.
+        self.msg.add_errors(original_messages)
+        self.store_types(original_type_map)
+        return typ
+
     def check_return_stmt(self, s: ReturnStmt) -> None:
         defn = self.scope.current_function()
         if defn is not None:
@@ -4759,11 +4929,18 @@ def check_return_stmt(self, s: ReturnStmt) -> None:
                 allow_none_func_call = is_lambda or declared_none_return or declared_any_return
 
                 # Return with a value.
-                typ = get_proper_type(
-                    self.expr_checker.accept(
-                        s.expr, return_type, allow_none_return=allow_none_func_call
+                if isinstance(s.expr, (CallExpr, ListExpr, TupleExpr, DictExpr, SetExpr, OpExpr)):
+                    # For expressions that (strongly) depend on type context (i.e. those that
+                    # are handled like a function call), we allow fallback to empty type context
+                    # in case of errors, this improves user experience in some cases,
+                    # see e.g. testReturnFallbackInference.
+                    typ = self.infer_context_dependent(s.expr, return_type, allow_none_func_call)
+                else:
+                    typ = get_proper_type(
+                        self.expr_checker.accept(
+                            s.expr, return_type, allow_none_return=allow_none_func_call
+                        )
                     )
-                )
                 # Treat NotImplemented as having type Any, consistent with its
                 # definition in typeshed prior to python/typeshed#4222.
                 if (
@@ -4873,17 +5050,7 @@ def visit_operator_assignment_stmt(self, s: OperatorAssignmentStmt) -> None:
         inplace, method = infer_operator_assignment_method(lvalue_type, s.op)
         if inplace:
             # There is __ifoo__, treat as x = x.__ifoo__(y)
-            rvalue_type, method_type = self.expr_checker.check_op(method, lvalue_type, s.rvalue, s)
-            if isinstance(inst := get_proper_type(lvalue_type), Instance) and isinstance(
-                defn := inst.type.get_method(method), OverloadedFuncDef
-            ):
-                for item in defn.items:
-                    if (
-                        isinstance(item, Decorator)
-                        and isinstance(typ := item.func.type, CallableType)
-                        and (bind_self(typ) == method_type)
-                    ):
-                        self.warn_deprecated(item.func, s)
+            rvalue_type, _ = self.expr_checker.check_op(method, lvalue_type, s.rvalue, s)
             if not is_subtype(rvalue_type, lvalue_type):
                 self.msg.incompatible_operator_assignment(s.op, s)
         else:
@@ -4948,6 +5115,9 @@ def type_check_raise(self, e: Expression, s: RaiseStmt, optional: bool = False)
 
     def visit_try_stmt(self, s: TryStmt) -> None:
         """Type check a try statement."""
+
+        iter_errors = None
+
         # Our enclosing frame will get the result if the try/except falls through.
         # This one gets all possible states after the try block exited abnormally
         # (by exception, return, break, etc.)
@@ -4962,7 +5132,9 @@ def visit_try_stmt(self, s: TryStmt) -> None:
             self.visit_try_without_finally(s, try_frame=bool(s.finally_body))
             if s.finally_body:
                 # First we check finally_body is type safe on all abnormal exit paths
-                self.accept(s.finally_body)
+                iter_errors = IterationDependentErrors()
+                with IterationErrorWatcher(self.msg.errors, iter_errors):
+                    self.accept(s.finally_body)
 
         if s.finally_body:
             # Then we try again for the more restricted set of options
@@ -4976,8 +5148,11 @@ def visit_try_stmt(self, s: TryStmt) -> None:
             # type checks in both contexts, but only the resulting types
             # from the latter context affect the type state in the code
             # that follows the try statement.)
+            assert iter_errors is not None
             if not self.binder.is_unreachable():
-                self.accept(s.finally_body)
+                with IterationErrorWatcher(self.msg.errors, iter_errors):
+                    self.accept(s.finally_body)
+            self.msg.iteration_dependent_errors(iter_errors)
 
     def visit_try_without_finally(self, s: TryStmt, try_frame: bool) -> None:
         """Type check a try statement, ignoring the finally block.
@@ -5277,7 +5452,10 @@ def visit_decorator_inner(
             )
         if non_trivial_decorator:
             self.check_untyped_after_decorator(sig, e.func)
+        self.require_correct_self_argument(sig, e.func)
         sig = set_callable_name(sig, e.func)
+        if isinstance(sig, CallableType):
+            sig.definition = e
         e.var.type = sig
         e.var.is_ready = True
         if e.func.is_property:
@@ -5372,7 +5550,7 @@ def visit_with_stmt(self, s: WithStmt) -> None:
             self.accept(s.body)
 
     def check_untyped_after_decorator(self, typ: Type, func: FuncDef) -> None:
-        if not self.options.disallow_any_decorated or self.is_stub:
+        if not self.options.disallow_any_decorated or self.is_stub or self.current_node_deferred:
             return
 
         if mypy.checkexpr.has_any_type(typ):
@@ -5419,21 +5597,10 @@ def visit_continue_stmt(self, s: ContinueStmt) -> None:
         return
 
     def visit_match_stmt(self, s: MatchStmt) -> None:
-        named_subject: Expression
-        if isinstance(s.subject, CallExpr):
-            # Create a dummy subject expression to handle cases where a match statement's subject
-            # is not a literal value. This lets us correctly narrow types and check exhaustivity
-            # This is hack!
-            if s.subject_dummy is None:
-                id = s.subject.callee.fullname if isinstance(s.subject.callee, RefExpr) else ""
-                name = "dummy-match-" + id
-                v = Var(name)
-                s.subject_dummy = NameExpr(name)
-                s.subject_dummy.node = v
-            named_subject = s.subject_dummy
-        else:
-            named_subject = s.subject
-
+        # In sync with similar actions elsewhere, narrow the target if
+        # we are matching an AssignmentExpr
+        unwrapped_subject = collapse_walrus(s.subject)
+        named_subject = self._make_named_statement_for_match(s, unwrapped_subject)
         with self.binder.frame_context(can_skip=False, fall_through=0):
             subject_type = get_proper_type(self.expr_checker.accept(s.subject))
 
@@ -5466,6 +5633,12 @@ def visit_match_stmt(self, s: MatchStmt) -> None:
                         pattern_map, else_map = conditional_types_to_typemaps(
                             named_subject, pattern_type.type, pattern_type.rest_type
                         )
+                        # Maybe the subject type can be inferred from constraints on
+                        # its attribute/item?
+                        if pattern_map and named_subject in pattern_map:
+                            pattern_map[unwrapped_subject] = pattern_map[named_subject]
+                        if else_map and named_subject in else_map:
+                            else_map[unwrapped_subject] = else_map[named_subject]
                         pattern_map = self.propagate_up_typemap_info(pattern_map)
                         else_map = self.propagate_up_typemap_info(else_map)
                         self.remove_capture_conflicts(pattern_type.captures, inferred_types)
@@ -5518,6 +5691,24 @@ def visit_match_stmt(self, s: MatchStmt) -> None:
             with self.binder.frame_context(can_skip=False, fall_through=2):
                 pass
 
+    def _make_named_statement_for_match(self, s: MatchStmt, subject: Expression) -> Expression:
+        """Construct a fake NameExpr for inference if a match clause is complex."""
+        if self.binder.can_put_directly(subject):
+            # Already named - we should infer type of it as given
+            return subject
+        elif s.subject_dummy is not None:
+            return s.subject_dummy
+        else:
+            # Create a dummy subject expression to handle cases where a match statement's subject
+            # is not a literal value. This lets us correctly narrow types and check exhaustivity
+            # This is hack!
+            name = self.new_unique_dummy_name("match")
+            v = Var(name)
+            named_subject = NameExpr(name)
+            named_subject.node = v
+            s.subject_dummy = named_subject
+            return named_subject
+
     def _get_recursive_sub_patterns_map(
         self, expr: Expression, typ: Type
     ) -> dict[Expression, Type]:
@@ -5556,6 +5747,8 @@ def infer_variable_types_from_type_maps(
                 previous_type, _, _ = self.check_lvalue(expr)
                 if previous_type is not None:
                     already_exists = True
+                    if isinstance(expr.node, Var) and expr.node.is_final:
+                        self.msg.cant_assign_to_final(expr.name, False, expr)
                     if self.check_subtype(
                         typ,
                         previous_type,
@@ -5680,6 +5873,10 @@ def _make_fake_typeinfo_and_full_name(
             format_type_distinctly(*base_classes, options=self.options, bare=True), "and"
         )
 
+        if not can_have_shared_disjoint_base(base_classes):
+            errors.append((pretty_names_list, "have distinct disjoint bases"))
+            return None
+
         new_errors = []
         for base in base_classes:
             if base.type.is_final:
@@ -6124,21 +6321,26 @@ def find_isinstance_check_helper(
                 attr = try_getting_str_literals(node.args[1], self.lookup_type(node.args[1]))
                 if literal(expr) == LITERAL_TYPE and attr and len(attr) == 1:
                     return self.hasattr_type_maps(expr, self.lookup_type(expr), attr[0])
-            elif isinstance(node.callee, RefExpr):
-                if node.callee.type_guard is not None or node.callee.type_is is not None:
+            else:
+                type_is, type_guard = None, None
+                called_type = self.lookup_type_or_none(node.callee)
+                if called_type is not None:
+                    called_type = get_proper_type(called_type)
+                    # TODO: there are some more cases in check_call() to handle.
+                    # If the callee is an instance, try to extract TypeGuard/TypeIs from its __call__ method.
+                    if isinstance(called_type, Instance):
+                        call = find_member("__call__", called_type, called_type, is_operator=True)
+                        if call is not None:
+                            called_type = get_proper_type(call)
+                    if isinstance(called_type, CallableType):
+                        type_is, type_guard = called_type.type_is, called_type.type_guard
+
+                # If the callee is a RefExpr, extract TypeGuard/TypeIs directly.
+                if isinstance(node.callee, RefExpr):
+                    type_is, type_guard = node.callee.type_is, node.callee.type_guard
+                if type_guard is not None or type_is is not None:
                     # TODO: Follow *args, **kwargs
                     if node.arg_kinds[0] != nodes.ARG_POS:
-                        # the first argument might be used as a kwarg
-                        called_type = get_proper_type(self.lookup_type(node.callee))
-
-                        # TODO: there are some more cases in check_call() to handle.
-                        if isinstance(called_type, Instance):
-                            call = find_member(
-                                "__call__", called_type, called_type, is_operator=True
-                            )
-                            if call is not None:
-                                called_type = get_proper_type(call)
-
                         # *assuming* the overloaded function is correct, there's a couple cases:
                         #  1) The first argument has different names, but is pos-only. We don't
                         #     care about this case, the argument must be passed positionally.
@@ -6151,9 +6353,7 @@ def find_isinstance_check_helper(
                                 # we want the idx-th variable to be narrowed
                                 expr = collapse_walrus(node.args[idx])
                             else:
-                                kind = (
-                                    "guard" if node.callee.type_guard is not None else "narrower"
-                                )
+                                kind = "guard" if type_guard is not None else "narrower"
                                 self.fail(
                                     message_registry.TYPE_GUARD_POS_ARG_REQUIRED.format(kind), node
                                 )
@@ -6164,16 +6364,17 @@ def find_isinstance_check_helper(
                         # considered "always right" (i.e. even if the types are not overlapping).
                         # Also note that a care must be taken to unwrap this back at read places
                         # where we use this to narrow down declared type.
-                        if node.callee.type_guard is not None:
-                            return {expr: TypeGuardedType(node.callee.type_guard)}, {}
+                        if type_guard is not None:
+                            return {expr: TypeGuardedType(type_guard)}, {}
                         else:
-                            assert node.callee.type_is is not None
+                            assert type_is is not None
                             return conditional_types_to_typemaps(
                                 expr,
                                 *self.conditional_types_with_intersection(
                                     self.lookup_type(expr),
-                                    [TypeRange(node.callee.type_is, is_upper_bound=False)],
+                                    [TypeRange(type_is, is_upper_bound=False)],
                                     expr,
+                                    consider_runtime_isinstance=False,
                                 ),
                             )
         elif isinstance(node, ComparisonExpr):
@@ -7258,13 +7459,36 @@ def named_type(self, name: str) -> Instance:
 
         For example, named_type('builtins.object') produces the 'object' type.
         """
+        if name == "builtins.str":
+            if self._str_type is None:
+                self._str_type = self._named_type(name)
+            return self._str_type
+        if name == "builtins.function":
+            if self._function_type is None:
+                self._function_type = self._named_type(name)
+            return self._function_type
+        if name == "builtins.int":
+            if self._int_type is None:
+                self._int_type = self._named_type(name)
+            return self._int_type
+        if name == "builtins.bool":
+            if self._bool_type is None:
+                self._bool_type = self._named_type(name)
+            return self._bool_type
+        if name == "builtins.object":
+            if self._object_type is None:
+                self._object_type = self._named_type(name)
+            return self._object_type
+        return self._named_type(name)
+
+    def _named_type(self, name: str) -> Instance:
         # Assume that the name refers to a type.
         sym = self.lookup_qualified(name)
         node = sym.node
         if isinstance(node, TypeAlias):
             assert isinstance(node.target, Instance)  # type: ignore[misc]
             node = node.target.type
-        assert isinstance(node, TypeInfo)
+        assert isinstance(node, TypeInfo), node
         any_type = AnyType(TypeOfAny.from_omitted_generics)
         return Instance(node, [any_type] * len(node.defn.type_vars))
 
@@ -7283,7 +7507,7 @@ def lookup_typeinfo(self, fullname: str) -> TypeInfo:
         # Assume that the name refers to a class.
         sym = self.lookup_qualified(fullname)
         node = sym.node
-        assert isinstance(node, TypeInfo)
+        assert isinstance(node, TypeInfo), node
         return node
 
     def type_type(self) -> Instance:
@@ -7317,18 +7541,6 @@ def lookup_type(self, node: Expression) -> Type:
     def store_types(self, d: dict[Expression, Type]) -> None:
         self._type_maps[-1].update(d)
 
-    @contextmanager
-    def local_type_map(self) -> Iterator[dict[Expression, Type]]:
-        """Store inferred types into a temporary type map (returned).
-
-        This can be used to perform type checking "experiments" without
-        affecting exported types (which are used by mypyc).
-        """
-        temp_type_map: dict[Expression, Type] = {}
-        self._type_maps.append(temp_type_map)
-        yield temp_type_map
-        self._type_maps.pop()
-
     def in_checked_function(self) -> bool:
         """Should we type-check the current function?
 
@@ -7601,11 +7813,19 @@ def conditional_types_with_intersection(
         type_ranges: list[TypeRange] | None,
         ctx: Context,
         default: None = None,
+        *,
+        consider_runtime_isinstance: bool = True,
     ) -> tuple[Type | None, Type | None]: ...
 
     @overload
     def conditional_types_with_intersection(
-        self, expr_type: Type, type_ranges: list[TypeRange] | None, ctx: Context, default: Type
+        self,
+        expr_type: Type,
+        type_ranges: list[TypeRange] | None,
+        ctx: Context,
+        default: Type,
+        *,
+        consider_runtime_isinstance: bool = True,
     ) -> tuple[Type, Type]: ...
 
     def conditional_types_with_intersection(
@@ -7614,8 +7834,15 @@ def conditional_types_with_intersection(
         type_ranges: list[TypeRange] | None,
         ctx: Context,
         default: Type | None = None,
+        *,
+        consider_runtime_isinstance: bool = True,
     ) -> tuple[Type | None, Type | None]:
-        initial_types = conditional_types(expr_type, type_ranges, default)
+        initial_types = conditional_types(
+            expr_type,
+            type_ranges,
+            default,
+            consider_runtime_isinstance=consider_runtime_isinstance,
+        )
         # For some reason, doing "yes_map, no_map = conditional_types_to_typemaps(...)"
         # doesn't work: mypyc will decide that 'yes_map' is of type None if we try.
         yes_type: Type | None = initial_types[0]
@@ -7859,6 +8086,9 @@ def has_valid_attribute(self, typ: Type, name: str) -> bool:
     def get_expression_type(self, node: Expression, type_context: Type | None = None) -> Type:
         return self.expr_checker.accept(node, type_context=type_context)
 
+    def is_defined_in_stub(self, typ: Instance, /) -> bool:
+        return self.modules[typ.type.module_name].is_stub
+
     def check_deprecated(self, node: Node | None, context: Context) -> None:
         """Warn if deprecated and not directly imported with a `from` statement."""
         if isinstance(node, Decorator):
@@ -7878,7 +8108,7 @@ def warn_deprecated(self, node: Node | None, context: Context) -> None:
             node = node.func
         if (
             isinstance(node, (FuncDef, OverloadedFuncDef, TypeInfo))
-            and ((deprecated := node.deprecated) is not None)
+            and (deprecated := node.deprecated) is not None
             and not self.is_typeshed_stub
             and not any(
                 node.fullname == p or node.fullname.startswith(f"{p}.")
@@ -7888,20 +8118,11 @@ def warn_deprecated(self, node: Node | None, context: Context) -> None:
             warn = self.msg.note if self.options.report_deprecated_as_note else self.msg.fail
             warn(deprecated, context, code=codes.DEPRECATED)
 
-    def warn_deprecated_overload_item(
-        self, node: Node | None, context: Context, *, target: Type, selftype: Type | None = None
-    ) -> None:
-        """Warn if the overload item corresponding to the given callable is deprecated."""
-        target = get_proper_type(target)
-        if isinstance(node, OverloadedFuncDef) and isinstance(target, CallableType):
-            for item in node.items:
-                if isinstance(item, Decorator) and isinstance(
-                    candidate := item.func.type, CallableType
-                ):
-                    if selftype is not None and not node.is_static:
-                        candidate = bind_self(candidate, selftype)
-                    if candidate == target:
-                        self.warn_deprecated(item.func, context)
+    def new_unique_dummy_name(self, namespace: str) -> str:
+        """Generate a name that is guaranteed to be unique for this TypeChecker instance."""
+        name = f"dummy-{namespace}-{self._unique_id}"
+        self._unique_id += 1
+        return name
 
     # leafs
 
@@ -7927,18 +8148,30 @@ def visit_type_var(self, t: TypeVarType) -> None:
 
 @overload
 def conditional_types(
-    current_type: Type, proposed_type_ranges: list[TypeRange] | None, default: None = None
+    current_type: Type,
+    proposed_type_ranges: list[TypeRange] | None,
+    default: None = None,
+    *,
+    consider_runtime_isinstance: bool = True,
 ) -> tuple[Type | None, Type | None]: ...
 
 
 @overload
 def conditional_types(
-    current_type: Type, proposed_type_ranges: list[TypeRange] | None, default: Type
+    current_type: Type,
+    proposed_type_ranges: list[TypeRange] | None,
+    default: Type,
+    *,
+    consider_runtime_isinstance: bool = True,
 ) -> tuple[Type, Type]: ...
 
 
 def conditional_types(
-    current_type: Type, proposed_type_ranges: list[TypeRange] | None, default: Type | None = None
+    current_type: Type,
+    proposed_type_ranges: list[TypeRange] | None,
+    default: Type | None = None,
+    *,
+    consider_runtime_isinstance: bool = True,
 ) -> tuple[Type | None, Type | None]:
     """Takes in the current type and a proposed type of an expression.
 
@@ -7980,7 +8213,11 @@ def conditional_types(
                     if not type_range.is_upper_bound
                 ]
             )
-            remaining_type = restrict_subtype_away(current_type, proposed_precise_type)
+            remaining_type = restrict_subtype_away(
+                current_type,
+                proposed_precise_type,
+                consider_runtime_isinstance=consider_runtime_isinstance,
+            )
             return proposed_type, remaining_type
     else:
         # An isinstance check, but we don't understand the type
@@ -8531,15 +8768,25 @@ def visit_type_alias_type(self, t: TypeAliasType) -> Type:
         return t.copy_modified(args=[a.accept(self) for a in t.args])
 
 
-def is_node_static(node: Node | None) -> bool | None:
-    """Find out if a node describes a static function method."""
+def is_classmethod_node(node: SymbolNode | None) -> bool | None:
+    """Find out if a node describes a classmethod."""
+    if isinstance(node, Decorator):
+        node = node.func
+    if isinstance(node, FuncDef):
+        return node.is_class
+    if isinstance(node, Var):
+        return node.is_classmethod
+    return None
+
 
+def is_node_static(node: SymbolNode | None) -> bool | None:
+    """Find out if a node describes a static function method."""
+    if isinstance(node, Decorator):
+        node = node.func
     if isinstance(node, FuncDef):
         return node.is_static
-
     if isinstance(node, Var):
         return node.is_staticmethod
-
     return None
 
 
@@ -8786,6 +9033,8 @@ def is_static(func: FuncBase | Decorator) -> bool:
 
 
 def is_property(defn: SymbolNode) -> bool:
+    if isinstance(defn, FuncDef):
+        return defn.is_property
     if isinstance(defn, Decorator):
         return defn.func.is_property
     if isinstance(defn, OverloadedFuncDef):
diff --git a/mypy/checker_shared.py b/mypy/checker_shared.py
index 2ab4548edfaf..0014d2c6fc88 100644
--- a/mypy/checker_shared.py
+++ b/mypy/checker_shared.py
@@ -137,6 +137,7 @@ class TypeCheckerSharedApi(CheckerPluginInterface):
     module_refs: set[str]
     scope: CheckerScope
     checking_missing_await: bool
+    allow_constructor_cache: bool
 
     @property
     @abstractmethod
@@ -252,12 +253,6 @@ def check_deprecated(self, node: Node | None, context: Context) -> None:
     def warn_deprecated(self, node: Node | None, context: Context) -> None:
         raise NotImplementedError
 
-    @abstractmethod
-    def warn_deprecated_overload_item(
-        self, node: Node | None, context: Context, *, target: Type, selftype: Type | None = None
-    ) -> None:
-        raise NotImplementedError
-
     @abstractmethod
     def type_is_iterable(self, type: Type) -> bool:
         raise NotImplementedError
@@ -277,6 +272,14 @@ def checking_await_set(self) -> Iterator[None]:
     def get_precise_awaitable_type(self, typ: Type, local_errors: ErrorWatcher) -> Type | None:
         raise NotImplementedError
 
+    @abstractmethod
+    def add_any_attribute_to_type(self, typ: Type, name: str) -> Type:
+        raise NotImplementedError
+
+    @abstractmethod
+    def is_defined_in_stub(self, typ: Instance, /) -> bool:
+        raise NotImplementedError
+
 
 class CheckerScope:
     # We keep two stacks combined, to maintain the relative order
@@ -334,6 +337,10 @@ def current_self_type(self) -> Instance | TupleType | None:
                 return fill_typevars(item)
         return None
 
+    def is_top_level(self) -> bool:
+        """Is current scope top-level (no classes or functions)?"""
+        return len(self.stack) == 1
+
     @contextmanager
     def push_function(self, item: FuncItem) -> Iterator[None]:
         self.stack.append(item)
diff --git a/mypy/checkexpr.py b/mypy/checkexpr.py
index edc3ac70fa54..250decd7567e 100644
--- a/mypy/checkexpr.py
+++ b/mypy/checkexpr.py
@@ -19,7 +19,7 @@
 from mypy.checkmember import analyze_member_access, has_operator
 from mypy.checkstrformat import StringFormatterChecker
 from mypy.erasetype import erase_type, remove_instance_last_known_values, replace_meta_vars
-from mypy.errors import ErrorWatcher, report_internal_error
+from mypy.errors import ErrorInfo, ErrorWatcher, report_internal_error
 from mypy.expandtype import (
     expand_type,
     expand_type_by_instance,
@@ -129,7 +129,6 @@
     validate_instance,
 )
 from mypy.typeops import (
-    bind_self,
     callable_type,
     custom_special_method,
     erase_to_union_or_bound,
@@ -249,12 +248,11 @@ def allow_fast_container_literal(t: Type) -> bool:
     )
 
 
-def extract_refexpr_names(expr: RefExpr) -> set[str]:
+def extract_refexpr_names(expr: RefExpr, output: set[str]) -> None:
     """Recursively extracts all module references from a reference expression.
 
     Note that currently, the only two subclasses of RefExpr are NameExpr and
     MemberExpr."""
-    output: set[str] = set()
     while isinstance(expr.node, MypyFile) or expr.fullname:
         if isinstance(expr.node, MypyFile) and expr.fullname:
             # If it's None, something's wrong (perhaps due to an
@@ -278,7 +276,6 @@ def extract_refexpr_names(expr: RefExpr) -> set[str]:
                 break
         else:
             raise AssertionError(f"Unknown RefExpr subclass: {type(expr)}")
-    return output
 
 
 class Finished(Exception):
@@ -318,6 +315,8 @@ class ExpressionChecker(ExpressionVisitor[Type], ExpressionCheckerSharedApi):
     strfrm_checker: StringFormatterChecker
     plugin: Plugin
 
+    _arg_infer_context_cache: ArgumentInferContext | None
+
     def __init__(
         self,
         chk: mypy.checker.TypeChecker,
@@ -352,15 +351,26 @@ def __init__(
         self.is_callee = False
         type_state.infer_polymorphic = not self.chk.options.old_type_inference
 
+        self._arg_infer_context_cache = None
+        self.expr_cache: dict[
+            tuple[Expression, Type | None],
+            tuple[int, Type, list[ErrorInfo], dict[Expression, Type]],
+        ] = {}
+        self.in_lambda_expr = False
+
+        self._literal_true: Instance | None = None
+        self._literal_false: Instance | None = None
+
     def reset(self) -> None:
         self.resolved_type = {}
+        self.expr_cache.clear()
 
     def visit_name_expr(self, e: NameExpr) -> Type:
         """Type check a name expression.
 
         It can be of any kind: local, member or global.
         """
-        self.chk.module_refs.update(extract_refexpr_names(e))
+        extract_refexpr_names(e, self.chk.module_refs)
         result = self.analyze_ref_expr(e)
         narrowed = self.narrow_type_from_binder(e, result)
         self.chk.check_deprecated(e.node, e)
@@ -570,7 +580,10 @@ def visit_call_expr_inner(self, e: CallExpr, allow_none_return: bool = False) ->
                     and not node.node.no_args
                     and not (
                         isinstance(union_target := get_proper_type(node.node.target), UnionType)
-                        and union_target.uses_pep604_syntax
+                        and (
+                            union_target.uses_pep604_syntax
+                            or self.chk.options.python_version >= (3, 10)
+                        )
                     )
                 ):
                     self.msg.type_arguments_not_allowed(e)
@@ -1063,7 +1076,7 @@ def check_typeddict_call_with_kwargs(
 
         # We don't show any errors, just infer types in a generic TypedDict type,
         # a custom error message will be given below, if there are errors.
-        with self.msg.filter_errors(), self.chk.local_type_map():
+        with self.msg.filter_errors(), self.chk.local_type_map:
             orig_ret_type, _ = self.check_callable_call(
                 infer_callee,
                 # We use first expression for each key to infer type variables of a generic
@@ -1428,7 +1441,7 @@ def is_generic_decorator_overload_call(
             return None
         if not isinstance(get_proper_type(callee_type.ret_type), CallableType):
             return None
-        with self.chk.local_type_map():
+        with self.chk.local_type_map:
             with self.msg.filter_errors():
                 arg_type = get_proper_type(self.accept(args[0], type_context=None))
         if isinstance(arg_type, Overloaded):
@@ -1507,15 +1520,6 @@ def check_call_expr_with_callee_type(
             object_type=object_type,
         )
         proper_callee = get_proper_type(callee_type)
-        if isinstance(e.callee, (NameExpr, MemberExpr)):
-            node = e.callee.node
-            if node is None and member is not None and isinstance(object_type, Instance):
-                if (symbol := object_type.type.get(member)) is not None:
-                    node = symbol.node
-            self.chk.check_deprecated(node, e)
-            self.chk.warn_deprecated_overload_item(
-                node, e, target=callee_type, selftype=object_type
-            )
         if isinstance(e.callee, RefExpr) and isinstance(proper_callee, CallableType):
             # Cache it for find_isinstance_check()
             if proper_callee.type_guard is not None:
@@ -1667,6 +1671,10 @@ def check_call(
                 object_type,
                 original_type=callee,
             )
+        elif isinstance(callee, UninhabitedType):
+            ret = UninhabitedType()
+            ret.ambiguous = callee.ambiguous
+            return callee, ret
         else:
             return self.msg.not_callable(callee, context), AnyType(TypeOfAny.from_error)
 
@@ -1747,14 +1755,6 @@ def check_callable_call(
                         return AnyType(TypeOfAny.from_error), callee
                     seen_unpack = True
 
-        formal_to_actual = map_actuals_to_formals(
-            arg_kinds,
-            arg_names,
-            callee.arg_kinds,
-            callee.arg_names,
-            lambda i: self.accept(args[i]),
-        )
-
         # This is tricky: return type may contain its own type variables, like in
         # def [S] (S) -> def [T] (T) -> tuple[S, T], so we need to update their ids
         # to avoid possible id clashes if this call itself appears in a generic
@@ -1765,27 +1765,29 @@ def check_callable_call(
             freeze_all_type_vars(fresh_ret_type)
             callee = callee.copy_modified(ret_type=fresh_ret_type)
 
+        if callee.is_generic():
+            callee = freshen_function_type_vars(callee)
+            callee = self.infer_function_type_arguments_using_context(callee, context)
+
+        formal_to_actual = map_actuals_to_formals(
+            arg_kinds,
+            arg_names,
+            callee.arg_kinds,
+            callee.arg_names,
+            lambda i: self.accept(args[i]),
+        )
+
         if callee.is_generic():
             need_refresh = any(
                 isinstance(v, (ParamSpecType, TypeVarTupleType)) for v in callee.variables
             )
-            callee = freshen_function_type_vars(callee)
-            callee = self.infer_function_type_arguments_using_context(callee, context)
-            if need_refresh:
-                # Argument kinds etc. may have changed due to
-                # ParamSpec or TypeVarTuple variables being replaced with an arbitrary
-                # number of arguments; recalculate actual-to-formal map
-                formal_to_actual = map_actuals_to_formals(
-                    arg_kinds,
-                    arg_names,
-                    callee.arg_kinds,
-                    callee.arg_names,
-                    lambda i: self.accept(args[i]),
-                )
             callee = self.infer_function_type_arguments(
                 callee, args, arg_kinds, arg_names, formal_to_actual, need_refresh, context
             )
             if need_refresh:
+                # Argument kinds etc. may have changed due to
+                # ParamSpec or TypeVarTuple variables being replaced with an arbitrary
+                # number of arguments; recalculate actual-to-formal map
                 formal_to_actual = map_actuals_to_formals(
                     arg_kinds,
                     arg_names,
@@ -2250,6 +2252,11 @@ def infer_function_type_arguments_pass2(
             if isinstance(arg, (NoneType, UninhabitedType)) or has_erased_component(arg):
                 inferred_args[i] = None
         callee_type = self.apply_generic_arguments(callee_type, inferred_args, context)
+
+        if not callee_type.is_generic():
+            # Fast path, second pass can't give new information.
+            return callee_type, []
+
         if need_refresh:
             formal_to_actual = map_actuals_to_formals(
                 arg_kinds,
@@ -2277,9 +2284,11 @@ def infer_function_type_arguments_pass2(
         return callee_type, inferred_args
 
     def argument_infer_context(self) -> ArgumentInferContext:
-        return ArgumentInferContext(
-            self.chk.named_type("typing.Mapping"), self.chk.named_type("typing.Iterable")
-        )
+        if self._arg_infer_context_cache is None:
+            self._arg_infer_context_cache = ArgumentInferContext(
+                self.chk.named_type("typing.Mapping"), self.chk.named_type("typing.Iterable")
+            )
+        return self._arg_infer_context_cache
 
     def get_arg_infer_passes(
         self,
@@ -2338,10 +2347,10 @@ def apply_inferred_arguments(
         # Report error if some of the variables could not be solved. In that
         # case assume that all variables have type Any to avoid extra
         # bogus error messages.
-        for i, inferred_type in enumerate(inferred_args):
+        for inferred_type, tv in zip(inferred_args, callee_type.variables):
             if not inferred_type or has_erased_component(inferred_type):
                 # Could not infer a non-trivial type for a type variable.
-                self.msg.could_not_infer_type_arguments(callee_type, i + 1, context)
+                self.msg.could_not_infer_type_arguments(callee_type, tv, context)
                 inferred_args = [AnyType(TypeOfAny.from_error)] * len(inferred_args)
         # Apply the inferred types to the function type. In this case the
         # return type must be CallableType, since we give the right number of type
@@ -2678,9 +2687,12 @@ def check_arg(
                 context=context,
                 outer_context=outer_context,
             )
-            self.msg.incompatible_argument_note(
-                original_caller_type, callee_type, context, parent_error=error
-            )
+            if not caller_kind.is_star():
+                # For *args and **kwargs this note would be incorrect - we're comparing
+                # iterable/mapping type with union of relevant arg types.
+                self.msg.incompatible_argument_note(
+                    original_caller_type, callee_type, context, parent_error=error
+                )
             if not self.msg.prefer_simple_messages():
                 self.chk.check_possible_missing_await(
                     caller_type, callee_type, context, error.code
@@ -2711,6 +2723,7 @@ def check_overload_call(
         #         for example, when we have a fallback alternative that accepts an unrestricted
         #         typevar. See https://github.com/python/mypy/issues/4063 for related discussion.
         erased_targets: list[CallableType] | None = None
+        inferred_types: list[Type] | None = None
         unioned_result: tuple[Type, Type] | None = None
 
         # Determine whether we need to encourage union math. This should be generally safe,
@@ -2738,13 +2751,14 @@ def check_overload_call(
                 # Record if we succeeded. Next we need to see if maybe normal procedure
                 # gives a narrower type.
                 if unioned_return:
-                    returns, inferred_types = zip(*unioned_return)
+                    returns = [u[0] for u in unioned_return]
+                    inferred_types = [u[1] for u in unioned_return]
                     # Note that we use `combine_function_signatures` instead of just returning
                     # a union of inferred callables because for example a call
                     # Union[int -> int, str -> str](Union[int, str]) is invalid and
                     # we don't want to introduce internal inconsistencies.
                     unioned_result = (
-                        make_simplified_union(list(returns), context.line, context.column),
+                        make_simplified_union(returns, context.line, context.column),
                         self.combine_function_signatures(get_proper_types(inferred_types)),
                     )
 
@@ -2759,7 +2773,7 @@ def check_overload_call(
             object_type,
             context,
         )
-        # If any of checks succeed, stop early.
+        # If any of checks succeed, perform deprecation tests and stop early.
         if inferred_result is not None and unioned_result is not None:
             # Both unioned and direct checks succeeded, choose the more precise type.
             if (
@@ -2767,11 +2781,18 @@ def check_overload_call(
                 and not isinstance(get_proper_type(inferred_result[0]), AnyType)
                 and not none_type_var_overlap
             ):
-                return inferred_result
-            return unioned_result
-        elif unioned_result is not None:
+                unioned_result = None
+            else:
+                inferred_result = None
+        if unioned_result is not None:
+            if inferred_types is not None:
+                for inferred_type in inferred_types:
+                    if isinstance(c := get_proper_type(inferred_type), CallableType):
+                        self.chk.warn_deprecated(c.definition, context)
             return unioned_result
-        elif inferred_result is not None:
+        if inferred_result is not None:
+            if isinstance(c := get_proper_type(inferred_result[1]), CallableType):
+                self.chk.warn_deprecated(c.definition, context)
             return inferred_result
 
         # Step 4: Failure. At this point, we know there is no match. We fall back to trying
@@ -2909,7 +2930,7 @@ def infer_overload_return_type(
         for typ in plausible_targets:
             assert self.msg is self.chk.msg
             with self.msg.filter_errors() as w:
-                with self.chk.local_type_map() as m:
+                with self.chk.local_type_map as m:
                     ret_type, infer_type = self.check_call(
                         callee=typ,
                         args=args,
@@ -3322,7 +3343,7 @@ def check_union_call(
 
     def visit_member_expr(self, e: MemberExpr, is_lvalue: bool = False) -> Type:
         """Visit member expression (of form e.id)."""
-        self.chk.module_refs.update(extract_refexpr_names(e))
+        extract_refexpr_names(e, self.chk.module_refs)
         result = self.analyze_ordinary_member_access(e, is_lvalue)
         narrowed = self.narrow_type_from_binder(e, result)
         self.chk.warn_deprecated(e.node, e)
@@ -3413,11 +3434,19 @@ def infer_literal_expr_type(self, value: LiteralValue, fallback_name: str) -> Ty
         if self.is_literal_context():
             return LiteralType(value=value, fallback=typ)
         else:
-            return typ.copy_modified(
-                last_known_value=LiteralType(
-                    value=value, fallback=typ, line=typ.line, column=typ.column
-                )
-            )
+            if value is True:
+                if self._literal_true is None:
+                    self._literal_true = typ.copy_modified(
+                        last_known_value=LiteralType(value=value, fallback=typ)
+                    )
+                return self._literal_true
+            if value is False:
+                if self._literal_false is None:
+                    self._literal_false = typ.copy_modified(
+                        last_known_value=LiteralType(value=value, fallback=typ)
+                    )
+                return self._literal_false
+            return typ.copy_modified(last_known_value=LiteralType(value=value, fallback=typ))
 
     def concat_tuples(self, left: TupleType, right: TupleType) -> TupleType:
         """Concatenate two fixed length tuples."""
@@ -3456,7 +3485,7 @@ def visit_op_expr(self, e: OpExpr) -> Type:
             # It's actually a type expression X | Y.
             return self.accept(e.analyzed)
         if e.op == "and" or e.op == "or":
-            return self.check_boolean_op(e, e)
+            return self.check_boolean_op(e)
         if e.op == "*" and isinstance(e.left, ListExpr):
             # Expressions of form [...] * e get special type inference.
             return self.check_list_multiply(e)
@@ -3690,7 +3719,7 @@ def visit_comparison_expr(self, e: ComparisonExpr) -> Type:
             elif operator == "is" or operator == "is not":
                 right_type = self.accept(right)  # validate the right operand
                 sub_result = self.bool_type()
-                if self.dangerous_comparison(left_type, right_type):
+                if self.dangerous_comparison(left_type, right_type, identity_check=True):
                     # Show the most specific literal types possible
                     left_type = try_getting_literal(left_type)
                     right_type = try_getting_literal(right_type)
@@ -3732,6 +3761,7 @@ def dangerous_comparison(
         original_container: Type | None = None,
         seen_types: set[tuple[Type, Type]] | None = None,
         prefer_literal: bool = True,
+        identity_check: bool = False,
     ) -> bool:
         """Check for dangerous non-overlapping comparisons like 42 == 'no'.
 
@@ -3759,10 +3789,12 @@ def dangerous_comparison(
 
         left, right = get_proper_types((left, right))
 
-        # We suppress the error if there is a custom __eq__() method on either
-        # side. User defined (or even standard library) classes can define this
+        # We suppress the error for equality and container checks if there is a custom __eq__()
+        # method on either side. User defined (or even standard library) classes can define this
         # to return True for comparisons between non-overlapping types.
-        if custom_special_method(left, "__eq__") or custom_special_method(right, "__eq__"):
+        if (
+            custom_special_method(left, "__eq__") or custom_special_method(right, "__eq__")
+        ) and not identity_check:
             return False
 
         if prefer_literal:
@@ -3786,7 +3818,10 @@ def dangerous_comparison(
             #
             # TODO: find a way of disabling the check only for types resulted from the expansion.
             return False
-        if isinstance(left, NoneType) or isinstance(right, NoneType):
+        if self.chk.options.strict_equality_for_none:
+            if isinstance(left, NoneType) and isinstance(right, NoneType):
+                return False
+        elif isinstance(left, NoneType) or isinstance(right, NoneType):
             return False
         if isinstance(left, UnionType) and isinstance(right, UnionType):
             left = remove_optional(left)
@@ -4085,16 +4120,6 @@ def lookup_definer(typ: Instance, attr_name: str) -> str | None:
                 errors.append(local_errors.filtered_errors())
                 results.append(result)
             else:
-                if isinstance(obj, Instance) and isinstance(
-                    defn := obj.type.get_method(name), OverloadedFuncDef
-                ):
-                    for item in defn.items:
-                        if (
-                            isinstance(item, Decorator)
-                            and isinstance(typ := item.func.type, CallableType)
-                            and bind_self(typ) == result[1]
-                        ):
-                            self.chk.check_deprecated(item.func, context)
                 return result
 
         # We finish invoking above operators and no early return happens. Therefore,
@@ -4243,20 +4268,18 @@ def check_op(
                 context=context,
             )
 
-    def check_boolean_op(self, e: OpExpr, context: Context) -> Type:
+    def check_boolean_op(self, e: OpExpr) -> Type:
         """Type check a boolean operation ('and' or 'or')."""
 
         # A boolean operation can evaluate to either of the operands.
 
-        # We use the current type context to guide the type inference of of
+        # We use the current type context to guide the type inference of
         # the left operand. We also use the left operand type to guide the type
         # inference of the right operand so that expressions such as
         # '[1] or []' are inferred correctly.
         ctx = self.type_context[-1]
         left_type = self.accept(e.left, ctx)
-        expanded_left_type = try_expanding_sum_type_to_union(
-            self.accept(e.left, ctx), "builtins.bool"
-        )
+        expanded_left_type = try_expanding_sum_type_to_union(left_type, "builtins.bool")
 
         assert e.op in ("and", "or")  # Checked by visit_op_expr
 
@@ -4288,7 +4311,9 @@ def check_boolean_op(self, e: OpExpr, context: Context) -> Type:
         ):
             self.msg.unreachable_right_operand(e.op, e.right)
 
-        right_type = self.analyze_cond_branch(right_map, e.right, expanded_left_type)
+        right_type = self.analyze_cond_branch(
+            right_map, e.right, self._combined_context(expanded_left_type)
+        )
 
         if left_map is None and right_map is None:
             return UninhabitedType()
@@ -5051,31 +5076,56 @@ def fast_container_type(
         module-level constant definitions.
 
         Limitations:
+
          - no active type context
+         - at least one item
          - no star expressions
-         - the joined type of all entries must be an Instance or Tuple type
+         - not after deferral
+         - either exactly one distinct type inside,
+           or the joined type of all entries is an Instance or Tuple type,
         """
         ctx = self.type_context[-1]
-        if ctx:
+        if ctx or not e.items:
+            return None
+        if self.chk.current_node_deferred:
+            # Guarantees that all items will be Any, we'll reject it anyway.
             return None
         rt = self.resolved_type.get(e, None)
         if rt is not None:
             return rt if isinstance(rt, Instance) else None
         values: list[Type] = []
+        # Preserve join order while avoiding O(n) lookups at every iteration
+        values_set: set[Type] = set()
         for item in e.items:
             if isinstance(item, StarExpr):
                 # fallback to slow path
                 self.resolved_type[e] = NoneType()
                 return None
-            values.append(self.accept(item))
-        vt = join.join_type_list(values)
-        if not allow_fast_container_literal(vt):
+
+            typ = self.accept(item)
+            if typ not in values_set:
+                values.append(typ)
+                values_set.add(typ)
+
+        vt = self._first_or_join_fast_item(values)
+        if vt is None:
             self.resolved_type[e] = NoneType()
             return None
         ct = self.chk.named_generic_type(container_fullname, [vt])
         self.resolved_type[e] = ct
         return ct
 
+    def _first_or_join_fast_item(self, items: list[Type]) -> Type | None:
+        if len(items) == 1 and not self.chk.current_node_deferred:
+            return items[0]
+        typ = join.join_type_list(items)
+        if not allow_fast_container_literal(typ):
+            # TODO: This is overly strict, many other types can be joined safely here.
+            # However, our join implementation isn't bug-free, and some joins may produce
+            # undesired `Any`s or even more surprising results.
+            return None
+        return typ
+
     def check_lst_expr(self, e: ListExpr | SetExpr | TupleExpr, fullname: str, tag: str) -> Type:
         # fast path
         t = self.fast_container_type(e, fullname)
@@ -5236,18 +5286,30 @@ def fast_dict_type(self, e: DictExpr) -> Type | None:
         module-level constant definitions.
 
         Limitations:
+
          - no active type context
+         - at least one item
          - only supported star expressions are other dict instances
-         - the joined types of all keys and values must be Instance or Tuple types
+         - either exactly one distinct type (keys and values separately) inside,
+           or the joined type of all entries is an Instance or Tuple type
         """
         ctx = self.type_context[-1]
-        if ctx:
+        if ctx or not e.items:
+            return None
+
+        if self.chk.current_node_deferred:
+            # Guarantees that all items will be Any, we'll reject it anyway.
             return None
+
         rt = self.resolved_type.get(e, None)
         if rt is not None:
             return rt if isinstance(rt, Instance) else None
+
         keys: list[Type] = []
         values: list[Type] = []
+        # Preserve join order while avoiding O(n) lookups at every iteration
+        keys_set: set[Type] = set()
+        values_set: set[Type] = set()
         stargs: tuple[Type, Type] | None = None
         for key, value in e.items:
             if key is None:
@@ -5262,13 +5324,25 @@ def fast_dict_type(self, e: DictExpr) -> Type | None:
                     self.resolved_type[e] = NoneType()
                     return None
             else:
-                keys.append(self.accept(key))
-                values.append(self.accept(value))
-        kt = join.join_type_list(keys)
-        vt = join.join_type_list(values)
-        if not (allow_fast_container_literal(kt) and allow_fast_container_literal(vt)):
+                key_t = self.accept(key)
+                if key_t not in keys_set:
+                    keys.append(key_t)
+                    keys_set.add(key_t)
+                value_t = self.accept(value)
+                if value_t not in values_set:
+                    values.append(value_t)
+                    values_set.add(value_t)
+
+        kt = self._first_or_join_fast_item(keys)
+        if kt is None:
             self.resolved_type[e] = NoneType()
             return None
+
+        vt = self._first_or_join_fast_item(values)
+        if vt is None:
+            self.resolved_type[e] = NoneType()
+            return None
+
         if stargs and (stargs[0] != kt or stargs[1] != vt):
             self.resolved_type[e] = NoneType()
             return None
@@ -5296,20 +5370,21 @@ def visit_dict_expr(self, e: DictExpr) -> Type:
         # an error, but returns the TypedDict type that matches the literal it found
         # that would cause a second error when that TypedDict type is returned upstream
         # to avoid the second error, we always return TypedDict type that was requested
-        typeddict_contexts = self.find_typeddict_context(self.type_context[-1], e)
+        typeddict_contexts, exhaustive = self.find_typeddict_context(self.type_context[-1], e)
         if typeddict_contexts:
-            if len(typeddict_contexts) == 1:
+            if len(typeddict_contexts) == 1 and exhaustive:
                 return self.check_typeddict_literal_in_context(e, typeddict_contexts[0])
             # Multiple items union, check if at least one of them matches cleanly.
             for typeddict_context in typeddict_contexts:
-                with self.msg.filter_errors() as err, self.chk.local_type_map() as tmap:
+                with self.msg.filter_errors() as err, self.chk.local_type_map as tmap:
                     ret_type = self.check_typeddict_literal_in_context(e, typeddict_context)
                 if err.has_new_errors():
                     continue
                 self.chk.store_types(tmap)
                 return ret_type
             # No item matched without an error, so we can't unambiguously choose the item.
-            self.msg.typeddict_context_ambiguous(typeddict_contexts, e)
+            if exhaustive:
+                self.msg.typeddict_context_ambiguous(typeddict_contexts, e)
 
         # fast path attempt
         dt = self.fast_dict_type(e)
@@ -5371,25 +5446,34 @@ def visit_dict_expr(self, e: DictExpr) -> Type:
 
     def find_typeddict_context(
         self, context: Type | None, dict_expr: DictExpr
-    ) -> list[TypedDictType]:
+    ) -> tuple[list[TypedDictType], bool]:
+        """Extract `TypedDict` members of the enclosing context.
+
+        Returns:
+            a 2-tuple, (found_candidates, is_exhaustive)
+        """
         context = get_proper_type(context)
         if isinstance(context, TypedDictType):
-            return [context]
+            return [context], True
         elif isinstance(context, UnionType):
             items = []
+            exhaustive = True
             for item in context.items:
-                item_contexts = self.find_typeddict_context(item, dict_expr)
+                item_contexts, item_exhaustive = self.find_typeddict_context(item, dict_expr)
                 for item_context in item_contexts:
                     if self.match_typeddict_call_with_dict(
                         item_context, dict_expr.items, dict_expr
                     ):
                         items.append(item_context)
-            return items
+                exhaustive = exhaustive and item_exhaustive
+            return items, exhaustive
         # No TypedDict type in context.
-        return []
+        return [], False
 
     def visit_lambda_expr(self, e: LambdaExpr) -> Type:
         """Type check lambda expression."""
+        old_in_lambda = self.in_lambda_expr
+        self.in_lambda_expr = True
         self.chk.check_default_args(e, body_is_trivial=False)
         inferred_type, type_override = self.infer_lambda_type_using_context(e)
         if not inferred_type:
@@ -5410,6 +5494,7 @@ def visit_lambda_expr(self, e: LambdaExpr) -> Type:
                 ret_type = self.accept(e.expr(), allow_none_return=True)
             fallback = self.named_type("builtins.function")
             self.chk.return_types.pop()
+            self.in_lambda_expr = old_in_lambda
             return callable_type(e, fallback, ret_type)
         else:
             # Type context available.
@@ -5422,6 +5507,7 @@ def visit_lambda_expr(self, e: LambdaExpr) -> Type:
                     self.accept(e.expr(), allow_none_return=True)
             ret_type = self.chk.lookup_type(e.expr())
             self.chk.return_types.pop()
+            self.in_lambda_expr = old_in_lambda
             return replace_callable_return_type(inferred_type, ret_type)
 
     def infer_lambda_type_using_context(
@@ -5919,6 +6005,20 @@ def analyze_cond_branch(
             self.chk.push_type_map(map)
             return self.accept(node, type_context=context, allow_none_return=allow_none_return)
 
+    def _combined_context(self, ty: Type | None) -> Type | None:
+        ctx_items = []
+        if ty is not None:
+            if has_any_type(ty):
+                # HACK: Any should be contagious, `dict[str, Any] or <x>` should still
+                # infer Any in x.
+                return ty
+            ctx_items.append(ty)
+        if self.type_context and self.type_context[-1] is not None:
+            ctx_items.append(self.type_context[-1])
+        if ctx_items:
+            return make_simplified_union(ctx_items)
+        return None
+
     #
     # Helpers
     #
@@ -5956,6 +6056,26 @@ def accept(
                 typ = self.visit_conditional_expr(node, allow_none_return=True)
             elif allow_none_return and isinstance(node, AwaitExpr):
                 typ = self.visit_await_expr(node, allow_none_return=True)
+            # Deeply nested generic calls can deteriorate performance dramatically.
+            # Although in most cases caching makes little difference, in worst case
+            # it avoids exponential complexity.
+            # We cannot use cache inside lambdas, because they skip immediate type
+            # context, and use enclosing one, see infer_lambda_type_using_context().
+            # TODO: consider using cache for more expression kinds.
+            elif (
+                isinstance(node, (CallExpr, ListExpr, TupleExpr, DictExpr, OpExpr))
+                and not (self.in_lambda_expr or self.chk.current_node_deferred)
+                and not self.chk.options.disable_expression_cache
+            ):
+                if (node, type_context) in self.expr_cache:
+                    binder_version, typ, messages, type_map = self.expr_cache[(node, type_context)]
+                    if binder_version == self.chk.binder.version:
+                        self.chk.store_types(type_map)
+                        self.msg.add_errors(messages)
+                    else:
+                        typ = self.accept_maybe_cache(node, type_context=type_context)
+                else:
+                    typ = self.accept_maybe_cache(node, type_context=type_context)
             else:
                 typ = node.accept(self)
         except Exception as err:
@@ -5986,6 +6106,18 @@ def accept(
             self.in_expression = False
         return result
 
+    def accept_maybe_cache(self, node: Expression, type_context: Type | None = None) -> Type:
+        binder_version = self.chk.binder.version
+        with self.msg.filter_errors(filter_errors=True, save_filtered_errors=True) as msg:
+            with self.chk.local_type_map as type_map:
+                typ = node.accept(self)
+        messages = msg.filtered_errors()
+        if binder_version == self.chk.binder.version and not self.chk.current_node_deferred:
+            self.expr_cache[(node, type_context)] = (binder_version, typ, messages, type_map)
+        self.chk.store_types(type_map)
+        self.msg.add_errors(messages)
+        return typ
+
     def named_type(self, name: str) -> Instance:
         """Return an instance type with type given by the name and no type
         arguments. Alias for TypeChecker.named_type.
diff --git a/mypy/checkmember.py b/mypy/checkmember.py
index 502251b3960c..e7de1b7a304f 100644
--- a/mypy/checkmember.py
+++ b/mypy/checkmember.py
@@ -5,7 +5,7 @@
 from collections.abc import Sequence
 from typing import Callable, TypeVar, cast
 
-from mypy import message_registry, state, subtypes
+from mypy import message_registry, state
 from mypy.checker_shared import TypeCheckerSharedApi
 from mypy.erasetype import erase_typevars
 from mypy.expandtype import (
@@ -14,6 +14,7 @@
     freshen_all_functions_type_vars,
 )
 from mypy.maptype import map_instance_to_supertype
+from mypy.meet import is_overlapping_types
 from mypy.messages import MessageBuilder
 from mypy.nodes import (
     ARG_POS,
@@ -39,13 +40,13 @@
     is_final_node,
 )
 from mypy.plugin import AttributeContext
+from mypy.subtypes import is_subtype
 from mypy.typeops import (
     bind_self,
     erase_to_bound,
     freeze_all_type_vars,
     function_type,
     get_all_type_vars,
-    get_type_vars,
     make_simplified_union,
     supported_self_type,
     tuple_fallback,
@@ -70,6 +71,7 @@
     TypeVarLikeType,
     TypeVarTupleType,
     TypeVarType,
+    UninhabitedType,
     UnionType,
     get_proper_type,
 )
@@ -269,6 +271,10 @@ def _analyze_member_access(
         if not mx.suppress_errors:
             mx.msg.deleted_as_rvalue(typ, mx.context)
         return AnyType(TypeOfAny.from_error)
+    elif isinstance(typ, UninhabitedType):
+        attr_type = UninhabitedType()
+        attr_type.ambiguous = typ.ambiguous
+        return attr_type
     return report_missing_attribute(mx.original_type, typ, name, mx)
 
 
@@ -371,8 +377,6 @@ def analyze_instance_member_access(
                     signature, mx.self_type, method.is_class, mx.context, name, mx.msg
                 )
                 signature = bind_self(signature, mx.self_type, is_classmethod=method.is_class)
-        # TODO: should we skip these steps for static methods as well?
-        # Since generic static methods should not be allowed.
         typ = map_instance_to_supertype(typ, method.info)
         member_type = expand_type_by_instance(signature, typ)
         freeze_all_type_vars(member_type)
@@ -743,10 +747,8 @@ def analyze_descriptor_access(descriptor_type: Type, mx: MemberContext) -> Type:
         callable_name=callable_name,
     )
 
-    mx.chk.check_deprecated(dunder_get, mx.context)
-    mx.chk.warn_deprecated_overload_item(
-        dunder_get, mx.context, target=inferred_dunder_get_type, selftype=descriptor_type
-    )
+    # Search for possible deprecations:
+    mx.chk.warn_deprecated(dunder_get, mx.context)
 
     inferred_dunder_get_type = get_proper_type(inferred_dunder_get_type)
     if isinstance(inferred_dunder_get_type, AnyType):
@@ -823,10 +825,7 @@ def analyze_descriptor_assign(descriptor_type: Instance, mx: MemberContext) -> T
     )
 
     # Search for possible deprecations:
-    mx.chk.check_deprecated(dunder_set, mx.context)
-    mx.chk.warn_deprecated_overload_item(
-        dunder_set, mx.context, target=inferred_dunder_set_type, selftype=descriptor_type
-    )
+    mx.chk.warn_deprecated(dunder_set, mx.context)
 
     # In the following cases, a message already will have been recorded in check_call.
     if (not isinstance(inferred_dunder_set_type, CallableType)) or (
@@ -922,6 +921,18 @@ def analyze_var(
         result = AnyType(TypeOfAny.special_form)
     fullname = f"{var.info.fullname}.{name}"
     hook = mx.chk.plugin.get_attribute_hook(fullname)
+
+    if var.info.is_enum and not mx.is_lvalue:
+        if name in var.info.enum_members and name not in {"name", "value"}:
+            enum_literal = LiteralType(name, fallback=itype)
+            result = itype.copy_modified(last_known_value=enum_literal)
+        elif (
+            isinstance(p_result := get_proper_type(result), Instance)
+            and p_result.type.fullname == "enum.nonmember"
+            and p_result.args
+        ):
+            # Unwrap nonmember similar to class-level access
+            result = p_result.args[0]
     if result and not (implicit or var.info.is_protocol and is_instance_var(var)):
         result = analyze_descriptor_access(result, mx)
     if hook:
@@ -954,7 +965,7 @@ def expand_and_bind_callable(
 ) -> Type:
     if not mx.preserve_type_var_ids:
         functype = freshen_all_functions_type_vars(functype)
-    typ = get_proper_type(expand_self_type(var, functype, mx.original_type))
+    typ = get_proper_type(expand_self_type(var, functype, mx.self_type))
     assert isinstance(typ, FunctionLike)
     if is_trivial_self:
         typ = bind_self_fast(typ, mx.self_type)
@@ -965,10 +976,23 @@ def expand_and_bind_callable(
     freeze_all_type_vars(expanded)
     if not var.is_property:
         return expanded
-    # TODO: a decorated property can result in Overloaded here.
-    assert isinstance(expanded, CallableType)
+    if isinstance(expanded, Overloaded):
+        # Legacy way to store settable properties is with overloads. Also in case it is
+        # an actual overloaded property, selecting first item that passed check_self_arg()
+        # is a good approximation, long-term we should use check_call() inference below.
+        if not expanded.items:
+            # A broken overload, error should be already reported.
+            return AnyType(TypeOfAny.from_error)
+        expanded = expanded.items[0]
+    assert isinstance(expanded, CallableType), expanded
     if var.is_settable_property and mx.is_lvalue and var.setter_type is not None:
-        # TODO: use check_call() to infer better type, same as for __set__().
+        if expanded.variables:
+            type_ctx = mx.rvalue or TempNode(AnyType(TypeOfAny.special_form), context=mx.context)
+            _, inferred_expanded = mx.chk.expr_checker.check_call(
+                expanded, [type_ctx], [ARG_POS], mx.context
+            )
+            expanded = get_proper_type(inferred_expanded)
+            assert isinstance(expanded, CallableType)
         if not expanded.arg_types:
             # This can happen when accessing invalid property from its own body,
             # error will be reported elsewhere.
@@ -1045,6 +1069,7 @@ def f(self: S) -> T: ...
     new_items = []
     if is_classmethod:
         dispatched_arg_type = TypeType.make_normalized(dispatched_arg_type)
+    p_dispatched_arg_type = get_proper_type(dispatched_arg_type)
 
     for item in items:
         if not item.arg_types or item.arg_kinds[0] not in (ARG_POS, ARG_STAR):
@@ -1053,28 +1078,42 @@ def f(self: S) -> T: ...
             # This is pretty bad, so just return the original signature if
             # there is at least one such error.
             return functype
-        else:
-            selfarg = get_proper_type(item.arg_types[0])
-            # This matches similar special-casing in bind_self(), see more details there.
-            self_callable = name == "__call__" and isinstance(selfarg, CallableType)
-            if self_callable or subtypes.is_subtype(
-                dispatched_arg_type,
-                # This level of erasure matches the one in checker.check_func_def(),
-                # better keep these two checks consistent.
-                erase_typevars(erase_to_bound(selfarg)),
-                # This is to work around the fact that erased ParamSpec and TypeVarTuple
-                # callables are not always compatible with non-erased ones both ways.
-                always_covariant=any(
-                    not isinstance(tv, TypeVarType) for tv in get_all_type_vars(selfarg)
-                ),
-                ignore_pos_arg_names=True,
-            ):
-                new_items.append(item)
-            elif isinstance(selfarg, ParamSpecType):
-                # TODO: This is not always right. What's the most reasonable thing to do here?
-                new_items.append(item)
-            elif isinstance(selfarg, TypeVarTupleType):
-                raise NotImplementedError
+        selfarg = get_proper_type(item.arg_types[0])
+        if isinstance(selfarg, Instance) and isinstance(p_dispatched_arg_type, Instance):
+            if selfarg.type is p_dispatched_arg_type.type and selfarg.args:
+                if not is_overlapping_types(p_dispatched_arg_type, selfarg):
+                    # This special casing is needed since `actual <: erased(template)`
+                    # logic below doesn't always work, and a more correct approach may
+                    # be tricky.
+                    continue
+        new_items.append(item)
+
+    if new_items:
+        items = new_items
+        new_items = []
+
+    for item in items:
+        selfarg = get_proper_type(item.arg_types[0])
+        # This matches similar special-casing in bind_self(), see more details there.
+        self_callable = name == "__call__" and isinstance(selfarg, CallableType)
+        if self_callable or is_subtype(
+            dispatched_arg_type,
+            # This level of erasure matches the one in checker.check_func_def(),
+            # better keep these two checks consistent.
+            erase_typevars(erase_to_bound(selfarg)),
+            # This is to work around the fact that erased ParamSpec and TypeVarTuple
+            # callables are not always compatible with non-erased ones both ways.
+            always_covariant=any(
+                not isinstance(tv, TypeVarType) for tv in get_all_type_vars(selfarg)
+            ),
+            ignore_pos_arg_names=True,
+        ):
+            new_items.append(item)
+        elif isinstance(selfarg, ParamSpecType):
+            # TODO: This is not always right. What's the most reasonable thing to do here?
+            new_items.append(item)
+        elif isinstance(selfarg, TypeVarTupleType):
+            raise NotImplementedError
     if not new_items:
         # Choose first item for the message (it may be not very helpful for overloads).
         msg.incompatible_self_argument(
@@ -1192,34 +1231,42 @@ def analyze_class_attribute_access(
 
         if isinstance(node.node, Var):
             assert isuper is not None
+            object_type = get_proper_type(mx.self_type)
             # Check if original variable type has type variables. For example:
             #     class C(Generic[T]):
             #         x: T
             #     C.x  # Error, ambiguous access
             #     C[int].x  # Also an error, since C[int] is same as C at runtime
             # Exception is Self type wrapped in ClassVar, that is safe.
+            prohibit_self = not node.node.is_classvar
             def_vars = set(node.node.info.defn.type_vars)
-            if not node.node.is_classvar and node.node.info.self_type:
+            if prohibit_self and node.node.info.self_type:
                 def_vars.add(node.node.info.self_type)
-            # TODO: should we include ParamSpec etc. here (i.e. use get_all_type_vars)?
-            typ_vars = set(get_type_vars(t))
-            if def_vars & typ_vars:
-                # Exception: access on Type[...], including first argument of class methods is OK.
-                if not isinstance(get_proper_type(mx.original_type), TypeType) or node.implicit:
-                    if node.node.is_classvar:
-                        message = message_registry.GENERIC_CLASS_VAR_ACCESS
-                    else:
-                        message = message_registry.GENERIC_INSTANCE_VAR_CLASS_ACCESS
-                    mx.fail(message)
+            # Exception: access on Type[...], including first argument of class methods is OK.
+            prohibit_generic = not isinstance(object_type, TypeType) or node.implicit
+            if prohibit_generic and def_vars & set(get_all_type_vars(t)):
+                if node.node.is_classvar:
+                    message = message_registry.GENERIC_CLASS_VAR_ACCESS
+                else:
+                    message = message_registry.GENERIC_INSTANCE_VAR_CLASS_ACCESS
+                mx.fail(message)
             t = expand_self_type_if_needed(t, mx, node.node, itype, is_class=True)
+            t = expand_type_by_instance(t, isuper)
             # Erase non-mapped variables, but keep mapped ones, even if there is an error.
             # In the above example this means that we infer following types:
             #     C.x -> Any
             #     C[int].x -> int
-            t = erase_typevars(expand_type_by_instance(t, isuper), {tv.id for tv in def_vars})
-
-        is_classmethod = (is_decorated and cast(Decorator, node.node).func.is_class) or (
-            isinstance(node.node, SYMBOL_FUNCBASE_TYPES) and node.node.is_class
+            if prohibit_generic:
+                erase_vars = set(itype.type.defn.type_vars)
+                if prohibit_self and itype.type.self_type:
+                    erase_vars.add(itype.type.self_type)
+                t = erase_typevars(t, {tv.id for tv in erase_vars})
+
+        is_classmethod = (
+            (is_decorated and cast(Decorator, node.node).func.is_class)
+            or (isinstance(node.node, SYMBOL_FUNCBASE_TYPES) and node.node.is_class)
+            or isinstance(node.node, Var)
+            and node.node.is_classmethod
         )
         t = get_proper_type(t)
         is_trivial_self = False
@@ -1228,9 +1275,14 @@ def analyze_class_attribute_access(
             is_trivial_self = node.node.func.is_trivial_self and not node.node.decorators
         elif isinstance(node.node, (FuncDef, OverloadedFuncDef)):
             is_trivial_self = node.node.is_trivial_self
-        if isinstance(t, FunctionLike) and is_classmethod and not is_trivial_self:
+        if (
+            isinstance(t, FunctionLike)
+            and is_classmethod
+            and not is_trivial_self
+            and not t.bound()
+        ):
             t = check_self_arg(t, mx.self_type, False, mx.context, name, mx.msg)
-        result = add_class_tvars(
+        t = add_class_tvars(
             t,
             isuper,
             is_classmethod,
@@ -1238,6 +1290,12 @@ def analyze_class_attribute_access(
             original_vars=original_vars,
             is_trivial_self=is_trivial_self,
         )
+        if is_decorated:
+            t = expand_self_type_if_needed(
+                t, mx, cast(Decorator, node.node).var, itype, is_class=is_classmethod
+            )
+
+        result = t
         # __set__ is not called on class objects.
         if not mx.is_lvalue:
             result = analyze_descriptor_access(result, mx)
@@ -1391,7 +1449,7 @@ class B(A[str]): pass
         tvars = original_vars if original_vars is not None else []
         if not mx.preserve_type_var_ids:
             t = freshen_all_functions_type_vars(t)
-        if is_classmethod:
+        if is_classmethod and not t.is_bound:
             if is_trivial_self:
                 t = bind_self_fast(t, mx.self_type)
             else:
@@ -1426,13 +1484,7 @@ def analyze_decorator_or_funcbase_access(
     if isinstance(defn, Decorator):
         return analyze_var(name, defn.var, itype, mx)
     typ = function_type(defn, mx.chk.named_type("builtins.function"))
-    is_trivial_self = False
-    if isinstance(defn, Decorator):
-        # Use fast path if there are trivial decorators like @classmethod or @property
-        is_trivial_self = defn.func.is_trivial_self and not defn.decorators
-    elif isinstance(defn, (FuncDef, OverloadedFuncDef)):
-        is_trivial_self = defn.is_trivial_self
-    if is_trivial_self:
+    if isinstance(defn, (FuncDef, OverloadedFuncDef)) and defn.is_trivial_self:
         return bind_self_fast(typ, mx.self_type)
     typ = check_self_arg(typ, mx.self_type, defn.is_class, mx.context, name, mx.msg)
     return bind_self(typ, original_type=mx.self_type, is_classmethod=defn.is_class)
@@ -1452,23 +1504,18 @@ def bind_self_fast(method: F, original_type: Type | None = None) -> F:
         items = [bind_self_fast(c, original_type) for c in method.items]
         return cast(F, Overloaded(items))
     assert isinstance(method, CallableType)
-    func: CallableType = method
-    if not func.arg_types:
+    if not method.arg_types:
         # Invalid method, return something.
         return method
-    if func.arg_kinds[0] in (ARG_STAR, ARG_STAR2):
+    if method.arg_kinds[0] in (ARG_STAR, ARG_STAR2):
         # See typeops.py for details.
         return method
-    original_type = get_proper_type(original_type)
-    if isinstance(original_type, CallableType) and original_type.is_type_obj():
-        original_type = TypeType.make_normalized(original_type.ret_type)
-    res = func.copy_modified(
-        arg_types=func.arg_types[1:],
-        arg_kinds=func.arg_kinds[1:],
-        arg_names=func.arg_names[1:],
+    return method.copy_modified(
+        arg_types=method.arg_types[1:],
+        arg_kinds=method.arg_kinds[1:],
+        arg_names=method.arg_names[1:],
         is_bound=True,
     )
-    return cast(F, res)
 
 
 def has_operator(typ: Type, op_method: str, named_type: Callable[[str], Instance]) -> bool:
diff --git a/mypy/checkpattern.py b/mypy/checkpattern.py
index 4cf7c1ca7862..f81684d2f44a 100644
--- a/mypy/checkpattern.py
+++ b/mypy/checkpattern.py
@@ -192,7 +192,7 @@ def visit_or_pattern(self, o: OrPattern) -> PatternType:
         for capture_list in capture_types.values():
             typ = UninhabitedType()
             for _, other in capture_list:
-                typ = join_types(typ, other)
+                typ = make_simplified_union([typ, other])
 
             captures[capture_list[0][0]] = typ
 
@@ -539,12 +539,12 @@ def visit_class_pattern(self, o: ClassPattern) -> PatternType:
         #
         type_info = o.class_ref.node
         if type_info is None:
-            return PatternType(AnyType(TypeOfAny.from_error), AnyType(TypeOfAny.from_error), {})
-        if isinstance(type_info, TypeAlias) and not type_info.no_args:
+            typ: Type = AnyType(TypeOfAny.from_error)
+        elif isinstance(type_info, TypeAlias) and not type_info.no_args:
             self.msg.fail(message_registry.CLASS_PATTERN_GENERIC_TYPE_ALIAS, o)
             return self.early_non_match()
-        if isinstance(type_info, TypeInfo):
-            typ: Type = fill_typevars_with_any(type_info)
+        elif isinstance(type_info, TypeInfo):
+            typ = fill_typevars_with_any(type_info)
         elif isinstance(type_info, TypeAlias):
             typ = type_info.target
         elif (
@@ -671,12 +671,15 @@ def visit_class_pattern(self, o: ClassPattern) -> PatternType:
                 has_local_errors = local_errors.has_new_errors()
             if has_local_errors or key_type is None:
                 key_type = AnyType(TypeOfAny.from_error)
-                self.msg.fail(
-                    message_registry.CLASS_PATTERN_UNKNOWN_KEYWORD.format(
-                        typ.str_with_options(self.options), keyword
-                    ),
-                    pattern,
-                )
+                if not (type_info and type_info.fullname == "builtins.object"):
+                    self.msg.fail(
+                        message_registry.CLASS_PATTERN_UNKNOWN_KEYWORD.format(
+                            typ.str_with_options(self.options), keyword
+                        ),
+                        pattern,
+                    )
+                elif keyword is not None:
+                    new_type = self.chk.add_any_attribute_to_type(new_type, keyword)
 
             inner_type, inner_rest_type, inner_captures = self.accept(pattern, key_type)
             if is_uninhabited(inner_type):
@@ -796,9 +799,9 @@ def get_var(expr: Expression) -> Var:
     Warning: this in only true for expressions captured by a match statement.
     Don't call it from anywhere else
     """
-    assert isinstance(expr, NameExpr)
+    assert isinstance(expr, NameExpr), expr
     node = expr.node
-    assert isinstance(node, Var)
+    assert isinstance(node, Var), node
     return node
 
 
diff --git a/mypy/config_parser.py b/mypy/config_parser.py
index e5c0dc893c76..5f08f342241e 100644
--- a/mypy/config_parser.py
+++ b/mypy/config_parser.py
@@ -17,15 +17,15 @@
 
 from collections.abc import Mapping, MutableMapping, Sequence
 from typing import Any, Callable, Final, TextIO, Union
-from typing_extensions import TypeAlias as _TypeAlias
+from typing_extensions import Never, TypeAlias
 
 from mypy import defaults
 from mypy.options import PER_MODULE_OPTIONS, Options
 
-_CONFIG_VALUE_TYPES: _TypeAlias = Union[
+_CONFIG_VALUE_TYPES: TypeAlias = Union[
     str, bool, int, float, dict[str, str], list[str], tuple[int, int]
 ]
-_INI_PARSER_CALLABLE: _TypeAlias = Callable[[Any], _CONFIG_VALUE_TYPES]
+_INI_PARSER_CALLABLE: TypeAlias = Callable[[Any], _CONFIG_VALUE_TYPES]
 
 
 class VersionTypeError(argparse.ArgumentTypeError):
@@ -60,14 +60,31 @@ def parse_version(v: str | float) -> tuple[int, int]:
     return major, minor
 
 
-def try_split(v: str | Sequence[str], split_regex: str = "[,]") -> list[str]:
-    """Split and trim a str or list of str into a list of str"""
+def try_split(v: str | Sequence[str] | object, split_regex: str = ",") -> list[str]:
+    """Split and trim a str or sequence (eg: list) of str into a list of str.
+    If an element of the input is not str, a type error will be raised."""
+
+    def complain(x: object, additional_info: str = "") -> Never:
+        raise argparse.ArgumentTypeError(
+            f"Expected a list or a stringified version thereof, but got: '{x}', of type {type(x).__name__}.{additional_info}"
+        )
+
     if isinstance(v, str):
         items = [p.strip() for p in re.split(split_regex, v)]
         if items and items[-1] == "":
             items.pop(-1)
         return items
-    return [p.strip() for p in v]
+    elif isinstance(v, Sequence):
+        return [
+            (
+                p.strip()
+                if isinstance(p, str)
+                else complain(p, additional_info=" (As an element of the list.)")
+            )
+            for p in v
+        ]
+    else:
+        complain(v)
 
 
 def validate_codes(codes: list[str]) -> list[str]:
@@ -650,9 +667,8 @@ def parse_mypy_comments(
     Returns a dictionary of options to be applied and a list of error messages
     generated.
     """
-
     errors: list[tuple[int, str]] = []
-    sections = {}
+    sections: dict[str, object] = {"enable_error_code": [], "disable_error_code": []}
 
     for lineno, line in args:
         # In order to easily match the behavior for bools, we abuse configparser.
@@ -660,7 +676,6 @@ def parse_mypy_comments(
         # method is to create a config parser.
         parser = configparser.RawConfigParser()
         options, parse_errors = mypy_comments_to_config_map(line, template)
-
         if "python_version" in options:
             errors.append((lineno, "python_version not supported in inline configuration"))
             del options["python_version"]
@@ -690,9 +705,24 @@ def set_strict_flags() -> None:
                     '(see "mypy -h" for the list of flags enabled in strict mode)',
                 )
             )
-
+        # Because this is currently special-cased
+        # (the new_sections for an inline config *always* includes 'disable_error_code' and
+        # 'enable_error_code' fields, usually empty, which overwrite the old ones),
+        # we have to manipulate them specially.
+        # This could use a refactor, but so could the whole subsystem.
+        if (
+            "enable_error_code" in new_sections
+            and isinstance(neec := new_sections["enable_error_code"], list)
+            and isinstance(eec := sections.get("enable_error_code", []), list)
+        ):
+            new_sections["enable_error_code"] = sorted(set(neec + eec))
+        if (
+            "disable_error_code" in new_sections
+            and isinstance(ndec := new_sections["disable_error_code"], list)
+            and isinstance(dec := sections.get("disable_error_code", []), list)
+        ):
+            new_sections["disable_error_code"] = sorted(set(ndec + dec))
         sections.update(new_sections)
-
     return sections, errors
 
 
diff --git a/mypy/constraints.py b/mypy/constraints.py
index 293618556203..6416791fa74a 100644
--- a/mypy/constraints.py
+++ b/mypy/constraints.py
@@ -1110,7 +1110,10 @@ def visit_callable_type(self, template: CallableType) -> list[Constraint]:
                     # like U -> U, should be Callable[..., Any], but if U is a self-type, we can
                     # allow it to leak, to be later bound to self. A bunch of existing code
                     # depends on this old behaviour.
-                    and not any(tv.id.is_self() for tv in cactual.variables)
+                    and not (
+                        any(tv.id.is_self() for tv in cactual.variables)
+                        and template.is_ellipsis_args
+                    )
                 ):
                     # If the actual callable is generic, infer constraints in the opposite
                     # direction, and indicate to the solver there are extra type variables
@@ -1335,6 +1338,11 @@ def visit_tuple_type(self, template: TupleType) -> list[Constraint]:
                     res.extend(
                         infer_constraints(template_items[i], actual_items[i], self.direction)
                     )
+            res.extend(
+                infer_constraints(
+                    template.partial_fallback, actual.partial_fallback, self.direction
+                )
+            )
             return res
         elif isinstance(actual, AnyType):
             return self.infer_against_any(template.items, actual)
diff --git a/mypy/dmypy/client.py b/mypy/dmypy/client.py
index b34e9bf8ced2..3db47f80d01b 100644
--- a/mypy/dmypy/client.py
+++ b/mypy/dmypy/client.py
@@ -36,9 +36,6 @@ def __init__(self, prog: str, **kwargs: Any) -> None:
 parser = argparse.ArgumentParser(
     prog="dmypy", description="Client for mypy daemon mode", fromfile_prefix_chars="@"
 )
-if sys.version_info >= (3, 14):
-    parser.color = True  # Set as init arg in 3.14
-
 parser.set_defaults(action=None)
 parser.add_argument(
     "--status-file", default=DEFAULT_STATUS_FILE, help="status file to retrieve daemon details"
diff --git a/mypy/erasetype.py b/mypy/erasetype.py
index 6c47670d6687..3f33ea1648f0 100644
--- a/mypy/erasetype.py
+++ b/mypy/erasetype.py
@@ -145,29 +145,34 @@ def erase_typevars(t: Type, ids_to_erase: Container[TypeVarId] | None = None) ->
     or just the ones in the provided collection.
     """
 
+    if ids_to_erase is None:
+        return t.accept(TypeVarEraser(None, AnyType(TypeOfAny.special_form)))
+
     def erase_id(id: TypeVarId) -> bool:
-        if ids_to_erase is None:
-            return True
         return id in ids_to_erase
 
     return t.accept(TypeVarEraser(erase_id, AnyType(TypeOfAny.special_form)))
 
 
+def erase_meta_id(id: TypeVarId) -> bool:
+    return id.is_meta_var()
+
+
 def replace_meta_vars(t: Type, target_type: Type) -> Type:
     """Replace unification variables in a type with the target type."""
-    return t.accept(TypeVarEraser(lambda id: id.is_meta_var(), target_type))
+    return t.accept(TypeVarEraser(erase_meta_id, target_type))
 
 
 class TypeVarEraser(TypeTranslator):
     """Implementation of type erasure"""
 
-    def __init__(self, erase_id: Callable[[TypeVarId], bool], replacement: Type) -> None:
+    def __init__(self, erase_id: Callable[[TypeVarId], bool] | None, replacement: Type) -> None:
         super().__init__()
         self.erase_id = erase_id
         self.replacement = replacement
 
     def visit_type_var(self, t: TypeVarType) -> Type:
-        if self.erase_id(t.id):
+        if self.erase_id is None or self.erase_id(t.id):
             return self.replacement
         return t
 
@@ -212,12 +217,12 @@ def visit_callable_type(self, t: CallableType) -> Type:
         return result
 
     def visit_type_var_tuple(self, t: TypeVarTupleType) -> Type:
-        if self.erase_id(t.id):
+        if self.erase_id is None or self.erase_id(t.id):
             return t.tuple_fallback.copy_modified(args=[self.replacement])
         return t
 
     def visit_param_spec(self, t: ParamSpecType) -> Type:
-        if self.erase_id(t.id):
+        if self.erase_id is None or self.erase_id(t.id):
             return self.replacement
         return t
 
diff --git a/mypy/errorcodes.py b/mypy/errorcodes.py
index c22308e4a754..bcfdbf6edc2b 100644
--- a/mypy/errorcodes.py
+++ b/mypy/errorcodes.py
@@ -37,6 +37,10 @@ def __init__(
     def __str__(self) -> str:
         return f"<ErrorCode {self.code}>"
 
+    def __repr__(self) -> str:
+        """This doesn't fulfill the goals of repr but it's better than the default view."""
+        return f"<ErrorCode {self.category}: {self.code}>"
+
     def __eq__(self, other: object) -> bool:
         if not isinstance(other, ErrorCode):
             return False
@@ -270,6 +274,7 @@ def __hash__(self) -> int:
     "General",
     default_enabled=False,
 )
+METACLASS: Final[ErrorCode] = ErrorCode("metaclass", "Ensure that metaclass is valid", "General")
 
 # Syntax errors are often blocking.
 SYNTAX: Final[ErrorCode] = ErrorCode("syntax", "Report syntax errors", "General")
diff --git a/mypy/errors.py b/mypy/errors.py
index 7a173f16d196..f1b2faf67401 100644
--- a/mypy/errors.py
+++ b/mypy/errors.py
@@ -4,15 +4,18 @@
 import sys
 import traceback
 from collections import defaultdict
-from collections.abc import Iterable
+from collections.abc import Iterable, Iterator
+from itertools import chain
 from typing import Callable, Final, NoReturn, Optional, TextIO, TypeVar
 from typing_extensions import Literal, Self, TypeAlias as _TypeAlias
 
 from mypy import errorcodes as codes
 from mypy.error_formatter import ErrorFormatter
 from mypy.errorcodes import IMPORT, IMPORT_NOT_FOUND, IMPORT_UNTYPED, ErrorCode, mypy_error_codes
+from mypy.nodes import Context
 from mypy.options import Options
 from mypy.scope import Scope
+from mypy.types import Type
 from mypy.util import DEFAULT_SOURCE_OFFSET, is_typeshed_file
 from mypy.version import __version__ as mypy_version
 
@@ -164,6 +167,10 @@ class ErrorWatcher:
     out by one of the ErrorWatcher instances.
     """
 
+    # public attribute for the special treatment of `reveal_type` by
+    # `MessageBuilder.reveal_type`:
+    filter_revealed_type: bool
+
     def __init__(
         self,
         errors: Errors,
@@ -171,11 +178,13 @@ def __init__(
         filter_errors: bool | Callable[[str, ErrorInfo], bool] = False,
         save_filtered_errors: bool = False,
         filter_deprecated: bool = False,
+        filter_revealed_type: bool = False,
     ) -> None:
         self.errors = errors
         self._has_new_errors = False
         self._filter = filter_errors
         self._filter_deprecated = filter_deprecated
+        self.filter_revealed_type = filter_revealed_type
         self._filtered: list[ErrorInfo] | None = [] if save_filtered_errors else None
 
     def __enter__(self) -> Self:
@@ -197,7 +206,8 @@ def on_error(self, file: str, info: ErrorInfo) -> bool:
         """
         if info.code == codes.DEPRECATED:
             # Deprecated is not a type error, so it is handled on opt-in basis here.
-            return self._filter_deprecated
+            if not self._filter_deprecated:
+                return False
 
         self._has_new_errors = True
         if isinstance(self._filter, bool):
@@ -219,23 +229,69 @@ def filtered_errors(self) -> list[ErrorInfo]:
         return self._filtered
 
 
-class LoopErrorWatcher(ErrorWatcher):
-    """Error watcher that filters and separately collects `unreachable` errors,
-    `redundant-expr` and `redundant-casts` errors, and revealed types when analysing
-    loops iteratively to help avoid making too-hasty reports."""
+class IterationDependentErrors:
+    """An `IterationDependentErrors` instance serves to collect the `unreachable`,
+    `redundant-expr`, and `redundant-casts` errors, as well as the revealed types,
+    handled by the individual `IterationErrorWatcher` instances sequentially applied to
+    the same code section."""
+
+    # One set of `unreachable`, `redundant-expr`, and `redundant-casts` errors per
+    # iteration step.  Meaning of the tuple items: ErrorCode, message, line, column,
+    # end_line, end_column.
+    uselessness_errors: list[set[tuple[ErrorCode, str, int, int, int, int]]]
+
+    # One set of unreachable line numbers per iteration step.  Not only the lines where
+    # the error report occurs but really all unreachable lines.
+    unreachable_lines: list[set[int]]
+
+    # One list of revealed types for each `reveal_type` statement.  Each created list
+    # can grow during the iteration.  Meaning of the tuple items: line, column,
+    # end_line, end_column:
+    revealed_types: dict[tuple[int, int, int | None, int | None], list[Type]]
+
+    def __init__(self) -> None:
+        self.uselessness_errors = []
+        self.unreachable_lines = []
+        self.revealed_types = defaultdict(list)
+
+    def yield_uselessness_error_infos(self) -> Iterator[tuple[str, Context, ErrorCode]]:
+        """Report only those `unreachable`, `redundant-expr`, and `redundant-casts`
+        errors that could not be ruled out in any iteration step."""
+
+        persistent_uselessness_errors = set()
+        for candidate in set(chain(*self.uselessness_errors)):
+            if all(
+                (candidate in errors) or (candidate[2] in lines)
+                for errors, lines in zip(self.uselessness_errors, self.unreachable_lines)
+            ):
+                persistent_uselessness_errors.add(candidate)
+        for error_info in persistent_uselessness_errors:
+            context = Context(line=error_info[2], column=error_info[3])
+            context.end_line = error_info[4]
+            context.end_column = error_info[5]
+            yield error_info[1], context, error_info[0]
 
-    # Meaning of the tuple items: ErrorCode, message, line, column, end_line, end_column:
-    uselessness_errors: set[tuple[ErrorCode, str, int, int, int, int]]
+    def yield_revealed_type_infos(self) -> Iterator[tuple[list[Type], Context]]:
+        """Yield all types revealed in at least one iteration step."""
 
-    # Meaning of the tuple items: function_or_member, line, column, end_line, end_column:
-    revealed_types: dict[tuple[str | None, int, int, int, int], set[str]]
+        for note_info, types in self.revealed_types.items():
+            context = Context(line=note_info[0], column=note_info[1])
+            context.end_line = note_info[2]
+            context.end_column = note_info[3]
+            yield types, context
 
-    # Not only the lines where the error report occurs but really all unreachable lines:
-    unreachable_lines: set[int]
+
+class IterationErrorWatcher(ErrorWatcher):
+    """Error watcher that filters and separately collects `unreachable` errors,
+    `redundant-expr` and `redundant-casts` errors, and revealed types when analysing
+    code sections iteratively to help avoid making too-hasty reports."""
+
+    iteration_dependent_errors: IterationDependentErrors
 
     def __init__(
         self,
         errors: Errors,
+        iteration_dependent_errors: IterationDependentErrors,
         *,
         filter_errors: bool | Callable[[str, ErrorInfo], bool] = False,
         save_filtered_errors: bool = False,
@@ -247,27 +303,22 @@ def __init__(
             save_filtered_errors=save_filtered_errors,
             filter_deprecated=filter_deprecated,
         )
-        self.uselessness_errors = set()
-        self.unreachable_lines = set()
-        self.revealed_types = defaultdict(set)
+        self.iteration_dependent_errors = iteration_dependent_errors
+        iteration_dependent_errors.uselessness_errors.append(set())
+        iteration_dependent_errors.unreachable_lines.append(set())
 
     def on_error(self, file: str, info: ErrorInfo) -> bool:
+        """Filter out the "iteration-dependent" errors and notes and store their
+        information to handle them after iteration is completed."""
+
+        iter_errors = self.iteration_dependent_errors
 
         if info.code in (codes.UNREACHABLE, codes.REDUNDANT_EXPR, codes.REDUNDANT_CAST):
-            self.uselessness_errors.add(
+            iter_errors.uselessness_errors[-1].add(
                 (info.code, info.message, info.line, info.column, info.end_line, info.end_column)
             )
             if info.code == codes.UNREACHABLE:
-                self.unreachable_lines.update(range(info.line, info.end_line + 1))
-            return True
-
-        if info.code == codes.MISC and info.message.startswith("Revealed type is "):
-            key = info.function_or_member, info.line, info.column, info.end_line, info.end_column
-            types = info.message.split('"')[1]
-            if types.startswith("Union["):
-                self.revealed_types[key].update(types[6:-1].split(", "))
-            else:
-                self.revealed_types[key].add(types)
+                iter_errors.unreachable_lines[-1].update(range(info.line, info.end_line + 1))
             return True
 
         return super().on_error(file, info)
@@ -340,7 +391,7 @@ class Errors:
     # in some cases to avoid reporting huge numbers of errors.
     seen_import_error = False
 
-    _watchers: list[ErrorWatcher] = []
+    _watchers: list[ErrorWatcher]
 
     def __init__(
         self,
@@ -371,6 +422,7 @@ def initialize(self) -> None:
         self.scope = None
         self.target_module = None
         self.seen_import_error = False
+        self._watchers = []
 
     def reset(self) -> None:
         self.initialize()
@@ -534,18 +586,19 @@ def _add_error_info(self, file: str, info: ErrorInfo) -> None:
         if info.code in (IMPORT, IMPORT_UNTYPED, IMPORT_NOT_FOUND):
             self.seen_import_error = True
 
+    def get_watchers(self) -> Iterator[ErrorWatcher]:
+        """Yield the `ErrorWatcher` stack from top to bottom."""
+        i = len(self._watchers)
+        while i > 0:
+            i -= 1
+            yield self._watchers[i]
+
     def _filter_error(self, file: str, info: ErrorInfo) -> bool:
         """
         process ErrorWatcher stack from top to bottom,
         stopping early if error needs to be filtered out
         """
-        i = len(self._watchers)
-        while i > 0:
-            i -= 1
-            w = self._watchers[i]
-            if w.on_error(file, info):
-                return True
-        return False
+        return any(w.on_error(file, info) for w in self.get_watchers())
 
     def add_error_info(self, info: ErrorInfo) -> None:
         file, lines = info.origin
@@ -786,6 +839,8 @@ def generate_unused_ignore_errors(self, file: str) -> None:
                 code=codes.UNUSED_IGNORE,
                 blocker=False,
                 only_once=False,
+                origin=(self.file, [line]),
+                target=self.target_module,
             )
             self._add_error_info(file, info)
 
@@ -837,6 +892,8 @@ def generate_ignore_without_code_errors(
                 code=codes.IGNORE_WITHOUT_CODE,
                 blocker=False,
                 only_once=False,
+                origin=(self.file, [line]),
+                target=self.target_module,
             )
             self._add_error_info(file, info)
 
@@ -876,7 +933,8 @@ def prefer_simple_messages(self) -> bool:
         if self.file in self.ignored_files:
             # Errors ignored, so no point generating fancy messages
             return True
-        for _watcher in self._watchers:
+        if self._watchers:
+            _watcher = self._watchers[-1]
             if _watcher._filter is True and _watcher._filtered is None:
                 # Errors are filtered
                 return True
diff --git a/mypy/expandtype.py b/mypy/expandtype.py
index d27105f48ed3..e2a42317141f 100644
--- a/mypy/expandtype.py
+++ b/mypy/expandtype.py
@@ -1,6 +1,6 @@
 from __future__ import annotations
 
-from collections.abc import Iterable, Mapping, Sequence
+from collections.abc import Iterable, Mapping
 from typing import Final, TypeVar, cast, overload
 
 from mypy.nodes import ARG_STAR, FakeInfo, Var
@@ -182,7 +182,7 @@ class ExpandTypeVisitor(TrivialSyntheticTypeTranslator):
     def __init__(self, variables: Mapping[TypeVarId, Type]) -> None:
         super().__init__()
         self.variables = variables
-        self.recursive_tvar_guard: dict[TypeVarId, Type | None] = {}
+        self.recursive_tvar_guard: dict[TypeVarId, Type | None] | None = None
 
     def visit_unbound_type(self, t: UnboundType) -> Type:
         return t
@@ -209,7 +209,10 @@ def visit_erased_type(self, t: ErasedType) -> Type:
         return t
 
     def visit_instance(self, t: Instance) -> Type:
-        args = self.expand_types_with_unpack(list(t.args))
+        if len(t.args) == 0:
+            return t
+
+        args = self.expand_type_tuple_with_unpack(t.args)
 
         if isinstance(t.type, FakeInfo):
             # The type checker expands function definitions and bodies
@@ -243,6 +246,8 @@ def visit_type_var(self, t: TypeVarType) -> Type:
             # If I try to remove this special-casing ~40 tests fail on reveal_type().
             return repl.copy_modified(last_known_value=None)
         if isinstance(repl, TypeVarType) and repl.has_default():
+            if self.recursive_tvar_guard is None:
+                self.recursive_tvar_guard = {}
             if (tvar_id := repl.id) in self.recursive_tvar_guard:
                 return self.recursive_tvar_guard[tvar_id] or repl
             self.recursive_tvar_guard[tvar_id] = None
@@ -431,7 +436,7 @@ def visit_overloaded(self, t: Overloaded) -> Type:
             items.append(new_item)
         return Overloaded(items)
 
-    def expand_types_with_unpack(self, typs: Sequence[Type]) -> list[Type]:
+    def expand_type_list_with_unpack(self, typs: list[Type]) -> list[Type]:
         """Expands a list of types that has an unpack."""
         items: list[Type] = []
         for item in typs:
@@ -441,8 +446,19 @@ def expand_types_with_unpack(self, typs: Sequence[Type]) -> list[Type]:
                 items.append(item.accept(self))
         return items
 
+    def expand_type_tuple_with_unpack(self, typs: tuple[Type, ...]) -> list[Type]:
+        """Expands a tuple of types that has an unpack."""
+        # Micro-optimization: Specialized variant of expand_type_list_with_unpack
+        items: list[Type] = []
+        for item in typs:
+            if isinstance(item, UnpackType) and isinstance(item.type, TypeVarTupleType):
+                items.extend(self.expand_unpack(item))
+            else:
+                items.append(item.accept(self))
+        return items
+
     def visit_tuple_type(self, t: TupleType) -> Type:
-        items = self.expand_types_with_unpack(t.items)
+        items = self.expand_type_list_with_unpack(t.items)
         if len(items) == 1:
             # Normalize Tuple[*Tuple[X, ...]] -> Tuple[X, ...]
             item = items[0]
@@ -510,7 +526,9 @@ def visit_type_type(self, t: TypeType) -> Type:
     def visit_type_alias_type(self, t: TypeAliasType) -> Type:
         # Target of the type alias cannot contain type variables (not bound by the type
         # alias itself), so we just expand the arguments.
-        args = self.expand_types_with_unpack(t.args)
+        if len(t.args) == 0:
+            return t
+        args = self.expand_type_list_with_unpack(t.args)
         # TODO: normalize if target is Tuple, and args are [*tuple[X, ...]]?
         return t.copy_modified(args=args)
 
diff --git a/mypy/fastparse.py b/mypy/fastparse.py
index e2af2198cdfd..6b2eb532003c 100644
--- a/mypy/fastparse.py
+++ b/mypy/fastparse.py
@@ -129,9 +129,7 @@
 PY_MINOR_VERSION: Final = sys.version_info[1]
 
 import ast as ast3
-
-# TODO: Index, ExtSlice are deprecated in 3.9.
-from ast import AST, Attribute, Call, FunctionType, Index, Name, Starred, UAdd, UnaryOp, USub
+from ast import AST, Attribute, Call, FunctionType, Name, Starred, UAdd, UnaryOp, USub
 
 
 def ast3_parse(
@@ -188,6 +186,13 @@ def ast3_parse(
     ast_TypeVar = Any
     ast_TypeVarTuple = Any
 
+if sys.version_info >= (3, 14):
+    ast_TemplateStr = ast3.TemplateStr
+    ast_Interpolation = ast3.Interpolation
+else:
+    ast_TemplateStr = Any
+    ast_Interpolation = Any
+
 N = TypeVar("N", bound=Node)
 
 # There is no way to create reasonable fallbacks at this stage,
@@ -631,7 +636,7 @@ def fix_function_overloads(self, stmts: list[Statement]) -> list[Statement]:
         ret: list[Statement] = []
         current_overload: list[OverloadPart] = []
         current_overload_name: str | None = None
-        seen_unconditional_func_def = False
+        last_unconditional_func_def: str | None = None
         last_if_stmt: IfStmt | None = None
         last_if_overload: Decorator | FuncDef | OverloadedFuncDef | None = None
         last_if_stmt_overload_name: str | None = None
@@ -641,7 +646,7 @@ def fix_function_overloads(self, stmts: list[Statement]) -> list[Statement]:
             if_overload_name: str | None = None
             if_block_with_overload: Block | None = None
             if_unknown_truth_value: IfStmt | None = None
-            if isinstance(stmt, IfStmt) and seen_unconditional_func_def is False:
+            if isinstance(stmt, IfStmt):
                 # Check IfStmt block to determine if function overloads can be merged
                 if_overload_name = self._check_ifstmt_for_overloads(stmt, current_overload_name)
                 if if_overload_name is not None:
@@ -669,11 +674,18 @@ def fix_function_overloads(self, stmts: list[Statement]) -> list[Statement]:
                     last_if_unknown_truth_value = None
                 current_overload.append(stmt)
                 if isinstance(stmt, FuncDef):
-                    seen_unconditional_func_def = True
+                    # This is, strictly speaking, wrong: there might be a decorated
+                    # implementation. However, it only affects the error message we show:
+                    # ideally it's "already defined", but "implementation must come last"
+                    # is also reasonable.
+                    # TODO: can we get rid of this completely and just always emit
+                    # "implementation must come last" instead?
+                    last_unconditional_func_def = stmt.name
             elif (
                 current_overload_name is not None
                 and isinstance(stmt, IfStmt)
                 and if_overload_name == current_overload_name
+                and last_unconditional_func_def != current_overload_name
             ):
                 # IfStmt only contains stmts relevant to current_overload.
                 # Check if stmts are reachable and add them to current_overload,
@@ -729,7 +741,7 @@ def fix_function_overloads(self, stmts: list[Statement]) -> list[Statement]:
                 # most of mypy/mypyc assumes that all the functions in an OverloadedFuncDef are
                 # related, but multiple underscore functions next to each other aren't necessarily
                 # related
-                seen_unconditional_func_def = False
+                last_unconditional_func_def = None
                 if isinstance(stmt, Decorator) and not unnamed_function(stmt.name):
                     current_overload = [stmt]
                     current_overload_name = stmt.name
@@ -1698,6 +1710,21 @@ def visit_FormattedValue(self, n: ast3.FormattedValue) -> Expression:
         )
         return self.set_line(result_expression, n)
 
+    # TemplateStr(expr* values)
+    def visit_TemplateStr(self, n: ast_TemplateStr) -> Expression:
+        self.fail(
+            ErrorMessage("PEP 750 template strings are not yet supported"),
+            n.lineno,
+            n.col_offset,
+            blocker=False,
+        )
+        e = TempNode(AnyType(TypeOfAny.from_error))
+        return self.set_line(e, n)
+
+    # Interpolation(expr value, constant str, int conversion, expr? format_spec)
+    def visit_Interpolation(self, n: ast_Interpolation) -> Expression:
+        assert False, "Unreachable"
+
     # Attribute(expr value, identifier attr, expr_context ctx)
     def visit_Attribute(self, n: Attribute) -> MemberExpr | SuperExpr:
         value = n.value
@@ -1750,18 +1777,6 @@ def visit_Slice(self, n: ast3.Slice) -> SliceExpr:
         e = SliceExpr(self.visit(n.lower), self.visit(n.upper), self.visit(n.step))
         return self.set_line(e, n)
 
-    # ExtSlice(slice* dims)
-    def visit_ExtSlice(self, n: ast3.ExtSlice) -> TupleExpr:
-        # cast for mypyc's benefit on Python 3.9
-        return TupleExpr(self.translate_expr_list(cast(Any, n).dims))
-
-    # Index(expr value)
-    def visit_Index(self, n: Index) -> Node:
-        # cast for mypyc's benefit on Python 3.9
-        value = self.visit(cast(Any, n).value)
-        assert isinstance(value, Node)
-        return value
-
     # Match(expr subject, match_case* cases) # python 3.10 and later
     def visit_Match(self, n: Match) -> MatchStmt:
         node = MatchStmt(
@@ -2227,7 +2242,7 @@ def visit_index_expr(self, e: IndexExpr) -> None:
         pass
 
     def visit_member_expr(self, e: MemberExpr) -> None:
-        if self.lvalue:
+        if self.lvalue and isinstance(e.expr, NameExpr):
             self.found = True
 
 
diff --git a/mypy/fixup.py b/mypy/fixup.py
index 0e9c186fd42a..bec5929ad4b1 100644
--- a/mypy/fixup.py
+++ b/mypy/fixup.py
@@ -29,6 +29,7 @@
     Overloaded,
     Parameters,
     ParamSpecType,
+    ProperType,
     TupleType,
     TypeAliasType,
     TypedDictType,
@@ -96,6 +97,8 @@ def visit_type_info(self, info: TypeInfo) -> None:
                 info.declared_metaclass.accept(self.type_fixer)
             if info.metaclass_type:
                 info.metaclass_type.accept(self.type_fixer)
+            if info.self_type:
+                info.self_type.accept(self.type_fixer)
             if info.alt_promote:
                 info.alt_promote.accept(self.type_fixer)
                 instance = Instance(info, [])
@@ -165,6 +168,8 @@ def visit_func_def(self, func: FuncDef) -> None:
             func.info = self.current_info
         if func.type is not None:
             func.type.accept(self.type_fixer)
+            if isinstance(func.type, CallableType):
+                func.type.definition = func
 
     def visit_overloaded_func_def(self, o: OverloadedFuncDef) -> None:
         if self.current_info is not None:
@@ -175,6 +180,10 @@ def visit_overloaded_func_def(self, o: OverloadedFuncDef) -> None:
             item.accept(self)
         if o.impl:
             o.impl.accept(self)
+        if isinstance(o.type, Overloaded):
+            # For error messages we link the original definition for each item.
+            for typ, item in zip(o.type.items, o.items):
+                typ.definition = item
 
     def visit_decorator(self, d: Decorator) -> None:
         if self.current_info is not None:
@@ -185,6 +194,9 @@ def visit_decorator(self, d: Decorator) -> None:
             d.var.accept(self)
         for node in d.decorators:
             node.accept(self)
+        typ = d.var.type
+        if isinstance(typ, ProperType) and isinstance(typ, CallableType):
+            typ.definition = d.func
 
     def visit_class_def(self, c: ClassDef) -> None:
         for v in c.type_vars:
diff --git a/mypy/fscache.py b/mypy/fscache.py
index 8251f4bd9488..240370159fff 100644
--- a/mypy/fscache.py
+++ b/mypy/fscache.py
@@ -117,7 +117,12 @@ def init_under_package_root(self, path: str) -> bool:
             if not stat.S_ISDIR(st.st_mode):
                 return False
         ok = False
-        drive, path = os.path.splitdrive(path)  # Ignore Windows drive name
+
+        # skip if on a different drive
+        current_drive, _ = os.path.splitdrive(os.getcwd())
+        drive, _ = os.path.splitdrive(path)
+        if drive != current_drive:
+            return False
         if os.path.isabs(path):
             path = os.path.relpath(path)
         path = os.path.normpath(path)
diff --git a/mypy/indirection.py b/mypy/indirection.py
index 4f455d2c1dc9..8c24c7242c96 100644
--- a/mypy/indirection.py
+++ b/mypy/indirection.py
@@ -32,11 +32,30 @@ def find_modules(self, typs: Iterable[types.Type]) -> set[str]:
         self.modules = set()
         self.seen_fullnames = set()
         self.seen_aliases = set()
-        self._visit(typs)
+        for typ in typs:
+            self._visit(typ)
         return self.modules
 
-    def _visit(self, typ_or_typs: types.Type | Iterable[types.Type]) -> None:
-        typs = [typ_or_typs] if isinstance(typ_or_typs, types.Type) else typ_or_typs
+    def _visit(self, typ: types.Type) -> None:
+        if isinstance(typ, types.TypeAliasType):
+            # Avoid infinite recursion for recursive type aliases.
+            if typ in self.seen_aliases:
+                return
+            self.seen_aliases.add(typ)
+        typ.accept(self)
+
+    def _visit_type_tuple(self, typs: tuple[types.Type, ...]) -> None:
+        # Micro-optimization: Specialized version of _visit for lists
+        for typ in typs:
+            if isinstance(typ, types.TypeAliasType):
+                # Avoid infinite recursion for recursive type aliases.
+                if typ in self.seen_aliases:
+                    continue
+                self.seen_aliases.add(typ)
+            typ.accept(self)
+
+    def _visit_type_list(self, typs: list[types.Type]) -> None:
+        # Micro-optimization: Specialized version of _visit for tuples
         for typ in typs:
             if isinstance(typ, types.TypeAliasType):
                 # Avoid infinite recursion for recursive type aliases.
@@ -50,7 +69,7 @@ def _visit_module_name(self, module_name: str) -> None:
             self.modules.update(split_module_names(module_name))
 
     def visit_unbound_type(self, t: types.UnboundType) -> None:
-        self._visit(t.args)
+        self._visit_type_tuple(t.args)
 
     def visit_any(self, t: types.AnyType) -> None:
         pass
@@ -68,7 +87,7 @@ def visit_deleted_type(self, t: types.DeletedType) -> None:
         pass
 
     def visit_type_var(self, t: types.TypeVarType) -> None:
-        self._visit(t.values)
+        self._visit_type_list(t.values)
         self._visit(t.upper_bound)
         self._visit(t.default)
 
@@ -84,10 +103,10 @@ def visit_unpack_type(self, t: types.UnpackType) -> None:
         t.type.accept(self)
 
     def visit_parameters(self, t: types.Parameters) -> None:
-        self._visit(t.arg_types)
+        self._visit_type_list(t.arg_types)
 
     def visit_instance(self, t: types.Instance) -> None:
-        self._visit(t.args)
+        self._visit_type_tuple(t.args)
         if t.type:
             # Uses of a class depend on everything in the MRO,
             # as changes to classes in the MRO can add types to methods,
@@ -98,7 +117,7 @@ def visit_instance(self, t: types.Instance) -> None:
                 self._visit_module_name(t.type.metaclass_type.type.module_name)
 
     def visit_callable_type(self, t: types.CallableType) -> None:
-        self._visit(t.arg_types)
+        self._visit_type_list(t.arg_types)
         self._visit(t.ret_type)
         if t.definition is not None:
             fullname = t.definition.fullname
@@ -107,22 +126,22 @@ def visit_callable_type(self, t: types.CallableType) -> None:
                 self.seen_fullnames.add(fullname)
 
     def visit_overloaded(self, t: types.Overloaded) -> None:
-        self._visit(t.items)
+        self._visit_type_list(list(t.items))
         self._visit(t.fallback)
 
     def visit_tuple_type(self, t: types.TupleType) -> None:
-        self._visit(t.items)
+        self._visit_type_list(t.items)
         self._visit(t.partial_fallback)
 
     def visit_typeddict_type(self, t: types.TypedDictType) -> None:
-        self._visit(t.items.values())
+        self._visit_type_list(list(t.items.values()))
         self._visit(t.fallback)
 
     def visit_literal_type(self, t: types.LiteralType) -> None:
         self._visit(t.fallback)
 
     def visit_union_type(self, t: types.UnionType) -> None:
-        self._visit(t.items)
+        self._visit_type_list(t.items)
 
     def visit_partial_type(self, t: types.PartialType) -> None:
         pass
diff --git a/mypy/join.py b/mypy/join.py
index a012a633dfa3..099df02680f0 100644
--- a/mypy/join.py
+++ b/mypy/join.py
@@ -625,6 +625,8 @@ def visit_literal_type(self, t: LiteralType) -> ProperType:
             if self.s.fallback.type.is_enum and t.fallback.type.is_enum:
                 return mypy.typeops.make_simplified_union([self.s, t])
             return join_types(self.s.fallback, t.fallback)
+        elif isinstance(self.s, Instance) and self.s.last_known_value == t:
+            return t
         else:
             return join_types(self.s, t.fallback)
 
diff --git a/mypy/main.py b/mypy/main.py
index a407a88d3ac1..d5bbca704305 100644
--- a/mypy/main.py
+++ b/mypy/main.py
@@ -462,24 +462,18 @@ def __call__(
         parser.exit()
 
 
-def process_options(
-    args: list[str],
-    stdout: TextIO | None = None,
-    stderr: TextIO | None = None,
-    require_targets: bool = True,
-    server_options: bool = False,
-    fscache: FileSystemCache | None = None,
+def define_options(
     program: str = "mypy",
     header: str = HEADER,
-) -> tuple[list[BuildSource], Options]:
-    """Parse command line arguments.
-
-    If a FileSystemCache is passed in, and package_root options are given,
-    call fscache.set_package_root() to set the cache's package root.
-    """
-    stdout = stdout or sys.stdout
-    stderr = stderr or sys.stderr
-
+    stdout: TextIO = sys.stdout,
+    stderr: TextIO = sys.stderr,
+    server_options: bool = False,
+) -> tuple[CapturableArgumentParser, list[str], list[tuple[str, bool]]]:
+    """Define the options in the parser (by calling a bunch of methods that express/build our desired command-line flags).
+    Returns a tuple of:
+      a parser object, that can parse command line arguments to mypy (expected consumer: main's process_options),
+      a list of what flags are strict (expected consumer: docs' html_builder's _add_strict_list),
+      strict_flag_assignments (expected consumer: main's process_options)."""
     parser = CapturableArgumentParser(
         prog=program,
         usage=header,
@@ -491,8 +485,6 @@ def process_options(
         stdout=stdout,
         stderr=stderr,
     )
-    if sys.version_info >= (3, 14):
-        parser.color = True  # Set as init arg in 3.14
 
     strict_flag_names: list[str] = []
     strict_flag_assignments: list[tuple[str, bool]] = []
@@ -894,7 +886,7 @@ def add_invertible_flag(
         "--allow-redefinition-new",
         default=False,
         strict_flag=False,
-        help=argparse.SUPPRESS,  # This is still very experimental
+        help="Allow more flexible variable redefinition semantics (experimental)",
         group=strictness_group,
     )
 
@@ -911,7 +903,16 @@ def add_invertible_flag(
         "--strict-equality",
         default=False,
         strict_flag=True,
-        help="Prohibit equality, identity, and container checks for non-overlapping types",
+        help="Prohibit equality, identity, and container checks for non-overlapping types "
+        "(except `None`)",
+        group=strictness_group,
+    )
+
+    add_invertible_flag(
+        "--strict-equality-for-none",
+        default=False,
+        strict_flag=False,
+        help="Extend `--strict-equality` for `None` checks",
         group=strictness_group,
     )
 
@@ -1062,6 +1063,15 @@ def add_invertible_flag(
         action="store_true",
         help="Include fine-grained dependency information in the cache for the mypy daemon",
     )
+    incremental_group.add_argument(
+        "--fixed-format-cache",
+        action="store_true",
+        help=(
+            "Use experimental fast and compact fixed format cache"
+            if compilation_status == "yes"
+            else argparse.SUPPRESS
+        ),
+    )
     incremental_group.add_argument(
         "--skip-version-check",
         action="store_true",
@@ -1090,13 +1100,10 @@ def add_invertible_flag(
         help="Use a custom typing module",
     )
     internals_group.add_argument(
-        "--old-type-inference",
-        action="store_true",
-        help="Disable new experimental type inference algorithm",
+        "--old-type-inference", action="store_true", help=argparse.SUPPRESS
     )
-    # Deprecated reverse variant of the above.
     internals_group.add_argument(
-        "--new-type-inference", action="store_true", help=argparse.SUPPRESS
+        "--disable-expression-cache", action="store_true", help=argparse.SUPPRESS
     )
     parser.add_argument(
         "--enable-incomplete-feature",
@@ -1341,6 +1348,32 @@ def add_invertible_flag(
         dest="special-opts:files",
         help="Type-check given files or directories",
     )
+    return parser, strict_flag_names, strict_flag_assignments
+
+
+def process_options(
+    args: list[str],
+    stdout: TextIO | None = None,
+    stderr: TextIO | None = None,
+    require_targets: bool = True,
+    server_options: bool = False,
+    fscache: FileSystemCache | None = None,
+    program: str = "mypy",
+    header: str = HEADER,
+) -> tuple[list[BuildSource], Options]:
+    """Parse command line arguments.
+
+    If a FileSystemCache is passed in, and package_root options are given,
+    call fscache.set_package_root() to set the cache's package root.
+
+    Returns a tuple of: a list of source files, an Options collected from flags.
+    """
+    stdout = stdout if stdout is not None else sys.stdout
+    stderr = stderr if stderr is not None else sys.stderr
+
+    parser, _, strict_flag_assignments = define_options(
+        program, header, stdout, stderr, server_options
+    )
 
     # Parse arguments once into a dummy namespace so we can get the
     # filename for the config file and know if the user requested all strict options.
@@ -1486,12 +1519,6 @@ def set_strict_flags() -> None:
     if options.logical_deps:
         options.cache_fine_grained = True
 
-    if options.new_type_inference:
-        print(
-            "Warning: --new-type-inference flag is deprecated;"
-            " new type inference algorithm is already enabled by default"
-        )
-
     if options.strict_concatenate and not strict_option_set:
         print("Warning: --strict-concatenate is deprecated; use --extra-checks instead")
 
@@ -1525,11 +1552,9 @@ def set_strict_flags() -> None:
             targets.extend(p_targets)
         for m in special_opts.modules:
             targets.append(BuildSource(None, m, None))
-        return targets, options
     elif special_opts.command:
         options.build_type = BuildType.PROGRAM_TEXT
         targets = [BuildSource(None, None, "\n".join(special_opts.command))]
-        return targets, options
     else:
         try:
             targets = create_source_list(special_opts.files, options, fscache)
@@ -1538,7 +1563,7 @@ def set_strict_flags() -> None:
         # exceptions of different types.
         except InvalidSourceList as e2:
             fail(str(e2), stderr, options)
-        return targets, options
+    return targets, options
 
 
 def process_package_roots(
diff --git a/mypy/meet.py b/mypy/meet.py
index 7a44feabc10c..353af59367ad 100644
--- a/mypy/meet.py
+++ b/mypy/meet.py
@@ -116,8 +116,11 @@ def meet_types(s: Type, t: Type) -> ProperType:
 def narrow_declared_type(declared: Type, narrowed: Type) -> Type:
     """Return the declared type narrowed down to another type."""
     # TODO: check infinite recursion for aliases here.
-    if isinstance(narrowed, TypeGuardedType):  # type: ignore[misc]
-        # A type guard forces the new type even if it doesn't overlap the old.
+    if isinstance(narrowed, TypeGuardedType):
+        # A type guard forces the new type even if it doesn't overlap the old...
+        if is_proper_subtype(declared, narrowed.type_guard, ignore_promotions=True):
+            # ...unless it is a proper supertype of declared type.
+            return declared
         return narrowed.type_guard
 
     original_declared = declared
@@ -128,18 +131,28 @@ def narrow_declared_type(declared: Type, narrowed: Type) -> Type:
     if declared == narrowed:
         return original_declared
     if isinstance(declared, UnionType):
+        declared_items = declared.relevant_items()
+        if isinstance(narrowed, UnionType):
+            narrowed_items = narrowed.relevant_items()
+        else:
+            narrowed_items = [narrowed]
         return make_simplified_union(
             [
-                narrow_declared_type(x, narrowed)
-                for x in declared.relevant_items()
+                narrow_declared_type(d, n)
+                for d in declared_items
+                for n in narrowed_items
                 # This (ugly) special-casing is needed to support checking
                 # branches like this:
                 # x: Union[float, complex]
                 # if isinstance(x, int):
                 #     ...
+                # And assignments like this:
+                # x: float | None
+                # y: int | None
+                # x = y
                 if (
-                    is_overlapping_types(x, narrowed, ignore_promotions=True)
-                    or is_subtype(narrowed, x, ignore_promotions=False)
+                    is_overlapping_types(d, n, ignore_promotions=True)
+                    or is_subtype(n, d, ignore_promotions=False)
                 )
             ]
         )
@@ -281,6 +294,31 @@ def is_object(t: ProperType) -> bool:
     return isinstance(t, Instance) and t.type.fullname == "builtins.object"
 
 
+def is_none_typevarlike_overlap(t1: ProperType, t2: ProperType) -> bool:
+    return isinstance(t1, NoneType) and isinstance(t2, TypeVarLikeType)
+
+
+def is_none_object_overlap(t1: ProperType, t2: ProperType) -> bool:
+    return (
+        isinstance(t1, NoneType)
+        and isinstance(t2, Instance)
+        and t2.type.fullname == "builtins.object"
+    )
+
+
+def are_related_types(
+    left: Type, right: Type, *, proper_subtype: bool, ignore_promotions: bool
+) -> bool:
+    if proper_subtype:
+        return is_proper_subtype(
+            left, right, ignore_promotions=ignore_promotions
+        ) or is_proper_subtype(right, left, ignore_promotions=ignore_promotions)
+    else:
+        return is_subtype(left, right, ignore_promotions=ignore_promotions) or is_subtype(
+            right, left, ignore_promotions=ignore_promotions
+        )
+
+
 def is_overlapping_types(
     left: Type,
     right: Type,
@@ -298,35 +336,19 @@ def is_overlapping_types(
     positives), for example: None only overlaps with explicitly optional types, Any
     doesn't overlap with anything except object, we don't ignore positional argument names.
     """
-    if isinstance(left, TypeGuardedType) or isinstance(  # type: ignore[misc]
-        right, TypeGuardedType
-    ):
+    if isinstance(left, TypeGuardedType) or isinstance(right, TypeGuardedType):
         # A type guard forces the new type even if it doesn't overlap the old.
         return True
 
     if seen_types is None:
         seen_types = set()
-    if (left, right) in seen_types:
+    elif (left, right) in seen_types:
         return True
     if isinstance(left, TypeAliasType) and isinstance(right, TypeAliasType):
         seen_types.add((left, right))
 
     left, right = get_proper_types((left, right))
 
-    def _is_overlapping_types(left: Type, right: Type) -> bool:
-        """Encode the kind of overlapping check to perform.
-
-        This function mostly exists, so we don't have to repeat keyword arguments everywhere.
-        """
-        return is_overlapping_types(
-            left,
-            right,
-            ignore_promotions=ignore_promotions,
-            prohibit_none_typevar_overlap=prohibit_none_typevar_overlap,
-            overlap_for_overloads=overlap_for_overloads,
-            seen_types=seen_types.copy(),
-        )
-
     # We should never encounter this type.
     if isinstance(left, PartialType) or isinstance(right, PartialType):
         assert False, "Unexpectedly encountered partial type"
@@ -372,25 +394,13 @@ def _is_overlapping_types(left: Type, right: Type) -> bool:
     ):
         return True
 
-    def is_none_object_overlap(t1: Type, t2: Type) -> bool:
-        t1, t2 = get_proper_types((t1, t2))
-        return (
-            isinstance(t1, NoneType)
-            and isinstance(t2, Instance)
-            and t2.type.fullname == "builtins.object"
-        )
-
     if overlap_for_overloads:
         if is_none_object_overlap(left, right) or is_none_object_overlap(right, left):
             return False
 
-    def _is_subtype(left: Type, right: Type) -> bool:
-        if overlap_for_overloads:
-            return is_proper_subtype(left, right, ignore_promotions=ignore_promotions)
-        else:
-            return is_subtype(left, right, ignore_promotions=ignore_promotions)
-
-    if _is_subtype(left, right) or _is_subtype(right, left):
+    if are_related_types(
+        left, right, proper_subtype=overlap_for_overloads, ignore_promotions=ignore_promotions
+    ):
         return True
 
     # See the docstring for 'get_possible_variants' for more info on what the
@@ -409,14 +419,24 @@ def _is_subtype(left: Type, right: Type) -> bool:
     # If both types are singleton variants (and are not TypeVarLikes), we've hit the base case:
     # we skip these checks to avoid infinitely recursing.
 
-    def is_none_typevarlike_overlap(t1: Type, t2: Type) -> bool:
-        t1, t2 = get_proper_types((t1, t2))
-        return isinstance(t1, NoneType) and isinstance(t2, TypeVarLikeType)
-
     if prohibit_none_typevar_overlap:
         if is_none_typevarlike_overlap(left, right) or is_none_typevarlike_overlap(right, left):
             return False
 
+    def _is_overlapping_types(left: Type, right: Type) -> bool:
+        """Encode the kind of overlapping check to perform.
+
+        This function mostly exists, so we don't have to repeat keyword arguments everywhere.
+        """
+        return is_overlapping_types(
+            left,
+            right,
+            ignore_promotions=ignore_promotions,
+            prohibit_none_typevar_overlap=prohibit_none_typevar_overlap,
+            overlap_for_overloads=overlap_for_overloads,
+            seen_types=seen_types.copy(),
+        )
+
     if (
         len(left_possible) > 1
         or len(right_possible) > 1
@@ -472,27 +492,28 @@ def is_none_typevarlike_overlap(t1: Type, t2: Type) -> bool:
     if isinstance(left, TypeType) and isinstance(right, TypeType):
         return _is_overlapping_types(left.item, right.item)
 
-    def _type_object_overlap(left: Type, right: Type) -> bool:
-        """Special cases for type object types overlaps."""
-        # TODO: these checks are a bit in gray area, adjust if they cause problems.
-        left, right = get_proper_types((left, right))
-        # 1. Type[C] vs Callable[..., C] overlap even if the latter is not class object.
-        if isinstance(left, TypeType) and isinstance(right, CallableType):
-            return _is_overlapping_types(left.item, right.ret_type)
-        # 2. Type[C] vs Meta, where Meta is a metaclass for C.
-        if isinstance(left, TypeType) and isinstance(right, Instance):
-            if isinstance(left.item, Instance):
-                left_meta = left.item.type.metaclass_type
-                if left_meta is not None:
-                    return _is_overlapping_types(left_meta, right)
-                # builtins.type (default metaclass) overlaps with all metaclasses
-                return right.type.has_base("builtins.type")
-            elif isinstance(left.item, AnyType):
-                return right.type.has_base("builtins.type")
-        # 3. Callable[..., C] vs Meta is considered below, when we switch to fallbacks.
-        return False
-
     if isinstance(left, TypeType) or isinstance(right, TypeType):
+
+        def _type_object_overlap(left: Type, right: Type) -> bool:
+            """Special cases for type object types overlaps."""
+            # TODO: these checks are a bit in gray area, adjust if they cause problems.
+            left, right = get_proper_types((left, right))
+            # 1. Type[C] vs Callable[..., C] overlap even if the latter is not class object.
+            if isinstance(left, TypeType) and isinstance(right, CallableType):
+                return _is_overlapping_types(left.item, right.ret_type)
+            # 2. Type[C] vs Meta, where Meta is a metaclass for C.
+            if isinstance(left, TypeType) and isinstance(right, Instance):
+                if isinstance(left.item, Instance):
+                    left_meta = left.item.type.metaclass_type
+                    if left_meta is not None:
+                        return _is_overlapping_types(left_meta, right)
+                    # builtins.type (default metaclass) overlaps with all metaclasses
+                    return right.type.has_base("builtins.type")
+                elif isinstance(left.item, AnyType):
+                    return right.type.has_base("builtins.type")
+            # 3. Callable[..., C] vs Meta is considered below, when we switch to fallbacks.
+            return False
+
         return _type_object_overlap(left, right) or _type_object_overlap(right, left)
 
     if isinstance(left, Parameters) and isinstance(right, Parameters):
@@ -553,7 +574,9 @@ def _type_object_overlap(left: Type, right: Type) -> bool:
     if isinstance(left, Instance) and isinstance(right, Instance):
         # First we need to handle promotions and structural compatibility for instances
         # that came as fallbacks, so simply call is_subtype() to avoid code duplication.
-        if _is_subtype(left, right) or _is_subtype(right, left):
+        if are_related_types(
+            left, right, proper_subtype=overlap_for_overloads, ignore_promotions=ignore_promotions
+        ):
             return True
 
         if right.type.fullname == "builtins.int" and left.type.fullname in MYPYC_NATIVE_INT_NAMES:
diff --git a/mypy/message_registry.py b/mypy/message_registry.py
index 609f968a8c65..09004322aee9 100644
--- a/mypy/message_registry.py
+++ b/mypy/message_registry.py
@@ -239,6 +239,9 @@ def with_additional_msg(self, info: str) -> ErrorMessage:
 )
 CANNOT_MAKE_DELETABLE_FINAL: Final = ErrorMessage("Deletable attribute cannot be final")
 
+# Disjoint bases
+INCOMPATIBLE_DISJOINT_BASES: Final = ErrorMessage('Class "{}" has incompatible disjoint bases')
+
 # Enum
 ENUM_MEMBERS_ATTR_WILL_BE_OVERRIDDEN: Final = ErrorMessage(
     'Assigned "__members__" will be overridden by "Enum" internally'
@@ -253,7 +256,6 @@ def with_additional_msg(self, info: str) -> ErrorMessage:
     'Cannot override class variable (previously declared on base class "{}") with instance '
     "variable"
 )
-CLASS_VAR_WITH_TYPEVARS: Final = "ClassVar cannot contain type variables"
 CLASS_VAR_WITH_GENERIC_SELF: Final = "ClassVar cannot contain Self type in generic classes"
 CLASS_VAR_OUTSIDE_OF_CLASS: Final = "ClassVar can only be used for assignments in class body"
 
@@ -353,6 +355,10 @@ def with_additional_msg(self, info: str) -> ErrorMessage:
     "TypeVar constraint type cannot be parametrized by type variables", codes.MISC
 )
 
+TYPE_VAR_REDECLARED_IN_NESTED_CLASS: Final = ErrorMessage(
+    'Type variable "{}" is bound by an outer class', codes.VALID_TYPE
+)
+
 TYPE_ALIAS_WITH_YIELD_EXPRESSION: Final = ErrorMessage(
     "Yield expression cannot be used within a type alias", codes.SYNTAX
 )
diff --git a/mypy/messages.py b/mypy/messages.py
index 01414f1c7f2b..6329cad687f6 100644
--- a/mypy/messages.py
+++ b/mypy/messages.py
@@ -23,7 +23,13 @@
 from mypy import errorcodes as codes, message_registry
 from mypy.erasetype import erase_type
 from mypy.errorcodes import ErrorCode
-from mypy.errors import ErrorInfo, Errors, ErrorWatcher
+from mypy.errors import (
+    ErrorInfo,
+    Errors,
+    ErrorWatcher,
+    IterationDependentErrors,
+    IterationErrorWatcher,
+)
 from mypy.nodes import (
     ARG_NAMED,
     ARG_NAMED_OPT,
@@ -49,6 +55,7 @@
     SymbolTable,
     TypeInfo,
     Var,
+    get_func_def,
     reverse_builtin_aliases,
 )
 from mypy.operators import op_methods, op_methods_to_symbols
@@ -188,12 +195,14 @@ def filter_errors(
         filter_errors: bool | Callable[[str, ErrorInfo], bool] = True,
         save_filtered_errors: bool = False,
         filter_deprecated: bool = False,
+        filter_revealed_type: bool = False,
     ) -> ErrorWatcher:
         return ErrorWatcher(
             self.errors,
             filter_errors=filter_errors,
             save_filtered_errors=save_filtered_errors,
             filter_deprecated=filter_deprecated,
+            filter_revealed_type=filter_revealed_type,
         )
 
     def add_errors(self, errors: list[ErrorInfo]) -> None:
@@ -640,26 +649,11 @@ def incompatible_argument(
             else:
                 base = extract_type(name)
 
-            for method, op in op_methods_to_symbols.items():
-                for variant in method, "__r" + method[2:]:
-                    # FIX: do not rely on textual formatting
-                    if name.startswith(f'"{variant}" of'):
-                        if op == "in" or variant != method:
-                            # Reversed order of base/argument.
-                            return self.unsupported_operand_types(
-                                op, arg_type, base, context, code=codes.OPERATOR
-                            )
-                        else:
-                            return self.unsupported_operand_types(
-                                op, base, arg_type, context, code=codes.OPERATOR
-                            )
-
             if name.startswith('"__getitem__" of'):
                 return self.invalid_index_type(
                     arg_type, callee.arg_types[n - 1], base, context, code=codes.INDEX
                 )
-
-            if name.startswith('"__setitem__" of'):
+            elif name.startswith('"__setitem__" of'):
                 if n == 1:
                     return self.invalid_index_type(
                         arg_type, callee.arg_types[n - 1], base, context, code=codes.INDEX
@@ -675,6 +669,20 @@ def incompatible_argument(
                         message_registry.INCOMPATIBLE_TYPES_IN_ASSIGNMENT.with_additional_msg(info)
                     )
                     return self.fail(error_msg.value, context, code=error_msg.code)
+            elif name.startswith('"__'):
+                for method, op in op_methods_to_symbols.items():
+                    for variant in method, "__r" + method[2:]:
+                        # FIX: do not rely on textual formatting
+                        if name.startswith(f'"{variant}" of'):
+                            if op == "in" or variant != method:
+                                # Reversed order of base/argument.
+                                return self.unsupported_operand_types(
+                                    op, arg_type, base, context, code=codes.OPERATOR
+                                )
+                            else:
+                                return self.unsupported_operand_types(
+                                    op, base, arg_type, context, code=codes.OPERATOR
+                                )
 
             target = f"to {name} "
 
@@ -995,7 +1003,7 @@ def maybe_note_about_special_args(self, callee: CallableType, context: Context)
         if self.prefer_simple_messages():
             return
         # https://github.com/python/mypy/issues/11309
-        first_arg = callee.def_extras.get("first_arg")
+        first_arg = get_first_arg(callee)
         if first_arg and first_arg not in {"self", "cls", "mcs"}:
             self.note(
                 "Looks like the first special argument in a method "
@@ -1370,11 +1378,14 @@ def incompatible_type_application(
             self.fail(f"Type application has too few types ({s})", context)
 
     def could_not_infer_type_arguments(
-        self, callee_type: CallableType, n: int, context: Context
+        self, callee_type: CallableType, tv: TypeVarLikeType, context: Context
     ) -> None:
         callee_name = callable_name(callee_type)
-        if callee_name is not None and n > 0:
-            self.fail(f"Cannot infer type argument {n} of {callee_name}", context)
+        if callee_name is not None:
+            self.fail(
+                f"Cannot infer value of type parameter {format_type(tv, self.options)} of {callee_name}",
+                context,
+            )
             if callee_name == "<dict>":
                 # Invariance in key type causes more of these errors than we would want.
                 self.note(
@@ -1735,6 +1746,24 @@ def invalid_signature_for_special_method(
         )
 
     def reveal_type(self, typ: Type, context: Context) -> None:
+
+        # Search for an error watcher that modifies the "normal" behaviour (we do not
+        # rely on the normal `ErrorWatcher` filtering approach because we might need to
+        # collect the original types for a later unionised response):
+        for watcher in self.errors.get_watchers():
+            # The `reveal_type` statement should be ignored:
+            if watcher.filter_revealed_type:
+                return
+            # The `reveal_type` statement might be visited iteratively due to being
+            # placed in a loop or so. Hence, we collect the respective types of
+            # individual iterations so that we can report them all in one step later:
+            if isinstance(watcher, IterationErrorWatcher):
+                watcher.iteration_dependent_errors.revealed_types[
+                    (context.line, context.column, context.end_line, context.end_column)
+                ].append(typ)
+                return
+
+        # Nothing special here; just create the note:
         visitor = TypeStrVisitor(options=self.options)
         self.note(f'Revealed type is "{typ.accept(visitor)}"', context)
 
@@ -2402,13 +2431,13 @@ def format_long_tuple_type(self, typ: TupleType) -> str:
         """Format very long tuple type using an ellipsis notation"""
         item_cnt = len(typ.items)
         if item_cnt > MAX_TUPLE_ITEMS:
-            return "tuple[{}, {}, ... <{} more items>]".format(
+            return '"tuple[{}, {}, ... <{} more items>]"'.format(
                 format_type_bare(typ.items[0], self.options),
                 format_type_bare(typ.items[1], self.options),
                 str(item_cnt - 2),
             )
         else:
-            return format_type_bare(typ, self.options)
+            return format_type(typ, self.options)
 
     def generate_incompatible_tuple_error(
         self,
@@ -2478,18 +2507,21 @@ def match_statement_inexhaustive_match(self, typ: Type, context: Context) -> Non
             code=codes.EXHAUSTIVE_MATCH,
         )
 
+    def iteration_dependent_errors(self, iter_errors: IterationDependentErrors) -> None:
+        for error_info in iter_errors.yield_uselessness_error_infos():
+            self.fail(*error_info[:2], code=error_info[2])
+        for types, context in iter_errors.yield_revealed_type_infos():
+            self.reveal_type(mypy.typeops.make_simplified_union(types), context)
+
 
 def quote_type_string(type_string: str) -> str:
     """Quotes a type representation for use in messages."""
-    no_quote_regex = r"^<(tuple|union): \d+ items>$"
     if (
         type_string in ["Module", "overloaded function", "<deleted>"]
         or type_string.startswith("Module ")
-        or re.match(no_quote_regex, type_string) is not None
         or type_string.endswith("?")
     ):
-        # Messages are easier to read if these aren't quoted.  We use a
-        # regex to match strings with variable contents.
+        # These messages are easier to read if these aren't quoted.
         return type_string
     return f'"{type_string}"'
 
@@ -2903,10 +2935,11 @@ def format_single(arg: Type) -> str:
 
 def pretty_class_or_static_decorator(tp: CallableType) -> str | None:
     """Return @classmethod or @staticmethod, if any, for the given callable type."""
-    if tp.definition is not None and isinstance(tp.definition, SYMBOL_FUNCBASE_TYPES):
-        if tp.definition.is_class:
+    definition = get_func_def(tp)
+    if definition is not None and isinstance(definition, SYMBOL_FUNCBASE_TYPES):
+        if definition.is_class:
             return "@classmethod"
-        if tp.definition.is_static:
+        if definition.is_static:
             return "@staticmethod"
     return None
 
@@ -2956,12 +2989,13 @@ def [T <: int] f(self, x: int, y: T) -> None
             slash = True
 
     # If we got a "special arg" (i.e: self, cls, etc...), prepend it to the arg list
+    definition = get_func_def(tp)
     if (
-        isinstance(tp.definition, FuncDef)
-        and hasattr(tp.definition, "arguments")
+        isinstance(definition, FuncDef)
+        and hasattr(definition, "arguments")
         and not tp.from_concatenate
     ):
-        definition_arg_names = [arg.variable.name for arg in tp.definition.arguments]
+        definition_arg_names = [arg.variable.name for arg in definition.arguments]
         if (
             len(definition_arg_names) > len(tp.arg_names)
             and definition_arg_names[0]
@@ -2970,9 +3004,9 @@ def [T <: int] f(self, x: int, y: T) -> None
             if s:
                 s = ", " + s
             s = definition_arg_names[0] + s
-        s = f"{tp.definition.name}({s})"
+        s = f"{definition.name}({s})"
     elif tp.name:
-        first_arg = tp.def_extras.get("first_arg")
+        first_arg = get_first_arg(tp)
         if first_arg:
             if s:
                 s = ", " + s
@@ -3015,6 +3049,13 @@ def [T <: int] f(self, x: int, y: T) -> None
     return f"def {s}"
 
 
+def get_first_arg(tp: CallableType) -> str | None:
+    definition = get_func_def(tp)
+    if not isinstance(definition, FuncDef) or not definition.info or definition.is_static:
+        return None
+    return definition.original_first_arg
+
+
 def variance_string(variance: int) -> str:
     if variance == COVARIANT:
         return "covariant"
diff --git a/mypy/modulefinder.py b/mypy/modulefinder.py
index d159736078eb..d61c9ee3ec3f 100644
--- a/mypy/modulefinder.py
+++ b/mypy/modulefinder.py
@@ -796,6 +796,7 @@ def default_lib_path(
         custom_typeshed_dir = os.path.abspath(custom_typeshed_dir)
         typeshed_dir = os.path.join(custom_typeshed_dir, "stdlib")
         mypy_extensions_dir = os.path.join(custom_typeshed_dir, "stubs", "mypy-extensions")
+        mypy_native_dir = os.path.join(custom_typeshed_dir, "stubs", "mypy-native")
         versions_file = os.path.join(typeshed_dir, "VERSIONS")
         if not os.path.isdir(typeshed_dir) or not os.path.isfile(versions_file):
             print(
@@ -811,11 +812,13 @@ def default_lib_path(
             data_dir = auto
         typeshed_dir = os.path.join(data_dir, "typeshed", "stdlib")
         mypy_extensions_dir = os.path.join(data_dir, "typeshed", "stubs", "mypy-extensions")
+        mypy_native_dir = os.path.join(data_dir, "typeshed", "stubs", "mypy-native")
     path.append(typeshed_dir)
 
-    # Get mypy-extensions stubs from typeshed, since we treat it as an
-    # "internal" library, similar to typing and typing-extensions.
+    # Get mypy-extensions and mypy-native stubs from typeshed, since we treat them as
+    # "internal" libraries, similar to typing and typing-extensions.
     path.append(mypy_extensions_dir)
+    path.append(mypy_native_dir)
 
     # Add fallback path that can be used if we have a broken installation.
     if sys.platform != "win32":
diff --git a/mypy/nodes.py b/mypy/nodes.py
index 2cec4852f31c..9cfc61c80b3e 100644
--- a/mypy/nodes.py
+++ b/mypy/nodes.py
@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import json
 import os
 from abc import abstractmethod
 from collections import defaultdict
@@ -13,6 +14,33 @@
 from mypy_extensions import trait
 
 import mypy.strconv
+from mypy.cache import (
+    LITERAL_COMPLEX,
+    LITERAL_NONE,
+    Buffer,
+    Tag,
+    read_bool,
+    read_float,
+    read_int,
+    read_int_list,
+    read_int_opt,
+    read_literal,
+    read_str,
+    read_str_list,
+    read_str_opt,
+    read_str_opt_list,
+    read_tag,
+    write_bool,
+    write_int,
+    write_int_list,
+    write_int_opt,
+    write_literal,
+    write_str,
+    write_str_list,
+    write_str_opt,
+    write_str_opt_list,
+    write_tag,
+)
 from mypy.options import Options
 from mypy.util import is_sunder, is_typeshed_file, short_type
 from mypy.visitor import ExpressionVisitor, NodeVisitor, StatementVisitor
@@ -240,6 +268,13 @@ def deserialize(cls, data: JsonDict) -> SymbolNode:
             return method(data)
         raise NotImplementedError(f"unexpected .class {classname}")
 
+    def write(self, data: Buffer) -> None:
+        raise NotImplementedError(f"Cannot serialize {self.__class__.__name__} instance")
+
+    @classmethod
+    def read(cls, data: Buffer) -> SymbolNode:
+        raise NotImplementedError(f"Cannot deserialize {cls.__name__} instance")
+
 
 # Items: fullname, related symbol table node, surrounding type (if any)
 Definition: _TypeAlias = tuple[str, "SymbolTableNode", Optional["TypeInfo"]]
@@ -368,7 +403,7 @@ def serialize(self) -> JsonDict:
             "is_stub": self.is_stub,
             "path": self.path,
             "is_partial_stub_package": self.is_partial_stub_package,
-            "future_import_flags": list(self.future_import_flags),
+            "future_import_flags": sorted(self.future_import_flags),
         }
 
     @classmethod
@@ -384,6 +419,28 @@ def deserialize(cls, data: JsonDict) -> MypyFile:
         tree.future_import_flags = set(data["future_import_flags"])
         return tree
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, MYPY_FILE)
+        write_str(data, self._fullname)
+        self.names.write(data, self._fullname)
+        write_bool(data, self.is_stub)
+        write_str(data, self.path)
+        write_bool(data, self.is_partial_stub_package)
+        write_str_list(data, sorted(self.future_import_flags))
+
+    @classmethod
+    def read(cls, data: Buffer) -> MypyFile:
+        assert read_tag(data) == MYPY_FILE
+        tree = MypyFile([], [])
+        tree._fullname = read_str(data)
+        tree.names = SymbolTable.read(data)
+        tree.is_stub = read_bool(data)
+        tree.path = read_str(data)
+        tree.is_partial_stub_package = read_bool(data)
+        tree.future_import_flags = set(read_str_list(data))
+        tree.is_cache_skeleton = True
+        return tree
+
 
 class ImportBase(Statement):
     """Base class for all import statements."""
@@ -508,6 +565,8 @@ def __init__(self) -> None:
         self.info = FUNC_NO_INFO
         self.is_property = False
         self.is_class = False
+        # Is this a `@staticmethod` (explicit or implicit)?
+        # Note: use has_self_or_cls_argument to check if there is `self` or `cls` argument
         self.is_static = False
         self.is_final = False
         self.is_explicit_override = False
@@ -524,6 +583,15 @@ def name(self) -> str:
     def fullname(self) -> str:
         return self._fullname
 
+    @property
+    def has_self_or_cls_argument(self) -> bool:
+        """If used as a method, does it have an argument for method binding (`self`, `cls`)?
+
+        This is true for `__new__` even though `__new__` does not undergo method binding,
+        because we still usually assume that `cls` corresponds to the enclosing class.
+        """
+        return not self.is_static or self.name == "__new__"
+
 
 OverloadPart: _TypeAlias = Union["FuncDef", "Decorator"]
 
@@ -584,12 +652,14 @@ def is_trivial_self(self) -> bool:
         """
         if self._is_trivial_self is not None:
             return self._is_trivial_self
-        for item in self.items:
+        for i, item in enumerate(self.items):
+            # Note: bare @property is removed in visit_decorator().
+            trivial = 1 if i > 0 or not self.is_property else 0
             if isinstance(item, FuncDef):
                 if not item.is_trivial_self:
                     self._is_trivial_self = False
                     return False
-            elif item.decorators or not item.func.is_trivial_self:
+            elif len(item.decorators) > trivial or not item.func.is_trivial_self:
                 self._is_trivial_self = False
                 return False
         self._is_trivial_self = True
@@ -643,6 +713,41 @@ def deserialize(cls, data: JsonDict) -> OverloadedFuncDef:
         # NOTE: res.info will be set in the fixup phase.
         return res
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, OVERLOADED_FUNC_DEF)
+        write_int(data, len(self.items))
+        for item in self.items:
+            item.write(data)
+        mypy.types.write_type_opt(data, self.type)
+        write_str(data, self._fullname)
+        if self.impl is None:
+            write_bool(data, False)
+        else:
+            write_bool(data, True)
+            self.impl.write(data)
+        write_flags(data, self, FUNCBASE_FLAGS)
+        write_str_opt(data, self.deprecated)
+        write_int_opt(data, self.setter_index)
+
+    @classmethod
+    def read(cls, data: Buffer) -> OverloadedFuncDef:
+        res = OverloadedFuncDef([read_overload_part(data) for _ in range(read_int(data))])
+        typ = mypy.types.read_type_opt(data)
+        if typ is not None:
+            assert isinstance(typ, mypy.types.ProperType)
+            res.type = typ
+        res._fullname = read_str(data)
+        if read_bool(data):
+            res.impl = read_overload_part(data)
+            # set line for empty overload items, as not set in __init__
+            if len(res.items) > 0:
+                res.set_line(res.impl.line)
+        read_flags(data, res, FUNCBASE_FLAGS)
+        res.deprecated = read_str_opt(data)
+        res.setter_index = read_int_opt(data)
+        # NOTE: res.info will be set in the fixup phase.
+        return res
+
     def is_dynamic(self) -> bool:
         return all(item.is_dynamic() for item in self.items)
 
@@ -805,11 +910,13 @@ class FuncDef(FuncItem, SymbolNode, Statement):
         "original_def",
         "is_trivial_body",
         "is_trivial_self",
+        "has_self_attr_def",
         "is_mypy_only",
         # Present only when a function is decorated with @typing.dataclass_transform or similar
         "dataclass_transform_spec",
         "docstring",
         "deprecated",
+        "original_first_arg",
     )
 
     __match_args__ = ("name", "arguments", "type", "body")
@@ -842,6 +949,14 @@ def __init__(
         # the majority). In cases where self is not annotated and there are no Self
         # in the signature we can simply drop the first argument.
         self.is_trivial_self = False
+        # Keep track of functions where self attributes are defined.
+        self.has_self_attr_def = False
+        # This is needed because for positional-only arguments the name is set to None,
+        # but we sometimes still want to show it in error messages.
+        if arguments:
+            self.original_first_arg: str | None = arguments[0].variable.name
+        else:
+            self.original_first_arg = None
 
     @property
     def name(self) -> str:
@@ -873,6 +988,7 @@ def serialize(self) -> JsonDict:
                 else self.dataclass_transform_spec.serialize()
             ),
             "deprecated": self.deprecated,
+            "original_first_arg": self.original_first_arg,
         }
 
     @classmethod
@@ -893,7 +1009,8 @@ def deserialize(cls, data: JsonDict) -> FuncDef:
         set_flags(ret, data["flags"])
         # NOTE: ret.info is set in the fixup phase.
         ret.arg_names = data["arg_names"]
-        ret.arg_kinds = [ArgKind(x) for x in data["arg_kinds"]]
+        ret.original_first_arg = data.get("original_first_arg")
+        ret.arg_kinds = [ARG_KINDS[x] for x in data["arg_kinds"]]
         ret.abstract_status = data["abstract_status"]
         ret.dataclass_transform_spec = (
             DataclassTransformSpec.deserialize(data["dataclass_transform_spec"])
@@ -907,6 +1024,46 @@ def deserialize(cls, data: JsonDict) -> FuncDef:
         del ret.min_args
         return ret
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, FUNC_DEF)
+        write_str(data, self._name)
+        mypy.types.write_type_opt(data, self.type)
+        write_str(data, self._fullname)
+        write_flags(data, self, FUNCDEF_FLAGS)
+        write_str_opt_list(data, self.arg_names)
+        write_int_list(data, [int(ak.value) for ak in self.arg_kinds])
+        write_int(data, self.abstract_status)
+        if self.dataclass_transform_spec is None:
+            write_bool(data, False)
+        else:
+            write_bool(data, True)
+            self.dataclass_transform_spec.write(data)
+        write_str_opt(data, self.deprecated)
+        write_str_opt(data, self.original_first_arg)
+
+    @classmethod
+    def read(cls, data: Buffer) -> FuncDef:
+        name = read_str(data)
+        typ: mypy.types.FunctionLike | None = None
+        if read_bool(data):
+            typ = mypy.types.read_function_like(data)
+        ret = FuncDef(name, [], Block([]), typ)
+        ret._fullname = read_str(data)
+        read_flags(data, ret, FUNCDEF_FLAGS)
+        # NOTE: ret.info is set in the fixup phase.
+        ret.arg_names = read_str_opt_list(data)
+        ret.arg_kinds = [ARG_KINDS[ak] for ak in read_int_list(data)]
+        ret.abstract_status = read_int(data)
+        if read_bool(data):
+            ret.dataclass_transform_spec = DataclassTransformSpec.read(data)
+        ret.deprecated = read_str_opt(data)
+        ret.original_first_arg = read_str_opt(data)
+        # Leave these uninitialized so that future uses will trigger an error
+        del ret.arguments
+        del ret.max_pos
+        del ret.min_args
+        return ret
+
 
 # All types that are both SymbolNodes and FuncBases. See the FuncBase
 # docstring for the rationale.
@@ -979,6 +1136,22 @@ def deserialize(cls, data: JsonDict) -> Decorator:
         dec.is_overload = data["is_overload"]
         return dec
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, DECORATOR)
+        self.func.write(data)
+        self.var.write(data)
+        write_bool(data, self.is_overload)
+
+    @classmethod
+    def read(cls, data: Buffer) -> Decorator:
+        assert read_tag(data) == FUNC_DEF
+        func = FuncDef.read(data)
+        assert read_tag(data) == VAR
+        var = Var.read(data)
+        dec = Decorator(func, [], var)
+        dec.is_overload = read_bool(data)
+        return dec
+
     def is_dynamic(self) -> bool:
         return self.func.is_dynamic()
 
@@ -1155,6 +1328,35 @@ def deserialize(cls, data: JsonDict) -> Var:
         v.final_value = data.get("final_value")
         return v
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, VAR)
+        write_str(data, self._name)
+        mypy.types.write_type_opt(data, self.type)
+        mypy.types.write_type_opt(data, self.setter_type)
+        write_str(data, self._fullname)
+        write_flags(data, self, VAR_FLAGS)
+        write_literal(data, self.final_value)
+
+    @classmethod
+    def read(cls, data: Buffer) -> Var:
+        name = read_str(data)
+        typ = mypy.types.read_type_opt(data)
+        v = Var(name, typ)
+        setter_type: mypy.types.CallableType | None = None
+        if read_bool(data):
+            assert read_tag(data) == mypy.types.CALLABLE_TYPE
+            setter_type = mypy.types.CallableType.read(data)
+        v.setter_type = setter_type
+        v.is_ready = False  # Override True default set in __init__
+        v._fullname = read_str(data)
+        read_flags(data, v, VAR_FLAGS)
+        marker = read_tag(data)
+        if marker == LITERAL_COMPLEX:
+            v.final_value = complex(read_float(data), read_float(data))
+        elif marker != LITERAL_NONE:
+            v.final_value = read_literal(data, marker)
+        return v
+
 
 class ClassDef(Statement):
     """Class definition"""
@@ -1265,6 +1467,22 @@ def deserialize(cls, data: JsonDict) -> ClassDef:
         res.fullname = data["fullname"]
         return res
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, CLASS_DEF)
+        write_str(data, self.name)
+        mypy.types.write_type_list(data, self.type_vars)
+        write_str(data, self.fullname)
+
+    @classmethod
+    def read(cls, data: Buffer) -> ClassDef:
+        res = ClassDef(
+            read_str(data),
+            Block([]),
+            [mypy.types.read_type_var_like(data) for _ in range(read_int(data))],
+        )
+        res.fullname = read_str(data)
+        return res
+
 
 class GlobalDecl(Statement):
     """Declaration global x, y, ..."""
@@ -1991,6 +2209,8 @@ def is_star(self) -> bool:
 ARG_STAR2: Final = ArgKind.ARG_STAR2
 ARG_NAMED_OPT: Final = ArgKind.ARG_NAMED_OPT
 
+ARG_KINDS: Final = (ARG_POS, ARG_OPT, ARG_STAR, ARG_NAMED, ARG_STAR2, ARG_NAMED_OPT)
+
 
 class CallExpr(Expression):
     """Call expression.
@@ -2680,6 +2900,26 @@ def deserialize(cls, data: JsonDict) -> TypeVarExpr:
             data["variance"],
         )
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, TYPE_VAR_EXPR)
+        write_str(data, self._name)
+        write_str(data, self._fullname)
+        mypy.types.write_type_list(data, self.values)
+        self.upper_bound.write(data)
+        self.default.write(data)
+        write_int(data, self.variance)
+
+    @classmethod
+    def read(cls, data: Buffer) -> TypeVarExpr:
+        return TypeVarExpr(
+            read_str(data),
+            read_str(data),
+            mypy.types.read_type_list(data),
+            mypy.types.read_type(data),
+            mypy.types.read_type(data),
+            read_int(data),
+        )
+
 
 class ParamSpecExpr(TypeVarLikeExpr):
     __slots__ = ()
@@ -2710,6 +2950,24 @@ def deserialize(cls, data: JsonDict) -> ParamSpecExpr:
             data["variance"],
         )
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, PARAM_SPEC_EXPR)
+        write_str(data, self._name)
+        write_str(data, self._fullname)
+        self.upper_bound.write(data)
+        self.default.write(data)
+        write_int(data, self.variance)
+
+    @classmethod
+    def read(cls, data: Buffer) -> ParamSpecExpr:
+        return ParamSpecExpr(
+            read_str(data),
+            read_str(data),
+            mypy.types.read_type(data),
+            mypy.types.read_type(data),
+            read_int(data),
+        )
+
 
 class TypeVarTupleExpr(TypeVarLikeExpr):
     """Type variable tuple expression TypeVarTuple(...)."""
@@ -2760,6 +3018,28 @@ def deserialize(cls, data: JsonDict) -> TypeVarTupleExpr:
             data["variance"],
         )
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, TYPE_VAR_TUPLE_EXPR)
+        self.tuple_fallback.write(data)
+        write_str(data, self._name)
+        write_str(data, self._fullname)
+        self.upper_bound.write(data)
+        self.default.write(data)
+        write_int(data, self.variance)
+
+    @classmethod
+    def read(cls, data: Buffer) -> TypeVarTupleExpr:
+        assert read_tag(data) == mypy.types.INSTANCE
+        fallback = mypy.types.Instance.read(data)
+        return TypeVarTupleExpr(
+            read_str(data),
+            read_str(data),
+            mypy.types.read_type(data),
+            fallback,
+            mypy.types.read_type(data),
+            read_int(data),
+        )
+
 
 class TypeAliasExpr(Expression):
     """Type alias expression (rvalue)."""
@@ -2977,6 +3257,7 @@ class is generic then it will be a type constructor of higher kind.
         "_mro_refs",
         "bad_mro",
         "is_final",
+        "is_disjoint_base",
         "declared_metaclass",
         "metaclass_type",
         "names",
@@ -3011,6 +3292,7 @@ class is generic then it will be a type constructor of higher kind.
         "dataclass_transform_spec",
         "is_type_check_only",
         "deprecated",
+        "type_object_type",
     )
 
     _fullname: str  # Fully qualified name
@@ -3027,6 +3309,7 @@ class is generic then it will be a type constructor of higher kind.
     _mro_refs: list[str] | None
     bad_mro: bool  # Could not construct full MRO
     is_final: bool
+    is_disjoint_base: bool
 
     declared_metaclass: mypy.types.Instance | None
     metaclass_type: mypy.types.Instance | None
@@ -3167,6 +3450,10 @@ class is generic then it will be a type constructor of higher kind.
     # The type's deprecation message (in case it is deprecated)
     deprecated: str | None
 
+    # Cached value of class constructor type, i.e. the type of class object when it
+    # appears in runtime context.
+    type_object_type: mypy.types.FunctionLike | None
+
     FLAGS: Final = [
         "is_abstract",
         "is_enum",
@@ -3177,6 +3464,7 @@ class is generic then it will be a type constructor of higher kind.
         "is_protocol",
         "runtime_protocol",
         "is_final",
+        "is_disjoint_base",
         "is_intersection",
     ]
 
@@ -3209,6 +3497,7 @@ def __init__(self, names: SymbolTable, defn: ClassDef, module_name: str) -> None
         self.type_var_tuple_suffix: int | None = None
         self.add_type_vars()
         self.is_final = False
+        self.is_disjoint_base = False
         self.is_enum = False
         self.fallback_to_any = False
         self.meta_fallback_to_any = False
@@ -3225,6 +3514,7 @@ def __init__(self, names: SymbolTable, defn: ClassDef, module_name: str) -> None
         self.dataclass_transform_spec = None
         self.is_type_check_only = False
         self.deprecated = None
+        self.type_object_type = None
 
     def add_type_vars(self) -> None:
         self.has_type_var_tuple_type = False
@@ -3371,14 +3661,61 @@ def calculate_metaclass_type(self) -> mypy.types.Instance | None:
             return declared
         if self._fullname == "builtins.type":
             return mypy.types.Instance(self, [])
-        candidates = [
-            s.declared_metaclass
-            for s in self.mro
-            if s.declared_metaclass is not None and s.declared_metaclass.type is not None
-        ]
-        for c in candidates:
-            if all(other.type in c.type.mro for other in candidates):
-                return c
+
+        winner = declared
+        for super_class in self.mro[1:]:
+            super_meta = super_class.declared_metaclass
+            if super_meta is None or super_meta.type is None:
+                continue
+            if winner is None:
+                winner = super_meta
+                continue
+            if winner.type.has_base(super_meta.type.fullname):
+                continue
+            if super_meta.type.has_base(winner.type.fullname):
+                winner = super_meta
+                continue
+            # metaclass conflict
+            winner = None
+            break
+
+        return winner
+
+    def explain_metaclass_conflict(self) -> str | None:
+        # Compare to logic in calculate_metaclass_type
+        declared = self.declared_metaclass
+        if declared is not None and not declared.type.has_base("builtins.type"):
+            return None
+        if self._fullname == "builtins.type":
+            return None
+
+        winner = declared
+        if declared is None:
+            resolution_steps = []
+        else:
+            resolution_steps = [f'"{declared.type.fullname}" (metaclass of "{self.fullname}")']
+        for super_class in self.mro[1:]:
+            super_meta = super_class.declared_metaclass
+            if super_meta is None or super_meta.type is None:
+                continue
+            if winner is None:
+                winner = super_meta
+                resolution_steps.append(
+                    f'"{winner.type.fullname}" (metaclass of "{super_class.fullname}")'
+                )
+                continue
+            if winner.type.has_base(super_meta.type.fullname):
+                continue
+            if super_meta.type.has_base(winner.type.fullname):
+                winner = super_meta
+                resolution_steps.append(
+                    f'"{winner.type.fullname}" (metaclass of "{super_class.fullname}")'
+                )
+                continue
+            # metaclass conflict
+            conflict = f'"{super_meta.type.fullname}" (metaclass of "{super_class.fullname}")'
+            return f"{' > '.join(resolution_steps)} conflicts with {conflict}"
+
         return None
 
     def is_metaclass(self, *, precise: bool = False) -> bool:
@@ -3413,6 +3750,8 @@ def update_tuple_type(self, typ: mypy.types.TupleType) -> None:
             self.special_alias = alias
         else:
             self.special_alias.target = alias.target
+            # Invalidate recursive status cache in case it was previously set.
+            self.special_alias._is_recursive = None
 
     def update_typeddict_type(self, typ: mypy.types.TypedDictType) -> None:
         """Update typeddict_type and special_alias as needed."""
@@ -3422,6 +3761,8 @@ def update_typeddict_type(self, typ: mypy.types.TypedDictType) -> None:
             self.special_alias = alias
         else:
             self.special_alias.target = alias.target
+            # Invalidate recursive status cache in case it was previously set.
+            self.special_alias._is_recursive = None
 
     def __str__(self) -> str:
         """Return a string representation of the type.
@@ -3510,7 +3851,6 @@ def deserialize(cls, data: JsonDict) -> TypeInfo:
         module_name = data["module_name"]
         ti = TypeInfo(names, defn, module_name)
         ti._fullname = data["fullname"]
-        # TODO: Is there a reason to reconstruct ti.subtypes?
         ti.abstract_attributes = [(attr[0], attr[1]) for attr in data["abstract_attributes"]]
         ti.type_vars = data["type_vars"]
         ti.has_param_spec_type = data["has_param_spec_type"]
@@ -3570,6 +3910,99 @@ def deserialize(cls, data: JsonDict) -> TypeInfo:
         ti.deprecated = data.get("deprecated")
         return ti
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, TYPE_INFO)
+        self.names.write(data, self.fullname)
+        self.defn.write(data)
+        write_str(data, self.module_name)
+        write_str(data, self.fullname)
+        write_str_list(data, [a for a, _ in self.abstract_attributes])
+        write_int_list(data, [s for _, s in self.abstract_attributes])
+        write_str_list(data, self.type_vars)
+        write_bool(data, self.has_param_spec_type)
+        mypy.types.write_type_list(data, self.bases)
+        write_str_list(data, [c.fullname for c in self.mro])
+        mypy.types.write_type_list(data, self._promote)
+        mypy.types.write_type_opt(data, self.alt_promote)
+        mypy.types.write_type_opt(data, self.declared_metaclass)
+        mypy.types.write_type_opt(data, self.metaclass_type)
+        mypy.types.write_type_opt(data, self.tuple_type)
+        mypy.types.write_type_opt(data, self.typeddict_type)
+        write_flags(data, self, TypeInfo.FLAGS)
+        write_str(data, json.dumps(self.metadata))
+        if self.slots is None:
+            write_bool(data, False)
+        else:
+            write_bool(data, True)
+            write_str_list(data, sorted(self.slots))
+        write_str_list(data, self.deletable_attributes)
+        mypy.types.write_type_opt(data, self.self_type)
+        if self.dataclass_transform_spec is None:
+            write_bool(data, False)
+        else:
+            write_bool(data, True)
+            self.dataclass_transform_spec.write(data)
+        write_str_opt(data, self.deprecated)
+
+    @classmethod
+    def read(cls, data: Buffer) -> TypeInfo:
+        names = SymbolTable.read(data)
+        assert read_tag(data) == CLASS_DEF
+        defn = ClassDef.read(data)
+        module_name = read_str(data)
+        ti = TypeInfo(names, defn, module_name)
+        ti._fullname = read_str(data)
+        attrs = read_str_list(data)
+        statuses = read_int_list(data)
+        ti.abstract_attributes = list(zip(attrs, statuses))
+        ti.type_vars = read_str_list(data)
+        ti.has_param_spec_type = read_bool(data)
+        ti.bases = []
+        for _ in range(read_int(data)):
+            assert read_tag(data) == mypy.types.INSTANCE
+            ti.bases.append(mypy.types.Instance.read(data))
+        # NOTE: ti.mro will be set in the fixup phase based on these
+        # names.  The reason we need to store the mro instead of just
+        # recomputing it from base classes has to do with a subtle
+        # point about fine-grained incremental: the cache files might
+        # not be loaded until after a class in the mro has changed its
+        # bases, which causes the mro to change. If we recomputed our
+        # mro, we would compute the *new* mro, which leaves us with no
+        # way to detect that the mro has changed! Thus, we need to make
+        # sure to load the original mro so that once the class is
+        # rechecked, it can tell that the mro has changed.
+        ti._mro_refs = read_str_list(data)
+        ti._promote = cast(list[mypy.types.ProperType], mypy.types.read_type_list(data))
+        if read_bool(data):
+            assert read_tag(data) == mypy.types.INSTANCE
+            ti.alt_promote = mypy.types.Instance.read(data)
+        if read_bool(data):
+            assert read_tag(data) == mypy.types.INSTANCE
+            ti.declared_metaclass = mypy.types.Instance.read(data)
+        if read_bool(data):
+            assert read_tag(data) == mypy.types.INSTANCE
+            ti.metaclass_type = mypy.types.Instance.read(data)
+        if read_bool(data):
+            assert read_tag(data) == mypy.types.TUPLE_TYPE
+            ti.tuple_type = mypy.types.TupleType.read(data)
+        if read_bool(data):
+            assert read_tag(data) == mypy.types.TYPED_DICT_TYPE
+            ti.typeddict_type = mypy.types.TypedDictType.read(data)
+        read_flags(data, ti, TypeInfo.FLAGS)
+        metadata = read_str(data)
+        if metadata != "{}":
+            ti.metadata = json.loads(metadata)
+        if read_bool(data):
+            ti.slots = set(read_str_list(data))
+        ti.deletable_attributes = read_str_list(data)
+        if read_bool(data):
+            assert read_tag(data) == mypy.types.TYPE_VAR_TYPE
+            ti.self_type = mypy.types.TypeVarType.read(data)
+        if read_bool(data):
+            ti.dataclass_transform_spec = DataclassTransformSpec.read(data)
+        ti.deprecated = read_str_opt(data)
+        return ti
+
 
 class FakeInfo(TypeInfo):
     __slots__ = ("msg",)
@@ -3798,6 +4231,9 @@ def fullname(self) -> str:
     def has_param_spec_type(self) -> bool:
         return any(isinstance(v, mypy.types.ParamSpecType) for v in self.alias_tvars)
 
+    def accept(self, visitor: NodeVisitor[T]) -> T:
+        return visitor.visit_type_alias(self)
+
     def serialize(self) -> JsonDict:
         data: JsonDict = {
             ".class": "TypeAlias",
@@ -3812,9 +4248,6 @@ def serialize(self) -> JsonDict:
         }
         return data
 
-    def accept(self, visitor: NodeVisitor[T]) -> T:
-        return visitor.visit_type_alias(self)
-
     @classmethod
     def deserialize(cls, data: JsonDict) -> TypeAlias:
         assert data[".class"] == "TypeAlias"
@@ -3838,6 +4271,33 @@ def deserialize(cls, data: JsonDict) -> TypeAlias:
             python_3_12_type_alias=python_3_12_type_alias,
         )
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, TYPE_ALIAS)
+        write_str(data, self._fullname)
+        self.target.write(data)
+        mypy.types.write_type_list(data, self.alias_tvars)
+        write_int(data, self.line)
+        write_int(data, self.column)
+        write_bool(data, self.no_args)
+        write_bool(data, self.normalized)
+        write_bool(data, self.python_3_12_type_alias)
+
+    @classmethod
+    def read(cls, data: Buffer) -> TypeAlias:
+        fullname = read_str(data)
+        target = mypy.types.read_type(data)
+        alias_tvars = [mypy.types.read_type_var_like(data) for _ in range(read_int(data))]
+        return TypeAlias(
+            target,
+            fullname,
+            read_int(data),
+            read_int(data),
+            alias_tvars=alias_tvars,
+            no_args=read_bool(data),
+            normalized=read_bool(data),
+            python_3_12_type_alias=read_bool(data),
+        )
+
 
 class PlaceholderNode(SymbolNode):
     """Temporary symbol node that will later become a real SymbolNode.
@@ -4096,6 +4556,49 @@ def deserialize(cls, data: JsonDict) -> SymbolTableNode:
             stnode.plugin_generated = data["plugin_generated"]
         return stnode
 
+    def write(self, data: Buffer, prefix: str, name: str) -> None:
+        write_int(data, self.kind)
+        write_bool(data, self.module_hidden)
+        write_bool(data, self.module_public)
+        write_bool(data, self.implicit)
+        write_bool(data, self.plugin_generated)
+
+        cross_ref = None
+        if isinstance(self.node, MypyFile):
+            cross_ref = self.node.fullname
+        else:
+            assert self.node is not None, f"{prefix}:{name}"
+            if prefix is not None:
+                fullname = self.node.fullname
+                if (
+                    "." in fullname
+                    and fullname != prefix + "." + name
+                    and not (isinstance(self.node, Var) and self.node.from_module_getattr)
+                ):
+                    assert not isinstance(
+                        self.node, PlaceholderNode
+                    ), f"Definition of {fullname} is unexpectedly incomplete"
+                    cross_ref = fullname
+
+        write_str_opt(data, cross_ref)
+        if cross_ref is None:
+            assert self.node is not None
+            self.node.write(data)
+
+    @classmethod
+    def read(cls, data: Buffer) -> SymbolTableNode:
+        sym = SymbolTableNode(read_int(data), None)
+        sym.module_hidden = read_bool(data)
+        sym.module_public = read_bool(data)
+        sym.implicit = read_bool(data)
+        sym.plugin_generated = read_bool(data)
+        cross_ref = read_str_opt(data)
+        if cross_ref is None:
+            sym.node = read_symbol(data)
+        else:
+            sym.cross_ref = cross_ref
+        return sym
+
 
 class SymbolTable(dict[str, SymbolTableNode]):
     """Static representation of a namespace dictionary.
@@ -4147,6 +4650,29 @@ def deserialize(cls, data: JsonDict) -> SymbolTable:
                 st[key] = SymbolTableNode.deserialize(value)
         return st
 
+    def write(self, data: Buffer, fullname: str) -> None:
+        size = 0
+        for key, value in self.items():
+            # Skip __builtins__: it's a reference to the builtins
+            # module that gets added to every module by
+            # SemanticAnalyzerPass2.visit_file(), but it shouldn't be
+            # accessed by users of the module.
+            if key == "__builtins__" or value.no_serialize:
+                continue
+            size += 1
+        write_int(data, size)
+        for key in sorted(self):
+            value = self[key]
+            if key == "__builtins__" or value.no_serialize:
+                continue
+            write_str(data, key)
+            value.write(data, fullname, key)
+
+    @classmethod
+    def read(cls, data: Buffer) -> SymbolTable:
+        size = read_int(data)
+        return SymbolTable([(read_str(data), SymbolTableNode.read(data)) for _ in range(size)])
+
 
 class DataclassTransformSpec:
     """Specifies how a dataclass-like transform should be applied. The fields here are based on the
@@ -4197,6 +4723,23 @@ def deserialize(cls, data: JsonDict) -> DataclassTransformSpec:
             field_specifiers=tuple(data.get("field_specifiers", [])),
         )
 
+    def write(self, data: Buffer) -> None:
+        write_bool(data, self.eq_default)
+        write_bool(data, self.order_default)
+        write_bool(data, self.kw_only_default)
+        write_bool(data, self.frozen_default)
+        write_str_list(data, self.field_specifiers)
+
+    @classmethod
+    def read(cls, data: Buffer) -> DataclassTransformSpec:
+        return DataclassTransformSpec(
+            eq_default=read_bool(data),
+            order_default=read_bool(data),
+            kw_only_default=read_bool(data),
+            frozen_default=read_bool(data),
+            field_specifiers=tuple(read_str_list(data)),
+        )
+
 
 def get_flags(node: Node, names: list[str]) -> list[str]:
     return [name for name in names if getattr(node, name)]
@@ -4207,6 +4750,17 @@ def set_flags(node: Node, flags: list[str]) -> None:
         setattr(node, name, True)
 
 
+def write_flags(data: Buffer, node: SymbolNode, flags: list[str]) -> None:
+    for flag in flags:
+        write_bool(data, getattr(node, flag))
+
+
+def read_flags(data: Buffer, node: SymbolNode, flags: list[str]) -> None:
+    for flag in flags:
+        if read_bool(data):
+            setattr(node, flag, True)
+
+
 def get_member_expr_fullname(expr: MemberExpr) -> str | None:
     """Return the qualified name representation of a member expression.
 
@@ -4296,6 +4850,13 @@ def is_final_node(node: SymbolNode | None) -> bool:
     return isinstance(node, (Var, FuncDef, OverloadedFuncDef, Decorator)) and node.is_final
 
 
+def get_func_def(typ: mypy.types.CallableType) -> SymbolNode | None:
+    definition = typ.definition
+    if isinstance(definition, Decorator):
+        definition = definition.func
+    return definition
+
+
 def local_definitions(
     names: SymbolTable, name_prefix: str, info: TypeInfo | None = None
 ) -> Iterator[Definition]:
@@ -4315,3 +4876,49 @@ def local_definitions(
             yield fullname, symnode, info
             if isinstance(node, TypeInfo):
                 yield from local_definitions(node.names, fullname, node)
+
+
+MYPY_FILE: Final[Tag] = 0
+OVERLOADED_FUNC_DEF: Final[Tag] = 1
+FUNC_DEF: Final[Tag] = 2
+DECORATOR: Final[Tag] = 3
+VAR: Final[Tag] = 4
+TYPE_VAR_EXPR: Final[Tag] = 5
+PARAM_SPEC_EXPR: Final[Tag] = 6
+TYPE_VAR_TUPLE_EXPR: Final[Tag] = 7
+TYPE_INFO: Final[Tag] = 8
+TYPE_ALIAS: Final[Tag] = 9
+CLASS_DEF: Final[Tag] = 10
+
+
+def read_symbol(data: Buffer) -> mypy.nodes.SymbolNode:
+    tag = read_tag(data)
+    # The branches here are ordered manually by type "popularity".
+    if tag == VAR:
+        return mypy.nodes.Var.read(data)
+    if tag == FUNC_DEF:
+        return mypy.nodes.FuncDef.read(data)
+    if tag == DECORATOR:
+        return mypy.nodes.Decorator.read(data)
+    if tag == TYPE_INFO:
+        return mypy.nodes.TypeInfo.read(data)
+    if tag == OVERLOADED_FUNC_DEF:
+        return mypy.nodes.OverloadedFuncDef.read(data)
+    if tag == TYPE_VAR_EXPR:
+        return mypy.nodes.TypeVarExpr.read(data)
+    if tag == TYPE_ALIAS:
+        return mypy.nodes.TypeAlias.read(data)
+    if tag == PARAM_SPEC_EXPR:
+        return mypy.nodes.ParamSpecExpr.read(data)
+    if tag == TYPE_VAR_TUPLE_EXPR:
+        return mypy.nodes.TypeVarTupleExpr.read(data)
+    assert False, f"Unknown symbol tag {tag}"
+
+
+def read_overload_part(data: Buffer) -> OverloadPart:
+    tag = read_tag(data)
+    if tag == DECORATOR:
+        return Decorator.read(data)
+    if tag == FUNC_DEF:
+        return FuncDef.read(data)
+    assert False, f"Invalid tag for an OverloadPart {tag}"
diff --git a/mypy/options.py b/mypy/options.py
index 4a89ef529c07..b3dc9639a41d 100644
--- a/mypy/options.py
+++ b/mypy/options.py
@@ -55,6 +55,7 @@ class BuildType:
     "mypyc",
     "strict_concatenate",
     "strict_equality",
+    "strict_equality_for_none",
     "strict_optional",
     "warn_no_return",
     "warn_return_any",
@@ -72,6 +73,7 @@ class BuildType:
         "disable_bytearray_promotion",
         "disable_memoryview_promotion",
         "strict_bytes",
+        "fixed_format_cache",
     }
 ) - {"debug_cache"}
 
@@ -229,6 +231,9 @@ def __init__(self) -> None:
         # This makes 1 == '1', 1 in ['1'], and 1 is '1' errors.
         self.strict_equality = False
 
+        # Extend the logic of `scrict_equality` for comparisons with `None`.
+        self.strict_equality_for_none = False
+
         # Disable treating bytearray and memoryview as subtypes of bytes
         self.strict_bytes = False
 
@@ -286,6 +291,7 @@ def __init__(self) -> None:
         self.incremental = True
         self.cache_dir = defaults.CACHE_DIR
         self.sqlite_cache = False
+        self.fixed_format_cache = False
         self.debug_cache = False
         self.skip_version_check = False
         self.skip_cache_mtime_checks = False
@@ -391,10 +397,10 @@ def __init__(self) -> None:
         # skip most errors after this many messages have been reported.
         # -1 means unlimited.
         self.many_errors_threshold = defaults.MANY_ERRORS_THRESHOLD
-        # Disable new experimental type inference algorithm.
+        # Disable new type inference algorithm.
         self.old_type_inference = False
-        # Deprecated reverse version of the above, do not use.
-        self.new_type_inference = False
+        # Disable expression cache (for debugging).
+        self.disable_expression_cache = False
         # Export line-level, limited, fine-grained dependency information in cache data
         # (undocumented feature).
         self.export_ref_info = False
@@ -505,7 +511,6 @@ def apply_changes(self, changes: dict[str, object]) -> Options:
             code = error_codes[code_str]
             new_options.enabled_error_codes.add(code)
             new_options.disabled_error_codes.discard(code)
-
         return new_options
 
     def compare_stable(self, other_snapshot: dict[str, object]) -> bool:
diff --git a/mypy/plugin.py b/mypy/plugin.py
index 831721eb193c..9019e3c2256f 100644
--- a/mypy/plugin.py
+++ b/mypy/plugin.py
@@ -846,12 +846,22 @@ def get_additional_deps(self, file: MypyFile) -> list[tuple[int, str, int]]:
         return deps
 
     def get_type_analyze_hook(self, fullname: str) -> Callable[[AnalyzeTypeContext], Type] | None:
-        return self._find_hook(lambda plugin: plugin.get_type_analyze_hook(fullname))
+        # Micro-optimization: Inline iteration over plugins
+        for plugin in self._plugins:
+            hook = plugin.get_type_analyze_hook(fullname)
+            if hook is not None:
+                return hook
+        return None
 
     def get_function_signature_hook(
         self, fullname: str
     ) -> Callable[[FunctionSigContext], FunctionLike] | None:
-        return self._find_hook(lambda plugin: plugin.get_function_signature_hook(fullname))
+        # Micro-optimization: Inline iteration over plugins
+        for plugin in self._plugins:
+            hook = plugin.get_function_signature_hook(fullname)
+            if hook is not None:
+                return hook
+        return None
 
     def get_function_hook(self, fullname: str) -> Callable[[FunctionContext], Type] | None:
         return self._find_hook(lambda plugin: plugin.get_function_hook(fullname))
@@ -859,13 +869,28 @@ def get_function_hook(self, fullname: str) -> Callable[[FunctionContext], Type]
     def get_method_signature_hook(
         self, fullname: str
     ) -> Callable[[MethodSigContext], FunctionLike] | None:
-        return self._find_hook(lambda plugin: plugin.get_method_signature_hook(fullname))
+        # Micro-optimization: Inline iteration over plugins
+        for plugin in self._plugins:
+            hook = plugin.get_method_signature_hook(fullname)
+            if hook is not None:
+                return hook
+        return None
 
     def get_method_hook(self, fullname: str) -> Callable[[MethodContext], Type] | None:
-        return self._find_hook(lambda plugin: plugin.get_method_hook(fullname))
+        # Micro-optimization: Inline iteration over plugins
+        for plugin in self._plugins:
+            hook = plugin.get_method_hook(fullname)
+            if hook is not None:
+                return hook
+        return None
 
     def get_attribute_hook(self, fullname: str) -> Callable[[AttributeContext], Type] | None:
-        return self._find_hook(lambda plugin: plugin.get_attribute_hook(fullname))
+        # Micro-optimization: Inline iteration over plugins
+        for plugin in self._plugins:
+            hook = plugin.get_attribute_hook(fullname)
+            if hook is not None:
+                return hook
+        return None
 
     def get_class_attribute_hook(self, fullname: str) -> Callable[[AttributeContext], Type] | None:
         return self._find_hook(lambda plugin: plugin.get_class_attribute_hook(fullname))
@@ -897,6 +922,6 @@ def get_dynamic_class_hook(
     def _find_hook(self, lookup: Callable[[Plugin], T]) -> T | None:
         for plugin in self._plugins:
             hook = lookup(plugin)
-            if hook:
+            if hook is not None:
                 return hook
         return None
diff --git a/mypy/plugins/attrs.py b/mypy/plugins/attrs.py
index b7b3821576ea..47c6ad9f305a 100644
--- a/mypy/plugins/attrs.py
+++ b/mypy/plugins/attrs.py
@@ -458,7 +458,7 @@ def _analyze_class(
             if isinstance(node, PlaceholderNode):
                 # This node is not ready yet.
                 continue
-            assert isinstance(node, Var)
+            assert isinstance(node, Var), node
             node.is_initialized_in_class = False
 
     # Traverse the MRO and collect attributes from the parents.
diff --git a/mypy/plugins/common.py b/mypy/plugins/common.py
index ac00171a037c..ed2a91d102f4 100644
--- a/mypy/plugins/common.py
+++ b/mypy/plugins/common.py
@@ -360,7 +360,7 @@ def _add_method_by_spec(
 
     signature = CallableType(arg_types, arg_kinds, arg_names, return_type, function_type)
     if tvar_defs:
-        signature.variables = tvar_defs
+        signature.variables = tuple(tvar_defs)
 
     func = FuncDef(name, args, Block([PassStmt()]))
     func.info = info
diff --git a/mypy/plugins/constants.py b/mypy/plugins/constants.py
new file mode 100644
index 000000000000..9a09e89202de
--- /dev/null
+++ b/mypy/plugins/constants.py
@@ -0,0 +1,20 @@
+"""Constant definitions for plugins kept here to help with import cycles."""
+
+from typing import Final
+
+from mypy.semanal_enum import ENUM_BASES
+
+SINGLEDISPATCH_TYPE: Final = "functools._SingleDispatchCallable"
+SINGLEDISPATCH_REGISTER_METHOD: Final = f"{SINGLEDISPATCH_TYPE}.register"
+SINGLEDISPATCH_CALLABLE_CALL_METHOD: Final = f"{SINGLEDISPATCH_TYPE}.__call__"
+SINGLEDISPATCH_REGISTER_RETURN_CLASS: Final = "_SingleDispatchRegisterCallable"
+SINGLEDISPATCH_REGISTER_CALLABLE_CALL_METHOD: Final = (
+    f"functools.{SINGLEDISPATCH_REGISTER_RETURN_CLASS}.__call__"
+)
+
+ENUM_NAME_ACCESS: Final = {f"{prefix}.name" for prefix in ENUM_BASES} | {
+    f"{prefix}._name_" for prefix in ENUM_BASES
+}
+ENUM_VALUE_ACCESS: Final = {f"{prefix}.value" for prefix in ENUM_BASES} | {
+    f"{prefix}._value_" for prefix in ENUM_BASES
+}
diff --git a/mypy/plugins/dataclasses.py b/mypy/plugins/dataclasses.py
index 99d4ef56a540..e916ded01dd2 100644
--- a/mypy/plugins/dataclasses.py
+++ b/mypy/plugins/dataclasses.py
@@ -410,13 +410,12 @@ def _add_dunder_replace(self, attributes: list[DataclassAttribute]) -> None:
             for attr in attributes
             if attr.is_in_init
         ]
-        type_vars = [tv for tv in self._cls.type_vars]
         add_method_to_class(
             self._api,
             self._cls,
             "__replace__",
             args=args,
-            return_type=Instance(self._cls.info, type_vars),
+            return_type=fill_typevars(self._cls.info),
         )
 
     def _add_internal_replace_method(self, attributes: list[DataclassAttribute]) -> None:
@@ -610,7 +609,7 @@ def collect_attributes(self) -> list[DataclassAttribute] | None:
                 # We will issue an error later.
                 continue
 
-            assert isinstance(node, Var)
+            assert isinstance(node, Var), node
 
             # x: ClassVar[int] is ignored by dataclasses.
             if node.is_classvar:
diff --git a/mypy/plugins/default.py b/mypy/plugins/default.py
index 2002a4f06093..e492b8dd7335 100644
--- a/mypy/plugins/default.py
+++ b/mypy/plugins/default.py
@@ -15,7 +15,51 @@
     MethodSigContext,
     Plugin,
 )
+from mypy.plugins.attrs import (
+    attr_class_maker_callback,
+    attr_class_makers,
+    attr_dataclass_makers,
+    attr_define_makers,
+    attr_frozen_makers,
+    attr_tag_callback,
+    evolve_function_sig_callback,
+    fields_function_sig_callback,
+)
 from mypy.plugins.common import try_getting_str_literals
+from mypy.plugins.constants import (
+    ENUM_NAME_ACCESS,
+    ENUM_VALUE_ACCESS,
+    SINGLEDISPATCH_CALLABLE_CALL_METHOD,
+    SINGLEDISPATCH_REGISTER_CALLABLE_CALL_METHOD,
+    SINGLEDISPATCH_REGISTER_METHOD,
+)
+from mypy.plugins.ctypes import (
+    array_constructor_callback,
+    array_getitem_callback,
+    array_iter_callback,
+    array_raw_callback,
+    array_setitem_callback,
+    array_value_callback,
+)
+from mypy.plugins.dataclasses import (
+    dataclass_class_maker_callback,
+    dataclass_makers,
+    dataclass_tag_callback,
+    replace_function_sig_callback,
+)
+from mypy.plugins.enums import enum_member_callback, enum_name_callback, enum_value_callback
+from mypy.plugins.functools import (
+    functools_total_ordering_maker_callback,
+    functools_total_ordering_makers,
+    partial_call_callback,
+    partial_new_callback,
+)
+from mypy.plugins.singledispatch import (
+    call_singledispatch_function_after_register_argument,
+    call_singledispatch_function_callback,
+    create_singledispatch_function_callback,
+    singledispatch_register_callback,
+)
 from mypy.subtypes import is_subtype
 from mypy.typeops import is_literal_type_like, make_simplified_union
 from mypy.types import (
@@ -36,70 +80,61 @@
     get_proper_types,
 )
 
+TD_SETDEFAULT_NAMES: Final = {n + ".setdefault" for n in TPDICT_FB_NAMES}
+TD_POP_NAMES: Final = {n + ".pop" for n in TPDICT_FB_NAMES}
+TD_DELITEM_NAMES: Final = {n + ".__delitem__" for n in TPDICT_FB_NAMES}
+
+TD_UPDATE_METHOD_NAMES: Final = (
+    {n + ".update" for n in TPDICT_FB_NAMES}
+    | {n + ".__or__" for n in TPDICT_FB_NAMES}
+    | {n + ".__ror__" for n in TPDICT_FB_NAMES}
+    | {n + ".__ior__" for n in TPDICT_FB_NAMES}
+)
+
 
 class DefaultPlugin(Plugin):
     """Type checker plugin that is enabled by default."""
 
     def get_function_hook(self, fullname: str) -> Callable[[FunctionContext], Type] | None:
-        from mypy.plugins import ctypes, enums, singledispatch
-
         if fullname == "_ctypes.Array":
-            return ctypes.array_constructor_callback
+            return array_constructor_callback
         elif fullname == "functools.singledispatch":
-            return singledispatch.create_singledispatch_function_callback
+            return create_singledispatch_function_callback
         elif fullname == "functools.partial":
-            import mypy.plugins.functools
-
-            return mypy.plugins.functools.partial_new_callback
+            return partial_new_callback
         elif fullname == "enum.member":
-            return enums.enum_member_callback
-
+            return enum_member_callback
         return None
 
     def get_function_signature_hook(
         self, fullname: str
     ) -> Callable[[FunctionSigContext], FunctionLike] | None:
-        from mypy.plugins import attrs, dataclasses
-
         if fullname in ("attr.evolve", "attrs.evolve", "attr.assoc", "attrs.assoc"):
-            return attrs.evolve_function_sig_callback
+            return evolve_function_sig_callback
         elif fullname in ("attr.fields", "attrs.fields"):
-            return attrs.fields_function_sig_callback
+            return fields_function_sig_callback
         elif fullname == "dataclasses.replace":
-            return dataclasses.replace_function_sig_callback
+            return replace_function_sig_callback
         return None
 
     def get_method_signature_hook(
         self, fullname: str
     ) -> Callable[[MethodSigContext], FunctionLike] | None:
-        from mypy.plugins import ctypes, singledispatch
-
         if fullname == "typing.Mapping.get":
             return typed_dict_get_signature_callback
-        elif fullname in {n + ".setdefault" for n in TPDICT_FB_NAMES}:
+        elif fullname in TD_SETDEFAULT_NAMES:
             return typed_dict_setdefault_signature_callback
-        elif fullname in {n + ".pop" for n in TPDICT_FB_NAMES}:
+        elif fullname in TD_POP_NAMES:
             return typed_dict_pop_signature_callback
         elif fullname == "_ctypes.Array.__setitem__":
-            return ctypes.array_setitem_callback
-        elif fullname == singledispatch.SINGLEDISPATCH_CALLABLE_CALL_METHOD:
-            return singledispatch.call_singledispatch_function_callback
-
-        typed_dict_updates = set()
-        for n in TPDICT_FB_NAMES:
-            typed_dict_updates.add(n + ".update")
-            typed_dict_updates.add(n + ".__or__")
-            typed_dict_updates.add(n + ".__ror__")
-            typed_dict_updates.add(n + ".__ior__")
-
-        if fullname in typed_dict_updates:
+            return array_setitem_callback
+        elif fullname == SINGLEDISPATCH_CALLABLE_CALL_METHOD:
+            return call_singledispatch_function_callback
+        elif fullname in TD_UPDATE_METHOD_NAMES:
             return typed_dict_update_signature_callback
-
         return None
 
     def get_method_hook(self, fullname: str) -> Callable[[MethodContext], Type] | None:
-        from mypy.plugins import ctypes, singledispatch
-
         if fullname == "typing.Mapping.get":
             return typed_dict_get_callback
         elif fullname == "builtins.int.__pow__":
@@ -110,81 +145,70 @@ def get_method_hook(self, fullname: str) -> Callable[[MethodContext], Type] | No
             return int_pos_callback
         elif fullname in ("builtins.tuple.__mul__", "builtins.tuple.__rmul__"):
             return tuple_mul_callback
-        elif fullname in {n + ".setdefault" for n in TPDICT_FB_NAMES}:
+        elif fullname in TD_SETDEFAULT_NAMES:
             return typed_dict_setdefault_callback
-        elif fullname in {n + ".pop" for n in TPDICT_FB_NAMES}:
+        elif fullname in TD_POP_NAMES:
             return typed_dict_pop_callback
-        elif fullname in {n + ".__delitem__" for n in TPDICT_FB_NAMES}:
+        elif fullname in TD_DELITEM_NAMES:
             return typed_dict_delitem_callback
         elif fullname == "_ctypes.Array.__getitem__":
-            return ctypes.array_getitem_callback
+            return array_getitem_callback
         elif fullname == "_ctypes.Array.__iter__":
-            return ctypes.array_iter_callback
-        elif fullname == singledispatch.SINGLEDISPATCH_REGISTER_METHOD:
-            return singledispatch.singledispatch_register_callback
-        elif fullname == singledispatch.REGISTER_CALLABLE_CALL_METHOD:
-            return singledispatch.call_singledispatch_function_after_register_argument
+            return array_iter_callback
+        elif fullname == SINGLEDISPATCH_REGISTER_METHOD:
+            return singledispatch_register_callback
+        elif fullname == SINGLEDISPATCH_REGISTER_CALLABLE_CALL_METHOD:
+            return call_singledispatch_function_after_register_argument
         elif fullname == "functools.partial.__call__":
-            import mypy.plugins.functools
-
-            return mypy.plugins.functools.partial_call_callback
+            return partial_call_callback
         return None
 
     def get_attribute_hook(self, fullname: str) -> Callable[[AttributeContext], Type] | None:
-        from mypy.plugins import ctypes, enums
-
         if fullname == "_ctypes.Array.value":
-            return ctypes.array_value_callback
+            return array_value_callback
         elif fullname == "_ctypes.Array.raw":
-            return ctypes.array_raw_callback
-        elif fullname in enums.ENUM_NAME_ACCESS:
-            return enums.enum_name_callback
-        elif fullname in enums.ENUM_VALUE_ACCESS:
-            return enums.enum_value_callback
+            return array_raw_callback
+        elif fullname in ENUM_NAME_ACCESS:
+            return enum_name_callback
+        elif fullname in ENUM_VALUE_ACCESS:
+            return enum_value_callback
         return None
 
     def get_class_decorator_hook(self, fullname: str) -> Callable[[ClassDefContext], None] | None:
-        from mypy.plugins import attrs, dataclasses
-
         # These dataclass and attrs hooks run in the main semantic analysis pass
         # and only tag known dataclasses/attrs classes, so that the second
         # hooks (in get_class_decorator_hook_2) can detect dataclasses/attrs classes
         # in the MRO.
-        if fullname in dataclasses.dataclass_makers:
-            return dataclasses.dataclass_tag_callback
+        if fullname in dataclass_makers:
+            return dataclass_tag_callback
         if (
-            fullname in attrs.attr_class_makers
-            or fullname in attrs.attr_dataclass_makers
-            or fullname in attrs.attr_frozen_makers
-            or fullname in attrs.attr_define_makers
+            fullname in attr_class_makers
+            or fullname in attr_dataclass_makers
+            or fullname in attr_frozen_makers
+            or fullname in attr_define_makers
         ):
-            return attrs.attr_tag_callback
-
+            return attr_tag_callback
         return None
 
     def get_class_decorator_hook_2(
         self, fullname: str
     ) -> Callable[[ClassDefContext], bool] | None:
-        import mypy.plugins.functools
-        from mypy.plugins import attrs, dataclasses
-
-        if fullname in dataclasses.dataclass_makers:
-            return dataclasses.dataclass_class_maker_callback
-        elif fullname in mypy.plugins.functools.functools_total_ordering_makers:
-            return mypy.plugins.functools.functools_total_ordering_maker_callback
-        elif fullname in attrs.attr_class_makers:
-            return attrs.attr_class_maker_callback
-        elif fullname in attrs.attr_dataclass_makers:
-            return partial(attrs.attr_class_maker_callback, auto_attribs_default=True)
-        elif fullname in attrs.attr_frozen_makers:
+        if fullname in dataclass_makers:
+            return dataclass_class_maker_callback
+        elif fullname in functools_total_ordering_makers:
+            return functools_total_ordering_maker_callback
+        elif fullname in attr_class_makers:
+            return attr_class_maker_callback
+        elif fullname in attr_dataclass_makers:
+            return partial(attr_class_maker_callback, auto_attribs_default=True)
+        elif fullname in attr_frozen_makers:
             return partial(
-                attrs.attr_class_maker_callback, auto_attribs_default=None, frozen_default=True
+                attr_class_maker_callback, auto_attribs_default=None, frozen_default=True
             )
-        elif fullname in attrs.attr_define_makers:
+        elif fullname in attr_define_makers:
             return partial(
-                attrs.attr_class_maker_callback, auto_attribs_default=None, slots_default=True
+                attr_class_maker_callback, auto_attribs_default=None, slots_default=True
             )
-
         return None
 
 
diff --git a/mypy/plugins/enums.py b/mypy/plugins/enums.py
index 8b7c5df6f51f..0be2e083b6dd 100644
--- a/mypy/plugins/enums.py
+++ b/mypy/plugins/enums.py
@@ -14,14 +14,15 @@
 from __future__ import annotations
 
 from collections.abc import Iterable, Sequence
-from typing import Final, TypeVar, cast
+from typing import TypeVar, cast
 
 import mypy.plugin  # To avoid circular imports.
-from mypy.nodes import TypeInfo
-from mypy.semanal_enum import ENUM_BASES
+from mypy.checker_shared import TypeCheckerSharedApi
+from mypy.nodes import TypeInfo, Var
 from mypy.subtypes import is_equivalent
 from mypy.typeops import fixup_partial_type, make_simplified_union
 from mypy.types import (
+    ELLIPSIS_TYPE_NAMES,
     CallableType,
     Instance,
     LiteralType,
@@ -31,13 +32,6 @@
     is_named_instance,
 )
 
-ENUM_NAME_ACCESS: Final = {f"{prefix}.name" for prefix in ENUM_BASES} | {
-    f"{prefix}._name_" for prefix in ENUM_BASES
-}
-ENUM_VALUE_ACCESS: Final = {f"{prefix}.value" for prefix in ENUM_BASES} | {
-    f"{prefix}._value_" for prefix in ENUM_BASES
-}
-
 
 def enum_name_callback(ctx: mypy.plugin.AttributeContext) -> Type:
     """This plugin refines the 'name' attribute in enums to act as if
@@ -87,6 +81,19 @@ def _infer_value_type_with_auto_fallback(
     if proper_type is None:
         return None
     proper_type = get_proper_type(fixup_partial_type(proper_type))
+    # Enums in stubs may have ... instead of actual values. If `_value_` is annotated
+    # (manually or inherited from IntEnum, for example), it is a more reasonable guess
+    # than literal ellipsis type.
+    if (
+        _is_defined_in_stub(ctx)
+        and isinstance(proper_type, Instance)
+        and proper_type.type.fullname in ELLIPSIS_TYPE_NAMES
+        and isinstance(ctx.type, Instance)
+    ):
+        value_type = ctx.type.type.get("_value_")
+        if value_type is not None and isinstance(var := value_type.node, Var):
+            return var.type
+        return proper_type
     if not (isinstance(proper_type, Instance) and proper_type.type.fullname == "enum.auto"):
         if is_named_instance(proper_type, "enum.member") and proper_type.args:
             return proper_type.args[0]
@@ -114,6 +121,11 @@ def _infer_value_type_with_auto_fallback(
     return ctx.default_attr_type
 
 
+def _is_defined_in_stub(ctx: mypy.plugin.AttributeContext) -> bool:
+    assert isinstance(ctx.api, TypeCheckerSharedApi)
+    return isinstance(ctx.type, Instance) and ctx.api.is_defined_in_stub(ctx.type)
+
+
 def _implements_new(info: TypeInfo) -> bool:
     """Check whether __new__ comes from enum.Enum or was implemented in a
     subclass. In the latter case, we must infer Any as long as mypy can't infer
@@ -132,7 +144,7 @@ def _implements_new(info: TypeInfo) -> bool:
 def enum_member_callback(ctx: mypy.plugin.FunctionContext) -> Type:
     """By default `member(1)` will be inferred as `member[int]`,
     we want to improve the inference to be `Literal[1]` here."""
-    if ctx.arg_types or ctx.arg_types[0]:
+    if ctx.arg_types and ctx.arg_types[0]:
         arg = get_proper_type(ctx.arg_types[0][0])
         proper_return = get_proper_type(ctx.default_return_type)
         if (
diff --git a/mypy/plugins/proper_plugin.py b/mypy/plugins/proper_plugin.py
index f51685c80afa..0189bfbd22fc 100644
--- a/mypy/plugins/proper_plugin.py
+++ b/mypy/plugins/proper_plugin.py
@@ -107,6 +107,7 @@ def is_special_target(right: ProperType) -> bool:
             "mypy.types.DeletedType",
             "mypy.types.RequiredType",
             "mypy.types.ReadOnlyType",
+            "mypy.types.TypeGuardedType",
         ):
             # Special case: these are not valid targets for a type alias and thus safe.
             # TODO: introduce a SyntheticType base to simplify this?
diff --git a/mypy/plugins/singledispatch.py b/mypy/plugins/singledispatch.py
index be4b405ce610..eb2bbe133bf0 100644
--- a/mypy/plugins/singledispatch.py
+++ b/mypy/plugins/singledispatch.py
@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 from collections.abc import Sequence
-from typing import Final, NamedTuple, TypeVar, Union
+from typing import NamedTuple, TypeVar, Union
 from typing_extensions import TypeAlias as _TypeAlias
 
 from mypy.messages import format_type
@@ -9,6 +9,7 @@
 from mypy.options import Options
 from mypy.plugin import CheckerPluginInterface, FunctionContext, MethodContext, MethodSigContext
 from mypy.plugins.common import add_method_to_class
+from mypy.plugins.constants import SINGLEDISPATCH_REGISTER_RETURN_CLASS
 from mypy.subtypes import is_subtype
 from mypy.types import (
     AnyType,
@@ -33,13 +34,6 @@ class RegisterCallableInfo(NamedTuple):
     singledispatch_obj: Instance
 
 
-SINGLEDISPATCH_TYPE: Final = "functools._SingleDispatchCallable"
-
-SINGLEDISPATCH_REGISTER_METHOD: Final = f"{SINGLEDISPATCH_TYPE}.register"
-
-SINGLEDISPATCH_CALLABLE_CALL_METHOD: Final = f"{SINGLEDISPATCH_TYPE}.__call__"
-
-
 def get_singledispatch_info(typ: Instance) -> SingledispatchTypeVars | None:
     if len(typ.args) == 2:
         return SingledispatchTypeVars(*typ.args)  # type: ignore[arg-type]
@@ -56,16 +50,11 @@ def get_first_arg(args: list[list[T]]) -> T | None:
     return None
 
 
-REGISTER_RETURN_CLASS: Final = "_SingleDispatchRegisterCallable"
-
-REGISTER_CALLABLE_CALL_METHOD: Final = f"functools.{REGISTER_RETURN_CLASS}.__call__"
-
-
 def make_fake_register_class_instance(
     api: CheckerPluginInterface, type_args: Sequence[Type]
 ) -> Instance:
-    defn = ClassDef(REGISTER_RETURN_CLASS, Block([]))
-    defn.fullname = f"functools.{REGISTER_RETURN_CLASS}"
+    defn = ClassDef(SINGLEDISPATCH_REGISTER_RETURN_CLASS, Block([]))
+    defn.fullname = f"functools.{SINGLEDISPATCH_REGISTER_RETURN_CLASS}"
     info = TypeInfo(SymbolTable(), defn, "functools")
     obj_type = api.named_generic_type("builtins.object", []).type
     info.bases = [Instance(obj_type, [])]
diff --git a/mypy/semanal.py b/mypy/semanal.py
index d70abe911fea..50ee3b532463 100644
--- a/mypy/semanal.py
+++ b/mypy/semanal.py
@@ -254,6 +254,7 @@
     ASSERT_TYPE_NAMES,
     DATACLASS_TRANSFORM_NAMES,
     DEPRECATED_TYPE_NAMES,
+    DISJOINT_BASE_DECORATOR_NAMES,
     FINAL_DECORATOR_NAMES,
     FINAL_TYPE_NAMES,
     IMPORTED_REVEAL_TYPE_NAMES,
@@ -294,6 +295,7 @@
     UnboundType,
     UnionType,
     UnpackType,
+    flatten_nested_tuples,
     get_proper_type,
     get_proper_types,
     has_type_vars,
@@ -497,6 +499,10 @@ def __init__(
         # Used to track edge case when return is still inside except* if it enters a loop
         self.return_stmt_inside_except_star_block: bool = False
 
+        self._str_type: Instance | None = None
+        self._function_type: Instance | None = None
+        self._object_type: Instance | None = None
+
     # mypyc doesn't properly handle implementing an abstractproperty
     # with a regular attribute so we make them properties
     @property
@@ -989,7 +995,7 @@ def analyze_func_def(self, defn: FuncDef) -> None:
                     if has_self_type and self.type is not None:
                         info = self.type
                         if info.self_type is not None:
-                            result.variables = [info.self_type] + list(result.variables)
+                            result.variables = (info.self_type,) + result.variables
                 defn.type = result
                 self.add_type_alias_deps(analyzer.aliases_used)
                 self.check_function_signature(defn)
@@ -1046,21 +1052,21 @@ def remove_unpack_kwargs(self, defn: FuncDef, typ: CallableType) -> CallableType
         last_type = typ.arg_types[-1]
         if not isinstance(last_type, UnpackType):
             return typ
-        last_type = get_proper_type(last_type.type)
-        if not isinstance(last_type, TypedDictType):
+        p_last_type = get_proper_type(last_type.type)
+        if not isinstance(p_last_type, TypedDictType):
             self.fail("Unpack item in ** argument must be a TypedDict", last_type)
             new_arg_types = typ.arg_types[:-1] + [AnyType(TypeOfAny.from_error)]
             return typ.copy_modified(arg_types=new_arg_types)
-        overlap = set(typ.arg_names) & set(last_type.items)
+        overlap = set(typ.arg_names) & set(p_last_type.items)
         # It is OK for TypedDict to have a key named 'kwargs'.
         overlap.discard(typ.arg_names[-1])
         if overlap:
-            overlapped = ", ".join([f'"{name}"' for name in overlap])
+            overlapped = ", ".join([f'"{name}"' for name in sorted(filter(None, overlap))])
             self.fail(f"Overlap between argument names and ** TypedDict items: {overlapped}", defn)
             new_arg_types = typ.arg_types[:-1] + [AnyType(TypeOfAny.from_error)]
             return typ.copy_modified(arg_types=new_arg_types)
         # OK, everything looks right now, mark the callable type as using unpack.
-        new_arg_types = typ.arg_types[:-1] + [last_type]
+        new_arg_types = typ.arg_types[:-1] + [p_last_type]
         return typ.copy_modified(arg_types=new_arg_types, unpack_kwargs=True)
 
     def prepare_method_signature(self, func: FuncDef, info: TypeInfo, has_self_type: bool) -> None:
@@ -1069,15 +1075,10 @@ def prepare_method_signature(self, func: FuncDef, info: TypeInfo, has_self_type:
         functype = func.type
         if func.name == "__new__":
             func.is_static = True
-        if not func.is_static or func.name == "__new__":
+        if func.has_self_or_cls_argument:
             if func.name in ["__init_subclass__", "__class_getitem__"]:
                 func.is_class = True
-            if not func.arguments:
-                self.fail(
-                    'Method must have at least one argument. Did you forget the "self" argument?',
-                    func,
-                )
-            elif isinstance(functype, CallableType):
+            if func.arguments and isinstance(functype, CallableType):
                 self_type = get_proper_type(functype.arg_types[0])
                 if isinstance(self_type, AnyType):
                     if has_self_type:
@@ -1246,8 +1247,9 @@ def analyze_overloaded_func_def(self, defn: OverloadedFuncDef) -> None:
             # This is a property.
             first_item.func.is_overload = True
             bare_setter_type = self.analyze_property_with_multi_part_definition(defn)
-            typ = function_type(first_item.func, self.named_type("builtins.function"))
+            typ = function_type(first_item.func, self.function_type())
             assert isinstance(typ, CallableType)
+            typ.definition = first_item
             types = [typ]
         else:
             # This is a normal overload. Find the item signatures, the
@@ -1377,8 +1379,9 @@ def analyze_overload_sigs_and_impl(
                     item.accept(self)
             # TODO: support decorated overloaded functions properly
             if isinstance(item, Decorator):
-                callable = function_type(item.func, self.named_type("builtins.function"))
+                callable = function_type(item.func, self.function_type())
                 assert isinstance(callable, CallableType)
+                callable.definition = item
                 if not any(refers_to_fullname(dec, OVERLOAD_NAMES) for dec in item.decorators):
                     if i == len(defn.items) - 1 and not self.is_stub_file:
                         # Last item outside a stub is impl
@@ -1527,33 +1530,31 @@ def analyze_property_with_multi_part_definition(
         assert isinstance(first_item, Decorator)
         deleted_items = []
         bare_setter_type = None
+        func_name = first_item.func.name
         for i, item in enumerate(items[1:]):
             if isinstance(item, Decorator):
                 item.func.accept(self)
                 if item.decorators:
                     first_node = item.decorators[0]
-                    if isinstance(first_node, MemberExpr):
+                    if self._is_valid_property_decorator(first_node, func_name):
+                        # Get abstractness from the original definition.
+                        item.func.abstract_status = first_item.func.abstract_status
                         if first_node.name == "setter":
                             # The first item represents the entire property.
                             first_item.var.is_settable_property = True
-                            # Get abstractness from the original definition.
-                            item.func.abstract_status = first_item.func.abstract_status
-                            setter_func_type = function_type(
-                                item.func, self.named_type("builtins.function")
-                            )
+                            setter_func_type = function_type(item.func, self.function_type())
                             assert isinstance(setter_func_type, CallableType)
                             bare_setter_type = setter_func_type
                             defn.setter_index = i + 1
-                        if first_node.name == "deleter":
-                            item.func.abstract_status = first_item.func.abstract_status
                         for other_node in item.decorators[1:]:
                             other_node.accept(self)
                     else:
                         self.fail(
-                            f"Only supported top decorator is @{first_item.func.name}.setter", item
+                            f'Only supported top decorators are "@{func_name}.setter" and "@{func_name}.deleter"',
+                            first_node,
                         )
             else:
-                self.fail(f'Unexpected definition for property "{first_item.func.name}"', item)
+                self.fail(f'Unexpected definition for property "{func_name}"', item)
                 deleted_items.append(i + 1)
         for i in reversed(deleted_items):
             del items[i]
@@ -1567,6 +1568,23 @@ def analyze_property_with_multi_part_definition(
                         )
         return bare_setter_type
 
+    def _is_valid_property_decorator(
+        self, deco: Expression, property_name: str
+    ) -> TypeGuard[MemberExpr]:
+        if not isinstance(deco, MemberExpr):
+            return False
+        if not isinstance(deco.expr, NameExpr) or deco.expr.name != property_name:
+            return False
+        if deco.name not in {"setter", "deleter"}:
+            # This intentionally excludes getter. While `@prop.getter` is valid at
+            # runtime, that would mean replacing the already processed getter type.
+            # Such usage is almost definitely a mistake (except for overrides in
+            # subclasses but we don't support them anyway) and might be a typo
+            # (only one letter away from `setter`), it's likely almost never used,
+            # so supporting it properly won't pay off.
+            return False
+        return True
+
     def add_function_to_symbol_table(self, func: FuncDef | OverloadedFuncDef) -> None:
         if self.is_class_scope():
             assert self.type is not None
@@ -1602,7 +1620,7 @@ def analyze_function_body(self, defn: FuncItem) -> None:
                 # The first argument of a non-static, non-class method is like 'self'
                 # (though the name could be different), having the enclosing class's
                 # instance type.
-                if is_method and (not defn.is_static or defn.name == "__new__") and defn.arguments:
+                if is_method and defn.has_self_or_cls_argument and defn.arguments:
                     if not defn.is_class:
                         defn.arguments[0].variable.is_self = True
                     else:
@@ -2172,6 +2190,8 @@ def analyze_class_decorator_common(
         """
         if refers_to_fullname(decorator, FINAL_DECORATOR_NAMES):
             info.is_final = True
+        elif refers_to_fullname(decorator, DISJOINT_BASE_DECORATOR_NAMES):
+            info.is_disjoint_base = True
         elif refers_to_fullname(decorator, TYPE_CHECK_ONLY_NAMES):
             info.is_type_check_only = True
         elif (deprecated := self.get_deprecated(decorator)) is not None:
@@ -2374,6 +2394,14 @@ def tvar_defs_from_tvars(
             tvar_expr.default = tvar_expr.default.accept(
                 TypeVarDefaultTranslator(self, tvar_expr.name, context)
             )
+            # PEP-695 type variables that are redeclared in an inner scope are warned
+            # about elsewhere.
+            if not tvar_expr.is_new_style and not self.tvar_scope.allow_binding(
+                tvar_expr.fullname
+            ):
+                self.fail(
+                    message_registry.TYPE_VAR_REDECLARED_IN_NESTED_CLASS.format(name), context
+                )
             tvar_def = self.tvar_scope.bind_new(name, tvar_expr)
             if last_tvar_name_with_default is not None and not tvar_def.has_default():
                 self.msg.tvar_without_default_type(
@@ -2694,7 +2722,7 @@ def infer_metaclass_and_bases_from_compat_helpers(self, defn: ClassDef) -> None:
         if len(metas) == 0:
             return
         if len(metas) > 1:
-            self.fail("Multiple metaclass definitions", defn)
+            self.fail("Multiple metaclass definitions", defn, code=codes.METACLASS)
             return
         defn.metaclass = metas.pop()
 
@@ -2750,7 +2778,11 @@ def get_declared_metaclass(
             elif isinstance(metaclass_expr, MemberExpr):
                 metaclass_name = get_member_expr_fullname(metaclass_expr)
             if metaclass_name is None:
-                self.fail(f'Dynamic metaclass not supported for "{name}"', metaclass_expr)
+                self.fail(
+                    f'Dynamic metaclass not supported for "{name}"',
+                    metaclass_expr,
+                    code=codes.METACLASS,
+                )
                 return None, False, True
             sym = self.lookup_qualified(metaclass_name, metaclass_expr)
             if sym is None:
@@ -2761,6 +2793,7 @@ def get_declared_metaclass(
                     self.fail(
                         f'Class cannot use "{sym.node.name}" as a metaclass (has type "Any")',
                         metaclass_expr,
+                        code=codes.METACLASS,
                     )
                 return None, False, True
             if isinstance(sym.node, PlaceholderNode):
@@ -2778,11 +2811,15 @@ def get_declared_metaclass(
                     metaclass_info = target.type
 
             if not isinstance(metaclass_info, TypeInfo) or metaclass_info.tuple_type is not None:
-                self.fail(f'Invalid metaclass "{metaclass_name}"', metaclass_expr)
+                self.fail(
+                    f'Invalid metaclass "{metaclass_name}"', metaclass_expr, code=codes.METACLASS
+                )
                 return None, False, False
             if not metaclass_info.is_metaclass():
                 self.fail(
-                    'Metaclasses not inheriting from "type" are not supported', metaclass_expr
+                    'Metaclasses not inheriting from "type" are not supported',
+                    metaclass_expr,
+                    code=codes.METACLASS,
                 )
                 return None, False, False
             inst = fill_typevars(metaclass_info)
@@ -3015,7 +3052,9 @@ def report_missing_module_attribute(
                 message = (
                     f'Module "{import_id}" does not explicitly export attribute "{source_id}"'
                 )
-            else:
+            elif not (
+                self.options.ignore_errors or self.cur_mod_node.path in self.errors.ignored_files
+            ):
                 alternatives = set(module.names.keys()).difference({source_id})
                 matches = best_matches(source_id, alternatives, n=3)
                 if matches:
@@ -4541,6 +4580,9 @@ def analyze_member_lvalue(
                     lval.node = v
                     # TODO: should we also set lval.kind = MDEF?
                     self.type.names[lval.name] = SymbolTableNode(MDEF, v, implicit=True)
+                    for func in self.scope.functions:
+                        if isinstance(func, FuncDef):
+                            func.has_self_attr_def = True
         self.check_lvalue_validity(lval.node, lval)
 
     def is_self_member_ref(self, memberexpr: MemberExpr) -> bool:
@@ -5065,20 +5107,13 @@ def check_classvar(self, s: AssignmentStmt) -> None:
             return
         if not s.type or not self.is_classvar(s.type):
             return
+        assert isinstance(s.type, UnboundType)
         if self.is_class_scope() and isinstance(lvalue, NameExpr):
             node = lvalue.node
             if isinstance(node, Var):
                 node.is_classvar = True
             analyzed = self.anal_type(s.type)
             assert self.type is not None
-            if analyzed is not None and set(get_type_vars(analyzed)) & set(
-                self.type.defn.type_vars
-            ):
-                # This means that we have a type var defined inside of a ClassVar.
-                # This is not allowed by PEP526.
-                # See https://github.com/python/mypy/issues/11538
-
-                self.fail(message_registry.CLASS_VAR_WITH_TYPEVARS, s)
             if (
                 analyzed is not None
                 and self.type.self_type in get_type_vars(analyzed)
@@ -5089,6 +5124,12 @@ def check_classvar(self, s: AssignmentStmt) -> None:
             # In case of member access, report error only when assigning to self
             # Other kinds of member assignments should be already reported
             self.fail_invalid_classvar(lvalue)
+        if not s.type.args:
+            if isinstance(s.rvalue, TempNode) and s.rvalue.no_rhs:
+                if self.options.disallow_any_generics:
+                    self.fail("ClassVar without type argument becomes Any", s, code=codes.TYPE_ARG)
+                return
+            s.type = None
 
     def is_classvar(self, typ: Type) -> bool:
         if not isinstance(typ, UnboundType):
@@ -5295,6 +5336,7 @@ def visit_expression_stmt(self, s: ExpressionStmt) -> None:
         s.expr.accept(self)
 
     def visit_return_stmt(self, s: ReturnStmt) -> None:
+        old = self.statement
         self.statement = s
         if not self.is_func_scope():
             self.fail('"return" outside function', s)
@@ -5302,6 +5344,7 @@ def visit_return_stmt(self, s: ReturnStmt) -> None:
             self.fail('"return" not allowed in except* block', s, serious=True)
         if s.expr:
             s.expr.accept(self)
+        self.statement = old
 
     def visit_raise_stmt(self, s: RaiseStmt) -> None:
         self.statement = s
@@ -5555,7 +5598,8 @@ def visit_type_alias_stmt(self, s: TypeAliasStmt) -> None:
             else:
                 incomplete_target = has_placeholder(res)
 
-            if self.found_incomplete_ref(tag) or incomplete_target:
+            incomplete_tv = any(has_placeholder(tv) for tv in alias_tvars)
+            if self.found_incomplete_ref(tag) or incomplete_target or incomplete_tv:
                 # Since we have got here, we know this must be a type alias (incomplete refs
                 # may appear in nested positions), therefore use becomes_typeinfo=True.
                 self.mark_incomplete(s.name.name, s.value, becomes_typeinfo=True)
@@ -5605,6 +5649,8 @@ def visit_type_alias_stmt(self, s: TypeAliasStmt) -> None:
                         existing.node.target = res
                         existing.node.alias_tvars = alias_tvars
                         updated = True
+                        # Invalidate recursive status cache in case it was previously set.
+                        existing.node._is_recursive = None
                 else:
                     # Otherwise just replace existing placeholder with type alias.
                     existing.node = alias_node
@@ -6049,7 +6095,9 @@ def analyze_type_application_args(self, expr: IndexExpr) -> list[Type] | None:
             types.append(analyzed)
 
         if allow_unpack:
-            types = self.type_analyzer().check_unpacks_in_list(types)
+            # need to flatten away harmless unpacks like Unpack[tuple[int]]
+            flattened_items = flatten_nested_tuples(types)
+            types = self.type_analyzer().check_unpacks_in_list(flattened_items)
         if has_param_spec and num_args == 1 and types:
             first_arg = get_proper_type(types[0])
             single_any = len(types) == 1 and isinstance(first_arg, AnyType)
@@ -6595,16 +6643,25 @@ def lookup_fully_qualified_or_none(self, fullname: str) -> SymbolTableNode | Non
             return result
 
     def object_type(self) -> Instance:
-        return self.named_type("builtins.object")
+        if self._object_type is None:
+            self._object_type = self.named_type("builtins.object")
+        return self._object_type
 
     def str_type(self) -> Instance:
-        return self.named_type("builtins.str")
+        if self._str_type is None:
+            self._str_type = self.named_type("builtins.str")
+        return self._str_type
+
+    def function_type(self) -> Instance:
+        if self._function_type is None:
+            self._function_type = self.named_type("builtins.function")
+        return self._function_type
 
     def named_type(self, fullname: str, args: list[Type] | None = None) -> Instance:
         sym = self.lookup_fully_qualified(fullname)
         assert sym, "Internal error: attempted to construct unknown type"
         node = sym.node
-        assert isinstance(node, TypeInfo)
+        assert isinstance(node, TypeInfo), node
         if args:
             # TODO: assert len(args) == len(node.defn.type_vars)
             return Instance(node, args)
@@ -7625,7 +7682,7 @@ def refers_to_fullname(node: Expression, fullnames: str | tuple[str, ...]) -> bo
         return False
     if node.fullname in fullnames:
         return True
-    if isinstance(node.node, TypeAlias):
+    if isinstance(node.node, TypeAlias) and not node.node.python_3_12_type_alias:
         return is_named_instance(node.node.target, fullnames)
     return False
 
diff --git a/mypy/semanal_infer.py b/mypy/semanal_infer.py
index a146b56dc2d3..89a073cdad47 100644
--- a/mypy/semanal_infer.py
+++ b/mypy/semanal_infer.py
@@ -31,6 +31,7 @@ def infer_decorator_signature_if_simple(
     """
     if dec.var.is_property:
         # Decorators are expected to have a callable type (it's a little odd).
+        # TODO: this may result in wrong type if @property is applied to decorated method.
         if dec.func.type is None:
             dec.var.type = CallableType(
                 [AnyType(TypeOfAny.special_form)],
@@ -47,6 +48,8 @@ def infer_decorator_signature_if_simple(
     for expr in dec.decorators:
         preserve_type = False
         if isinstance(expr, RefExpr) and isinstance(expr.node, FuncDef):
+            if expr.fullname == "typing.no_type_check":
+                return
             if expr.node.type and is_identity_signature(expr.node.type):
                 preserve_type = True
         if not preserve_type:
diff --git a/mypy/semanal_main.py b/mypy/semanal_main.py
index 00d795c64e44..7301e9f9b9b3 100644
--- a/mypy/semanal_main.py
+++ b/mypy/semanal_main.py
@@ -290,7 +290,7 @@ def process_functions(graph: Graph, scc: list[str], patches: Patches) -> None:
 
     for module, target, node, active_type in order_by_subclassing(all_targets):
         analyzer = graph[module].manager.semantic_analyzer
-        assert isinstance(node, (FuncDef, OverloadedFuncDef, Decorator))
+        assert isinstance(node, (FuncDef, OverloadedFuncDef, Decorator)), node
         process_top_level_function(
             analyzer, graph[module], module, target, node, active_type, patches
         )
diff --git a/mypy/semanal_namedtuple.py b/mypy/semanal_namedtuple.py
index b67747d16887..37a650f1b664 100644
--- a/mypy/semanal_namedtuple.py
+++ b/mypy/semanal_namedtuple.py
@@ -606,7 +606,7 @@ def add_method(
             arg_kinds = [arg.kind for arg in args]
             assert None not in types
             signature = CallableType(cast(list[Type], types), arg_kinds, items, ret, function_type)
-            signature.variables = [self_type]
+            signature.variables = (self_type,)
             func = FuncDef(funcname, args, Block([]))
             func.info = info
             func.is_class = is_classmethod
diff --git a/mypy/semanal_pass1.py b/mypy/semanal_pass1.py
index aaa01969217a..266fd236a01f 100644
--- a/mypy/semanal_pass1.py
+++ b/mypy/semanal_pass1.py
@@ -74,6 +74,9 @@ def visit_file(self, file: MypyFile, fnam: str, mod_id: str, options: Options) -
                     if last.end_line is not None:
                         # We are on a Python version recent enough to support end lines.
                         self.skipped_lines |= set(range(next_def.line, last.end_line + 1))
+                file.imports = [
+                    i for i in file.imports if (i.line, i.column) <= (defn.line, defn.column)
+                ]
                 del file.defs[i + 1 :]
                 break
         file.skipped_lines = self.skipped_lines
diff --git a/mypy/semanal_shared.py b/mypy/semanal_shared.py
index bdd01ef6a6f3..e94604b66381 100644
--- a/mypy/semanal_shared.py
+++ b/mypy/semanal_shared.py
@@ -46,6 +46,7 @@
     TypeVarLikeType,
     TypeVarTupleType,
     UnpackType,
+    flatten_nested_tuples,
     get_proper_type,
 )
 
@@ -290,7 +291,7 @@ def calculate_tuple_fallback(typ: TupleType) -> None:
     fallback = typ.partial_fallback
     assert fallback.type.fullname == "builtins.tuple"
     items = []
-    for item in typ.items:
+    for item in flatten_nested_tuples(typ.items):
         # TODO: this duplicates some logic in typeops.tuple_fallback().
         if isinstance(item, UnpackType):
             unpacked_type = get_proper_type(item.type)
diff --git a/mypy/semanal_typeargs.py b/mypy/semanal_typeargs.py
index 435abb78ca43..be39a8259c2e 100644
--- a/mypy/semanal_typeargs.py
+++ b/mypy/semanal_typeargs.py
@@ -102,6 +102,8 @@ def visit_type_alias_type(self, t: TypeAliasType) -> None:
             # If there was already an error for the alias itself, there is no point in checking
             # the expansion, most likely it will result in the same kind of error.
             get_proper_type(t).accept(self)
+            if t.alias is not None:
+                t.alias.accept(self)
 
     def visit_tuple_type(self, t: TupleType) -> None:
         t.items = flatten_nested_tuples(t.items)
@@ -254,6 +256,10 @@ def visit_unpack_type(self, typ: UnpackType) -> None:
     def check_type_var_values(
         self, name: str, actuals: list[Type], arg_name: str, valids: list[Type], context: Context
     ) -> bool:
+        if self.in_type_alias_expr:
+            # See testValidTypeAliasValues - we do not enforce typevar compatibility
+            # at the definition site. We check instantiation validity later.
+            return False
         is_error = False
         for actual in get_proper_types(actuals):
             # We skip UnboundType here, since they may appear in defn.bases,
diff --git a/mypy/server/astdiff.py b/mypy/server/astdiff.py
index 16a0d882a8aa..1df85a163e0f 100644
--- a/mypy/server/astdiff.py
+++ b/mypy/server/astdiff.py
@@ -252,6 +252,15 @@ def snapshot_definition(node: SymbolNode | None, common: SymbolSnapshot) -> Symb
                 setter_type = snapshot_optional_type(first_item.var.setter_type)
         is_trivial_body = impl.is_trivial_body if impl else False
         dataclass_transform_spec = find_dataclass_transform_spec(node)
+
+        deprecated: str | list[str | None] | None = None
+        if isinstance(node, FuncDef):
+            deprecated = node.deprecated
+        elif isinstance(node, OverloadedFuncDef):
+            deprecated = [node.deprecated] + [
+                i.func.deprecated for i in node.items if isinstance(i, Decorator)
+            ]
+
         return (
             "Func",
             common,
@@ -262,7 +271,7 @@ def snapshot_definition(node: SymbolNode | None, common: SymbolSnapshot) -> Symb
             signature,
             is_trivial_body,
             dataclass_transform_spec.serialize() if dataclass_transform_spec is not None else None,
-            node.deprecated if isinstance(node, FuncDef) else None,
+            deprecated,
             setter_type,  # multi-part properties are stored as OverloadedFuncDef
         )
     elif isinstance(node, Var):
diff --git a/mypy/server/astmerge.py b/mypy/server/astmerge.py
index 8cd574628bb8..33e2d2b799cb 100644
--- a/mypy/server/astmerge.py
+++ b/mypy/server/astmerge.py
@@ -345,13 +345,11 @@ def visit_type_alias(self, node: TypeAlias) -> None:
     def fixup(self, node: SN) -> SN:
         if node in self.replacements:
             new = self.replacements[node]
-            skip_slots: tuple[str, ...] = ()
             if isinstance(node, TypeInfo) and isinstance(new, TypeInfo):
                 # Special case: special_alias is not exposed in symbol tables, but may appear
                 # in external types (e.g. named tuples), so we need to update it manually.
-                skip_slots = ("special_alias",)
                 replace_object_state(new.special_alias, node.special_alias)
-            replace_object_state(new, node, skip_slots=skip_slots)
+            replace_object_state(new, node, skip_slots=_get_ignored_slots(new))
             return cast(SN, new)
         return node
 
@@ -556,9 +554,16 @@ def replace_nodes_in_symbol_table(
             if node.node in replacements:
                 new = replacements[node.node]
                 old = node.node
-                # Needed for TypeInfo, see comment in fixup() above.
-                replace_object_state(new, old, skip_slots=("special_alias",))
+                replace_object_state(new, old, skip_slots=_get_ignored_slots(new))
                 node.node = new
             if isinstance(node.node, (Var, TypeAlias)):
                 # Handle them here just in case these aren't exposed through the AST.
                 node.node.accept(NodeReplaceVisitor(replacements))
+
+
+def _get_ignored_slots(node: SymbolNode) -> tuple[str, ...]:
+    if isinstance(node, OverloadedFuncDef):
+        return ("setter",)
+    if isinstance(node, TypeInfo):
+        return ("special_alias",)
+    return ()
diff --git a/mypy/server/aststrip.py b/mypy/server/aststrip.py
index a70dfc30deb5..27c1c4a0eedb 100644
--- a/mypy/server/aststrip.py
+++ b/mypy/server/aststrip.py
@@ -165,7 +165,7 @@ def visit_func_def(self, node: FuncDef) -> None:
             # in order to get the state exactly as it was before semantic analysis.
             # See also #4814.
             assert isinstance(node.type, CallableType)
-            node.type.variables = []
+            node.type.variables = ()
         with self.enter_method(node.info) if node.info else nullcontext():
             super().visit_func_def(node)
 
diff --git a/mypy/server/update.py b/mypy/server/update.py
index 9891e2417b94..839090ca45ac 100644
--- a/mypy/server/update.py
+++ b/mypy/server/update.py
@@ -668,6 +668,8 @@ def restore(ids: list[str]) -> None:
     state.type_check_first_pass()
     state.type_check_second_pass()
     state.detect_possibly_undefined_vars()
+    state.generate_unused_ignore_notes()
+    state.generate_ignore_without_code_notes()
     t2 = time.time()
     state.finish_passes()
     t3 = time.time()
@@ -1023,10 +1025,12 @@ def key(node: FineGrainedDeferredNode) -> int:
     # We seem to need additional passes in fine-grained incremental mode.
     checker.pass_num = 0
     checker.last_pass = 3
-    more = checker.check_second_pass(nodes)
+    # It is tricky to reliably invalidate constructor cache in fine-grained increments.
+    # See PR 19514 description for details.
+    more = checker.check_second_pass(nodes, allow_constructor_cache=False)
     while more:
         more = False
-        if graph[module_id].type_checker().check_second_pass():
+        if graph[module_id].type_checker().check_second_pass(allow_constructor_cache=False):
             more = True
 
     if manager.options.export_types:
diff --git a/mypy/sharedparse.py b/mypy/sharedparse.py
index ef2e4f720664..71d1dee8f7d6 100644
--- a/mypy/sharedparse.py
+++ b/mypy/sharedparse.py
@@ -10,6 +10,7 @@
     "__call__",
     "__complex__",
     "__contains__",
+    "__buffer__",
     "__del__",
     "__delattr__",
     "__delitem__",
@@ -31,6 +32,7 @@
     "__new__",
     "__oct__",
     "__pos__",
+    "__release_buffer__",
     "__repr__",
     "__reversed__",
     "__setattr__",
diff --git a/mypy/solve.py b/mypy/solve.py
index 098d926bc789..fbbcac2520ad 100644
--- a/mypy/solve.py
+++ b/mypy/solve.py
@@ -270,6 +270,7 @@ def solve_one(lowers: Iterable[Type], uppers: Iterable[Type]) -> Type | None:
     uppers = new_uppers
 
     # ...unless this is the only information we have, then we just pass it on.
+    lowers = list(lowers)
     if not uppers and not lowers:
         candidate = UninhabitedType()
         candidate.ambiguous = True
@@ -281,10 +282,11 @@ def solve_one(lowers: Iterable[Type], uppers: Iterable[Type]) -> Type | None:
     # Process each bound separately, and calculate the lower and upper
     # bounds based on constraints. Note that we assume that the constraint
     # targets do not have constraint references.
-    if type_state.infer_unions:
+    if type_state.infer_unions and lowers:
         # This deviates from the general mypy semantics because
         # recursive types are union-heavy in 95% of cases.
-        bottom = UnionType.make_union(list(lowers))
+        # Retain `None` when no bottoms were provided to avoid bogus `Never` inference.
+        bottom = UnionType.make_union(lowers)
     else:
         # The order of lowers is non-deterministic.
         # We attempt to sort lowers because joins are non-associative. For instance:
diff --git a/mypy/stubgen.py b/mypy/stubgen.py
index ece22ba235bf..60fbd7f43c0f 100755
--- a/mypy/stubgen.py
+++ b/mypy/stubgen.py
@@ -1899,8 +1899,6 @@ def parse_options(args: list[str]) -> Options:
     parser = argparse.ArgumentParser(
         prog="stubgen", usage=HEADER, description=DESCRIPTION, fromfile_prefix_chars="@"
     )
-    if sys.version_info >= (3, 14):
-        parser.color = True  # Set as init arg in 3.14
 
     parser.add_argument(
         "--ignore-errors",
diff --git a/mypy/stubinfo.py b/mypy/stubinfo.py
index 33064c9d3067..42e53ba21c84 100644
--- a/mypy/stubinfo.py
+++ b/mypy/stubinfo.py
@@ -45,7 +45,6 @@ def stub_distribution_name(module: str) -> str | None:
     "first": "types-first",
     "markdown": "types-Markdown",
     "mock": "types-mock",
-    "OpenSSL": "types-pyOpenSSL",
     "paramiko": "types-paramiko",
     "polib": "types-polib",
     "pycurl": "types-pycurl",
@@ -75,35 +74,37 @@ def stub_distribution_name(module: str) -> str | None:
 #               but is a non-typeshed stubs package.
 non_bundled_packages_flat: dict[str, str] = {
     "_cffi_backend": "types-cffi",
+    "_jsonnet": "types-jsonnet",
     "_win32typing": "types-pywin32",
     "antlr4": "types-antlr4-python3-runtime",
     "assertpy": "types-assertpy",
-    "atheris": "types-atheris",
+    "auth0": "types-auth0-python",
     "authlib": "types-Authlib",
     "aws_xray_sdk": "types-aws-xray-sdk",
+    "binaryornot": "types-binaryornot",
     "boltons": "types-boltons",
     "braintree": "types-braintree",
-    "bs4": "types-beautifulsoup4",
     "bugbear": "types-flake8-bugbear",
-    "caldav": "types-caldav",
     "capturer": "types-capturer",
     "cffi": "types-cffi",
+    "channels": "types-channels",
     "chevron": "types-chevron",
     "click_default_group": "types-click-default-group",
     "click_log": "types-click-log",
+    "click_shell": "types-click-shell",
     "click_web": "types-click-web",
     "colorama": "types-colorama",
     "commctrl": "types-pywin32",
-    "commonmark": "types-commonmark",
     "consolemenu": "types-console-menu",
-    "corus": "types-corus",  # codespell:ignore corus
+    "convertdate": "types-convertdate",
     "cronlog": "types-python-crontab",
     "crontab": "types-python-crontab",
     "crontabs": "types-python-crontab",
-    "datemath": "types-python-datemath",
     "dateparser_data": "types-dateparser",
     "dde": "types-pywin32",
     "defusedxml": "types-defusedxml",
+    "dirhash": "types-dirhash",
+    "django_filters": "types-django-filter",
     "docker": "types-docker",
     "dockerfile_parse": "types-dockerfile-parse",
     "editdistance": "types-editdistance",
@@ -122,17 +123,22 @@ def stub_distribution_name(module: str) -> str | None:
     "flask_socketio": "types-Flask-SocketIO",
     "fpdf": "types-fpdf2",
     "gdb": "types-gdb",
+    "geopandas": "types-geopandas",
     "gevent": "types-gevent",
     "greenlet": "types-greenlet",
+    "grpc_channelz": "types-grpcio-channelz",
+    "grpc_health": "types-grpcio-health-checking",
+    "grpc_reflection": "types-grpcio-reflection",
+    "grpc_status": "types-grpcio-status",
+    "grpc": "types-grpcio",
     "hdbcli": "types-hdbcli",
+    "hnswlib": "types-hnswlib",
     "html5lib": "types-html5lib",
     "httplib2": "types-httplib2",
-    "humanfriendly": "types-humanfriendly",
     "hvac": "types-hvac",
     "ibm_db": "types-ibm-db",
     "icalendar": "types-icalendar",
     "import_export": "types-django-import-export",
-    "influxdb_client": "types-influxdb-client",
     "inifile": "types-inifile",
     "isapi": "types-pywin32",
     "jack": "types-JACK-Client",
@@ -145,9 +151,11 @@ def stub_distribution_name(module: str) -> str | None:
     "jwcrypto": "types-jwcrypto",
     "keyboard": "types-keyboard",
     "ldap3": "types-ldap3",
+    "lunardate": "types-lunardate",
     "lupa": "types-lupa",
     "lzstring": "types-lzstring",
     "m3u8": "types-m3u8",
+    "management": "types-django-import-export",
     "mmapfile": "types-pywin32",
     "mmsystem": "types-pywin32",
     "mypy_extensions": "types-mypy-extensions",
@@ -173,6 +181,7 @@ def stub_distribution_name(module: str) -> str | None:
     "perfmon": "types-pywin32",
     "pexpect": "types-pexpect",
     "playhouse": "types-peewee",
+    "pony": "types-pony",
     "portpicker": "types-portpicker",
     "psutil": "types-psutil",
     "psycopg2": "types-psycopg2",
@@ -181,11 +190,13 @@ def stub_distribution_name(module: str) -> str | None:
     "pyautogui": "types-PyAutoGUI",
     "pycocotools": "types-pycocotools",
     "pyflakes": "types-pyflakes",
-    "pygit2": "types-pygit2",
     "pygments": "types-Pygments",
     "pyi_splash": "types-pyinstaller",
     "PyInstaller": "types-pyinstaller",
+    "pyluach": "types-pyluach",
+    "pymeeus": "types-PyMeeus",
     "pynput": "types-pynput",
+    "pyperclip": "types-pyperclip",
     "pyscreeze": "types-PyScreeze",
     "pysftp": "types-pysftp",
     "pytest_lazyfixture": "types-pytest-lazy-fixture",
@@ -195,10 +206,12 @@ def stub_distribution_name(module: str) -> str | None:
     "pywintypes": "types-pywin32",
     "qrbill": "types-qrbill",
     "qrcode": "types-qrcode",
+    "ratelimit": "types-ratelimit",
     "regex": "types-regex",
     "regutil": "types-pywin32",
     "reportlab": "types-reportlab",
     "requests_oauthlib": "types-requests-oauthlib",
+    "rfc3339_validator": "types-rfc3339-validator",
     "RPi": "types-RPi.GPIO",
     "s2clientprotocol": "types-s2clientprotocol",
     "sass": "types-libsass",
@@ -210,6 +223,8 @@ def stub_distribution_name(module: str) -> str | None:
     "setuptools": "types-setuptools",
     "shapely": "types-shapely",
     "slumber": "types-slumber",
+    "socks": "types-PySocks",
+    "sockshandler": "types-PySocks",
     "sspicon": "types-pywin32",
     "str2bool": "types-str2bool",
     "tensorflow": "types-tensorflow",
@@ -218,7 +233,6 @@ def stub_distribution_name(module: str) -> str | None:
     "toposort": "types-toposort",
     "tqdm": "types-tqdm",
     "translationstring": "types-translationstring",
-    "tree_sitter_languages": "types-tree-sitter-languages",
     "ttkthemes": "types-ttkthemes",
     "unidiff": "types-unidiff",
     "untangle": "types-untangle",
@@ -226,6 +240,7 @@ def stub_distribution_name(module: str) -> str | None:
     "uwsgi": "types-uWSGI",
     "uwsgidecorators": "types-uWSGI",
     "vobject": "types-vobject",
+    "watchpoints": "types-watchpoints",
     "webob": "types-WebOb",
     "whatthepatch": "types-whatthepatch",
     "win2kras": "types-pywin32",
@@ -282,7 +297,9 @@ def stub_distribution_name(module: str) -> str | None:
     "xdg": "types-pyxdg",
     "xdgenvpy": "types-xdgenvpy",
     "Xlib": "types-python-xlib",
+    "xlrd": "types-xlrd",
     "xmltodict": "types-xmltodict",
+    "yt_dlp": "types-yt-dlp",
     "zstd": "types-zstd",
     "zxcvbn": "types-zxcvbn",
     # Stub packages that are not from typeshed
diff --git a/mypy/stubtest.py b/mypy/stubtest.py
index f9e6f7d337be..4126f3959ee1 100644
--- a/mypy/stubtest.py
+++ b/mypy/stubtest.py
@@ -17,6 +17,7 @@
 import os
 import pkgutil
 import re
+import struct
 import symtable
 import sys
 import traceback
@@ -33,6 +34,9 @@
 from typing_extensions import get_origin, is_typeddict
 
 import mypy.build
+import mypy.checkexpr
+import mypy.checkmember
+import mypy.erasetype
 import mypy.modulefinder
 import mypy.nodes
 import mypy.state
@@ -136,6 +140,11 @@ def is_positional_only_related(self) -> bool:
         # TODO: This is hacky, use error codes or something more resilient
         return "should be positional" in self.message
 
+    def is_disjoint_base_related(self) -> bool:
+        """Whether or not the error is related to @disjoint_base."""
+        # TODO: This is hacky, use error codes or something more resilient
+        return "@disjoint_base" in self.message
+
     def get_description(self, concise: bool = False) -> str:
         """Returns a description of the error.
 
@@ -466,6 +475,98 @@ class SubClass(runtime):  # type: ignore[misc]
         )
 
 
+SIZEOF_PYOBJECT = struct.calcsize("P")
+
+
+def _shape_differs(t1: type[object], t2: type[object]) -> bool:
+    """Check whether two types differ in shape.
+
+    Mirrors the shape_differs() function in typeobject.c in CPython."""
+    if sys.version_info >= (3, 12):
+        return t1.__basicsize__ != t2.__basicsize__ or t1.__itemsize__ != t2.__itemsize__
+    else:
+        # CPython had more complicated logic before 3.12:
+        # https://github.com/python/cpython/blob/f3c6f882cddc8dc30320d2e73edf019e201394fc/Objects/typeobject.c#L2224
+        # We attempt to mirror it here well enough to support the most common cases.
+        if t1.__itemsize__ or t2.__itemsize__:
+            return t1.__basicsize__ != t2.__basicsize__ or t1.__itemsize__ != t2.__itemsize__
+        t_size = t1.__basicsize__
+        if not t2.__weakrefoffset__ and t1.__weakrefoffset__ + SIZEOF_PYOBJECT == t_size:
+            t_size -= SIZEOF_PYOBJECT
+        if not t2.__dictoffset__ and t1.__dictoffset__ + SIZEOF_PYOBJECT == t_size:
+            t_size -= SIZEOF_PYOBJECT
+        if not t2.__weakrefoffset__ and t2.__weakrefoffset__ == t_size:
+            t_size -= SIZEOF_PYOBJECT
+        return t_size != t2.__basicsize__
+
+
+def _is_disjoint_base(typ: type[object]) -> bool:
+    """Return whether a type is a disjoint base at runtime, mirroring CPython's logic in typeobject.c.
+
+    See PEP 800."""
+    if typ is object:
+        return True
+    base = typ.__base__
+    assert base is not None, f"Type {typ} has no base"
+    return _shape_differs(typ, base)
+
+
+def _verify_disjoint_base(
+    stub: nodes.TypeInfo, runtime: type[object], object_path: list[str]
+) -> Iterator[Error]:
+    is_disjoint_runtime = _is_disjoint_base(runtime)
+    # Don't complain about missing @disjoint_base if there are __slots__, because
+    # in that case we can infer that it's a disjoint base.
+    if (
+        is_disjoint_runtime
+        and not stub.is_disjoint_base
+        and not runtime.__dict__.get("__slots__")
+        and not stub.is_final
+        and not (stub.is_enum and stub.enum_members)
+    ):
+        yield Error(
+            object_path,
+            "is a disjoint base at runtime, but isn't marked with @disjoint_base in the stub",
+            stub,
+            runtime,
+            stub_desc=repr(stub),
+        )
+    elif stub.is_disjoint_base:
+        if not is_disjoint_runtime:
+            yield Error(
+                object_path,
+                "is marked with @disjoint_base in the stub, but isn't a disjoint base at runtime",
+                stub,
+                runtime,
+                stub_desc=repr(stub),
+            )
+        if runtime.__dict__.get("__slots__"):
+            yield Error(
+                object_path,
+                "is marked as @disjoint_base, but also has slots; add __slots__ instead",
+                stub,
+                runtime,
+                stub_desc=repr(stub),
+            )
+        elif stub.is_final:
+            yield Error(
+                object_path,
+                "is marked as @disjoint_base, but also marked as @final; remove @disjoint_base",
+                stub,
+                runtime,
+                stub_desc=repr(stub),
+            )
+        elif stub.is_enum and stub.enum_members:
+            yield Error(
+                object_path,
+                "is marked as @disjoint_base, but is an enum with members, which is implicitly final; "
+                "remove @disjoint_base",
+                stub,
+                runtime,
+                stub_desc=repr(stub),
+            )
+
+
 def _verify_metaclass(
     stub: nodes.TypeInfo, runtime: type[Any], object_path: list[str], *, is_runtime_typeddict: bool
 ) -> Iterator[Error]:
@@ -506,9 +607,13 @@ def _verify_metaclass(
 
 @verify.register(nodes.TypeInfo)
 def verify_typeinfo(
-    stub: nodes.TypeInfo, runtime: MaybeMissing[type[Any]], object_path: list[str]
+    stub: nodes.TypeInfo,
+    runtime: MaybeMissing[type[Any]],
+    object_path: list[str],
+    *,
+    is_alias_target: bool = False,
 ) -> Iterator[Error]:
-    if stub.is_type_check_only:
+    if stub.is_type_check_only and not is_alias_target:
         # This type only exists in stubs, we only check that the runtime part
         # is missing. Other checks are not required.
         if not isinstance(runtime, Missing):
@@ -530,6 +635,7 @@ def verify_typeinfo(
         return
 
     yield from _verify_final(stub, runtime, object_path)
+    yield from _verify_disjoint_base(stub, runtime, object_path)
     is_runtime_typeddict = stub.typeddict_type is not None and is_typeddict(runtime)
     yield from _verify_metaclass(
         stub, runtime, object_path, is_runtime_typeddict=is_runtime_typeddict
@@ -678,8 +784,8 @@ def names_approx_match(a: str, b: str) -> bool:
     if stub_arg.variable.name == "_self":
         return
     yield (
-        f'stub argument "{stub_arg.variable.name}" '
-        f'differs from runtime argument "{runtime_arg.name}"'
+        f'stub parameter "{stub_arg.variable.name}" '
+        f'differs from runtime parameter "{runtime_arg.name}"'
     )
 
 
@@ -690,11 +796,15 @@ def _verify_arg_default_value(
     if runtime_arg.default is not inspect.Parameter.empty:
         if stub_arg.kind.is_required():
             yield (
-                f'runtime argument "{runtime_arg.name}" '
-                "has a default value but stub argument does not"
+                f'runtime parameter "{runtime_arg.name}" '
+                "has a default value but stub parameter does not"
             )
         else:
-            runtime_type = get_mypy_type_of_runtime_value(runtime_arg.default)
+            type_context = stub_arg.variable.type
+            runtime_type = get_mypy_type_of_runtime_value(
+                runtime_arg.default, type_context=type_context
+            )
+
             # Fallback to the type annotation type if var type is missing. The type annotation
             # is an UnboundType, but I don't know enough to know what the pros and cons here are.
             # UnboundTypes have ugly question marks following them, so default to var type.
@@ -712,9 +822,9 @@ def _verify_arg_default_value(
                 and not is_subtype_helper(runtime_type, stub_type)
             ):
                 yield (
-                    f'runtime argument "{runtime_arg.name}" '
+                    f'runtime parameter "{runtime_arg.name}" '
                     f"has a default value of type {runtime_type}, "
-                    f"which is incompatible with stub argument type {stub_type}"
+                    f"which is incompatible with stub parameter type {stub_type}"
                 )
             if stub_arg.initializer is not None:
                 stub_default = evaluate_expression(stub_arg.initializer)
@@ -738,15 +848,15 @@ def _verify_arg_default_value(
                             defaults_match = False
                     if not defaults_match:
                         yield (
-                            f'runtime argument "{runtime_arg.name}" '
+                            f'runtime parameter "{runtime_arg.name}" '
                             f"has a default value of {runtime_arg.default!r}, "
-                            f"which is different from stub argument default {stub_default!r}"
+                            f"which is different from stub parameter default {stub_default!r}"
                         )
     else:
         if stub_arg.kind.is_optional():
             yield (
-                f'stub argument "{stub_arg.variable.name}" has a default value '
-                f"but runtime argument does not"
+                f'stub parameter "{stub_arg.variable.name}" has a default value '
+                f"but runtime parameter does not"
             )
 
 
@@ -856,21 +966,36 @@ def from_overloadedfuncdef(stub: nodes.OverloadedFuncDef) -> Signature[nodes.Arg
         # For most dunder methods, just assume all args are positional-only
         assume_positional_only = is_dunder(stub.name, exclude_special=True)
 
-        all_args: dict[str, list[tuple[nodes.Argument, int]]] = {}
+        is_arg_pos_only: defaultdict[str, set[bool]] = defaultdict(set)
         for func in map(_resolve_funcitem_from_decorator, stub.items):
             assert func is not None, "Failed to resolve decorated overload"
             args = maybe_strip_cls(stub.name, func.arguments)
             for index, arg in enumerate(args):
-                # For positional-only args, we allow overloads to have different names for the same
-                # argument. To accomplish this, we just make up a fake index-based name.
-                name = (
-                    f"__{index}"
-                    if arg.variable.name.startswith("__")
+                if (
+                    arg.variable.name.startswith("__")
                     or arg.pos_only
                     or assume_positional_only
                     or arg.variable.name.strip("_") == "self"
-                    else arg.variable.name
-                )
+                    or (index == 0 and arg.variable.name.strip("_") == "cls")
+                ):
+                    is_arg_pos_only[arg.variable.name].add(True)
+                else:
+                    is_arg_pos_only[arg.variable.name].add(False)
+
+        all_args: dict[str, list[tuple[nodes.Argument, int]]] = {}
+        for func in map(_resolve_funcitem_from_decorator, stub.items):
+            assert func is not None, "Failed to resolve decorated overload"
+            args = maybe_strip_cls(stub.name, func.arguments)
+            for index, arg in enumerate(args):
+                # For positional-only args, we allow overloads to have different names for the same
+                # argument. To accomplish this, we just make up a fake index-based name.
+                # We can only use the index-based name if the argument is always
+                # positional only. Sometimes overloads have an arg as positional-only
+                # in some but not all branches of the overload.
+                name = arg.variable.name
+                if is_arg_pos_only[name] == {True}:
+                    name = f"__{index}"
+
                 all_args.setdefault(name, []).append((arg, index))
 
         def get_position(arg_name: str) -> int:
@@ -928,7 +1053,10 @@ def get_kind(arg_name: str) -> nodes.ArgKind:
 
 
 def _verify_signature(
-    stub: Signature[nodes.Argument], runtime: Signature[inspect.Parameter], function_name: str
+    stub: Signature[nodes.Argument],
+    runtime: Signature[inspect.Parameter],
+    function_name: str,
+    warn_runtime_is_object_init: bool = False,
 ) -> Iterator[str]:
     # Check positional arguments match up
     for stub_arg, runtime_arg in zip(stub.pos, runtime.pos):
@@ -939,10 +1067,11 @@ def _verify_signature(
             and not stub_arg.pos_only
             and not stub_arg.variable.name.startswith("__")
             and stub_arg.variable.name.strip("_") != "self"
+            and stub_arg.variable.name.strip("_") != "cls"
             and not is_dunder(function_name, exclude_special=True)  # noisy for dunder methods
         ):
             yield (
-                f'stub argument "{stub_arg.variable.name}" should be positional-only '
+                f'stub parameter "{stub_arg.variable.name}" should be positional-only '
                 f'(add "/", e.g. "{runtime_arg.name}, /")'
             )
         if (
@@ -950,10 +1079,11 @@ def _verify_signature(
             and (stub_arg.pos_only or stub_arg.variable.name.startswith("__"))
             and not runtime_arg.name.startswith("__")
             and stub_arg.variable.name.strip("_") != "self"
+            and stub_arg.variable.name.strip("_") != "cls"
             and not is_dunder(function_name, exclude_special=True)  # noisy for dunder methods
         ):
             yield (
-                f'stub argument "{stub_arg.variable.name}" should be positional or keyword '
+                f'stub parameter "{stub_arg.variable.name}" should be positional or keyword '
                 '(remove "/")'
             )
 
@@ -968,28 +1098,30 @@ def _verify_signature(
                 # If the variable is in runtime.kwonly, it's just mislabelled as not a
                 # keyword-only argument
                 if stub_arg.variable.name not in runtime.kwonly:
-                    msg = f'runtime does not have argument "{stub_arg.variable.name}"'
+                    msg = f'runtime does not have parameter "{stub_arg.variable.name}"'
                     if runtime.varkw is not None:
                         msg += ". Maybe you forgot to make it keyword-only in the stub?"
+                    elif warn_runtime_is_object_init:
+                        msg += ". You may need to write stubs for __new__ instead of __init__."
                     yield msg
                 else:
-                    yield f'stub argument "{stub_arg.variable.name}" is not keyword-only'
+                    yield f'stub parameter "{stub_arg.variable.name}" is not keyword-only'
             if stub.varpos is not None:
-                yield f'runtime does not have *args argument "{stub.varpos.variable.name}"'
+                yield f'runtime does not have *args parameter "{stub.varpos.variable.name}"'
     elif len(stub.pos) < len(runtime.pos):
         for runtime_arg in runtime.pos[len(stub.pos) :]:
             if runtime_arg.name not in stub.kwonly:
                 if not _is_private_parameter(runtime_arg):
-                    yield f'stub does not have argument "{runtime_arg.name}"'
+                    yield f'stub does not have parameter "{runtime_arg.name}"'
             else:
-                yield f'runtime argument "{runtime_arg.name}" is not keyword-only'
+                yield f'runtime parameter "{runtime_arg.name}" is not keyword-only'
 
     # Checks involving *args
     if len(stub.pos) <= len(runtime.pos) or runtime.varpos is None:
         if stub.varpos is None and runtime.varpos is not None:
-            yield f'stub does not have *args argument "{runtime.varpos.name}"'
+            yield f'stub does not have *args parameter "{runtime.varpos.name}"'
         if stub.varpos is not None and runtime.varpos is None:
-            yield f'runtime does not have *args argument "{stub.varpos.variable.name}"'
+            yield f'runtime does not have *args parameter "{stub.varpos.variable.name}"'
 
     # Check keyword-only args
     for arg in sorted(set(stub.kwonly) & set(runtime.kwonly)):
@@ -1008,9 +1140,13 @@ def _verify_signature(
             if arg in {runtime_arg.name for runtime_arg in runtime.pos}:
                 # Don't report this if we've reported it before
                 if arg not in {runtime_arg.name for runtime_arg in runtime.pos[len(stub.pos) :]}:
-                    yield f'runtime argument "{arg}" is not keyword-only'
+                    yield f'runtime parameter "{arg}" is not keyword-only'
             else:
-                yield f'runtime does not have argument "{arg}"'
+                msg = f'runtime does not have parameter "{arg}"'
+                if warn_runtime_is_object_init:
+                    msg += ". You may need to write stubs for __new__ instead of __init__."
+                yield msg
+
     for arg in sorted(set(runtime.kwonly) - set(stub.kwonly)):
         if arg in {stub_arg.variable.name for stub_arg in stub.pos}:
             # Don't report this if we've reported it before
@@ -1018,10 +1154,10 @@ def _verify_signature(
                 runtime.varpos is None
                 and arg in {stub_arg.variable.name for stub_arg in stub.pos[len(runtime.pos) :]}
             ):
-                yield f'stub argument "{arg}" is not keyword-only'
+                yield f'stub parameter "{arg}" is not keyword-only'
         else:
             if not _is_private_parameter(runtime.kwonly[arg]):
-                yield f'stub does not have argument "{arg}"'
+                yield f'stub does not have parameter "{arg}"'
 
     # Checks involving **kwargs
     if stub.varkw is None and runtime.varkw is not None:
@@ -1031,9 +1167,9 @@ def _verify_signature(
         stub_pos_names = {stub_arg.variable.name for stub_arg in stub.pos}
         # Ideally we'd do a strict subset check, but in practice the errors from that aren't useful
         if not set(runtime.kwonly).issubset(set(stub.kwonly) | stub_pos_names):
-            yield f'stub does not have **kwargs argument "{runtime.varkw.name}"'
+            yield f'stub does not have **kwargs parameter "{runtime.varkw.name}"'
     if stub.varkw is not None and runtime.varkw is None:
-        yield f'runtime does not have **kwargs argument "{stub.varkw.variable.name}"'
+        yield f'runtime does not have **kwargs parameter "{stub.varkw.variable.name}"'
 
 
 def _is_private_parameter(arg: inspect.Parameter) -> bool:
@@ -1096,7 +1232,12 @@ def verify_funcitem(
     if not signature:
         return
 
-    for message in _verify_signature(stub_sig, runtime_sig, function_name=stub.name):
+    for message in _verify_signature(
+        stub_sig,
+        runtime_sig,
+        function_name=stub.name,
+        warn_runtime_is_object_init=runtime is object.__init__,
+    ):
         yield Error(
             object_path,
             "is inconsistent, " + message,
@@ -1132,7 +1273,7 @@ def verify_var(
     ):
         yield Error(object_path, "is read-only at runtime but not in the stub", stub, runtime)
 
-    runtime_type = get_mypy_type_of_runtime_value(runtime)
+    runtime_type = get_mypy_type_of_runtime_value(runtime, type_context=stub.type)
     if (
         runtime_type is not None
         and stub.type is not None
@@ -1149,7 +1290,7 @@ def verify_var(
             proper_type = mypy.types.get_proper_type(stub.type)
             if (
                 isinstance(proper_type, mypy.types.Instance)
-                and proper_type.type.fullname == "builtins.ellipsis"
+                and proper_type.type.fullname in mypy.types.ELLIPSIS_TYPE_NAMES
             ):
                 should_error = False
 
@@ -1206,7 +1347,12 @@ def verify_overloadedfuncdef(
     stub_sig = Signature.from_overloadedfuncdef(stub)
     runtime_sig = Signature.from_inspect_signature(signature)
 
-    for message in _verify_signature(stub_sig, runtime_sig, function_name=stub.name):
+    for message in _verify_signature(
+        stub_sig,
+        runtime_sig,
+        function_name=stub.name,
+        warn_runtime_is_object_init=runtime is object.__init__,
+    ):
         # TODO: This is a little hacky, but the addition here is super useful
         if "has a default value of type" in message:
             message += (
@@ -1353,7 +1499,7 @@ def apply_decorator_to_funcitem(
         if decorator.fullname == "builtins.classmethod":
             if func.arguments[0].variable.name not in ("cls", "mcs", "metacls"):
                 raise StubtestFailure(
-                    f"unexpected class argument name {func.arguments[0].variable.name!r} "
+                    f"unexpected class parameter name {func.arguments[0].variable.name!r} "
                     f"in {dec.fullname}"
                 )
             # FuncItem is written so that copy.copy() actually works, even when compiled
@@ -1449,7 +1595,7 @@ def verify_typealias(
         # Okay, either we couldn't construct a fullname
         # or the fullname of the stub didn't match the fullname of the runtime.
         # Fallback to a full structural check of the runtime vis-a-vis the stub.
-        yield from verify(stub_origin, runtime_origin, object_path)
+        yield from verify_typeinfo(stub_origin, runtime_origin, object_path, is_alias_target=True)
         return
     if isinstance(stub_target, mypy.types.UnionType):
         # complain if runtime is not a Union or UnionType
@@ -1593,6 +1739,71 @@ def is_read_only_property(runtime: object) -> bool:
 
 
 def safe_inspect_signature(runtime: Any) -> inspect.Signature | None:
+    if (
+        hasattr(runtime, "__name__")
+        and runtime.__name__ == "__init__"
+        and hasattr(runtime, "__text_signature__")
+        and runtime.__text_signature__ == "($self, /, *args, **kwargs)"
+        and hasattr(runtime, "__objclass__")
+        and hasattr(runtime.__objclass__, "__text_signature__")
+        and runtime.__objclass__.__text_signature__ is not None
+    ):
+        # This is an __init__ method with the generic C-class signature.
+        # In this case, the underlying class often has a better signature,
+        # which we can convert into an __init__ signature by adding in the
+        # self parameter.
+        try:
+            s = inspect.signature(runtime.__objclass__)
+
+            parameter_kind: inspect._ParameterKind = inspect.Parameter.POSITIONAL_OR_KEYWORD
+            if s.parameters:
+                first_parameter = next(iter(s.parameters.values()))
+                if first_parameter.kind == inspect.Parameter.POSITIONAL_ONLY:
+                    parameter_kind = inspect.Parameter.POSITIONAL_ONLY
+            return s.replace(
+                parameters=[inspect.Parameter("self", parameter_kind), *s.parameters.values()]
+            )
+        except Exception:
+            pass
+
+    if (
+        hasattr(runtime, "__name__")
+        and runtime.__name__ == "__new__"
+        and hasattr(runtime, "__text_signature__")
+        and runtime.__text_signature__ == "($type, *args, **kwargs)"
+        and hasattr(runtime, "__self__")
+        and hasattr(runtime.__self__, "__text_signature__")
+        and runtime.__self__.__text_signature__ is not None
+    ):
+        # This is a __new__ method with the generic C-class signature.
+        # In this case, the underlying class often has a better signature,
+        # which we can convert into a __new__ signature by adding in the
+        # cls parameter.
+
+        # If the attached class has a valid __init__, skip recovering a
+        # signature for this __new__ method.
+        has_init = False
+        if (
+            hasattr(runtime.__self__, "__init__")
+            and hasattr(runtime.__self__.__init__, "__objclass__")
+            and runtime.__self__.__init__.__objclass__ is runtime.__self__
+        ):
+            has_init = True
+
+        if not has_init:
+            try:
+                s = inspect.signature(runtime.__self__)
+                parameter_kind = inspect.Parameter.POSITIONAL_OR_KEYWORD
+                if s.parameters:
+                    first_parameter = next(iter(s.parameters.values()))
+                    if first_parameter.kind == inspect.Parameter.POSITIONAL_ONLY:
+                        parameter_kind = inspect.Parameter.POSITIONAL_ONLY
+                return s.replace(
+                    parameters=[inspect.Parameter("cls", parameter_kind), *s.parameters.values()]
+                )
+            except Exception:
+                pass
+
     try:
         try:
             return inspect.signature(runtime)
@@ -1652,7 +1863,18 @@ def is_subtype_helper(left: mypy.types.Type, right: mypy.types.Type) -> bool:
         return mypy.subtypes.is_subtype(left, right)
 
 
-def get_mypy_type_of_runtime_value(runtime: Any) -> mypy.types.Type | None:
+def get_mypy_node_for_name(module: str, type_name: str) -> mypy.nodes.SymbolNode | None:
+    stub = get_stub(module)
+    if stub is None:
+        return None
+    if type_name not in stub.names:
+        return None
+    return stub.names[type_name].node
+
+
+def get_mypy_type_of_runtime_value(
+    runtime: Any, type_context: mypy.types.Type | None = None
+) -> mypy.types.Type | None:
     """Returns a mypy type object representing the type of ``runtime``.
 
     Returns None if we can't find something that works.
@@ -1713,14 +1935,45 @@ def anytype() -> mypy.types.AnyType:
             is_ellipsis_args=True,
         )
 
-    # Try and look up a stub for the runtime object
-    stub = get_stub(type(runtime).__module__)
-    if stub is None:
-        return None
-    type_name = type(runtime).__name__
-    if type_name not in stub.names:
+    skip_type_object_type = False
+    if type_context:
+        # Don't attempt to process the type object when context is generic
+        # This is related to issue #3737
+        type_context = mypy.types.get_proper_type(type_context)
+        # Callable types with a generic return value
+        if isinstance(type_context, mypy.types.CallableType):
+            if isinstance(type_context.ret_type, mypy.types.TypeVarType):
+                skip_type_object_type = True
+        # Type[x] where x is generic
+        if isinstance(type_context, mypy.types.TypeType):
+            if isinstance(type_context.item, mypy.types.TypeVarType):
+                skip_type_object_type = True
+
+    if isinstance(runtime, type) and not skip_type_object_type:
+
+        def _named_type(name: str) -> mypy.types.Instance:
+            parts = name.rsplit(".", maxsplit=1)
+            node = get_mypy_node_for_name(parts[0], parts[1])
+            assert isinstance(node, nodes.TypeInfo)
+            any_type = mypy.types.AnyType(mypy.types.TypeOfAny.special_form)
+            return mypy.types.Instance(node, [any_type] * len(node.defn.type_vars))
+
+        # Try and look up a stub for the runtime object itself
+        # The logic here is similar to ExpressionChecker.analyze_ref_expr
+        type_info = get_mypy_node_for_name(runtime.__module__, runtime.__name__)
+        if isinstance(type_info, nodes.TypeInfo):
+            result: mypy.types.Type | None = None
+            result = mypy.typeops.type_object_type(type_info, _named_type)
+            if mypy.checkexpr.is_type_type_context(type_context):
+                # This is the type in a type[] expression, so substitute type
+                # variables with Any.
+                result = mypy.erasetype.erase_typevars(result)
+            return result
+
+    # Try and look up a stub for the runtime object's type
+    type_info = get_mypy_node_for_name(type(runtime).__module__, type(runtime).__name__)
+    if type_info is None:
         return None
-    type_info = stub.names[type_name].node
     if isinstance(type_info, nodes.Var):
         return type_info.type
     if not isinstance(type_info, nodes.TypeInfo):
@@ -1952,6 +2205,7 @@ class _Arguments:
     concise: bool
     ignore_missing_stub: bool
     ignore_positional_only: bool
+    ignore_disjoint_bases: bool
     allowlist: list[str]
     generate_allowlist: bool
     ignore_unused_allowlist: bool
@@ -2045,6 +2299,8 @@ def warning_callback(msg: str) -> None:
                 continue
             if args.ignore_positional_only and error.is_positional_only_related():
                 continue
+            if args.ignore_disjoint_bases and error.is_disjoint_base_related():
+                continue
             if error.object_desc in allowlist:
                 allowlist[error.object_desc] = True
                 continue
@@ -2062,7 +2318,7 @@ def warning_callback(msg: str) -> None:
             if args.generate_allowlist:
                 generated_allowlist.add(error.object_desc)
                 continue
-            print(error.get_description(concise=args.concise))
+            safe_print(error.get_description(concise=args.concise))
             error_count += 1
 
     # Print unused allowlist entries
@@ -2102,12 +2358,23 @@ def warning_callback(msg: str) -> None:
     return exit_code
 
 
+def safe_print(text: str) -> None:
+    """Print a text replacing chars not representable in stdout encoding."""
+    # If `sys.stdout` encoding is not the same as out (usually UTF8) string,
+    # if may cause painful crashes. I don't want to reconfigure `sys.stdout`
+    # to do `errors = "replace"` as that sounds scary.
+    out_encoding = sys.stdout.encoding
+    if out_encoding is not None:
+        # Can be None if stdout is replaced (including our own tests). This should be
+        # safe to omit if the actual stream doesn't care about encoding.
+        text = text.encode(out_encoding, errors="replace").decode(out_encoding, errors="replace")
+    print(text)
+
+
 def parse_options(args: list[str]) -> _Arguments:
     parser = argparse.ArgumentParser(
         description="Compares stubs to objects introspected from the runtime."
     )
-    if sys.version_info >= (3, 14):
-        parser.color = True  # Set as init arg in 3.14
     parser.add_argument("modules", nargs="*", help="Modules to test")
     parser.add_argument(
         "--concise",
@@ -2124,6 +2391,12 @@ def parse_options(args: list[str]) -> _Arguments:
         action="store_true",
         help="Ignore errors for whether an argument should or shouldn't be positional-only",
     )
+    # TODO: Remove once PEP 800 is accepted
+    parser.add_argument(
+        "--ignore-disjoint-bases",
+        action="store_true",
+        help="Disable checks for PEP 800 @disjoint_base classes",
+    )
     parser.add_argument(
         "--allowlist",
         "--whitelist",
diff --git a/mypy/subtypes.py b/mypy/subtypes.py
index acb41609fdc5..7da258a827f3 100644
--- a/mypy/subtypes.py
+++ b/mypy/subtypes.py
@@ -145,6 +145,8 @@ def is_subtype(
     between the type arguments (e.g., A and B), taking the variance of the
     type var into account.
     """
+    if left == right:
+        return True
     if subtype_context is None:
         subtype_context = SubtypeContext(
             ignore_type_params=ignore_type_params,
@@ -155,15 +157,13 @@ def is_subtype(
             options=options,
         )
     else:
-        assert not any(
-            {
-                ignore_type_params,
-                ignore_pos_arg_names,
-                ignore_declared_variance,
-                always_covariant,
-                ignore_promotions,
-                options,
-            }
+        assert (
+            not ignore_type_params
+            and not ignore_pos_arg_names
+            and not ignore_declared_variance
+            and not always_covariant
+            and not ignore_promotions
+            and options is None
         ), "Don't pass both context and individual flags"
     if type_state.is_assumed_subtype(left, right):
         return True
@@ -208,6 +208,8 @@ def is_proper_subtype(
     (this is useful for runtime isinstance() checks). If keep_erased_types is True,
     do not consider ErasedType a subtype of all types (used by type inference against unions).
     """
+    if left == right:
+        return True
     if subtype_context is None:
         subtype_context = SubtypeContext(
             ignore_promotions=ignore_promotions,
@@ -215,8 +217,8 @@ def is_proper_subtype(
             keep_erased_types=keep_erased_types,
         )
     else:
-        assert not any(
-            {ignore_promotions, erase_instances, keep_erased_types}
+        assert (
+            not ignore_promotions and not erase_instances and not keep_erased_types
         ), "Don't pass both context and individual flags"
     if type_state.is_assumed_proper_subtype(left, right):
         return True
@@ -392,6 +394,15 @@ def check_type_parameter(
 
 
 class SubtypeVisitor(TypeVisitor[bool]):
+    __slots__ = (
+        "right",
+        "orig_right",
+        "proper_subtype",
+        "subtype_context",
+        "options",
+        "_subtype_kind",
+    )
+
     def __init__(self, right: Type, subtype_context: SubtypeContext, proper_subtype: bool) -> None:
         self.right = get_proper_type(right)
         self.orig_right = right
@@ -1457,7 +1468,8 @@ def get_member_flags(name: str, itype: Instance, class_obj: bool = False) -> set
         flags = {IS_VAR}
         if not v.is_final:
             flags.add(IS_SETTABLE)
-        if v.is_classvar:
+        # TODO: define cleaner rules for class vs instance variables.
+        if v.is_classvar and not is_descriptor(v.type):
             flags.add(IS_CLASSVAR)
         if class_obj and v.is_inferred:
             flags.add(IS_CLASSVAR)
@@ -1465,6 +1477,15 @@ def get_member_flags(name: str, itype: Instance, class_obj: bool = False) -> set
     return set()
 
 
+def is_descriptor(typ: Type | None) -> bool:
+    typ = get_proper_type(typ)
+    if isinstance(typ, Instance):
+        return typ.type.get("__get__") is not None
+    if isinstance(typ, UnionType):
+        return all(is_descriptor(item) for item in typ.relevant_items())
+    return False
+
+
 def find_node_type(
     node: Var | FuncBase,
     itype: Instance,
@@ -2063,7 +2084,7 @@ def try_restrict_literal_union(t: UnionType, s: Type) -> list[Type] | None:
     return new_items
 
 
-def restrict_subtype_away(t: Type, s: Type) -> Type:
+def restrict_subtype_away(t: Type, s: Type, *, consider_runtime_isinstance: bool = True) -> Type:
     """Return t minus s for runtime type assertions.
 
     If we can't determine a precise result, return a supertype of the
@@ -2077,16 +2098,27 @@ def restrict_subtype_away(t: Type, s: Type) -> Type:
         new_items = try_restrict_literal_union(p_t, s)
         if new_items is None:
             new_items = [
-                restrict_subtype_away(item, s)
+                restrict_subtype_away(
+                    item, s, consider_runtime_isinstance=consider_runtime_isinstance
+                )
                 for item in p_t.relevant_items()
-                if (isinstance(get_proper_type(item), AnyType) or not covers_at_runtime(item, s))
             ]
-        return UnionType.make_union(new_items)
+        return UnionType.make_union(
+            [item for item in new_items if not isinstance(get_proper_type(item), UninhabitedType)]
+        )
     elif isinstance(p_t, TypeVarType):
         return p_t.copy_modified(upper_bound=restrict_subtype_away(p_t.upper_bound, s))
-    elif covers_at_runtime(t, s):
-        return UninhabitedType()
+
+    if consider_runtime_isinstance:
+        if covers_at_runtime(t, s):
+            return UninhabitedType()
+        else:
+            return t
     else:
+        if is_proper_subtype(t, s, ignore_promotions=True):
+            return UninhabitedType()
+        if is_proper_subtype(t, s, ignore_promotions=True, erase_instances=True):
+            return UninhabitedType()
         return t
 
 
@@ -2096,7 +2128,8 @@ def covers_at_runtime(item: Type, supertype: Type) -> bool:
     supertype = get_proper_type(supertype)
 
     # Since runtime type checks will ignore type arguments, erase the types.
-    supertype = erase_type(supertype)
+    if not (isinstance(supertype, FunctionLike) and supertype.is_type_obj()):
+        supertype = erase_type(supertype)
     if is_proper_subtype(
         erase_type(item), supertype, ignore_promotions=True, erase_instances=True
     ):
diff --git a/mypy/suggestions.py b/mypy/suggestions.py
index a662dd7b98e9..45aa5ade47a4 100644
--- a/mypy/suggestions.py
+++ b/mypy/suggestions.py
@@ -27,6 +27,7 @@
 import itertools
 import json
 import os
+import sys
 from collections.abc import Iterator
 from contextlib import contextmanager
 from typing import Callable, NamedTuple, TypedDict, TypeVar, cast
@@ -229,6 +230,18 @@ def is_implicit_any(typ: Type) -> bool:
     return isinstance(typ, AnyType) and not is_explicit_any(typ)
 
 
+def _arg_accepts_function(typ: ProperType) -> bool:
+    return (
+        # TypeVar / Callable
+        isinstance(typ, (TypeVarType, CallableType))
+        or
+        # Protocol with __call__
+        isinstance(typ, Instance)
+        and typ.type.is_protocol
+        and typ.type.get_method("__call__") is not None
+    )
+
+
 class SuggestionEngine:
     """Engine for finding call sites and suggesting signatures."""
 
@@ -474,7 +487,7 @@ def get_suggestion(self, mod: str, node: FuncDef) -> PyAnnotateSignature:
         if self.no_errors and orig_errors:
             raise SuggestionFailure("Function does not typecheck.")
 
-        is_method = bool(node.info) and not node.is_static
+        is_method = bool(node.info) and node.has_self_or_cls_argument
 
         with state.strict_optional_set(graph[mod].options.strict_optional):
             guesses = self.get_guesses(
@@ -537,12 +550,17 @@ def find_node(self, key: str) -> tuple[str, str, FuncDef]:
         # TODO: Also return OverloadedFuncDef -- currently these are ignored.
         node: SymbolNode | None = None
         if ":" in key:
-            if key.count(":") > 1:
+            # A colon might be part of a drive name on Windows (like `C:/foo/bar`)
+            # and is also used as a delimiter between file path and lineno.
+            # If a colon is there for any of those reasons, it must be a file+line
+            # reference.
+            platform_key_count = 2 if sys.platform == "win32" else 1
+            if key.count(":") > platform_key_count:
                 raise SuggestionFailure(
                     "Malformed location for function: {}. Must be either"
                     " package.module.Class.method or path/to/file.py:line".format(key)
                 )
-            file, line = key.split(":")
+            file, line = key.rsplit(":", 1)
             if not line.isdigit():
                 raise SuggestionFailure(f"Line number must be a number. Got {line}")
             line_number = int(line)
@@ -658,7 +676,7 @@ def extract_from_decorator(self, node: Decorator) -> FuncDef | None:
             for ct in typ.items:
                 if not (
                     len(ct.arg_types) == 1
-                    and isinstance(ct.arg_types[0], TypeVarType)
+                    and _arg_accepts_function(get_proper_type(ct.arg_types[0]))
                     and ct.arg_types[0] == ct.ret_type
                 ):
                     return None
@@ -840,7 +858,7 @@ def visit_instance(self, t: Instance) -> str:
         if self.module:
             parts = obj.split(".")  # need to split the object part if it is a nested class
             tree = self.graph[self.module].tree
-            if tree and parts[0] in tree.names:
+            if tree and parts[0] in tree.names and mod not in tree.names:
                 mod = self.module
 
         if (mod, obj) == ("builtins", "tuple"):
diff --git a/mypy/test/testcheck.py b/mypy/test/testcheck.py
index fb2eb3a75b9b..04ef5370d381 100644
--- a/mypy/test/testcheck.py
+++ b/mypy/test/testcheck.py
@@ -5,6 +5,8 @@
 import os
 import re
 import sys
+import tempfile
+from pathlib import Path
 
 from mypy import build
 from mypy.build import Graph
@@ -45,16 +47,19 @@
     typecheck_files.remove("check-python312.test")
 if sys.version_info < (3, 13):
     typecheck_files.remove("check-python313.test")
-
-# Special tests for platforms with case-insensitive filesystems.
-if sys.platform not in ("darwin", "win32"):
-    typecheck_files.remove("check-modules-case.test")
+if sys.version_info < (3, 14):
+    typecheck_files.remove("check-python314.test")
 
 
 class TypeCheckSuite(DataSuite):
     files = typecheck_files
 
     def run_case(self, testcase: DataDrivenTestCase) -> None:
+        if os.path.basename(testcase.file) == "check-modules-case.test":
+            with tempfile.NamedTemporaryFile(prefix="test", dir=".") as temp_file:
+                temp_path = Path(temp_file.name)
+                if not temp_path.with_name(temp_path.name.upper()).exists():
+                    pytest.skip("File system is not case‐insensitive")
         if lxml is None and os.path.basename(testcase.file) == "check-reports.test":
             pytest.skip("Cannot import lxml. Is it installed?")
         incremental = (
diff --git a/mypy/test/testfscache.py b/mypy/test/testfscache.py
index 44b0d32f5797..529402dade96 100644
--- a/mypy/test/testfscache.py
+++ b/mypy/test/testfscache.py
@@ -4,7 +4,6 @@
 
 import os
 import shutil
-import sys
 import tempfile
 import unittest
 
@@ -83,7 +82,7 @@ def test_isfile_case_other_directory(self) -> None:
             assert self.isfile_case(os.path.join(other, "other_dir.py"))
             assert not self.isfile_case(os.path.join(other, "Other_Dir.py"))
             assert not self.isfile_case(os.path.join(other, "bar.py"))
-            if sys.platform in ("win32", "darwin"):
+            if os.path.exists(os.path.join(other, "PKG/other_dir.py")):
                 # We only check case for directories under our prefix, and since
                 # this path is not under the prefix, case difference is fine.
                 assert self.isfile_case(os.path.join(other, "PKG/other_dir.py"))
diff --git a/mypy/test/testparse.py b/mypy/test/testparse.py
index 027ca4dd2887..c8bcb5c0d807 100644
--- a/mypy/test/testparse.py
+++ b/mypy/test/testparse.py
@@ -27,6 +27,8 @@ class ParserSuite(DataSuite):
         files.remove("parse-python312.test")
     if sys.version_info < (3, 13):
         files.remove("parse-python313.test")
+    if sys.version_info < (3, 14):
+        files.remove("parse-python314.test")
 
     def run_case(self, testcase: DataDrivenTestCase) -> None:
         test_parser(testcase)
@@ -46,6 +48,8 @@ def test_parser(testcase: DataDrivenTestCase) -> None:
         options.python_version = (3, 12)
     elif testcase.file.endswith("python313.test"):
         options.python_version = (3, 13)
+    elif testcase.file.endswith("python314.test"):
+        options.python_version = (3, 14)
     else:
         options.python_version = defaults.PYTHON3_VERSION
 
diff --git a/mypy/test/testsolve.py b/mypy/test/testsolve.py
index 6566b03ef5e9..d60b2cb3fcc5 100644
--- a/mypy/test/testsolve.py
+++ b/mypy/test/testsolve.py
@@ -64,12 +64,14 @@ def test_multiple_variables(self) -> None:
         )
 
     def test_no_constraints_for_var(self) -> None:
-        self.assert_solve([self.fx.t], [], [self.fx.uninhabited])
-        self.assert_solve([self.fx.t, self.fx.s], [], [self.fx.uninhabited, self.fx.uninhabited])
+        self.assert_solve([self.fx.t], [], [self.fx.a_uninhabited])
+        self.assert_solve(
+            [self.fx.t, self.fx.s], [], [self.fx.a_uninhabited, self.fx.a_uninhabited]
+        )
         self.assert_solve(
             [self.fx.t, self.fx.s],
             [self.supc(self.fx.s, self.fx.a)],
-            [self.fx.uninhabited, self.fx.a],
+            [self.fx.a_uninhabited, self.fx.a],
         )
 
     def test_simple_constraints_with_dynamic_type(self) -> None:
@@ -116,7 +118,7 @@ def test_poly_no_constraints(self) -> None:
         self.assert_solve(
             [self.fx.t, self.fx.u],
             [],
-            [self.fx.uninhabited, self.fx.uninhabited],
+            [self.fx.a_uninhabited, self.fx.a_uninhabited],
             allow_polymorphic=True,
         )
 
@@ -152,7 +154,7 @@ def test_poly_free_pair_with_bounds_uninhabited(self) -> None:
         self.assert_solve(
             [self.fx.ub, self.fx.uc],
             [self.subc(self.fx.ub, self.fx.uc)],
-            [self.fx.uninhabited, self.fx.uninhabited],
+            [self.fx.a_uninhabited, self.fx.a_uninhabited],
             [],
             allow_polymorphic=True,
         )
diff --git a/mypy/test/teststubinfo.py b/mypy/test/teststubinfo.py
index e90c72335bf8..ae34e78f98c6 100644
--- a/mypy/test/teststubinfo.py
+++ b/mypy/test/teststubinfo.py
@@ -20,7 +20,8 @@ def test_is_legacy_bundled_packages(self) -> None:
     def test_stub_distribution_name(self) -> None:
         assert stub_distribution_name("foobar_asdf") is None
         assert stub_distribution_name("pycurl") == "types-pycurl"
-        assert stub_distribution_name("bs4") == "types-beautifulsoup4"
+        assert stub_distribution_name("psutil") == "types-psutil"
+        assert stub_distribution_name("sassutils") == "types-libsass"
         assert stub_distribution_name("google.cloud.ndb") == "types-google-cloud-ndb"
         assert stub_distribution_name("google.cloud.ndb.submodule") == "types-google-cloud-ndb"
         assert stub_distribution_name("google.cloud.unknown") is None
diff --git a/mypy/test/teststubtest.py b/mypy/test/teststubtest.py
index 7925f2a6bd3e..28263e20099d 100644
--- a/mypy/test/teststubtest.py
+++ b/mypy/test/teststubtest.py
@@ -13,7 +13,11 @@
 from typing import Any, Callable
 
 import mypy.stubtest
+from mypy import build, nodes
+from mypy.modulefinder import BuildSource
+from mypy.options import Options
 from mypy.stubtest import parse_options, test_stubs
+from mypy.test.config import test_temp_dir
 from mypy.test.data import root_dir
 
 
@@ -158,6 +162,14 @@ def __invert__(self: _T) -> _T: pass
 """
 
 
+def build_helper(source: str) -> build.BuildResult:
+    return build.build(
+        sources=[BuildSource("main.pyi", None, textwrap.dedent(source))],
+        options=Options(),
+        alt_lib_path=test_temp_dir,
+    )
+
+
 def run_stubtest_with_stderr(
     stub: str, runtime: str, options: list[str], config_file: str | None = None
 ) -> tuple[str, str]:
@@ -842,6 +854,18 @@ def f2(self, *a) -> int: ...
             """,
             error=None,
         )
+        yield Case(
+            stub="""
+            @overload
+            def f(a: int) -> int: ...
+            @overload
+            def f(a: int, b: str, /) -> str: ...
+            """,
+            runtime="""
+            def f(a, *args): ...
+            """,
+            error=None,
+        )
 
     @collect_cases
     def test_property(self) -> Iterator[Case]:
@@ -850,11 +874,13 @@ def test_property(self) -> Iterator[Case]:
             class Good:
                 @property
                 def read_only_attr(self) -> int: ...
+                read_only_attr_alias = read_only_attr
             """,
             runtime="""
             class Good:
                 @property
                 def read_only_attr(self): return 1
+                read_only_attr_alias = read_only_attr
             """,
             error=None,
         )
@@ -916,6 +942,7 @@ class Z:
                 def read_write_attr(self) -> int: ...
                 @read_write_attr.setter
                 def read_write_attr(self, val: int) -> None: ...
+                read_write_attr_alias = read_write_attr
             """,
             runtime="""
             class Z:
@@ -923,6 +950,7 @@ class Z:
                 def read_write_attr(self): return self._val
                 @read_write_attr.setter
                 def read_write_attr(self, val): self._val = val
+                read_write_attr_alias = read_write_attr
             """,
             error=None,
         )
@@ -1401,9 +1429,11 @@ def spam(x=Flags4(0)): pass
         )
         yield Case(
             stub="""
+            import sys
             from typing import Final, Literal
             class BytesEnum(bytes, enum.Enum):
                 a = b'foo'
+
             FOO: Literal[BytesEnum.a]
             BAR: Final = BytesEnum.a
             BAZ: BytesEnum
@@ -1419,6 +1449,31 @@ class BytesEnum(bytes, enum.Enum):
             """,
             error=None,
         )
+        yield Case(
+            stub="""
+            class HasSlotsAndNothingElse:
+                __slots__ = ("x",)
+                x: int
+
+            class HasInheritedSlots(HasSlotsAndNothingElse):
+                pass
+
+            class HasEmptySlots:
+                __slots__ = ()
+            """,
+            runtime="""
+            class HasSlotsAndNothingElse:
+                __slots__ = ("x",)
+                x: int
+
+            class HasInheritedSlots(HasSlotsAndNothingElse):
+                pass
+
+            class HasEmptySlots:
+                __slots__ = ()
+            """,
+            error=None,
+        )
 
     @collect_cases
     def test_decorator(self) -> Iterator[Case]:
@@ -1609,6 +1664,107 @@ def test_not_subclassable(self) -> Iterator[Case]:
             error="CannotBeSubclassed",
         )
 
+    @collect_cases
+    def test_disjoint_base(self) -> Iterator[Case]:
+        yield Case(
+            stub="""
+            class A: pass
+            """,
+            runtime="""
+            class A: pass
+            """,
+            error=None,
+        )
+        yield Case(
+            stub="""
+            from typing_extensions import disjoint_base
+
+            @disjoint_base
+            class B: pass
+            """,
+            runtime="""
+            class B: pass
+            """,
+            error="test_module.B",
+        )
+        yield Case(
+            stub="""
+            from typing_extensions import Self
+
+            class mytakewhile:
+                def __new__(cls, predicate: object, iterable: object, /) -> Self: ...
+                def __iter__(self) -> Self: ...
+                def __next__(self) -> object: ...
+            """,
+            runtime="""
+            from itertools import takewhile as mytakewhile
+            """,
+            # Should have @disjoint_base
+            error="test_module.mytakewhile",
+        )
+        yield Case(
+            stub="""
+            from typing_extensions import disjoint_base, Self
+
+            @disjoint_base
+            class mycorrecttakewhile:
+                def __new__(cls, predicate: object, iterable: object, /) -> Self: ...
+                def __iter__(self) -> Self: ...
+                def __next__(self) -> object: ...
+            """,
+            runtime="""
+            from itertools import takewhile as mycorrecttakewhile
+            """,
+            error=None,
+        )
+        yield Case(
+            runtime="""
+            class IsDisjointBaseBecauseItHasSlots:
+                __slots__ = ("a",)
+                a: int
+            """,
+            stub="""
+            from typing_extensions import disjoint_base
+
+            @disjoint_base
+            class IsDisjointBaseBecauseItHasSlots:
+                a: int
+            """,
+            error="test_module.IsDisjointBaseBecauseItHasSlots",
+        )
+        yield Case(
+            runtime="""
+            class IsFinalSoDisjointBaseIsRedundant: ...
+            """,
+            stub="""
+            from typing_extensions import disjoint_base, final
+
+            @final
+            @disjoint_base
+            class IsFinalSoDisjointBaseIsRedundant: ...
+            """,
+            error="test_module.IsFinalSoDisjointBaseIsRedundant",
+        )
+        yield Case(
+            runtime="""
+            import enum
+
+            class IsEnumWithMembersSoDisjointBaseIsRedundant(enum.Enum):
+                A = 1
+                B = 2
+            """,
+            stub="""
+            from typing_extensions import disjoint_base
+            import enum
+
+            @disjoint_base
+            class IsEnumWithMembersSoDisjointBaseIsRedundant(enum.Enum):
+                A = 1
+                B = 2
+            """,
+            error="test_module.IsEnumWithMembersSoDisjointBaseIsRedundant",
+        )
+
     @collect_cases
     def test_has_runtime_final_decorator(self) -> Iterator[Case]:
         yield Case(
@@ -2468,6 +2624,42 @@ def func2() -> None: ...
             runtime="def func2() -> None: ...",
             error="func2",
         )
+        # A type that exists at runtime is allowed to alias a type marked
+        # as '@type_check_only' in the stubs.
+        yield Case(
+            stub="""
+            @type_check_only
+            class _X1: ...
+            X2 = _X1
+            """,
+            runtime="class X2: ...",
+            error=None,
+        )
+
+    @collect_cases
+    def test_type_default_protocol(self) -> Iterator[Case]:
+        yield Case(
+            stub="""
+            from typing import Protocol
+
+            class _FormatterClass(Protocol):
+                def __call__(self, *, prog: str) -> HelpFormatter: ...
+
+            class ArgumentParser:
+                def __init__(self, formatter_class: _FormatterClass = ...) -> None: ...
+
+            class HelpFormatter:
+                def __init__(self, prog: str, indent_increment: int = 2) -> None: ...
+            """,
+            runtime="""
+            class HelpFormatter:
+                def __init__(self, prog, indent_increment=2) -> None: ...
+
+            class ArgumentParser:
+                def __init__(self, formatter_class=HelpFormatter): ...
+            """,
+            error=None,
+        )
 
 
 def remove_color_code(s: str) -> str:
@@ -2482,8 +2674,8 @@ def test_output(self) -> None:
             options=[],
         )
         expected = (
-            f'error: {TEST_MODULE_NAME}.bad is inconsistent, stub argument "number" differs '
-            'from runtime argument "num"\n'
+            f'error: {TEST_MODULE_NAME}.bad is inconsistent, stub parameter "number" differs '
+            'from runtime parameter "num"\n'
             f"Stub: in file {TEST_MODULE_NAME}.pyi:1\n"
             "def (number: builtins.int, text: builtins.str)\n"
             f"Runtime: in file {TEST_MODULE_NAME}.py:1\ndef (num, text)\n\n"
@@ -2498,7 +2690,9 @@ def test_output(self) -> None:
         )
         expected = (
             "{}.bad is inconsistent, "
-            'stub argument "number" differs from runtime argument "num"\n'.format(TEST_MODULE_NAME)
+            'stub parameter "number" differs from runtime parameter "num"\n'.format(
+                TEST_MODULE_NAME
+            )
         )
         assert output == expected
 
@@ -2645,6 +2839,25 @@ def test_builtin_signature_with_unrepresentable_default(self) -> None:
             == "def (self, sep = ..., bytes_per_sep = ...)"
         )
 
+    def test_overload_signature(self) -> None:
+        # The same argument as both positional-only and pos-or-kw in
+        # different overloads previously produced incorrect signatures
+        source = """
+        from typing import overload
+        @overload
+        def myfunction(arg: int) -> None: ...
+        @overload
+        def myfunction(arg: str, /) -> None: ...
+        """
+        result = build_helper(source)
+        stub = result.files["__main__"].names["myfunction"].node
+        assert isinstance(stub, nodes.OverloadedFuncDef)
+        sig = mypy.stubtest.Signature.from_overloadedfuncdef(stub)
+        if sys.version_info >= (3, 10):
+            assert str(sig) == "def (arg: builtins.int | builtins.str)"
+        else:
+            assert str(sig) == "def (arg: Union[builtins.int, builtins.str])"
+
     def test_config_file(self) -> None:
         runtime = "temp = 5\n"
         stub = "from decimal import Decimal\ntemp: Decimal\n"
diff --git a/mypy/test/typefixture.py b/mypy/test/typefixture.py
index d6c904732b17..0defcdaebc99 100644
--- a/mypy/test/typefixture.py
+++ b/mypy/test/typefixture.py
@@ -78,6 +78,8 @@ def make_type_var(
         self.anyt = AnyType(TypeOfAny.special_form)
         self.nonet = NoneType()
         self.uninhabited = UninhabitedType()
+        self.a_uninhabited = UninhabitedType()
+        self.a_uninhabited.ambiguous = True
 
         # Abstract class TypeInfos
 
diff --git a/mypy/type_visitor.py b/mypy/type_visitor.py
index ab1ec8b46fdd..65051ddbab67 100644
--- a/mypy/type_visitor.py
+++ b/mypy/type_visitor.py
@@ -228,7 +228,7 @@ def visit_instance(self, t: Instance, /) -> Type:
             last_known_value = raw_last_known_value
         return Instance(
             typ=t.type,
-            args=self.translate_types(t.args),
+            args=self.translate_type_tuple(t.args),
             line=t.line,
             column=t.column,
             last_known_value=last_known_value,
@@ -242,7 +242,7 @@ def visit_param_spec(self, t: ParamSpecType, /) -> Type:
         return t
 
     def visit_parameters(self, t: Parameters, /) -> Type:
-        return t.copy_modified(arg_types=self.translate_types(t.arg_types))
+        return t.copy_modified(arg_types=self.translate_type_list(t.arg_types))
 
     def visit_type_var_tuple(self, t: TypeVarTupleType, /) -> Type:
         return t
@@ -255,14 +255,14 @@ def visit_unpack_type(self, t: UnpackType, /) -> Type:
 
     def visit_callable_type(self, t: CallableType, /) -> Type:
         return t.copy_modified(
-            arg_types=self.translate_types(t.arg_types),
+            arg_types=self.translate_type_list(t.arg_types),
             ret_type=t.ret_type.accept(self),
             variables=self.translate_variables(t.variables),
         )
 
     def visit_tuple_type(self, t: TupleType, /) -> Type:
         return TupleType(
-            self.translate_types(t.items),
+            self.translate_type_list(t.items),
             # TODO: This appears to be unsafe.
             cast(Any, t.partial_fallback.accept(self)),
             t.line,
@@ -299,7 +299,7 @@ def visit_union_type(self, t: UnionType, /) -> Type:
             return cached
 
         result = UnionType(
-            self.translate_types(t.items),
+            self.translate_type_list(t.items),
             t.line,
             t.column,
             uses_pep604_syntax=t.uses_pep604_syntax,
@@ -308,9 +308,12 @@ def visit_union_type(self, t: UnionType, /) -> Type:
             self.set_cached(t, result)
         return result
 
-    def translate_types(self, types: Iterable[Type]) -> list[Type]:
+    def translate_type_list(self, types: list[Type]) -> list[Type]:
         return [t.accept(self) for t in types]
 
+    def translate_type_tuple(self, types: tuple[Type, ...]) -> tuple[Type, ...]:
+        return tuple(t.accept(self) for t in types)
+
     def translate_variables(
         self, variables: Sequence[TypeVarLikeType]
     ) -> Sequence[TypeVarLikeType]:
diff --git a/mypy/typeanal.py b/mypy/typeanal.py
index eeb5d3c52ac6..af70c52180aa 100644
--- a/mypy/typeanal.py
+++ b/mypy/typeanal.py
@@ -1109,8 +1109,8 @@ def visit_callable_type(
                 variables = t.variables
             else:
                 variables, _ = self.bind_function_type_variables(t, t)
-            type_guard = self.anal_type_guard(t.ret_type)
-            type_is = self.anal_type_is(t.ret_type)
+            type_guard = self.anal_type_guard(t.ret_type) if t.type_guard is None else t.type_guard
+            type_is = self.anal_type_is(t.ret_type) if t.type_is is None else t.type_is
 
             arg_kinds = t.arg_kinds
             arg_types = []
@@ -1820,7 +1820,7 @@ def infer_type_variables(
 
     def bind_function_type_variables(
         self, fun_type: CallableType, defn: Context
-    ) -> tuple[Sequence[TypeVarLikeType], bool]:
+    ) -> tuple[tuple[TypeVarLikeType, ...], bool]:
         """Find the type variables of the function type and bind them in our tvar_scope"""
         has_self_type = False
         if fun_type.variables:
@@ -1835,7 +1835,7 @@ def bind_function_type_variables(
                 assert isinstance(var_expr, TypeVarLikeExpr)
                 binding = self.tvar_scope.bind_new(var.name, var_expr)
                 defs.append(binding)
-            return defs, has_self_type
+            return tuple(defs), has_self_type
         typevars, has_self_type = self.infer_type_variables(fun_type)
         # Do not define a new type variable if already defined in scope.
         typevars = [
@@ -1844,15 +1844,12 @@ def bind_function_type_variables(
         defs = []
         for name, tvar in typevars:
             if not self.tvar_scope.allow_binding(tvar.fullname):
-                self.fail(
-                    f'Type variable "{name}" is bound by an outer class',
-                    defn,
-                    code=codes.VALID_TYPE,
-                )
+                err_msg = message_registry.TYPE_VAR_REDECLARED_IN_NESTED_CLASS.format(name)
+                self.fail(err_msg.value, defn, code=err_msg.code)
             binding = self.tvar_scope.bind_new(name, tvar)
             defs.append(binding)
 
-        return defs, has_self_type
+        return tuple(defs), has_self_type
 
     def is_defined_type_var(self, tvar: str, context: Context) -> bool:
         tvar_node = self.lookup_qualified(tvar, context)
@@ -1981,7 +1978,7 @@ def check_unpacks_in_list(self, items: list[Type]) -> list[Type]:
 
         if num_unpacks > 1:
             assert final_unpack is not None
-            self.fail("More than one Unpack in a type is not allowed", final_unpack.type)
+            self.fail("More than one variadic Unpack in a type is not allowed", final_unpack.type)
         return new_items
 
     def tuple_type(self, items: list[Type], line: int, column: int) -> TupleType:
diff --git a/mypy/typeops.py b/mypy/typeops.py
index e8087a1713ff..87a4d8cefd13 100644
--- a/mypy/typeops.py
+++ b/mypy/typeops.py
@@ -11,11 +11,11 @@
 from collections.abc import Iterable, Sequence
 from typing import Any, Callable, TypeVar, cast
 
+from mypy.checker_state import checker_state
 from mypy.copytype import copy_type
 from mypy.expandtype import expand_type, expand_type_by_instance
 from mypy.maptype import map_instance_to_supertype
 from mypy.nodes import (
-    ARG_OPT,
     ARG_POS,
     ARG_STAR,
     ARG_STAR2,
@@ -63,6 +63,7 @@
     flatten_nested_unions,
     get_proper_type,
     get_proper_types,
+    remove_dups,
 )
 from mypy.typetraverser import TypeTraverserVisitor
 from mypy.typevars import fill_typevars
@@ -125,7 +126,8 @@ def tuple_fallback(typ: TupleType) -> Instance:
     )
 
 
-def get_self_type(func: CallableType, default_self: Instance | TupleType) -> Type | None:
+def get_self_type(func: CallableType, def_info: TypeInfo) -> Type | None:
+    default_self = fill_typevars(def_info)
     if isinstance(get_proper_type(func.ret_type), UninhabitedType):
         return func.ret_type
     elif func.arg_types and func.arg_types[0] != default_self and func.arg_kinds[0] == ARG_POS:
@@ -144,6 +146,15 @@ def type_object_type(info: TypeInfo, named_type: Callable[[str], Instance]) -> P
     where ... are argument types for the __init__/__new__ method (without the self
     argument). Also, the fallback type will be 'type' instead of 'function'.
     """
+    allow_cache = (
+        checker_state.type_checker is not None
+        and checker_state.type_checker.allow_constructor_cache
+    )
+
+    if info.type_object_type is not None:
+        if allow_cache:
+            return info.type_object_type
+        info.type_object_type = None
 
     # We take the type from whichever of __init__ and __new__ is first
     # in the MRO, preferring __init__ if there is a tie.
@@ -166,7 +177,15 @@ def type_object_type(info: TypeInfo, named_type: Callable[[str], Instance]) -> P
     init_index = info.mro.index(init_method.node.info)
     new_index = info.mro.index(new_method.node.info)
 
-    fallback = info.metaclass_type or named_type("builtins.type")
+    if info.metaclass_type is not None:
+        fallback = info.metaclass_type
+    elif checker_state.type_checker:
+        # Prefer direct call when it is available. It is faster, and,
+        # unfortunately, some callers provide bogus callback.
+        fallback = checker_state.type_checker.named_type("builtins.type")
+    else:
+        fallback = named_type("builtins.type")
+
     if init_index < new_index:
         method: FuncBase | Decorator = init_method.node
         is_new = False
@@ -188,7 +207,10 @@ def type_object_type(info: TypeInfo, named_type: Callable[[str], Instance]) -> P
                     is_bound=True,
                     fallback=named_type("builtins.function"),
                 )
-                return class_callable(sig, info, fallback, None, is_new=False)
+                result: FunctionLike = class_callable(sig, info, fallback, None, is_new=False)
+                if allow_cache and state.strict_optional:
+                    info.type_object_type = result
+                return result
 
         # Otherwise prefer __init__ in a tie. It isn't clear that this
         # is the right thing, but __new__ caused problems with
@@ -198,12 +220,21 @@ def type_object_type(info: TypeInfo, named_type: Callable[[str], Instance]) -> P
     # Construct callable type based on signature of __init__. Adjust
     # return type and insert type arguments.
     if isinstance(method, FuncBase):
+        if isinstance(method, OverloadedFuncDef) and not method.type:
+            # Do not cache if the type is not ready. Same logic for decorators is
+            # achieved in early return above because is_valid_constructor() is False.
+            allow_cache = False
         t = function_type(method, fallback)
     else:
         assert isinstance(method.type, ProperType)
         assert isinstance(method.type, FunctionLike)  # is_valid_constructor() ensures this
         t = method.type
-    return type_object_type_from_function(t, info, method.info, fallback, is_new)
+    result = type_object_type_from_function(t, info, method.info, fallback, is_new)
+    # Only write cached result is strict_optional=True, otherwise we may get
+    # inconsistent behaviour because of union simplification.
+    if allow_cache and state.strict_optional:
+        info.type_object_type = result
+    return result
 
 
 def is_valid_constructor(n: SymbolNode | None) -> bool:
@@ -227,9 +258,8 @@ def type_object_type_from_function(
     # self-types only in the defining class, similar to __new__ (but not exactly the same,
     # see comment in class_callable below). This is mostly useful for annotating library
     # classes such as subprocess.Popen.
-    default_self = fill_typevars(info)
     if not is_new and not info.is_newtype:
-        orig_self_types = [get_self_type(it, default_self) for it in signature.items]
+        orig_self_types = [get_self_type(it, def_info) for it in signature.items]
     else:
         orig_self_types = [None] * len(signature.items)
 
@@ -245,7 +275,7 @@ def type_object_type_from_function(
     # We need to map B's __init__ to the type (List[T]) -> None.
     signature = bind_self(
         signature,
-        original_type=default_self,
+        original_type=fill_typevars(info),
         is_classmethod=is_new,
         # Explicit instance self annotations have special handling in class_callable(),
         # we don't need to bind any type variables in them if they are generic.
@@ -393,27 +423,9 @@ class B(A): pass
 
     """
     if isinstance(method, Overloaded):
-        items = []
-        original_type = get_proper_type(original_type)
-        for c in method.items:
-            if isinstance(original_type, Instance):
-                # Filter based on whether declared self type can match actual object type.
-                # For example, if self has type C[int] and method is accessed on a C[str] value,
-                # omit this item. This is best effort since bind_self can be called in many
-                # contexts, and doing complete validation might trigger infinite recursion.
-                #
-                # Note that overload item filtering normally happens elsewhere. This is needed
-                # at least during constraint inference.
-                keep = is_valid_self_type_best_effort(c, original_type)
-            else:
-                keep = True
-            if keep:
-                items.append(bind_self(c, original_type, is_classmethod, ignore_instances))
-        if len(items) == 0:
-            # If no item matches, returning all items helps avoid some spurious errors
-            items = [
-                bind_self(c, original_type, is_classmethod, ignore_instances) for c in method.items
-            ]
+        items = [
+            bind_self(c, original_type, is_classmethod, ignore_instances) for c in method.items
+        ]
         return cast(F, Overloaded(items))
     assert isinstance(method, CallableType)
     func: CallableType = method
@@ -472,9 +484,6 @@ class B(A): pass
     else:
         variables = func.variables
 
-    original_type = get_proper_type(original_type)
-    if isinstance(original_type, CallableType) and original_type.is_type_obj():
-        original_type = TypeType.make_normalized(original_type.ret_type)
     res = func.copy_modified(
         arg_types=func.arg_types[1:],
         arg_kinds=func.arg_kinds[1:],
@@ -485,43 +494,6 @@ class B(A): pass
     return cast(F, res)
 
 
-def is_valid_self_type_best_effort(c: CallableType, self_type: Instance) -> bool:
-    """Quickly check if self_type might match the self in a callable.
-
-    Avoid performing any complex type operations. This is performance-critical.
-
-    Default to returning True if we don't know (or it would be too expensive).
-    """
-    if (
-        self_type.args
-        and c.arg_types
-        and isinstance((arg_type := get_proper_type(c.arg_types[0])), Instance)
-        and c.arg_kinds[0] in (ARG_POS, ARG_OPT)
-        and arg_type.args
-        and self_type.type.fullname != "functools._SingleDispatchCallable"
-    ):
-        if self_type.type is not arg_type.type:
-            # We can't map to supertype, since it could trigger expensive checks for
-            # protocol types, so we consevatively assume this is fine.
-            return True
-
-        # Fast path: no explicit annotation on self
-        if all(
-            (
-                type(arg) is TypeVarType
-                and type(arg.upper_bound) is Instance
-                and arg.upper_bound.type.fullname == "builtins.object"
-            )
-            for arg in arg_type.args
-        ):
-            return True
-
-        from mypy.meet import is_overlapping_types
-
-        return is_overlapping_types(self_type, c.arg_types[0])
-    return True
-
-
 def erase_to_bound(t: Type) -> Type:
     # TODO: use value restrictions to produce a union?
     t = get_proper_type(t)
@@ -551,15 +523,16 @@ def callable_corresponding_argument(
 
         # def right(a: int = ...) -> None: ...
         # def left(__a: int = ..., *, a: int = ...) -> None: ...
-        from mypy.subtypes import is_equivalent
+        from mypy.meet import meet_types
 
         if (
             not (by_name.required or by_pos.required)
             and by_pos.name is None
             and by_name.pos is None
-            and is_equivalent(by_name.typ, by_pos.typ)
         ):
-            return FormalArgument(by_name.name, by_pos.pos, by_name.typ, False)
+            return FormalArgument(
+                by_name.name, by_pos.pos, meet_types(by_name.typ, by_pos.typ), False
+            )
     return by_name if by_name is not None else by_pos
 
 
@@ -868,8 +841,8 @@ def function_type(func: FuncBase, fallback: Instance) -> FunctionLike:
         if isinstance(func, FuncItem):
             return callable_type(func, fallback)
         else:
-            # Broken overloads can have self.type set to None.
-            # TODO: should we instead always set the type in semantic analyzer?
+            # Either a broken overload, or decorated overload type is not ready.
+            # TODO: make sure the caller defers if possible.
             assert isinstance(func, OverloadedFuncDef)
             any_type = AnyType(TypeOfAny.from_error)
             dummy = CallableType(
@@ -890,7 +863,7 @@ def callable_type(
     fdef: FuncItem, fallback: Instance, ret_type: Type | None = None
 ) -> CallableType:
     # TODO: somewhat unfortunate duplication with prepare_method_signature in semanal
-    if fdef.info and (not fdef.is_static or fdef.name == "__new__") and fdef.arg_names:
+    if fdef.info and fdef.has_self_or_cls_argument and fdef.arg_names:
         self_type: Type = fill_typevars(fdef.info)
         if fdef.is_class or fdef.name == "__new__":
             self_type = TypeType.make_normalized(self_type)
@@ -1026,7 +999,7 @@ def is_singleton_type(typ: Type) -> bool:
     return typ.is_singleton_type()
 
 
-def try_expanding_sum_type_to_union(typ: Type, target_fullname: str) -> ProperType:
+def try_expanding_sum_type_to_union(typ: Type, target_fullname: str) -> Type:
     """Attempts to recursively expand any enum Instances with the given target_fullname
     into a Union of all of its component LiteralTypes.
 
@@ -1048,21 +1021,22 @@ class Status(Enum):
     typ = get_proper_type(typ)
 
     if isinstance(typ, UnionType):
+        # Non-empty enums cannot subclass each other so simply removing duplicates is enough.
         items = [
-            try_expanding_sum_type_to_union(item, target_fullname) for item in typ.relevant_items()
+            try_expanding_sum_type_to_union(item, target_fullname)
+            for item in remove_dups(flatten_nested_unions(typ.relevant_items()))
         ]
-        return make_simplified_union(items, contract_literals=False)
+        return UnionType.make_union(items)
 
     if isinstance(typ, Instance) and typ.type.fullname == target_fullname:
         if typ.type.fullname == "builtins.bool":
-            items = [LiteralType(True, typ), LiteralType(False, typ)]
-            return make_simplified_union(items, contract_literals=False)
+            return UnionType([LiteralType(True, typ), LiteralType(False, typ)])
 
         if typ.type.is_enum:
             items = [LiteralType(name, typ) for name in typ.type.enum_members]
             if not items:
                 return typ
-            return make_simplified_union(items, contract_literals=False)
+            return UnionType.make_union(items)
 
     return typ
 
@@ -1257,6 +1231,8 @@ def get_protocol_member(
     if member == "__call__" and class_obj:
         # Special case: class objects always have __call__ that is just the constructor.
 
+        # TODO: this is wrong, it creates callables that are not recognized as type objects.
+        # Long-term, we should probably get rid of this callback argument altogether.
         def named_type(fullname: str) -> Instance:
             return Instance(left.type.mro[-1], [])
 
@@ -1279,3 +1255,54 @@ def named_type(fullname: str) -> Instance:
             )
         )
     return subtype
+
+
+def _is_disjoint_base(info: TypeInfo) -> bool:
+    # It either has the @disjoint_base decorator or defines nonempty __slots__.
+    if info.is_disjoint_base:
+        return True
+    if not info.slots:
+        return False
+    own_slots = {
+        slot
+        for slot in info.slots
+        if not any(
+            base_info.type.slots is not None and slot in base_info.type.slots
+            for base_info in info.bases
+        )
+    }
+    return bool(own_slots)
+
+
+def _get_disjoint_base_of(instance: Instance) -> TypeInfo | None:
+    """Returns the disjoint base of the given instance, if it exists."""
+    if _is_disjoint_base(instance.type):
+        return instance.type
+    for base in instance.type.mro:
+        if _is_disjoint_base(base):
+            return base
+    return None
+
+
+def can_have_shared_disjoint_base(instances: list[Instance]) -> bool:
+    """Returns whether the given instances can share a disjoint base.
+
+    This means that a child class of these classes can exist at runtime.
+    """
+    # Ignore None disjoint bases (which are `object`).
+    disjoint_bases = [
+        base for instance in instances if (base := _get_disjoint_base_of(instance)) is not None
+    ]
+    if not disjoint_bases:
+        # All are `object`.
+        return True
+
+    candidate = disjoint_bases[0]
+    for base in disjoint_bases[1:]:
+        if candidate.has_base(base.fullname):
+            continue
+        elif base.has_base(candidate.fullname):
+            candidate = base
+        else:
+            return False
+    return True
diff --git a/mypy/types.py b/mypy/types.py
index 8ecd2ccf52d9..c23997d069d4 100644
--- a/mypy/types.py
+++ b/mypy/types.py
@@ -5,32 +5,34 @@
 import sys
 from abc import abstractmethod
 from collections.abc import Iterable, Sequence
-from typing import (
-    TYPE_CHECKING,
-    Any,
-    ClassVar,
-    Final,
-    NamedTuple,
-    NewType,
-    TypeVar,
-    Union,
-    cast,
-    overload,
-)
+from typing import TYPE_CHECKING, Any, ClassVar, Final, NewType, TypeVar, Union, cast, overload
 from typing_extensions import Self, TypeAlias as _TypeAlias, TypeGuard
 
 import mypy.nodes
 from mypy.bogus_type import Bogus
-from mypy.nodes import (
-    ARG_POS,
-    ARG_STAR,
-    ARG_STAR2,
-    INVARIANT,
-    ArgKind,
-    FakeInfo,
-    FuncDef,
-    SymbolNode,
+from mypy.cache import (
+    Buffer,
+    Tag,
+    read_bool,
+    read_int,
+    read_int_list,
+    read_literal,
+    read_str,
+    read_str_list,
+    read_str_opt,
+    read_str_opt_list,
+    read_tag,
+    write_bool,
+    write_int,
+    write_int_list,
+    write_literal,
+    write_str,
+    write_str_list,
+    write_str_opt,
+    write_str_opt_list,
+    write_tag,
 )
+from mypy.nodes import ARG_KINDS, ARG_POS, ARG_STAR, ARG_STAR2, INVARIANT, ArgKind, SymbolNode
 from mypy.options import Options
 from mypy.state import state
 from mypy.util import IdMapper
@@ -139,9 +141,12 @@
 # Supported Unpack type names.
 UNPACK_TYPE_NAMES: Final = ("typing.Unpack", "typing_extensions.Unpack")
 
-# Supported @deprecated type names
+# Supported @deprecated decorator names
 DEPRECATED_TYPE_NAMES: Final = ("warnings.deprecated", "typing_extensions.deprecated")
 
+# Supported @disjoint_base decorator names
+DISJOINT_BASE_DECORATOR_NAMES: Final = ("typing.disjoint_base", "typing_extensions.disjoint_base")
+
 # We use this constant in various places when checking `tuple` subtyping:
 TUPLE_LIKE_INSTANCE_NAMES: Final = (
     "builtins.tuple",
@@ -181,6 +186,8 @@
 # Supported @override decorator names.
 OVERRIDE_DECORATOR_NAMES: Final = ("typing.override", "typing_extensions.override")
 
+ELLIPSIS_TYPE_NAMES: Final = ("builtins.ellipsis", "types.EllipsisType")
+
 # A placeholder used for Bogus[...] parameters
 _dummy: Final[Any] = object()
 
@@ -291,6 +298,13 @@ def serialize(self) -> JsonDict | str:
     def deserialize(cls, data: JsonDict) -> Type:
         raise NotImplementedError(f"Cannot deserialize {cls.__name__} instance")
 
+    def write(self, data: Buffer) -> None:
+        raise NotImplementedError(f"Cannot serialize {self.__class__.__name__} instance")
+
+    @classmethod
+    def read(cls, data: Buffer) -> Type:
+        raise NotImplementedError(f"Cannot deserialize {cls.__name__} instance")
+
     def is_singleton_type(self) -> bool:
         return False
 
@@ -353,11 +367,7 @@ def _expand_once(self) -> Type:
             ):
                 mapping[tvar.id] = sub
 
-        new_tp = self.alias.target.accept(InstantiateAliasVisitor(mapping))
-        new_tp.accept(LocationSetter(self.line, self.column))
-        new_tp.line = self.line
-        new_tp.column = self.column
-        return new_tp
+        return self.alias.target.accept(InstantiateAliasVisitor(mapping))
 
     def _partial_expansion(self, nothing_args: bool = False) -> tuple[ProperType, bool]:
         # Private method mostly for debugging and testing.
@@ -410,6 +420,11 @@ def can_be_false_default(self) -> bool:
             return self.alias.target.can_be_false
         return super().can_be_false_default()
 
+    def copy_modified(self, *, args: list[Type] | None = None) -> TypeAliasType:
+        return TypeAliasType(
+            self.alias, args if args is not None else self.args.copy(), self.line, self.column
+        )
+
     def accept(self, visitor: TypeVisitor[T]) -> T:
         return visitor.visit_type_alias_type(self)
 
@@ -443,10 +458,17 @@ def deserialize(cls, data: JsonDict) -> TypeAliasType:
         alias.type_ref = data["type_ref"]
         return alias
 
-    def copy_modified(self, *, args: list[Type] | None = None) -> TypeAliasType:
-        return TypeAliasType(
-            self.alias, args if args is not None else self.args.copy(), self.line, self.column
-        )
+    def write(self, data: Buffer) -> None:
+        write_tag(data, TYPE_ALIAS_TYPE)
+        write_type_list(data, self.args)
+        assert self.alias is not None
+        write_str(data, self.alias.fullname)
+
+    @classmethod
+    def read(cls, data: Buffer) -> TypeAliasType:
+        alias = TypeAliasType(None, read_type_list(data))
+        alias.type_ref = read_str(data)
+        return alias
 
 
 class TypeGuardedType(Type):
@@ -521,7 +543,7 @@ class TypeVarId:
     # function type variables.
 
     # Metavariables are allocated unique ids starting from 1.
-    raw_id: int
+    raw_id: Final[int]
 
     # Level of the variable in type inference. Currently either 0 for
     # declared types, or 1 for type inference metavariables.
@@ -549,6 +571,10 @@ def __repr__(self) -> str:
         return self.raw_id.__repr__()
 
     def __eq__(self, other: object) -> bool:
+        # Although this call is not expensive (like UnionType or TypedDictType),
+        # most of the time we get the same object here, so add a fast path.
+        if self is other:
+            return True
         return (
             isinstance(other, TypeVarId)
             and self.raw_id == other.raw_id
@@ -560,7 +586,7 @@ def __ne__(self, other: object) -> bool:
         return not (self == other)
 
     def __hash__(self) -> int:
-        return hash((self.raw_id, self.meta_level, self.namespace))
+        return self.raw_id ^ (self.meta_level << 8) ^ hash(self.namespace)
 
     def is_meta_var(self) -> bool:
         return self.meta_level > 0
@@ -711,6 +737,29 @@ def deserialize(cls, data: JsonDict) -> TypeVarType:
             variance=data["variance"],
         )
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, TYPE_VAR_TYPE)
+        write_str(data, self.name)
+        write_str(data, self.fullname)
+        write_int(data, self.id.raw_id)
+        write_str(data, self.id.namespace)
+        write_type_list(data, self.values)
+        self.upper_bound.write(data)
+        self.default.write(data)
+        write_int(data, self.variance)
+
+    @classmethod
+    def read(cls, data: Buffer) -> TypeVarType:
+        return TypeVarType(
+            read_str(data),
+            read_str(data),
+            TypeVarId(read_int(data), namespace=read_str(data)),
+            read_type_list(data),
+            read_type(data),
+            read_type(data),
+            read_int(data),
+        )
+
 
 class ParamSpecFlavor:
     # Simple ParamSpec reference such as "P"
@@ -840,6 +889,31 @@ def deserialize(cls, data: JsonDict) -> ParamSpecType:
             prefix=Parameters.deserialize(data["prefix"]),
         )
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, PARAM_SPEC_TYPE)
+        self.prefix.write(data)
+        write_str(data, self.name)
+        write_str(data, self.fullname)
+        write_int(data, self.id.raw_id)
+        write_str(data, self.id.namespace)
+        write_int(data, self.flavor)
+        self.upper_bound.write(data)
+        self.default.write(data)
+
+    @classmethod
+    def read(cls, data: Buffer) -> ParamSpecType:
+        assert read_tag(data) == PARAMETERS
+        prefix = Parameters.read(data)
+        return ParamSpecType(
+            read_str(data),
+            read_str(data),
+            TypeVarId(read_int(data), namespace=read_str(data)),
+            read_int(data),
+            read_type(data),
+            read_type(data),
+            prefix=prefix,
+        )
+
 
 class TypeVarTupleType(TypeVarLikeType):
     """Type that refers to a TypeVarTuple.
@@ -895,6 +969,31 @@ def deserialize(cls, data: JsonDict) -> TypeVarTupleType:
             min_len=data["min_len"],
         )
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, TYPE_VAR_TUPLE_TYPE)
+        self.tuple_fallback.write(data)
+        write_str(data, self.name)
+        write_str(data, self.fullname)
+        write_int(data, self.id.raw_id)
+        write_str(data, self.id.namespace)
+        self.upper_bound.write(data)
+        self.default.write(data)
+        write_int(data, self.min_len)
+
+    @classmethod
+    def read(cls, data: Buffer) -> TypeVarTupleType:
+        assert read_tag(data) == INSTANCE
+        fallback = Instance.read(data)
+        return TypeVarTupleType(
+            read_str(data),
+            read_str(data),
+            TypeVarId(read_int(data), namespace=read_str(data)),
+            read_type(data),
+            fallback,
+            read_type(data),
+            min_len=read_int(data),
+        )
+
     def accept(self, visitor: TypeVisitor[T]) -> T:
         return visitor.visit_type_var_tuple(self)
 
@@ -1026,6 +1125,22 @@ def deserialize(cls, data: JsonDict) -> UnboundType:
             original_str_fallback=data["expr_fallback"],
         )
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, UNBOUND_TYPE)
+        write_str(data, self.name)
+        write_type_list(data, self.args)
+        write_str_opt(data, self.original_str_expr)
+        write_str_opt(data, self.original_str_fallback)
+
+    @classmethod
+    def read(cls, data: Buffer) -> UnboundType:
+        return UnboundType(
+            read_str(data),
+            read_type_list(data),
+            original_str_expr=read_str_opt(data),
+            original_str_fallback=read_str_opt(data),
+        )
+
 
 class CallableArgument(ProperType):
     """Represents a Arg(type, 'name') inside a Callable's type list.
@@ -1120,6 +1235,14 @@ def accept(self, visitor: TypeVisitor[T]) -> T:
     def serialize(self) -> JsonDict:
         return {".class": "UnpackType", "type": self.type.serialize()}
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, UNPACK_TYPE)
+        self.type.write(data)
+
+    @classmethod
+    def read(cls, data: Buffer) -> UnpackType:
+        return UnpackType(read_type(data))
+
     @classmethod
     def deserialize(cls, data: JsonDict) -> UnpackType:
         assert data[".class"] == "UnpackType"
@@ -1221,6 +1344,21 @@ def deserialize(cls, data: JsonDict) -> AnyType:
             data["missing_import_name"],
         )
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, ANY_TYPE)
+        write_type_opt(data, self.source_any)
+        write_int(data, self.type_of_any)
+        write_str_opt(data, self.missing_import_name)
+
+    @classmethod
+    def read(cls, data: Buffer) -> AnyType:
+        if read_bool(data):
+            assert read_tag(data) == ANY_TYPE
+            source_any = AnyType.read(data)
+        else:
+            source_any = None
+        return AnyType(read_int(data), source_any, read_str_opt(data))
+
 
 class UninhabitedType(ProperType):
     """This type has no members.
@@ -1254,10 +1392,10 @@ def accept(self, visitor: TypeVisitor[T]) -> T:
         return visitor.visit_uninhabited_type(self)
 
     def __hash__(self) -> int:
-        return hash(UninhabitedType)
+        return hash((UninhabitedType, self.ambiguous))
 
     def __eq__(self, other: object) -> bool:
-        return isinstance(other, UninhabitedType)
+        return isinstance(other, UninhabitedType) and other.ambiguous == self.ambiguous
 
     def serialize(self) -> JsonDict:
         return {".class": "UninhabitedType"}
@@ -1267,6 +1405,13 @@ def deserialize(cls, data: JsonDict) -> UninhabitedType:
         assert data[".class"] == "UninhabitedType"
         return UninhabitedType()
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, UNINHABITED_TYPE)
+
+    @classmethod
+    def read(cls, data: Buffer) -> UninhabitedType:
+        return UninhabitedType()
+
 
 class NoneType(ProperType):
     """The type of 'None'.
@@ -1299,6 +1444,13 @@ def deserialize(cls, data: JsonDict) -> NoneType:
         assert data[".class"] == "NoneType"
         return NoneType()
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, NONE_TYPE)
+
+    @classmethod
+    def read(cls, data: Buffer) -> NoneType:
+        return NoneType()
+
     def is_singleton_type(self) -> bool:
         return True
 
@@ -1346,6 +1498,14 @@ def deserialize(cls, data: JsonDict) -> DeletedType:
         assert data[".class"] == "DeletedType"
         return DeletedType(data["source"])
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, DELETED_TYPE)
+        write_str_opt(data, self.source)
+
+    @classmethod
+    def read(cls, data: Buffer) -> DeletedType:
+        return DeletedType(read_str_opt(data))
+
 
 # Fake TypeInfo to be used as a placeholder during Instance de-serialization.
 NOT_READY: Final = mypy.nodes.FakeInfo("De-serialization failure: TypeInfo not fixed")
@@ -1388,7 +1548,7 @@ def serialize(self) -> JsonDict:
         return {
             ".class": "ExtraAttrs",
             "attrs": {k: v.serialize() for k, v in self.attrs.items()},
-            "immutable": list(self.immutable),
+            "immutable": sorted(self.immutable),
             "mod_name": self.mod_name,
         }
 
@@ -1401,6 +1561,15 @@ def deserialize(cls, data: JsonDict) -> ExtraAttrs:
             data["mod_name"],
         )
 
+    def write(self, data: Buffer) -> None:
+        write_type_map(data, self.attrs)
+        write_str_list(data, sorted(self.immutable))
+        write_str_opt(data, self.mod_name)
+
+    @classmethod
+    def read(cls, data: Buffer) -> ExtraAttrs:
+        return ExtraAttrs(read_type_map(data), set(read_str_list(data)), read_str_opt(data))
+
 
 class Instance(ProperType):
     """An instance type of form C[T1, ..., Tn].
@@ -1505,7 +1674,7 @@ def __eq__(self, other: object) -> bool:
     def serialize(self) -> JsonDict | str:
         assert self.type is not None
         type_ref = self.type.fullname
-        if not self.args and not self.last_known_value:
+        if not self.args and not self.last_known_value and not self.extra_attrs:
             return type_ref
         data: JsonDict = {
             ".class": "Instance",
@@ -1537,6 +1706,29 @@ def deserialize(cls, data: JsonDict | str) -> Instance:
             inst.extra_attrs = ExtraAttrs.deserialize(data["extra_attrs"])
         return inst
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, INSTANCE)
+        write_str(data, self.type.fullname)
+        write_type_list(data, self.args)
+        write_type_opt(data, self.last_known_value)
+        if self.extra_attrs is None:
+            write_bool(data, False)
+        else:
+            write_bool(data, True)
+            self.extra_attrs.write(data)
+
+    @classmethod
+    def read(cls, data: Buffer) -> Instance:
+        type_ref = read_str(data)
+        inst = Instance(NOT_READY, read_type_list(data))
+        inst.type_ref = type_ref
+        if read_bool(data):
+            assert read_tag(data) == LITERAL_TYPE
+            inst.last_known_value = LiteralType.read(data)
+        if read_bool(data):
+            inst.extra_attrs = ExtraAttrs.read(data)
+        return inst
+
     def copy_modified(
         self,
         *,
@@ -1553,7 +1745,6 @@ def copy_modified(
             ),
             extra_attrs=self.extra_attrs,
         )
-        # We intentionally don't copy the extra_attrs here, so they will be erased.
         new.can_be_true = self.can_be_true
         new.can_be_false = self.can_be_false
         return new
@@ -1574,7 +1765,7 @@ def is_singleton_type(self) -> bool:
         return (
             self.type.is_enum
             and len(self.type.enum_members) == 1
-            or self.type.fullname in {"builtins.ellipsis", "types.EllipsisType"}
+            or self.type.fullname in ELLIPSIS_TYPE_NAMES
         )
 
 
@@ -1614,11 +1805,25 @@ def bound(self) -> bool:
         return bool(self.items) and self.items[0].is_bound
 
 
-class FormalArgument(NamedTuple):
-    name: str | None
-    pos: int | None
-    typ: Type
-    required: bool
+class FormalArgument:
+    def __init__(self, name: str | None, pos: int | None, typ: Type, required: bool) -> None:
+        self.name = name
+        self.pos = pos
+        self.typ = typ
+        self.required = required
+
+    def __eq__(self, other: object) -> bool:
+        if not isinstance(other, FormalArgument):
+            return NotImplemented
+        return (
+            self.name == other.name
+            and self.pos == other.pos
+            and self.typ == other.typ
+            and self.required == other.required
+        )
+
+    def __hash__(self) -> int:
+        return hash((self.name, self.pos, self.typ, self.required))
 
 
 class Parameters(ProperType):
@@ -1791,12 +1996,34 @@ def deserialize(cls, data: JsonDict) -> Parameters:
         assert data[".class"] == "Parameters"
         return Parameters(
             [deserialize_type(t) for t in data["arg_types"]],
-            [ArgKind(x) for x in data["arg_kinds"]],
+            # This is a micro-optimization until mypyc gets dedicated enum support. Otherwise,
+            # we would spend ~20% of types deserialization time in Enum.__call__().
+            [ARG_KINDS[x] for x in data["arg_kinds"]],
             data["arg_names"],
             variables=[cast(TypeVarLikeType, deserialize_type(v)) for v in data["variables"]],
             imprecise_arg_kinds=data["imprecise_arg_kinds"],
         )
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, PARAMETERS)
+        write_type_list(data, self.arg_types)
+        write_int_list(data, [int(x.value) for x in self.arg_kinds])
+        write_str_opt_list(data, self.arg_names)
+        write_type_list(data, self.variables)
+        write_bool(data, self.imprecise_arg_kinds)
+
+    @classmethod
+    def read(cls, data: Buffer) -> Parameters:
+        return Parameters(
+            read_type_list(data),
+            # This is a micro-optimization until mypyc gets dedicated enum support. Otherwise,
+            # we would spend ~20% of types deserialization time in Enum.__call__().
+            [ARG_KINDS[ak] for ak in read_int_list(data)],
+            read_str_opt_list(data),
+            variables=[read_type_var_like(data) for _ in range(read_int(data))],
+            imprecise_arg_kinds=read_bool(data),
+        )
+
     def __hash__(self) -> int:
         return hash(
             (
@@ -1808,7 +2035,7 @@ def __hash__(self) -> int:
         )
 
     def __eq__(self, other: object) -> bool:
-        if isinstance(other, (Parameters, CallableType)):
+        if isinstance(other, Parameters):
             return (
                 self.arg_types == other.arg_types
                 and self.arg_names == other.arg_names
@@ -1843,8 +2070,6 @@ class CallableType(FunctionLike):
         "from_type_type",  # Was this callable generated by analyzing Type[...]
         # instantiation?
         "is_bound",  # Is this a bound method?
-        "def_extras",  # Information about original definition we want to serialize.
-        # This is used for more detailed error messages.
         "type_guard",  # T, if -> TypeGuard[T] (ret_type is bool in this case).
         "type_is",  # T, if -> TypeIs[T] (ret_type is bool in this case).
         "from_concatenate",  # whether this callable is from a concatenate object
@@ -1871,7 +2096,6 @@ def __init__(
         special_sig: str | None = None,
         from_type_type: bool = False,
         is_bound: bool = False,
-        def_extras: dict[str, Any] | None = None,
         type_guard: Type | None = None,
         type_is: Type | None = None,
         from_concatenate: bool = False,
@@ -1880,14 +2104,12 @@ def __init__(
     ) -> None:
         super().__init__(line, column)
         assert len(arg_types) == len(arg_kinds) == len(arg_names)
-        for t, k in zip(arg_types, arg_kinds):
+        self.arg_types = list(arg_types)
+        for t in self.arg_types:
             if isinstance(t, ParamSpecType):
                 assert not t.prefix.arg_types
                 # TODO: should we assert that only ARG_STAR contain ParamSpecType?
                 # See testParamSpecJoin, that relies on passing e.g `P.args` as plain argument.
-        if variables is None:
-            variables = []
-        self.arg_types = list(arg_types)
         self.arg_kinds = arg_kinds
         self.arg_names = list(arg_names)
         self.min_args = arg_kinds.count(ARG_POS)
@@ -1895,8 +2117,15 @@ def __init__(
         self.fallback = fallback
         assert not name or "<bound method" not in name
         self.name = name
+        # The rules for what exactly is considered a definition:
+        #   * If it is a non-decorated function, FuncDef is the definition
+        #   * If it is a decorated function, enclosing Decorator is the definition
         self.definition = definition
-        self.variables = variables
+        self.variables: tuple[TypeVarLikeType, ...]
+        if variables is None:
+            self.variables = ()
+        else:
+            self.variables = tuple(variables)
         self.is_ellipsis_args = is_ellipsis_args
         self.implicit = implicit
         self.special_sig = special_sig
@@ -1904,22 +2133,6 @@ def __init__(
         self.from_concatenate = from_concatenate
         self.imprecise_arg_kinds = imprecise_arg_kinds
         self.is_bound = is_bound
-        if def_extras:
-            self.def_extras = def_extras
-        elif isinstance(definition, FuncDef):
-            # This information would be lost if we don't have definition
-            # after serialization, but it is useful in error messages.
-            # TODO: decide how to add more info here (file, line, column)
-            # without changing interface hash.
-            first_arg: str | None = None
-            if definition.arg_names and definition.info and not definition.is_static:
-                if getattr(definition, "arguments", None):
-                    first_arg = definition.arguments[0].variable.name
-                else:
-                    first_arg = definition.arg_names[0]
-            self.def_extras = {"first_arg": first_arg}
-        else:
-            self.def_extras = {}
         self.type_guard = type_guard
         self.type_is = type_is
         self.unpack_kwargs = unpack_kwargs
@@ -1941,7 +2154,6 @@ def copy_modified(
         special_sig: Bogus[str | None] = _dummy,
         from_type_type: Bogus[bool] = _dummy,
         is_bound: Bogus[bool] = _dummy,
-        def_extras: Bogus[dict[str, Any]] = _dummy,
         type_guard: Bogus[Type | None] = _dummy,
         type_is: Bogus[Type | None] = _dummy,
         from_concatenate: Bogus[bool] = _dummy,
@@ -1966,7 +2178,6 @@ def copy_modified(
             special_sig=special_sig if special_sig is not _dummy else self.special_sig,
             from_type_type=from_type_type if from_type_type is not _dummy else self.from_type_type,
             is_bound=is_bound if is_bound is not _dummy else self.is_bound,
-            def_extras=def_extras if def_extras is not _dummy else dict(self.def_extras),
             type_guard=type_guard if type_guard is not _dummy else self.type_guard,
             type_is=type_is if type_is is not _dummy else self.type_is,
             from_concatenate=(
@@ -2242,15 +2453,9 @@ def with_normalized_var_args(self) -> Self:
         )
 
     def __hash__(self) -> int:
-        # self.is_type_obj() will fail if self.fallback.type is a FakeInfo
-        if isinstance(self.fallback.type, FakeInfo):
-            is_type_obj = 2
-        else:
-            is_type_obj = self.is_type_obj()
         return hash(
             (
                 self.ret_type,
-                is_type_obj,
                 self.is_ellipsis_args,
                 self.name,
                 tuple(self.arg_types),
@@ -2268,8 +2473,9 @@ def __eq__(self, other: object) -> bool:
                 and self.arg_names == other.arg_names
                 and self.arg_kinds == other.arg_kinds
                 and self.name == other.name
-                and self.is_type_obj() == other.is_type_obj()
                 and self.is_ellipsis_args == other.is_ellipsis_args
+                and self.type_guard == other.type_guard
+                and self.type_is == other.type_is
                 and self.fallback == other.fallback
             )
         else:
@@ -2291,7 +2497,6 @@ def serialize(self) -> JsonDict:
             "is_ellipsis_args": self.is_ellipsis_args,
             "implicit": self.implicit,
             "is_bound": self.is_bound,
-            "def_extras": dict(self.def_extras),
             "type_guard": self.type_guard.serialize() if self.type_guard is not None else None,
             "type_is": (self.type_is.serialize() if self.type_is is not None else None),
             "from_concatenate": self.from_concatenate,
@@ -2302,10 +2507,10 @@ def serialize(self) -> JsonDict:
     @classmethod
     def deserialize(cls, data: JsonDict) -> CallableType:
         assert data[".class"] == "CallableType"
-        # TODO: Set definition to the containing SymbolNode?
+        # The .definition link is set in fixup.py.
         return CallableType(
             [deserialize_type(t) for t in data["arg_types"]],
-            [ArgKind(x) for x in data["arg_kinds"]],
+            [ARG_KINDS[x] for x in data["arg_kinds"]],
             data["arg_names"],
             deserialize_type(data["ret_type"]),
             Instance.deserialize(data["fallback"]),
@@ -2314,7 +2519,6 @@ def deserialize(cls, data: JsonDict) -> CallableType:
             is_ellipsis_args=data["is_ellipsis_args"],
             implicit=data["implicit"],
             is_bound=data["is_bound"],
-            def_extras=data["def_extras"],
             type_guard=(
                 deserialize_type(data["type_guard"]) if data["type_guard"] is not None else None
             ),
@@ -2324,6 +2528,46 @@ def deserialize(cls, data: JsonDict) -> CallableType:
             unpack_kwargs=data["unpack_kwargs"],
         )
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, CALLABLE_TYPE)
+        self.fallback.write(data)
+        write_type_list(data, self.arg_types)
+        write_int_list(data, [int(x.value) for x in self.arg_kinds])
+        write_str_opt_list(data, self.arg_names)
+        self.ret_type.write(data)
+        write_str_opt(data, self.name)
+        write_type_list(data, self.variables)
+        write_bool(data, self.is_ellipsis_args)
+        write_bool(data, self.implicit)
+        write_bool(data, self.is_bound)
+        write_type_opt(data, self.type_guard)
+        write_type_opt(data, self.type_is)
+        write_bool(data, self.from_concatenate)
+        write_bool(data, self.imprecise_arg_kinds)
+        write_bool(data, self.unpack_kwargs)
+
+    @classmethod
+    def read(cls, data: Buffer) -> CallableType:
+        assert read_tag(data) == INSTANCE
+        fallback = Instance.read(data)
+        return CallableType(
+            read_type_list(data),
+            [ARG_KINDS[ak] for ak in read_int_list(data)],
+            read_str_opt_list(data),
+            read_type(data),
+            fallback,
+            name=read_str_opt(data),
+            variables=[read_type_var_like(data) for _ in range(read_int(data))],
+            is_ellipsis_args=read_bool(data),
+            implicit=read_bool(data),
+            is_bound=read_bool(data),
+            type_guard=read_type_opt(data),
+            type_is=read_type_opt(data),
+            from_concatenate=read_bool(data),
+            imprecise_arg_kinds=read_bool(data),
+            unpack_kwargs=read_bool(data),
+        )
+
 
 # This is a little safety net to prevent reckless special-casing of callables
 # that can potentially break Unpack[...] with **kwargs.
@@ -2399,6 +2643,18 @@ def deserialize(cls, data: JsonDict) -> Overloaded:
         assert data[".class"] == "Overloaded"
         return Overloaded([CallableType.deserialize(t) for t in data["items"]])
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, OVERLOADED)
+        write_type_list(data, self.items)
+
+    @classmethod
+    def read(cls, data: Buffer) -> Overloaded:
+        items = []
+        for _ in range(read_int(data)):
+            assert read_tag(data) == CALLABLE_TYPE
+            items.append(CallableType.read(data))
+        return Overloaded(items)
+
 
 class TupleType(ProperType):
     """The tuple type Tuple[T1, ..., Tn] (at least one type argument).
@@ -2495,6 +2751,18 @@ def deserialize(cls, data: JsonDict) -> TupleType:
             implicit=data["implicit"],
         )
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, TUPLE_TYPE)
+        self.partial_fallback.write(data)
+        write_type_list(data, self.items)
+        write_bool(data, self.implicit)
+
+    @classmethod
+    def read(cls, data: Buffer) -> TupleType:
+        assert read_tag(data) == INSTANCE
+        fallback = Instance.read(data)
+        return TupleType(read_type_list(data), fallback, implicit=read_bool(data))
+
     def copy_modified(
         self, *, fallback: Instance | None = None, items: list[Type] | None = None
     ) -> TupleType:
@@ -2665,6 +2933,21 @@ def deserialize(cls, data: JsonDict) -> TypedDictType:
             Instance.deserialize(data["fallback"]),
         )
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, TYPED_DICT_TYPE)
+        self.fallback.write(data)
+        write_type_map(data, self.items)
+        write_str_list(data, sorted(self.required_keys))
+        write_str_list(data, sorted(self.readonly_keys))
+
+    @classmethod
+    def read(cls, data: Buffer) -> TypedDictType:
+        assert read_tag(data) == INSTANCE
+        fallback = Instance.read(data)
+        return TypedDictType(
+            read_type_map(data), set(read_str_list(data)), set(read_str_list(data)), fallback
+        )
+
     @property
     def is_final(self) -> bool:
         return self.fallback.type.is_final
@@ -2913,6 +3196,18 @@ def deserialize(cls, data: JsonDict) -> LiteralType:
         assert data[".class"] == "LiteralType"
         return LiteralType(value=data["value"], fallback=Instance.deserialize(data["fallback"]))
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, LITERAL_TYPE)
+        self.fallback.write(data)
+        write_literal(data, self.value)
+
+    @classmethod
+    def read(cls, data: Buffer) -> LiteralType:
+        assert read_tag(data) == INSTANCE
+        fallback = Instance.read(data)
+        tag = read_tag(data)
+        return LiteralType(read_literal(data, tag), fallback)
+
     def is_singleton_type(self) -> bool:
         return self.is_enum_literal() or isinstance(self.value, bool)
 
@@ -2963,6 +3258,8 @@ def __hash__(self) -> int:
     def __eq__(self, other: object) -> bool:
         if not isinstance(other, UnionType):
             return NotImplemented
+        if self is other:
+            return True
         return frozenset(self.items) == frozenset(other.items)
 
     @overload
@@ -3012,6 +3309,15 @@ def deserialize(cls, data: JsonDict) -> UnionType:
             uses_pep604_syntax=data["uses_pep604_syntax"],
         )
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, UNION_TYPE)
+        write_type_list(data, self.items)
+        write_bool(data, self.uses_pep604_syntax)
+
+    @classmethod
+    def read(cls, data: Buffer) -> UnionType:
+        return UnionType(read_type_list(data), uses_pep604_syntax=read_bool(data))
+
 
 class PartialType(ProperType):
     """Type such as List[?] where type arguments are unknown, or partial None type.
@@ -3148,6 +3454,14 @@ def deserialize(cls, data: JsonDict) -> Type:
         assert data[".class"] == "TypeType"
         return TypeType.make_normalized(deserialize_type(data["item"]))
 
+    def write(self, data: Buffer) -> None:
+        write_tag(data, TYPE_TYPE)
+        self.item.write(data)
+
+    @classmethod
+    def read(cls, data: Buffer) -> Type:
+        return TypeType.make_normalized(read_type(data))
+
 
 class PlaceholderType(ProperType):
     """Temporary, yet-unknown type during semantic analysis.
@@ -3210,7 +3524,8 @@ def get_proper_type(typ: Type | None) -> ProperType | None:
     """
     if typ is None:
         return None
-    if isinstance(typ, TypeGuardedType):  # type: ignore[misc]
+    # TODO: this is an ugly hack, remove.
+    if isinstance(typ, TypeGuardedType):
         typ = typ.type_guard
     while isinstance(typ, TypeAliasType):
         typ = typ._expand_once()
@@ -3234,9 +3549,7 @@ def get_proper_types(
     if isinstance(types, list):
         typelist = types
         # Optimize for the common case so that we don't need to allocate anything
-        if not any(
-            isinstance(t, (TypeAliasType, TypeGuardedType)) for t in typelist  # type: ignore[misc]
-        ):
+        if not any(isinstance(t, (TypeAliasType, TypeGuardedType)) for t in typelist):
             return cast("list[ProperType]", typelist)
         return [get_proper_type(t) for t in typelist]
     else:
@@ -3256,7 +3569,6 @@ def get_proper_types(
     TypeTranslator as TypeTranslator,
     TypeVisitor as TypeVisitor,
 )
-from mypy.typetraverser import TypeTraverserVisitor
 
 
 class TypeStrVisitor(SyntheticTypeVisitor[str]):
@@ -3594,23 +3906,6 @@ def is_named_instance(t: Type, fullnames: str | tuple[str, ...]) -> TypeGuard[In
     return isinstance(t, Instance) and t.type.fullname in fullnames
 
 
-class LocationSetter(TypeTraverserVisitor):
-    # TODO: Should we update locations of other Type subclasses?
-    def __init__(self, line: int, column: int) -> None:
-        self.line = line
-        self.column = column
-
-    def visit_instance(self, typ: Instance) -> None:
-        typ.line = self.line
-        typ.column = self.column
-        super().visit_instance(typ)
-
-    def visit_type_alias_type(self, typ: TypeAliasType) -> None:
-        typ.line = self.line
-        typ.column = self.column
-        super().visit_type_alias_type(typ)
-
-
 class HasTypeVars(BoolTypeQuery):
     """Visitor for querying whether a type has a type variable component."""
 
@@ -3705,8 +4000,8 @@ def flatten_nested_unions(
 
     flat_items: list[Type] = []
     for t in typelist:
-        if handle_type_alias_type:
-            if not handle_recursive and isinstance(t, TypeAliasType) and t.is_recursive:
+        if handle_type_alias_type and isinstance(t, TypeAliasType):
+            if not handle_recursive and t.is_recursive:
                 tp: Type = t
             else:
                 tp = get_proper_type(t)
@@ -3753,7 +4048,21 @@ def flatten_nested_tuples(types: Iterable[Type]) -> list[Type]:
         if not isinstance(p_type, TupleType):
             res.append(typ)
             continue
-        res.extend(flatten_nested_tuples(p_type.items))
+        if isinstance(typ.type, TypeAliasType):
+            items = []
+            for item in p_type.items:
+                if (
+                    isinstance(item, ProperType)
+                    and isinstance(item, Instance)
+                    or isinstance(item, TypeAliasType)
+                ):
+                    if len(item.args) == 0:
+                        item = item.copy_modified()
+                        item.set_line(typ)
+                items.append(item)
+        else:
+            items = p_type.items
+        res.extend(flatten_nested_tuples(items))
     return res
 
 
@@ -3813,6 +4122,128 @@ def type_vars_as_args(type_vars: Sequence[TypeVarLikeType]) -> tuple[Type, ...]:
     return tuple(args)
 
 
+TYPE_ALIAS_TYPE: Final[Tag] = 1
+TYPE_VAR_TYPE: Final[Tag] = 2
+PARAM_SPEC_TYPE: Final[Tag] = 3
+TYPE_VAR_TUPLE_TYPE: Final[Tag] = 4
+UNBOUND_TYPE: Final[Tag] = 5
+UNPACK_TYPE: Final[Tag] = 6
+ANY_TYPE: Final[Tag] = 7
+UNINHABITED_TYPE: Final[Tag] = 8
+NONE_TYPE: Final[Tag] = 9
+DELETED_TYPE: Final[Tag] = 10
+INSTANCE: Final[Tag] = 11
+CALLABLE_TYPE: Final[Tag] = 12
+OVERLOADED: Final[Tag] = 13
+TUPLE_TYPE: Final[Tag] = 14
+TYPED_DICT_TYPE: Final[Tag] = 15
+LITERAL_TYPE: Final[Tag] = 16
+UNION_TYPE: Final[Tag] = 17
+TYPE_TYPE: Final[Tag] = 18
+PARAMETERS: Final[Tag] = 19
+
+
+def read_type(data: Buffer) -> Type:
+    tag = read_tag(data)
+    # The branches here are ordered manually by type "popularity".
+    if tag == INSTANCE:
+        return Instance.read(data)
+    if tag == ANY_TYPE:
+        return AnyType.read(data)
+    if tag == TYPE_VAR_TYPE:
+        return TypeVarType.read(data)
+    if tag == CALLABLE_TYPE:
+        return CallableType.read(data)
+    if tag == NONE_TYPE:
+        return NoneType.read(data)
+    if tag == UNION_TYPE:
+        return UnionType.read(data)
+    if tag == LITERAL_TYPE:
+        return LiteralType.read(data)
+    if tag == TYPE_ALIAS_TYPE:
+        return TypeAliasType.read(data)
+    if tag == TUPLE_TYPE:
+        return TupleType.read(data)
+    if tag == TYPED_DICT_TYPE:
+        return TypedDictType.read(data)
+    if tag == TYPE_TYPE:
+        return TypeType.read(data)
+    if tag == OVERLOADED:
+        return Overloaded.read(data)
+    if tag == PARAM_SPEC_TYPE:
+        return ParamSpecType.read(data)
+    if tag == TYPE_VAR_TUPLE_TYPE:
+        return TypeVarTupleType.read(data)
+    if tag == UNPACK_TYPE:
+        return UnpackType.read(data)
+    if tag == PARAMETERS:
+        return Parameters.read(data)
+    if tag == UNINHABITED_TYPE:
+        return UninhabitedType.read(data)
+    if tag == UNBOUND_TYPE:
+        return UnboundType.read(data)
+    if tag == DELETED_TYPE:
+        return DeletedType.read(data)
+    assert False, f"Unknown type tag {tag}"
+
+
+def read_function_like(data: Buffer) -> FunctionLike:
+    tag = read_tag(data)
+    if tag == CALLABLE_TYPE:
+        return CallableType.read(data)
+    if tag == OVERLOADED:
+        return Overloaded.read(data)
+    assert False, f"Invalid type tag for FunctionLike {tag}"
+
+
+def read_type_var_like(data: Buffer) -> TypeVarLikeType:
+    tag = read_tag(data)
+    if tag == TYPE_VAR_TYPE:
+        return TypeVarType.read(data)
+    if tag == PARAM_SPEC_TYPE:
+        return ParamSpecType.read(data)
+    if tag == TYPE_VAR_TUPLE_TYPE:
+        return TypeVarTupleType.read(data)
+    assert False, f"Invalid type tag for TypeVarLikeType {tag}"
+
+
+def read_type_opt(data: Buffer) -> Type | None:
+    if read_bool(data):
+        return read_type(data)
+    return None
+
+
+def write_type_opt(data: Buffer, value: Type | None) -> None:
+    if value is not None:
+        write_bool(data, True)
+        value.write(data)
+    else:
+        write_bool(data, False)
+
+
+def read_type_list(data: Buffer) -> list[Type]:
+    size = read_int(data)
+    return [read_type(data) for _ in range(size)]
+
+
+def write_type_list(data: Buffer, value: Sequence[Type]) -> None:
+    write_int(data, len(value))
+    for item in value:
+        item.write(data)
+
+
+def read_type_map(data: Buffer) -> dict[str, Type]:
+    size = read_int(data)
+    return {read_str(data): read_type(data) for _ in range(size)}
+
+
+def write_type_map(data: Buffer, value: dict[str, Type]) -> None:
+    write_int(data, len(value))
+    for key in sorted(value):
+        write_str(data, key)
+        value[key].write(data)
+
+
 # This cyclic import is unfortunate, but to avoid it we would need to move away all uses
 # of get_proper_type() from types.py. Majority of them have been removed, but few remaining
 # are quite tricky to get rid of, but ultimately we want to do it at some point.
diff --git a/mypy/typeshed/stdlib/VERSIONS b/mypy/typeshed/stdlib/VERSIONS
index 1ecd8af64559..6fcf0161790d 100644
--- a/mypy/typeshed/stdlib/VERSIONS
+++ b/mypy/typeshed/stdlib/VERSIONS
@@ -76,6 +76,7 @@ _warnings: 3.0-
 _weakref: 3.0-
 _weakrefset: 3.0-
 _winapi: 3.3-
+_zstd: 3.14-
 abc: 3.0-
 aifc: 3.0-3.12
 annotationlib: 3.14-
@@ -94,6 +95,7 @@ asyncio.staggered: 3.8-
 asyncio.taskgroups: 3.11-
 asyncio.threads: 3.9-
 asyncio.timeouts: 3.11-
+asyncio.tools: 3.14-
 asyncio.trsock: 3.8-
 asyncore: 3.0-3.11
 atexit: 3.0-
@@ -122,6 +124,7 @@ compileall: 3.0-
 compression: 3.14-
 concurrent: 3.2-
 concurrent.futures.interpreter: 3.14-
+concurrent.interpreters: 3.14-
 configparser: 3.0-
 contextlib: 3.0-
 contextvars: 3.7-
diff --git a/mypy/typeshed/stdlib/_ast.pyi b/mypy/typeshed/stdlib/_ast.pyi
index 00c6b357f7d8..d8d5a1829991 100644
--- a/mypy/typeshed/stdlib/_ast.pyi
+++ b/mypy/typeshed/stdlib/_ast.pyi
@@ -108,7 +108,7 @@ from ast import (
     unaryop as unaryop,
     withitem as withitem,
 )
-from typing import Literal
+from typing import Final
 
 if sys.version_info >= (3, 12):
     from ast import (
@@ -137,9 +137,9 @@ if sys.version_info >= (3, 10):
         pattern as pattern,
     )
 
-PyCF_ALLOW_TOP_LEVEL_AWAIT: Literal[8192]
-PyCF_ONLY_AST: Literal[1024]
-PyCF_TYPE_COMMENTS: Literal[4096]
+PyCF_ALLOW_TOP_LEVEL_AWAIT: Final = 8192
+PyCF_ONLY_AST: Final = 1024
+PyCF_TYPE_COMMENTS: Final = 4096
 
 if sys.version_info >= (3, 13):
-    PyCF_OPTIMIZED_AST: Literal[33792]
+    PyCF_OPTIMIZED_AST: Final = 33792
diff --git a/mypy/typeshed/stdlib/_asyncio.pyi b/mypy/typeshed/stdlib/_asyncio.pyi
index 5253e967e5a3..f43178e4d725 100644
--- a/mypy/typeshed/stdlib/_asyncio.pyi
+++ b/mypy/typeshed/stdlib/_asyncio.pyi
@@ -4,12 +4,13 @@ from collections.abc import Awaitable, Callable, Coroutine, Generator, Iterable
 from contextvars import Context
 from types import FrameType, GenericAlias
 from typing import Any, Literal, TextIO, TypeVar
-from typing_extensions import Self, TypeAlias
+from typing_extensions import Self, TypeAlias, disjoint_base
 
 _T = TypeVar("_T")
 _T_co = TypeVar("_T_co", covariant=True)
 _TaskYieldType: TypeAlias = Future[object] | None
 
+@disjoint_base
 class Future(Awaitable[_T], Iterable[_T]):
     _state: str
     @property
@@ -20,7 +21,7 @@ class Future(Awaitable[_T], Iterable[_T]):
     @_log_traceback.setter
     def _log_traceback(self, val: Literal[False]) -> None: ...
     _asyncio_future_blocking: bool  # is a part of duck-typing contract for `Future`
-    def __init__(self, *, loop: AbstractEventLoop | None = ...) -> None: ...
+    def __init__(self, *, loop: AbstractEventLoop | None = None) -> None: ...
     def __del__(self) -> None: ...
     def get_loop(self) -> AbstractEventLoop: ...
     @property
@@ -49,6 +50,7 @@ else:
 # While this is true in general, here it's sort-of okay to have a covariant subclass,
 # since the only reason why `asyncio.Future` is invariant is the `set_result()` method,
 # and `asyncio.Task.set_result()` always raises.
+@disjoint_base
 class Task(Future[_T_co]):  # type: ignore[type-var]  # pyright: ignore[reportInvalidTypeArguments]
     if sys.version_info >= (3, 12):
         def __init__(
@@ -56,7 +58,7 @@ class Task(Future[_T_co]):  # type: ignore[type-var]  # pyright: ignore[reportIn
             coro: _TaskCompatibleCoro[_T_co],
             *,
             loop: AbstractEventLoop | None = None,
-            name: str | None = ...,
+            name: str | None = None,
             context: Context | None = None,
             eager_start: bool = False,
         ) -> None: ...
@@ -66,12 +68,12 @@ class Task(Future[_T_co]):  # type: ignore[type-var]  # pyright: ignore[reportIn
             coro: _TaskCompatibleCoro[_T_co],
             *,
             loop: AbstractEventLoop | None = None,
-            name: str | None = ...,
+            name: str | None = None,
             context: Context | None = None,
         ) -> None: ...
     else:
         def __init__(
-            self, coro: _TaskCompatibleCoro[_T_co], *, loop: AbstractEventLoop | None = None, name: str | None = ...
+            self, coro: _TaskCompatibleCoro[_T_co], *, loop: AbstractEventLoop | None = None, name: str | None = None
         ) -> None: ...
 
     if sys.version_info >= (3, 12):
diff --git a/mypy/typeshed/stdlib/_blake2.pyi b/mypy/typeshed/stdlib/_blake2.pyi
index d578df55c2fa..a6c3869fb851 100644
--- a/mypy/typeshed/stdlib/_blake2.pyi
+++ b/mypy/typeshed/stdlib/_blake2.pyi
@@ -1,15 +1,16 @@
+import sys
 from _typeshed import ReadableBuffer
-from typing import ClassVar, final
+from typing import ClassVar, Final, final
 from typing_extensions import Self
 
-BLAKE2B_MAX_DIGEST_SIZE: int = 64
-BLAKE2B_MAX_KEY_SIZE: int = 64
-BLAKE2B_PERSON_SIZE: int = 16
-BLAKE2B_SALT_SIZE: int = 16
-BLAKE2S_MAX_DIGEST_SIZE: int = 32
-BLAKE2S_MAX_KEY_SIZE: int = 32
-BLAKE2S_PERSON_SIZE: int = 8
-BLAKE2S_SALT_SIZE: int = 8
+BLAKE2B_MAX_DIGEST_SIZE: Final = 64
+BLAKE2B_MAX_KEY_SIZE: Final = 64
+BLAKE2B_PERSON_SIZE: Final = 16
+BLAKE2B_SALT_SIZE: Final = 16
+BLAKE2S_MAX_DIGEST_SIZE: Final = 32
+BLAKE2S_MAX_KEY_SIZE: Final = 32
+BLAKE2S_PERSON_SIZE: Final = 8
+BLAKE2S_SALT_SIZE: Final = 8
 
 @final
 class blake2b:
@@ -20,24 +21,45 @@ class blake2b:
     block_size: int
     digest_size: int
     name: str
-    def __new__(
-        cls,
-        data: ReadableBuffer = b"",
-        /,
-        *,
-        digest_size: int = 64,
-        key: ReadableBuffer = b"",
-        salt: ReadableBuffer = b"",
-        person: ReadableBuffer = b"",
-        fanout: int = 1,
-        depth: int = 1,
-        leaf_size: int = 0,
-        node_offset: int = 0,
-        node_depth: int = 0,
-        inner_size: int = 0,
-        last_node: bool = False,
-        usedforsecurity: bool = True,
-    ) -> Self: ...
+    if sys.version_info >= (3, 13):
+        def __new__(
+            cls,
+            data: ReadableBuffer = b"",
+            *,
+            digest_size: int = 64,
+            key: ReadableBuffer = b"",
+            salt: ReadableBuffer = b"",
+            person: ReadableBuffer = b"",
+            fanout: int = 1,
+            depth: int = 1,
+            leaf_size: int = 0,
+            node_offset: int = 0,
+            node_depth: int = 0,
+            inner_size: int = 0,
+            last_node: bool = False,
+            usedforsecurity: bool = True,
+            string: ReadableBuffer | None = None,
+        ) -> Self: ...
+    else:
+        def __new__(
+            cls,
+            data: ReadableBuffer = b"",
+            /,
+            *,
+            digest_size: int = 64,
+            key: ReadableBuffer = b"",
+            salt: ReadableBuffer = b"",
+            person: ReadableBuffer = b"",
+            fanout: int = 1,
+            depth: int = 1,
+            leaf_size: int = 0,
+            node_offset: int = 0,
+            node_depth: int = 0,
+            inner_size: int = 0,
+            last_node: bool = False,
+            usedforsecurity: bool = True,
+        ) -> Self: ...
+
     def copy(self) -> Self: ...
     def digest(self) -> bytes: ...
     def hexdigest(self) -> str: ...
@@ -52,24 +74,45 @@ class blake2s:
     block_size: int
     digest_size: int
     name: str
-    def __new__(
-        cls,
-        data: ReadableBuffer = b"",
-        /,
-        *,
-        digest_size: int = 32,
-        key: ReadableBuffer = b"",
-        salt: ReadableBuffer = b"",
-        person: ReadableBuffer = b"",
-        fanout: int = 1,
-        depth: int = 1,
-        leaf_size: int = 0,
-        node_offset: int = 0,
-        node_depth: int = 0,
-        inner_size: int = 0,
-        last_node: bool = False,
-        usedforsecurity: bool = True,
-    ) -> Self: ...
+    if sys.version_info >= (3, 13):
+        def __new__(
+            cls,
+            data: ReadableBuffer = b"",
+            *,
+            digest_size: int = 32,
+            key: ReadableBuffer = b"",
+            salt: ReadableBuffer = b"",
+            person: ReadableBuffer = b"",
+            fanout: int = 1,
+            depth: int = 1,
+            leaf_size: int = 0,
+            node_offset: int = 0,
+            node_depth: int = 0,
+            inner_size: int = 0,
+            last_node: bool = False,
+            usedforsecurity: bool = True,
+            string: ReadableBuffer | None = None,
+        ) -> Self: ...
+    else:
+        def __new__(
+            cls,
+            data: ReadableBuffer = b"",
+            /,
+            *,
+            digest_size: int = 32,
+            key: ReadableBuffer = b"",
+            salt: ReadableBuffer = b"",
+            person: ReadableBuffer = b"",
+            fanout: int = 1,
+            depth: int = 1,
+            leaf_size: int = 0,
+            node_offset: int = 0,
+            node_depth: int = 0,
+            inner_size: int = 0,
+            last_node: bool = False,
+            usedforsecurity: bool = True,
+        ) -> Self: ...
+
     def copy(self) -> Self: ...
     def digest(self) -> bytes: ...
     def hexdigest(self) -> str: ...
diff --git a/mypy/typeshed/stdlib/_collections_abc.pyi b/mypy/typeshed/stdlib/_collections_abc.pyi
index b099bdd98f3c..c63606a13ca9 100644
--- a/mypy/typeshed/stdlib/_collections_abc.pyi
+++ b/mypy/typeshed/stdlib/_collections_abc.pyi
@@ -103,5 +103,6 @@ class dict_items(ItemsView[_KT_co, _VT_co]):  # undocumented
 if sys.version_info >= (3, 12):
     @runtime_checkable
     class Buffer(Protocol):
+        __slots__ = ()
         @abstractmethod
         def __buffer__(self, flags: int, /) -> memoryview: ...
diff --git a/mypy/typeshed/stdlib/_compat_pickle.pyi b/mypy/typeshed/stdlib/_compat_pickle.pyi
index 50fb22442cc9..32c0b542d991 100644
--- a/mypy/typeshed/stdlib/_compat_pickle.pyi
+++ b/mypy/typeshed/stdlib/_compat_pickle.pyi
@@ -1,8 +1,10 @@
-IMPORT_MAPPING: dict[str, str]
-NAME_MAPPING: dict[tuple[str, str], tuple[str, str]]
-PYTHON2_EXCEPTIONS: tuple[str, ...]
-MULTIPROCESSING_EXCEPTIONS: tuple[str, ...]
-REVERSE_IMPORT_MAPPING: dict[str, str]
-REVERSE_NAME_MAPPING: dict[tuple[str, str], tuple[str, str]]
-PYTHON3_OSERROR_EXCEPTIONS: tuple[str, ...]
-PYTHON3_IMPORTERROR_EXCEPTIONS: tuple[str, ...]
+from typing import Final
+
+IMPORT_MAPPING: Final[dict[str, str]]
+NAME_MAPPING: Final[dict[tuple[str, str], tuple[str, str]]]
+PYTHON2_EXCEPTIONS: Final[tuple[str, ...]]
+MULTIPROCESSING_EXCEPTIONS: Final[tuple[str, ...]]
+REVERSE_IMPORT_MAPPING: Final[dict[str, str]]
+REVERSE_NAME_MAPPING: Final[dict[tuple[str, str], tuple[str, str]]]
+PYTHON3_OSERROR_EXCEPTIONS: Final[tuple[str, ...]]
+PYTHON3_IMPORTERROR_EXCEPTIONS: Final[tuple[str, ...]]
diff --git a/mypy/typeshed/stdlib/_compression.pyi b/mypy/typeshed/stdlib/_compression.pyi
index 80d38b4db824..aa67df2ab478 100644
--- a/mypy/typeshed/stdlib/_compression.pyi
+++ b/mypy/typeshed/stdlib/_compression.pyi
@@ -3,10 +3,11 @@
 from _typeshed import Incomplete, WriteableBuffer
 from collections.abc import Callable
 from io import DEFAULT_BUFFER_SIZE, BufferedIOBase, RawIOBase
-from typing import Any, Protocol
+from typing import Any, Protocol, type_check_only
 
 BUFFER_SIZE = DEFAULT_BUFFER_SIZE
 
+@type_check_only
 class _Reader(Protocol):
     def read(self, n: int, /) -> bytes: ...
     def seekable(self) -> bool: ...
diff --git a/mypy/typeshed/stdlib/_contextvars.pyi b/mypy/typeshed/stdlib/_contextvars.pyi
index e2e2e4df9d08..0ddeca7882cd 100644
--- a/mypy/typeshed/stdlib/_contextvars.pyi
+++ b/mypy/typeshed/stdlib/_contextvars.pyi
@@ -39,7 +39,7 @@ class Token(Generic[_T]):
     if sys.version_info >= (3, 14):
         def __enter__(self) -> Self: ...
         def __exit__(
-            self, exc_type: type[BaseException] | None, exc_value: BaseException | None, traceback: TracebackType | None
+            self, exc_type: type[BaseException] | None, exc_value: BaseException | None, traceback: TracebackType | None, /
         ) -> None: ...
 
 def copy_context() -> Context: ...
diff --git a/mypy/typeshed/stdlib/_csv.pyi b/mypy/typeshed/stdlib/_csv.pyi
index ecea4878907c..4128178c18b3 100644
--- a/mypy/typeshed/stdlib/_csv.pyi
+++ b/mypy/typeshed/stdlib/_csv.pyi
@@ -3,7 +3,7 @@ import sys
 from _typeshed import SupportsWrite
 from collections.abc import Iterable
 from typing import Any, Final, Literal, type_check_only
-from typing_extensions import Self, TypeAlias
+from typing_extensions import Self, TypeAlias, disjoint_base
 
 __version__: Final[str]
 
@@ -24,6 +24,7 @@ class Error(Exception): ...
 
 _DialectLike: TypeAlias = str | Dialect | csv.Dialect | type[Dialect | csv.Dialect]
 
+@disjoint_base
 class Dialect:
     delimiter: str
     quotechar: str | None
@@ -35,7 +36,7 @@ class Dialect:
     strict: bool
     def __new__(
         cls,
-        dialect: _DialectLike | None = ...,
+        dialect: _DialectLike | None = None,
         delimiter: str = ",",
         doublequote: bool = True,
         escapechar: str | None = None,
@@ -48,6 +49,7 @@ class Dialect:
 
 if sys.version_info >= (3, 10):
     # This class calls itself _csv.reader.
+    @disjoint_base
     class Reader:
         @property
         def dialect(self) -> Dialect: ...
@@ -56,6 +58,7 @@ if sys.version_info >= (3, 10):
         def __next__(self) -> list[str]: ...
 
     # This class calls itself _csv.writer.
+    @disjoint_base
     class Writer:
         @property
         def dialect(self) -> Dialect: ...
@@ -90,6 +93,7 @@ else:
 
 def writer(
     csvfile: SupportsWrite[str],
+    /,
     dialect: _DialectLike = "excel",
     *,
     delimiter: str = ",",
@@ -103,6 +107,7 @@ def writer(
 ) -> _writer: ...
 def reader(
     csvfile: Iterable[str],
+    /,
     dialect: _DialectLike = "excel",
     *,
     delimiter: str = ",",
diff --git a/mypy/typeshed/stdlib/_ctypes.pyi b/mypy/typeshed/stdlib/_ctypes.pyi
index e134066f0bcf..082a31f70562 100644
--- a/mypy/typeshed/stdlib/_ctypes.pyi
+++ b/mypy/typeshed/stdlib/_ctypes.pyi
@@ -5,24 +5,24 @@ from abc import abstractmethod
 from collections.abc import Callable, Iterable, Iterator, Mapping, Sequence
 from ctypes import CDLL, ArgumentError as ArgumentError, c_void_p
 from types import GenericAlias
-from typing import Any, ClassVar, Generic, TypeVar, final, overload, type_check_only
+from typing import Any, ClassVar, Final, Generic, TypeVar, final, overload, type_check_only
 from typing_extensions import Self, TypeAlias
 
 _T = TypeVar("_T")
 _CT = TypeVar("_CT", bound=_CData)
 
-FUNCFLAG_CDECL: int
-FUNCFLAG_PYTHONAPI: int
-FUNCFLAG_USE_ERRNO: int
-FUNCFLAG_USE_LASTERROR: int
-RTLD_GLOBAL: int
-RTLD_LOCAL: int
+FUNCFLAG_CDECL: Final = 0x1
+FUNCFLAG_PYTHONAPI: Final = 0x4
+FUNCFLAG_USE_ERRNO: Final = 0x8
+FUNCFLAG_USE_LASTERROR: Final = 0x10
+RTLD_GLOBAL: Final[int]
+RTLD_LOCAL: Final[int]
 
 if sys.version_info >= (3, 11):
-    CTYPES_MAX_ARGCOUNT: int
+    CTYPES_MAX_ARGCOUNT: Final[int]
 
 if sys.version_info >= (3, 12):
-    SIZEOF_TIME_T: int
+    SIZEOF_TIME_T: Final[int]
 
 if sys.platform == "win32":
     # Description, Source, HelpFile, HelpContext, scode
@@ -37,8 +37,8 @@ if sys.platform == "win32":
 
     def CopyComPointer(src: _PointerLike, dst: _PointerLike | _CArgObject) -> int: ...
 
-    FUNCFLAG_HRESULT: int
-    FUNCFLAG_STDCALL: int
+    FUNCFLAG_HRESULT: Final = 0x2
+    FUNCFLAG_STDCALL: Final = 0x0
 
     def FormatError(code: int = ...) -> str: ...
     def get_last_error() -> int: ...
@@ -103,7 +103,10 @@ class _SimpleCData(_CData, Generic[_T], metaclass=_PyCSimpleType):
     def __init__(self, value: _T = ...) -> None: ...  # pyright: ignore[reportInvalidTypeVarUse]
     def __ctypes_from_outparam__(self, /) -> _T: ...  # type: ignore[override]
 
+@type_check_only
 class _CanCastTo(_CData): ...
+
+@type_check_only
 class _PointerLike(_CanCastTo): ...
 
 # This type is not exposed. It calls itself _ctypes.PyCPointerType.
@@ -114,7 +117,7 @@ class _PyCPointerType(_CTypeBaseType):
     def from_buffer_copy(self: type[_typeshed.Self], buffer: ReadableBuffer, offset: int = 0, /) -> _typeshed.Self: ...
     def from_param(self: type[_typeshed.Self], value: Any, /) -> _typeshed.Self | _CArgObject: ...
     def in_dll(self: type[_typeshed.Self], dll: CDLL, name: str, /) -> _typeshed.Self: ...
-    def set_type(self, type: Any, /) -> None: ...
+    def set_type(self, type: _CTypeBaseType, /) -> None: ...
     if sys.version_info < (3, 13):
         # Inherited from CType_Type starting on 3.13
         def __mul__(cls: type[_CT], other: int) -> type[Array[_CT]]: ...  # type: ignore[misc] # pyright: ignore[reportGeneralTypeIssues]
diff --git a/mypy/typeshed/stdlib/_curses.pyi b/mypy/typeshed/stdlib/_curses.pyi
index f21a9ca60270..d4e4d48f4e20 100644
--- a/mypy/typeshed/stdlib/_curses.pyi
+++ b/mypy/typeshed/stdlib/_curses.pyi
@@ -1,7 +1,7 @@
 import sys
 from _typeshed import ReadOnlyBuffer, SupportsRead, SupportsWrite
 from curses import _ncurses_version
-from typing import Any, final, overload
+from typing import Any, Final, final, overload
 from typing_extensions import TypeAlias
 
 # NOTE: This module is ordinarily only available on Unix, but the windows-curses
@@ -11,270 +11,270 @@ from typing_extensions import TypeAlias
 _ChType: TypeAlias = str | bytes | int
 
 # ACS codes are only initialized after initscr is called
-ACS_BBSS: int
-ACS_BLOCK: int
-ACS_BOARD: int
-ACS_BSBS: int
-ACS_BSSB: int
-ACS_BSSS: int
-ACS_BTEE: int
-ACS_BULLET: int
-ACS_CKBOARD: int
-ACS_DARROW: int
-ACS_DEGREE: int
-ACS_DIAMOND: int
-ACS_GEQUAL: int
-ACS_HLINE: int
-ACS_LANTERN: int
-ACS_LARROW: int
-ACS_LEQUAL: int
-ACS_LLCORNER: int
-ACS_LRCORNER: int
-ACS_LTEE: int
-ACS_NEQUAL: int
-ACS_PI: int
-ACS_PLMINUS: int
-ACS_PLUS: int
-ACS_RARROW: int
-ACS_RTEE: int
-ACS_S1: int
-ACS_S3: int
-ACS_S7: int
-ACS_S9: int
-ACS_SBBS: int
-ACS_SBSB: int
-ACS_SBSS: int
-ACS_SSBB: int
-ACS_SSBS: int
-ACS_SSSB: int
-ACS_SSSS: int
-ACS_STERLING: int
-ACS_TTEE: int
-ACS_UARROW: int
-ACS_ULCORNER: int
-ACS_URCORNER: int
-ACS_VLINE: int
-ALL_MOUSE_EVENTS: int
-A_ALTCHARSET: int
-A_ATTRIBUTES: int
-A_BLINK: int
-A_BOLD: int
-A_CHARTEXT: int
-A_COLOR: int
-A_DIM: int
-A_HORIZONTAL: int
-A_INVIS: int
-A_ITALIC: int
-A_LEFT: int
-A_LOW: int
-A_NORMAL: int
-A_PROTECT: int
-A_REVERSE: int
-A_RIGHT: int
-A_STANDOUT: int
-A_TOP: int
-A_UNDERLINE: int
-A_VERTICAL: int
-BUTTON1_CLICKED: int
-BUTTON1_DOUBLE_CLICKED: int
-BUTTON1_PRESSED: int
-BUTTON1_RELEASED: int
-BUTTON1_TRIPLE_CLICKED: int
-BUTTON2_CLICKED: int
-BUTTON2_DOUBLE_CLICKED: int
-BUTTON2_PRESSED: int
-BUTTON2_RELEASED: int
-BUTTON2_TRIPLE_CLICKED: int
-BUTTON3_CLICKED: int
-BUTTON3_DOUBLE_CLICKED: int
-BUTTON3_PRESSED: int
-BUTTON3_RELEASED: int
-BUTTON3_TRIPLE_CLICKED: int
-BUTTON4_CLICKED: int
-BUTTON4_DOUBLE_CLICKED: int
-BUTTON4_PRESSED: int
-BUTTON4_RELEASED: int
-BUTTON4_TRIPLE_CLICKED: int
+ACS_BBSS: Final[int]
+ACS_BLOCK: Final[int]
+ACS_BOARD: Final[int]
+ACS_BSBS: Final[int]
+ACS_BSSB: Final[int]
+ACS_BSSS: Final[int]
+ACS_BTEE: Final[int]
+ACS_BULLET: Final[int]
+ACS_CKBOARD: Final[int]
+ACS_DARROW: Final[int]
+ACS_DEGREE: Final[int]
+ACS_DIAMOND: Final[int]
+ACS_GEQUAL: Final[int]
+ACS_HLINE: Final[int]
+ACS_LANTERN: Final[int]
+ACS_LARROW: Final[int]
+ACS_LEQUAL: Final[int]
+ACS_LLCORNER: Final[int]
+ACS_LRCORNER: Final[int]
+ACS_LTEE: Final[int]
+ACS_NEQUAL: Final[int]
+ACS_PI: Final[int]
+ACS_PLMINUS: Final[int]
+ACS_PLUS: Final[int]
+ACS_RARROW: Final[int]
+ACS_RTEE: Final[int]
+ACS_S1: Final[int]
+ACS_S3: Final[int]
+ACS_S7: Final[int]
+ACS_S9: Final[int]
+ACS_SBBS: Final[int]
+ACS_SBSB: Final[int]
+ACS_SBSS: Final[int]
+ACS_SSBB: Final[int]
+ACS_SSBS: Final[int]
+ACS_SSSB: Final[int]
+ACS_SSSS: Final[int]
+ACS_STERLING: Final[int]
+ACS_TTEE: Final[int]
+ACS_UARROW: Final[int]
+ACS_ULCORNER: Final[int]
+ACS_URCORNER: Final[int]
+ACS_VLINE: Final[int]
+ALL_MOUSE_EVENTS: Final[int]
+A_ALTCHARSET: Final[int]
+A_ATTRIBUTES: Final[int]
+A_BLINK: Final[int]
+A_BOLD: Final[int]
+A_CHARTEXT: Final[int]
+A_COLOR: Final[int]
+A_DIM: Final[int]
+A_HORIZONTAL: Final[int]
+A_INVIS: Final[int]
+A_ITALIC: Final[int]
+A_LEFT: Final[int]
+A_LOW: Final[int]
+A_NORMAL: Final[int]
+A_PROTECT: Final[int]
+A_REVERSE: Final[int]
+A_RIGHT: Final[int]
+A_STANDOUT: Final[int]
+A_TOP: Final[int]
+A_UNDERLINE: Final[int]
+A_VERTICAL: Final[int]
+BUTTON1_CLICKED: Final[int]
+BUTTON1_DOUBLE_CLICKED: Final[int]
+BUTTON1_PRESSED: Final[int]
+BUTTON1_RELEASED: Final[int]
+BUTTON1_TRIPLE_CLICKED: Final[int]
+BUTTON2_CLICKED: Final[int]
+BUTTON2_DOUBLE_CLICKED: Final[int]
+BUTTON2_PRESSED: Final[int]
+BUTTON2_RELEASED: Final[int]
+BUTTON2_TRIPLE_CLICKED: Final[int]
+BUTTON3_CLICKED: Final[int]
+BUTTON3_DOUBLE_CLICKED: Final[int]
+BUTTON3_PRESSED: Final[int]
+BUTTON3_RELEASED: Final[int]
+BUTTON3_TRIPLE_CLICKED: Final[int]
+BUTTON4_CLICKED: Final[int]
+BUTTON4_DOUBLE_CLICKED: Final[int]
+BUTTON4_PRESSED: Final[int]
+BUTTON4_RELEASED: Final[int]
+BUTTON4_TRIPLE_CLICKED: Final[int]
 # Darwin ncurses doesn't provide BUTTON5_* constants prior to 3.12.10 and 3.13.3
 if sys.version_info >= (3, 10):
     if sys.version_info >= (3, 12) or sys.platform != "darwin":
-        BUTTON5_PRESSED: int
-        BUTTON5_RELEASED: int
-        BUTTON5_CLICKED: int
-        BUTTON5_DOUBLE_CLICKED: int
-        BUTTON5_TRIPLE_CLICKED: int
-BUTTON_ALT: int
-BUTTON_CTRL: int
-BUTTON_SHIFT: int
-COLOR_BLACK: int
-COLOR_BLUE: int
-COLOR_CYAN: int
-COLOR_GREEN: int
-COLOR_MAGENTA: int
-COLOR_RED: int
-COLOR_WHITE: int
-COLOR_YELLOW: int
-ERR: int
-KEY_A1: int
-KEY_A3: int
-KEY_B2: int
-KEY_BACKSPACE: int
-KEY_BEG: int
-KEY_BREAK: int
-KEY_BTAB: int
-KEY_C1: int
-KEY_C3: int
-KEY_CANCEL: int
-KEY_CATAB: int
-KEY_CLEAR: int
-KEY_CLOSE: int
-KEY_COMMAND: int
-KEY_COPY: int
-KEY_CREATE: int
-KEY_CTAB: int
-KEY_DC: int
-KEY_DL: int
-KEY_DOWN: int
-KEY_EIC: int
-KEY_END: int
-KEY_ENTER: int
-KEY_EOL: int
-KEY_EOS: int
-KEY_EXIT: int
-KEY_F0: int
-KEY_F1: int
-KEY_F10: int
-KEY_F11: int
-KEY_F12: int
-KEY_F13: int
-KEY_F14: int
-KEY_F15: int
-KEY_F16: int
-KEY_F17: int
-KEY_F18: int
-KEY_F19: int
-KEY_F2: int
-KEY_F20: int
-KEY_F21: int
-KEY_F22: int
-KEY_F23: int
-KEY_F24: int
-KEY_F25: int
-KEY_F26: int
-KEY_F27: int
-KEY_F28: int
-KEY_F29: int
-KEY_F3: int
-KEY_F30: int
-KEY_F31: int
-KEY_F32: int
-KEY_F33: int
-KEY_F34: int
-KEY_F35: int
-KEY_F36: int
-KEY_F37: int
-KEY_F38: int
-KEY_F39: int
-KEY_F4: int
-KEY_F40: int
-KEY_F41: int
-KEY_F42: int
-KEY_F43: int
-KEY_F44: int
-KEY_F45: int
-KEY_F46: int
-KEY_F47: int
-KEY_F48: int
-KEY_F49: int
-KEY_F5: int
-KEY_F50: int
-KEY_F51: int
-KEY_F52: int
-KEY_F53: int
-KEY_F54: int
-KEY_F55: int
-KEY_F56: int
-KEY_F57: int
-KEY_F58: int
-KEY_F59: int
-KEY_F6: int
-KEY_F60: int
-KEY_F61: int
-KEY_F62: int
-KEY_F63: int
-KEY_F7: int
-KEY_F8: int
-KEY_F9: int
-KEY_FIND: int
-KEY_HELP: int
-KEY_HOME: int
-KEY_IC: int
-KEY_IL: int
-KEY_LEFT: int
-KEY_LL: int
-KEY_MARK: int
-KEY_MAX: int
-KEY_MESSAGE: int
-KEY_MIN: int
-KEY_MOUSE: int
-KEY_MOVE: int
-KEY_NEXT: int
-KEY_NPAGE: int
-KEY_OPEN: int
-KEY_OPTIONS: int
-KEY_PPAGE: int
-KEY_PREVIOUS: int
-KEY_PRINT: int
-KEY_REDO: int
-KEY_REFERENCE: int
-KEY_REFRESH: int
-KEY_REPLACE: int
-KEY_RESET: int
-KEY_RESIZE: int
-KEY_RESTART: int
-KEY_RESUME: int
-KEY_RIGHT: int
-KEY_SAVE: int
-KEY_SBEG: int
-KEY_SCANCEL: int
-KEY_SCOMMAND: int
-KEY_SCOPY: int
-KEY_SCREATE: int
-KEY_SDC: int
-KEY_SDL: int
-KEY_SELECT: int
-KEY_SEND: int
-KEY_SEOL: int
-KEY_SEXIT: int
-KEY_SF: int
-KEY_SFIND: int
-KEY_SHELP: int
-KEY_SHOME: int
-KEY_SIC: int
-KEY_SLEFT: int
-KEY_SMESSAGE: int
-KEY_SMOVE: int
-KEY_SNEXT: int
-KEY_SOPTIONS: int
-KEY_SPREVIOUS: int
-KEY_SPRINT: int
-KEY_SR: int
-KEY_SREDO: int
-KEY_SREPLACE: int
-KEY_SRESET: int
-KEY_SRIGHT: int
-KEY_SRSUME: int
-KEY_SSAVE: int
-KEY_SSUSPEND: int
-KEY_STAB: int
-KEY_SUNDO: int
-KEY_SUSPEND: int
-KEY_UNDO: int
-KEY_UP: int
-OK: int
-REPORT_MOUSE_POSITION: int
+        BUTTON5_PRESSED: Final[int]
+        BUTTON5_RELEASED: Final[int]
+        BUTTON5_CLICKED: Final[int]
+        BUTTON5_DOUBLE_CLICKED: Final[int]
+        BUTTON5_TRIPLE_CLICKED: Final[int]
+BUTTON_ALT: Final[int]
+BUTTON_CTRL: Final[int]
+BUTTON_SHIFT: Final[int]
+COLOR_BLACK: Final[int]
+COLOR_BLUE: Final[int]
+COLOR_CYAN: Final[int]
+COLOR_GREEN: Final[int]
+COLOR_MAGENTA: Final[int]
+COLOR_RED: Final[int]
+COLOR_WHITE: Final[int]
+COLOR_YELLOW: Final[int]
+ERR: Final[int]
+KEY_A1: Final[int]
+KEY_A3: Final[int]
+KEY_B2: Final[int]
+KEY_BACKSPACE: Final[int]
+KEY_BEG: Final[int]
+KEY_BREAK: Final[int]
+KEY_BTAB: Final[int]
+KEY_C1: Final[int]
+KEY_C3: Final[int]
+KEY_CANCEL: Final[int]
+KEY_CATAB: Final[int]
+KEY_CLEAR: Final[int]
+KEY_CLOSE: Final[int]
+KEY_COMMAND: Final[int]
+KEY_COPY: Final[int]
+KEY_CREATE: Final[int]
+KEY_CTAB: Final[int]
+KEY_DC: Final[int]
+KEY_DL: Final[int]
+KEY_DOWN: Final[int]
+KEY_EIC: Final[int]
+KEY_END: Final[int]
+KEY_ENTER: Final[int]
+KEY_EOL: Final[int]
+KEY_EOS: Final[int]
+KEY_EXIT: Final[int]
+KEY_F0: Final[int]
+KEY_F1: Final[int]
+KEY_F10: Final[int]
+KEY_F11: Final[int]
+KEY_F12: Final[int]
+KEY_F13: Final[int]
+KEY_F14: Final[int]
+KEY_F15: Final[int]
+KEY_F16: Final[int]
+KEY_F17: Final[int]
+KEY_F18: Final[int]
+KEY_F19: Final[int]
+KEY_F2: Final[int]
+KEY_F20: Final[int]
+KEY_F21: Final[int]
+KEY_F22: Final[int]
+KEY_F23: Final[int]
+KEY_F24: Final[int]
+KEY_F25: Final[int]
+KEY_F26: Final[int]
+KEY_F27: Final[int]
+KEY_F28: Final[int]
+KEY_F29: Final[int]
+KEY_F3: Final[int]
+KEY_F30: Final[int]
+KEY_F31: Final[int]
+KEY_F32: Final[int]
+KEY_F33: Final[int]
+KEY_F34: Final[int]
+KEY_F35: Final[int]
+KEY_F36: Final[int]
+KEY_F37: Final[int]
+KEY_F38: Final[int]
+KEY_F39: Final[int]
+KEY_F4: Final[int]
+KEY_F40: Final[int]
+KEY_F41: Final[int]
+KEY_F42: Final[int]
+KEY_F43: Final[int]
+KEY_F44: Final[int]
+KEY_F45: Final[int]
+KEY_F46: Final[int]
+KEY_F47: Final[int]
+KEY_F48: Final[int]
+KEY_F49: Final[int]
+KEY_F5: Final[int]
+KEY_F50: Final[int]
+KEY_F51: Final[int]
+KEY_F52: Final[int]
+KEY_F53: Final[int]
+KEY_F54: Final[int]
+KEY_F55: Final[int]
+KEY_F56: Final[int]
+KEY_F57: Final[int]
+KEY_F58: Final[int]
+KEY_F59: Final[int]
+KEY_F6: Final[int]
+KEY_F60: Final[int]
+KEY_F61: Final[int]
+KEY_F62: Final[int]
+KEY_F63: Final[int]
+KEY_F7: Final[int]
+KEY_F8: Final[int]
+KEY_F9: Final[int]
+KEY_FIND: Final[int]
+KEY_HELP: Final[int]
+KEY_HOME: Final[int]
+KEY_IC: Final[int]
+KEY_IL: Final[int]
+KEY_LEFT: Final[int]
+KEY_LL: Final[int]
+KEY_MARK: Final[int]
+KEY_MAX: Final[int]
+KEY_MESSAGE: Final[int]
+KEY_MIN: Final[int]
+KEY_MOUSE: Final[int]
+KEY_MOVE: Final[int]
+KEY_NEXT: Final[int]
+KEY_NPAGE: Final[int]
+KEY_OPEN: Final[int]
+KEY_OPTIONS: Final[int]
+KEY_PPAGE: Final[int]
+KEY_PREVIOUS: Final[int]
+KEY_PRINT: Final[int]
+KEY_REDO: Final[int]
+KEY_REFERENCE: Final[int]
+KEY_REFRESH: Final[int]
+KEY_REPLACE: Final[int]
+KEY_RESET: Final[int]
+KEY_RESIZE: Final[int]
+KEY_RESTART: Final[int]
+KEY_RESUME: Final[int]
+KEY_RIGHT: Final[int]
+KEY_SAVE: Final[int]
+KEY_SBEG: Final[int]
+KEY_SCANCEL: Final[int]
+KEY_SCOMMAND: Final[int]
+KEY_SCOPY: Final[int]
+KEY_SCREATE: Final[int]
+KEY_SDC: Final[int]
+KEY_SDL: Final[int]
+KEY_SELECT: Final[int]
+KEY_SEND: Final[int]
+KEY_SEOL: Final[int]
+KEY_SEXIT: Final[int]
+KEY_SF: Final[int]
+KEY_SFIND: Final[int]
+KEY_SHELP: Final[int]
+KEY_SHOME: Final[int]
+KEY_SIC: Final[int]
+KEY_SLEFT: Final[int]
+KEY_SMESSAGE: Final[int]
+KEY_SMOVE: Final[int]
+KEY_SNEXT: Final[int]
+KEY_SOPTIONS: Final[int]
+KEY_SPREVIOUS: Final[int]
+KEY_SPRINT: Final[int]
+KEY_SR: Final[int]
+KEY_SREDO: Final[int]
+KEY_SREPLACE: Final[int]
+KEY_SRESET: Final[int]
+KEY_SRIGHT: Final[int]
+KEY_SRSUME: Final[int]
+KEY_SSAVE: Final[int]
+KEY_SSUSPEND: Final[int]
+KEY_STAB: Final[int]
+KEY_SUNDO: Final[int]
+KEY_SUSPEND: Final[int]
+KEY_UNDO: Final[int]
+KEY_UP: Final[int]
+OK: Final[int]
+REPORT_MOUSE_POSITION: Final[int]
 _C_API: Any
-version: bytes
+version: Final[bytes]
 
 def baudrate() -> int: ...
 def beep() -> None: ...
@@ -324,7 +324,7 @@ def mouseinterval(interval: int, /) -> None: ...
 def mousemask(newmask: int, /) -> tuple[int, int]: ...
 def napms(ms: int, /) -> int: ...
 def newpad(nlines: int, ncols: int, /) -> window: ...
-def newwin(nlines: int, ncols: int, begin_y: int = ..., begin_x: int = ..., /) -> window: ...
+def newwin(nlines: int, ncols: int, begin_y: int = 0, begin_x: int = 0, /) -> window: ...
 def nl(flag: bool = True, /) -> None: ...
 def nocbreak() -> None: ...
 def noecho() -> None: ...
@@ -394,8 +394,8 @@ class window:  # undocumented
     def attroff(self, attr: int, /) -> None: ...
     def attron(self, attr: int, /) -> None: ...
     def attrset(self, attr: int, /) -> None: ...
-    def bkgd(self, ch: _ChType, attr: int = ..., /) -> None: ...
-    def bkgdset(self, ch: _ChType, attr: int = ..., /) -> None: ...
+    def bkgd(self, ch: _ChType, attr: int = 0, /) -> None: ...
+    def bkgdset(self, ch: _ChType, attr: int = 0, /) -> None: ...
     def border(
         self,
         ls: _ChType = ...,
@@ -410,7 +410,7 @@ class window:  # undocumented
     @overload
     def box(self) -> None: ...
     @overload
-    def box(self, vertch: _ChType = ..., horch: _ChType = ...) -> None: ...
+    def box(self, vertch: _ChType = 0, horch: _ChType = 0) -> None: ...
     @overload
     def chgat(self, attr: int) -> None: ...
     @overload
@@ -433,7 +433,7 @@ class window:  # undocumented
     def derwin(self, begin_y: int, begin_x: int) -> window: ...
     @overload
     def derwin(self, nlines: int, ncols: int, begin_y: int, begin_x: int) -> window: ...
-    def echochar(self, ch: _ChType, attr: int = ..., /) -> None: ...
+    def echochar(self, ch: _ChType, attr: int = 0, /) -> None: ...
     def enclose(self, y: int, x: int, /) -> bool: ...
     def erase(self) -> None: ...
     def getbegyx(self) -> tuple[int, int]: ...
@@ -487,9 +487,9 @@ class window:  # undocumented
     @overload
     def insstr(self, y: int, x: int, str: str, attr: int = ...) -> None: ...
     @overload
-    def instr(self, n: int = ...) -> bytes: ...
+    def instr(self, n: int = 2047) -> bytes: ...
     @overload
-    def instr(self, y: int, x: int, n: int = ...) -> bytes: ...
+    def instr(self, y: int, x: int, n: int = 2047) -> bytes: ...
     def is_linetouched(self, line: int, /) -> bool: ...
     def is_wintouched(self) -> bool: ...
     def keypad(self, yes: bool, /) -> None: ...
@@ -523,7 +523,7 @@ class window:  # undocumented
     @overload
     def refresh(self, pminrow: int, pmincol: int, sminrow: int, smincol: int, smaxrow: int, smaxcol: int) -> None: ...
     def resize(self, nlines: int, ncols: int) -> None: ...
-    def scroll(self, lines: int = ...) -> None: ...
+    def scroll(self, lines: int = 1) -> None: ...
     def scrollok(self, flag: bool) -> None: ...
     def setscrreg(self, top: int, bottom: int, /) -> None: ...
     def standend(self) -> None: ...
@@ -540,7 +540,7 @@ class window:  # undocumented
     def syncok(self, flag: bool) -> None: ...
     def syncup(self) -> None: ...
     def timeout(self, delay: int) -> None: ...
-    def touchline(self, start: int, count: int, changed: bool = ...) -> None: ...
+    def touchline(self, start: int, count: int, changed: bool = True) -> None: ...
     def touchwin(self) -> None: ...
     def untouchwin(self) -> None: ...
     @overload
diff --git a/mypy/typeshed/stdlib/_curses_panel.pyi b/mypy/typeshed/stdlib/_curses_panel.pyi
index ddec22236b96..a552a151ddf1 100644
--- a/mypy/typeshed/stdlib/_curses_panel.pyi
+++ b/mypy/typeshed/stdlib/_curses_panel.pyi
@@ -1,8 +1,8 @@
 from _curses import window
-from typing import final
+from typing import Final, final
 
-__version__: str
-version: str
+__version__: Final[str]
+version: Final[str]
 
 class error(Exception): ...
 
diff --git a/mypy/typeshed/stdlib/_dbm.pyi b/mypy/typeshed/stdlib/_dbm.pyi
index 7e53cca3c704..222c3ffcb246 100644
--- a/mypy/typeshed/stdlib/_dbm.pyi
+++ b/mypy/typeshed/stdlib/_dbm.pyi
@@ -1,7 +1,7 @@
 import sys
 from _typeshed import ReadOnlyBuffer, StrOrBytesPath
 from types import TracebackType
-from typing import TypeVar, final, overload, type_check_only
+from typing import Final, TypeVar, final, overload, type_check_only
 from typing_extensions import Self, TypeAlias
 
 if sys.platform != "win32":
@@ -10,7 +10,7 @@ if sys.platform != "win32":
     _ValueType: TypeAlias = str | ReadOnlyBuffer
 
     class error(OSError): ...
-    library: str
+    library: Final[str]
 
     # Actual typename dbm, not exposed by the implementation
     @final
@@ -33,7 +33,7 @@ if sys.platform != "win32":
         @overload
         def get(self, k: _KeyType, default: _T, /) -> bytes | _T: ...
         def keys(self) -> list[bytes]: ...
-        def setdefault(self, k: _KeyType, default: _ValueType = ..., /) -> bytes: ...
+        def setdefault(self, k: _KeyType, default: _ValueType = b"", /) -> bytes: ...
         # This isn't true, but the class can't be instantiated. See #13024
         __new__: None  # type: ignore[assignment]
         __init__: None  # type: ignore[assignment]
diff --git a/mypy/typeshed/stdlib/_decimal.pyi b/mypy/typeshed/stdlib/_decimal.pyi
index fd0e6e6ac091..3cfe8944dfaf 100644
--- a/mypy/typeshed/stdlib/_decimal.pyi
+++ b/mypy/typeshed/stdlib/_decimal.pyi
@@ -51,14 +51,14 @@ if sys.version_info >= (3, 11):
     def localcontext(
         ctx: Context | None = None,
         *,
-        prec: int | None = ...,
-        rounding: str | None = ...,
-        Emin: int | None = ...,
-        Emax: int | None = ...,
-        capitals: int | None = ...,
-        clamp: int | None = ...,
-        traps: dict[_TrapType, bool] | None = ...,
-        flags: dict[_TrapType, bool] | None = ...,
+        prec: int | None = None,
+        rounding: str | None = None,
+        Emin: int | None = None,
+        Emax: int | None = None,
+        capitals: int | None = None,
+        clamp: int | None = None,
+        traps: dict[_TrapType, bool] | None = None,
+        flags: dict[_TrapType, bool] | None = None,
     ) -> _ContextManager: ...
 
 else:
diff --git a/mypy/typeshed/stdlib/_frozen_importlib.pyi b/mypy/typeshed/stdlib/_frozen_importlib.pyi
index 3dbc8c6b52f0..93aaed82e2e1 100644
--- a/mypy/typeshed/stdlib/_frozen_importlib.pyi
+++ b/mypy/typeshed/stdlib/_frozen_importlib.pyi
@@ -6,6 +6,7 @@ from _typeshed.importlib import LoaderProtocol
 from collections.abc import Mapping, Sequence
 from types import ModuleType
 from typing import Any, ClassVar
+from typing_extensions import deprecated
 
 # Signature of `builtins.__import__` should be kept identical to `importlib.__import__`
 def __import__(
@@ -49,6 +50,7 @@ class BuiltinImporter(importlib.abc.MetaPathFinder, importlib.abc.InspectLoader)
     # MetaPathFinder
     if sys.version_info < (3, 12):
         @classmethod
+        @deprecated("Deprecated since Python 3.4; removed in Python 3.12. Use `find_spec()` instead.")
         def find_module(cls, fullname: str, path: Sequence[str] | None = None) -> importlib.abc.Loader | None: ...
 
     @classmethod
@@ -67,6 +69,10 @@ class BuiltinImporter(importlib.abc.MetaPathFinder, importlib.abc.InspectLoader)
     # Loader
     if sys.version_info < (3, 12):
         @staticmethod
+        @deprecated(
+            "Deprecated since Python 3.4; removed in Python 3.12. "
+            "The module spec is now used by the import machinery to generate a module repr."
+        )
         def module_repr(module: types.ModuleType) -> str: ...
     if sys.version_info >= (3, 10):
         @staticmethod
@@ -83,6 +89,7 @@ class FrozenImporter(importlib.abc.MetaPathFinder, importlib.abc.InspectLoader):
     # MetaPathFinder
     if sys.version_info < (3, 12):
         @classmethod
+        @deprecated("Deprecated since Python 3.4; removed in Python 3.12. Use `find_spec()` instead.")
         def find_module(cls, fullname: str, path: Sequence[str] | None = None) -> importlib.abc.Loader | None: ...
 
     @classmethod
@@ -101,6 +108,10 @@ class FrozenImporter(importlib.abc.MetaPathFinder, importlib.abc.InspectLoader):
     # Loader
     if sys.version_info < (3, 12):
         @staticmethod
+        @deprecated(
+            "Deprecated since Python 3.4; removed in Python 3.12. "
+            "The module spec is now used by the import machinery to generate a module repr."
+        )
         def module_repr(m: types.ModuleType) -> str: ...
     if sys.version_info >= (3, 10):
         @staticmethod
diff --git a/mypy/typeshed/stdlib/_frozen_importlib_external.pyi b/mypy/typeshed/stdlib/_frozen_importlib_external.pyi
index edad50a8d858..71642c65dc07 100644
--- a/mypy/typeshed/stdlib/_frozen_importlib_external.pyi
+++ b/mypy/typeshed/stdlib/_frozen_importlib_external.pyi
@@ -9,7 +9,7 @@ from _typeshed.importlib import LoaderProtocol
 from collections.abc import Callable, Iterable, Iterator, Mapping, MutableSequence, Sequence
 from importlib.machinery import ModuleSpec
 from importlib.metadata import DistributionFinder, PathDistribution
-from typing import Any, Literal
+from typing import Any, Final, Literal
 from typing_extensions import Self, deprecated
 
 if sys.version_info >= (3, 10):
@@ -24,7 +24,7 @@ else:
     path_sep: Literal["/"]
     path_sep_tuple: tuple[Literal["/"]]
 
-MAGIC_NUMBER: bytes
+MAGIC_NUMBER: Final[bytes]
 
 def cache_from_source(path: StrPath, debug_override: bool | None = None, *, optimization: Any | None = None) -> str: ...
 def source_from_cache(path: StrPath) -> str: ...
@@ -37,12 +37,13 @@ def spec_from_file_location(
     submodule_search_locations: list[str] | None = ...,
 ) -> importlib.machinery.ModuleSpec | None: ...
 @deprecated(
-    "Deprecated as of Python 3.6: Use site configuration instead. "
+    "Deprecated since Python 3.6. Use site configuration instead. "
     "Future versions of Python may not enable this finder by default."
 )
 class WindowsRegistryFinder(importlib.abc.MetaPathFinder):
     if sys.version_info < (3, 12):
         @classmethod
+        @deprecated("Deprecated since Python 3.4; removed in Python 3.12. Use `find_spec()` instead.")
         def find_module(cls, fullname: str, path: Sequence[str] | None = None) -> importlib.abc.Loader | None: ...
 
     @classmethod
@@ -70,13 +71,14 @@ class PathFinder(importlib.abc.MetaPathFinder):
     ) -> ModuleSpec | None: ...
     if sys.version_info < (3, 12):
         @classmethod
+        @deprecated("Deprecated since Python 3.4; removed in Python 3.12. Use `find_spec()` instead.")
         def find_module(cls, fullname: str, path: Sequence[str] | None = None) -> importlib.abc.Loader | None: ...
 
-SOURCE_SUFFIXES: list[str]
-DEBUG_BYTECODE_SUFFIXES: list[str]
-OPTIMIZED_BYTECODE_SUFFIXES: list[str]
-BYTECODE_SUFFIXES: list[str]
-EXTENSION_SUFFIXES: list[str]
+SOURCE_SUFFIXES: Final[list[str]]
+DEBUG_BYTECODE_SUFFIXES: Final = [".pyc"]
+OPTIMIZED_BYTECODE_SUFFIXES: Final = [".pyc"]
+BYTECODE_SUFFIXES: Final = [".pyc"]
+EXTENSION_SUFFIXES: Final[list[str]]
 
 class FileFinder(importlib.abc.PathEntryFinder):
     path: str
@@ -153,12 +155,15 @@ if sys.version_info >= (3, 11):
         def get_code(self, fullname: str) -> types.CodeType: ...
         def create_module(self, spec: ModuleSpec) -> None: ...
         def exec_module(self, module: types.ModuleType) -> None: ...
-        @deprecated("load_module() is deprecated; use exec_module() instead")
+        @deprecated("Deprecated since Python 3.10; will be removed in Python 3.15. Use `exec_module()` instead.")
         def load_module(self, fullname: str) -> types.ModuleType: ...
         def get_resource_reader(self, module: types.ModuleType) -> importlib.readers.NamespaceReader: ...
         if sys.version_info < (3, 12):
             @staticmethod
-            @deprecated("module_repr() is deprecated, and has been removed in Python 3.12")
+            @deprecated(
+                "Deprecated since Python 3.4; removed in Python 3.12. "
+                "The module spec is now used by the import machinery to generate a module repr."
+            )
             def module_repr(module: types.ModuleType) -> str: ...
 
     _NamespaceLoader = NamespaceLoader
@@ -172,16 +177,23 @@ else:
         def get_code(self, fullname: str) -> types.CodeType: ...
         def create_module(self, spec: ModuleSpec) -> None: ...
         def exec_module(self, module: types.ModuleType) -> None: ...
-        @deprecated("load_module() is deprecated; use exec_module() instead")
-        def load_module(self, fullname: str) -> types.ModuleType: ...
         if sys.version_info >= (3, 10):
+            @deprecated("Deprecated since Python 3.10; will be removed in Python 3.15. Use `exec_module()` instead.")
+            def load_module(self, fullname: str) -> types.ModuleType: ...
             @staticmethod
-            @deprecated("module_repr() is deprecated, and has been removed in Python 3.12")
+            @deprecated(
+                "Deprecated since Python 3.4; removed in Python 3.12. "
+                "The module spec is now used by the import machinery to generate a module repr."
+            )
             def module_repr(module: types.ModuleType) -> str: ...
             def get_resource_reader(self, module: types.ModuleType) -> importlib.readers.NamespaceReader: ...
         else:
+            def load_module(self, fullname: str) -> types.ModuleType: ...
             @classmethod
-            @deprecated("module_repr() is deprecated, and has been removed in Python 3.12")
+            @deprecated(
+                "Deprecated since Python 3.4; removed in Python 3.12. "
+                "The module spec is now used by the import machinery to generate a module repr."
+            )
             def module_repr(cls, module: types.ModuleType) -> str: ...
 
 if sys.version_info >= (3, 13):
diff --git a/mypy/typeshed/stdlib/_gdbm.pyi b/mypy/typeshed/stdlib/_gdbm.pyi
index 1d1d541f5477..2cb5fba29dfa 100644
--- a/mypy/typeshed/stdlib/_gdbm.pyi
+++ b/mypy/typeshed/stdlib/_gdbm.pyi
@@ -1,7 +1,7 @@
 import sys
 from _typeshed import ReadOnlyBuffer, StrOrBytesPath
 from types import TracebackType
-from typing import TypeVar, overload
+from typing import TypeVar, overload, type_check_only
 from typing_extensions import Self, TypeAlias
 
 if sys.platform != "win32":
@@ -13,6 +13,7 @@ if sys.platform != "win32":
 
     class error(OSError): ...
     # Actual typename gdbm, not exposed by the implementation
+    @type_check_only
     class _gdbm:
         def firstkey(self) -> bytes | None: ...
         def nextkey(self, key: _KeyType) -> bytes | None: ...
diff --git a/mypy/typeshed/stdlib/_hashlib.pyi b/mypy/typeshed/stdlib/_hashlib.pyi
index 746b1657e2db..03c1eef3be3f 100644
--- a/mypy/typeshed/stdlib/_hashlib.pyi
+++ b/mypy/typeshed/stdlib/_hashlib.pyi
@@ -3,7 +3,7 @@ from _typeshed import ReadableBuffer
 from collections.abc import Callable
 from types import ModuleType
 from typing import AnyStr, Protocol, final, overload, type_check_only
-from typing_extensions import Self, TypeAlias
+from typing_extensions import Self, TypeAlias, disjoint_base
 
 _DigestMod: TypeAlias = str | Callable[[], _HashObject] | ModuleType | None
 
@@ -22,6 +22,7 @@ class _HashObject(Protocol):
     def hexdigest(self) -> str: ...
     def update(self, obj: ReadableBuffer, /) -> None: ...
 
+@disjoint_base
 class HASH:
     @property
     def digest_size(self) -> int: ...
@@ -60,19 +61,63 @@ def compare_digest(a: ReadableBuffer, b: ReadableBuffer, /) -> bool: ...
 def compare_digest(a: AnyStr, b: AnyStr, /) -> bool: ...
 def get_fips_mode() -> int: ...
 def hmac_new(key: bytes | bytearray, msg: ReadableBuffer = b"", digestmod: _DigestMod = None) -> HMAC: ...
-def new(name: str, string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASH: ...
-def openssl_md5(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASH: ...
-def openssl_sha1(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASH: ...
-def openssl_sha224(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASH: ...
-def openssl_sha256(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASH: ...
-def openssl_sha384(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASH: ...
-def openssl_sha512(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASH: ...
-def openssl_sha3_224(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASH: ...
-def openssl_sha3_256(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASH: ...
-def openssl_sha3_384(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASH: ...
-def openssl_sha3_512(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASH: ...
-def openssl_shake_128(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASHXOF: ...
-def openssl_shake_256(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASHXOF: ...
+
+if sys.version_info >= (3, 13):
+    def new(
+        name: str, data: ReadableBuffer = b"", *, usedforsecurity: bool = True, string: ReadableBuffer | None = None
+    ) -> HASH: ...
+    def openssl_md5(
+        data: ReadableBuffer = b"", *, usedforsecurity: bool = True, string: ReadableBuffer | None = None
+    ) -> HASH: ...
+    def openssl_sha1(
+        data: ReadableBuffer = b"", *, usedforsecurity: bool = True, string: ReadableBuffer | None = None
+    ) -> HASH: ...
+    def openssl_sha224(
+        data: ReadableBuffer = b"", *, usedforsecurity: bool = True, string: ReadableBuffer | None = None
+    ) -> HASH: ...
+    def openssl_sha256(
+        data: ReadableBuffer = b"", *, usedforsecurity: bool = True, string: ReadableBuffer | None = None
+    ) -> HASH: ...
+    def openssl_sha384(
+        data: ReadableBuffer = b"", *, usedforsecurity: bool = True, string: ReadableBuffer | None = None
+    ) -> HASH: ...
+    def openssl_sha512(
+        data: ReadableBuffer = b"", *, usedforsecurity: bool = True, string: ReadableBuffer | None = None
+    ) -> HASH: ...
+    def openssl_sha3_224(
+        data: ReadableBuffer = b"", *, usedforsecurity: bool = True, string: ReadableBuffer | None = None
+    ) -> HASH: ...
+    def openssl_sha3_256(
+        data: ReadableBuffer = b"", *, usedforsecurity: bool = True, string: ReadableBuffer | None = None
+    ) -> HASH: ...
+    def openssl_sha3_384(
+        data: ReadableBuffer = b"", *, usedforsecurity: bool = True, string: ReadableBuffer | None = None
+    ) -> HASH: ...
+    def openssl_sha3_512(
+        data: ReadableBuffer = b"", *, usedforsecurity: bool = True, string: ReadableBuffer | None = None
+    ) -> HASH: ...
+    def openssl_shake_128(
+        data: ReadableBuffer = b"", *, usedforsecurity: bool = True, string: ReadableBuffer | None = None
+    ) -> HASHXOF: ...
+    def openssl_shake_256(
+        data: ReadableBuffer = b"", *, usedforsecurity: bool = True, string: ReadableBuffer | None = None
+    ) -> HASHXOF: ...
+
+else:
+    def new(name: str, string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASH: ...
+    def openssl_md5(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASH: ...
+    def openssl_sha1(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASH: ...
+    def openssl_sha224(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASH: ...
+    def openssl_sha256(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASH: ...
+    def openssl_sha384(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASH: ...
+    def openssl_sha512(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASH: ...
+    def openssl_sha3_224(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASH: ...
+    def openssl_sha3_256(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASH: ...
+    def openssl_sha3_384(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASH: ...
+    def openssl_sha3_512(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASH: ...
+    def openssl_shake_128(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASHXOF: ...
+    def openssl_shake_256(string: ReadableBuffer = b"", *, usedforsecurity: bool = True) -> HASHXOF: ...
+
 def hmac_digest(key: bytes | bytearray, msg: ReadableBuffer, digest: str) -> bytes: ...
 def pbkdf2_hmac(
     hash_name: str, password: ReadableBuffer, salt: ReadableBuffer, iterations: int, dklen: int | None = None
diff --git a/mypy/typeshed/stdlib/_heapq.pyi b/mypy/typeshed/stdlib/_heapq.pyi
index 3363fbcd7e74..4d7d6aba3241 100644
--- a/mypy/typeshed/stdlib/_heapq.pyi
+++ b/mypy/typeshed/stdlib/_heapq.pyi
@@ -1,18 +1,17 @@
 import sys
-from typing import Any, Final, TypeVar
-
-_T = TypeVar("_T")  # list items must be comparable
+from _typeshed import SupportsRichComparisonT as _T  # All type variable use in this module requires comparability.
+from typing import Final
 
 __about__: Final[str]
 
-def heapify(heap: list[Any], /) -> None: ...  # list items must be comparable
+def heapify(heap: list[_T], /) -> None: ...
 def heappop(heap: list[_T], /) -> _T: ...
 def heappush(heap: list[_T], item: _T, /) -> None: ...
 def heappushpop(heap: list[_T], item: _T, /) -> _T: ...
 def heapreplace(heap: list[_T], item: _T, /) -> _T: ...
 
 if sys.version_info >= (3, 14):
-    def heapify_max(heap: list[Any], /) -> None: ...  # list items must be comparable
+    def heapify_max(heap: list[_T], /) -> None: ...
     def heappop_max(heap: list[_T], /) -> _T: ...
     def heappush_max(heap: list[_T], item: _T, /) -> None: ...
     def heappushpop_max(heap: list[_T], item: _T, /) -> _T: ...
diff --git a/mypy/typeshed/stdlib/_interpchannels.pyi b/mypy/typeshed/stdlib/_interpchannels.pyi
index c03496044df0..a631a6f16616 100644
--- a/mypy/typeshed/stdlib/_interpchannels.pyi
+++ b/mypy/typeshed/stdlib/_interpchannels.pyi
@@ -17,15 +17,15 @@ class ChannelID:
     def send(self) -> Self: ...
     @property
     def recv(self) -> Self: ...
-    def __eq__(self, other: object) -> bool: ...
-    def __ge__(self, other: ChannelID) -> bool: ...
-    def __gt__(self, other: ChannelID) -> bool: ...
+    def __eq__(self, other: object, /) -> bool: ...
+    def __ge__(self, other: ChannelID, /) -> bool: ...
+    def __gt__(self, other: ChannelID, /) -> bool: ...
     def __hash__(self) -> int: ...
     def __index__(self) -> int: ...
     def __int__(self) -> int: ...
-    def __le__(self, other: ChannelID) -> bool: ...
-    def __lt__(self, other: ChannelID) -> bool: ...
-    def __ne__(self, other: object) -> bool: ...
+    def __le__(self, other: ChannelID, /) -> bool: ...
+    def __lt__(self, other: ChannelID, /) -> bool: ...
+    def __ne__(self, other: object, /) -> bool: ...
 
 @final
 class ChannelInfo(structseq[int], tuple[bool, bool, bool, int, int, int, int, int]):
diff --git a/mypy/typeshed/stdlib/_interpreters.pyi b/mypy/typeshed/stdlib/_interpreters.pyi
index caa1115e9d3d..8e097efad618 100644
--- a/mypy/typeshed/stdlib/_interpreters.pyi
+++ b/mypy/typeshed/stdlib/_interpreters.pyi
@@ -1,49 +1,58 @@
 import types
-from collections.abc import Callable, Mapping
-from typing import Final, Literal, SupportsIndex
-from typing_extensions import TypeAlias
+from collections.abc import Callable
+from typing import Any, Final, Literal, SupportsIndex, TypeVar, overload
+from typing_extensions import TypeAlias, disjoint_base
+
+_R = TypeVar("_R")
 
 _Configs: TypeAlias = Literal["default", "isolated", "legacy", "empty", ""]
+_SharedDict: TypeAlias = dict[str, Any]  # many objects can be shared
 
 class InterpreterError(Exception): ...
 class InterpreterNotFoundError(InterpreterError): ...
 class NotShareableError(ValueError): ...
 
+@disjoint_base
 class CrossInterpreterBufferView:
     def __buffer__(self, flags: int, /) -> memoryview: ...
 
 def new_config(name: _Configs = "isolated", /, **overides: object) -> types.SimpleNamespace: ...
 def create(config: types.SimpleNamespace | _Configs | None = "isolated", *, reqrefs: bool = False) -> int: ...
 def destroy(id: SupportsIndex, *, restrict: bool = False) -> None: ...
-def list_all(*, require_ready: bool) -> list[tuple[int, int]]: ...
-def get_current() -> tuple[int, int]: ...
-def get_main() -> tuple[int, int]: ...
+def list_all(*, require_ready: bool = False) -> list[tuple[int, _Whence]]: ...
+def get_current() -> tuple[int, _Whence]: ...
+def get_main() -> tuple[int, _Whence]: ...
 def is_running(id: SupportsIndex, *, restrict: bool = False) -> bool: ...
 def get_config(id: SupportsIndex, *, restrict: bool = False) -> types.SimpleNamespace: ...
-def whence(id: SupportsIndex) -> int: ...
+def whence(id: SupportsIndex) -> _Whence: ...
 def exec(
-    id: SupportsIndex, code: str | types.CodeType | Callable[[], object], shared: bool | None = None, *, restrict: bool = False
+    id: SupportsIndex, code: str | types.CodeType | Callable[[], object], shared: _SharedDict = {}, *, restrict: bool = False
 ) -> None | types.SimpleNamespace: ...
 def call(
     id: SupportsIndex,
-    callable: Callable[..., object],
-    args: tuple[object, ...] | None = None,
-    kwargs: dict[str, object] | None = None,
+    callable: Callable[..., _R],
+    args: tuple[Any, ...] = (),
+    kwargs: dict[str, Any] = {},
     *,
+    preserve_exc: bool = False,
     restrict: bool = False,
-) -> object: ...
+) -> tuple[_R, types.SimpleNamespace]: ...
 def run_string(
-    id: SupportsIndex, script: str | types.CodeType | Callable[[], object], shared: bool | None = None, *, restrict: bool = False
+    id: SupportsIndex, script: str | types.CodeType | Callable[[], object], shared: _SharedDict = {}, *, restrict: bool = False
 ) -> None: ...
 def run_func(
-    id: SupportsIndex, func: types.CodeType | Callable[[], object], shared: bool | None = None, *, restrict: bool = False
+    id: SupportsIndex, func: types.CodeType | Callable[[], object], shared: _SharedDict = {}, *, restrict: bool = False
 ) -> None: ...
-def set___main___attrs(id: SupportsIndex, updates: Mapping[str, object], *, restrict: bool = False) -> None: ...
+def set___main___attrs(id: SupportsIndex, updates: _SharedDict, *, restrict: bool = False) -> None: ...
 def incref(id: SupportsIndex, *, implieslink: bool = False, restrict: bool = False) -> None: ...
 def decref(id: SupportsIndex, *, restrict: bool = False) -> None: ...
 def is_shareable(obj: object) -> bool: ...
-def capture_exception(exc: BaseException | None = None) -> types.SimpleNamespace: ...
+@overload
+def capture_exception(exc: BaseException) -> types.SimpleNamespace: ...
+@overload
+def capture_exception(exc: None = None) -> types.SimpleNamespace | None: ...
 
+_Whence: TypeAlias = Literal[0, 1, 2, 3, 4, 5]
 WHENCE_UNKNOWN: Final = 0
 WHENCE_RUNTIME: Final = 1
 WHENCE_LEGACY_CAPI: Final = 2
diff --git a/mypy/typeshed/stdlib/_io.pyi b/mypy/typeshed/stdlib/_io.pyi
index c77d75287c25..2d2a60e4dddf 100644
--- a/mypy/typeshed/stdlib/_io.pyi
+++ b/mypy/typeshed/stdlib/_io.pyi
@@ -7,11 +7,14 @@ from io import BufferedIOBase, RawIOBase, TextIOBase, UnsupportedOperation as Un
 from os import _Opener
 from types import TracebackType
 from typing import IO, Any, BinaryIO, Final, Generic, Literal, Protocol, TextIO, TypeVar, overload, type_check_only
-from typing_extensions import Self
+from typing_extensions import Self, disjoint_base
 
 _T = TypeVar("_T")
 
-DEFAULT_BUFFER_SIZE: Final = 8192
+if sys.version_info >= (3, 14):
+    DEFAULT_BUFFER_SIZE: Final = 131072
+else:
+    DEFAULT_BUFFER_SIZE: Final = 8192
 
 open = builtins.open
 
@@ -19,32 +22,62 @@ def open_code(path: str) -> IO[bytes]: ...
 
 BlockingIOError = builtins.BlockingIOError
 
-class _IOBase:
-    def __iter__(self) -> Iterator[bytes]: ...
-    def __next__(self) -> bytes: ...
-    def __enter__(self) -> Self: ...
-    def __exit__(
-        self, exc_type: type[BaseException] | None, exc_val: BaseException | None, exc_tb: TracebackType | None
-    ) -> None: ...
-    def close(self) -> None: ...
-    def fileno(self) -> int: ...
-    def flush(self) -> None: ...
-    def isatty(self) -> bool: ...
-    def readable(self) -> bool: ...
-    read: Callable[..., Any]
-    def readlines(self, hint: int = -1, /) -> list[bytes]: ...
-    def seek(self, offset: int, whence: int = 0, /) -> int: ...
-    def seekable(self) -> bool: ...
-    def tell(self) -> int: ...
-    def truncate(self, size: int | None = None, /) -> int: ...
-    def writable(self) -> bool: ...
-    write: Callable[..., Any]
-    def writelines(self, lines: Iterable[ReadableBuffer], /) -> None: ...
-    def readline(self, size: int | None = -1, /) -> bytes: ...
-    def __del__(self) -> None: ...
-    @property
-    def closed(self) -> bool: ...
-    def _checkClosed(self) -> None: ...  # undocumented
+if sys.version_info >= (3, 12):
+    @disjoint_base
+    class _IOBase:
+        def __iter__(self) -> Iterator[bytes]: ...
+        def __next__(self) -> bytes: ...
+        def __enter__(self) -> Self: ...
+        def __exit__(
+            self, exc_type: type[BaseException] | None, exc_val: BaseException | None, exc_tb: TracebackType | None
+        ) -> None: ...
+        def close(self) -> None: ...
+        def fileno(self) -> int: ...
+        def flush(self) -> None: ...
+        def isatty(self) -> bool: ...
+        def readable(self) -> bool: ...
+        read: Callable[..., Any]
+        def readlines(self, hint: int = -1, /) -> list[bytes]: ...
+        def seek(self, offset: int, whence: int = 0, /) -> int: ...
+        def seekable(self) -> bool: ...
+        def tell(self) -> int: ...
+        def truncate(self, size: int | None = None, /) -> int: ...
+        def writable(self) -> bool: ...
+        write: Callable[..., Any]
+        def writelines(self, lines: Iterable[ReadableBuffer], /) -> None: ...
+        def readline(self, size: int | None = -1, /) -> bytes: ...
+        def __del__(self) -> None: ...
+        @property
+        def closed(self) -> bool: ...
+        def _checkClosed(self) -> None: ...  # undocumented
+
+else:
+    class _IOBase:
+        def __iter__(self) -> Iterator[bytes]: ...
+        def __next__(self) -> bytes: ...
+        def __enter__(self) -> Self: ...
+        def __exit__(
+            self, exc_type: type[BaseException] | None, exc_val: BaseException | None, exc_tb: TracebackType | None
+        ) -> None: ...
+        def close(self) -> None: ...
+        def fileno(self) -> int: ...
+        def flush(self) -> None: ...
+        def isatty(self) -> bool: ...
+        def readable(self) -> bool: ...
+        read: Callable[..., Any]
+        def readlines(self, hint: int = -1, /) -> list[bytes]: ...
+        def seek(self, offset: int, whence: int = 0, /) -> int: ...
+        def seekable(self) -> bool: ...
+        def tell(self) -> int: ...
+        def truncate(self, size: int | None = None, /) -> int: ...
+        def writable(self) -> bool: ...
+        write: Callable[..., Any]
+        def writelines(self, lines: Iterable[ReadableBuffer], /) -> None: ...
+        def readline(self, size: int | None = -1, /) -> bytes: ...
+        def __del__(self) -> None: ...
+        @property
+        def closed(self) -> bool: ...
+        def _checkClosed(self) -> None: ...  # undocumented
 
 class _RawIOBase(_IOBase):
     def readall(self) -> bytes: ...
@@ -62,6 +95,7 @@ class _BufferedIOBase(_IOBase):
     def read(self, size: int | None = -1, /) -> bytes: ...
     def read1(self, size: int = -1, /) -> bytes: ...
 
+@disjoint_base
 class FileIO(RawIOBase, _RawIOBase, BinaryIO):  # type: ignore[misc]  # incompatible definitions of writelines in the base classes
     mode: str
     # The type of "name" equals the argument passed in to the constructor,
@@ -76,6 +110,7 @@ class FileIO(RawIOBase, _RawIOBase, BinaryIO):  # type: ignore[misc]  # incompat
     def seek(self, pos: int, whence: int = 0, /) -> int: ...
     def read(self, size: int | None = -1, /) -> bytes | MaybeNone: ...
 
+@disjoint_base
 class BytesIO(BufferedIOBase, _BufferedIOBase, BinaryIO):  # type: ignore[misc]  # incompatible definitions of methods in the base classes
     def __init__(self, initial_bytes: ReadableBuffer = b"") -> None: ...
     # BytesIO does not contain a "name" field. This workaround is necessary
@@ -88,6 +123,7 @@ class BytesIO(BufferedIOBase, _BufferedIOBase, BinaryIO):  # type: ignore[misc]
     def readlines(self, size: int | None = None, /) -> list[bytes]: ...
     def seek(self, pos: int, whence: int = 0, /) -> int: ...
 
+@type_check_only
 class _BufferedReaderStream(Protocol):
     def read(self, n: int = ..., /) -> bytes: ...
     # Optional: def readall(self) -> bytes: ...
@@ -115,31 +151,51 @@ class _BufferedReaderStream(Protocol):
 
 _BufferedReaderStreamT = TypeVar("_BufferedReaderStreamT", bound=_BufferedReaderStream, default=_BufferedReaderStream)
 
+@disjoint_base
 class BufferedReader(BufferedIOBase, _BufferedIOBase, BinaryIO, Generic[_BufferedReaderStreamT]):  # type: ignore[misc]  # incompatible definitions of methods in the base classes
     raw: _BufferedReaderStreamT
-    def __init__(self, raw: _BufferedReaderStreamT, buffer_size: int = 8192) -> None: ...
+    if sys.version_info >= (3, 14):
+        def __init__(self, raw: _BufferedReaderStreamT, buffer_size: int = 131072) -> None: ...
+    else:
+        def __init__(self, raw: _BufferedReaderStreamT, buffer_size: int = 8192) -> None: ...
+
     def peek(self, size: int = 0, /) -> bytes: ...
     def seek(self, target: int, whence: int = 0, /) -> int: ...
     def truncate(self, pos: int | None = None, /) -> int: ...
 
+@disjoint_base
 class BufferedWriter(BufferedIOBase, _BufferedIOBase, BinaryIO):  # type: ignore[misc]  # incompatible definitions of writelines in the base classes
     raw: RawIOBase
-    def __init__(self, raw: RawIOBase, buffer_size: int = 8192) -> None: ...
+    if sys.version_info >= (3, 14):
+        def __init__(self, raw: RawIOBase, buffer_size: int = 131072) -> None: ...
+    else:
+        def __init__(self, raw: RawIOBase, buffer_size: int = 8192) -> None: ...
+
     def write(self, buffer: ReadableBuffer, /) -> int: ...
     def seek(self, target: int, whence: int = 0, /) -> int: ...
     def truncate(self, pos: int | None = None, /) -> int: ...
 
+@disjoint_base
 class BufferedRandom(BufferedIOBase, _BufferedIOBase, BinaryIO):  # type: ignore[misc]  # incompatible definitions of methods in the base classes
     mode: str
     name: Any
     raw: RawIOBase
-    def __init__(self, raw: RawIOBase, buffer_size: int = 8192) -> None: ...
+    if sys.version_info >= (3, 14):
+        def __init__(self, raw: RawIOBase, buffer_size: int = 131072) -> None: ...
+    else:
+        def __init__(self, raw: RawIOBase, buffer_size: int = 8192) -> None: ...
+
     def seek(self, target: int, whence: int = 0, /) -> int: ...  # stubtest needs this
     def peek(self, size: int = 0, /) -> bytes: ...
     def truncate(self, pos: int | None = None, /) -> int: ...
 
+@disjoint_base
 class BufferedRWPair(BufferedIOBase, _BufferedIOBase, Generic[_BufferedReaderStreamT]):
-    def __init__(self, reader: _BufferedReaderStreamT, writer: RawIOBase, buffer_size: int = 8192, /) -> None: ...
+    if sys.version_info >= (3, 14):
+        def __init__(self, reader: _BufferedReaderStreamT, writer: RawIOBase, buffer_size: int = 131072, /) -> None: ...
+    else:
+        def __init__(self, reader: _BufferedReaderStreamT, writer: RawIOBase, buffer_size: int = 8192, /) -> None: ...
+
     def peek(self, size: int = 0, /) -> bytes: ...
 
 class _TextIOBase(_IOBase):
@@ -180,6 +236,7 @@ class _WrappedBuffer(Protocol):
 
 _BufferT_co = TypeVar("_BufferT_co", bound=_WrappedBuffer, default=_WrappedBuffer, covariant=True)
 
+@disjoint_base
 class TextIOWrapper(TextIOBase, _TextIOBase, TextIO, Generic[_BufferT_co]):  # type: ignore[misc]  # incompatible definitions of write in the base classes
     def __init__(
         self,
@@ -214,6 +271,7 @@ class TextIOWrapper(TextIOBase, _TextIOBase, TextIO, Generic[_BufferT_co]):  # t
     def seek(self, cookie: int, whence: int = 0, /) -> int: ...
     def truncate(self, pos: int | None = None, /) -> int: ...
 
+@disjoint_base
 class StringIO(TextIOBase, _TextIOBase, TextIO):  # type: ignore[misc]  # incompatible definitions of write in the base classes
     def __init__(self, initial_value: str | None = "", newline: str | None = "\n") -> None: ...
     # StringIO does not contain a "name" field. This workaround is necessary
@@ -226,6 +284,7 @@ class StringIO(TextIOBase, _TextIOBase, TextIO):  # type: ignore[misc]  # incomp
     def seek(self, pos: int, whence: int = 0, /) -> int: ...
     def truncate(self, pos: int | None = None, /) -> int: ...
 
+@disjoint_base
 class IncrementalNewlineDecoder:
     def __init__(self, decoder: codecs.IncrementalDecoder | None, translate: bool, errors: str = "strict") -> None: ...
     def decode(self, input: ReadableBuffer | str, final: bool = False) -> str: ...
diff --git a/mypy/typeshed/stdlib/_json.pyi b/mypy/typeshed/stdlib/_json.pyi
index 5296b8e62a02..4a77e5be594a 100644
--- a/mypy/typeshed/stdlib/_json.pyi
+++ b/mypy/typeshed/stdlib/_json.pyi
@@ -11,7 +11,7 @@ class make_encoder:
     @property
     def key_separator(self) -> str: ...
     @property
-    def indent(self) -> int | None: ...
+    def indent(self) -> str | None: ...
     @property
     def markers(self) -> dict[int, Any] | None: ...
     @property
@@ -25,7 +25,7 @@ class make_encoder:
         markers: dict[int, Any] | None,
         default: Callable[[Any], Any],
         encoder: Callable[[str], str],
-        indent: int | None,
+        indent: str | None,
         key_separator: str,
         item_separator: str,
         sort_keys: bool,
@@ -48,4 +48,4 @@ class make_scanner:
 
 def encode_basestring(s: str, /) -> str: ...
 def encode_basestring_ascii(s: str, /) -> str: ...
-def scanstring(string: str, end: int, strict: bool = ...) -> tuple[str, int]: ...
+def scanstring(string: str, end: int, strict: bool = True) -> tuple[str, int]: ...
diff --git a/mypy/typeshed/stdlib/_lsprof.pyi b/mypy/typeshed/stdlib/_lsprof.pyi
index 8a6934162c92..4f6d98b8ffb6 100644
--- a/mypy/typeshed/stdlib/_lsprof.pyi
+++ b/mypy/typeshed/stdlib/_lsprof.pyi
@@ -3,7 +3,9 @@ from _typeshed import structseq
 from collections.abc import Callable
 from types import CodeType
 from typing import Any, Final, final
+from typing_extensions import disjoint_base
 
+@disjoint_base
 class Profiler:
     def __init__(
         self, timer: Callable[[], float] | None = None, timeunit: float = 0.0, subcalls: bool = True, builtins: bool = True
diff --git a/mypy/typeshed/stdlib/_lzma.pyi b/mypy/typeshed/stdlib/_lzma.pyi
index 1a27c7428e8e..b38dce9faded 100644
--- a/mypy/typeshed/stdlib/_lzma.pyi
+++ b/mypy/typeshed/stdlib/_lzma.pyi
@@ -16,7 +16,7 @@ CHECK_CRC64: Final = 4
 CHECK_SHA256: Final = 10
 CHECK_ID_MAX: Final = 15
 CHECK_UNKNOWN: Final = 16
-FILTER_LZMA1: int  # v big number
+FILTER_LZMA1: Final[int]  # v big number
 FILTER_LZMA2: Final = 33
 FILTER_DELTA: Final = 3
 FILTER_X86: Final = 4
@@ -33,14 +33,14 @@ MF_BT4: Final = 20
 MODE_FAST: Final = 1
 MODE_NORMAL: Final = 2
 PRESET_DEFAULT: Final = 6
-PRESET_EXTREME: int  # v big number
+PRESET_EXTREME: Final[int]  # v big number
 
 @final
 class LZMADecompressor:
     if sys.version_info >= (3, 12):
-        def __new__(cls, format: int | None = ..., memlimit: int | None = ..., filters: _FilterChain | None = ...) -> Self: ...
+        def __new__(cls, format: int = 0, memlimit: int | None = None, filters: _FilterChain | None = None) -> Self: ...
     else:
-        def __init__(self, format: int | None = ..., memlimit: int | None = ..., filters: _FilterChain | None = ...) -> None: ...
+        def __init__(self, format: int = 0, memlimit: int | None = None, filters: _FilterChain | None = None) -> None: ...
 
     def decompress(self, data: ReadableBuffer, max_length: int = -1) -> bytes: ...
     @property
@@ -56,11 +56,11 @@ class LZMADecompressor:
 class LZMACompressor:
     if sys.version_info >= (3, 12):
         def __new__(
-            cls, format: int | None = ..., check: int = ..., preset: int | None = ..., filters: _FilterChain | None = ...
+            cls, format: int = 1, check: int = -1, preset: int | None = None, filters: _FilterChain | None = None
         ) -> Self: ...
     else:
         def __init__(
-            self, format: int | None = ..., check: int = ..., preset: int | None = ..., filters: _FilterChain | None = ...
+            self, format: int = 1, check: int = -1, preset: int | None = None, filters: _FilterChain | None = None
         ) -> None: ...
 
     def compress(self, data: ReadableBuffer, /) -> bytes: ...
diff --git a/mypy/typeshed/stdlib/_markupbase.pyi b/mypy/typeshed/stdlib/_markupbase.pyi
index 62bad25e5ccc..597bd09b700b 100644
--- a/mypy/typeshed/stdlib/_markupbase.pyi
+++ b/mypy/typeshed/stdlib/_markupbase.pyi
@@ -5,9 +5,9 @@ class ParserBase:
     def reset(self) -> None: ...
     def getpos(self) -> tuple[int, int]: ...
     def unknown_decl(self, data: str) -> None: ...
-    def parse_comment(self, i: int, report: int = 1) -> int: ...  # undocumented
+    def parse_comment(self, i: int, report: bool = True) -> int: ...  # undocumented
     def parse_declaration(self, i: int) -> int: ...  # undocumented
-    def parse_marked_section(self, i: int, report: int = 1) -> int: ...  # undocumented
+    def parse_marked_section(self, i: int, report: bool = True) -> int: ...  # undocumented
     def updatepos(self, i: int, j: int) -> int: ...  # undocumented
     if sys.version_info < (3, 10):
         # Removed from ParserBase: https://bugs.python.org/issue31844
diff --git a/mypy/typeshed/stdlib/_msi.pyi b/mypy/typeshed/stdlib/_msi.pyi
index 779fda3b67fe..edceed51bf9d 100644
--- a/mypy/typeshed/stdlib/_msi.pyi
+++ b/mypy/typeshed/stdlib/_msi.pyi
@@ -1,8 +1,10 @@
 import sys
+from typing import Final, type_check_only
 
 if sys.platform == "win32":
     class MSIError(Exception): ...
     # Actual typename View, not exposed by the implementation
+    @type_check_only
     class _View:
         def Execute(self, params: _Record | None = ...) -> None: ...
         def GetColumnInfo(self, kind: int) -> _Record: ...
@@ -14,6 +16,7 @@ if sys.platform == "win32":
         __init__: None  # type: ignore[assignment]
 
     # Actual typename SummaryInformation, not exposed by the implementation
+    @type_check_only
     class _SummaryInformation:
         def GetProperty(self, field: int) -> int | bytes | None: ...
         def GetPropertyCount(self) -> int: ...
@@ -24,6 +27,7 @@ if sys.platform == "win32":
         __init__: None  # type: ignore[assignment]
 
     # Actual typename Database, not exposed by the implementation
+    @type_check_only
     class _Database:
         def OpenView(self, sql: str) -> _View: ...
         def Commit(self) -> None: ...
@@ -34,6 +38,7 @@ if sys.platform == "win32":
         __init__: None  # type: ignore[assignment]
 
     # Actual typename Record, not exposed by the implementation
+    @type_check_only
     class _Record:
         def GetFieldCount(self) -> int: ...
         def GetInteger(self, field: int) -> int: ...
@@ -51,42 +56,42 @@ if sys.platform == "win32":
     def OpenDatabase(path: str, persist: int, /) -> _Database: ...
     def CreateRecord(count: int, /) -> _Record: ...
 
-    MSICOLINFO_NAMES: int
-    MSICOLINFO_TYPES: int
-    MSIDBOPEN_CREATE: int
-    MSIDBOPEN_CREATEDIRECT: int
-    MSIDBOPEN_DIRECT: int
-    MSIDBOPEN_PATCHFILE: int
-    MSIDBOPEN_READONLY: int
-    MSIDBOPEN_TRANSACT: int
-    MSIMODIFY_ASSIGN: int
-    MSIMODIFY_DELETE: int
-    MSIMODIFY_INSERT: int
-    MSIMODIFY_INSERT_TEMPORARY: int
-    MSIMODIFY_MERGE: int
-    MSIMODIFY_REFRESH: int
-    MSIMODIFY_REPLACE: int
-    MSIMODIFY_SEEK: int
-    MSIMODIFY_UPDATE: int
-    MSIMODIFY_VALIDATE: int
-    MSIMODIFY_VALIDATE_DELETE: int
-    MSIMODIFY_VALIDATE_FIELD: int
-    MSIMODIFY_VALIDATE_NEW: int
+    MSICOLINFO_NAMES: Final[int]
+    MSICOLINFO_TYPES: Final[int]
+    MSIDBOPEN_CREATE: Final[int]
+    MSIDBOPEN_CREATEDIRECT: Final[int]
+    MSIDBOPEN_DIRECT: Final[int]
+    MSIDBOPEN_PATCHFILE: Final[int]
+    MSIDBOPEN_READONLY: Final[int]
+    MSIDBOPEN_TRANSACT: Final[int]
+    MSIMODIFY_ASSIGN: Final[int]
+    MSIMODIFY_DELETE: Final[int]
+    MSIMODIFY_INSERT: Final[int]
+    MSIMODIFY_INSERT_TEMPORARY: Final[int]
+    MSIMODIFY_MERGE: Final[int]
+    MSIMODIFY_REFRESH: Final[int]
+    MSIMODIFY_REPLACE: Final[int]
+    MSIMODIFY_SEEK: Final[int]
+    MSIMODIFY_UPDATE: Final[int]
+    MSIMODIFY_VALIDATE: Final[int]
+    MSIMODIFY_VALIDATE_DELETE: Final[int]
+    MSIMODIFY_VALIDATE_FIELD: Final[int]
+    MSIMODIFY_VALIDATE_NEW: Final[int]
 
-    PID_APPNAME: int
-    PID_AUTHOR: int
-    PID_CHARCOUNT: int
-    PID_CODEPAGE: int
-    PID_COMMENTS: int
-    PID_CREATE_DTM: int
-    PID_KEYWORDS: int
-    PID_LASTAUTHOR: int
-    PID_LASTPRINTED: int
-    PID_LASTSAVE_DTM: int
-    PID_PAGECOUNT: int
-    PID_REVNUMBER: int
-    PID_SECURITY: int
-    PID_SUBJECT: int
-    PID_TEMPLATE: int
-    PID_TITLE: int
-    PID_WORDCOUNT: int
+    PID_APPNAME: Final[int]
+    PID_AUTHOR: Final[int]
+    PID_CHARCOUNT: Final[int]
+    PID_CODEPAGE: Final[int]
+    PID_COMMENTS: Final[int]
+    PID_CREATE_DTM: Final[int]
+    PID_KEYWORDS: Final[int]
+    PID_LASTAUTHOR: Final[int]
+    PID_LASTPRINTED: Final[int]
+    PID_LASTSAVE_DTM: Final[int]
+    PID_PAGECOUNT: Final[int]
+    PID_REVNUMBER: Final[int]
+    PID_SECURITY: Final[int]
+    PID_SUBJECT: Final[int]
+    PID_TEMPLATE: Final[int]
+    PID_TITLE: Final[int]
+    PID_WORDCOUNT: Final[int]
diff --git a/mypy/typeshed/stdlib/_multibytecodec.pyi b/mypy/typeshed/stdlib/_multibytecodec.pyi
index 7e408f2aa30e..abe58cb64f31 100644
--- a/mypy/typeshed/stdlib/_multibytecodec.pyi
+++ b/mypy/typeshed/stdlib/_multibytecodec.pyi
@@ -2,6 +2,7 @@ from _typeshed import ReadableBuffer
 from codecs import _ReadableStream, _WritableStream
 from collections.abc import Iterable
 from typing import final, type_check_only
+from typing_extensions import disjoint_base
 
 # This class is not exposed. It calls itself _multibytecodec.MultibyteCodec.
 @final
@@ -10,6 +11,7 @@ class _MultibyteCodec:
     def decode(self, input: ReadableBuffer, errors: str | None = None) -> str: ...
     def encode(self, input: str, errors: str | None = None) -> bytes: ...
 
+@disjoint_base
 class MultibyteIncrementalDecoder:
     errors: str
     def __init__(self, errors: str = "strict") -> None: ...
@@ -18,6 +20,7 @@ class MultibyteIncrementalDecoder:
     def reset(self) -> None: ...
     def setstate(self, state: tuple[bytes, int], /) -> None: ...
 
+@disjoint_base
 class MultibyteIncrementalEncoder:
     errors: str
     def __init__(self, errors: str = "strict") -> None: ...
@@ -26,6 +29,7 @@ class MultibyteIncrementalEncoder:
     def reset(self) -> None: ...
     def setstate(self, state: int, /) -> None: ...
 
+@disjoint_base
 class MultibyteStreamReader:
     errors: str
     stream: _ReadableStream
@@ -35,6 +39,7 @@ class MultibyteStreamReader:
     def readlines(self, sizehintobj: int | None = None, /) -> list[str]: ...
     def reset(self) -> None: ...
 
+@disjoint_base
 class MultibyteStreamWriter:
     errors: str
     stream: _WritableStream
diff --git a/mypy/typeshed/stdlib/_operator.pyi b/mypy/typeshed/stdlib/_operator.pyi
index 967215d8fa21..cb1c1bcfc4aa 100644
--- a/mypy/typeshed/stdlib/_operator.pyi
+++ b/mypy/typeshed/stdlib/_operator.pyi
@@ -2,7 +2,7 @@ import sys
 from _typeshed import SupportsGetItem
 from collections.abc import Callable, Container, Iterable, MutableMapping, MutableSequence, Sequence
 from operator import attrgetter as attrgetter, itemgetter as itemgetter, methodcaller as methodcaller
-from typing import Any, AnyStr, Protocol, SupportsAbs, SupportsIndex, TypeVar, overload
+from typing import Any, AnyStr, Protocol, SupportsAbs, SupportsIndex, TypeVar, overload, type_check_only
 from typing_extensions import ParamSpec, TypeAlias, TypeIs
 
 _R = TypeVar("_R")
@@ -16,26 +16,33 @@ _P = ParamSpec("_P")
 # operators can be overloaded to return an arbitrary object. For example,
 # the numpy.array comparison dunders return another numpy.array.
 
+@type_check_only
 class _SupportsDunderLT(Protocol):
     def __lt__(self, other: Any, /) -> Any: ...
 
+@type_check_only
 class _SupportsDunderGT(Protocol):
     def __gt__(self, other: Any, /) -> Any: ...
 
+@type_check_only
 class _SupportsDunderLE(Protocol):
     def __le__(self, other: Any, /) -> Any: ...
 
+@type_check_only
 class _SupportsDunderGE(Protocol):
     def __ge__(self, other: Any, /) -> Any: ...
 
 _SupportsComparison: TypeAlias = _SupportsDunderLE | _SupportsDunderGE | _SupportsDunderGT | _SupportsDunderLT
 
+@type_check_only
 class _SupportsInversion(Protocol[_T_co]):
     def __invert__(self) -> _T_co: ...
 
+@type_check_only
 class _SupportsNeg(Protocol[_T_co]):
     def __neg__(self) -> _T_co: ...
 
+@type_check_only
 class _SupportsPos(Protocol[_T_co]):
     def __pos__(self) -> _T_co: ...
 
diff --git a/mypy/typeshed/stdlib/_pickle.pyi b/mypy/typeshed/stdlib/_pickle.pyi
index 8e8afb600efa..544f787172d6 100644
--- a/mypy/typeshed/stdlib/_pickle.pyi
+++ b/mypy/typeshed/stdlib/_pickle.pyi
@@ -2,8 +2,9 @@ from _typeshed import ReadableBuffer, SupportsWrite
 from collections.abc import Callable, Iterable, Iterator, Mapping
 from pickle import PickleBuffer as PickleBuffer
 from typing import Any, Protocol, type_check_only
-from typing_extensions import TypeAlias
+from typing_extensions import TypeAlias, disjoint_base
 
+@type_check_only
 class _ReadableFileobj(Protocol):
     def read(self, n: int, /) -> bytes: ...
     def readline(self) -> bytes: ...
@@ -56,6 +57,7 @@ class PicklerMemoProxy:
     def clear(self, /) -> None: ...
     def copy(self, /) -> dict[int, tuple[int, Any]]: ...
 
+@disjoint_base
 class Pickler:
     fast: bool
     dispatch_table: Mapping[type, Callable[[Any], _ReducedType]]
@@ -83,6 +85,7 @@ class UnpicklerMemoProxy:
     def clear(self, /) -> None: ...
     def copy(self, /) -> dict[int, tuple[int, Any]]: ...
 
+@disjoint_base
 class Unpickler:
     def __init__(
         self,
diff --git a/mypy/typeshed/stdlib/_queue.pyi b/mypy/typeshed/stdlib/_queue.pyi
index f98397b132ab..edd484a9a71a 100644
--- a/mypy/typeshed/stdlib/_queue.pyi
+++ b/mypy/typeshed/stdlib/_queue.pyi
@@ -1,10 +1,12 @@
 from types import GenericAlias
 from typing import Any, Generic, TypeVar
+from typing_extensions import disjoint_base
 
 _T = TypeVar("_T")
 
 class Empty(Exception): ...
 
+@disjoint_base
 class SimpleQueue(Generic[_T]):
     def __init__(self) -> None: ...
     def empty(self) -> bool: ...
diff --git a/mypy/typeshed/stdlib/_random.pyi b/mypy/typeshed/stdlib/_random.pyi
index 4082344ade8e..ac00fdfb7272 100644
--- a/mypy/typeshed/stdlib/_random.pyi
+++ b/mypy/typeshed/stdlib/_random.pyi
@@ -1,10 +1,16 @@
-from typing_extensions import TypeAlias
+import sys
+from typing_extensions import Self, TypeAlias, disjoint_base
 
 # Actually Tuple[(int,) * 625]
 _State: TypeAlias = tuple[int, ...]
 
+@disjoint_base
 class Random:
-    def __init__(self, seed: object = ...) -> None: ...
+    if sys.version_info >= (3, 10):
+        def __init__(self, seed: object = ..., /) -> None: ...
+    else:
+        def __new__(self, seed: object = ..., /) -> Self: ...
+
     def seed(self, n: object = None, /) -> None: ...
     def getstate(self) -> _State: ...
     def setstate(self, state: _State, /) -> None: ...
diff --git a/mypy/typeshed/stdlib/_socket.pyi b/mypy/typeshed/stdlib/_socket.pyi
index 06a8a2ba5fa0..cdad886b3415 100644
--- a/mypy/typeshed/stdlib/_socket.pyi
+++ b/mypy/typeshed/stdlib/_socket.pyi
@@ -2,8 +2,8 @@ import sys
 from _typeshed import ReadableBuffer, WriteableBuffer
 from collections.abc import Iterable
 from socket import error as error, gaierror as gaierror, herror as herror, timeout as timeout
-from typing import Any, SupportsIndex, overload
-from typing_extensions import CapsuleType, TypeAlias
+from typing import Any, Final, SupportsIndex, overload
+from typing_extensions import CapsuleType, TypeAlias, disjoint_base
 
 _CMSG: TypeAlias = tuple[int, int, bytes]
 _CMSGArg: TypeAlias = tuple[int, int, ReadableBuffer]
@@ -19,23 +19,23 @@ _RetAddress: TypeAlias = Any
 # https://docs.python.org/3/library/socket.html#constants
 
 if sys.platform != "win32":
-    AF_UNIX: int
+    AF_UNIX: Final[int]
 
-AF_INET: int
-AF_INET6: int
+AF_INET: Final[int]
+AF_INET6: Final[int]
 
-AF_UNSPEC: int
+AF_UNSPEC: Final[int]
 
-SOCK_STREAM: int
-SOCK_DGRAM: int
-SOCK_RAW: int
-SOCK_RDM: int
-SOCK_SEQPACKET: int
+SOCK_STREAM: Final[int]
+SOCK_DGRAM: Final[int]
+SOCK_RAW: Final[int]
+SOCK_RDM: Final[int]
+SOCK_SEQPACKET: Final[int]
 
 if sys.platform == "linux":
     # Availability: Linux >= 2.6.27
-    SOCK_CLOEXEC: int
-    SOCK_NONBLOCK: int
+    SOCK_CLOEXEC: Final[int]
+    SOCK_NONBLOCK: Final[int]
 
 # --------------------
 # Many constants of these forms, documented in the Unix documentation on
@@ -56,328 +56,329 @@ if sys.platform == "linux":
 # TCP_*
 # --------------------
 
-SO_ACCEPTCONN: int
-SO_BROADCAST: int
-SO_DEBUG: int
-SO_DONTROUTE: int
-SO_ERROR: int
-SO_KEEPALIVE: int
-SO_LINGER: int
-SO_OOBINLINE: int
-SO_RCVBUF: int
-SO_RCVLOWAT: int
-SO_RCVTIMEO: int
-SO_REUSEADDR: int
-SO_SNDBUF: int
-SO_SNDLOWAT: int
-SO_SNDTIMEO: int
-SO_TYPE: int
+SO_ACCEPTCONN: Final[int]
+SO_BROADCAST: Final[int]
+SO_DEBUG: Final[int]
+SO_DONTROUTE: Final[int]
+SO_ERROR: Final[int]
+SO_KEEPALIVE: Final[int]
+SO_LINGER: Final[int]
+SO_OOBINLINE: Final[int]
+SO_RCVBUF: Final[int]
+SO_RCVLOWAT: Final[int]
+SO_RCVTIMEO: Final[int]
+SO_REUSEADDR: Final[int]
+SO_SNDBUF: Final[int]
+SO_SNDLOWAT: Final[int]
+SO_SNDTIMEO: Final[int]
+SO_TYPE: Final[int]
 if sys.platform != "linux":
-    SO_USELOOPBACK: int
+    SO_USELOOPBACK: Final[int]
 if sys.platform == "win32":
-    SO_EXCLUSIVEADDRUSE: int
+    SO_EXCLUSIVEADDRUSE: Final[int]
 if sys.platform != "win32":
-    SO_REUSEPORT: int
+    SO_REUSEPORT: Final[int]
     if sys.platform != "darwin" or sys.version_info >= (3, 13):
-        SO_BINDTODEVICE: int
+        SO_BINDTODEVICE: Final[int]
 
 if sys.platform != "win32" and sys.platform != "darwin":
-    SO_DOMAIN: int
-    SO_MARK: int
-    SO_PASSCRED: int
-    SO_PASSSEC: int
-    SO_PEERCRED: int
-    SO_PEERSEC: int
-    SO_PRIORITY: int
-    SO_PROTOCOL: int
+    SO_DOMAIN: Final[int]
+    SO_MARK: Final[int]
+    SO_PASSCRED: Final[int]
+    SO_PASSSEC: Final[int]
+    SO_PEERCRED: Final[int]
+    SO_PEERSEC: Final[int]
+    SO_PRIORITY: Final[int]
+    SO_PROTOCOL: Final[int]
 if sys.platform != "win32" and sys.platform != "darwin" and sys.platform != "linux":
-    SO_SETFIB: int
+    SO_SETFIB: Final[int]
 if sys.platform == "linux" and sys.version_info >= (3, 13):
-    SO_BINDTOIFINDEX: int
+    SO_BINDTOIFINDEX: Final[int]
 
-SOMAXCONN: int
+SOMAXCONN: Final[int]
 
-MSG_CTRUNC: int
-MSG_DONTROUTE: int
-MSG_OOB: int
-MSG_PEEK: int
-MSG_TRUNC: int
-MSG_WAITALL: int
+MSG_CTRUNC: Final[int]
+MSG_DONTROUTE: Final[int]
+MSG_OOB: Final[int]
+MSG_PEEK: Final[int]
+MSG_TRUNC: Final[int]
+MSG_WAITALL: Final[int]
 if sys.platform != "win32":
-    MSG_DONTWAIT: int
-    MSG_EOR: int
-    MSG_NOSIGNAL: int  # Sometimes this exists on darwin, sometimes not
+    MSG_DONTWAIT: Final[int]
+    MSG_EOR: Final[int]
+    MSG_NOSIGNAL: Final[int]  # Sometimes this exists on darwin, sometimes not
 if sys.platform != "darwin":
-    MSG_ERRQUEUE: int
+    MSG_ERRQUEUE: Final[int]
 if sys.platform == "win32":
-    MSG_BCAST: int
-    MSG_MCAST: int
+    MSG_BCAST: Final[int]
+    MSG_MCAST: Final[int]
 if sys.platform != "win32" and sys.platform != "darwin":
-    MSG_CMSG_CLOEXEC: int
-    MSG_CONFIRM: int
-    MSG_FASTOPEN: int
-    MSG_MORE: int
+    MSG_CMSG_CLOEXEC: Final[int]
+    MSG_CONFIRM: Final[int]
+    MSG_FASTOPEN: Final[int]
+    MSG_MORE: Final[int]
 if sys.platform != "win32" and sys.platform != "linux":
-    MSG_EOF: int
+    MSG_EOF: Final[int]
 if sys.platform != "win32" and sys.platform != "linux" and sys.platform != "darwin":
-    MSG_NOTIFICATION: int
-    MSG_BTAG: int  # Not FreeBSD either
-    MSG_ETAG: int  # Not FreeBSD either
-
-SOL_IP: int
-SOL_SOCKET: int
-SOL_TCP: int
-SOL_UDP: int
+    MSG_NOTIFICATION: Final[int]
+    MSG_BTAG: Final[int]  # Not FreeBSD either
+    MSG_ETAG: Final[int]  # Not FreeBSD either
+
+SOL_IP: Final[int]
+SOL_SOCKET: Final[int]
+SOL_TCP: Final[int]
+SOL_UDP: Final[int]
 if sys.platform != "win32" and sys.platform != "darwin":
     # Defined in socket.h for Linux, but these aren't always present for
     # some reason.
-    SOL_ATALK: int
-    SOL_AX25: int
-    SOL_HCI: int
-    SOL_IPX: int
-    SOL_NETROM: int
-    SOL_ROSE: int
+    SOL_ATALK: Final[int]
+    SOL_AX25: Final[int]
+    SOL_HCI: Final[int]
+    SOL_IPX: Final[int]
+    SOL_NETROM: Final[int]
+    SOL_ROSE: Final[int]
 
 if sys.platform != "win32":
-    SCM_RIGHTS: int
+    SCM_RIGHTS: Final[int]
 if sys.platform != "win32" and sys.platform != "darwin":
-    SCM_CREDENTIALS: int
+    SCM_CREDENTIALS: Final[int]
 if sys.platform != "win32" and sys.platform != "linux":
-    SCM_CREDS: int
-
-IPPROTO_ICMP: int
-IPPROTO_IP: int
-IPPROTO_RAW: int
-IPPROTO_TCP: int
-IPPROTO_UDP: int
-IPPROTO_AH: int
-IPPROTO_DSTOPTS: int
-IPPROTO_EGP: int
-IPPROTO_ESP: int
-IPPROTO_FRAGMENT: int
-IPPROTO_HOPOPTS: int
-IPPROTO_ICMPV6: int
-IPPROTO_IDP: int
-IPPROTO_IGMP: int
-IPPROTO_IPV6: int
-IPPROTO_NONE: int
-IPPROTO_PIM: int
-IPPROTO_PUP: int
-IPPROTO_ROUTING: int
-IPPROTO_SCTP: int
+    SCM_CREDS: Final[int]
+
+IPPROTO_ICMP: Final[int]
+IPPROTO_IP: Final[int]
+IPPROTO_RAW: Final[int]
+IPPROTO_TCP: Final[int]
+IPPROTO_UDP: Final[int]
+IPPROTO_AH: Final[int]
+IPPROTO_DSTOPTS: Final[int]
+IPPROTO_EGP: Final[int]
+IPPROTO_ESP: Final[int]
+IPPROTO_FRAGMENT: Final[int]
+IPPROTO_HOPOPTS: Final[int]
+IPPROTO_ICMPV6: Final[int]
+IPPROTO_IDP: Final[int]
+IPPROTO_IGMP: Final[int]
+IPPROTO_IPV6: Final[int]
+IPPROTO_NONE: Final[int]
+IPPROTO_PIM: Final[int]
+IPPROTO_PUP: Final[int]
+IPPROTO_ROUTING: Final[int]
+IPPROTO_SCTP: Final[int]
 if sys.platform != "linux":
-    IPPROTO_GGP: int
-    IPPROTO_IPV4: int
-    IPPROTO_MAX: int
-    IPPROTO_ND: int
+    IPPROTO_GGP: Final[int]
+    IPPROTO_IPV4: Final[int]
+    IPPROTO_MAX: Final[int]
+    IPPROTO_ND: Final[int]
 if sys.platform == "win32":
-    IPPROTO_CBT: int
-    IPPROTO_ICLFXBM: int
-    IPPROTO_IGP: int
-    IPPROTO_L2TP: int
-    IPPROTO_PGM: int
-    IPPROTO_RDP: int
-    IPPROTO_ST: int
+    IPPROTO_CBT: Final[int]
+    IPPROTO_ICLFXBM: Final[int]
+    IPPROTO_IGP: Final[int]
+    IPPROTO_L2TP: Final[int]
+    IPPROTO_PGM: Final[int]
+    IPPROTO_RDP: Final[int]
+    IPPROTO_ST: Final[int]
 if sys.platform != "win32":
-    IPPROTO_GRE: int
-    IPPROTO_IPIP: int
-    IPPROTO_RSVP: int
-    IPPROTO_TP: int
+    IPPROTO_GRE: Final[int]
+    IPPROTO_IPIP: Final[int]
+    IPPROTO_RSVP: Final[int]
+    IPPROTO_TP: Final[int]
 if sys.platform != "win32" and sys.platform != "linux":
-    IPPROTO_EON: int
-    IPPROTO_HELLO: int
-    IPPROTO_IPCOMP: int
-    IPPROTO_XTP: int
+    IPPROTO_EON: Final[int]
+    IPPROTO_HELLO: Final[int]
+    IPPROTO_IPCOMP: Final[int]
+    IPPROTO_XTP: Final[int]
 if sys.platform != "win32" and sys.platform != "darwin" and sys.platform != "linux":
-    IPPROTO_BIP: int  # Not FreeBSD either
-    IPPROTO_MOBILE: int  # Not FreeBSD either
-    IPPROTO_VRRP: int  # Not FreeBSD either
+    IPPROTO_BIP: Final[int]  # Not FreeBSD either
+    IPPROTO_MOBILE: Final[int]  # Not FreeBSD either
+    IPPROTO_VRRP: Final[int]  # Not FreeBSD either
 if sys.platform == "linux":
     # Availability: Linux >= 2.6.20, FreeBSD >= 10.1
-    IPPROTO_UDPLITE: int
+    IPPROTO_UDPLITE: Final[int]
 if sys.version_info >= (3, 10) and sys.platform == "linux":
-    IPPROTO_MPTCP: int
-
-IPPORT_RESERVED: int
-IPPORT_USERRESERVED: int
-
-INADDR_ALLHOSTS_GROUP: int
-INADDR_ANY: int
-INADDR_BROADCAST: int
-INADDR_LOOPBACK: int
-INADDR_MAX_LOCAL_GROUP: int
-INADDR_NONE: int
-INADDR_UNSPEC_GROUP: int
-
-IP_ADD_MEMBERSHIP: int
-IP_DROP_MEMBERSHIP: int
-IP_HDRINCL: int
-IP_MULTICAST_IF: int
-IP_MULTICAST_LOOP: int
-IP_MULTICAST_TTL: int
-IP_OPTIONS: int
+    IPPROTO_MPTCP: Final[int]
+
+IPPORT_RESERVED: Final[int]
+IPPORT_USERRESERVED: Final[int]
+
+INADDR_ALLHOSTS_GROUP: Final[int]
+INADDR_ANY: Final[int]
+INADDR_BROADCAST: Final[int]
+INADDR_LOOPBACK: Final[int]
+INADDR_MAX_LOCAL_GROUP: Final[int]
+INADDR_NONE: Final[int]
+INADDR_UNSPEC_GROUP: Final[int]
+
+IP_ADD_MEMBERSHIP: Final[int]
+IP_DROP_MEMBERSHIP: Final[int]
+IP_HDRINCL: Final[int]
+IP_MULTICAST_IF: Final[int]
+IP_MULTICAST_LOOP: Final[int]
+IP_MULTICAST_TTL: Final[int]
+IP_OPTIONS: Final[int]
 if sys.platform != "linux":
-    IP_RECVDSTADDR: int
+    IP_RECVDSTADDR: Final[int]
 if sys.version_info >= (3, 10):
-    IP_RECVTOS: int
-IP_TOS: int
-IP_TTL: int
+    IP_RECVTOS: Final[int]
+IP_TOS: Final[int]
+IP_TTL: Final[int]
 if sys.platform != "win32":
-    IP_DEFAULT_MULTICAST_LOOP: int
-    IP_DEFAULT_MULTICAST_TTL: int
-    IP_MAX_MEMBERSHIPS: int
-    IP_RECVOPTS: int
-    IP_RECVRETOPTS: int
-    IP_RETOPTS: int
+    IP_DEFAULT_MULTICAST_LOOP: Final[int]
+    IP_DEFAULT_MULTICAST_TTL: Final[int]
+    IP_MAX_MEMBERSHIPS: Final[int]
+    IP_RECVOPTS: Final[int]
+    IP_RECVRETOPTS: Final[int]
+    IP_RETOPTS: Final[int]
+if sys.version_info >= (3, 13) and sys.platform == "linux":
+    CAN_RAW_ERR_FILTER: Final[int]
 if sys.version_info >= (3, 14):
-    IP_RECVTTL: int
+    IP_RECVTTL: Final[int]
 
     if sys.platform == "win32" or sys.platform == "linux":
-        IPV6_RECVERR: int
-        IP_RECVERR: int
-        SO_ORIGINAL_DST: int
+        IPV6_RECVERR: Final[int]
+        IP_RECVERR: Final[int]
+        SO_ORIGINAL_DST: Final[int]
 
     if sys.platform == "win32":
-        SOL_RFCOMM: int
-        SO_BTH_ENCRYPT: int
-        SO_BTH_MTU: int
-        SO_BTH_MTU_MAX: int
-        SO_BTH_MTU_MIN: int
-        TCP_QUICKACK: int
+        SOL_RFCOMM: Final[int]
+        SO_BTH_ENCRYPT: Final[int]
+        SO_BTH_MTU: Final[int]
+        SO_BTH_MTU_MAX: Final[int]
+        SO_BTH_MTU_MIN: Final[int]
+        TCP_QUICKACK: Final[int]
 
     if sys.platform == "linux":
-        CAN_RAW_ERR_FILTER: int
-        IP_FREEBIND: int
-        IP_RECVORIGDSTADDR: int
-        VMADDR_CID_LOCAL: int
+        IP_FREEBIND: Final[int]
+        IP_RECVORIGDSTADDR: Final[int]
+        VMADDR_CID_LOCAL: Final[int]
 
 if sys.platform != "win32" and sys.platform != "darwin":
-    IP_TRANSPARENT: int
+    IP_TRANSPARENT: Final[int]
 if sys.platform != "win32" and sys.platform != "darwin" and sys.version_info >= (3, 11):
-    IP_BIND_ADDRESS_NO_PORT: int
+    IP_BIND_ADDRESS_NO_PORT: Final[int]
 if sys.version_info >= (3, 12):
-    IP_ADD_SOURCE_MEMBERSHIP: int
-    IP_BLOCK_SOURCE: int
-    IP_DROP_SOURCE_MEMBERSHIP: int
-    IP_PKTINFO: int
-    IP_UNBLOCK_SOURCE: int
-
-IPV6_CHECKSUM: int
-IPV6_JOIN_GROUP: int
-IPV6_LEAVE_GROUP: int
-IPV6_MULTICAST_HOPS: int
-IPV6_MULTICAST_IF: int
-IPV6_MULTICAST_LOOP: int
-IPV6_RECVTCLASS: int
-IPV6_TCLASS: int
-IPV6_UNICAST_HOPS: int
-IPV6_V6ONLY: int
-IPV6_DONTFRAG: int
-IPV6_HOPLIMIT: int
-IPV6_HOPOPTS: int
-IPV6_PKTINFO: int
-IPV6_RECVRTHDR: int
-IPV6_RTHDR: int
+    IP_ADD_SOURCE_MEMBERSHIP: Final[int]
+    IP_BLOCK_SOURCE: Final[int]
+    IP_DROP_SOURCE_MEMBERSHIP: Final[int]
+    IP_PKTINFO: Final[int]
+    IP_UNBLOCK_SOURCE: Final[int]
+
+IPV6_CHECKSUM: Final[int]
+IPV6_JOIN_GROUP: Final[int]
+IPV6_LEAVE_GROUP: Final[int]
+IPV6_MULTICAST_HOPS: Final[int]
+IPV6_MULTICAST_IF: Final[int]
+IPV6_MULTICAST_LOOP: Final[int]
+IPV6_RECVTCLASS: Final[int]
+IPV6_TCLASS: Final[int]
+IPV6_UNICAST_HOPS: Final[int]
+IPV6_V6ONLY: Final[int]
+IPV6_DONTFRAG: Final[int]
+IPV6_HOPLIMIT: Final[int]
+IPV6_HOPOPTS: Final[int]
+IPV6_PKTINFO: Final[int]
+IPV6_RECVRTHDR: Final[int]
+IPV6_RTHDR: Final[int]
 if sys.platform != "win32":
-    IPV6_RTHDR_TYPE_0: int
-    IPV6_DSTOPTS: int
-    IPV6_NEXTHOP: int
-    IPV6_PATHMTU: int
-    IPV6_RECVDSTOPTS: int
-    IPV6_RECVHOPLIMIT: int
-    IPV6_RECVHOPOPTS: int
-    IPV6_RECVPATHMTU: int
-    IPV6_RECVPKTINFO: int
-    IPV6_RTHDRDSTOPTS: int
+    IPV6_RTHDR_TYPE_0: Final[int]
+    IPV6_DSTOPTS: Final[int]
+    IPV6_NEXTHOP: Final[int]
+    IPV6_PATHMTU: Final[int]
+    IPV6_RECVDSTOPTS: Final[int]
+    IPV6_RECVHOPLIMIT: Final[int]
+    IPV6_RECVHOPOPTS: Final[int]
+    IPV6_RECVPATHMTU: Final[int]
+    IPV6_RECVPKTINFO: Final[int]
+    IPV6_RTHDRDSTOPTS: Final[int]
 
 if sys.platform != "win32" and sys.platform != "linux":
-    IPV6_USE_MIN_MTU: int
-
-EAI_AGAIN: int
-EAI_BADFLAGS: int
-EAI_FAIL: int
-EAI_FAMILY: int
-EAI_MEMORY: int
-EAI_NODATA: int
-EAI_NONAME: int
-EAI_SERVICE: int
-EAI_SOCKTYPE: int
+    IPV6_USE_MIN_MTU: Final[int]
+
+EAI_AGAIN: Final[int]
+EAI_BADFLAGS: Final[int]
+EAI_FAIL: Final[int]
+EAI_FAMILY: Final[int]
+EAI_MEMORY: Final[int]
+EAI_NODATA: Final[int]
+EAI_NONAME: Final[int]
+EAI_SERVICE: Final[int]
+EAI_SOCKTYPE: Final[int]
 if sys.platform != "win32":
-    EAI_ADDRFAMILY: int
-    EAI_OVERFLOW: int
-    EAI_SYSTEM: int
+    EAI_ADDRFAMILY: Final[int]
+    EAI_OVERFLOW: Final[int]
+    EAI_SYSTEM: Final[int]
 if sys.platform != "win32" and sys.platform != "linux":
-    EAI_BADHINTS: int
-    EAI_MAX: int
-    EAI_PROTOCOL: int
-
-AI_ADDRCONFIG: int
-AI_ALL: int
-AI_CANONNAME: int
-AI_NUMERICHOST: int
-AI_NUMERICSERV: int
-AI_PASSIVE: int
-AI_V4MAPPED: int
+    EAI_BADHINTS: Final[int]
+    EAI_MAX: Final[int]
+    EAI_PROTOCOL: Final[int]
+
+AI_ADDRCONFIG: Final[int]
+AI_ALL: Final[int]
+AI_CANONNAME: Final[int]
+AI_NUMERICHOST: Final[int]
+AI_NUMERICSERV: Final[int]
+AI_PASSIVE: Final[int]
+AI_V4MAPPED: Final[int]
 if sys.platform != "win32" and sys.platform != "linux":
-    AI_DEFAULT: int
-    AI_MASK: int
-    AI_V4MAPPED_CFG: int
-
-NI_DGRAM: int
-NI_MAXHOST: int
-NI_MAXSERV: int
-NI_NAMEREQD: int
-NI_NOFQDN: int
-NI_NUMERICHOST: int
-NI_NUMERICSERV: int
+    AI_DEFAULT: Final[int]
+    AI_MASK: Final[int]
+    AI_V4MAPPED_CFG: Final[int]
+
+NI_DGRAM: Final[int]
+NI_MAXHOST: Final[int]
+NI_MAXSERV: Final[int]
+NI_NAMEREQD: Final[int]
+NI_NOFQDN: Final[int]
+NI_NUMERICHOST: Final[int]
+NI_NUMERICSERV: Final[int]
 if sys.platform == "linux" and sys.version_info >= (3, 13):
-    NI_IDN: int
+    NI_IDN: Final[int]
 
-TCP_FASTOPEN: int
-TCP_KEEPCNT: int
-TCP_KEEPINTVL: int
-TCP_MAXSEG: int
-TCP_NODELAY: int
+TCP_FASTOPEN: Final[int]
+TCP_KEEPCNT: Final[int]
+TCP_KEEPINTVL: Final[int]
+TCP_MAXSEG: Final[int]
+TCP_NODELAY: Final[int]
 if sys.platform != "win32":
-    TCP_NOTSENT_LOWAT: int
+    TCP_NOTSENT_LOWAT: Final[int]
 if sys.platform != "darwin":
-    TCP_KEEPIDLE: int
+    TCP_KEEPIDLE: Final[int]
 if sys.version_info >= (3, 10) and sys.platform == "darwin":
-    TCP_KEEPALIVE: int
+    TCP_KEEPALIVE: Final[int]
 if sys.version_info >= (3, 11) and sys.platform == "darwin":
-    TCP_CONNECTION_INFO: int
+    TCP_CONNECTION_INFO: Final[int]
 
 if sys.platform != "win32" and sys.platform != "darwin":
-    TCP_CONGESTION: int
-    TCP_CORK: int
-    TCP_DEFER_ACCEPT: int
-    TCP_INFO: int
-    TCP_LINGER2: int
-    TCP_QUICKACK: int
-    TCP_SYNCNT: int
-    TCP_USER_TIMEOUT: int
-    TCP_WINDOW_CLAMP: int
+    TCP_CONGESTION: Final[int]
+    TCP_CORK: Final[int]
+    TCP_DEFER_ACCEPT: Final[int]
+    TCP_INFO: Final[int]
+    TCP_LINGER2: Final[int]
+    TCP_QUICKACK: Final[int]
+    TCP_SYNCNT: Final[int]
+    TCP_USER_TIMEOUT: Final[int]
+    TCP_WINDOW_CLAMP: Final[int]
 if sys.platform == "linux" and sys.version_info >= (3, 12):
-    TCP_CC_INFO: int
-    TCP_FASTOPEN_CONNECT: int
-    TCP_FASTOPEN_KEY: int
-    TCP_FASTOPEN_NO_COOKIE: int
-    TCP_INQ: int
-    TCP_MD5SIG: int
-    TCP_MD5SIG_EXT: int
-    TCP_QUEUE_SEQ: int
-    TCP_REPAIR: int
-    TCP_REPAIR_OPTIONS: int
-    TCP_REPAIR_QUEUE: int
-    TCP_REPAIR_WINDOW: int
-    TCP_SAVED_SYN: int
-    TCP_SAVE_SYN: int
-    TCP_THIN_DUPACK: int
-    TCP_THIN_LINEAR_TIMEOUTS: int
-    TCP_TIMESTAMP: int
-    TCP_TX_DELAY: int
-    TCP_ULP: int
-    TCP_ZEROCOPY_RECEIVE: int
+    TCP_CC_INFO: Final[int]
+    TCP_FASTOPEN_CONNECT: Final[int]
+    TCP_FASTOPEN_KEY: Final[int]
+    TCP_FASTOPEN_NO_COOKIE: Final[int]
+    TCP_INQ: Final[int]
+    TCP_MD5SIG: Final[int]
+    TCP_MD5SIG_EXT: Final[int]
+    TCP_QUEUE_SEQ: Final[int]
+    TCP_REPAIR: Final[int]
+    TCP_REPAIR_OPTIONS: Final[int]
+    TCP_REPAIR_QUEUE: Final[int]
+    TCP_REPAIR_WINDOW: Final[int]
+    TCP_SAVED_SYN: Final[int]
+    TCP_SAVE_SYN: Final[int]
+    TCP_THIN_DUPACK: Final[int]
+    TCP_THIN_LINEAR_TIMEOUTS: Final[int]
+    TCP_TIMESTAMP: Final[int]
+    TCP_TX_DELAY: Final[int]
+    TCP_ULP: Final[int]
+    TCP_ZEROCOPY_RECEIVE: Final[int]
 
 # --------------------
 # Specifically documented constants
@@ -385,250 +386,250 @@ if sys.platform == "linux" and sys.version_info >= (3, 12):
 
 if sys.platform == "linux":
     # Availability: Linux >= 2.6.25, NetBSD >= 8
-    AF_CAN: int
-    PF_CAN: int
-    SOL_CAN_BASE: int
-    SOL_CAN_RAW: int
-    CAN_EFF_FLAG: int
-    CAN_EFF_MASK: int
-    CAN_ERR_FLAG: int
-    CAN_ERR_MASK: int
-    CAN_RAW: int
-    CAN_RAW_FILTER: int
-    CAN_RAW_LOOPBACK: int
-    CAN_RAW_RECV_OWN_MSGS: int
-    CAN_RTR_FLAG: int
-    CAN_SFF_MASK: int
+    AF_CAN: Final[int]
+    PF_CAN: Final[int]
+    SOL_CAN_BASE: Final[int]
+    SOL_CAN_RAW: Final[int]
+    CAN_EFF_FLAG: Final[int]
+    CAN_EFF_MASK: Final[int]
+    CAN_ERR_FLAG: Final[int]
+    CAN_ERR_MASK: Final[int]
+    CAN_RAW: Final[int]
+    CAN_RAW_FILTER: Final[int]
+    CAN_RAW_LOOPBACK: Final[int]
+    CAN_RAW_RECV_OWN_MSGS: Final[int]
+    CAN_RTR_FLAG: Final[int]
+    CAN_SFF_MASK: Final[int]
     if sys.version_info < (3, 11):
-        CAN_RAW_ERR_FILTER: int
+        CAN_RAW_ERR_FILTER: Final[int]
 
 if sys.platform == "linux":
     # Availability: Linux >= 2.6.25
-    CAN_BCM: int
-    CAN_BCM_TX_SETUP: int
-    CAN_BCM_TX_DELETE: int
-    CAN_BCM_TX_READ: int
-    CAN_BCM_TX_SEND: int
-    CAN_BCM_RX_SETUP: int
-    CAN_BCM_RX_DELETE: int
-    CAN_BCM_RX_READ: int
-    CAN_BCM_TX_STATUS: int
-    CAN_BCM_TX_EXPIRED: int
-    CAN_BCM_RX_STATUS: int
-    CAN_BCM_RX_TIMEOUT: int
-    CAN_BCM_RX_CHANGED: int
-    CAN_BCM_SETTIMER: int
-    CAN_BCM_STARTTIMER: int
-    CAN_BCM_TX_COUNTEVT: int
-    CAN_BCM_TX_ANNOUNCE: int
-    CAN_BCM_TX_CP_CAN_ID: int
-    CAN_BCM_RX_FILTER_ID: int
-    CAN_BCM_RX_CHECK_DLC: int
-    CAN_BCM_RX_NO_AUTOTIMER: int
-    CAN_BCM_RX_ANNOUNCE_RESUME: int
-    CAN_BCM_TX_RESET_MULTI_IDX: int
-    CAN_BCM_RX_RTR_FRAME: int
-    CAN_BCM_CAN_FD_FRAME: int
+    CAN_BCM: Final[int]
+    CAN_BCM_TX_SETUP: Final[int]
+    CAN_BCM_TX_DELETE: Final[int]
+    CAN_BCM_TX_READ: Final[int]
+    CAN_BCM_TX_SEND: Final[int]
+    CAN_BCM_RX_SETUP: Final[int]
+    CAN_BCM_RX_DELETE: Final[int]
+    CAN_BCM_RX_READ: Final[int]
+    CAN_BCM_TX_STATUS: Final[int]
+    CAN_BCM_TX_EXPIRED: Final[int]
+    CAN_BCM_RX_STATUS: Final[int]
+    CAN_BCM_RX_TIMEOUT: Final[int]
+    CAN_BCM_RX_CHANGED: Final[int]
+    CAN_BCM_SETTIMER: Final[int]
+    CAN_BCM_STARTTIMER: Final[int]
+    CAN_BCM_TX_COUNTEVT: Final[int]
+    CAN_BCM_TX_ANNOUNCE: Final[int]
+    CAN_BCM_TX_CP_CAN_ID: Final[int]
+    CAN_BCM_RX_FILTER_ID: Final[int]
+    CAN_BCM_RX_CHECK_DLC: Final[int]
+    CAN_BCM_RX_NO_AUTOTIMER: Final[int]
+    CAN_BCM_RX_ANNOUNCE_RESUME: Final[int]
+    CAN_BCM_TX_RESET_MULTI_IDX: Final[int]
+    CAN_BCM_RX_RTR_FRAME: Final[int]
+    CAN_BCM_CAN_FD_FRAME: Final[int]
 
 if sys.platform == "linux":
     # Availability: Linux >= 3.6
-    CAN_RAW_FD_FRAMES: int
+    CAN_RAW_FD_FRAMES: Final[int]
     # Availability: Linux >= 4.1
-    CAN_RAW_JOIN_FILTERS: int
+    CAN_RAW_JOIN_FILTERS: Final[int]
     # Availability: Linux >= 2.6.25
-    CAN_ISOTP: int
+    CAN_ISOTP: Final[int]
     # Availability: Linux >= 5.4
-    CAN_J1939: int
-
-    J1939_MAX_UNICAST_ADDR: int
-    J1939_IDLE_ADDR: int
-    J1939_NO_ADDR: int
-    J1939_NO_NAME: int
-    J1939_PGN_REQUEST: int
-    J1939_PGN_ADDRESS_CLAIMED: int
-    J1939_PGN_ADDRESS_COMMANDED: int
-    J1939_PGN_PDU1_MAX: int
-    J1939_PGN_MAX: int
-    J1939_NO_PGN: int
-
-    SO_J1939_FILTER: int
-    SO_J1939_PROMISC: int
-    SO_J1939_SEND_PRIO: int
-    SO_J1939_ERRQUEUE: int
-
-    SCM_J1939_DEST_ADDR: int
-    SCM_J1939_DEST_NAME: int
-    SCM_J1939_PRIO: int
-    SCM_J1939_ERRQUEUE: int
-
-    J1939_NLA_PAD: int
-    J1939_NLA_BYTES_ACKED: int
-    J1939_EE_INFO_NONE: int
-    J1939_EE_INFO_TX_ABORT: int
-    J1939_FILTER_MAX: int
+    CAN_J1939: Final[int]
+
+    J1939_MAX_UNICAST_ADDR: Final[int]
+    J1939_IDLE_ADDR: Final[int]
+    J1939_NO_ADDR: Final[int]
+    J1939_NO_NAME: Final[int]
+    J1939_PGN_REQUEST: Final[int]
+    J1939_PGN_ADDRESS_CLAIMED: Final[int]
+    J1939_PGN_ADDRESS_COMMANDED: Final[int]
+    J1939_PGN_PDU1_MAX: Final[int]
+    J1939_PGN_MAX: Final[int]
+    J1939_NO_PGN: Final[int]
+
+    SO_J1939_FILTER: Final[int]
+    SO_J1939_PROMISC: Final[int]
+    SO_J1939_SEND_PRIO: Final[int]
+    SO_J1939_ERRQUEUE: Final[int]
+
+    SCM_J1939_DEST_ADDR: Final[int]
+    SCM_J1939_DEST_NAME: Final[int]
+    SCM_J1939_PRIO: Final[int]
+    SCM_J1939_ERRQUEUE: Final[int]
+
+    J1939_NLA_PAD: Final[int]
+    J1939_NLA_BYTES_ACKED: Final[int]
+    J1939_EE_INFO_NONE: Final[int]
+    J1939_EE_INFO_TX_ABORT: Final[int]
+    J1939_FILTER_MAX: Final[int]
 
 if sys.version_info >= (3, 12) and sys.platform != "linux" and sys.platform != "win32" and sys.platform != "darwin":
     # Availability: FreeBSD >= 14.0
-    AF_DIVERT: int
-    PF_DIVERT: int
+    AF_DIVERT: Final[int]
+    PF_DIVERT: Final[int]
 
 if sys.platform == "linux":
     # Availability: Linux >= 2.2
-    AF_PACKET: int
-    PF_PACKET: int
-    PACKET_BROADCAST: int
-    PACKET_FASTROUTE: int
-    PACKET_HOST: int
-    PACKET_LOOPBACK: int
-    PACKET_MULTICAST: int
-    PACKET_OTHERHOST: int
-    PACKET_OUTGOING: int
+    AF_PACKET: Final[int]
+    PF_PACKET: Final[int]
+    PACKET_BROADCAST: Final[int]
+    PACKET_FASTROUTE: Final[int]
+    PACKET_HOST: Final[int]
+    PACKET_LOOPBACK: Final[int]
+    PACKET_MULTICAST: Final[int]
+    PACKET_OTHERHOST: Final[int]
+    PACKET_OUTGOING: Final[int]
 
 if sys.version_info >= (3, 12) and sys.platform == "linux":
-    ETH_P_ALL: int
+    ETH_P_ALL: Final[int]
 
 if sys.platform == "linux":
     # Availability: Linux >= 2.6.30
-    AF_RDS: int
-    PF_RDS: int
-    SOL_RDS: int
+    AF_RDS: Final[int]
+    PF_RDS: Final[int]
+    SOL_RDS: Final[int]
     # These are present in include/linux/rds.h but don't always show up
     # here.
-    RDS_CANCEL_SENT_TO: int
-    RDS_CMSG_RDMA_ARGS: int
-    RDS_CMSG_RDMA_DEST: int
-    RDS_CMSG_RDMA_MAP: int
-    RDS_CMSG_RDMA_STATUS: int
-    RDS_CONG_MONITOR: int
-    RDS_FREE_MR: int
-    RDS_GET_MR: int
-    RDS_GET_MR_FOR_DEST: int
-    RDS_RDMA_DONTWAIT: int
-    RDS_RDMA_FENCE: int
-    RDS_RDMA_INVALIDATE: int
-    RDS_RDMA_NOTIFY_ME: int
-    RDS_RDMA_READWRITE: int
-    RDS_RDMA_SILENT: int
-    RDS_RDMA_USE_ONCE: int
-    RDS_RECVERR: int
+    RDS_CANCEL_SENT_TO: Final[int]
+    RDS_CMSG_RDMA_ARGS: Final[int]
+    RDS_CMSG_RDMA_DEST: Final[int]
+    RDS_CMSG_RDMA_MAP: Final[int]
+    RDS_CMSG_RDMA_STATUS: Final[int]
+    RDS_CONG_MONITOR: Final[int]
+    RDS_FREE_MR: Final[int]
+    RDS_GET_MR: Final[int]
+    RDS_GET_MR_FOR_DEST: Final[int]
+    RDS_RDMA_DONTWAIT: Final[int]
+    RDS_RDMA_FENCE: Final[int]
+    RDS_RDMA_INVALIDATE: Final[int]
+    RDS_RDMA_NOTIFY_ME: Final[int]
+    RDS_RDMA_READWRITE: Final[int]
+    RDS_RDMA_SILENT: Final[int]
+    RDS_RDMA_USE_ONCE: Final[int]
+    RDS_RECVERR: Final[int]
 
     # This is supported by CPython but doesn't seem to be a real thing.
     # The closest existing constant in rds.h is RDS_CMSG_CONG_UPDATE
-    # RDS_CMSG_RDMA_UPDATE: int
+    # RDS_CMSG_RDMA_UPDATE: Final[int]
 
 if sys.platform == "win32":
-    SIO_RCVALL: int
-    SIO_KEEPALIVE_VALS: int
-    SIO_LOOPBACK_FAST_PATH: int
-    RCVALL_MAX: int
-    RCVALL_OFF: int
-    RCVALL_ON: int
-    RCVALL_SOCKETLEVELONLY: int
+    SIO_RCVALL: Final[int]
+    SIO_KEEPALIVE_VALS: Final[int]
+    SIO_LOOPBACK_FAST_PATH: Final[int]
+    RCVALL_MAX: Final[int]
+    RCVALL_OFF: Final[int]
+    RCVALL_ON: Final[int]
+    RCVALL_SOCKETLEVELONLY: Final[int]
 
 if sys.platform == "linux":
-    AF_TIPC: int
-    SOL_TIPC: int
-    TIPC_ADDR_ID: int
-    TIPC_ADDR_NAME: int
-    TIPC_ADDR_NAMESEQ: int
-    TIPC_CFG_SRV: int
-    TIPC_CLUSTER_SCOPE: int
-    TIPC_CONN_TIMEOUT: int
-    TIPC_CRITICAL_IMPORTANCE: int
-    TIPC_DEST_DROPPABLE: int
-    TIPC_HIGH_IMPORTANCE: int
-    TIPC_IMPORTANCE: int
-    TIPC_LOW_IMPORTANCE: int
-    TIPC_MEDIUM_IMPORTANCE: int
-    TIPC_NODE_SCOPE: int
-    TIPC_PUBLISHED: int
-    TIPC_SRC_DROPPABLE: int
-    TIPC_SUBSCR_TIMEOUT: int
-    TIPC_SUB_CANCEL: int
-    TIPC_SUB_PORTS: int
-    TIPC_SUB_SERVICE: int
-    TIPC_TOP_SRV: int
-    TIPC_WAIT_FOREVER: int
-    TIPC_WITHDRAWN: int
-    TIPC_ZONE_SCOPE: int
+    AF_TIPC: Final[int]
+    SOL_TIPC: Final[int]
+    TIPC_ADDR_ID: Final[int]
+    TIPC_ADDR_NAME: Final[int]
+    TIPC_ADDR_NAMESEQ: Final[int]
+    TIPC_CFG_SRV: Final[int]
+    TIPC_CLUSTER_SCOPE: Final[int]
+    TIPC_CONN_TIMEOUT: Final[int]
+    TIPC_CRITICAL_IMPORTANCE: Final[int]
+    TIPC_DEST_DROPPABLE: Final[int]
+    TIPC_HIGH_IMPORTANCE: Final[int]
+    TIPC_IMPORTANCE: Final[int]
+    TIPC_LOW_IMPORTANCE: Final[int]
+    TIPC_MEDIUM_IMPORTANCE: Final[int]
+    TIPC_NODE_SCOPE: Final[int]
+    TIPC_PUBLISHED: Final[int]
+    TIPC_SRC_DROPPABLE: Final[int]
+    TIPC_SUBSCR_TIMEOUT: Final[int]
+    TIPC_SUB_CANCEL: Final[int]
+    TIPC_SUB_PORTS: Final[int]
+    TIPC_SUB_SERVICE: Final[int]
+    TIPC_TOP_SRV: Final[int]
+    TIPC_WAIT_FOREVER: Final[int]
+    TIPC_WITHDRAWN: Final[int]
+    TIPC_ZONE_SCOPE: Final[int]
 
 if sys.platform == "linux":
     # Availability: Linux >= 2.6.38
-    AF_ALG: int
-    SOL_ALG: int
-    ALG_OP_DECRYPT: int
-    ALG_OP_ENCRYPT: int
-    ALG_OP_SIGN: int
-    ALG_OP_VERIFY: int
-    ALG_SET_AEAD_ASSOCLEN: int
-    ALG_SET_AEAD_AUTHSIZE: int
-    ALG_SET_IV: int
-    ALG_SET_KEY: int
-    ALG_SET_OP: int
-    ALG_SET_PUBKEY: int
+    AF_ALG: Final[int]
+    SOL_ALG: Final[int]
+    ALG_OP_DECRYPT: Final[int]
+    ALG_OP_ENCRYPT: Final[int]
+    ALG_OP_SIGN: Final[int]
+    ALG_OP_VERIFY: Final[int]
+    ALG_SET_AEAD_ASSOCLEN: Final[int]
+    ALG_SET_AEAD_AUTHSIZE: Final[int]
+    ALG_SET_IV: Final[int]
+    ALG_SET_KEY: Final[int]
+    ALG_SET_OP: Final[int]
+    ALG_SET_PUBKEY: Final[int]
 
 if sys.platform == "linux":
     # Availability: Linux >= 4.8 (or maybe 3.9, CPython docs are confusing)
-    AF_VSOCK: int
-    IOCTL_VM_SOCKETS_GET_LOCAL_CID: int
-    VMADDR_CID_ANY: int
-    VMADDR_CID_HOST: int
-    VMADDR_PORT_ANY: int
-    SO_VM_SOCKETS_BUFFER_MAX_SIZE: int
-    SO_VM_SOCKETS_BUFFER_SIZE: int
-    SO_VM_SOCKETS_BUFFER_MIN_SIZE: int
-    VM_SOCKETS_INVALID_VERSION: int  # undocumented
+    AF_VSOCK: Final[int]
+    IOCTL_VM_SOCKETS_GET_LOCAL_CID: Final = 0x7B9
+    VMADDR_CID_ANY: Final = 0xFFFFFFFF
+    VMADDR_CID_HOST: Final = 2
+    VMADDR_PORT_ANY: Final = 0xFFFFFFFF
+    SO_VM_SOCKETS_BUFFER_MAX_SIZE: Final = 2
+    SO_VM_SOCKETS_BUFFER_SIZE: Final = 0
+    SO_VM_SOCKETS_BUFFER_MIN_SIZE: Final = 1
+    VM_SOCKETS_INVALID_VERSION: Final = 0xFFFFFFFF  # undocumented
 
 # Documented as only available on BSD, macOS, but empirically sometimes
 # available on Windows
 if sys.platform != "linux":
-    AF_LINK: int
+    AF_LINK: Final[int]
 
 has_ipv6: bool
 
 if sys.platform != "darwin" and sys.platform != "linux":
-    BDADDR_ANY: str
-    BDADDR_LOCAL: str
+    BDADDR_ANY: Final = "00:00:00:00:00:00"
+    BDADDR_LOCAL: Final = "00:00:00:FF:FF:FF"
 
 if sys.platform != "win32" and sys.platform != "darwin" and sys.platform != "linux":
-    HCI_FILTER: int  # not in NetBSD or DragonFlyBSD
-    HCI_TIME_STAMP: int  # not in FreeBSD, NetBSD, or DragonFlyBSD
-    HCI_DATA_DIR: int  # not in FreeBSD, NetBSD, or DragonFlyBSD
+    HCI_FILTER: Final[int]  # not in NetBSD or DragonFlyBSD
+    HCI_TIME_STAMP: Final[int]  # not in FreeBSD, NetBSD, or DragonFlyBSD
+    HCI_DATA_DIR: Final[int]  # not in FreeBSD, NetBSD, or DragonFlyBSD
 
 if sys.platform == "linux":
-    AF_QIPCRTR: int  # Availability: Linux >= 4.7
+    AF_QIPCRTR: Final[int]  # Availability: Linux >= 4.7
 
 if sys.version_info >= (3, 11) and sys.platform != "linux" and sys.platform != "win32" and sys.platform != "darwin":
     # FreeBSD
-    SCM_CREDS2: int
-    LOCAL_CREDS: int
-    LOCAL_CREDS_PERSISTENT: int
+    SCM_CREDS2: Final[int]
+    LOCAL_CREDS: Final[int]
+    LOCAL_CREDS_PERSISTENT: Final[int]
 
 if sys.version_info >= (3, 11) and sys.platform == "linux":
-    SO_INCOMING_CPU: int  # Availability: Linux >= 3.9
+    SO_INCOMING_CPU: Final[int]  # Availability: Linux >= 3.9
 
 if sys.version_info >= (3, 12) and sys.platform == "win32":
     # Availability: Windows
-    AF_HYPERV: int
-    HV_PROTOCOL_RAW: int
-    HVSOCKET_CONNECT_TIMEOUT: int
-    HVSOCKET_CONNECT_TIMEOUT_MAX: int
-    HVSOCKET_CONNECTED_SUSPEND: int
-    HVSOCKET_ADDRESS_FLAG_PASSTHRU: int
-    HV_GUID_ZERO: str
-    HV_GUID_WILDCARD: str
-    HV_GUID_BROADCAST: str
-    HV_GUID_CHILDREN: str
-    HV_GUID_LOOPBACK: str
-    HV_GUID_PARENT: str
+    AF_HYPERV: Final[int]
+    HV_PROTOCOL_RAW: Final[int]
+    HVSOCKET_CONNECT_TIMEOUT: Final[int]
+    HVSOCKET_CONNECT_TIMEOUT_MAX: Final[int]
+    HVSOCKET_CONNECTED_SUSPEND: Final[int]
+    HVSOCKET_ADDRESS_FLAG_PASSTHRU: Final[int]
+    HV_GUID_ZERO: Final = "00000000-0000-0000-0000-000000000000"
+    HV_GUID_WILDCARD: Final = "00000000-0000-0000-0000-000000000000"
+    HV_GUID_BROADCAST: Final = "FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF"
+    HV_GUID_CHILDREN: Final = "90DB8B89-0D35-4F79-8CE9-49EA0AC8B7CD"
+    HV_GUID_LOOPBACK: Final = "E0E16197-DD56-4A10-9195-5EE7A155A838"
+    HV_GUID_PARENT: Final = "A42E7CDA-D03F-480C-9CC2-A4DE20ABB878"
 
 if sys.version_info >= (3, 12):
     if sys.platform != "win32":
         # Availability: Linux, FreeBSD, macOS
-        ETHERTYPE_ARP: int
-        ETHERTYPE_IP: int
-        ETHERTYPE_IPV6: int
-        ETHERTYPE_VLAN: int
+        ETHERTYPE_ARP: Final[int]
+        ETHERTYPE_IP: Final[int]
+        ETHERTYPE_IPV6: Final[int]
+        ETHERTYPE_VLAN: Final[int]
 
 # --------------------
 # Semi-documented constants
@@ -638,98 +639,99 @@ if sys.version_info >= (3, 12):
 
 if sys.platform == "linux":
     # Netlink is defined by Linux
-    AF_NETLINK: int
-    NETLINK_CRYPTO: int
-    NETLINK_DNRTMSG: int
-    NETLINK_FIREWALL: int
-    NETLINK_IP6_FW: int
-    NETLINK_NFLOG: int
-    NETLINK_ROUTE: int
-    NETLINK_USERSOCK: int
-    NETLINK_XFRM: int
+    AF_NETLINK: Final[int]
+    NETLINK_CRYPTO: Final[int]
+    NETLINK_DNRTMSG: Final[int]
+    NETLINK_FIREWALL: Final[int]
+    NETLINK_IP6_FW: Final[int]
+    NETLINK_NFLOG: Final[int]
+    NETLINK_ROUTE: Final[int]
+    NETLINK_USERSOCK: Final[int]
+    NETLINK_XFRM: Final[int]
     # Technically still supported by CPython
-    # NETLINK_ARPD: int  # linux 2.0 to 2.6.12 (EOL August 2005)
-    # NETLINK_ROUTE6: int  # linux 2.2 to 2.6.12 (EOL August 2005)
-    # NETLINK_SKIP: int  # linux 2.0 to 2.6.12 (EOL August 2005)
-    # NETLINK_TAPBASE: int  # linux 2.2 to 2.6.12 (EOL August 2005)
-    # NETLINK_TCPDIAG: int  # linux 2.6.0 to 2.6.13 (EOL December 2005)
-    # NETLINK_W1: int  # linux 2.6.13 to 2.6.17 (EOL October 2006)
+    # NETLINK_ARPD: Final[int]  # linux 2.0 to 2.6.12 (EOL August 2005)
+    # NETLINK_ROUTE6: Final[int]  # linux 2.2 to 2.6.12 (EOL August 2005)
+    # NETLINK_SKIP: Final[int]  # linux 2.0 to 2.6.12 (EOL August 2005)
+    # NETLINK_TAPBASE: Final[int]  # linux 2.2 to 2.6.12 (EOL August 2005)
+    # NETLINK_TCPDIAG: Final[int]  # linux 2.6.0 to 2.6.13 (EOL December 2005)
+    # NETLINK_W1: Final[int]  # linux 2.6.13 to 2.6.17 (EOL October 2006)
 
 if sys.platform == "darwin":
-    PF_SYSTEM: int
-    SYSPROTO_CONTROL: int
+    PF_SYSTEM: Final[int]
+    SYSPROTO_CONTROL: Final[int]
 
 if sys.platform != "darwin" and sys.platform != "linux":
-    AF_BLUETOOTH: int
+    AF_BLUETOOTH: Final[int]
 
 if sys.platform != "win32" and sys.platform != "darwin" and sys.platform != "linux":
     # Linux and some BSD support is explicit in the docs
     # Windows and macOS do not support in practice
-    BTPROTO_HCI: int
-    BTPROTO_L2CAP: int
-    BTPROTO_SCO: int  # not in FreeBSD
+    BTPROTO_HCI: Final[int]
+    BTPROTO_L2CAP: Final[int]
+    BTPROTO_SCO: Final[int]  # not in FreeBSD
 if sys.platform != "darwin" and sys.platform != "linux":
-    BTPROTO_RFCOMM: int
+    BTPROTO_RFCOMM: Final[int]
 
 if sys.platform == "linux":
-    UDPLITE_RECV_CSCOV: int
-    UDPLITE_SEND_CSCOV: int
+    UDPLITE_RECV_CSCOV: Final[int]
+    UDPLITE_SEND_CSCOV: Final[int]
 
 # --------------------
 # Documented under socket.shutdown
 # --------------------
-SHUT_RD: int
-SHUT_RDWR: int
-SHUT_WR: int
+SHUT_RD: Final[int]
+SHUT_RDWR: Final[int]
+SHUT_WR: Final[int]
 
 # --------------------
 # Undocumented constants
 # --------------------
 
 # Undocumented address families
-AF_APPLETALK: int
-AF_DECnet: int
-AF_IPX: int
-AF_SNA: int
+AF_APPLETALK: Final[int]
+AF_DECnet: Final[int]
+AF_IPX: Final[int]
+AF_SNA: Final[int]
 
 if sys.platform != "win32":
-    AF_ROUTE: int
+    AF_ROUTE: Final[int]
 
 if sys.platform == "darwin":
-    AF_SYSTEM: int
+    AF_SYSTEM: Final[int]
 
 if sys.platform != "darwin":
-    AF_IRDA: int
+    AF_IRDA: Final[int]
 
 if sys.platform != "win32" and sys.platform != "darwin":
-    AF_ASH: int
-    AF_ATMPVC: int
-    AF_ATMSVC: int
-    AF_AX25: int
-    AF_BRIDGE: int
-    AF_ECONET: int
-    AF_KEY: int
-    AF_LLC: int
-    AF_NETBEUI: int
-    AF_NETROM: int
-    AF_PPPOX: int
-    AF_ROSE: int
-    AF_SECURITY: int
-    AF_WANPIPE: int
-    AF_X25: int
+    AF_ASH: Final[int]
+    AF_ATMPVC: Final[int]
+    AF_ATMSVC: Final[int]
+    AF_AX25: Final[int]
+    AF_BRIDGE: Final[int]
+    AF_ECONET: Final[int]
+    AF_KEY: Final[int]
+    AF_LLC: Final[int]
+    AF_NETBEUI: Final[int]
+    AF_NETROM: Final[int]
+    AF_PPPOX: Final[int]
+    AF_ROSE: Final[int]
+    AF_SECURITY: Final[int]
+    AF_WANPIPE: Final[int]
+    AF_X25: Final[int]
 
 # Miscellaneous undocumented
 
 if sys.platform != "win32" and sys.platform != "linux":
-    LOCAL_PEERCRED: int
+    LOCAL_PEERCRED: Final[int]
 
 if sys.platform != "win32" and sys.platform != "darwin":
     # Defined in linux socket.h, but this isn't always present for
     # some reason.
-    IPX_TYPE: int
+    IPX_TYPE: Final[int]
 
 # ===== Classes =====
 
+@disjoint_base
 class socket:
     @property
     def family(self) -> int: ...
@@ -742,10 +744,10 @@ class socket:
     def timeout(self) -> float | None: ...  # noqa: F811
     if sys.platform == "win32":
         def __init__(
-            self, family: int = ..., type: int = ..., proto: int = ..., fileno: SupportsIndex | bytes | None = ...
+            self, family: int = ..., type: int = ..., proto: int = ..., fileno: SupportsIndex | bytes | None = None
         ) -> None: ...
     else:
-        def __init__(self, family: int = ..., type: int = ..., proto: int = ..., fileno: SupportsIndex | None = ...) -> None: ...
+        def __init__(self, family: int = ..., type: int = ..., proto: int = ..., fileno: SupportsIndex | None = None) -> None: ...
 
     def bind(self, address: _Address, /) -> None: ...
     def close(self) -> None: ...
@@ -765,18 +767,18 @@ class socket:
         def ioctl(self, control: int, option: int | tuple[int, int, int] | bool, /) -> None: ...
 
     def listen(self, backlog: int = ..., /) -> None: ...
-    def recv(self, bufsize: int, flags: int = ..., /) -> bytes: ...
-    def recvfrom(self, bufsize: int, flags: int = ..., /) -> tuple[bytes, _RetAddress]: ...
+    def recv(self, bufsize: int, flags: int = 0, /) -> bytes: ...
+    def recvfrom(self, bufsize: int, flags: int = 0, /) -> tuple[bytes, _RetAddress]: ...
     if sys.platform != "win32":
-        def recvmsg(self, bufsize: int, ancbufsize: int = ..., flags: int = ..., /) -> tuple[bytes, list[_CMSG], int, Any]: ...
+        def recvmsg(self, bufsize: int, ancbufsize: int = 0, flags: int = 0, /) -> tuple[bytes, list[_CMSG], int, Any]: ...
         def recvmsg_into(
-            self, buffers: Iterable[WriteableBuffer], ancbufsize: int = ..., flags: int = ..., /
+            self, buffers: Iterable[WriteableBuffer], ancbufsize: int = 0, flags: int = 0, /
         ) -> tuple[int, list[_CMSG], int, Any]: ...
 
-    def recvfrom_into(self, buffer: WriteableBuffer, nbytes: int = ..., flags: int = ...) -> tuple[int, _RetAddress]: ...
-    def recv_into(self, buffer: WriteableBuffer, nbytes: int = ..., flags: int = ...) -> int: ...
-    def send(self, data: ReadableBuffer, flags: int = ..., /) -> int: ...
-    def sendall(self, data: ReadableBuffer, flags: int = ..., /) -> None: ...
+    def recvfrom_into(self, buffer: WriteableBuffer, nbytes: int = 0, flags: int = 0) -> tuple[int, _RetAddress]: ...
+    def recv_into(self, buffer: WriteableBuffer, nbytes: int = 0, flags: int = 0) -> int: ...
+    def send(self, data: ReadableBuffer, flags: int = 0, /) -> int: ...
+    def sendall(self, data: ReadableBuffer, flags: int = 0, /) -> None: ...
     @overload
     def sendto(self, data: ReadableBuffer, address: _Address, /) -> int: ...
     @overload
@@ -786,13 +788,13 @@ class socket:
             self,
             buffers: Iterable[ReadableBuffer],
             ancdata: Iterable[_CMSGArg] = ...,
-            flags: int = ...,
-            address: _Address | None = ...,
+            flags: int = 0,
+            address: _Address | None = None,
             /,
         ) -> int: ...
     if sys.platform == "linux":
         def sendmsg_afalg(
-            self, msg: Iterable[ReadableBuffer] = ..., *, op: int, iv: Any = ..., assoclen: int = ..., flags: int = ...
+            self, msg: Iterable[ReadableBuffer] = ..., *, op: int, iv: Any = ..., assoclen: int = ..., flags: int = 0
         ) -> int: ...
 
     def setblocking(self, flag: bool, /) -> None: ...
@@ -815,12 +817,7 @@ def dup(fd: SupportsIndex, /) -> int: ...
 
 # the 5th tuple item is an address
 def getaddrinfo(
-    host: bytes | str | None,
-    port: bytes | str | int | None,
-    family: int = ...,
-    type: int = ...,
-    proto: int = ...,
-    flags: int = ...,
+    host: bytes | str | None, port: bytes | str | int | None, family: int = ..., type: int = 0, proto: int = 0, flags: int = 0
 ) -> list[tuple[int, int, int, str, tuple[str, int] | tuple[str, int, int, int] | tuple[int, bytes]]]: ...
 def gethostbyname(hostname: str, /) -> str: ...
 def gethostbyname_ex(hostname: str, /) -> tuple[str, list[str], list[str]]: ...
@@ -847,7 +844,7 @@ if sys.platform != "win32":
     def sethostname(name: str, /) -> None: ...
     def CMSG_LEN(length: int, /) -> int: ...
     def CMSG_SPACE(length: int, /) -> int: ...
-    def socketpair(family: int = ..., type: int = ..., proto: int = ..., /) -> tuple[socket, socket]: ...
+    def socketpair(family: int = ..., type: int = ..., proto: int = 0, /) -> tuple[socket, socket]: ...
 
 def if_nameindex() -> list[tuple[int, str]]: ...
 def if_nametoindex(oname: str, /) -> int: ...
diff --git a/mypy/typeshed/stdlib/_sqlite3.pyi b/mypy/typeshed/stdlib/_sqlite3.pyi
index 6f06542c1ba7..50006dcf4032 100644
--- a/mypy/typeshed/stdlib/_sqlite3.pyi
+++ b/mypy/typeshed/stdlib/_sqlite3.pyi
@@ -16,6 +16,7 @@ from sqlite3 import (
     ProgrammingError as ProgrammingError,
     Row as Row,
     Warning as Warning,
+    _IsolationLevel,
 )
 from typing import Any, Final, Literal, TypeVar, overload
 from typing_extensions import TypeAlias
@@ -29,45 +30,45 @@ _SqliteData: TypeAlias = str | ReadableBuffer | int | float | None
 _Adapter: TypeAlias = Callable[[_T], _SqliteData]
 _Converter: TypeAlias = Callable[[bytes], Any]
 
-PARSE_COLNAMES: Final[int]
-PARSE_DECLTYPES: Final[int]
-SQLITE_ALTER_TABLE: Final[int]
-SQLITE_ANALYZE: Final[int]
-SQLITE_ATTACH: Final[int]
-SQLITE_CREATE_INDEX: Final[int]
-SQLITE_CREATE_TABLE: Final[int]
-SQLITE_CREATE_TEMP_INDEX: Final[int]
-SQLITE_CREATE_TEMP_TABLE: Final[int]
-SQLITE_CREATE_TEMP_TRIGGER: Final[int]
-SQLITE_CREATE_TEMP_VIEW: Final[int]
-SQLITE_CREATE_TRIGGER: Final[int]
-SQLITE_CREATE_VIEW: Final[int]
-SQLITE_CREATE_VTABLE: Final[int]
-SQLITE_DELETE: Final[int]
-SQLITE_DENY: Final[int]
-SQLITE_DETACH: Final[int]
-SQLITE_DONE: Final[int]
-SQLITE_DROP_INDEX: Final[int]
-SQLITE_DROP_TABLE: Final[int]
-SQLITE_DROP_TEMP_INDEX: Final[int]
-SQLITE_DROP_TEMP_TABLE: Final[int]
-SQLITE_DROP_TEMP_TRIGGER: Final[int]
-SQLITE_DROP_TEMP_VIEW: Final[int]
-SQLITE_DROP_TRIGGER: Final[int]
-SQLITE_DROP_VIEW: Final[int]
-SQLITE_DROP_VTABLE: Final[int]
-SQLITE_FUNCTION: Final[int]
-SQLITE_IGNORE: Final[int]
-SQLITE_INSERT: Final[int]
-SQLITE_OK: Final[int]
-SQLITE_PRAGMA: Final[int]
-SQLITE_READ: Final[int]
-SQLITE_RECURSIVE: Final[int]
-SQLITE_REINDEX: Final[int]
-SQLITE_SAVEPOINT: Final[int]
-SQLITE_SELECT: Final[int]
-SQLITE_TRANSACTION: Final[int]
-SQLITE_UPDATE: Final[int]
+PARSE_COLNAMES: Final = 2
+PARSE_DECLTYPES: Final = 1
+SQLITE_ALTER_TABLE: Final = 26
+SQLITE_ANALYZE: Final = 28
+SQLITE_ATTACH: Final = 24
+SQLITE_CREATE_INDEX: Final = 1
+SQLITE_CREATE_TABLE: Final = 2
+SQLITE_CREATE_TEMP_INDEX: Final = 3
+SQLITE_CREATE_TEMP_TABLE: Final = 4
+SQLITE_CREATE_TEMP_TRIGGER: Final = 5
+SQLITE_CREATE_TEMP_VIEW: Final = 6
+SQLITE_CREATE_TRIGGER: Final = 7
+SQLITE_CREATE_VIEW: Final = 8
+SQLITE_CREATE_VTABLE: Final = 29
+SQLITE_DELETE: Final = 9
+SQLITE_DENY: Final = 1
+SQLITE_DETACH: Final = 25
+SQLITE_DONE: Final = 101
+SQLITE_DROP_INDEX: Final = 10
+SQLITE_DROP_TABLE: Final = 11
+SQLITE_DROP_TEMP_INDEX: Final = 12
+SQLITE_DROP_TEMP_TABLE: Final = 13
+SQLITE_DROP_TEMP_TRIGGER: Final = 14
+SQLITE_DROP_TEMP_VIEW: Final = 15
+SQLITE_DROP_TRIGGER: Final = 16
+SQLITE_DROP_VIEW: Final = 17
+SQLITE_DROP_VTABLE: Final = 30
+SQLITE_FUNCTION: Final = 31
+SQLITE_IGNORE: Final = 2
+SQLITE_INSERT: Final = 18
+SQLITE_OK: Final = 0
+SQLITE_PRAGMA: Final = 19
+SQLITE_READ: Final = 20
+SQLITE_RECURSIVE: Final = 33
+SQLITE_REINDEX: Final = 27
+SQLITE_SAVEPOINT: Final = 32
+SQLITE_SELECT: Final = 21
+SQLITE_TRANSACTION: Final = 22
+SQLITE_UPDATE: Final = 23
 adapters: dict[tuple[type[Any], type[Any]], _Adapter[Any]]
 converters: dict[str, _Converter]
 sqlite_version: str
@@ -76,141 +77,141 @@ if sys.version_info < (3, 12):
     version: str
 
 if sys.version_info >= (3, 12):
-    LEGACY_TRANSACTION_CONTROL: Final[int]
-    SQLITE_DBCONFIG_DEFENSIVE: Final[int]
-    SQLITE_DBCONFIG_DQS_DDL: Final[int]
-    SQLITE_DBCONFIG_DQS_DML: Final[int]
-    SQLITE_DBCONFIG_ENABLE_FKEY: Final[int]
-    SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER: Final[int]
-    SQLITE_DBCONFIG_ENABLE_LOAD_EXTENSION: Final[int]
-    SQLITE_DBCONFIG_ENABLE_QPSG: Final[int]
-    SQLITE_DBCONFIG_ENABLE_TRIGGER: Final[int]
-    SQLITE_DBCONFIG_ENABLE_VIEW: Final[int]
-    SQLITE_DBCONFIG_LEGACY_ALTER_TABLE: Final[int]
-    SQLITE_DBCONFIG_LEGACY_FILE_FORMAT: Final[int]
-    SQLITE_DBCONFIG_NO_CKPT_ON_CLOSE: Final[int]
-    SQLITE_DBCONFIG_RESET_DATABASE: Final[int]
-    SQLITE_DBCONFIG_TRIGGER_EQP: Final[int]
-    SQLITE_DBCONFIG_TRUSTED_SCHEMA: Final[int]
-    SQLITE_DBCONFIG_WRITABLE_SCHEMA: Final[int]
+    LEGACY_TRANSACTION_CONTROL: Final = -1
+    SQLITE_DBCONFIG_DEFENSIVE: Final = 1010
+    SQLITE_DBCONFIG_DQS_DDL: Final = 1014
+    SQLITE_DBCONFIG_DQS_DML: Final = 1013
+    SQLITE_DBCONFIG_ENABLE_FKEY: Final = 1002
+    SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER: Final = 1004
+    SQLITE_DBCONFIG_ENABLE_LOAD_EXTENSION: Final = 1005
+    SQLITE_DBCONFIG_ENABLE_QPSG: Final = 1007
+    SQLITE_DBCONFIG_ENABLE_TRIGGER: Final = 1003
+    SQLITE_DBCONFIG_ENABLE_VIEW: Final = 1015
+    SQLITE_DBCONFIG_LEGACY_ALTER_TABLE: Final = 1012
+    SQLITE_DBCONFIG_LEGACY_FILE_FORMAT: Final = 1016
+    SQLITE_DBCONFIG_NO_CKPT_ON_CLOSE: Final = 1006
+    SQLITE_DBCONFIG_RESET_DATABASE: Final = 1009
+    SQLITE_DBCONFIG_TRIGGER_EQP: Final = 1008
+    SQLITE_DBCONFIG_TRUSTED_SCHEMA: Final = 1017
+    SQLITE_DBCONFIG_WRITABLE_SCHEMA: Final = 1011
 
 if sys.version_info >= (3, 11):
-    SQLITE_ABORT: Final[int]
-    SQLITE_ABORT_ROLLBACK: Final[int]
-    SQLITE_AUTH: Final[int]
-    SQLITE_AUTH_USER: Final[int]
-    SQLITE_BUSY: Final[int]
-    SQLITE_BUSY_RECOVERY: Final[int]
-    SQLITE_BUSY_SNAPSHOT: Final[int]
-    SQLITE_BUSY_TIMEOUT: Final[int]
-    SQLITE_CANTOPEN: Final[int]
-    SQLITE_CANTOPEN_CONVPATH: Final[int]
-    SQLITE_CANTOPEN_DIRTYWAL: Final[int]
-    SQLITE_CANTOPEN_FULLPATH: Final[int]
-    SQLITE_CANTOPEN_ISDIR: Final[int]
-    SQLITE_CANTOPEN_NOTEMPDIR: Final[int]
-    SQLITE_CANTOPEN_SYMLINK: Final[int]
-    SQLITE_CONSTRAINT: Final[int]
-    SQLITE_CONSTRAINT_CHECK: Final[int]
-    SQLITE_CONSTRAINT_COMMITHOOK: Final[int]
-    SQLITE_CONSTRAINT_FOREIGNKEY: Final[int]
-    SQLITE_CONSTRAINT_FUNCTION: Final[int]
-    SQLITE_CONSTRAINT_NOTNULL: Final[int]
-    SQLITE_CONSTRAINT_PINNED: Final[int]
-    SQLITE_CONSTRAINT_PRIMARYKEY: Final[int]
-    SQLITE_CONSTRAINT_ROWID: Final[int]
-    SQLITE_CONSTRAINT_TRIGGER: Final[int]
-    SQLITE_CONSTRAINT_UNIQUE: Final[int]
-    SQLITE_CONSTRAINT_VTAB: Final[int]
-    SQLITE_CORRUPT: Final[int]
-    SQLITE_CORRUPT_INDEX: Final[int]
-    SQLITE_CORRUPT_SEQUENCE: Final[int]
-    SQLITE_CORRUPT_VTAB: Final[int]
-    SQLITE_EMPTY: Final[int]
-    SQLITE_ERROR: Final[int]
-    SQLITE_ERROR_MISSING_COLLSEQ: Final[int]
-    SQLITE_ERROR_RETRY: Final[int]
-    SQLITE_ERROR_SNAPSHOT: Final[int]
-    SQLITE_FORMAT: Final[int]
-    SQLITE_FULL: Final[int]
-    SQLITE_INTERNAL: Final[int]
-    SQLITE_INTERRUPT: Final[int]
-    SQLITE_IOERR: Final[int]
-    SQLITE_IOERR_ACCESS: Final[int]
-    SQLITE_IOERR_AUTH: Final[int]
-    SQLITE_IOERR_BEGIN_ATOMIC: Final[int]
-    SQLITE_IOERR_BLOCKED: Final[int]
-    SQLITE_IOERR_CHECKRESERVEDLOCK: Final[int]
-    SQLITE_IOERR_CLOSE: Final[int]
-    SQLITE_IOERR_COMMIT_ATOMIC: Final[int]
-    SQLITE_IOERR_CONVPATH: Final[int]
-    SQLITE_IOERR_CORRUPTFS: Final[int]
-    SQLITE_IOERR_DATA: Final[int]
-    SQLITE_IOERR_DELETE: Final[int]
-    SQLITE_IOERR_DELETE_NOENT: Final[int]
-    SQLITE_IOERR_DIR_CLOSE: Final[int]
-    SQLITE_IOERR_DIR_FSYNC: Final[int]
-    SQLITE_IOERR_FSTAT: Final[int]
-    SQLITE_IOERR_FSYNC: Final[int]
-    SQLITE_IOERR_GETTEMPPATH: Final[int]
-    SQLITE_IOERR_LOCK: Final[int]
-    SQLITE_IOERR_MMAP: Final[int]
-    SQLITE_IOERR_NOMEM: Final[int]
-    SQLITE_IOERR_RDLOCK: Final[int]
-    SQLITE_IOERR_READ: Final[int]
-    SQLITE_IOERR_ROLLBACK_ATOMIC: Final[int]
-    SQLITE_IOERR_SEEK: Final[int]
-    SQLITE_IOERR_SHMLOCK: Final[int]
-    SQLITE_IOERR_SHMMAP: Final[int]
-    SQLITE_IOERR_SHMOPEN: Final[int]
-    SQLITE_IOERR_SHMSIZE: Final[int]
-    SQLITE_IOERR_SHORT_READ: Final[int]
-    SQLITE_IOERR_TRUNCATE: Final[int]
-    SQLITE_IOERR_UNLOCK: Final[int]
-    SQLITE_IOERR_VNODE: Final[int]
-    SQLITE_IOERR_WRITE: Final[int]
-    SQLITE_LIMIT_ATTACHED: Final[int]
-    SQLITE_LIMIT_COLUMN: Final[int]
-    SQLITE_LIMIT_COMPOUND_SELECT: Final[int]
-    SQLITE_LIMIT_EXPR_DEPTH: Final[int]
-    SQLITE_LIMIT_FUNCTION_ARG: Final[int]
-    SQLITE_LIMIT_LENGTH: Final[int]
-    SQLITE_LIMIT_LIKE_PATTERN_LENGTH: Final[int]
-    SQLITE_LIMIT_SQL_LENGTH: Final[int]
-    SQLITE_LIMIT_TRIGGER_DEPTH: Final[int]
-    SQLITE_LIMIT_VARIABLE_NUMBER: Final[int]
-    SQLITE_LIMIT_VDBE_OP: Final[int]
-    SQLITE_LIMIT_WORKER_THREADS: Final[int]
-    SQLITE_LOCKED: Final[int]
-    SQLITE_LOCKED_SHAREDCACHE: Final[int]
-    SQLITE_LOCKED_VTAB: Final[int]
-    SQLITE_MISMATCH: Final[int]
-    SQLITE_MISUSE: Final[int]
-    SQLITE_NOLFS: Final[int]
-    SQLITE_NOMEM: Final[int]
-    SQLITE_NOTADB: Final[int]
-    SQLITE_NOTFOUND: Final[int]
-    SQLITE_NOTICE: Final[int]
-    SQLITE_NOTICE_RECOVER_ROLLBACK: Final[int]
-    SQLITE_NOTICE_RECOVER_WAL: Final[int]
-    SQLITE_OK_LOAD_PERMANENTLY: Final[int]
-    SQLITE_OK_SYMLINK: Final[int]
-    SQLITE_PERM: Final[int]
-    SQLITE_PROTOCOL: Final[int]
-    SQLITE_RANGE: Final[int]
-    SQLITE_READONLY: Final[int]
-    SQLITE_READONLY_CANTINIT: Final[int]
-    SQLITE_READONLY_CANTLOCK: Final[int]
-    SQLITE_READONLY_DBMOVED: Final[int]
-    SQLITE_READONLY_DIRECTORY: Final[int]
-    SQLITE_READONLY_RECOVERY: Final[int]
-    SQLITE_READONLY_ROLLBACK: Final[int]
-    SQLITE_ROW: Final[int]
-    SQLITE_SCHEMA: Final[int]
-    SQLITE_TOOBIG: Final[int]
-    SQLITE_WARNING: Final[int]
-    SQLITE_WARNING_AUTOINDEX: Final[int]
-    threadsafety: Final[int]
+    SQLITE_ABORT: Final = 4
+    SQLITE_ABORT_ROLLBACK: Final = 516
+    SQLITE_AUTH: Final = 23
+    SQLITE_AUTH_USER: Final = 279
+    SQLITE_BUSY: Final = 5
+    SQLITE_BUSY_RECOVERY: Final = 261
+    SQLITE_BUSY_SNAPSHOT: Final = 517
+    SQLITE_BUSY_TIMEOUT: Final = 773
+    SQLITE_CANTOPEN: Final = 14
+    SQLITE_CANTOPEN_CONVPATH: Final = 1038
+    SQLITE_CANTOPEN_DIRTYWAL: Final = 1294
+    SQLITE_CANTOPEN_FULLPATH: Final = 782
+    SQLITE_CANTOPEN_ISDIR: Final = 526
+    SQLITE_CANTOPEN_NOTEMPDIR: Final = 270
+    SQLITE_CANTOPEN_SYMLINK: Final = 1550
+    SQLITE_CONSTRAINT: Final = 19
+    SQLITE_CONSTRAINT_CHECK: Final = 275
+    SQLITE_CONSTRAINT_COMMITHOOK: Final = 531
+    SQLITE_CONSTRAINT_FOREIGNKEY: Final = 787
+    SQLITE_CONSTRAINT_FUNCTION: Final = 1043
+    SQLITE_CONSTRAINT_NOTNULL: Final = 1299
+    SQLITE_CONSTRAINT_PINNED: Final = 2835
+    SQLITE_CONSTRAINT_PRIMARYKEY: Final = 1555
+    SQLITE_CONSTRAINT_ROWID: Final = 2579
+    SQLITE_CONSTRAINT_TRIGGER: Final = 1811
+    SQLITE_CONSTRAINT_UNIQUE: Final = 2067
+    SQLITE_CONSTRAINT_VTAB: Final = 2323
+    SQLITE_CORRUPT: Final = 11
+    SQLITE_CORRUPT_INDEX: Final = 779
+    SQLITE_CORRUPT_SEQUENCE: Final = 523
+    SQLITE_CORRUPT_VTAB: Final = 267
+    SQLITE_EMPTY: Final = 16
+    SQLITE_ERROR: Final = 1
+    SQLITE_ERROR_MISSING_COLLSEQ: Final = 257
+    SQLITE_ERROR_RETRY: Final = 513
+    SQLITE_ERROR_SNAPSHOT: Final = 769
+    SQLITE_FORMAT: Final = 24
+    SQLITE_FULL: Final = 13
+    SQLITE_INTERNAL: Final = 2
+    SQLITE_INTERRUPT: Final = 9
+    SQLITE_IOERR: Final = 10
+    SQLITE_IOERR_ACCESS: Final = 3338
+    SQLITE_IOERR_AUTH: Final = 7178
+    SQLITE_IOERR_BEGIN_ATOMIC: Final = 7434
+    SQLITE_IOERR_BLOCKED: Final = 2826
+    SQLITE_IOERR_CHECKRESERVEDLOCK: Final = 3594
+    SQLITE_IOERR_CLOSE: Final = 4106
+    SQLITE_IOERR_COMMIT_ATOMIC: Final = 7690
+    SQLITE_IOERR_CONVPATH: Final = 6666
+    SQLITE_IOERR_CORRUPTFS: Final = 8458
+    SQLITE_IOERR_DATA: Final = 8202
+    SQLITE_IOERR_DELETE: Final = 2570
+    SQLITE_IOERR_DELETE_NOENT: Final = 5898
+    SQLITE_IOERR_DIR_CLOSE: Final = 4362
+    SQLITE_IOERR_DIR_FSYNC: Final = 1290
+    SQLITE_IOERR_FSTAT: Final = 1802
+    SQLITE_IOERR_FSYNC: Final = 1034
+    SQLITE_IOERR_GETTEMPPATH: Final = 6410
+    SQLITE_IOERR_LOCK: Final = 3850
+    SQLITE_IOERR_MMAP: Final = 6154
+    SQLITE_IOERR_NOMEM: Final = 3082
+    SQLITE_IOERR_RDLOCK: Final = 2314
+    SQLITE_IOERR_READ: Final = 266
+    SQLITE_IOERR_ROLLBACK_ATOMIC: Final = 7946
+    SQLITE_IOERR_SEEK: Final = 5642
+    SQLITE_IOERR_SHMLOCK: Final = 5130
+    SQLITE_IOERR_SHMMAP: Final = 5386
+    SQLITE_IOERR_SHMOPEN: Final = 4618
+    SQLITE_IOERR_SHMSIZE: Final = 4874
+    SQLITE_IOERR_SHORT_READ: Final = 522
+    SQLITE_IOERR_TRUNCATE: Final = 1546
+    SQLITE_IOERR_UNLOCK: Final = 2058
+    SQLITE_IOERR_VNODE: Final = 6922
+    SQLITE_IOERR_WRITE: Final = 778
+    SQLITE_LIMIT_ATTACHED: Final = 7
+    SQLITE_LIMIT_COLUMN: Final = 22
+    SQLITE_LIMIT_COMPOUND_SELECT: Final = 4
+    SQLITE_LIMIT_EXPR_DEPTH: Final = 3
+    SQLITE_LIMIT_FUNCTION_ARG: Final = 6
+    SQLITE_LIMIT_LENGTH: Final = 0
+    SQLITE_LIMIT_LIKE_PATTERN_LENGTH: Final = 8
+    SQLITE_LIMIT_SQL_LENGTH: Final = 1
+    SQLITE_LIMIT_TRIGGER_DEPTH: Final = 10
+    SQLITE_LIMIT_VARIABLE_NUMBER: Final = 9
+    SQLITE_LIMIT_VDBE_OP: Final = 5
+    SQLITE_LIMIT_WORKER_THREADS: Final = 11
+    SQLITE_LOCKED: Final = 6
+    SQLITE_LOCKED_SHAREDCACHE: Final = 262
+    SQLITE_LOCKED_VTAB: Final = 518
+    SQLITE_MISMATCH: Final = 20
+    SQLITE_MISUSE: Final = 21
+    SQLITE_NOLFS: Final = 22
+    SQLITE_NOMEM: Final = 7
+    SQLITE_NOTADB: Final = 26
+    SQLITE_NOTFOUND: Final = 12
+    SQLITE_NOTICE: Final = 27
+    SQLITE_NOTICE_RECOVER_ROLLBACK: Final = 539
+    SQLITE_NOTICE_RECOVER_WAL: Final = 283
+    SQLITE_OK_LOAD_PERMANENTLY: Final = 256
+    SQLITE_OK_SYMLINK: Final = 512
+    SQLITE_PERM: Final = 3
+    SQLITE_PROTOCOL: Final = 15
+    SQLITE_RANGE: Final = 25
+    SQLITE_READONLY: Final = 8
+    SQLITE_READONLY_CANTINIT: Final = 1288
+    SQLITE_READONLY_CANTLOCK: Final = 520
+    SQLITE_READONLY_DBMOVED: Final = 1032
+    SQLITE_READONLY_DIRECTORY: Final = 1544
+    SQLITE_READONLY_RECOVERY: Final = 264
+    SQLITE_READONLY_ROLLBACK: Final = 776
+    SQLITE_ROW: Final = 100
+    SQLITE_SCHEMA: Final = 17
+    SQLITE_TOOBIG: Final = 18
+    SQLITE_WARNING: Final = 28
+    SQLITE_WARNING_AUTOINDEX: Final = 284
+    threadsafety: Literal[0, 1, 3]
 
 # Can take or return anything depending on what's in the registry.
 @overload
@@ -225,7 +226,7 @@ if sys.version_info >= (3, 12):
         database: StrOrBytesPath,
         timeout: float = 5.0,
         detect_types: int = 0,
-        isolation_level: Literal["DEFERRED", "EXCLUSIVE", "IMMEDIATE"] | None = "DEFERRED",
+        isolation_level: _IsolationLevel = "DEFERRED",
         check_same_thread: bool = True,
         cached_statements: int = 128,
         uri: bool = False,
@@ -237,7 +238,7 @@ if sys.version_info >= (3, 12):
         database: StrOrBytesPath,
         timeout: float,
         detect_types: int,
-        isolation_level: Literal["DEFERRED", "EXCLUSIVE", "IMMEDIATE"] | None,
+        isolation_level: _IsolationLevel,
         check_same_thread: bool,
         factory: type[_ConnectionT],
         cached_statements: int = 128,
@@ -250,7 +251,7 @@ if sys.version_info >= (3, 12):
         database: StrOrBytesPath,
         timeout: float = 5.0,
         detect_types: int = 0,
-        isolation_level: Literal["DEFERRED", "EXCLUSIVE", "IMMEDIATE"] | None = "DEFERRED",
+        isolation_level: _IsolationLevel = "DEFERRED",
         check_same_thread: bool = True,
         *,
         factory: type[_ConnectionT],
@@ -265,7 +266,7 @@ else:
         database: StrOrBytesPath,
         timeout: float = 5.0,
         detect_types: int = 0,
-        isolation_level: Literal["DEFERRED", "EXCLUSIVE", "IMMEDIATE"] | None = "DEFERRED",
+        isolation_level: _IsolationLevel = "DEFERRED",
         check_same_thread: bool = True,
         cached_statements: int = 128,
         uri: bool = False,
@@ -275,7 +276,7 @@ else:
         database: StrOrBytesPath,
         timeout: float,
         detect_types: int,
-        isolation_level: Literal["DEFERRED", "EXCLUSIVE", "IMMEDIATE"] | None,
+        isolation_level: _IsolationLevel,
         check_same_thread: bool,
         factory: type[_ConnectionT],
         cached_statements: int = 128,
@@ -286,7 +287,7 @@ else:
         database: StrOrBytesPath,
         timeout: float = 5.0,
         detect_types: int = 0,
-        isolation_level: Literal["DEFERRED", "EXCLUSIVE", "IMMEDIATE"] | None = "DEFERRED",
+        isolation_level: _IsolationLevel = "DEFERRED",
         check_same_thread: bool = True,
         *,
         factory: type[_ConnectionT],
diff --git a/mypy/typeshed/stdlib/_ssl.pyi b/mypy/typeshed/stdlib/_ssl.pyi
index 7ab880e4def7..73a43f29c8c5 100644
--- a/mypy/typeshed/stdlib/_ssl.pyi
+++ b/mypy/typeshed/stdlib/_ssl.pyi
@@ -12,14 +12,15 @@ from ssl import (
     SSLWantWriteError as SSLWantWriteError,
     SSLZeroReturnError as SSLZeroReturnError,
 )
-from typing import Any, ClassVar, Literal, TypedDict, final, overload
-from typing_extensions import NotRequired, Self, TypeAlias
+from typing import Any, ClassVar, Final, Literal, TypedDict, final, overload, type_check_only
+from typing_extensions import NotRequired, Self, TypeAlias, deprecated, disjoint_base
 
 _PasswordType: TypeAlias = Callable[[], str | bytes | bytearray] | str | bytes | bytearray
 _PCTRTT: TypeAlias = tuple[tuple[str, str], ...]
 _PCTRTTT: TypeAlias = tuple[_PCTRTT, ...]
 _PeerCertRetDictType: TypeAlias = dict[str, str | _PCTRTTT | _PCTRTT]
 
+@type_check_only
 class _Cipher(TypedDict):
     aead: bool
     alg_bits: int
@@ -33,6 +34,7 @@ class _Cipher(TypedDict):
     strength_bits: int
     symmetric: str
 
+@type_check_only
 class _CertInfo(TypedDict):
     subject: tuple[tuple[tuple[str, str], ...], ...]
     issuer: tuple[tuple[tuple[str, str], ...], ...]
@@ -49,6 +51,7 @@ def RAND_add(string: str | ReadableBuffer, entropy: float, /) -> None: ...
 def RAND_bytes(n: int, /) -> bytes: ...
 
 if sys.version_info < (3, 12):
+    @deprecated("Deprecated since Python 3.6; removed in Python 3.12. Use `ssl.RAND_bytes()` instead.")
     def RAND_pseudo_bytes(n: int, /) -> tuple[bytes, bool]: ...
 
 if sys.version_info < (3, 10):
@@ -64,7 +67,7 @@ if sys.platform == "win32":
 
 def txt2obj(txt: str, name: bool = False) -> tuple[int, str, str, str]: ...
 def nid2obj(nid: int, /) -> tuple[int, str, str, str]: ...
-
+@disjoint_base
 class _SSLContext:
     check_hostname: bool
     keylog_filename: str | None
@@ -159,135 +162,134 @@ if sys.version_info < (3, 12):
     err_names_to_codes: dict[str, tuple[int, int]]
     lib_codes_to_names: dict[int, str]
 
-_DEFAULT_CIPHERS: str
+_DEFAULT_CIPHERS: Final[str]
 
 # SSL error numbers
-SSL_ERROR_ZERO_RETURN: int
-SSL_ERROR_WANT_READ: int
-SSL_ERROR_WANT_WRITE: int
-SSL_ERROR_WANT_X509_LOOKUP: int
-SSL_ERROR_SYSCALL: int
-SSL_ERROR_SSL: int
-SSL_ERROR_WANT_CONNECT: int
-SSL_ERROR_EOF: int
-SSL_ERROR_INVALID_ERROR_CODE: int
+SSL_ERROR_ZERO_RETURN: Final = 6
+SSL_ERROR_WANT_READ: Final = 2
+SSL_ERROR_WANT_WRITE: Final = 3
+SSL_ERROR_WANT_X509_LOOKUP: Final = 4
+SSL_ERROR_SYSCALL: Final = 5
+SSL_ERROR_SSL: Final = 1
+SSL_ERROR_WANT_CONNECT: Final = 7
+SSL_ERROR_EOF: Final = 8
+SSL_ERROR_INVALID_ERROR_CODE: Final = 10
 
 # verify modes
-CERT_NONE: int
-CERT_OPTIONAL: int
-CERT_REQUIRED: int
+CERT_NONE: Final = 0
+CERT_OPTIONAL: Final = 1
+CERT_REQUIRED: Final = 2
 
 # verify flags
-VERIFY_DEFAULT: int
-VERIFY_CRL_CHECK_LEAF: int
-VERIFY_CRL_CHECK_CHAIN: int
-VERIFY_X509_STRICT: int
-VERIFY_X509_TRUSTED_FIRST: int
+VERIFY_DEFAULT: Final = 0
+VERIFY_CRL_CHECK_LEAF: Final = 0x4
+VERIFY_CRL_CHECK_CHAIN: Final = 0x8
+VERIFY_X509_STRICT: Final = 0x20
+VERIFY_X509_TRUSTED_FIRST: Final = 0x8000
 if sys.version_info >= (3, 10):
-    VERIFY_ALLOW_PROXY_CERTS: int
-    VERIFY_X509_PARTIAL_CHAIN: int
+    VERIFY_ALLOW_PROXY_CERTS: Final = 0x40
+    VERIFY_X509_PARTIAL_CHAIN: Final = 0x80000
 
 # alert descriptions
-ALERT_DESCRIPTION_CLOSE_NOTIFY: int
-ALERT_DESCRIPTION_UNEXPECTED_MESSAGE: int
-ALERT_DESCRIPTION_BAD_RECORD_MAC: int
-ALERT_DESCRIPTION_RECORD_OVERFLOW: int
-ALERT_DESCRIPTION_DECOMPRESSION_FAILURE: int
-ALERT_DESCRIPTION_HANDSHAKE_FAILURE: int
-ALERT_DESCRIPTION_BAD_CERTIFICATE: int
-ALERT_DESCRIPTION_UNSUPPORTED_CERTIFICATE: int
-ALERT_DESCRIPTION_CERTIFICATE_REVOKED: int
-ALERT_DESCRIPTION_CERTIFICATE_EXPIRED: int
-ALERT_DESCRIPTION_CERTIFICATE_UNKNOWN: int
-ALERT_DESCRIPTION_ILLEGAL_PARAMETER: int
-ALERT_DESCRIPTION_UNKNOWN_CA: int
-ALERT_DESCRIPTION_ACCESS_DENIED: int
-ALERT_DESCRIPTION_DECODE_ERROR: int
-ALERT_DESCRIPTION_DECRYPT_ERROR: int
-ALERT_DESCRIPTION_PROTOCOL_VERSION: int
-ALERT_DESCRIPTION_INSUFFICIENT_SECURITY: int
-ALERT_DESCRIPTION_INTERNAL_ERROR: int
-ALERT_DESCRIPTION_USER_CANCELLED: int
-ALERT_DESCRIPTION_NO_RENEGOTIATION: int
-ALERT_DESCRIPTION_UNSUPPORTED_EXTENSION: int
-ALERT_DESCRIPTION_CERTIFICATE_UNOBTAINABLE: int
-ALERT_DESCRIPTION_UNRECOGNIZED_NAME: int
-ALERT_DESCRIPTION_BAD_CERTIFICATE_STATUS_RESPONSE: int
-ALERT_DESCRIPTION_BAD_CERTIFICATE_HASH_VALUE: int
-ALERT_DESCRIPTION_UNKNOWN_PSK_IDENTITY: int
+ALERT_DESCRIPTION_CLOSE_NOTIFY: Final = 0
+ALERT_DESCRIPTION_UNEXPECTED_MESSAGE: Final = 10
+ALERT_DESCRIPTION_BAD_RECORD_MAC: Final = 20
+ALERT_DESCRIPTION_RECORD_OVERFLOW: Final = 22
+ALERT_DESCRIPTION_DECOMPRESSION_FAILURE: Final = 30
+ALERT_DESCRIPTION_HANDSHAKE_FAILURE: Final = 40
+ALERT_DESCRIPTION_BAD_CERTIFICATE: Final = 42
+ALERT_DESCRIPTION_UNSUPPORTED_CERTIFICATE: Final = 43
+ALERT_DESCRIPTION_CERTIFICATE_REVOKED: Final = 44
+ALERT_DESCRIPTION_CERTIFICATE_EXPIRED: Final = 45
+ALERT_DESCRIPTION_CERTIFICATE_UNKNOWN: Final = 46
+ALERT_DESCRIPTION_ILLEGAL_PARAMETER: Final = 47
+ALERT_DESCRIPTION_UNKNOWN_CA: Final = 48
+ALERT_DESCRIPTION_ACCESS_DENIED: Final = 49
+ALERT_DESCRIPTION_DECODE_ERROR: Final = 50
+ALERT_DESCRIPTION_DECRYPT_ERROR: Final = 51
+ALERT_DESCRIPTION_PROTOCOL_VERSION: Final = 70
+ALERT_DESCRIPTION_INSUFFICIENT_SECURITY: Final = 71
+ALERT_DESCRIPTION_INTERNAL_ERROR: Final = 80
+ALERT_DESCRIPTION_USER_CANCELLED: Final = 90
+ALERT_DESCRIPTION_NO_RENEGOTIATION: Final = 100
+ALERT_DESCRIPTION_UNSUPPORTED_EXTENSION: Final = 110
+ALERT_DESCRIPTION_CERTIFICATE_UNOBTAINABLE: Final = 111
+ALERT_DESCRIPTION_UNRECOGNIZED_NAME: Final = 112
+ALERT_DESCRIPTION_BAD_CERTIFICATE_STATUS_RESPONSE: Final = 113
+ALERT_DESCRIPTION_BAD_CERTIFICATE_HASH_VALUE: Final = 114
+ALERT_DESCRIPTION_UNKNOWN_PSK_IDENTITY: Final = 115
 
 # protocol versions
-PROTOCOL_SSLv23: int
-PROTOCOL_TLS: int
-PROTOCOL_TLS_CLIENT: int
-PROTOCOL_TLS_SERVER: int
-PROTOCOL_TLSv1: int
-PROTOCOL_TLSv1_1: int
-PROTOCOL_TLSv1_2: int
+PROTOCOL_SSLv23: Final = 2
+PROTOCOL_TLS: Final = 2
+PROTOCOL_TLS_CLIENT: Final = 16
+PROTOCOL_TLS_SERVER: Final = 17
+PROTOCOL_TLSv1: Final = 3
+PROTOCOL_TLSv1_1: Final = 4
+PROTOCOL_TLSv1_2: Final = 5
 
 # protocol options
-OP_ALL: int
-OP_NO_SSLv2: int
-OP_NO_SSLv3: int
-OP_NO_TLSv1: int
-OP_NO_TLSv1_1: int
-OP_NO_TLSv1_2: int
-OP_NO_TLSv1_3: int
-OP_CIPHER_SERVER_PREFERENCE: int
-OP_SINGLE_DH_USE: int
-OP_NO_TICKET: int
-OP_SINGLE_ECDH_USE: int
-OP_NO_COMPRESSION: int
-OP_ENABLE_MIDDLEBOX_COMPAT: int
-OP_NO_RENEGOTIATION: int
+OP_ALL: Final = 0x80000050
+OP_NO_SSLv2: Final = 0x0
+OP_NO_SSLv3: Final = 0x2000000
+OP_NO_TLSv1: Final = 0x4000000
+OP_NO_TLSv1_1: Final = 0x10000000
+OP_NO_TLSv1_2: Final = 0x8000000
+OP_NO_TLSv1_3: Final = 0x20000000
+OP_CIPHER_SERVER_PREFERENCE: Final = 0x400000
+OP_SINGLE_DH_USE: Final = 0x0
+OP_NO_TICKET: Final = 0x4000
+OP_SINGLE_ECDH_USE: Final = 0x0
+OP_NO_COMPRESSION: Final = 0x20000
+OP_ENABLE_MIDDLEBOX_COMPAT: Final = 0x100000
+OP_NO_RENEGOTIATION: Final = 0x40000000
 if sys.version_info >= (3, 11) or sys.platform == "linux":
-    OP_IGNORE_UNEXPECTED_EOF: int
+    OP_IGNORE_UNEXPECTED_EOF: Final = 0x80
 if sys.version_info >= (3, 12):
-    OP_LEGACY_SERVER_CONNECT: int
-    OP_ENABLE_KTLS: int
+    OP_LEGACY_SERVER_CONNECT: Final = 0x4
+    OP_ENABLE_KTLS: Final = 0x8
 
 # host flags
-HOSTFLAG_ALWAYS_CHECK_SUBJECT: int
-HOSTFLAG_NEVER_CHECK_SUBJECT: int
-HOSTFLAG_NO_WILDCARDS: int
-HOSTFLAG_NO_PARTIAL_WILDCARDS: int
-HOSTFLAG_MULTI_LABEL_WILDCARDS: int
-HOSTFLAG_SINGLE_LABEL_SUBDOMAINS: int
+HOSTFLAG_ALWAYS_CHECK_SUBJECT: Final = 0x1
+HOSTFLAG_NEVER_CHECK_SUBJECT: Final = 0x20
+HOSTFLAG_NO_WILDCARDS: Final = 0x2
+HOSTFLAG_NO_PARTIAL_WILDCARDS: Final = 0x4
+HOSTFLAG_MULTI_LABEL_WILDCARDS: Final = 0x8
+HOSTFLAG_SINGLE_LABEL_SUBDOMAINS: Final = 0x10
 
 if sys.version_info >= (3, 10):
     # certificate file types
-    # Typed as Literal so the overload on Certificate.public_bytes can work properly.
-    ENCODING_PEM: Literal[1]
-    ENCODING_DER: Literal[2]
+    ENCODING_PEM: Final = 1
+    ENCODING_DER: Final = 2
 
 # protocol versions
-PROTO_MINIMUM_SUPPORTED: int
-PROTO_MAXIMUM_SUPPORTED: int
-PROTO_SSLv3: int
-PROTO_TLSv1: int
-PROTO_TLSv1_1: int
-PROTO_TLSv1_2: int
-PROTO_TLSv1_3: int
+PROTO_MINIMUM_SUPPORTED: Final = -2
+PROTO_MAXIMUM_SUPPORTED: Final = -1
+PROTO_SSLv3: Final[int]
+PROTO_TLSv1: Final[int]
+PROTO_TLSv1_1: Final[int]
+PROTO_TLSv1_2: Final[int]
+PROTO_TLSv1_3: Final[int]
 
 # feature support
-HAS_SNI: bool
-HAS_TLS_UNIQUE: bool
-HAS_ECDH: bool
-HAS_NPN: bool
+HAS_SNI: Final[bool]
+HAS_TLS_UNIQUE: Final[bool]
+HAS_ECDH: Final[bool]
+HAS_NPN: Final[bool]
 if sys.version_info >= (3, 13):
-    HAS_PSK: bool
-HAS_ALPN: bool
-HAS_SSLv2: bool
-HAS_SSLv3: bool
-HAS_TLSv1: bool
-HAS_TLSv1_1: bool
-HAS_TLSv1_2: bool
-HAS_TLSv1_3: bool
+    HAS_PSK: Final[bool]
+HAS_ALPN: Final[bool]
+HAS_SSLv2: Final[bool]
+HAS_SSLv3: Final[bool]
+HAS_TLSv1: Final[bool]
+HAS_TLSv1_1: Final[bool]
+HAS_TLSv1_2: Final[bool]
+HAS_TLSv1_3: Final[bool]
 if sys.version_info >= (3, 14):
-    HAS_PHA: bool
+    HAS_PHA: Final[bool]
 
 # version info
-OPENSSL_VERSION_NUMBER: int
-OPENSSL_VERSION_INFO: tuple[int, int, int, int, int]
-OPENSSL_VERSION: str
-_OPENSSL_API_VERSION: tuple[int, int, int, int, int]
+OPENSSL_VERSION_NUMBER: Final[int]
+OPENSSL_VERSION_INFO: Final[tuple[int, int, int, int, int]]
+OPENSSL_VERSION: Final[str]
+_OPENSSL_API_VERSION: Final[tuple[int, int, int, int, int]]
diff --git a/mypy/typeshed/stdlib/_struct.pyi b/mypy/typeshed/stdlib/_struct.pyi
index 662170e869f3..a8fac2aea1b0 100644
--- a/mypy/typeshed/stdlib/_struct.pyi
+++ b/mypy/typeshed/stdlib/_struct.pyi
@@ -1,6 +1,7 @@
 from _typeshed import ReadableBuffer, WriteableBuffer
 from collections.abc import Iterator
 from typing import Any
+from typing_extensions import disjoint_base
 
 def pack(fmt: str | bytes, /, *v: Any) -> bytes: ...
 def pack_into(fmt: str | bytes, buffer: WriteableBuffer, offset: int, /, *v: Any) -> None: ...
@@ -8,7 +9,7 @@ def unpack(format: str | bytes, buffer: ReadableBuffer, /) -> tuple[Any, ...]: .
 def unpack_from(format: str | bytes, /, buffer: ReadableBuffer, offset: int = 0) -> tuple[Any, ...]: ...
 def iter_unpack(format: str | bytes, buffer: ReadableBuffer, /) -> Iterator[tuple[Any, ...]]: ...
 def calcsize(format: str | bytes, /) -> int: ...
-
+@disjoint_base
 class Struct:
     @property
     def format(self) -> str: ...
diff --git a/mypy/typeshed/stdlib/_thread.pyi b/mypy/typeshed/stdlib/_thread.pyi
index 9cfbe55b4fe3..6969ae48cae7 100644
--- a/mypy/typeshed/stdlib/_thread.pyi
+++ b/mypy/typeshed/stdlib/_thread.pyi
@@ -5,7 +5,7 @@ from collections.abc import Callable
 from threading import Thread
 from types import TracebackType
 from typing import Any, Final, NoReturn, final, overload
-from typing_extensions import TypeVarTuple, Unpack
+from typing_extensions import TypeVarTuple, Unpack, disjoint_base
 
 _Ts = TypeVarTuple("_Ts")
 
@@ -73,7 +73,7 @@ def start_new(function: Callable[[Unpack[_Ts]], object], args: tuple[Unpack[_Ts]
 def start_new(function: Callable[..., object], args: tuple[Any, ...], kwargs: dict[str, Any], /) -> int: ...
 
 if sys.version_info >= (3, 10):
-    def interrupt_main(signum: signal.Signals = ..., /) -> None: ...
+    def interrupt_main(signum: signal.Signals = signal.SIGINT, /) -> None: ...
 
 else:
     def interrupt_main() -> None: ...
@@ -85,7 +85,7 @@ def allocate() -> LockType: ...  # Obsolete synonym for allocate_lock()
 def get_ident() -> int: ...
 def stack_size(size: int = 0, /) -> int: ...
 
-TIMEOUT_MAX: float
+TIMEOUT_MAX: Final[float]
 
 def get_native_id() -> int: ...  # only available on some platforms
 @final
@@ -110,6 +110,7 @@ if sys.version_info >= (3, 12):
 if sys.version_info >= (3, 14):
     def set_name(name: str) -> None: ...
 
+@disjoint_base
 class _local:
     def __getattribute__(self, name: str, /) -> Any: ...
     def __setattr__(self, name: str, value: Any, /) -> None: ...
diff --git a/mypy/typeshed/stdlib/_threading_local.pyi b/mypy/typeshed/stdlib/_threading_local.pyi
index 07a825f0d816..5f6acaf840aa 100644
--- a/mypy/typeshed/stdlib/_threading_local.pyi
+++ b/mypy/typeshed/stdlib/_threading_local.pyi
@@ -7,6 +7,7 @@ __all__ = ["local"]
 _LocalDict: TypeAlias = dict[Any, Any]
 
 class _localimpl:
+    __slots__ = ("key", "dicts", "localargs", "locallock", "__weakref__")
     key: str
     dicts: dict[int, tuple[ReferenceType[Any], _LocalDict]]
     # Keep localargs in sync with the *args, **kwargs annotation on local.__new__
@@ -16,6 +17,7 @@ class _localimpl:
     def create_dict(self) -> _LocalDict: ...
 
 class local:
+    __slots__ = ("_local__impl", "__dict__")
     def __new__(cls, /, *args: Any, **kw: Any) -> Self: ...
     def __getattribute__(self, name: str) -> Any: ...
     def __setattr__(self, name: str, value: Any) -> None: ...
diff --git a/mypy/typeshed/stdlib/_tkinter.pyi b/mypy/typeshed/stdlib/_tkinter.pyi
index 08eb00ca442b..46366ccc1740 100644
--- a/mypy/typeshed/stdlib/_tkinter.pyi
+++ b/mypy/typeshed/stdlib/_tkinter.pyi
@@ -1,7 +1,7 @@
 import sys
 from collections.abc import Callable
 from typing import Any, ClassVar, Final, final
-from typing_extensions import TypeAlias
+from typing_extensions import TypeAlias, deprecated
 
 # _tkinter is meant to be only used internally by tkinter, but some tkinter
 # functions e.g. return _tkinter.Tcl_Obj objects. Tcl_Obj represents a Tcl
@@ -84,6 +84,7 @@ class TkappType:
     def record(self, script, /): ...
     def setvar(self, *ags, **kwargs): ...
     if sys.version_info < (3, 11):
+        @deprecated("Deprecated since Python 3.9; removed in Python 3.11. Use `splitlist()` instead.")
         def split(self, arg, /): ...
 
     def splitlist(self, arg, /): ...
diff --git a/mypy/typeshed/stdlib/_typeshed/__init__.pyi b/mypy/typeshed/stdlib/_typeshed/__init__.pyi
index f322244016dd..25054b601a4f 100644
--- a/mypy/typeshed/stdlib/_typeshed/__init__.pyi
+++ b/mypy/typeshed/stdlib/_typeshed/__init__.pyi
@@ -3,7 +3,7 @@
 # See the README.md file in this directory for more information.
 
 import sys
-from collections.abc import Awaitable, Callable, Iterable, Sequence, Set as AbstractSet, Sized
+from collections.abc import Awaitable, Callable, Iterable, Iterator, Sequence, Set as AbstractSet, Sized
 from dataclasses import Field
 from os import PathLike
 from types import FrameType, TracebackType
@@ -54,7 +54,8 @@ Unused: TypeAlias = object  # stable
 
 # Marker for return types that include None, but where forcing the user to
 # check for None can be detrimental. Sometimes called "the Any trick". See
-# CONTRIBUTING.md for more information.
+# https://typing.python.org/en/latest/guides/writing_stubs.html#the-any-trick
+# for more information.
 MaybeNone: TypeAlias = Any  # stable
 
 # Used to mark arguments that default to a sentinel value. This prevents
@@ -65,10 +66,10 @@ MaybeNone: TypeAlias = Any  # stable
 # In cases where the sentinel object is exported and can be used by user code,
 # a construct like this is better:
 #
-# _SentinelType = NewType("_SentinelType", object)
-# sentinel: _SentinelType
+# _SentinelType = NewType("_SentinelType", object)  # does not exist at runtime
+# sentinel: Final[_SentinelType]
 # def foo(x: int | None | _SentinelType = ...) -> None: ...
-sentinel: Any
+sentinel: Any  # stable
 
 # stable
 class IdentityFunction(Protocol):
@@ -82,19 +83,21 @@ class SupportsNext(Protocol[_T_co]):
 class SupportsAnext(Protocol[_T_co]):
     def __anext__(self) -> Awaitable[_T_co]: ...
 
-# Comparison protocols
+class SupportsBool(Protocol):
+    def __bool__(self) -> bool: ...
 
+# Comparison protocols
 class SupportsDunderLT(Protocol[_T_contra]):
-    def __lt__(self, other: _T_contra, /) -> bool: ...
+    def __lt__(self, other: _T_contra, /) -> SupportsBool: ...
 
 class SupportsDunderGT(Protocol[_T_contra]):
-    def __gt__(self, other: _T_contra, /) -> bool: ...
+    def __gt__(self, other: _T_contra, /) -> SupportsBool: ...
 
 class SupportsDunderLE(Protocol[_T_contra]):
-    def __le__(self, other: _T_contra, /) -> bool: ...
+    def __le__(self, other: _T_contra, /) -> SupportsBool: ...
 
 class SupportsDunderGE(Protocol[_T_contra]):
-    def __ge__(self, other: _T_contra, /) -> bool: ...
+    def __ge__(self, other: _T_contra, /) -> SupportsBool: ...
 
 class SupportsAllComparisons(
     SupportsDunderLT[Any], SupportsDunderGT[Any], SupportsDunderLE[Any], SupportsDunderGE[Any], Protocol
@@ -273,6 +276,16 @@ class SupportsWrite(Protocol[_T_contra]):
 class SupportsFlush(Protocol):
     def flush(self) -> object: ...
 
+# Suitable for dictionary view objects
+class Viewable(Protocol[_T_co]):
+    def __len__(self) -> int: ...
+    def __iter__(self) -> Iterator[_T_co]: ...
+
+class SupportsGetItemViewable(Protocol[_KT, _VT_co]):
+    def __len__(self) -> int: ...
+    def __iter__(self) -> Iterator[_KT]: ...
+    def __getitem__(self, key: _KT, /) -> _VT_co: ...
+
 # Unfortunately PEP 688 does not allow us to distinguish read-only
 # from writable buffers. We use these aliases for readability for now.
 # Perhaps a future extension of the buffer protocol will allow us to
diff --git a/mypy/typeshed/stdlib/_warnings.pyi b/mypy/typeshed/stdlib/_warnings.pyi
index 2e571e676c97..2dbc7b855281 100644
--- a/mypy/typeshed/stdlib/_warnings.pyi
+++ b/mypy/typeshed/stdlib/_warnings.pyi
@@ -38,9 +38,9 @@ def warn_explicit(
     filename: str,
     lineno: int,
     module: str | None = ...,
-    registry: dict[str | tuple[str, type[Warning], int], int] | None = ...,
-    module_globals: dict[str, Any] | None = ...,
-    source: Any | None = ...,
+    registry: dict[str | tuple[str, type[Warning], int], int] | None = None,
+    module_globals: dict[str, Any] | None = None,
+    source: Any | None = None,
 ) -> None: ...
 @overload
 def warn_explicit(
@@ -48,8 +48,8 @@ def warn_explicit(
     category: Any,
     filename: str,
     lineno: int,
-    module: str | None = ...,
-    registry: dict[str | tuple[str, type[Warning], int], int] | None = ...,
-    module_globals: dict[str, Any] | None = ...,
-    source: Any | None = ...,
+    module: str | None = None,
+    registry: dict[str | tuple[str, type[Warning], int], int] | None = None,
+    module_globals: dict[str, Any] | None = None,
+    source: Any | None = None,
 ) -> None: ...
diff --git a/mypy/typeshed/stdlib/_winapi.pyi b/mypy/typeshed/stdlib/_winapi.pyi
index 0f71a0687748..d9e2c377b115 100644
--- a/mypy/typeshed/stdlib/_winapi.pyi
+++ b/mypy/typeshed/stdlib/_winapi.pyi
@@ -128,21 +128,21 @@ if sys.platform == "win32":
     WAIT_TIMEOUT: Final = 258
 
     if sys.version_info >= (3, 10):
-        LOCALE_NAME_INVARIANT: str
-        LOCALE_NAME_MAX_LENGTH: int
-        LOCALE_NAME_SYSTEM_DEFAULT: str
-        LOCALE_NAME_USER_DEFAULT: str | None
+        LOCALE_NAME_INVARIANT: Final[str]
+        LOCALE_NAME_MAX_LENGTH: Final[int]
+        LOCALE_NAME_SYSTEM_DEFAULT: Final[str]
+        LOCALE_NAME_USER_DEFAULT: Final[str | None]
 
-        LCMAP_FULLWIDTH: int
-        LCMAP_HALFWIDTH: int
-        LCMAP_HIRAGANA: int
-        LCMAP_KATAKANA: int
-        LCMAP_LINGUISTIC_CASING: int
-        LCMAP_LOWERCASE: int
-        LCMAP_SIMPLIFIED_CHINESE: int
-        LCMAP_TITLECASE: int
-        LCMAP_TRADITIONAL_CHINESE: int
-        LCMAP_UPPERCASE: int
+        LCMAP_FULLWIDTH: Final[int]
+        LCMAP_HALFWIDTH: Final[int]
+        LCMAP_HIRAGANA: Final[int]
+        LCMAP_KATAKANA: Final[int]
+        LCMAP_LINGUISTIC_CASING: Final[int]
+        LCMAP_LOWERCASE: Final[int]
+        LCMAP_SIMPLIFIED_CHINESE: Final[int]
+        LCMAP_TITLECASE: Final[int]
+        LCMAP_TRADITIONAL_CHINESE: Final[int]
+        LCMAP_UPPERCASE: Final[int]
 
     if sys.version_info >= (3, 12):
         COPYFILE2_CALLBACK_CHUNK_STARTED: Final = 1
@@ -172,6 +172,9 @@ if sys.platform == "win32":
         ERROR_ACCESS_DENIED: Final = 5
         ERROR_PRIVILEGE_NOT_HELD: Final = 1314
 
+    if sys.version_info >= (3, 14):
+        COPY_FILE_DIRECTORY: Final = 0x00000080
+
     def CloseHandle(handle: int, /) -> None: ...
     @overload
     def ConnectNamedPipe(handle: int, overlapped: Literal[True]) -> Overlapped: ...
diff --git a/mypy/typeshed/stdlib/_zstd.pyi b/mypy/typeshed/stdlib/_zstd.pyi
new file mode 100644
index 000000000000..f5e98ef88bb9
--- /dev/null
+++ b/mypy/typeshed/stdlib/_zstd.pyi
@@ -0,0 +1,97 @@
+from _typeshed import ReadableBuffer
+from collections.abc import Mapping
+from compression.zstd import CompressionParameter, DecompressionParameter
+from typing import Final, Literal, final
+from typing_extensions import Self, TypeAlias
+
+ZSTD_CLEVEL_DEFAULT: Final = 3
+ZSTD_DStreamOutSize: Final = 131072
+ZSTD_btlazy2: Final = 6
+ZSTD_btopt: Final = 7
+ZSTD_btultra: Final = 8
+ZSTD_btultra2: Final = 9
+ZSTD_c_chainLog: Final = 103
+ZSTD_c_checksumFlag: Final = 201
+ZSTD_c_compressionLevel: Final = 100
+ZSTD_c_contentSizeFlag: Final = 200
+ZSTD_c_dictIDFlag: Final = 202
+ZSTD_c_enableLongDistanceMatching: Final = 160
+ZSTD_c_hashLog: Final = 102
+ZSTD_c_jobSize: Final = 401
+ZSTD_c_ldmBucketSizeLog: Final = 163
+ZSTD_c_ldmHashLog: Final = 161
+ZSTD_c_ldmHashRateLog: Final = 164
+ZSTD_c_ldmMinMatch: Final = 162
+ZSTD_c_minMatch: Final = 105
+ZSTD_c_nbWorkers: Final = 400
+ZSTD_c_overlapLog: Final = 402
+ZSTD_c_searchLog: Final = 104
+ZSTD_c_strategy: Final = 107
+ZSTD_c_targetLength: Final = 106
+ZSTD_c_windowLog: Final = 101
+ZSTD_d_windowLogMax: Final = 100
+ZSTD_dfast: Final = 2
+ZSTD_fast: Final = 1
+ZSTD_greedy: Final = 3
+ZSTD_lazy: Final = 4
+ZSTD_lazy2: Final = 5
+
+_ZstdCompressorContinue: TypeAlias = Literal[0]
+_ZstdCompressorFlushBlock: TypeAlias = Literal[1]
+_ZstdCompressorFlushFrame: TypeAlias = Literal[2]
+
+@final
+class ZstdCompressor:
+    CONTINUE: Final = 0
+    FLUSH_BLOCK: Final = 1
+    FLUSH_FRAME: Final = 2
+    def __new__(
+        cls, level: int | None = None, options: Mapping[int, int] | None = None, zstd_dict: ZstdDict | None = None
+    ) -> Self: ...
+    def compress(
+        self, /, data: ReadableBuffer, mode: _ZstdCompressorContinue | _ZstdCompressorFlushBlock | _ZstdCompressorFlushFrame = 0
+    ) -> bytes: ...
+    def flush(self, /, mode: _ZstdCompressorFlushBlock | _ZstdCompressorFlushFrame = 2) -> bytes: ...
+    def set_pledged_input_size(self, size: int | None, /) -> None: ...
+    @property
+    def last_mode(self) -> _ZstdCompressorContinue | _ZstdCompressorFlushBlock | _ZstdCompressorFlushFrame: ...
+
+@final
+class ZstdDecompressor:
+    def __new__(cls, zstd_dict: ZstdDict | None = None, options: Mapping[int, int] | None = None) -> Self: ...
+    def decompress(self, /, data: ReadableBuffer, max_length: int = -1) -> bytes: ...
+    @property
+    def eof(self) -> bool: ...
+    @property
+    def needs_input(self) -> bool: ...
+    @property
+    def unused_data(self) -> bytes: ...
+
+@final
+class ZstdDict:
+    def __new__(cls, dict_content: bytes, /, *, is_raw: bool = False) -> Self: ...
+    def __len__(self, /) -> int: ...
+    @property
+    def as_digested_dict(self) -> tuple[Self, int]: ...
+    @property
+    def as_prefix(self) -> tuple[Self, int]: ...
+    @property
+    def as_undigested_dict(self) -> tuple[Self, int]: ...
+    @property
+    def dict_content(self) -> bytes: ...
+    @property
+    def dict_id(self) -> int: ...
+
+class ZstdError(Exception): ...
+
+def finalize_dict(
+    custom_dict_bytes: bytes, samples_bytes: bytes, samples_sizes: tuple[int, ...], dict_size: int, compression_level: int, /
+) -> bytes: ...
+def get_frame_info(frame_buffer: ReadableBuffer) -> tuple[int, int]: ...
+def get_frame_size(frame_buffer: ReadableBuffer) -> int: ...
+def get_param_bounds(parameter: int, is_compress: bool) -> tuple[int, int]: ...
+def set_parameter_types(c_parameter_type: type[CompressionParameter], d_parameter_type: type[DecompressionParameter]) -> None: ...
+def train_dict(samples_bytes: bytes, samples_sizes: tuple[int, ...], dict_size: int, /) -> bytes: ...
+
+zstd_version: Final[str]
+zstd_version_number: Final[int]
diff --git a/mypy/typeshed/stdlib/abc.pyi b/mypy/typeshed/stdlib/abc.pyi
index fdca48ac7aaf..c8cd549e30ec 100644
--- a/mypy/typeshed/stdlib/abc.pyi
+++ b/mypy/typeshed/stdlib/abc.pyi
@@ -28,17 +28,17 @@ class ABCMeta(type):
     def register(cls: ABCMeta, subclass: type[_T]) -> type[_T]: ...
 
 def abstractmethod(funcobj: _FuncT) -> _FuncT: ...
-@deprecated("Use 'classmethod' with 'abstractmethod' instead")
+@deprecated("Deprecated since Python 3.3. Use `@classmethod` stacked on top of `@abstractmethod` instead.")
 class abstractclassmethod(classmethod[_T, _P, _R_co]):
     __isabstractmethod__: Literal[True]
     def __init__(self, callable: Callable[Concatenate[type[_T], _P], _R_co]) -> None: ...
 
-@deprecated("Use 'staticmethod' with 'abstractmethod' instead")
+@deprecated("Deprecated since Python 3.3. Use `@staticmethod` stacked on top of `@abstractmethod` instead.")
 class abstractstaticmethod(staticmethod[_P, _R_co]):
     __isabstractmethod__: Literal[True]
     def __init__(self, callable: Callable[_P, _R_co]) -> None: ...
 
-@deprecated("Use 'property' with 'abstractmethod' instead")
+@deprecated("Deprecated since Python 3.3. Use `@property` stacked on top of `@abstractmethod` instead.")
 class abstractproperty(property):
     __isabstractmethod__: Literal[True]
 
diff --git a/mypy/typeshed/stdlib/annotationlib.pyi b/mypy/typeshed/stdlib/annotationlib.pyi
index 7590c632d785..3679dc29daaa 100644
--- a/mypy/typeshed/stdlib/annotationlib.pyi
+++ b/mypy/typeshed/stdlib/annotationlib.pyi
@@ -28,6 +28,20 @@ if sys.version_info >= (3, 14):
 
     @final
     class ForwardRef:
+        __slots__ = (
+            "__forward_is_argument__",
+            "__forward_is_class__",
+            "__forward_module__",
+            "__weakref__",
+            "__arg__",
+            "__globals__",
+            "__extra_names__",
+            "__code__",
+            "__ast_node__",
+            "__cell__",
+            "__owner__",
+            "__stringifier_dict__",
+        )
         __forward_is_argument__: bool
         __forward_is_class__: bool
         __forward_module__: str | None
@@ -64,7 +78,7 @@ if sys.version_info >= (3, 14):
             owner: object = None,
             format: Format = Format.VALUE,  # noqa: Y011
         ) -> AnnotationForm: ...
-        @deprecated("Use ForwardRef.evaluate() or typing.evaluate_forward_ref() instead.")
+        @deprecated("Use `ForwardRef.evaluate()` or `typing.evaluate_forward_ref()` instead.")
         def _evaluate(
             self,
             globalns: dict[str, Any] | None,
diff --git a/mypy/typeshed/stdlib/argparse.pyi b/mypy/typeshed/stdlib/argparse.pyi
index c22777e45436..f4b3aac09aa9 100644
--- a/mypy/typeshed/stdlib/argparse.pyi
+++ b/mypy/typeshed/stdlib/argparse.pyi
@@ -2,7 +2,7 @@ import sys
 from _typeshed import SupportsWrite, sentinel
 from collections.abc import Callable, Generator, Iterable, Sequence
 from re import Pattern
-from typing import IO, Any, ClassVar, Final, Generic, NewType, NoReturn, Protocol, TypeVar, overload
+from typing import IO, Any, ClassVar, Final, Generic, NewType, NoReturn, Protocol, TypeVar, overload, type_check_only
 from typing_extensions import Self, TypeAlias, deprecated
 
 __all__ = [
@@ -114,6 +114,7 @@ class _ActionsContainer:
     def _handle_conflict_error(self, action: Action, conflicting_actions: Iterable[tuple[str, Action]]) -> NoReturn: ...
     def _handle_conflict_resolve(self, action: Action, conflicting_actions: Iterable[tuple[str, Action]]) -> None: ...
 
+@type_check_only
 class _FormatterClass(Protocol):
     def __call__(self, *, prog: str) -> HelpFormatter: ...
 
@@ -155,7 +156,7 @@ class ArgumentParser(_AttributeHolder, _ActionsContainer):
             exit_on_error: bool = True,
             *,
             suggest_on_error: bool = False,
-            color: bool = False,
+            color: bool = True,
         ) -> None: ...
     else:
         def __init__(
@@ -283,7 +284,7 @@ class HelpFormatter:
 
     if sys.version_info >= (3, 14):
         def __init__(
-            self, prog: str, indent_increment: int = 2, max_help_position: int = 24, width: int | None = None, color: bool = False
+            self, prog: str, indent_increment: int = 2, max_help_position: int = 24, width: int | None = None, color: bool = True
         ) -> None: ...
     else:
         def __init__(
@@ -469,7 +470,7 @@ class Namespace(_AttributeHolder):
     __hash__: ClassVar[None]  # type: ignore[assignment]
 
 if sys.version_info >= (3, 14):
-    @deprecated("Deprecated in Python 3.14; Simply open files after parsing arguments")
+    @deprecated("Deprecated since Python 3.14. Open files after parsing arguments instead.")
     class FileType:
         # undocumented
         _mode: str
@@ -497,16 +498,40 @@ else:
 class _ArgumentGroup(_ActionsContainer):
     title: str | None
     _group_actions: list[Action]
-    def __init__(
-        self,
-        container: _ActionsContainer,
-        title: str | None = None,
-        description: str | None = None,
-        *,
-        prefix_chars: str = ...,
-        argument_default: Any = ...,
-        conflict_handler: str = ...,
-    ) -> None: ...
+    if sys.version_info >= (3, 14):
+        @overload
+        def __init__(
+            self,
+            container: _ActionsContainer,
+            title: str | None = None,
+            description: str | None = None,
+            *,
+            argument_default: Any = ...,
+            conflict_handler: str = ...,
+        ) -> None: ...
+        @overload
+        @deprecated("Undocumented `prefix_chars` parameter is deprecated since Python 3.14.")
+        def __init__(
+            self,
+            container: _ActionsContainer,
+            title: str | None = None,
+            description: str | None = None,
+            *,
+            prefix_chars: str,
+            argument_default: Any = ...,
+            conflict_handler: str = ...,
+        ) -> None: ...
+    else:
+        def __init__(
+            self,
+            container: _ActionsContainer,
+            title: str | None = None,
+            description: str | None = None,
+            *,
+            prefix_chars: str = ...,
+            argument_default: Any = ...,
+            conflict_handler: str = ...,
+        ) -> None: ...
 
 # undocumented
 class _MutuallyExclusiveGroup(_ArgumentGroup):
@@ -740,9 +765,9 @@ class _SubParsersAction(Action, Generic[_ArgumentParserT]):
             fromfile_prefix_chars: str | None = ...,
             argument_default: Any = ...,
             conflict_handler: str = ...,
-            add_help: bool = ...,
-            allow_abbrev: bool = ...,
-            exit_on_error: bool = ...,
+            add_help: bool = True,
+            allow_abbrev: bool = True,
+            exit_on_error: bool = True,
             suggest_on_error: bool = False,
             color: bool = False,
             **kwargs: Any,  # Accepting any additional kwargs for custom parser classes
@@ -766,9 +791,9 @@ class _SubParsersAction(Action, Generic[_ArgumentParserT]):
             fromfile_prefix_chars: str | None = ...,
             argument_default: Any = ...,
             conflict_handler: str = ...,
-            add_help: bool = ...,
-            allow_abbrev: bool = ...,
-            exit_on_error: bool = ...,
+            add_help: bool = True,
+            allow_abbrev: bool = True,
+            exit_on_error: bool = True,
             **kwargs: Any,  # Accepting any additional kwargs for custom parser classes
         ) -> _ArgumentParserT: ...
     else:
@@ -789,9 +814,9 @@ class _SubParsersAction(Action, Generic[_ArgumentParserT]):
             fromfile_prefix_chars: str | None = ...,
             argument_default: Any = ...,
             conflict_handler: str = ...,
-            add_help: bool = ...,
-            allow_abbrev: bool = ...,
-            exit_on_error: bool = ...,
+            add_help: bool = True,
+            allow_abbrev: bool = True,
+            exit_on_error: bool = True,
             **kwargs: Any,  # Accepting any additional kwargs for custom parser classes
         ) -> _ArgumentParserT: ...
 
diff --git a/mypy/typeshed/stdlib/array.pyi b/mypy/typeshed/stdlib/array.pyi
index bd96c9bc2d31..a6b0344a1e2e 100644
--- a/mypy/typeshed/stdlib/array.pyi
+++ b/mypy/typeshed/stdlib/array.pyi
@@ -3,17 +3,21 @@ from _typeshed import ReadableBuffer, SupportsRead, SupportsWrite
 from collections.abc import Iterable, MutableSequence
 from types import GenericAlias
 from typing import Any, ClassVar, Literal, SupportsIndex, TypeVar, overload
-from typing_extensions import Self, TypeAlias
+from typing_extensions import Self, TypeAlias, deprecated, disjoint_base
 
 _IntTypeCode: TypeAlias = Literal["b", "B", "h", "H", "i", "I", "l", "L", "q", "Q"]
 _FloatTypeCode: TypeAlias = Literal["f", "d"]
-_UnicodeTypeCode: TypeAlias = Literal["u"]
+if sys.version_info >= (3, 13):
+    _UnicodeTypeCode: TypeAlias = Literal["u", "w"]
+else:
+    _UnicodeTypeCode: TypeAlias = Literal["u"]
 _TypeCode: TypeAlias = _IntTypeCode | _FloatTypeCode | _UnicodeTypeCode
 
 _T = TypeVar("_T", int, float, str)
 
 typecodes: str
 
+@disjoint_base
 class array(MutableSequence[_T]):
     @property
     def typecode(self) -> _TypeCode: ...
@@ -27,10 +31,23 @@ class array(MutableSequence[_T]):
     def __new__(
         cls: type[array[float]], typecode: _FloatTypeCode, initializer: bytes | bytearray | Iterable[float] = ..., /
     ) -> array[float]: ...
-    @overload
-    def __new__(
-        cls: type[array[str]], typecode: _UnicodeTypeCode, initializer: bytes | bytearray | Iterable[str] = ..., /
-    ) -> array[str]: ...
+    if sys.version_info >= (3, 13):
+        @overload
+        def __new__(
+            cls: type[array[str]], typecode: Literal["w"], initializer: bytes | bytearray | Iterable[str] = ..., /
+        ) -> array[str]: ...
+        @overload
+        @deprecated("Deprecated since Python 3.3; will be removed in Python 3.16. Use 'w' typecode instead.")
+        def __new__(
+            cls: type[array[str]], typecode: Literal["u"], initializer: bytes | bytearray | Iterable[str] = ..., /
+        ) -> array[str]: ...
+    else:
+        @overload
+        @deprecated("Deprecated since Python 3.3; will be removed in Python 3.16.")
+        def __new__(
+            cls: type[array[str]], typecode: Literal["u"], initializer: bytes | bytearray | Iterable[str] = ..., /
+        ) -> array[str]: ...
+
     @overload
     def __new__(cls, typecode: str, initializer: Iterable[_T], /) -> Self: ...
     @overload
@@ -58,6 +75,7 @@ class array(MutableSequence[_T]):
     def tounicode(self) -> str: ...
 
     __hash__: ClassVar[None]  # type: ignore[assignment]
+    def __contains__(self, value: object, /) -> bool: ...
     def __len__(self) -> int: ...
     @overload
     def __getitem__(self, key: SupportsIndex, /) -> _T: ...
diff --git a/mypy/typeshed/stdlib/ast.pyi b/mypy/typeshed/stdlib/ast.pyi
index af9d20d086b3..d360c2ed60e5 100644
--- a/mypy/typeshed/stdlib/ast.pyi
+++ b/mypy/typeshed/stdlib/ast.pyi
@@ -1,3 +1,4 @@
+import ast
 import builtins
 import os
 import sys
@@ -9,8 +10,8 @@ from _ast import (
 )
 from _typeshed import ReadableBuffer, Unused
 from collections.abc import Iterable, Iterator, Sequence
-from typing import Any, ClassVar, Generic, Literal, TypedDict, TypeVar as _TypeVar, overload
-from typing_extensions import Self, Unpack, deprecated
+from typing import Any, ClassVar, Generic, Literal, TypedDict, TypeVar as _TypeVar, overload, type_check_only
+from typing_extensions import Self, Unpack, deprecated, disjoint_base
 
 if sys.version_info >= (3, 13):
     from _ast import PyCF_OPTIMIZED_AST as PyCF_OPTIMIZED_AST
@@ -19,6 +20,7 @@ if sys.version_info >= (3, 13):
 _EndPositionT = typing_extensions.TypeVar("_EndPositionT", int, int | None, default=int | None)
 
 # Corresponds to the names in the `_attributes` class variable which is non-empty in certain AST nodes
+@type_check_only
 class _Attributes(TypedDict, Generic[_EndPositionT], total=False):
     lineno: int
     col_offset: int
@@ -28,16 +30,24 @@ class _Attributes(TypedDict, Generic[_EndPositionT], total=False):
 # The various AST classes are implemented in C, and imported from _ast at runtime,
 # but they consider themselves to live in the ast module,
 # so we'll define the stubs in this file.
-class AST:
-    if sys.version_info >= (3, 10):
+if sys.version_info >= (3, 12):
+    @disjoint_base
+    class AST:
         __match_args__ = ()
-    _attributes: ClassVar[tuple[str, ...]]
-    _fields: ClassVar[tuple[str, ...]]
-    if sys.version_info >= (3, 13):
-        _field_types: ClassVar[dict[str, Any]]
+        _attributes: ClassVar[tuple[str, ...]]
+        _fields: ClassVar[tuple[str, ...]]
+        if sys.version_info >= (3, 13):
+            _field_types: ClassVar[dict[str, Any]]
 
-    if sys.version_info >= (3, 14):
-        def __replace__(self) -> Self: ...
+        if sys.version_info >= (3, 14):
+            def __replace__(self) -> Self: ...
+
+else:
+    class AST:
+        if sys.version_info >= (3, 10):
+            __match_args__ = ()
+        _attributes: ClassVar[tuple[str, ...]]
+        _fields: ClassVar[tuple[str, ...]]
 
 class mod(AST): ...
 
@@ -623,21 +633,6 @@ class AsyncWith(stmt):
             **kwargs: Unpack[_Attributes],
         ) -> Self: ...
 
-if sys.version_info >= (3, 10):
-    class Match(stmt):
-        __match_args__ = ("subject", "cases")
-        subject: expr
-        cases: list[match_case]
-        if sys.version_info >= (3, 13):
-            def __init__(self, subject: expr, cases: list[match_case] = ..., **kwargs: Unpack[_Attributes]) -> None: ...
-        else:
-            def __init__(self, subject: expr, cases: list[match_case], **kwargs: Unpack[_Attributes]) -> None: ...
-
-        if sys.version_info >= (3, 14):
-            def __replace__(
-                self, *, subject: expr = ..., cases: list[match_case] = ..., **kwargs: Unpack[_Attributes]
-            ) -> Self: ...
-
 class Raise(stmt):
     if sys.version_info >= (3, 10):
         __match_args__ = ("exc", "cause")
@@ -1076,13 +1071,13 @@ if sys.version_info >= (3, 14):
         value: expr
         str: builtins.str
         conversion: int
-        format_spec: builtins.str | None = None
+        format_spec: expr | None = None
         def __init__(
             self,
             value: expr = ...,
             str: builtins.str = ...,
             conversion: int = ...,
-            format_spec: builtins.str | None = ...,
+            format_spec: expr | None = ...,
             **kwargs: Unpack[_Attributes],
         ) -> None: ...
         def __replace__(
@@ -1091,7 +1086,7 @@ if sys.version_info >= (3, 14):
             value: expr = ...,
             str: builtins.str = ...,
             conversion: int = ...,
-            format_spec: builtins.str | None = ...,
+            format_spec: expr | None = ...,
             **kwargs: Unpack[_Attributes],
         ) -> Self: ...
 
@@ -1110,8 +1105,18 @@ class Constant(expr):
     kind: str | None
     if sys.version_info < (3, 14):
         # Aliases for value, for backwards compatibility
-        s: _ConstantValue
-        n: _ConstantValue
+        @property
+        @deprecated("Removed in Python 3.14. Use `value` instead.")
+        def n(self) -> _ConstantValue: ...
+        @n.setter
+        @deprecated("Removed in Python 3.14. Use `value` instead.")
+        def n(self, value: _ConstantValue) -> None: ...
+        @property
+        @deprecated("Removed in Python 3.14. Use `value` instead.")
+        def s(self) -> _ConstantValue: ...
+        @s.setter
+        @deprecated("Removed in Python 3.14. Use `value` instead.")
+        def s(self, value: _ConstantValue) -> None: ...
 
     def __init__(self, value: _ConstantValue, kind: str | None = None, **kwargs: Unpack[_Attributes]) -> None: ...
 
@@ -1135,13 +1140,13 @@ class Subscript(expr):
     if sys.version_info >= (3, 10):
         __match_args__ = ("value", "slice", "ctx")
     value: expr
-    slice: _Slice
+    slice: expr
     ctx: expr_context  # Not present in Python < 3.13 if not passed to `__init__`
-    def __init__(self, value: expr, slice: _Slice, ctx: expr_context = ..., **kwargs: Unpack[_Attributes]) -> None: ...
+    def __init__(self, value: expr, slice: expr, ctx: expr_context = ..., **kwargs: Unpack[_Attributes]) -> None: ...
 
     if sys.version_info >= (3, 14):
         def __replace__(
-            self, *, value: expr = ..., slice: _Slice = ..., ctx: expr_context = ..., **kwargs: Unpack[_Attributes]
+            self, *, value: expr = ..., slice: expr = ..., ctx: expr_context = ..., **kwargs: Unpack[_Attributes]
         ) -> Self: ...
 
 class Starred(expr):
@@ -1194,36 +1199,28 @@ class Tuple(expr):
 @deprecated("Deprecated since Python 3.9.")
 class slice(AST): ...
 
-_Slice: typing_extensions.TypeAlias = expr
-_SliceAttributes: typing_extensions.TypeAlias = _Attributes
-
-class Slice(_Slice):
+class Slice(expr):
     if sys.version_info >= (3, 10):
         __match_args__ = ("lower", "upper", "step")
     lower: expr | None
     upper: expr | None
     step: expr | None
     def __init__(
-        self, lower: expr | None = None, upper: expr | None = None, step: expr | None = None, **kwargs: Unpack[_SliceAttributes]
+        self, lower: expr | None = None, upper: expr | None = None, step: expr | None = None, **kwargs: Unpack[_Attributes]
     ) -> None: ...
 
     if sys.version_info >= (3, 14):
         def __replace__(
-            self,
-            *,
-            lower: expr | None = ...,
-            upper: expr | None = ...,
-            step: expr | None = ...,
-            **kwargs: Unpack[_SliceAttributes],
+            self, *, lower: expr | None = ..., upper: expr | None = ..., step: expr | None = ..., **kwargs: Unpack[_Attributes]
         ) -> Self: ...
 
-@deprecated("Deprecated since Python 3.9. Use ast.Tuple instead.")
+@deprecated("Deprecated since Python 3.9. Use `ast.Tuple` instead.")
 class ExtSlice(slice):
-    def __new__(cls, dims: Iterable[slice] = (), **kwargs: Unpack[_SliceAttributes]) -> Tuple: ...  # type: ignore[misc]
+    def __new__(cls, dims: Iterable[slice] = (), **kwargs: Unpack[_Attributes]) -> Tuple: ...  # type: ignore[misc]
 
 @deprecated("Deprecated since Python 3.9. Use the index value directly instead.")
 class Index(slice):
-    def __new__(cls, value: expr, **kwargs: Unpack[_SliceAttributes]) -> expr: ...  # type: ignore[misc]
+    def __new__(cls, value: expr, **kwargs: Unpack[_Attributes]) -> expr: ...  # type: ignore[misc]
 
 class expr_context(AST): ...
 
@@ -1465,37 +1462,48 @@ class withitem(AST):
         def __replace__(self, *, context_expr: expr = ..., optional_vars: expr | None = ...) -> Self: ...
 
 if sys.version_info >= (3, 10):
+    class pattern(AST):
+        lineno: int
+        col_offset: int
+        end_lineno: int
+        end_col_offset: int
+        def __init__(self, **kwargs: Unpack[_Attributes[int]]) -> None: ...
+
+        if sys.version_info >= (3, 14):
+            def __replace__(
+                self, *, lineno: int = ..., col_offset: int = ..., end_lineno: int = ..., end_col_offset: int = ...
+            ) -> Self: ...
+
     class match_case(AST):
         __match_args__ = ("pattern", "guard", "body")
-        pattern: _Pattern
+        pattern: ast.pattern
         guard: expr | None
         body: list[stmt]
         if sys.version_info >= (3, 13):
-            def __init__(self, pattern: _Pattern, guard: expr | None = None, body: list[stmt] = ...) -> None: ...
-        else:
+            def __init__(self, pattern: ast.pattern, guard: expr | None = None, body: list[stmt] = ...) -> None: ...
+        elif sys.version_info >= (3, 10):
             @overload
-            def __init__(self, pattern: _Pattern, guard: expr | None, body: list[stmt]) -> None: ...
+            def __init__(self, pattern: ast.pattern, guard: expr | None, body: list[stmt]) -> None: ...
             @overload
-            def __init__(self, pattern: _Pattern, guard: expr | None = None, *, body: list[stmt]) -> None: ...
+            def __init__(self, pattern: ast.pattern, guard: expr | None = None, *, body: list[stmt]) -> None: ...
 
         if sys.version_info >= (3, 14):
-            def __replace__(self, *, pattern: _Pattern = ..., guard: expr | None = ..., body: list[stmt] = ...) -> Self: ...
+            def __replace__(self, *, pattern: ast.pattern = ..., guard: expr | None = ..., body: list[stmt] = ...) -> Self: ...
 
-    class pattern(AST):
-        lineno: int
-        col_offset: int
-        end_lineno: int
-        end_col_offset: int
-        def __init__(self, **kwargs: Unpack[_Attributes[int]]) -> None: ...
+    class Match(stmt):
+        __match_args__ = ("subject", "cases")
+        subject: expr
+        cases: list[match_case]
+        if sys.version_info >= (3, 13):
+            def __init__(self, subject: expr, cases: list[match_case] = ..., **kwargs: Unpack[_Attributes]) -> None: ...
+        else:
+            def __init__(self, subject: expr, cases: list[match_case], **kwargs: Unpack[_Attributes]) -> None: ...
 
         if sys.version_info >= (3, 14):
             def __replace__(
-                self, *, lineno: int = ..., col_offset: int = ..., end_lineno: int = ..., end_col_offset: int = ...
+                self, *, subject: expr = ..., cases: list[match_case] = ..., **kwargs: Unpack[_Attributes]
             ) -> Self: ...
 
-    # Without the alias, Pyright complains variables named pattern are recursively defined
-    _Pattern: typing_extensions.TypeAlias = pattern
-
     class MatchValue(pattern):
         __match_args__ = ("value",)
         value: expr
@@ -1506,11 +1514,11 @@ if sys.version_info >= (3, 10):
 
     class MatchSingleton(pattern):
         __match_args__ = ("value",)
-        value: Literal[True, False] | None
-        def __init__(self, value: Literal[True, False] | None, **kwargs: Unpack[_Attributes[int]]) -> None: ...
+        value: bool | None
+        def __init__(self, value: bool | None, **kwargs: Unpack[_Attributes[int]]) -> None: ...
 
         if sys.version_info >= (3, 14):
-            def __replace__(self, *, value: Literal[True, False] | None = ..., **kwargs: Unpack[_Attributes[int]]) -> Self: ...
+            def __replace__(self, *, value: bool | None = ..., **kwargs: Unpack[_Attributes[int]]) -> Self: ...
 
     class MatchSequence(pattern):
         __match_args__ = ("patterns",)
@@ -1590,22 +1598,22 @@ if sys.version_info >= (3, 10):
     class MatchStar(pattern):
         __match_args__ = ("name",)
         name: str | None
-        def __init__(self, name: str | None, **kwargs: Unpack[_Attributes[int]]) -> None: ...
+        def __init__(self, name: str | None = None, **kwargs: Unpack[_Attributes[int]]) -> None: ...
 
         if sys.version_info >= (3, 14):
             def __replace__(self, *, name: str | None = ..., **kwargs: Unpack[_Attributes[int]]) -> Self: ...
 
     class MatchAs(pattern):
         __match_args__ = ("pattern", "name")
-        pattern: _Pattern | None
+        pattern: ast.pattern | None
         name: str | None
         def __init__(
-            self, pattern: _Pattern | None = None, name: str | None = None, **kwargs: Unpack[_Attributes[int]]
+            self, pattern: ast.pattern | None = None, name: str | None = None, **kwargs: Unpack[_Attributes[int]]
         ) -> None: ...
 
         if sys.version_info >= (3, 14):
             def __replace__(
-                self, *, pattern: _Pattern | None = ..., name: str | None = ..., **kwargs: Unpack[_Attributes[int]]
+                self, *, pattern: ast.pattern | None = ..., name: str | None = ..., **kwargs: Unpack[_Attributes[int]]
             ) -> Self: ...
 
     class MatchOr(pattern):
@@ -1701,31 +1709,35 @@ if sys.version_info >= (3, 12):
                 self, *, name: str = ..., default_value: expr | None = ..., **kwargs: Unpack[_Attributes[int]]
             ) -> Self: ...
 
-class _ABC(type):
-    def __init__(cls, *args: Unused) -> None: ...
+if sys.version_info >= (3, 14):
+    @type_check_only
+    class _ABC(type):
+        def __init__(cls, *args: Unused) -> None: ...
+
+else:
+    class _ABC(type):
+        def __init__(cls, *args: Unused) -> None: ...
 
 if sys.version_info < (3, 14):
-    @deprecated("Replaced by ast.Constant; removed in Python 3.14")
+    @deprecated("Removed in Python 3.14. Use `ast.Constant` instead.")
     class Num(Constant, metaclass=_ABC):
-        value: int | float | complex
+        def __new__(cls, n: complex, **kwargs: Unpack[_Attributes]) -> Constant: ...  # type: ignore[misc]  # pyright: ignore[reportInconsistentConstructor]
 
-    @deprecated("Replaced by ast.Constant; removed in Python 3.14")
+    @deprecated("Removed in Python 3.14. Use `ast.Constant` instead.")
     class Str(Constant, metaclass=_ABC):
-        value: str
-        # Aliases for value, for backwards compatibility
-        s: str
+        def __new__(cls, s: str, **kwargs: Unpack[_Attributes]) -> Constant: ...  # type: ignore[misc]  # pyright: ignore[reportInconsistentConstructor]
 
-    @deprecated("Replaced by ast.Constant; removed in Python 3.14")
+    @deprecated("Removed in Python 3.14. Use `ast.Constant` instead.")
     class Bytes(Constant, metaclass=_ABC):
-        value: bytes
-        # Aliases for value, for backwards compatibility
-        s: bytes
+        def __new__(cls, s: bytes, **kwargs: Unpack[_Attributes]) -> Constant: ...  # type: ignore[misc]  # pyright: ignore[reportInconsistentConstructor]
 
-    @deprecated("Replaced by ast.Constant; removed in Python 3.14")
-    class NameConstant(Constant, metaclass=_ABC): ...
+    @deprecated("Removed in Python 3.14. Use `ast.Constant` instead.")
+    class NameConstant(Constant, metaclass=_ABC):
+        def __new__(cls, value: _ConstantValue, kind: str | None, **kwargs: Unpack[_Attributes]) -> Constant: ...  # type: ignore[misc]  # pyright: ignore[reportInconsistentConstructor]
 
-    @deprecated("Replaced by ast.Constant; removed in Python 3.14")
-    class Ellipsis(Constant, metaclass=_ABC): ...
+    @deprecated("Removed in Python 3.14. Use `ast.Constant` instead.")
+    class Ellipsis(Constant, metaclass=_ABC):
+        def __new__(cls, **kwargs: Unpack[_Attributes]) -> Constant: ...  # type: ignore[misc]  # pyright: ignore[reportInconsistentConstructor]
 
 # everything below here is defined in ast.py
 
@@ -1808,7 +1820,7 @@ if sys.version_info >= (3, 13):
         type_comments: bool = False,
         feature_version: None | int | tuple[int, int] = None,
         optimize: Literal[-1, 0, 1, 2] = -1,
-    ) -> AST: ...
+    ) -> mod: ...
 
 else:
     @overload
@@ -1879,7 +1891,7 @@ else:
         *,
         type_comments: bool = False,
         feature_version: None | int | tuple[int, int] = None,
-    ) -> AST: ...
+    ) -> mod: ...
 
 def literal_eval(node_or_string: str | AST) -> Any: ...
 
@@ -2042,15 +2054,15 @@ class NodeVisitor:
     def visit_Param(self, node: Param) -> Any: ...
 
     if sys.version_info < (3, 14):
-        @deprecated("Replaced by visit_Constant; removed in Python 3.14")
+        @deprecated("Removed in Python 3.14. Use `visit_Constant` instead.")
         def visit_Num(self, node: Num) -> Any: ...  # type: ignore[deprecated]
-        @deprecated("Replaced by visit_Constant; removed in Python 3.14")
+        @deprecated("Removed in Python 3.14. Use `visit_Constant` instead.")
         def visit_Str(self, node: Str) -> Any: ...  # type: ignore[deprecated]
-        @deprecated("Replaced by visit_Constant; removed in Python 3.14")
+        @deprecated("Removed in Python 3.14. Use `visit_Constant` instead.")
         def visit_Bytes(self, node: Bytes) -> Any: ...  # type: ignore[deprecated]
-        @deprecated("Replaced by visit_Constant; removed in Python 3.14")
+        @deprecated("Removed in Python 3.14. Use `visit_Constant` instead.")
         def visit_NameConstant(self, node: NameConstant) -> Any: ...  # type: ignore[deprecated]
-        @deprecated("Replaced by visit_Constant; removed in Python 3.14")
+        @deprecated("Removed in Python 3.14. Use `visit_Constant` instead.")
         def visit_Ellipsis(self, node: Ellipsis) -> Any: ...  # type: ignore[deprecated]
 
 class NodeTransformer(NodeVisitor):
diff --git a/mypy/typeshed/stdlib/asyncio/__init__.pyi b/mypy/typeshed/stdlib/asyncio/__init__.pyi
index 68e44a88face..23cf57aaac33 100644
--- a/mypy/typeshed/stdlib/asyncio/__init__.pyi
+++ b/mypy/typeshed/stdlib/asyncio/__init__.pyi
@@ -1,4 +1,4 @@
-# ruff: noqa: PLR5501 # This condition is so big, it's clearer to keep to platform condition in two blocks
+# This condition is so big, it's clearer to keep to platform condition in two blocks
 # Can't NOQA on a specific line: https://github.com/plinss/flake8-noqa/issues/22
 import sys
 from collections.abc import Awaitable, Coroutine, Generator
@@ -41,14 +41,11 @@ if sys.platform == "win32":
             "Server",  # from base_events
             "iscoroutinefunction",  # from coroutines
             "iscoroutine",  # from coroutines
-            "_AbstractEventLoopPolicy",  # from events
             "AbstractEventLoop",  # from events
             "AbstractServer",  # from events
             "Handle",  # from events
             "TimerHandle",  # from events
-            "_get_event_loop_policy",  # from events
             "get_event_loop_policy",  # from events
-            "_set_event_loop_policy",  # from events
             "set_event_loop_policy",  # from events
             "get_event_loop",  # from events
             "set_event_loop",  # from events
@@ -517,14 +514,11 @@ else:
             "Server",  # from base_events
             "iscoroutinefunction",  # from coroutines
             "iscoroutine",  # from coroutines
-            "_AbstractEventLoopPolicy",  # from events
             "AbstractEventLoop",  # from events
             "AbstractServer",  # from events
             "Handle",  # from events
             "TimerHandle",  # from events
-            "_get_event_loop_policy",  # from events
             "get_event_loop_policy",  # from events
-            "_set_event_loop_policy",  # from events
             "set_event_loop_policy",  # from events
             "get_event_loop",  # from events
             "set_event_loop",  # from events
@@ -610,7 +604,6 @@ else:
             "DatagramTransport",  # from transports
             "SubprocessTransport",  # from transports
             "SelectorEventLoop",  # from unix_events
-            "_DefaultEventLoopPolicy",  # from unix_events
             "EventLoop",  # from unix_events
         )
     elif sys.version_info >= (3, 13):
diff --git a/mypy/typeshed/stdlib/asyncio/base_events.pyi b/mypy/typeshed/stdlib/asyncio/base_events.pyi
index cad7dde40b01..1f493210d665 100644
--- a/mypy/typeshed/stdlib/asyncio/base_events.pyi
+++ b/mypy/typeshed/stdlib/asyncio/base_events.pyi
@@ -10,7 +10,7 @@ from asyncio.transports import BaseTransport, DatagramTransport, ReadTransport,
 from collections.abc import Callable, Iterable, Sequence
 from concurrent.futures import Executor, ThreadPoolExecutor
 from contextvars import Context
-from socket import AddressFamily, SocketKind, _Address, _RetAddress, socket
+from socket import AddressFamily, AddressInfo, SocketKind, _Address, _RetAddress, socket
 from typing import IO, Any, Literal, TypeVar, overload
 from typing_extensions import TypeAlias, TypeVarTuple, Unpack
 
@@ -235,8 +235,8 @@ class BaseEventLoop(AbstractEventLoop):
             host: str | Sequence[str] | None = None,
             port: int = ...,
             *,
-            family: int = ...,
-            flags: int = ...,
+            family: int = 0,
+            flags: int = 1,
             sock: None = None,
             backlog: int = 100,
             ssl: _SSLContext = None,
@@ -254,8 +254,8 @@ class BaseEventLoop(AbstractEventLoop):
             host: None = None,
             port: None = None,
             *,
-            family: int = ...,
-            flags: int = ...,
+            family: int = 0,
+            flags: int = 1,
             sock: socket = ...,
             backlog: int = 100,
             ssl: _SSLContext = None,
@@ -274,8 +274,8 @@ class BaseEventLoop(AbstractEventLoop):
             host: str | Sequence[str] | None = None,
             port: int = ...,
             *,
-            family: int = ...,
-            flags: int = ...,
+            family: int = AddressFamily.AF_UNSPEC,
+            flags: int = AddressInfo.AI_PASSIVE,
             sock: None = None,
             backlog: int = 100,
             ssl: _SSLContext = None,
@@ -292,8 +292,8 @@ class BaseEventLoop(AbstractEventLoop):
             host: None = None,
             port: None = None,
             *,
-            family: int = ...,
-            flags: int = ...,
+            family: int = AddressFamily.AF_UNSPEC,
+            flags: int = AddressInfo.AI_PASSIVE,
             sock: socket = ...,
             backlog: int = 100,
             ssl: _SSLContext = None,
@@ -311,8 +311,8 @@ class BaseEventLoop(AbstractEventLoop):
             host: str | Sequence[str] | None = None,
             port: int = ...,
             *,
-            family: int = ...,
-            flags: int = ...,
+            family: int = AddressFamily.AF_UNSPEC,
+            flags: int = AddressInfo.AI_PASSIVE,
             sock: None = None,
             backlog: int = 100,
             ssl: _SSLContext = None,
@@ -328,8 +328,8 @@ class BaseEventLoop(AbstractEventLoop):
             host: None = None,
             port: None = None,
             *,
-            family: int = ...,
-            flags: int = ...,
+            family: int = AddressFamily.AF_UNSPEC,
+            flags: int = AddressInfo.AI_PASSIVE,
             sock: socket = ...,
             backlog: int = 100,
             ssl: _SSLContext = None,
diff --git a/mypy/typeshed/stdlib/asyncio/base_futures.pyi b/mypy/typeshed/stdlib/asyncio/base_futures.pyi
index 55d2fbdbdb62..2cd0f2e3a7e4 100644
--- a/mypy/typeshed/stdlib/asyncio/base_futures.pyi
+++ b/mypy/typeshed/stdlib/asyncio/base_futures.pyi
@@ -1,19 +1,17 @@
+from _asyncio import Future
 from collections.abc import Callable, Sequence
 from contextvars import Context
 from typing import Any, Final
+from typing_extensions import TypeIs
 
 from . import futures
 
 __all__ = ()
 
-# asyncio defines 'isfuture()' in base_futures.py and re-imports it in futures.py
-# but it leads to circular import error in pytype tool.
-# That's why the import order is reversed.
-from .futures import isfuture as isfuture
-
 _PENDING: Final = "PENDING"  # undocumented
 _CANCELLED: Final = "CANCELLED"  # undocumented
 _FINISHED: Final = "FINISHED"  # undocumented
 
+def isfuture(obj: object) -> TypeIs[Future[Any]]: ...
 def _format_callbacks(cb: Sequence[tuple[Callable[[futures.Future[Any]], None], Context]]) -> str: ...  # undocumented
 def _future_repr_info(future: futures.Future[Any]) -> list[str]: ...  # undocumented
diff --git a/mypy/typeshed/stdlib/asyncio/coroutines.pyi b/mypy/typeshed/stdlib/asyncio/coroutines.pyi
index 8ef30b3d3198..59212f4ec398 100644
--- a/mypy/typeshed/stdlib/asyncio/coroutines.pyi
+++ b/mypy/typeshed/stdlib/asyncio/coroutines.pyi
@@ -1,7 +1,7 @@
 import sys
 from collections.abc import Awaitable, Callable, Coroutine
 from typing import Any, TypeVar, overload
-from typing_extensions import ParamSpec, TypeGuard, TypeIs
+from typing_extensions import ParamSpec, TypeGuard, TypeIs, deprecated
 
 # Keep asyncio.__all__ updated with any changes to __all__ here
 if sys.version_info >= (3, 11):
@@ -14,6 +14,7 @@ _FunctionT = TypeVar("_FunctionT", bound=Callable[..., Any])
 _P = ParamSpec("_P")
 
 if sys.version_info < (3, 11):
+    @deprecated("Deprecated since Python 3.8; removed in Python 3.11. Use `async def` instead.")
     def coroutine(func: _FunctionT) -> _FunctionT: ...
 
 @overload
diff --git a/mypy/typeshed/stdlib/asyncio/events.pyi b/mypy/typeshed/stdlib/asyncio/events.pyi
index 688ef3ed0879..14c4c0bf3d5a 100644
--- a/mypy/typeshed/stdlib/asyncio/events.pyi
+++ b/mypy/typeshed/stdlib/asyncio/events.pyi
@@ -11,8 +11,8 @@ from abc import ABCMeta, abstractmethod
 from collections.abc import Callable, Sequence
 from concurrent.futures import Executor
 from contextvars import Context
-from socket import AddressFamily, SocketKind, _Address, _RetAddress, socket
-from typing import IO, Any, Literal, Protocol, TypeVar, overload
+from socket import AddressFamily, AddressInfo, SocketKind, _Address, _RetAddress, socket
+from typing import IO, Any, Literal, Protocol, TypeVar, overload, type_check_only
 from typing_extensions import Self, TypeAlias, TypeVarTuple, Unpack, deprecated
 
 from . import _AwaitableLike, _CoroutineLike
@@ -28,14 +28,11 @@ if sys.version_info < (3, 14):
 # Keep asyncio.__all__ updated with any changes to __all__ here
 if sys.version_info >= (3, 14):
     __all__ = (
-        "_AbstractEventLoopPolicy",
         "AbstractEventLoop",
         "AbstractServer",
         "Handle",
         "TimerHandle",
-        "_get_event_loop_policy",
         "get_event_loop_policy",
-        "_set_event_loop_policy",
         "set_event_loop_policy",
         "get_event_loop",
         "set_event_loop",
@@ -71,10 +68,12 @@ _ExceptionHandler: TypeAlias = Callable[[AbstractEventLoop, _Context], object]
 _ProtocolFactory: TypeAlias = Callable[[], BaseProtocol]
 _SSLContext: TypeAlias = bool | None | ssl.SSLContext
 
+@type_check_only
 class _TaskFactory(Protocol):
     def __call__(self, loop: AbstractEventLoop, factory: _CoroutineLike[_T], /) -> Future[_T]: ...
 
 class Handle:
+    __slots__ = ("_callback", "_args", "_cancelled", "_loop", "_source_traceback", "_repr", "__weakref__", "_context")
     _cancelled: bool
     _args: Sequence[Any]
     def __init__(
@@ -87,6 +86,7 @@ class Handle:
         def get_context(self) -> Context: ...
 
 class TimerHandle(Handle):
+    __slots__ = ["_scheduled", "_when"]
     def __init__(
         self,
         when: float,
@@ -289,8 +289,8 @@ class AbstractEventLoop:
             host: str | Sequence[str] | None = None,
             port: int = ...,
             *,
-            family: int = ...,
-            flags: int = ...,
+            family: int = AddressFamily.AF_UNSPEC,
+            flags: int = AddressInfo.AI_PASSIVE,
             sock: None = None,
             backlog: int = 100,
             ssl: _SSLContext = None,
@@ -309,8 +309,8 @@ class AbstractEventLoop:
             host: None = None,
             port: None = None,
             *,
-            family: int = ...,
-            flags: int = ...,
+            family: int = AddressFamily.AF_UNSPEC,
+            flags: int = AddressInfo.AI_PASSIVE,
             sock: socket = ...,
             backlog: int = 100,
             ssl: _SSLContext = None,
@@ -330,8 +330,8 @@ class AbstractEventLoop:
             host: str | Sequence[str] | None = None,
             port: int = ...,
             *,
-            family: int = ...,
-            flags: int = ...,
+            family: int = AddressFamily.AF_UNSPEC,
+            flags: int = AddressInfo.AI_PASSIVE,
             sock: None = None,
             backlog: int = 100,
             ssl: _SSLContext = None,
@@ -349,8 +349,8 @@ class AbstractEventLoop:
             host: None = None,
             port: None = None,
             *,
-            family: int = ...,
-            flags: int = ...,
+            family: int = AddressFamily.AF_UNSPEC,
+            flags: int = AddressInfo.AI_PASSIVE,
             sock: socket = ...,
             backlog: int = 100,
             ssl: _SSLContext = None,
@@ -369,8 +369,8 @@ class AbstractEventLoop:
             host: str | Sequence[str] | None = None,
             port: int = ...,
             *,
-            family: int = ...,
-            flags: int = ...,
+            family: int = AddressFamily.AF_UNSPEC,
+            flags: int = AddressInfo.AI_PASSIVE,
             sock: None = None,
             backlog: int = 100,
             ssl: _SSLContext = None,
@@ -387,8 +387,8 @@ class AbstractEventLoop:
             host: None = None,
             port: None = None,
             *,
-            family: int = ...,
-            flags: int = ...,
+            family: int = AddressFamily.AF_UNSPEC,
+            flags: int = AddressInfo.AI_PASSIVE,
             sock: socket = ...,
             backlog: int = 100,
             ssl: _SSLContext = None,
@@ -536,7 +536,7 @@ class AbstractEventLoop:
         bufsize: Literal[0] = 0,
         encoding: None = None,
         errors: None = None,
-        text: Literal[False] | None = ...,
+        text: Literal[False] | None = None,
         **kwargs: Any,
     ) -> tuple[SubprocessTransport, _ProtocolT]: ...
     @abstractmethod
@@ -602,6 +602,9 @@ class AbstractEventLoop:
     @abstractmethod
     async def shutdown_default_executor(self) -> None: ...
 
+# This class does not exist at runtime, but stubtest complains if it's marked as
+# @type_check_only because it has an alias that does exist at runtime. See mypy#19568.
+# @type_check_only
 class _AbstractEventLoopPolicy:
     @abstractmethod
     def get_event_loop(self) -> AbstractEventLoop: ...
@@ -613,10 +616,10 @@ class _AbstractEventLoopPolicy:
     if sys.version_info < (3, 14):
         if sys.version_info >= (3, 12):
             @abstractmethod
-            @deprecated("Deprecated as of Python 3.12; will be removed in Python 3.14")
+            @deprecated("Deprecated since Python 3.12; removed in Python 3.14.")
             def get_child_watcher(self) -> AbstractChildWatcher: ...
             @abstractmethod
-            @deprecated("Deprecated as of Python 3.12; will be removed in Python 3.14")
+            @deprecated("Deprecated since Python 3.12; removed in Python 3.14.")
             def set_child_watcher(self, watcher: AbstractChildWatcher) -> None: ...
         else:
             @abstractmethod
@@ -642,9 +645,9 @@ else:
 if sys.version_info >= (3, 14):
     def _get_event_loop_policy() -> _AbstractEventLoopPolicy: ...
     def _set_event_loop_policy(policy: _AbstractEventLoopPolicy | None) -> None: ...
-    @deprecated("Deprecated as of Python 3.14; will be removed in Python 3.16")
+    @deprecated("Deprecated since Python 3.14; will be removed in Python 3.16.")
     def get_event_loop_policy() -> _AbstractEventLoopPolicy: ...
-    @deprecated("Deprecated as of Python 3.14; will be removed in Python 3.16")
+    @deprecated("Deprecated since Python 3.14; will be removed in Python 3.16.")
     def set_event_loop_policy(policy: _AbstractEventLoopPolicy | None) -> None: ...
 
 else:
@@ -656,9 +659,9 @@ def new_event_loop() -> AbstractEventLoop: ...
 
 if sys.version_info < (3, 14):
     if sys.version_info >= (3, 12):
-        @deprecated("Deprecated as of Python 3.12; will be removed in Python 3.14")
+        @deprecated("Deprecated since Python 3.12; removed in Python 3.14.")
         def get_child_watcher() -> AbstractChildWatcher: ...
-        @deprecated("Deprecated as of Python 3.12; will be removed in Python 3.14")
+        @deprecated("Deprecated since Python 3.12; removed in Python 3.14.")
         def set_child_watcher(watcher: AbstractChildWatcher) -> None: ...
 
     else:
diff --git a/mypy/typeshed/stdlib/asyncio/format_helpers.pyi b/mypy/typeshed/stdlib/asyncio/format_helpers.pyi
index 41505b14cd08..597eb9e56e1a 100644
--- a/mypy/typeshed/stdlib/asyncio/format_helpers.pyi
+++ b/mypy/typeshed/stdlib/asyncio/format_helpers.pyi
@@ -3,9 +3,10 @@ import sys
 import traceback
 from collections.abc import Iterable
 from types import FrameType, FunctionType
-from typing import Any, overload
+from typing import Any, overload, type_check_only
 from typing_extensions import TypeAlias
 
+@type_check_only
 class _HasWrapper:
     __wrapper__: _HasWrapper | FunctionType
 
diff --git a/mypy/typeshed/stdlib/asyncio/futures.pyi b/mypy/typeshed/stdlib/asyncio/futures.pyi
index 644d2d0e94ca..c907c7036b04 100644
--- a/mypy/typeshed/stdlib/asyncio/futures.pyi
+++ b/mypy/typeshed/stdlib/asyncio/futures.pyi
@@ -1,9 +1,9 @@
 import sys
 from _asyncio import Future as Future
 from concurrent.futures._base import Future as _ConcurrentFuture
-from typing import Any, TypeVar
-from typing_extensions import TypeIs
+from typing import TypeVar
 
+from .base_futures import isfuture as isfuture
 from .events import AbstractEventLoop
 
 # Keep asyncio.__all__ updated with any changes to __all__ here
@@ -16,8 +16,4 @@ else:
 
 _T = TypeVar("_T")
 
-# asyncio defines 'isfuture()' in base_futures.py and re-imports it in futures.py
-# but it leads to circular import error in pytype tool.
-# That's why the import order is reversed.
-def isfuture(obj: object) -> TypeIs[Future[Any]]: ...
 def wrap_future(future: _ConcurrentFuture[_T] | Future[_T], *, loop: AbstractEventLoop | None = None) -> Future[_T]: ...
diff --git a/mypy/typeshed/stdlib/asyncio/graph.pyi b/mypy/typeshed/stdlib/asyncio/graph.pyi
index cb2cf0174995..18a8a6457d75 100644
--- a/mypy/typeshed/stdlib/asyncio/graph.pyi
+++ b/mypy/typeshed/stdlib/asyncio/graph.pyi
@@ -1,26 +1,28 @@
+import sys
 from _typeshed import SupportsWrite
 from asyncio import Future
 from dataclasses import dataclass
 from types import FrameType
 from typing import Any, overload
 
-__all__ = ("capture_call_graph", "format_call_graph", "print_call_graph", "FrameCallGraphEntry", "FutureCallGraph")
+if sys.version_info >= (3, 14):
+    __all__ = ("capture_call_graph", "format_call_graph", "print_call_graph", "FrameCallGraphEntry", "FutureCallGraph")
 
-@dataclass(frozen=True)
-class FrameCallGraphEntry:
-    frame: FrameType
+    @dataclass(frozen=True, slots=True)
+    class FrameCallGraphEntry:
+        frame: FrameType
 
-@dataclass(frozen=True)
-class FutureCallGraph:
-    future: Future[Any]
-    call_stack: tuple[FrameCallGraphEntry, ...]
-    awaited_by: tuple[FutureCallGraph, ...]
+    @dataclass(frozen=True, slots=True)
+    class FutureCallGraph:
+        future: Future[Any]
+        call_stack: tuple[FrameCallGraphEntry, ...]
+        awaited_by: tuple[FutureCallGraph, ...]
 
-@overload
-def capture_call_graph(future: None = None, /, *, depth: int = 1, limit: int | None = None) -> FutureCallGraph | None: ...
-@overload
-def capture_call_graph(future: Future[Any], /, *, depth: int = 1, limit: int | None = None) -> FutureCallGraph | None: ...
-def format_call_graph(future: Future[Any] | None = None, /, *, depth: int = 1, limit: int | None = None) -> str: ...
-def print_call_graph(
-    future: Future[Any] | None = None, /, *, file: SupportsWrite[str] | None = None, depth: int = 1, limit: int | None = None
-) -> None: ...
+    @overload
+    def capture_call_graph(future: None = None, /, *, depth: int = 1, limit: int | None = None) -> FutureCallGraph | None: ...
+    @overload
+    def capture_call_graph(future: Future[Any], /, *, depth: int = 1, limit: int | None = None) -> FutureCallGraph | None: ...
+    def format_call_graph(future: Future[Any] | None = None, /, *, depth: int = 1, limit: int | None = None) -> str: ...
+    def print_call_graph(
+        future: Future[Any] | None = None, /, *, file: SupportsWrite[str] | None = None, depth: int = 1, limit: int | None = None
+    ) -> None: ...
diff --git a/mypy/typeshed/stdlib/asyncio/protocols.pyi b/mypy/typeshed/stdlib/asyncio/protocols.pyi
index 5425336c49a8..2c52ad4be410 100644
--- a/mypy/typeshed/stdlib/asyncio/protocols.pyi
+++ b/mypy/typeshed/stdlib/asyncio/protocols.pyi
@@ -6,21 +6,26 @@ from typing import Any
 __all__ = ("BaseProtocol", "Protocol", "DatagramProtocol", "SubprocessProtocol", "BufferedProtocol")
 
 class BaseProtocol:
+    __slots__ = ()
     def connection_made(self, transport: transports.BaseTransport) -> None: ...
     def connection_lost(self, exc: Exception | None) -> None: ...
     def pause_writing(self) -> None: ...
     def resume_writing(self) -> None: ...
 
 class Protocol(BaseProtocol):
+    # Need annotation or mypy will complain about 'Cannot determine type of "__slots__" in base class'
+    __slots__: tuple[()] = ()
     def data_received(self, data: bytes) -> None: ...
     def eof_received(self) -> bool | None: ...
 
 class BufferedProtocol(BaseProtocol):
+    __slots__ = ()
     def get_buffer(self, sizehint: int) -> ReadableBuffer: ...
     def buffer_updated(self, nbytes: int) -> None: ...
     def eof_received(self) -> bool | None: ...
 
 class DatagramProtocol(BaseProtocol):
+    __slots__ = ()
     def connection_made(self, transport: transports.DatagramTransport) -> None: ...  # type: ignore[override]
     # addr can be a tuple[int, int] for some unusual protocols like socket.AF_NETLINK.
     # Use tuple[str | Any, int] to not cause typechecking issues on most usual cases.
@@ -30,6 +35,7 @@ class DatagramProtocol(BaseProtocol):
     def error_received(self, exc: Exception) -> None: ...
 
 class SubprocessProtocol(BaseProtocol):
+    __slots__: tuple[()] = ()
     def pipe_data_received(self, fd: int, data: bytes) -> None: ...
     def pipe_connection_lost(self, fd: int, exc: Exception | None) -> None: ...
     def process_exited(self) -> None: ...
diff --git a/mypy/typeshed/stdlib/asyncio/queues.pyi b/mypy/typeshed/stdlib/asyncio/queues.pyi
index 63cd98f53da3..2fa2226d0e6a 100644
--- a/mypy/typeshed/stdlib/asyncio/queues.pyi
+++ b/mypy/typeshed/stdlib/asyncio/queues.pyi
@@ -1,4 +1,5 @@
 import sys
+from _typeshed import SupportsRichComparisonT
 from asyncio.events import AbstractEventLoop
 from types import GenericAlias
 from typing import Any, Generic, TypeVar
@@ -50,5 +51,5 @@ class Queue(Generic[_T], _LoopBoundMixin):  # noqa: Y059
     if sys.version_info >= (3, 13):
         def shutdown(self, immediate: bool = False) -> None: ...
 
-class PriorityQueue(Queue[_T]): ...
+class PriorityQueue(Queue[SupportsRichComparisonT]): ...
 class LifoQueue(Queue[_T]): ...
diff --git a/mypy/typeshed/stdlib/asyncio/runners.pyi b/mypy/typeshed/stdlib/asyncio/runners.pyi
index caf5e4996cf4..919e6521f8a1 100644
--- a/mypy/typeshed/stdlib/asyncio/runners.pyi
+++ b/mypy/typeshed/stdlib/asyncio/runners.pyi
@@ -26,7 +26,7 @@ if sys.version_info >= (3, 11):
 
 if sys.version_info >= (3, 12):
     def run(
-        main: Coroutine[Any, Any, _T], *, debug: bool | None = ..., loop_factory: Callable[[], AbstractEventLoop] | None = ...
+        main: Coroutine[Any, Any, _T], *, debug: bool | None = None, loop_factory: Callable[[], AbstractEventLoop] | None = None
     ) -> _T: ...
 
 else:
diff --git a/mypy/typeshed/stdlib/asyncio/streams.pyi b/mypy/typeshed/stdlib/asyncio/streams.pyi
index 43df5ae2d0c8..33cffb11ed78 100644
--- a/mypy/typeshed/stdlib/asyncio/streams.pyi
+++ b/mypy/typeshed/stdlib/asyncio/streams.pyi
@@ -3,7 +3,7 @@ import sys
 from _typeshed import ReadableBuffer, StrPath
 from collections.abc import Awaitable, Callable, Iterable, Sequence, Sized
 from types import ModuleType
-from typing import Any, Protocol, SupportsIndex
+from typing import Any, Protocol, SupportsIndex, type_check_only
 from typing_extensions import Self, TypeAlias
 
 from . import events, protocols, transports
@@ -25,6 +25,7 @@ else:
 
 _ClientConnectedCallback: TypeAlias = Callable[[StreamReader, StreamWriter], Awaitable[None] | None]
 
+@type_check_only
 class _ReaduntilBuffer(ReadableBuffer, Sized, Protocol): ...
 
 if sys.version_info >= (3, 10):
@@ -33,7 +34,7 @@ if sys.version_info >= (3, 10):
         port: int | str | None = None,
         *,
         limit: int = 65536,
-        ssl_handshake_timeout: float | None = ...,
+        ssl_handshake_timeout: float | None = None,
         **kwds: Any,
     ) -> tuple[StreamReader, StreamWriter]: ...
     async def start_server(
@@ -42,7 +43,7 @@ if sys.version_info >= (3, 10):
         port: int | str | None = None,
         *,
         limit: int = 65536,
-        ssl_handshake_timeout: float | None = ...,
+        ssl_handshake_timeout: float | None = None,
         **kwds: Any,
     ) -> Server: ...
 
@@ -53,7 +54,7 @@ else:
         *,
         loop: events.AbstractEventLoop | None = None,
         limit: int = 65536,
-        ssl_handshake_timeout: float | None = ...,
+        ssl_handshake_timeout: float | None = None,
         **kwds: Any,
     ) -> tuple[StreamReader, StreamWriter]: ...
     async def start_server(
@@ -63,7 +64,7 @@ else:
         *,
         loop: events.AbstractEventLoop | None = None,
         limit: int = 65536,
-        ssl_handshake_timeout: float | None = ...,
+        ssl_handshake_timeout: float | None = None,
         **kwds: Any,
     ) -> Server: ...
 
diff --git a/mypy/typeshed/stdlib/asyncio/subprocess.pyi b/mypy/typeshed/stdlib/asyncio/subprocess.pyi
index 50d75391f36d..ceee2b5b90a0 100644
--- a/mypy/typeshed/stdlib/asyncio/subprocess.pyi
+++ b/mypy/typeshed/stdlib/asyncio/subprocess.pyi
@@ -60,7 +60,7 @@ if sys.version_info >= (3, 11):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         group: None | str | int = None,
         extra_groups: None | Collection[str | int] = None,
         user: None | str | int = None,
@@ -92,7 +92,7 @@ if sys.version_info >= (3, 11):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         group: None | str | int = None,
         extra_groups: None | Collection[str | int] = None,
         user: None | str | int = None,
@@ -126,7 +126,7 @@ elif sys.version_info >= (3, 10):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         group: None | str | int = None,
         extra_groups: None | Collection[str | int] = None,
         user: None | str | int = None,
@@ -157,7 +157,7 @@ elif sys.version_info >= (3, 10):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         group: None | str | int = None,
         extra_groups: None | Collection[str | int] = None,
         user: None | str | int = None,
@@ -191,7 +191,7 @@ else:  # >= 3.9
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         group: None | str | int = None,
         extra_groups: None | Collection[str | int] = None,
         user: None | str | int = None,
@@ -222,7 +222,7 @@ else:  # >= 3.9
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         group: None | str | int = None,
         extra_groups: None | Collection[str | int] = None,
         user: None | str | int = None,
diff --git a/mypy/typeshed/stdlib/asyncio/tasks.pyi b/mypy/typeshed/stdlib/asyncio/tasks.pyi
index e42151213e69..1442f7400a9c 100644
--- a/mypy/typeshed/stdlib/asyncio/tasks.pyi
+++ b/mypy/typeshed/stdlib/asyncio/tasks.pyi
@@ -8,7 +8,7 @@ from _asyncio import (
     _unregister_task as _unregister_task,
 )
 from collections.abc import AsyncIterator, Awaitable, Coroutine, Generator, Iterable, Iterator
-from typing import Any, Literal, Protocol, TypeVar, overload
+from typing import Any, Final, Literal, Protocol, TypeVar, overload, type_check_only
 from typing_extensions import TypeAlias
 
 from . import _CoroutineLike
@@ -82,11 +82,12 @@ else:
 
 _TaskYieldType: TypeAlias = Future[object] | None
 
-FIRST_COMPLETED = concurrent.futures.FIRST_COMPLETED
-FIRST_EXCEPTION = concurrent.futures.FIRST_EXCEPTION
-ALL_COMPLETED = concurrent.futures.ALL_COMPLETED
+FIRST_COMPLETED: Final = concurrent.futures.FIRST_COMPLETED
+FIRST_EXCEPTION: Final = concurrent.futures.FIRST_EXCEPTION
+ALL_COMPLETED: Final = concurrent.futures.ALL_COMPLETED
 
 if sys.version_info >= (3, 13):
+    @type_check_only
     class _SyncAndAsyncIterator(Iterator[_T_co], AsyncIterator[_T_co], Protocol[_T_co]): ...
 
     def as_completed(fs: Iterable[_FutureLike[_T]], *, timeout: float | None = None) -> _SyncAndAsyncIterator[Future[_T]]: ...
@@ -423,9 +424,29 @@ if sys.version_info >= (3, 12):
 else:
     def current_task(loop: AbstractEventLoop | None = None) -> Task[Any] | None: ...
 
+if sys.version_info >= (3, 14):
+    def eager_task_factory(
+        loop: AbstractEventLoop | None,
+        coro: _TaskCompatibleCoro[_T_co],
+        *,
+        name: str | None = None,
+        context: Context | None = None,
+        eager_start: bool = True,
+    ) -> Task[_T_co]: ...
+
+elif sys.version_info >= (3, 12):
+    def eager_task_factory(
+        loop: AbstractEventLoop | None,
+        coro: _TaskCompatibleCoro[_T_co],
+        *,
+        name: str | None = None,
+        context: Context | None = None,
+    ) -> Task[_T_co]: ...
+
 if sys.version_info >= (3, 12):
     _TaskT_co = TypeVar("_TaskT_co", bound=Task[Any], covariant=True)
 
+    @type_check_only
     class _CustomTaskConstructor(Protocol[_TaskT_co]):
         def __call__(
             self,
@@ -438,6 +459,7 @@ if sys.version_info >= (3, 12):
             eager_start: bool,
         ) -> _TaskT_co: ...
 
+    @type_check_only
     class _EagerTaskFactoryType(Protocol[_TaskT_co]):
         def __call__(
             self,
@@ -451,10 +473,3 @@ if sys.version_info >= (3, 12):
     def create_eager_task_factory(
         custom_task_constructor: _CustomTaskConstructor[_TaskT_co],
     ) -> _EagerTaskFactoryType[_TaskT_co]: ...
-    def eager_task_factory(
-        loop: AbstractEventLoop | None,
-        coro: _TaskCompatibleCoro[_T_co],
-        *,
-        name: str | None = None,
-        context: Context | None = None,
-    ) -> Task[_T_co]: ...
diff --git a/mypy/typeshed/stdlib/asyncio/tools.pyi b/mypy/typeshed/stdlib/asyncio/tools.pyi
new file mode 100644
index 000000000000..65c7f27e0b85
--- /dev/null
+++ b/mypy/typeshed/stdlib/asyncio/tools.pyi
@@ -0,0 +1,41 @@
+from collections.abc import Iterable
+from enum import Enum
+from typing import NamedTuple, SupportsIndex, type_check_only
+
+@type_check_only
+class _AwaitedInfo(NamedTuple):  # AwaitedInfo_Type from _remote_debugging
+    thread_id: int
+    awaited_by: list[_TaskInfo]
+
+@type_check_only
+class _TaskInfo(NamedTuple):  # TaskInfo_Type from _remote_debugging
+    task_id: int
+    task_name: str
+    coroutine_stack: list[_CoroInfo]
+    awaited_by: list[_CoroInfo]
+
+@type_check_only
+class _CoroInfo(NamedTuple):  # CoroInfo_Type from _remote_debugging
+    call_stack: list[_FrameInfo]
+    task_name: int | str
+
+@type_check_only
+class _FrameInfo(NamedTuple):  # FrameInfo_Type from _remote_debugging
+    filename: str
+    lineno: int
+    funcname: str
+
+class NodeType(Enum):
+    COROUTINE = 1
+    TASK = 2
+
+class CycleFoundException(Exception):
+    cycles: list[list[int]]
+    id2name: dict[int, str]
+    def __init__(self, cycles: list[list[int]], id2name: dict[int, str]) -> None: ...
+
+def get_all_awaited_by(pid: SupportsIndex) -> list[_AwaitedInfo]: ...
+def build_async_tree(result: Iterable[_AwaitedInfo], task_emoji: str = "(T)", cor_emoji: str = "") -> list[list[str]]: ...
+def build_task_table(result: Iterable[_AwaitedInfo]) -> list[list[int | str]]: ...
+def display_awaited_by_tasks_table(pid: SupportsIndex) -> None: ...
+def display_awaited_by_tasks_tree(pid: SupportsIndex) -> None: ...
diff --git a/mypy/typeshed/stdlib/asyncio/transports.pyi b/mypy/typeshed/stdlib/asyncio/transports.pyi
index bce54897f18f..cc870d5e0b9a 100644
--- a/mypy/typeshed/stdlib/asyncio/transports.pyi
+++ b/mypy/typeshed/stdlib/asyncio/transports.pyi
@@ -8,6 +8,7 @@ from typing import Any
 __all__ = ("BaseTransport", "ReadTransport", "WriteTransport", "Transport", "DatagramTransport", "SubprocessTransport")
 
 class BaseTransport:
+    __slots__ = ("_extra",)
     def __init__(self, extra: Mapping[str, Any] | None = None) -> None: ...
     def get_extra_info(self, name: str, default: Any = None) -> Any: ...
     def is_closing(self) -> bool: ...
@@ -16,11 +17,13 @@ class BaseTransport:
     def get_protocol(self) -> BaseProtocol: ...
 
 class ReadTransport(BaseTransport):
+    __slots__ = ()
     def is_reading(self) -> bool: ...
     def pause_reading(self) -> None: ...
     def resume_reading(self) -> None: ...
 
 class WriteTransport(BaseTransport):
+    __slots__ = ()
     def set_write_buffer_limits(self, high: int | None = None, low: int | None = None) -> None: ...
     def get_write_buffer_size(self) -> int: ...
     def get_write_buffer_limits(self) -> tuple[int, int]: ...
@@ -32,13 +35,16 @@ class WriteTransport(BaseTransport):
     def can_write_eof(self) -> bool: ...
     def abort(self) -> None: ...
 
-class Transport(ReadTransport, WriteTransport): ...
+class Transport(ReadTransport, WriteTransport):
+    __slots__ = ()
 
 class DatagramTransport(BaseTransport):
+    __slots__ = ()
     def sendto(self, data: bytes | bytearray | memoryview, addr: _Address | None = None) -> None: ...
     def abort(self) -> None: ...
 
 class SubprocessTransport(BaseTransport):
+    __slots__ = ()
     def get_pid(self) -> int: ...
     def get_returncode(self) -> int | None: ...
     def get_pipe_transport(self, fd: int) -> BaseTransport | None: ...
@@ -47,4 +53,5 @@ class SubprocessTransport(BaseTransport):
     def kill(self) -> None: ...
 
 class _FlowControlMixin(Transport):
+    __slots__ = ("_loop", "_protocol_paused", "_high_water", "_low_water")
     def __init__(self, extra: Mapping[str, Any] | None = None, loop: AbstractEventLoop | None = None) -> None: ...
diff --git a/mypy/typeshed/stdlib/asyncio/trsock.pyi b/mypy/typeshed/stdlib/asyncio/trsock.pyi
index e74cf6fd4e05..492f1e42adf2 100644
--- a/mypy/typeshed/stdlib/asyncio/trsock.pyi
+++ b/mypy/typeshed/stdlib/asyncio/trsock.pyi
@@ -5,7 +5,7 @@ from builtins import type as Type  # alias to avoid name clashes with property n
 from collections.abc import Iterable
 from types import TracebackType
 from typing import Any, BinaryIO, NoReturn, overload
-from typing_extensions import TypeAlias
+from typing_extensions import TypeAlias, deprecated
 
 # These are based in socket, maybe move them out into _typeshed.pyi or such
 _Address: TypeAlias = socket._Address
@@ -14,6 +14,7 @@ _WriteBuffer: TypeAlias = bytearray | memoryview
 _CMSG: TypeAlias = tuple[int, int, bytes]
 
 class TransportSocket:
+    __slots__ = ("_sock",)
     def __init__(self, sock: socket.socket) -> None: ...
     @property
     def family(self) -> int: ...
@@ -42,53 +43,87 @@ class TransportSocket:
     def setblocking(self, flag: bool) -> None: ...
     if sys.version_info < (3, 11):
         def _na(self, what: str) -> None: ...
+        @deprecated("Removed in Python 3.11")
         def accept(self) -> tuple[socket.socket, _RetAddress]: ...
+        @deprecated("Removed in Python 3.11")
         def connect(self, address: _Address) -> None: ...
+        @deprecated("Removed in Python 3.11")
         def connect_ex(self, address: _Address) -> int: ...
+        @deprecated("Removed in Python 3.11")
         def bind(self, address: _Address) -> None: ...
         if sys.platform == "win32":
+            @deprecated("Removed in Python 3.11")
             def ioctl(self, control: int, option: int | tuple[int, int, int] | bool) -> None: ...
         else:
+            @deprecated("Removed in Python 3.11")
             def ioctl(self, control: int, option: int | tuple[int, int, int] | bool) -> NoReturn: ...
 
+        @deprecated("Removed in Python 3.11")
         def listen(self, backlog: int = ..., /) -> None: ...
+        @deprecated("Removed in Python 3.11")
         def makefile(self) -> BinaryIO: ...
-        def sendfile(self, file: BinaryIO, offset: int = ..., count: int | None = ...) -> int: ...
+        @deprecated("Rmoved in Python 3.11")
+        def sendfile(self, file: BinaryIO, offset: int = 0, count: int | None = None) -> int: ...
+        @deprecated("Removed in Python 3.11")
         def close(self) -> None: ...
+        @deprecated("Removed in Python 3.11")
         def detach(self) -> int: ...
         if sys.platform == "linux":
+            @deprecated("Removed in Python 3.11")
             def sendmsg_afalg(
-                self, msg: Iterable[ReadableBuffer] = ..., *, op: int, iv: Any = ..., assoclen: int = ..., flags: int = ...
+                self, msg: Iterable[ReadableBuffer] = ..., *, op: int, iv: Any = ..., assoclen: int = ..., flags: int = 0
             ) -> int: ...
         else:
+            @deprecated("Removed in Python 3.11.")
             def sendmsg_afalg(
-                self, msg: Iterable[ReadableBuffer] = ..., *, op: int, iv: Any = ..., assoclen: int = ..., flags: int = ...
+                self, msg: Iterable[ReadableBuffer] = ..., *, op: int, iv: Any = ..., assoclen: int = ..., flags: int = 0
             ) -> NoReturn: ...
 
+        @deprecated("Removed in Python 3.11.")
         def sendmsg(
-            self, buffers: Iterable[ReadableBuffer], ancdata: Iterable[_CMSG] = ..., flags: int = ..., address: _Address = ..., /
+            self,
+            buffers: Iterable[ReadableBuffer],
+            ancdata: Iterable[_CMSG] = ...,
+            flags: int = 0,
+            address: _Address | None = None,
+            /,
         ) -> int: ...
         @overload
+        @deprecated("Removed in Python 3.11.")
         def sendto(self, data: ReadableBuffer, address: _Address) -> int: ...
         @overload
+        @deprecated("Removed in Python 3.11.")
         def sendto(self, data: ReadableBuffer, flags: int, address: _Address) -> int: ...
-        def send(self, data: ReadableBuffer, flags: int = ...) -> int: ...
-        def sendall(self, data: ReadableBuffer, flags: int = ...) -> None: ...
+        @deprecated("Removed in Python 3.11.")
+        def send(self, data: ReadableBuffer, flags: int = 0) -> int: ...
+        @deprecated("Removed in Python 3.11.")
+        def sendall(self, data: ReadableBuffer, flags: int = 0) -> None: ...
+        @deprecated("Removed in Python 3.11.")
         def set_inheritable(self, inheritable: bool) -> None: ...
         if sys.platform == "win32":
+            @deprecated("Removed in Python 3.11.")
             def share(self, process_id: int) -> bytes: ...
         else:
+            @deprecated("Removed in Python 3.11.")
             def share(self, process_id: int) -> NoReturn: ...
 
-        def recv_into(self, buffer: _WriteBuffer, nbytes: int = ..., flags: int = ...) -> int: ...
-        def recvfrom_into(self, buffer: _WriteBuffer, nbytes: int = ..., flags: int = ...) -> tuple[int, _RetAddress]: ...
+        @deprecated("Removed in Python 3.11.")
+        def recv_into(self, buffer: _WriteBuffer, nbytes: int = 0, flags: int = 0) -> int: ...
+        @deprecated("Removed in Python 3.11.")
+        def recvfrom_into(self, buffer: _WriteBuffer, nbytes: int = 0, flags: int = 0) -> tuple[int, _RetAddress]: ...
+        @deprecated("Removed in Python 3.11.")
         def recvmsg_into(
-            self, buffers: Iterable[_WriteBuffer], ancbufsize: int = ..., flags: int = ..., /
+            self, buffers: Iterable[_WriteBuffer], ancbufsize: int = 0, flags: int = 0, /
         ) -> tuple[int, list[_CMSG], int, Any]: ...
-        def recvmsg(self, bufsize: int, ancbufsize: int = ..., flags: int = ..., /) -> tuple[bytes, list[_CMSG], int, Any]: ...
-        def recvfrom(self, bufsize: int, flags: int = ...) -> tuple[bytes, _RetAddress]: ...
-        def recv(self, bufsize: int, flags: int = ...) -> bytes: ...
+        @deprecated("Removed in Python 3.11.")
+        def recvmsg(self, bufsize: int, ancbufsize: int = 0, flags: int = 0, /) -> tuple[bytes, list[_CMSG], int, Any]: ...
+        @deprecated("Removed in Python 3.11.")
+        def recvfrom(self, bufsize: int, flags: int = 0) -> tuple[bytes, _RetAddress]: ...
+        @deprecated("Removed in Python 3.11.")
+        def recv(self, bufsize: int, flags: int = 0) -> bytes: ...
+        @deprecated("Removed in Python 3.11.")
         def __enter__(self) -> socket.socket: ...
+        @deprecated("Removed in Python 3.11.")
         def __exit__(
             self, exc_type: Type[BaseException] | None, exc_val: BaseException | None, exc_tb: TracebackType | None
         ) -> None: ...
diff --git a/mypy/typeshed/stdlib/asyncio/unix_events.pyi b/mypy/typeshed/stdlib/asyncio/unix_events.pyi
index 49f200dcdcae..9071ee9a2fa7 100644
--- a/mypy/typeshed/stdlib/asyncio/unix_events.pyi
+++ b/mypy/typeshed/stdlib/asyncio/unix_events.pyi
@@ -16,7 +16,7 @@ _Ts = TypeVarTuple("_Ts")
 # Keep asyncio.__all__ updated with any changes to __all__ here
 if sys.platform != "win32":
     if sys.version_info >= (3, 14):
-        __all__ = ("SelectorEventLoop", "_DefaultEventLoopPolicy", "EventLoop")
+        __all__ = ("SelectorEventLoop", "EventLoop")
     elif sys.version_info >= (3, 13):
         # Adds EventLoop
         __all__ = (
@@ -48,7 +48,7 @@ if sys.platform != "win32":
 # So, it is special cased.
 if sys.version_info < (3, 14):
     if sys.version_info >= (3, 12):
-        @deprecated("Deprecated as of Python 3.12; will be removed in Python 3.14")
+        @deprecated("Deprecated since Python 3.12; removed in Python 3.14.")
         class AbstractChildWatcher:
             @abstractmethod
             def add_child_handler(
@@ -100,7 +100,7 @@ if sys.platform != "win32":
                 def is_active(self) -> bool: ...
                 def attach_loop(self, loop: events.AbstractEventLoop | None) -> None: ...
 
-            @deprecated("Deprecated as of Python 3.12; will be removed in Python 3.14")
+            @deprecated("Deprecated since Python 3.12; removed in Python 3.14.")
             class SafeChildWatcher(BaseChildWatcher):
                 def __enter__(self) -> Self: ...
                 def __exit__(
@@ -111,7 +111,7 @@ if sys.platform != "win32":
                 ) -> None: ...
                 def remove_child_handler(self, pid: int) -> bool: ...
 
-            @deprecated("Deprecated as of Python 3.12; will be removed in Python 3.14")
+            @deprecated("Deprecated since Python 3.12; removed in Python 3.14.")
             class FastChildWatcher(BaseChildWatcher):
                 def __enter__(self) -> Self: ...
                 def __exit__(
@@ -171,9 +171,9 @@ if sys.platform != "win32":
     else:
         class _UnixDefaultEventLoopPolicy(events.BaseDefaultEventLoopPolicy):
             if sys.version_info >= (3, 12):
-                @deprecated("Deprecated as of Python 3.12; will be removed in Python 3.14")
+                @deprecated("Deprecated since Python 3.12; removed in Python 3.14.")
                 def get_child_watcher(self) -> AbstractChildWatcher: ...
-                @deprecated("Deprecated as of Python 3.12; will be removed in Python 3.14")
+                @deprecated("Deprecated since Python 3.12; removed in Python 3.14.")
                 def set_child_watcher(self, watcher: AbstractChildWatcher | None) -> None: ...
             else:
                 def get_child_watcher(self) -> AbstractChildWatcher: ...
@@ -191,7 +191,7 @@ if sys.platform != "win32":
 
     if sys.version_info < (3, 14):
         if sys.version_info >= (3, 12):
-            @deprecated("Deprecated as of Python 3.12; will be removed in Python 3.14")
+            @deprecated("Deprecated since Python 3.12; removed in Python 3.14.")
             class MultiLoopChildWatcher(AbstractChildWatcher):
                 def is_active(self) -> bool: ...
                 def close(self) -> None: ...
diff --git a/mypy/typeshed/stdlib/asyncio/windows_events.pyi b/mypy/typeshed/stdlib/asyncio/windows_events.pyi
index b454aca1f262..a32381bfb3e6 100644
--- a/mypy/typeshed/stdlib/asyncio/windows_events.pyi
+++ b/mypy/typeshed/stdlib/asyncio/windows_events.pyi
@@ -116,6 +116,6 @@ if sys.platform == "win32":
     if sys.version_info >= (3, 14):
         _DefaultEventLoopPolicy = _WindowsProactorEventLoopPolicy
     else:
-        DefaultEventLoopPolicy = WindowsSelectorEventLoopPolicy
+        DefaultEventLoopPolicy = WindowsProactorEventLoopPolicy
     if sys.version_info >= (3, 13):
         EventLoop = ProactorEventLoop
diff --git a/mypy/typeshed/stdlib/asyncio/windows_utils.pyi b/mypy/typeshed/stdlib/asyncio/windows_utils.pyi
index 4fa014532376..5cedd61b5f4a 100644
--- a/mypy/typeshed/stdlib/asyncio/windows_utils.pyi
+++ b/mypy/typeshed/stdlib/asyncio/windows_utils.pyi
@@ -9,8 +9,8 @@ if sys.platform == "win32":
     __all__ = ("pipe", "Popen", "PIPE", "PipeHandle")
 
     BUFSIZE: Final = 8192
-    PIPE = subprocess.PIPE
-    STDOUT = subprocess.STDOUT
+    PIPE: Final = subprocess.PIPE
+    STDOUT: Final = subprocess.STDOUT
     def pipe(*, duplex: bool = False, overlapped: tuple[bool, bool] = (True, True), bufsize: int = 8192) -> tuple[int, int]: ...
 
     class PipeHandle:
@@ -34,9 +34,9 @@ if sys.platform == "win32":
         def __new__(
             cls,
             args: subprocess._CMD,
-            stdin: subprocess._FILE | None = ...,
-            stdout: subprocess._FILE | None = ...,
-            stderr: subprocess._FILE | None = ...,
+            stdin: subprocess._FILE | None = None,
+            stdout: subprocess._FILE | None = None,
+            stderr: subprocess._FILE | None = None,
             **kwds: Any,
         ) -> Self: ...
         def __init__(
diff --git a/mypy/typeshed/stdlib/bdb.pyi b/mypy/typeshed/stdlib/bdb.pyi
index b73f894093ce..b6be2210ffe2 100644
--- a/mypy/typeshed/stdlib/bdb.pyi
+++ b/mypy/typeshed/stdlib/bdb.pyi
@@ -81,8 +81,8 @@ class Bdb:
     def get_bpbynumber(self, arg: SupportsInt) -> Breakpoint: ...
     def get_break(self, filename: str, lineno: int) -> bool: ...
     def get_breaks(self, filename: str, lineno: int) -> list[Breakpoint]: ...
-    def get_file_breaks(self, filename: str) -> list[Breakpoint]: ...
-    def get_all_breaks(self) -> list[Breakpoint]: ...
+    def get_file_breaks(self, filename: str) -> list[int]: ...
+    def get_all_breaks(self) -> dict[str, list[int]]: ...
     def get_stack(self, f: FrameType | None, t: TracebackType | None) -> tuple[list[tuple[FrameType, int]], int]: ...
     def format_stack_entry(self, frame_lineno: tuple[FrameType, int], lprefix: str = ": ") -> str: ...
     def run(
diff --git a/mypy/typeshed/stdlib/binascii.pyi b/mypy/typeshed/stdlib/binascii.pyi
index 32e018c653cb..5606d5cdf74d 100644
--- a/mypy/typeshed/stdlib/binascii.pyi
+++ b/mypy/typeshed/stdlib/binascii.pyi
@@ -1,6 +1,6 @@
 import sys
 from _typeshed import ReadableBuffer
-from typing_extensions import TypeAlias
+from typing_extensions import TypeAlias, deprecated
 
 # Many functions in binascii accept buffer objects
 # or ASCII-only strings.
@@ -20,15 +20,19 @@ def a2b_qp(data: _AsciiBuffer, header: bool = False) -> bytes: ...
 def b2a_qp(data: ReadableBuffer, quotetabs: bool = False, istext: bool = True, header: bool = False) -> bytes: ...
 
 if sys.version_info < (3, 11):
+    @deprecated("Deprecated since Python 3.9; removed in Python 3.11.")
     def a2b_hqx(data: _AsciiBuffer, /) -> bytes: ...
+    @deprecated("Deprecated since Python 3.9; removed in Python 3.11.")
     def rledecode_hqx(data: ReadableBuffer, /) -> bytes: ...
+    @deprecated("Deprecated since Python 3.9; removed in Python 3.11.")
     def rlecode_hqx(data: ReadableBuffer, /) -> bytes: ...
+    @deprecated("Deprecated since Python 3.9; removed in Python 3.11.")
     def b2a_hqx(data: ReadableBuffer, /) -> bytes: ...
 
 def crc_hqx(data: ReadableBuffer, crc: int, /) -> int: ...
 def crc32(data: ReadableBuffer, crc: int = 0, /) -> int: ...
-def b2a_hex(data: ReadableBuffer, sep: str | bytes = ..., bytes_per_sep: int = ...) -> bytes: ...
-def hexlify(data: ReadableBuffer, sep: str | bytes = ..., bytes_per_sep: int = ...) -> bytes: ...
+def b2a_hex(data: ReadableBuffer, sep: str | bytes = ..., bytes_per_sep: int = 1) -> bytes: ...
+def hexlify(data: ReadableBuffer, sep: str | bytes = ..., bytes_per_sep: int = 1) -> bytes: ...
 def a2b_hex(hexstr: _AsciiBuffer, /) -> bytes: ...
 def unhexlify(hexstr: _AsciiBuffer, /) -> bytes: ...
 
diff --git a/mypy/typeshed/stdlib/builtins.pyi b/mypy/typeshed/stdlib/builtins.pyi
index 6e983ef9ef29..ca8d56cb4297 100644
--- a/mypy/typeshed/stdlib/builtins.pyi
+++ b/mypy/typeshed/stdlib/builtins.pyi
@@ -70,6 +70,7 @@ from typing_extensions import (  # noqa: Y023
     TypeIs,
     TypeVarTuple,
     deprecated,
+    disjoint_base,
 )
 
 if sys.version_info >= (3, 14):
@@ -102,6 +103,7 @@ _StopT_co = TypeVar("_StopT_co", covariant=True, default=_StartT_co)  #  slice[A
 # FIXME: https://github.com/python/typing/issues/213 (replace step=start|stop with step=start&stop)
 _StepT_co = TypeVar("_StepT_co", covariant=True, default=_StartT_co | _StopT_co)  #  slice[A,B] -> slice[A, B, A|B]
 
+@disjoint_base
 class object:
     __doc__: str | None
     __dict__: dict[str, Any]
@@ -137,6 +139,7 @@ class object:
     @classmethod
     def __subclasshook__(cls, subclass: type, /) -> bool: ...
 
+@disjoint_base
 class staticmethod(Generic[_P, _R_co]):
     @property
     def __func__(self) -> Callable[_P, _R_co]: ...
@@ -157,6 +160,7 @@ class staticmethod(Generic[_P, _R_co]):
         def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
         __annotate__: AnnotateFunc | None
 
+@disjoint_base
 class classmethod(Generic[_T, _P, _R_co]):
     @property
     def __func__(self) -> Callable[Concatenate[type[_T], _P], _R_co]: ...
@@ -176,6 +180,7 @@ class classmethod(Generic[_T, _P, _R_co]):
         def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
         __annotate__: AnnotateFunc | None
 
+@disjoint_base
 class type:
     # object.__base__ is None. Otherwise, it would be a type.
     @property
@@ -228,6 +233,7 @@ class type:
     if sys.version_info >= (3, 14):
         __annotate__: AnnotateFunc | None
 
+@disjoint_base
 class super:
     @overload
     def __init__(self, t: Any, obj: Any, /) -> None: ...
@@ -240,6 +246,7 @@ _PositiveInteger: TypeAlias = Literal[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,
 _NegativeInteger: TypeAlias = Literal[-1, -2, -3, -4, -5, -6, -7, -8, -9, -10, -11, -12, -13, -14, -15, -16, -17, -18, -19, -20]
 _LiteralInteger = _PositiveInteger | _NegativeInteger | Literal[0]  # noqa: Y026  # TODO: Use TypeAlias once mypy bugs are fixed
 
+@disjoint_base
 class int:
     @overload
     def __new__(cls, x: ConvertibleToInt = ..., /) -> Self: ...
@@ -348,7 +355,9 @@ class int:
     def __hash__(self) -> int: ...
     def __bool__(self) -> bool: ...
     def __index__(self) -> int: ...
+    def __format__(self, format_spec: str, /) -> str: ...
 
+@disjoint_base
 class float:
     def __new__(cls, x: ConvertibleToFloat = ..., /) -> Self: ...
     def as_integer_ratio(self) -> tuple[int, int]: ...
@@ -409,10 +418,12 @@ class float:
     def __abs__(self) -> float: ...
     def __hash__(self) -> int: ...
     def __bool__(self) -> bool: ...
+    def __format__(self, format_spec: str, /) -> str: ...
     if sys.version_info >= (3, 14):
         @classmethod
         def from_number(cls, number: float | SupportsIndex | SupportsFloat, /) -> Self: ...
 
+@disjoint_base
 class complex:
     # Python doesn't currently accept SupportsComplex for the second argument
     @overload
@@ -445,18 +456,22 @@ class complex:
     def __abs__(self) -> float: ...
     def __hash__(self) -> int: ...
     def __bool__(self) -> bool: ...
+    def __format__(self, format_spec: str, /) -> str: ...
     if sys.version_info >= (3, 11):
         def __complex__(self) -> complex: ...
     if sys.version_info >= (3, 14):
         @classmethod
         def from_number(cls, number: complex | SupportsComplex | SupportsFloat | SupportsIndex, /) -> Self: ...
 
+@type_check_only
 class _FormatMapMapping(Protocol):
     def __getitem__(self, key: str, /) -> Any: ...
 
+@type_check_only
 class _TranslateTable(Protocol):
     def __getitem__(self, key: int, /) -> str | int | None: ...
 
+@disjoint_base
 class str(Sequence[str]):
     @overload
     def __new__(cls, object: object = ...) -> Self: ...
@@ -542,7 +557,9 @@ class str(Sequence[str]):
     def __ne__(self, value: object, /) -> bool: ...
     def __rmul__(self, value: SupportsIndex, /) -> str: ...  # type: ignore[misc]
     def __getnewargs__(self) -> tuple[str]: ...
+    def __format__(self, format_spec: str, /) -> str: ...
 
+@disjoint_base
 class bytes(Sequence[int]):
     @overload
     def __new__(cls, o: Iterable[SupportsIndex] | SupportsIndex | SupportsBytes | ReadableBuffer, /) -> Self: ...
@@ -609,7 +626,7 @@ class bytes(Sequence[int]):
     def strip(self, bytes: ReadableBuffer | None = None, /) -> bytes: ...
     def swapcase(self) -> bytes: ...
     def title(self) -> bytes: ...
-    def translate(self, table: ReadableBuffer | None, /, delete: bytes = b"") -> bytes: ...
+    def translate(self, table: ReadableBuffer | None, /, delete: ReadableBuffer = b"") -> bytes: ...
     def upper(self) -> bytes: ...
     def zfill(self, width: SupportsIndex, /) -> bytes: ...
     @classmethod
@@ -641,6 +658,7 @@ class bytes(Sequence[int]):
 
     def __buffer__(self, flags: int, /) -> memoryview: ...
 
+@disjoint_base
 class bytearray(MutableSequence[int]):
     @overload
     def __init__(self) -> None: ...
@@ -905,6 +923,8 @@ class slice(Generic[_StartT_co, _StopT_co, _StepT_co]):
 
     def indices(self, len: SupportsIndex, /) -> tuple[int, int, int]: ...
 
+# Making this a disjoint_base upsets pyright
+# @disjoint_base
 class tuple(Sequence[_T_co]):
     def __new__(cls, iterable: Iterable[_T_co] = ..., /) -> Self: ...
     def __len__(self) -> int: ...
@@ -981,6 +1001,7 @@ class function:
     # mypy uses `builtins.function.__get__` to represent methods, properties, and getset_descriptors so we type the return as Any.
     def __get__(self, instance: object, owner: type | None = None, /) -> Any: ...
 
+@disjoint_base
 class list(MutableSequence[_T]):
     @overload
     def __init__(self) -> None: ...
@@ -1035,6 +1056,7 @@ class list(MutableSequence[_T]):
     def __eq__(self, value: object, /) -> bool: ...
     def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
+@disjoint_base
 class dict(MutableMapping[_KT, _VT]):
     # __init__ should be kept roughly in line with `collections.UserDict.__init__`, which has similar semantics
     # Also multiprocessing.managers.SyncManager.dict()
@@ -1117,6 +1139,7 @@ class dict(MutableMapping[_KT, _VT]):
     @overload
     def __ior__(self, value: Iterable[tuple[_KT, _VT]], /) -> Self: ...
 
+@disjoint_base
 class set(MutableSet[_T]):
     @overload
     def __init__(self) -> None: ...
@@ -1156,6 +1179,7 @@ class set(MutableSet[_T]):
     __hash__: ClassVar[None]  # type: ignore[assignment]
     def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
+@disjoint_base
 class frozenset(AbstractSet[_T_co]):
     @overload
     def __new__(cls) -> Self: ...
@@ -1184,6 +1208,7 @@ class frozenset(AbstractSet[_T_co]):
     def __hash__(self) -> int: ...
     def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
+@disjoint_base
 class enumerate(Iterator[tuple[int, _T]]):
     def __new__(cls, iterable: Iterable[_T], start: int = 0) -> Self: ...
     def __iter__(self) -> Self: ...
@@ -1215,6 +1240,7 @@ class range(Sequence[int]):
     def __getitem__(self, key: slice, /) -> range: ...
     def __reversed__(self) -> Iterator[int]: ...
 
+@disjoint_base
 class property:
     fget: Callable[[Any], Any] | None
     fset: Callable[[Any, Any], None] | None
@@ -1240,6 +1266,9 @@ class property:
     def __set__(self, instance: Any, value: Any, /) -> None: ...
     def __delete__(self, instance: Any, /) -> None: ...
 
+# This class does not exist at runtime, but stubtest complains if it's marked as
+# @type_check_only because it has an alias that does exist at runtime. See mypy#19568.
+# @type_check_only
 @final
 class _NotImplementedType(Any):
     __call__: None
@@ -1257,7 +1286,7 @@ def chr(i: int | SupportsIndex, /) -> str: ...
 
 if sys.version_info >= (3, 10):
     def aiter(async_iterable: SupportsAiter[_SupportsAnextT_co], /) -> _SupportsAnextT_co: ...
-
+    @type_check_only
     class _SupportsSynchronousAnext(Protocol[_AwaitableT_co]):
         def __anext__(self) -> _AwaitableT_co: ...
 
@@ -1375,6 +1404,7 @@ else:
 
 exit: _sitebuiltins.Quitter
 
+@disjoint_base
 class filter(Iterator[_T]):
     @overload
     def __new__(cls, function: None, iterable: Iterable[_T | None], /) -> Self: ...
@@ -1413,7 +1443,7 @@ help: _sitebuiltins._Helper
 def hex(number: int | SupportsIndex, /) -> str: ...
 def id(obj: object, /) -> int: ...
 def input(prompt: object = "", /) -> str: ...
-
+@type_check_only
 class _GetItemIterable(Protocol[_T_co]):
     def __getitem__(self, i: int, /) -> _T_co: ...
 
@@ -1426,7 +1456,6 @@ def iter(object: Callable[[], _T | None], sentinel: None, /) -> Iterator[_T]: ..
 @overload
 def iter(object: Callable[[], _T], sentinel: object, /) -> Iterator[_T]: ...
 
-# Keep this alias in sync with unittest.case._ClassInfo
 if sys.version_info >= (3, 10):
     _ClassInfo: TypeAlias = type | types.UnionType | tuple[_ClassInfo, ...]
 else:
@@ -1439,7 +1468,7 @@ def len(obj: Sized, /) -> int: ...
 license: _sitebuiltins._Printer
 
 def locals() -> dict[str, Any]: ...
-
+@disjoint_base
 class map(Iterator[_S]):
     # 3.14 adds `strict` argument.
     if sys.version_info >= (3, 14):
@@ -1669,7 +1698,7 @@ def open(
     opener: _Opener | None = None,
 ) -> IO[Any]: ...
 def ord(c: str | bytes | bytearray, /) -> int: ...
-
+@type_check_only
 class _SupportsWriteAndFlush(SupportsWrite[_T_contra], SupportsFlush, Protocol[_T_contra]): ...
 
 @overload
@@ -1688,12 +1717,15 @@ def print(
 _E_contra = TypeVar("_E_contra", contravariant=True)
 _M_contra = TypeVar("_M_contra", contravariant=True)
 
+@type_check_only
 class _SupportsPow2(Protocol[_E_contra, _T_co]):
     def __pow__(self, other: _E_contra, /) -> _T_co: ...
 
+@type_check_only
 class _SupportsPow3NoneOnly(Protocol[_E_contra, _T_co]):
     def __pow__(self, other: _E_contra, modulo: None = None, /) -> _T_co: ...
 
+@type_check_only
 class _SupportsPow3(Protocol[_E_contra, _M_contra, _T_co]):
     def __pow__(self, other: _E_contra, modulo: _M_contra, /) -> _T_co: ...
 
@@ -1743,6 +1775,7 @@ def pow(base: _SupportsSomeKindOfPow, exp: complex, mod: None = None) -> complex
 
 quit: _sitebuiltins.Quitter
 
+@disjoint_base
 class reversed(Iterator[_T]):
     @overload
     def __new__(cls, sequence: Reversible[_T], /) -> Iterator[_T]: ...  # type: ignore[misc]
@@ -1758,9 +1791,11 @@ def repr(obj: object, /) -> str: ...
 # and https://github.com/python/typeshed/pull/9151
 # on why we don't use `SupportsRound` from `typing.pyi`
 
+@type_check_only
 class _SupportsRound1(Protocol[_T_co]):
     def __round__(self) -> _T_co: ...
 
+@type_check_only
 class _SupportsRound2(Protocol[_T_co]):
     def __round__(self, ndigits: int, /) -> _T_co: ...
 
@@ -1782,6 +1817,7 @@ def sorted(iterable: Iterable[_T], /, *, key: Callable[[_T], SupportsRichCompari
 _AddableT1 = TypeVar("_AddableT1", bound=SupportsAdd[Any, Any])
 _AddableT2 = TypeVar("_AddableT2", bound=SupportsAdd[Any, Any])
 
+@type_check_only
 class _SupportsSumWithNoDefaultGiven(SupportsAdd[Any, Any], SupportsRAdd[int, Any], Protocol): ...
 
 _SupportsSumNoDefaultT = TypeVar("_SupportsSumNoDefaultT", bound=_SupportsSumWithNoDefaultGiven)
@@ -1803,7 +1839,7 @@ def sum(iterable: Iterable[_AddableT1], /, start: _AddableT2) -> _AddableT1 | _A
 def vars(object: type, /) -> types.MappingProxyType[str, Any]: ...
 @overload
 def vars(object: Any = ..., /) -> dict[str, Any]: ...
-
+@disjoint_base
 class zip(Iterator[_T_co]):
     if sys.version_info >= (3, 10):
         @overload
@@ -1907,6 +1943,7 @@ else:
 
     Ellipsis: ellipsis
 
+@disjoint_base
 class BaseException:
     args: tuple[Any, ...]
     __cause__: BaseException | None
@@ -1925,14 +1962,17 @@ class BaseException:
 class GeneratorExit(BaseException): ...
 class KeyboardInterrupt(BaseException): ...
 
+@disjoint_base
 class SystemExit(BaseException):
     code: sys._ExitCode
 
 class Exception(BaseException): ...
 
+@disjoint_base
 class StopIteration(Exception):
     value: Any
 
+@disjoint_base
 class OSError(Exception):
     errno: int | None
     strerror: str | None
@@ -1950,15 +1990,20 @@ if sys.platform == "win32":
 class ArithmeticError(Exception): ...
 class AssertionError(Exception): ...
 
-class AttributeError(Exception):
-    if sys.version_info >= (3, 10):
+if sys.version_info >= (3, 10):
+    @disjoint_base
+    class AttributeError(Exception):
         def __init__(self, *args: object, name: str | None = ..., obj: object = ...) -> None: ...
         name: str
         obj: object
 
+else:
+    class AttributeError(Exception): ...
+
 class BufferError(Exception): ...
 class EOFError(Exception): ...
 
+@disjoint_base
 class ImportError(Exception):
     def __init__(self, *args: object, name: str | None = ..., path: str | None = ...) -> None: ...
     name: str | None
@@ -1970,15 +2015,20 @@ class ImportError(Exception):
 class LookupError(Exception): ...
 class MemoryError(Exception): ...
 
-class NameError(Exception):
-    if sys.version_info >= (3, 10):
+if sys.version_info >= (3, 10):
+    @disjoint_base
+    class NameError(Exception):
         def __init__(self, *args: object, name: str | None = ...) -> None: ...
         name: str
 
+else:
+    class NameError(Exception): ...
+
 class ReferenceError(Exception): ...
 class RuntimeError(Exception): ...
 class StopAsyncIteration(Exception): ...
 
+@disjoint_base
 class SyntaxError(Exception):
     msg: str
     filename: str | None
@@ -2042,6 +2092,7 @@ class IndentationError(SyntaxError): ...
 class TabError(IndentationError): ...
 class UnicodeError(ValueError): ...
 
+@disjoint_base
 class UnicodeDecodeError(UnicodeError):
     encoding: str
     object: bytes
@@ -2050,6 +2101,7 @@ class UnicodeDecodeError(UnicodeError):
     reason: str
     def __init__(self, encoding: str, object: ReadableBuffer, start: int, end: int, reason: str, /) -> None: ...
 
+@disjoint_base
 class UnicodeEncodeError(UnicodeError):
     encoding: str
     object: str
@@ -2058,6 +2110,7 @@ class UnicodeEncodeError(UnicodeError):
     reason: str
     def __init__(self, encoding: str, object: str, start: int, end: int, reason: str, /) -> None: ...
 
+@disjoint_base
 class UnicodeTranslateError(UnicodeError):
     encoding: None
     object: str
@@ -2088,6 +2141,7 @@ if sys.version_info >= (3, 11):
     _ExceptionT = TypeVar("_ExceptionT", bound=Exception)
 
     # See `check_exception_group.py` for use-cases and comments.
+    @disjoint_base
     class BaseExceptionGroup(BaseException, Generic[_BaseExceptionT_co]):
         def __new__(cls, message: str, exceptions: Sequence[_BaseExceptionT_co], /) -> Self: ...
         def __init__(self, message: str, exceptions: Sequence[_BaseExceptionT_co], /) -> None: ...
diff --git a/mypy/typeshed/stdlib/bz2.pyi b/mypy/typeshed/stdlib/bz2.pyi
index 0f9d00fbc633..7bd829d040cb 100644
--- a/mypy/typeshed/stdlib/bz2.pyi
+++ b/mypy/typeshed/stdlib/bz2.pyi
@@ -2,7 +2,8 @@ import sys
 from _bz2 import BZ2Compressor as BZ2Compressor, BZ2Decompressor as BZ2Decompressor
 from _typeshed import ReadableBuffer, StrOrBytesPath, WriteableBuffer
 from collections.abc import Iterable
-from typing import IO, Literal, Protocol, SupportsIndex, TextIO, overload
+from io import TextIOWrapper
+from typing import IO, Literal, Protocol, SupportsIndex, overload, type_check_only
 from typing_extensions import Self, TypeAlias
 
 if sys.version_info >= (3, 14):
@@ -15,8 +16,10 @@ __all__ = ["BZ2File", "BZ2Compressor", "BZ2Decompressor", "open", "compress", "d
 # The following attributes and methods are optional:
 # def fileno(self) -> int: ...
 # def close(self) -> object: ...
+@type_check_only
 class _ReadableFileobj(_Reader, Protocol): ...
 
+@type_check_only
 class _WritableFileobj(Protocol):
     def write(self, b: bytes, /) -> object: ...
     # The following attributes and methods are optional:
@@ -48,7 +51,7 @@ def open(
     encoding: str | None = None,
     errors: str | None = None,
     newline: str | None = None,
-) -> TextIO: ...
+) -> TextIOWrapper: ...
 @overload
 def open(
     filename: _WritableFileobj,
@@ -66,7 +69,7 @@ def open(
     encoding: str | None = None,
     errors: str | None = None,
     newline: str | None = None,
-) -> TextIO: ...
+) -> TextIOWrapper: ...
 @overload
 def open(
     filename: StrOrBytesPath,
@@ -84,7 +87,7 @@ def open(
     encoding: str | None = None,
     errors: str | None = None,
     newline: str | None = None,
-) -> TextIO: ...
+) -> TextIOWrapper: ...
 @overload
 def open(
     filename: StrOrBytesPath | _ReadableFileobj | _WritableFileobj,
@@ -93,7 +96,7 @@ def open(
     encoding: str | None = None,
     errors: str | None = None,
     newline: str | None = None,
-) -> BZ2File | TextIO: ...
+) -> BZ2File | TextIOWrapper: ...
 
 class BZ2File(BaseStream, IO[bytes]):
     def __enter__(self) -> Self: ...
diff --git a/mypy/typeshed/stdlib/calendar.pyi b/mypy/typeshed/stdlib/calendar.pyi
index cabf3b881c30..d00f0d5d2bce 100644
--- a/mypy/typeshed/stdlib/calendar.pyi
+++ b/mypy/typeshed/stdlib/calendar.pyi
@@ -167,18 +167,18 @@ if sys.version_info >= (3, 12):
         NOVEMBER = 11
         DECEMBER = 12
 
-    JANUARY = Month.JANUARY
-    FEBRUARY = Month.FEBRUARY
-    MARCH = Month.MARCH
-    APRIL = Month.APRIL
-    MAY = Month.MAY
-    JUNE = Month.JUNE
-    JULY = Month.JULY
-    AUGUST = Month.AUGUST
-    SEPTEMBER = Month.SEPTEMBER
-    OCTOBER = Month.OCTOBER
-    NOVEMBER = Month.NOVEMBER
-    DECEMBER = Month.DECEMBER
+    JANUARY: Final = Month.JANUARY
+    FEBRUARY: Final = Month.FEBRUARY
+    MARCH: Final = Month.MARCH
+    APRIL: Final = Month.APRIL
+    MAY: Final = Month.MAY
+    JUNE: Final = Month.JUNE
+    JULY: Final = Month.JULY
+    AUGUST: Final = Month.AUGUST
+    SEPTEMBER: Final = Month.SEPTEMBER
+    OCTOBER: Final = Month.OCTOBER
+    NOVEMBER: Final = Month.NOVEMBER
+    DECEMBER: Final = Month.DECEMBER
 
     class Day(enum.IntEnum):
         MONDAY = 0
@@ -189,13 +189,13 @@ if sys.version_info >= (3, 12):
         SATURDAY = 5
         SUNDAY = 6
 
-    MONDAY = Day.MONDAY
-    TUESDAY = Day.TUESDAY
-    WEDNESDAY = Day.WEDNESDAY
-    THURSDAY = Day.THURSDAY
-    FRIDAY = Day.FRIDAY
-    SATURDAY = Day.SATURDAY
-    SUNDAY = Day.SUNDAY
+    MONDAY: Final = Day.MONDAY
+    TUESDAY: Final = Day.TUESDAY
+    WEDNESDAY: Final = Day.WEDNESDAY
+    THURSDAY: Final = Day.THURSDAY
+    FRIDAY: Final = Day.FRIDAY
+    SATURDAY: Final = Day.SATURDAY
+    SUNDAY: Final = Day.SUNDAY
 else:
     MONDAY: Final = 0
     TUESDAY: Final = 1
diff --git a/mypy/typeshed/stdlib/cgi.pyi b/mypy/typeshed/stdlib/cgi.pyi
index 3a2e2a91b241..0f9d4343b630 100644
--- a/mypy/typeshed/stdlib/cgi.pyi
+++ b/mypy/typeshed/stdlib/cgi.pyi
@@ -1,9 +1,10 @@
+import os
 from _typeshed import SupportsContainsAndGetItem, SupportsGetItem, SupportsItemAccess, Unused
 from builtins import list as _list, type as _type
 from collections.abc import Iterable, Iterator, Mapping
 from email.message import Message
 from types import TracebackType
-from typing import IO, Any, Protocol
+from typing import IO, Any, Protocol, type_check_only
 from typing_extensions import Self
 
 __all__ = [
@@ -23,7 +24,7 @@ __all__ = [
 
 def parse(
     fp: IO[Any] | None = None,
-    environ: SupportsItemAccess[str, str] = ...,
+    environ: SupportsItemAccess[str, str] = os.environ,
     keep_blank_values: bool = ...,
     strict_parsing: bool = ...,
     separator: str = "&",
@@ -31,14 +32,14 @@ def parse(
 def parse_multipart(
     fp: IO[Any], pdict: SupportsGetItem[str, bytes], encoding: str = "utf-8", errors: str = "replace", separator: str = "&"
 ) -> dict[str, list[Any]]: ...
-
+@type_check_only
 class _Environ(Protocol):
     def __getitem__(self, k: str, /) -> str: ...
     def keys(self) -> Iterable[str]: ...
 
 def parse_header(line: str) -> tuple[str, dict[str, str]]: ...
-def test(environ: _Environ = ...) -> None: ...
-def print_environ(environ: _Environ = ...) -> None: ...
+def test(environ: _Environ = os.environ) -> None: ...
+def print_environ(environ: _Environ = os.environ) -> None: ...
 def print_form(form: dict[str, Any]) -> None: ...
 def print_directory() -> None: ...
 def print_environ_usage() -> None: ...
@@ -85,7 +86,7 @@ class FieldStorage:
         fp: IO[Any] | None = None,
         headers: Mapping[str, str] | Message | None = None,
         outerboundary: bytes = b"",
-        environ: SupportsContainsAndGetItem[str, str] = ...,
+        environ: SupportsContainsAndGetItem[str, str] = os.environ,
         keep_blank_values: int = 0,
         strict_parsing: int = 0,
         limit: int | None = None,
diff --git a/mypy/typeshed/stdlib/codecs.pyi b/mypy/typeshed/stdlib/codecs.pyi
index 579d09c66a1b..fa4d4fd4ba92 100644
--- a/mypy/typeshed/stdlib/codecs.pyi
+++ b/mypy/typeshed/stdlib/codecs.pyi
@@ -1,10 +1,11 @@
+import sys
 import types
 from _codecs import *
 from _typeshed import ReadableBuffer
 from abc import abstractmethod
 from collections.abc import Callable, Generator, Iterable
-from typing import Any, BinaryIO, ClassVar, Final, Literal, Protocol, TextIO, overload
-from typing_extensions import Self, TypeAlias
+from typing import Any, BinaryIO, ClassVar, Final, Literal, Protocol, TextIO, overload, type_check_only
+from typing_extensions import Self, TypeAlias, disjoint_base
 
 __all__ = [
     "register",
@@ -73,16 +74,19 @@ _BufferedEncoding: TypeAlias = Literal[
     "utf-8-sig",
 ]
 
+@type_check_only
 class _WritableStream(Protocol):
     def write(self, data: bytes, /) -> object: ...
     def seek(self, offset: int, whence: int, /) -> object: ...
     def close(self) -> object: ...
 
+@type_check_only
 class _ReadableStream(Protocol):
     def read(self, size: int = ..., /) -> bytes: ...
     def seek(self, offset: int, whence: int, /) -> object: ...
     def close(self) -> object: ...
 
+@type_check_only
 class _Stream(_WritableStream, _ReadableStream, Protocol): ...
 
 # TODO: this only satisfies the most common interface, where
@@ -91,54 +95,92 @@ class _Stream(_WritableStream, _ReadableStream, Protocol): ...
 # There *are* bytes->bytes and str->str encodings in the standard library.
 # They were much more common in Python 2 than in Python 3.
 
+@type_check_only
 class _Encoder(Protocol):
     def __call__(self, input: str, errors: str = ..., /) -> tuple[bytes, int]: ...  # signature of Codec().encode
 
+@type_check_only
 class _Decoder(Protocol):
     def __call__(self, input: ReadableBuffer, errors: str = ..., /) -> tuple[str, int]: ...  # signature of Codec().decode
 
+@type_check_only
 class _StreamReader(Protocol):
     def __call__(self, stream: _ReadableStream, errors: str = ..., /) -> StreamReader: ...
 
+@type_check_only
 class _StreamWriter(Protocol):
     def __call__(self, stream: _WritableStream, errors: str = ..., /) -> StreamWriter: ...
 
+@type_check_only
 class _IncrementalEncoder(Protocol):
     def __call__(self, errors: str = ...) -> IncrementalEncoder: ...
 
+@type_check_only
 class _IncrementalDecoder(Protocol):
     def __call__(self, errors: str = ...) -> IncrementalDecoder: ...
 
+@type_check_only
 class _BufferedIncrementalDecoder(Protocol):
     def __call__(self, errors: str = ...) -> BufferedIncrementalDecoder: ...
 
-class CodecInfo(tuple[_Encoder, _Decoder, _StreamReader, _StreamWriter]):
-    _is_text_encoding: bool
-    @property
-    def encode(self) -> _Encoder: ...
-    @property
-    def decode(self) -> _Decoder: ...
-    @property
-    def streamreader(self) -> _StreamReader: ...
-    @property
-    def streamwriter(self) -> _StreamWriter: ...
-    @property
-    def incrementalencoder(self) -> _IncrementalEncoder: ...
-    @property
-    def incrementaldecoder(self) -> _IncrementalDecoder: ...
-    name: str
-    def __new__(
-        cls,
-        encode: _Encoder,
-        decode: _Decoder,
-        streamreader: _StreamReader | None = None,
-        streamwriter: _StreamWriter | None = None,
-        incrementalencoder: _IncrementalEncoder | None = None,
-        incrementaldecoder: _IncrementalDecoder | None = None,
-        name: str | None = None,
-        *,
-        _is_text_encoding: bool | None = None,
-    ) -> Self: ...
+if sys.version_info >= (3, 12):
+    class CodecInfo(tuple[_Encoder, _Decoder, _StreamReader, _StreamWriter]):
+        _is_text_encoding: bool
+        @property
+        def encode(self) -> _Encoder: ...
+        @property
+        def decode(self) -> _Decoder: ...
+        @property
+        def streamreader(self) -> _StreamReader: ...
+        @property
+        def streamwriter(self) -> _StreamWriter: ...
+        @property
+        def incrementalencoder(self) -> _IncrementalEncoder: ...
+        @property
+        def incrementaldecoder(self) -> _IncrementalDecoder: ...
+        name: str
+        def __new__(
+            cls,
+            encode: _Encoder,
+            decode: _Decoder,
+            streamreader: _StreamReader | None = None,
+            streamwriter: _StreamWriter | None = None,
+            incrementalencoder: _IncrementalEncoder | None = None,
+            incrementaldecoder: _IncrementalDecoder | None = None,
+            name: str | None = None,
+            *,
+            _is_text_encoding: bool | None = None,
+        ) -> Self: ...
+
+else:
+    @disjoint_base
+    class CodecInfo(tuple[_Encoder, _Decoder, _StreamReader, _StreamWriter]):
+        _is_text_encoding: bool
+        @property
+        def encode(self) -> _Encoder: ...
+        @property
+        def decode(self) -> _Decoder: ...
+        @property
+        def streamreader(self) -> _StreamReader: ...
+        @property
+        def streamwriter(self) -> _StreamWriter: ...
+        @property
+        def incrementalencoder(self) -> _IncrementalEncoder: ...
+        @property
+        def incrementaldecoder(self) -> _IncrementalDecoder: ...
+        name: str
+        def __new__(
+            cls,
+            encode: _Encoder,
+            decode: _Decoder,
+            streamreader: _StreamReader | None = None,
+            streamwriter: _StreamWriter | None = None,
+            incrementalencoder: _IncrementalEncoder | None = None,
+            incrementaldecoder: _IncrementalDecoder | None = None,
+            name: str | None = None,
+            *,
+            _is_text_encoding: bool | None = None,
+        ) -> Self: ...
 
 def getencoder(encoding: str) -> _Encoder: ...
 def getdecoder(encoding: str) -> _Decoder: ...
diff --git a/mypy/typeshed/stdlib/collections/__init__.pyi b/mypy/typeshed/stdlib/collections/__init__.pyi
index b9e4f84ec0b6..8636e6cdbdc3 100644
--- a/mypy/typeshed/stdlib/collections/__init__.pyi
+++ b/mypy/typeshed/stdlib/collections/__init__.pyi
@@ -2,8 +2,8 @@ import sys
 from _collections_abc import dict_items, dict_keys, dict_values
 from _typeshed import SupportsItems, SupportsKeysAndGetItem, SupportsRichComparison, SupportsRichComparisonT
 from types import GenericAlias
-from typing import Any, ClassVar, Generic, NoReturn, SupportsIndex, TypeVar, final, overload
-from typing_extensions import Self
+from typing import Any, ClassVar, Generic, NoReturn, SupportsIndex, TypeVar, final, overload, type_check_only
+from typing_extensions import Self, disjoint_base
 
 if sys.version_info >= (3, 10):
     from collections.abc import (
@@ -108,6 +108,8 @@ class UserDict(MutableMapping[_KT, _VT]):
         @overload
         def get(self, key: _KT, default: None = None) -> _VT | None: ...
         @overload
+        def get(self, key: _KT, default: _VT) -> _VT: ...
+        @overload
         def get(self, key: _KT, default: _T) -> _VT | _T: ...
 
 class UserList(MutableSequence[_T]):
@@ -229,6 +231,7 @@ class UserString(Sequence[UserString]):
     def upper(self) -> Self: ...
     def zfill(self, width: int) -> Self: ...
 
+@disjoint_base
 class deque(MutableSequence[_T]):
     @property
     def maxlen(self) -> int | None: ...
@@ -340,17 +343,21 @@ class _OrderedDictValuesView(ValuesView[_VT_co]):
 # but they are not exposed anywhere)
 # pyright doesn't have a specific error code for subclassing error!
 @final
+@type_check_only
 class _odict_keys(dict_keys[_KT_co, _VT_co]):  # type: ignore[misc]  # pyright: ignore[reportGeneralTypeIssues]
     def __reversed__(self) -> Iterator[_KT_co]: ...
 
 @final
+@type_check_only
 class _odict_items(dict_items[_KT_co, _VT_co]):  # type: ignore[misc]  # pyright: ignore[reportGeneralTypeIssues]
     def __reversed__(self) -> Iterator[tuple[_KT_co, _VT_co]]: ...
 
 @final
+@type_check_only
 class _odict_values(dict_values[_KT_co, _VT_co]):  # type: ignore[misc]  # pyright: ignore[reportGeneralTypeIssues]
     def __reversed__(self) -> Iterator[_VT_co]: ...
 
+@disjoint_base
 class OrderedDict(dict[_KT, _VT]):
     def popitem(self, last: bool = True) -> tuple[_KT, _VT]: ...
     def move_to_end(self, key: _KT, last: bool = True) -> None: ...
@@ -390,6 +397,7 @@ class OrderedDict(dict[_KT, _VT]):
     @overload
     def __ror__(self, value: dict[_T1, _T2], /) -> OrderedDict[_KT | _T1, _VT | _T2]: ...  # type: ignore[misc]
 
+@disjoint_base
 class defaultdict(dict[_KT, _VT]):
     default_factory: Callable[[], _VT] | None
     @overload
@@ -452,6 +460,8 @@ class ChainMap(MutableMapping[_KT, _VT]):
     @overload
     def get(self, key: _KT, default: None = None) -> _VT | None: ...
     @overload
+    def get(self, key: _KT, default: _VT) -> _VT: ...
+    @overload
     def get(self, key: _KT, default: _T) -> _VT | _T: ...
     def __missing__(self, key: _KT) -> _VT: ...  # undocumented
     def __bool__(self) -> bool: ...
@@ -470,9 +480,15 @@ class ChainMap(MutableMapping[_KT, _VT]):
     __copy__ = copy
     # All arguments to `fromkeys` are passed to `dict.fromkeys` at runtime,
     # so the signature should be kept in line with `dict.fromkeys`.
-    @classmethod
-    @overload
-    def fromkeys(cls, iterable: Iterable[_T]) -> ChainMap[_T, Any | None]: ...
+    if sys.version_info >= (3, 13):
+        @classmethod
+        @overload
+        def fromkeys(cls, iterable: Iterable[_T], /) -> ChainMap[_T, Any | None]: ...
+    else:
+        @classmethod
+        @overload
+        def fromkeys(cls, iterable: Iterable[_T]) -> ChainMap[_T, Any | None]: ...
+
     @classmethod
     @overload
     # Special-case None: the user probably wants to add non-None values later.
diff --git a/mypy/typeshed/stdlib/colorsys.pyi b/mypy/typeshed/stdlib/colorsys.pyi
index 7842f80284ef..4afcb5392b58 100644
--- a/mypy/typeshed/stdlib/colorsys.pyi
+++ b/mypy/typeshed/stdlib/colorsys.pyi
@@ -1,3 +1,5 @@
+from typing import Final
+
 __all__ = ["rgb_to_yiq", "yiq_to_rgb", "rgb_to_hls", "hls_to_rgb", "rgb_to_hsv", "hsv_to_rgb"]
 
 def rgb_to_yiq(r: float, g: float, b: float) -> tuple[float, float, float]: ...
@@ -8,6 +10,6 @@ def rgb_to_hsv(r: float, g: float, b: float) -> tuple[float, float, float]: ...
 def hsv_to_rgb(h: float, s: float, v: float) -> tuple[float, float, float]: ...
 
 # TODO: undocumented
-ONE_SIXTH: float
-ONE_THIRD: float
-TWO_THIRD: float
+ONE_SIXTH: Final[float]
+ONE_THIRD: Final[float]
+TWO_THIRD: Final[float]
diff --git a/mypy/typeshed/stdlib/compileall.pyi b/mypy/typeshed/stdlib/compileall.pyi
index a599b1b23540..8972d50a4a63 100644
--- a/mypy/typeshed/stdlib/compileall.pyi
+++ b/mypy/typeshed/stdlib/compileall.pyi
@@ -1,10 +1,11 @@
 import sys
 from _typeshed import StrPath
 from py_compile import PycInvalidationMode
-from typing import Any, Protocol
+from typing import Any, Protocol, type_check_only
 
 __all__ = ["compile_dir", "compile_file", "compile_path"]
 
+@type_check_only
 class _SupportsSearch(Protocol):
     def search(self, string: str, /) -> Any: ...
 
diff --git a/mypy/typeshed/stdlib/compression/_common/_streams.pyi b/mypy/typeshed/stdlib/compression/_common/_streams.pyi
index 6303a9b1d460..b8463973ec67 100644
--- a/mypy/typeshed/stdlib/compression/_common/_streams.pyi
+++ b/mypy/typeshed/stdlib/compression/_common/_streams.pyi
@@ -1,10 +1,11 @@
 from _typeshed import Incomplete, WriteableBuffer
 from collections.abc import Callable
 from io import DEFAULT_BUFFER_SIZE, BufferedIOBase, RawIOBase
-from typing import Any, Protocol
+from typing import Any, Protocol, type_check_only
 
 BUFFER_SIZE = DEFAULT_BUFFER_SIZE
 
+@type_check_only
 class _Reader(Protocol):
     def read(self, n: int, /) -> bytes: ...
     def seekable(self) -> bool: ...
diff --git a/mypy/typeshed/stdlib/compression/bz2/__init__.pyi b/mypy/typeshed/stdlib/compression/bz2.pyi
similarity index 100%
rename from mypy/typeshed/stdlib/compression/bz2/__init__.pyi
rename to mypy/typeshed/stdlib/compression/bz2.pyi
diff --git a/mypy/typeshed/stdlib/compression/gzip/__init__.pyi b/mypy/typeshed/stdlib/compression/gzip.pyi
similarity index 100%
rename from mypy/typeshed/stdlib/compression/gzip/__init__.pyi
rename to mypy/typeshed/stdlib/compression/gzip.pyi
diff --git a/mypy/typeshed/stdlib/compression/lzma/__init__.pyi b/mypy/typeshed/stdlib/compression/lzma.pyi
similarity index 100%
rename from mypy/typeshed/stdlib/compression/lzma/__init__.pyi
rename to mypy/typeshed/stdlib/compression/lzma.pyi
diff --git a/mypy/typeshed/stdlib/compression/zlib/__init__.pyi b/mypy/typeshed/stdlib/compression/zlib.pyi
similarity index 100%
rename from mypy/typeshed/stdlib/compression/zlib/__init__.pyi
rename to mypy/typeshed/stdlib/compression/zlib.pyi
diff --git a/mypy/typeshed/stdlib/compression/zstd/__init__.pyi b/mypy/typeshed/stdlib/compression/zstd/__init__.pyi
new file mode 100644
index 000000000000..d5da4be03612
--- /dev/null
+++ b/mypy/typeshed/stdlib/compression/zstd/__init__.pyi
@@ -0,0 +1,88 @@
+import enum
+from _typeshed import ReadableBuffer
+from collections.abc import Iterable, Mapping
+from compression.zstd._zstdfile import ZstdFile, open
+from typing import Final, final
+
+import _zstd
+from _zstd import ZstdCompressor, ZstdDecompressor, ZstdDict, ZstdError, get_frame_size, zstd_version
+
+__all__ = (
+    # compression.zstd
+    "COMPRESSION_LEVEL_DEFAULT",
+    "compress",
+    "CompressionParameter",
+    "decompress",
+    "DecompressionParameter",
+    "finalize_dict",
+    "get_frame_info",
+    "Strategy",
+    "train_dict",
+    # compression.zstd._zstdfile
+    "open",
+    "ZstdFile",
+    # _zstd
+    "get_frame_size",
+    "zstd_version",
+    "zstd_version_info",
+    "ZstdCompressor",
+    "ZstdDecompressor",
+    "ZstdDict",
+    "ZstdError",
+)
+
+zstd_version_info: Final[tuple[int, int, int]]
+COMPRESSION_LEVEL_DEFAULT: Final = _zstd.ZSTD_CLEVEL_DEFAULT
+
+class FrameInfo:
+    __slots__ = ("decompressed_size", "dictionary_id")
+    decompressed_size: int
+    dictionary_id: int
+    def __init__(self, decompressed_size: int, dictionary_id: int) -> None: ...
+
+def get_frame_info(frame_buffer: ReadableBuffer) -> FrameInfo: ...
+def train_dict(samples: Iterable[ReadableBuffer], dict_size: int) -> ZstdDict: ...
+def finalize_dict(zstd_dict: ZstdDict, /, samples: Iterable[ReadableBuffer], dict_size: int, level: int) -> ZstdDict: ...
+def compress(
+    data: ReadableBuffer, level: int | None = None, options: Mapping[int, int] | None = None, zstd_dict: ZstdDict | None = None
+) -> bytes: ...
+def decompress(data: ReadableBuffer, zstd_dict: ZstdDict | None = None, options: Mapping[int, int] | None = None) -> bytes: ...
+@final
+class CompressionParameter(enum.IntEnum):
+    compression_level = _zstd.ZSTD_c_compressionLevel
+    window_log = _zstd.ZSTD_c_windowLog
+    hash_log = _zstd.ZSTD_c_hashLog
+    chain_log = _zstd.ZSTD_c_chainLog
+    search_log = _zstd.ZSTD_c_searchLog
+    min_match = _zstd.ZSTD_c_minMatch
+    target_length = _zstd.ZSTD_c_targetLength
+    strategy = _zstd.ZSTD_c_strategy
+    enable_long_distance_matching = _zstd.ZSTD_c_enableLongDistanceMatching
+    ldm_hash_log = _zstd.ZSTD_c_ldmHashLog
+    ldm_min_match = _zstd.ZSTD_c_ldmMinMatch
+    ldm_bucket_size_log = _zstd.ZSTD_c_ldmBucketSizeLog
+    ldm_hash_rate_log = _zstd.ZSTD_c_ldmHashRateLog
+    content_size_flag = _zstd.ZSTD_c_contentSizeFlag
+    checksum_flag = _zstd.ZSTD_c_checksumFlag
+    dict_id_flag = _zstd.ZSTD_c_dictIDFlag
+    nb_workers = _zstd.ZSTD_c_nbWorkers
+    job_size = _zstd.ZSTD_c_jobSize
+    overlap_log = _zstd.ZSTD_c_overlapLog
+    def bounds(self) -> tuple[int, int]: ...
+
+@final
+class DecompressionParameter(enum.IntEnum):
+    window_log_max = _zstd.ZSTD_d_windowLogMax
+    def bounds(self) -> tuple[int, int]: ...
+
+@final
+class Strategy(enum.IntEnum):
+    fast = _zstd.ZSTD_fast
+    dfast = _zstd.ZSTD_dfast
+    greedy = _zstd.ZSTD_greedy
+    lazy = _zstd.ZSTD_lazy
+    lazy2 = _zstd.ZSTD_lazy2
+    btlazy2 = _zstd.ZSTD_btlazy2
+    btopt = _zstd.ZSTD_btopt
+    btultra = _zstd.ZSTD_btultra
+    btultra2 = _zstd.ZSTD_btultra2
diff --git a/mypy/typeshed/stdlib/compression/zstd/_zstdfile.pyi b/mypy/typeshed/stdlib/compression/zstd/_zstdfile.pyi
new file mode 100644
index 000000000000..e67b3d992f2f
--- /dev/null
+++ b/mypy/typeshed/stdlib/compression/zstd/_zstdfile.pyi
@@ -0,0 +1,117 @@
+from _typeshed import ReadableBuffer, StrOrBytesPath, SupportsWrite, WriteableBuffer
+from collections.abc import Mapping
+from compression._common import _streams
+from compression.zstd import ZstdDict
+from io import TextIOWrapper, _WrappedBuffer
+from typing import Literal, Protocol, overload, type_check_only
+from typing_extensions import TypeAlias
+
+from _zstd import ZstdCompressor, _ZstdCompressorFlushBlock, _ZstdCompressorFlushFrame
+
+__all__ = ("ZstdFile", "open")
+
+_ReadBinaryMode: TypeAlias = Literal["r", "rb"]
+_WriteBinaryMode: TypeAlias = Literal["w", "wb", "x", "xb", "a", "ab"]
+_ReadTextMode: TypeAlias = Literal["rt"]
+_WriteTextMode: TypeAlias = Literal["wt", "xt", "at"]
+
+@type_check_only
+class _FileBinaryRead(_streams._Reader, Protocol):
+    def close(self) -> None: ...
+
+@type_check_only
+class _FileBinaryWrite(SupportsWrite[bytes], Protocol):
+    def close(self) -> None: ...
+
+class ZstdFile(_streams.BaseStream):
+    FLUSH_BLOCK = ZstdCompressor.FLUSH_BLOCK
+    FLUSH_FRAME = ZstdCompressor.FLUSH_FRAME
+
+    @overload
+    def __init__(
+        self,
+        file: StrOrBytesPath | _FileBinaryRead,
+        /,
+        mode: _ReadBinaryMode = "r",
+        *,
+        level: None = None,
+        options: Mapping[int, int] | None = None,
+        zstd_dict: ZstdDict | None = None,
+    ) -> None: ...
+    @overload
+    def __init__(
+        self,
+        file: StrOrBytesPath | _FileBinaryWrite,
+        /,
+        mode: _WriteBinaryMode,
+        *,
+        level: int | None = None,
+        options: Mapping[int, int] | None = None,
+        zstd_dict: ZstdDict | None = None,
+    ) -> None: ...
+    def write(self, data: ReadableBuffer, /) -> int: ...
+    def flush(self, mode: _ZstdCompressorFlushBlock | _ZstdCompressorFlushFrame = 1) -> bytes: ...  # type: ignore[override]
+    def read(self, size: int | None = -1) -> bytes: ...
+    def read1(self, size: int | None = -1) -> bytes: ...
+    def readinto(self, b: WriteableBuffer) -> int: ...
+    def readinto1(self, b: WriteableBuffer) -> int: ...
+    def readline(self, size: int | None = -1) -> bytes: ...
+    def seek(self, offset: int, whence: int = 0) -> int: ...
+    def peek(self, size: int = -1) -> bytes: ...
+    @property
+    def name(self) -> str | bytes: ...
+    @property
+    def mode(self) -> Literal["rb", "wb"]: ...
+
+@overload
+def open(
+    file: StrOrBytesPath | _FileBinaryRead,
+    /,
+    mode: _ReadBinaryMode = "rb",
+    *,
+    level: None = None,
+    options: Mapping[int, int] | None = None,
+    zstd_dict: ZstdDict | None = None,
+    encoding: str | None = None,
+    errors: str | None = None,
+    newline: str | None = None,
+) -> ZstdFile: ...
+@overload
+def open(
+    file: StrOrBytesPath | _FileBinaryWrite,
+    /,
+    mode: _WriteBinaryMode,
+    *,
+    level: int | None = None,
+    options: Mapping[int, int] | None = None,
+    zstd_dict: ZstdDict | None = None,
+    encoding: str | None = None,
+    errors: str | None = None,
+    newline: str | None = None,
+) -> ZstdFile: ...
+@overload
+def open(
+    file: StrOrBytesPath | _WrappedBuffer,
+    /,
+    mode: _ReadTextMode,
+    *,
+    level: None = None,
+    options: Mapping[int, int] | None = None,
+    zstd_dict: ZstdDict | None = None,
+    encoding: str | None = None,
+    errors: str | None = None,
+    newline: str | None = None,
+) -> TextIOWrapper: ...
+@overload
+def open(
+    file: StrOrBytesPath | _WrappedBuffer,
+    /,
+    mode: _WriteTextMode,
+    *,
+    level: int | None = None,
+    options: Mapping[int, int] | None = None,
+    zstd_dict: ZstdDict | None = None,
+    encoding: str | None = None,
+    errors: str | None = None,
+    newline: str | None = None,
+) -> TextIOWrapper: ...
diff --git a/mypy/typeshed/stdlib/concurrent/futures/__init__.pyi b/mypy/typeshed/stdlib/concurrent/futures/__init__.pyi
index dd1f6da80c4d..ad4d20ea5445 100644
--- a/mypy/typeshed/stdlib/concurrent/futures/__init__.pyi
+++ b/mypy/typeshed/stdlib/concurrent/futures/__init__.pyi
@@ -19,7 +19,7 @@ from .thread import ThreadPoolExecutor as ThreadPoolExecutor
 if sys.version_info >= (3, 14):
     from .interpreter import InterpreterPoolExecutor as InterpreterPoolExecutor
 
-    __all__ = (
+    __all__ = [
         "FIRST_COMPLETED",
         "FIRST_EXCEPTION",
         "ALL_COMPLETED",
@@ -34,7 +34,7 @@ if sys.version_info >= (3, 14):
         "ProcessPoolExecutor",
         "ThreadPoolExecutor",
         "InterpreterPoolExecutor",
-    )
+    ]
 
 elif sys.version_info >= (3, 13):
     __all__ = (
diff --git a/mypy/typeshed/stdlib/concurrent/futures/_base.pyi b/mypy/typeshed/stdlib/concurrent/futures/_base.pyi
index fbf07a3fc78f..be48a6e4289c 100644
--- a/mypy/typeshed/stdlib/concurrent/futures/_base.pyi
+++ b/mypy/typeshed/stdlib/concurrent/futures/_base.pyi
@@ -4,7 +4,7 @@ from _typeshed import Unused
 from collections.abc import Callable, Iterable, Iterator
 from logging import Logger
 from types import GenericAlias, TracebackType
-from typing import Any, Final, Generic, NamedTuple, Protocol, TypeVar
+from typing import Any, Final, Generic, NamedTuple, Protocol, TypeVar, type_check_only
 from typing_extensions import ParamSpec, Self
 
 FIRST_COMPLETED: Final = "FIRST_COMPLETED"
@@ -15,8 +15,7 @@ RUNNING: Final = "RUNNING"
 CANCELLED: Final = "CANCELLED"
 CANCELLED_AND_NOTIFIED: Final = "CANCELLED_AND_NOTIFIED"
 FINISHED: Final = "FINISHED"
-_FUTURE_STATES: list[str]
-_STATE_TO_DESCRIPTION_MAP: dict[str, str]
+_STATE_TO_DESCRIPTION_MAP: Final[dict[str, str]]
 LOGGER: Logger
 
 class Error(Exception): ...
@@ -74,6 +73,7 @@ class Executor:
         self, exc_type: type[BaseException] | None, exc_val: BaseException | None, exc_tb: TracebackType | None
     ) -> bool | None: ...
 
+@type_check_only
 class _AsCompletedFuture(Protocol[_T_co]):
     # as_completed only mutates non-generic aspects of passed Futures and does not do any nominal
     # checks. Therefore, we can use a Protocol here to allow as_completed to act covariantly.
diff --git a/mypy/typeshed/stdlib/concurrent/futures/interpreter.pyi b/mypy/typeshed/stdlib/concurrent/futures/interpreter.pyi
index 9c1078983d8c..e101022babcb 100644
--- a/mypy/typeshed/stdlib/concurrent/futures/interpreter.pyi
+++ b/mypy/typeshed/stdlib/concurrent/futures/interpreter.pyi
@@ -1,10 +1,13 @@
 import sys
-from collections.abc import Callable, Mapping
+from collections.abc import Callable
 from concurrent.futures import ThreadPoolExecutor
-from typing import Literal, Protocol, overload, type_check_only
+from typing import Any, Literal, Protocol, overload, type_check_only
 from typing_extensions import ParamSpec, Self, TypeAlias, TypeVar, TypeVarTuple, Unpack
 
 _Task: TypeAlias = tuple[bytes, Literal["function", "script"]]
+_Ts = TypeVarTuple("_Ts")
+_P = ParamSpec("_P")
+_R = TypeVar("_R")
 
 @type_check_only
 class _TaskFunc(Protocol):
@@ -13,62 +16,41 @@ class _TaskFunc(Protocol):
     @overload
     def __call__(self, fn: str) -> tuple[bytes, Literal["script"]]: ...
 
-_Ts = TypeVarTuple("_Ts")
-_P = ParamSpec("_P")
-_R = TypeVar("_R")
-
-# A `type.simplenamespace` with `__name__` attribute.
-@type_check_only
-class _HasName(Protocol):
-    __name__: str
-
-# `_interpreters.exec` technically gives us a simple namespace.
-@type_check_only
-class _ExcInfo(Protocol):
-    formatted: str
-    msg: str
-    type: _HasName
-
 if sys.version_info >= (3, 14):
     from concurrent.futures.thread import BrokenThreadPool, WorkerContext as ThreadWorkerContext
+    from concurrent.interpreters import Interpreter, Queue
 
-    from _interpreters import InterpreterError
-
-    class ExecutionFailed(InterpreterError):
-        def __init__(self, excinfo: _ExcInfo) -> None: ...  #  type: ignore[override]
+    def do_call(results: Queue, func: Callable[..., _R], args: tuple[Any, ...], kwargs: dict[str, Any]) -> _R: ...
 
     class WorkerContext(ThreadWorkerContext):
-        # Parent class doesn't have `shared` argument,
-        @overload  #  type: ignore[override]
+        interp: Interpreter | None
+        results: Queue | None
+        @overload  # type: ignore[override]
         @classmethod
         def prepare(
-            cls, initializer: Callable[[Unpack[_Ts]], object], initargs: tuple[Unpack[_Ts]], shared: Mapping[str, object]
+            cls, initializer: Callable[[Unpack[_Ts]], object], initargs: tuple[Unpack[_Ts]]
         ) -> tuple[Callable[[], Self], _TaskFunc]: ...
-        @overload  #  type: ignore[override]
+        @overload
         @classmethod
-        def prepare(
-            cls, initializer: Callable[[], object], initargs: tuple[()], shared: Mapping[str, object]
-        ) -> tuple[Callable[[], Self], _TaskFunc]: ...
-        def __init__(
-            self, initdata: tuple[bytes, Literal["function", "script"]], shared: Mapping[str, object] | None = None
-        ) -> None: ...  #  type: ignore[override]
+        def prepare(cls, initializer: Callable[[], object], initargs: tuple[()]) -> tuple[Callable[[], Self], _TaskFunc]: ...
+        def __init__(self, initdata: _Task) -> None: ...
         def __del__(self) -> None: ...
-        def run(self, task: _Task) -> None: ...  #  type: ignore[override]
+        def run(self, task: _Task) -> None: ...  # type: ignore[override]
 
     class BrokenInterpreterPool(BrokenThreadPool): ...
 
     class InterpreterPoolExecutor(ThreadPoolExecutor):
         BROKEN: type[BrokenInterpreterPool]
 
-        @overload  #  type: ignore[override]
+        @overload  # type: ignore[override]
         @classmethod
         def prepare_context(
-            cls, initializer: Callable[[], object], initargs: tuple[()], shared: Mapping[str, object]
+            cls, initializer: Callable[[], object], initargs: tuple[()]
         ) -> tuple[Callable[[], WorkerContext], _TaskFunc]: ...
-        @overload  #  type: ignore[override]
+        @overload
         @classmethod
         def prepare_context(
-            cls, initializer: Callable[[Unpack[_Ts]], object], initargs: tuple[Unpack[_Ts]], shared: Mapping[str, object]
+            cls, initializer: Callable[[Unpack[_Ts]], object], initargs: tuple[Unpack[_Ts]]
         ) -> tuple[Callable[[], WorkerContext], _TaskFunc]: ...
         @overload
         def __init__(
@@ -77,7 +59,6 @@ if sys.version_info >= (3, 14):
             thread_name_prefix: str = "",
             initializer: Callable[[], object] | None = None,
             initargs: tuple[()] = (),
-            shared: Mapping[str, object] | None = None,
         ) -> None: ...
         @overload
         def __init__(
@@ -87,7 +68,6 @@ if sys.version_info >= (3, 14):
             *,
             initializer: Callable[[Unpack[_Ts]], object],
             initargs: tuple[Unpack[_Ts]],
-            shared: Mapping[str, object] | None = None,
         ) -> None: ...
         @overload
         def __init__(
@@ -96,5 +76,4 @@ if sys.version_info >= (3, 14):
             thread_name_prefix: str,
             initializer: Callable[[Unpack[_Ts]], object],
             initargs: tuple[Unpack[_Ts]],
-            shared: Mapping[str, object] | None = None,
         ) -> None: ...
diff --git a/mypy/typeshed/stdlib/concurrent/futures/process.pyi b/mypy/typeshed/stdlib/concurrent/futures/process.pyi
index 607990100369..071b3aba5d33 100644
--- a/mypy/typeshed/stdlib/concurrent/futures/process.pyi
+++ b/mypy/typeshed/stdlib/concurrent/futures/process.pyi
@@ -5,7 +5,7 @@ from multiprocessing.context import BaseContext, Process
 from multiprocessing.queues import Queue, SimpleQueue
 from threading import Lock, Semaphore, Thread
 from types import TracebackType
-from typing import Any, Generic, TypeVar, overload
+from typing import Any, Final, Generic, TypeVar, overload
 from typing_extensions import TypeVarTuple, Unpack
 from weakref import ref
 
@@ -28,9 +28,9 @@ class _ThreadWakeup:
 
 def _python_exit() -> None: ...
 
-EXTRA_QUEUED_CALLS: int
+EXTRA_QUEUED_CALLS: Final = 1
 
-_MAX_WINDOWS_WORKERS: int
+_MAX_WINDOWS_WORKERS: Final = 61
 
 class _RemoteTraceback(Exception):
     tb: str
diff --git a/mypy/typeshed/stdlib/concurrent/futures/thread.pyi b/mypy/typeshed/stdlib/concurrent/futures/thread.pyi
index 22df0dca5a3f..50a6a9c6f43e 100644
--- a/mypy/typeshed/stdlib/concurrent/futures/thread.pyi
+++ b/mypy/typeshed/stdlib/concurrent/futures/thread.pyi
@@ -91,8 +91,12 @@ class ThreadPoolExecutor(Executor):
     _shutdown: bool
     _shutdown_lock: Lock
     _thread_name_prefix: str | None
-    _initializer: Callable[..., None] | None
-    _initargs: tuple[Any, ...]
+    if sys.version_info >= (3, 14):
+        _create_worker_context: Callable[[], WorkerContext]
+        _resolve_work_item_task: _ResolveTaskFunc
+    else:
+        _initializer: Callable[..., None] | None
+        _initargs: tuple[Any, ...]
     _work_queue: queue.SimpleQueue[_WorkItem[Any]]
 
     if sys.version_info >= (3, 14):
@@ -100,12 +104,12 @@ class ThreadPoolExecutor(Executor):
         @classmethod
         def prepare_context(
             cls, initializer: Callable[[], object], initargs: tuple[()]
-        ) -> tuple[Callable[[], Self], _ResolveTaskFunc]: ...
+        ) -> tuple[Callable[[], WorkerContext], _ResolveTaskFunc]: ...
         @overload
         @classmethod
         def prepare_context(
             cls, initializer: Callable[[Unpack[_Ts]], object], initargs: tuple[Unpack[_Ts]]
-        ) -> tuple[Callable[[], Self], _ResolveTaskFunc]: ...
+        ) -> tuple[Callable[[], WorkerContext], _ResolveTaskFunc]: ...
 
     @overload
     def __init__(
diff --git a/mypy/typeshed/stdlib/concurrent/interpreters/__init__.pyi b/mypy/typeshed/stdlib/concurrent/interpreters/__init__.pyi
new file mode 100644
index 000000000000..3839e6bef09b
--- /dev/null
+++ b/mypy/typeshed/stdlib/concurrent/interpreters/__init__.pyi
@@ -0,0 +1,68 @@
+import sys
+import threading
+import types
+from collections.abc import Callable
+from typing import Any, Literal, TypeVar
+from typing_extensions import ParamSpec, Self
+
+if sys.version_info >= (3, 13):  # needed to satisfy pyright checks for Python <3.13
+    from _interpreters import (
+        InterpreterError as InterpreterError,
+        InterpreterNotFoundError as InterpreterNotFoundError,
+        NotShareableError as NotShareableError,
+        _SharedDict,
+        _Whence,
+        is_shareable as is_shareable,
+    )
+
+    from ._queues import Queue as Queue, QueueEmpty as QueueEmpty, QueueFull as QueueFull, create as create_queue
+
+    __all__ = [
+        "ExecutionFailed",
+        "Interpreter",
+        "InterpreterError",
+        "InterpreterNotFoundError",
+        "NotShareableError",
+        "Queue",
+        "QueueEmpty",
+        "QueueFull",
+        "create",
+        "create_queue",
+        "get_current",
+        "get_main",
+        "is_shareable",
+        "list_all",
+    ]
+
+    _R = TypeVar("_R")
+    _P = ParamSpec("_P")
+
+    class ExecutionFailed(InterpreterError):
+        excinfo: types.SimpleNamespace
+
+        def __init__(self, excinfo: types.SimpleNamespace) -> None: ...
+
+    def create() -> Interpreter: ...
+    def list_all() -> list[Interpreter]: ...
+    def get_current() -> Interpreter: ...
+    def get_main() -> Interpreter: ...
+
+    class Interpreter:
+        def __new__(cls, id: int, /, _whence: _Whence | None = None, _ownsref: bool | None = None) -> Self: ...
+        def __reduce__(self) -> tuple[type[Self], int]: ...
+        def __hash__(self) -> int: ...
+        def __del__(self) -> None: ...
+        @property
+        def id(self) -> int: ...
+        @property
+        def whence(
+            self,
+        ) -> Literal["unknown", "runtime init", "legacy C-API", "C-API", "cross-interpreter C-API", "_interpreters module"]: ...
+        def is_running(self) -> bool: ...
+        def close(self) -> None: ...
+        def prepare_main(
+            self, ns: _SharedDict | None = None, /, **kwargs: Any
+        ) -> None: ...  # kwargs has same value restrictions as _SharedDict
+        def exec(self, code: str | types.CodeType | Callable[[], object], /) -> None: ...
+        def call(self, callable: Callable[_P, _R], /, *args: _P.args, **kwargs: _P.kwargs) -> _R: ...
+        def call_in_thread(self, callable: Callable[_P, object], /, *args: _P.args, **kwargs: _P.kwargs) -> threading.Thread: ...
diff --git a/mypy/typeshed/stdlib/concurrent/interpreters/_crossinterp.pyi b/mypy/typeshed/stdlib/concurrent/interpreters/_crossinterp.pyi
new file mode 100644
index 000000000000..7cf1ea34786e
--- /dev/null
+++ b/mypy/typeshed/stdlib/concurrent/interpreters/_crossinterp.pyi
@@ -0,0 +1,30 @@
+import sys
+from collections.abc import Callable
+from typing import Final, NewType
+from typing_extensions import Never, Self, TypeAlias
+
+if sys.version_info >= (3, 13):  # needed to satisfy pyright checks for Python <3.13
+    from _interpqueues import _UnboundOp
+
+    class ItemInterpreterDestroyed(Exception): ...
+    # Actually a descriptor that behaves similarly to classmethod but prevents
+    # access from instances.
+    classonly = classmethod
+
+    class UnboundItem:
+        __slots__ = ()
+        def __new__(cls) -> Never: ...
+        @classonly
+        def singleton(cls, kind: str, module: str, name: str = "UNBOUND") -> Self: ...
+
+    # Sentinel types and alias that don't exist at runtime.
+    _UnboundErrorType = NewType("_UnboundErrorType", object)
+    _UnboundRemoveType = NewType("_UnboundRemoveType", object)
+    _AnyUnbound: TypeAlias = _UnboundErrorType | _UnboundRemoveType | UnboundItem
+
+    UNBOUND_ERROR: Final[_UnboundErrorType]
+    UNBOUND_REMOVE: Final[_UnboundRemoveType]
+    UNBOUND: Final[UnboundItem]  # analogous to UNBOUND_REPLACE in C
+
+    def serialize_unbound(unbound: _AnyUnbound) -> tuple[_UnboundOp]: ...
+    def resolve_unbound(flag: _UnboundOp, exctype_destroyed: Callable[[str], BaseException]) -> UnboundItem: ...
diff --git a/mypy/typeshed/stdlib/concurrent/interpreters/_queues.pyi b/mypy/typeshed/stdlib/concurrent/interpreters/_queues.pyi
new file mode 100644
index 000000000000..7493f87809c8
--- /dev/null
+++ b/mypy/typeshed/stdlib/concurrent/interpreters/_queues.pyi
@@ -0,0 +1,58 @@
+import queue
+import sys
+from typing import Final, SupportsIndex
+from typing_extensions import Self
+
+if sys.version_info >= (3, 13):  # needed to satisfy pyright checks for Python <3.13
+    from _interpqueues import QueueError as QueueError, QueueNotFoundError as QueueNotFoundError
+
+    from . import _crossinterp
+    from ._crossinterp import UNBOUND_ERROR as UNBOUND_ERROR, UNBOUND_REMOVE as UNBOUND_REMOVE, UnboundItem, _AnyUnbound
+
+    __all__ = [
+        "UNBOUND",
+        "UNBOUND_ERROR",
+        "UNBOUND_REMOVE",
+        "ItemInterpreterDestroyed",
+        "Queue",
+        "QueueEmpty",
+        "QueueError",
+        "QueueFull",
+        "QueueNotFoundError",
+        "create",
+        "list_all",
+    ]
+
+    class QueueEmpty(QueueError, queue.Empty): ...
+    class QueueFull(QueueError, queue.Full): ...
+    class ItemInterpreterDestroyed(QueueError, _crossinterp.ItemInterpreterDestroyed): ...
+    UNBOUND: Final[UnboundItem]
+
+    def create(maxsize: int = 0, *, unbounditems: _AnyUnbound = ...) -> Queue: ...
+    def list_all() -> list[Queue]: ...
+
+    class Queue:
+        def __new__(cls, id: int, /) -> Self: ...
+        def __del__(self) -> None: ...
+        def __hash__(self) -> int: ...
+        def __reduce__(self) -> tuple[type[Self], int]: ...
+        @property
+        def id(self) -> int: ...
+        @property
+        def unbounditems(self) -> _AnyUnbound: ...
+        @property
+        def maxsize(self) -> int: ...
+        def empty(self) -> bool: ...
+        def full(self) -> bool: ...
+        def qsize(self) -> int: ...
+        def put(
+            self,
+            obj: object,
+            timeout: SupportsIndex | None = None,
+            *,
+            unbounditems: _AnyUnbound | None = None,
+            _delay: float = 0.01,
+        ) -> None: ...
+        def put_nowait(self, obj: object, *, unbounditems: _AnyUnbound | None = None) -> None: ...
+        def get(self, timeout: SupportsIndex | None = None, *, _delay: float = 0.01) -> object: ...
+        def get_nowait(self) -> object: ...
diff --git a/mypy/typeshed/stdlib/configparser.pyi b/mypy/typeshed/stdlib/configparser.pyi
index 15c564c02589..764a8a965ea2 100644
--- a/mypy/typeshed/stdlib/configparser.pyi
+++ b/mypy/typeshed/stdlib/configparser.pyi
@@ -2,8 +2,8 @@ import sys
 from _typeshed import MaybeNone, StrOrBytesPath, SupportsWrite
 from collections.abc import Callable, ItemsView, Iterable, Iterator, Mapping, MutableMapping, Sequence
 from re import Pattern
-from typing import Any, ClassVar, Final, Literal, TypeVar, overload
-from typing_extensions import TypeAlias
+from typing import Any, ClassVar, Final, Literal, TypeVar, overload, type_check_only
+from typing_extensions import TypeAlias, deprecated
 
 if sys.version_info >= (3, 14):
     __all__ = (
@@ -104,7 +104,9 @@ else:
     ]
 
 if sys.version_info >= (3, 13):
+    @type_check_only
     class _UNNAMED_SECTION: ...
+
     UNNAMED_SECTION: _UNNAMED_SECTION
 
     _SectionName: TypeAlias = str | _UNNAMED_SECTION
@@ -135,6 +137,9 @@ class BasicInterpolation(Interpolation): ...
 class ExtendedInterpolation(Interpolation): ...
 
 if sys.version_info < (3, 13):
+    @deprecated(
+        "Deprecated since Python 3.2; removed in Python 3.13. Use `BasicInterpolation` or `ExtendedInterpolation` instead."
+    )
     class LegacyInterpolation(Interpolation):
         def before_get(self, parser: _Parser, section: _SectionName, option: str, value: str, vars: _Section) -> str: ...
 
@@ -269,6 +274,7 @@ class RawConfigParser(_Parser):
     def read_string(self, string: str, source: str = "<string>") -> None: ...
     def read_dict(self, dictionary: Mapping[str, Mapping[str, Any]], source: str = "<dict>") -> None: ...
     if sys.version_info < (3, 12):
+        @deprecated("Deprecated since Python 3.2; removed in Python 3.12. Use `parser.read_file()` instead.")
         def readfp(self, fp: Iterable[str], filename: str | None = None) -> None: ...
     # These get* methods are partially applied (with the same names) in
     # SectionProxy; the stubs should be kept updated together
@@ -329,7 +335,8 @@ class ConfigParser(RawConfigParser):
     ) -> str | _T: ...
 
 if sys.version_info < (3, 12):
-    class SafeConfigParser(ConfigParser): ...  # deprecated alias
+    @deprecated("Deprecated since Python 3.2; removed in Python 3.12. Use `ConfigParser` instead.")
+    class SafeConfigParser(ConfigParser): ...
 
 class SectionProxy(MutableMapping[str, str]):
     def __init__(self, parser: RawConfigParser, name: str) -> None: ...
@@ -369,17 +376,17 @@ class SectionProxy(MutableMapping[str, str]):
     # These are partially-applied version of the methods with the same names in
     # RawConfigParser; the stubs should be kept updated together
     @overload
-    def getint(self, option: str, *, raw: bool = ..., vars: _Section | None = ...) -> int | None: ...
+    def getint(self, option: str, *, raw: bool = False, vars: _Section | None = None) -> int | None: ...
     @overload
-    def getint(self, option: str, fallback: _T = ..., *, raw: bool = ..., vars: _Section | None = ...) -> int | _T: ...
+    def getint(self, option: str, fallback: _T = ..., *, raw: bool = False, vars: _Section | None = None) -> int | _T: ...
     @overload
-    def getfloat(self, option: str, *, raw: bool = ..., vars: _Section | None = ...) -> float | None: ...
+    def getfloat(self, option: str, *, raw: bool = False, vars: _Section | None = None) -> float | None: ...
     @overload
-    def getfloat(self, option: str, fallback: _T = ..., *, raw: bool = ..., vars: _Section | None = ...) -> float | _T: ...
+    def getfloat(self, option: str, fallback: _T = ..., *, raw: bool = False, vars: _Section | None = None) -> float | _T: ...
     @overload
-    def getboolean(self, option: str, *, raw: bool = ..., vars: _Section | None = ...) -> bool | None: ...
+    def getboolean(self, option: str, *, raw: bool = False, vars: _Section | None = None) -> bool | None: ...
     @overload
-    def getboolean(self, option: str, fallback: _T = ..., *, raw: bool = ..., vars: _Section | None = ...) -> bool | _T: ...
+    def getboolean(self, option: str, fallback: _T = ..., *, raw: bool = False, vars: _Section | None = None) -> bool | _T: ...
     # SectionProxy can have arbitrary attributes when custom converters are used
     def __getattr__(self, key: str) -> Callable[..., Any]: ...
 
@@ -441,10 +448,25 @@ class ParsingError(Error):
     elif sys.version_info >= (3, 12):
         def __init__(self, source: str) -> None: ...
     else:
-        def __init__(self, source: str | None = None, filename: str | None = None) -> None: ...
+        @overload
+        def __init__(self, source: str) -> None: ...
+        @overload
+        @deprecated("The `filename` parameter removed in Python 3.12. Use `source` instead.")
+        def __init__(self, source: None, filename: str | None) -> None: ...
+        @overload
+        @deprecated("The `filename` parameter removed in Python 3.12. Use `source` instead.")
+        def __init__(self, source: None = None, *, filename: str | None) -> None: ...
 
     def append(self, lineno: int, line: str) -> None: ...
 
+    if sys.version_info < (3, 12):
+        @property
+        @deprecated("Deprecated since Python 3.2; removed in Python 3.12. Use `source` instead.")
+        def filename(self) -> str: ...
+        @filename.setter
+        @deprecated("Deprecated since Python 3.2; removed in Python 3.12. Use `source` instead.")
+        def filename(self, value: str) -> None: ...
+
 class MissingSectionHeaderError(ParsingError):
     lineno: int
     line: str
diff --git a/mypy/typeshed/stdlib/contextlib.pyi b/mypy/typeshed/stdlib/contextlib.pyi
index 4663b448c79c..383a1b7f334b 100644
--- a/mypy/typeshed/stdlib/contextlib.pyi
+++ b/mypy/typeshed/stdlib/contextlib.pyi
@@ -4,7 +4,7 @@ from _typeshed import FileDescriptorOrPath, Unused
 from abc import ABC, abstractmethod
 from collections.abc import AsyncGenerator, AsyncIterator, Awaitable, Callable, Generator, Iterator
 from types import TracebackType
-from typing import IO, Any, Generic, Protocol, TypeVar, overload, runtime_checkable
+from typing import IO, Any, Generic, Protocol, TypeVar, overload, runtime_checkable, type_check_only
 from typing_extensions import ParamSpec, Self, TypeAlias
 
 __all__ = [
@@ -47,6 +47,7 @@ _CM_EF = TypeVar("_CM_EF", bound=AbstractContextManager[Any, Any] | _ExitFunc)
 # allowlist for use as a Protocol.
 @runtime_checkable
 class AbstractContextManager(ABC, Protocol[_T_co, _ExitT_co]):  # type: ignore[misc]  # pyright: ignore[reportGeneralTypeIssues]
+    __slots__ = ()
     def __enter__(self) -> _T_co: ...
     @abstractmethod
     def __exit__(
@@ -58,6 +59,7 @@ class AbstractContextManager(ABC, Protocol[_T_co, _ExitT_co]):  # type: ignore[m
 # allowlist for use as a Protocol.
 @runtime_checkable
 class AbstractAsyncContextManager(ABC, Protocol[_T_co, _ExitT_co]):  # type: ignore[misc]  # pyright: ignore[reportGeneralTypeIssues]
+    __slots__ = ()
     async def __aenter__(self) -> _T_co: ...
     @abstractmethod
     async def __aexit__(
@@ -112,7 +114,7 @@ else:
         ) -> bool | None: ...
 
 def asynccontextmanager(func: Callable[_P, AsyncIterator[_T_co]]) -> Callable[_P, _AsyncGeneratorContextManager[_T_co]]: ...
-
+@type_check_only
 class _SupportsClose(Protocol):
     def close(self) -> object: ...
 
@@ -123,6 +125,7 @@ class closing(AbstractContextManager[_SupportsCloseT, None]):
     def __exit__(self, *exc_info: Unused) -> None: ...
 
 if sys.version_info >= (3, 10):
+    @type_check_only
     class _SupportsAclose(Protocol):
         def aclose(self) -> Awaitable[object]: ...
 
diff --git a/mypy/typeshed/stdlib/copy.pyi b/mypy/typeshed/stdlib/copy.pyi
index 2cceec6a2250..10d2f0ae3710 100644
--- a/mypy/typeshed/stdlib/copy.pyi
+++ b/mypy/typeshed/stdlib/copy.pyi
@@ -1,5 +1,5 @@
 import sys
-from typing import Any, Protocol, TypeVar
+from typing import Any, Protocol, TypeVar, type_check_only
 from typing_extensions import Self
 
 __all__ = ["Error", "copy", "deepcopy"]
@@ -7,6 +7,7 @@ __all__ = ["Error", "copy", "deepcopy"]
 _T = TypeVar("_T")
 _SR = TypeVar("_SR", bound=_SupportsReplace)
 
+@type_check_only
 class _SupportsReplace(Protocol):
     # In reality doesn't support args, but there's no other great way to express this.
     def __replace__(self, *args: Any, **kwargs: Any) -> Self: ...
diff --git a/mypy/typeshed/stdlib/crypt.pyi b/mypy/typeshed/stdlib/crypt.pyi
index bd22b5f8daba..f92632196989 100644
--- a/mypy/typeshed/stdlib/crypt.pyi
+++ b/mypy/typeshed/stdlib/crypt.pyi
@@ -1,5 +1,6 @@
 import sys
 from typing import Final, NamedTuple, type_check_only
+from typing_extensions import disjoint_base
 
 if sys.platform != "win32":
     @type_check_only
@@ -9,7 +10,12 @@ if sys.platform != "win32":
         salt_chars: int
         total_size: int
 
-    class _Method(_MethodBase): ...
+    if sys.version_info >= (3, 12):
+        class _Method(_MethodBase): ...
+    else:
+        @disjoint_base
+        class _Method(_MethodBase): ...
+
     METHOD_CRYPT: Final[_Method]
     METHOD_MD5: Final[_Method]
     METHOD_SHA256: Final[_Method]
diff --git a/mypy/typeshed/stdlib/ctypes/__init__.pyi b/mypy/typeshed/stdlib/ctypes/__init__.pyi
index 0b14bd856784..9da972240abb 100644
--- a/mypy/typeshed/stdlib/ctypes/__init__.pyi
+++ b/mypy/typeshed/stdlib/ctypes/__init__.pyi
@@ -11,6 +11,7 @@ from _ctypes import (
     _CData as _CData,
     _CDataType as _CDataType,
     _CField as _CField,
+    _CTypeBaseType,
     _Pointer as _Pointer,
     _PointerLike as _PointerLike,
     _SimpleCData as _SimpleCData,
@@ -25,14 +26,14 @@ from _ctypes import (
 from _typeshed import StrPath
 from ctypes._endian import BigEndianStructure as BigEndianStructure, LittleEndianStructure as LittleEndianStructure
 from types import GenericAlias
-from typing import Any, ClassVar, Generic, Literal, TypeVar, overload, type_check_only
+from typing import Any, ClassVar, Final, Generic, Literal, TypeVar, overload, type_check_only
 from typing_extensions import Self, TypeAlias, deprecated
 
 if sys.platform == "win32":
     from _ctypes import FormatError as FormatError, get_last_error as get_last_error, set_last_error as set_last_error
 
     if sys.version_info >= (3, 14):
-        from _ctypes import COMError as COMError
+        from _ctypes import COMError as COMError, CopyComPointer as CopyComPointer
 
 if sys.version_info >= (3, 11):
     from ctypes._endian import BigEndianUnion as BigEndianUnion, LittleEndianUnion as LittleEndianUnion
@@ -54,7 +55,7 @@ if sys.version_info >= (3, 14):
 else:
     from _ctypes import POINTER as POINTER, pointer as pointer
 
-DEFAULT_MODE: int
+DEFAULT_MODE: Final[int]
 
 class ArgumentError(Exception): ...
 
@@ -161,8 +162,14 @@ def create_string_buffer(init: int | bytes, size: int | None = None) -> Array[c_
 c_buffer = create_string_buffer
 
 def create_unicode_buffer(init: int | str, size: int | None = None) -> Array[c_wchar]: ...
-@deprecated("Deprecated in Python 3.13; removal scheduled for Python 3.15")
-def SetPointerType(pointer: type[_Pointer[Any]], cls: Any) -> None: ...
+
+if sys.version_info >= (3, 13):
+    @deprecated("Deprecated since Python 3.13; will be removed in Python 3.15.")
+    def SetPointerType(pointer: type[_Pointer[Any]], cls: _CTypeBaseType) -> None: ...
+
+else:
+    def SetPointerType(pointer: type[_Pointer[Any]], cls: _CTypeBaseType) -> None: ...
+
 def ARRAY(typ: _CT, len: int) -> Array[_CT]: ...  # Soft Deprecated, no plans to remove
 
 if sys.platform == "win32":
diff --git a/mypy/typeshed/stdlib/ctypes/_endian.pyi b/mypy/typeshed/stdlib/ctypes/_endian.pyi
index 144f5ba5dd40..97852f67aa6e 100644
--- a/mypy/typeshed/stdlib/ctypes/_endian.pyi
+++ b/mypy/typeshed/stdlib/ctypes/_endian.pyi
@@ -3,10 +3,14 @@ from ctypes import Structure, Union
 
 # At runtime, the native endianness is an alias for Structure,
 # while the other is a subclass with a metaclass added in.
-class BigEndianStructure(Structure): ...
+class BigEndianStructure(Structure):
+    __slots__ = ()
+
 class LittleEndianStructure(Structure): ...
 
 # Same thing for these: one is an alias of Union at runtime
 if sys.version_info >= (3, 11):
-    class BigEndianUnion(Union): ...
+    class BigEndianUnion(Union):
+        __slots__ = ()
+
     class LittleEndianUnion(Union): ...
diff --git a/mypy/typeshed/stdlib/ctypes/macholib/__init__.pyi b/mypy/typeshed/stdlib/ctypes/macholib/__init__.pyi
index bda5b5a7f4cc..c5dd95466063 100644
--- a/mypy/typeshed/stdlib/ctypes/macholib/__init__.pyi
+++ b/mypy/typeshed/stdlib/ctypes/macholib/__init__.pyi
@@ -1 +1,3 @@
-__version__: str
+from typing import Final
+
+__version__: Final[str]
diff --git a/mypy/typeshed/stdlib/ctypes/wintypes.pyi b/mypy/typeshed/stdlib/ctypes/wintypes.pyi
index e9ed0df24dd1..0f0d61a396d5 100644
--- a/mypy/typeshed/stdlib/ctypes/wintypes.pyi
+++ b/mypy/typeshed/stdlib/ctypes/wintypes.pyi
@@ -21,7 +21,7 @@ from ctypes import (
     c_wchar,
     c_wchar_p,
 )
-from typing import Any, TypeVar
+from typing import Any, Final, TypeVar
 from typing_extensions import Self, TypeAlias
 
 if sys.version_info >= (3, 12):
@@ -177,7 +177,7 @@ class MSG(Structure):
     pt: _CField[POINT, POINT, POINT]
 
 tagMSG = MSG
-MAX_PATH: int
+MAX_PATH: Final = 260
 
 class WIN32_FIND_DATAA(Structure):
     dwFileAttributes: _CIntLikeField[DWORD]
diff --git a/mypy/typeshed/stdlib/curses/__init__.pyi b/mypy/typeshed/stdlib/curses/__init__.pyi
index 5c157fd7c2f6..2c0231c13087 100644
--- a/mypy/typeshed/stdlib/curses/__init__.pyi
+++ b/mypy/typeshed/stdlib/curses/__init__.pyi
@@ -14,12 +14,12 @@ _T = TypeVar("_T")
 _P = ParamSpec("_P")
 
 # available after calling `curses.initscr()`
-LINES: int
-COLS: int
+LINES: Final[int]
+COLS: Final[int]
 
 # available after calling `curses.start_color()`
-COLORS: int
-COLOR_PAIRS: int
+COLORS: Final[int]
+COLOR_PAIRS: Final[int]
 
 def wrapper(func: Callable[Concatenate[window, _P], _T], /, *arg: _P.args, **kwds: _P.kwargs) -> _T: ...
 
diff --git a/mypy/typeshed/stdlib/curses/ascii.pyi b/mypy/typeshed/stdlib/curses/ascii.pyi
index 66efbe36a7df..0234434b8c3d 100644
--- a/mypy/typeshed/stdlib/curses/ascii.pyi
+++ b/mypy/typeshed/stdlib/curses/ascii.pyi
@@ -1,45 +1,45 @@
-from typing import TypeVar
+from typing import Final, TypeVar
 
 _CharT = TypeVar("_CharT", str, int)
 
-NUL: int
-SOH: int
-STX: int
-ETX: int
-EOT: int
-ENQ: int
-ACK: int
-BEL: int
-BS: int
-TAB: int
-HT: int
-LF: int
-NL: int
-VT: int
-FF: int
-CR: int
-SO: int
-SI: int
-DLE: int
-DC1: int
-DC2: int
-DC3: int
-DC4: int
-NAK: int
-SYN: int
-ETB: int
-CAN: int
-EM: int
-SUB: int
-ESC: int
-FS: int
-GS: int
-RS: int
-US: int
-SP: int
-DEL: int
+NUL: Final = 0x00
+SOH: Final = 0x01
+STX: Final = 0x02
+ETX: Final = 0x03
+EOT: Final = 0x04
+ENQ: Final = 0x05
+ACK: Final = 0x06
+BEL: Final = 0x07
+BS: Final = 0x08
+TAB: Final = 0x09
+HT: Final = 0x09
+LF: Final = 0x0A
+NL: Final = 0x0A
+VT: Final = 0x0B
+FF: Final = 0x0C
+CR: Final = 0x0D
+SO: Final = 0x0E
+SI: Final = 0x0F
+DLE: Final = 0x10
+DC1: Final = 0x11
+DC2: Final = 0x12
+DC3: Final = 0x13
+DC4: Final = 0x14
+NAK: Final = 0x15
+SYN: Final = 0x16
+ETB: Final = 0x17
+CAN: Final = 0x18
+EM: Final = 0x19
+SUB: Final = 0x1A
+ESC: Final = 0x1B
+FS: Final = 0x1C
+GS: Final = 0x1D
+RS: Final = 0x1E
+US: Final = 0x1F
+SP: Final = 0x20
+DEL: Final = 0x7F
 
-controlnames: list[int]
+controlnames: Final[list[int]]
 
 def isalnum(c: str | int) -> bool: ...
 def isalpha(c: str | int) -> bool: ...
diff --git a/mypy/typeshed/stdlib/dataclasses.pyi b/mypy/typeshed/stdlib/dataclasses.pyi
index c76b0b0e61e2..3a1c8cb5d62d 100644
--- a/mypy/typeshed/stdlib/dataclasses.pyi
+++ b/mypy/typeshed/stdlib/dataclasses.pyi
@@ -5,7 +5,7 @@ from _typeshed import DataclassInstance
 from builtins import type as Type  # alias to avoid name clashes with fields named "type"
 from collections.abc import Callable, Iterable, Mapping
 from types import GenericAlias
-from typing import Any, Generic, Literal, Protocol, TypeVar, overload, type_check_only
+from typing import Any, Final, Generic, Literal, Protocol, TypeVar, overload, type_check_only
 from typing_extensions import Never, TypeIs
 
 _T = TypeVar("_T")
@@ -58,7 +58,7 @@ class _DataclassFactory(Protocol):
 class _MISSING_TYPE(enum.Enum):
     MISSING = enum.auto()
 
-MISSING = _MISSING_TYPE.MISSING
+MISSING: Final = _MISSING_TYPE.MISSING
 
 if sys.version_info >= (3, 10):
     class KW_ONLY: ...
@@ -165,10 +165,42 @@ else:
     ) -> Callable[[type[_T]], type[_T]]: ...
 
 # See https://github.com/python/mypy/issues/10750
+@type_check_only
 class _DefaultFactory(Protocol[_T_co]):
     def __call__(self) -> _T_co: ...
 
 class Field(Generic[_T]):
+    if sys.version_info >= (3, 14):
+        __slots__ = (
+            "name",
+            "type",
+            "default",
+            "default_factory",
+            "repr",
+            "hash",
+            "init",
+            "compare",
+            "metadata",
+            "kw_only",
+            "doc",
+            "_field_type",
+        )
+    elif sys.version_info >= (3, 10):
+        __slots__ = (
+            "name",
+            "type",
+            "default",
+            "default_factory",
+            "repr",
+            "hash",
+            "init",
+            "compare",
+            "metadata",
+            "kw_only",
+            "_field_type",
+        )
+    else:
+        __slots__ = ("name", "type", "default", "default_factory", "repr", "hash", "init", "compare", "metadata", "_field_type")
     name: str
     type: Type[_T] | str | Any
     default: _T | Literal[_MISSING_TYPE.MISSING]
@@ -354,6 +386,7 @@ def is_dataclass(obj: object) -> TypeIs[DataclassInstance | type[DataclassInstan
 class FrozenInstanceError(AttributeError): ...
 
 class InitVar(Generic[_T]):
+    __slots__ = ("type",)
     type: Type[_T]
     def __init__(self, type: Type[_T]) -> None: ...
     @overload
diff --git a/mypy/typeshed/stdlib/datetime.pyi b/mypy/typeshed/stdlib/datetime.pyi
index 37d6a06dfff9..8a0536c006d5 100644
--- a/mypy/typeshed/stdlib/datetime.pyi
+++ b/mypy/typeshed/stdlib/datetime.pyi
@@ -2,7 +2,7 @@ import sys
 from abc import abstractmethod
 from time import struct_time
 from typing import ClassVar, Final, NoReturn, SupportsIndex, final, overload, type_check_only
-from typing_extensions import CapsuleType, Self, TypeAlias, deprecated
+from typing_extensions import CapsuleType, Self, TypeAlias, deprecated, disjoint_base
 
 if sys.version_info >= (3, 11):
     __all__ = ("date", "datetime", "time", "timedelta", "timezone", "tzinfo", "MINYEAR", "MAXYEAR", "UTC")
@@ -51,6 +51,7 @@ class _IsoCalendarDate(tuple[int, int, int]):
     @property
     def weekday(self) -> int: ...
 
+@disjoint_base
 class date:
     min: ClassVar[date]
     max: ClassVar[date]
@@ -112,19 +113,20 @@ class date:
     def isoweekday(self) -> int: ...
     def isocalendar(self) -> _IsoCalendarDate: ...
 
+@disjoint_base
 class time:
     min: ClassVar[time]
     max: ClassVar[time]
     resolution: ClassVar[timedelta]
     def __new__(
         cls,
-        hour: SupportsIndex = ...,
-        minute: SupportsIndex = ...,
-        second: SupportsIndex = ...,
-        microsecond: SupportsIndex = ...,
-        tzinfo: _TzInfo | None = ...,
+        hour: SupportsIndex = 0,
+        minute: SupportsIndex = 0,
+        second: SupportsIndex = 0,
+        microsecond: SupportsIndex = 0,
+        tzinfo: _TzInfo | None = None,
         *,
-        fold: int = ...,
+        fold: int = 0,
     ) -> Self: ...
     @property
     def hour(self) -> int: ...
@@ -144,7 +146,7 @@ class time:
     def __gt__(self, value: time, /) -> bool: ...
     def __eq__(self, value: object, /) -> bool: ...
     def __hash__(self) -> int: ...
-    def isoformat(self, timespec: str = ...) -> str: ...
+    def isoformat(self, timespec: str = "auto") -> str: ...
     @classmethod
     def fromisoformat(cls, time_string: str, /) -> Self: ...
 
@@ -191,19 +193,20 @@ class time:
 _Date: TypeAlias = date
 _Time: TypeAlias = time
 
+@disjoint_base
 class timedelta:
     min: ClassVar[timedelta]
     max: ClassVar[timedelta]
     resolution: ClassVar[timedelta]
     def __new__(
         cls,
-        days: float = ...,
-        seconds: float = ...,
-        microseconds: float = ...,
-        milliseconds: float = ...,
-        minutes: float = ...,
-        hours: float = ...,
-        weeks: float = ...,
+        days: float = 0,
+        seconds: float = 0,
+        microseconds: float = 0,
+        milliseconds: float = 0,
+        minutes: float = 0,
+        hours: float = 0,
+        weeks: float = 0,
     ) -> Self: ...
     @property
     def days(self) -> int: ...
@@ -239,6 +242,7 @@ class timedelta:
     def __bool__(self) -> bool: ...
     def __hash__(self) -> int: ...
 
+@disjoint_base
 class datetime(date):
     min: ClassVar[datetime]
     max: ClassVar[datetime]
@@ -247,13 +251,13 @@ class datetime(date):
         year: SupportsIndex,
         month: SupportsIndex,
         day: SupportsIndex,
-        hour: SupportsIndex = ...,
-        minute: SupportsIndex = ...,
-        second: SupportsIndex = ...,
-        microsecond: SupportsIndex = ...,
-        tzinfo: _TzInfo | None = ...,
+        hour: SupportsIndex = 0,
+        minute: SupportsIndex = 0,
+        second: SupportsIndex = 0,
+        microsecond: SupportsIndex = 0,
+        tzinfo: _TzInfo | None = None,
         *,
-        fold: int = ...,
+        fold: int = 0,
     ) -> Self: ...
     @property
     def hour(self) -> int: ...
@@ -272,10 +276,10 @@ class datetime(date):
     # meaning it is only *safe* to pass it as a keyword argument on 3.12+
     if sys.version_info >= (3, 12):
         @classmethod
-        def fromtimestamp(cls, timestamp: float, tz: _TzInfo | None = ...) -> Self: ...
+        def fromtimestamp(cls, timestamp: float, tz: _TzInfo | None = None) -> Self: ...
     else:
         @classmethod
-        def fromtimestamp(cls, timestamp: float, /, tz: _TzInfo | None = ...) -> Self: ...
+        def fromtimestamp(cls, timestamp: float, /, tz: _TzInfo | None = None) -> Self: ...
 
     @classmethod
     @deprecated("Use timezone-aware objects to represent datetimes in UTC; e.g. by calling .fromtimestamp(datetime.timezone.utc)")
@@ -321,8 +325,8 @@ class datetime(date):
         *,
         fold: int = ...,
     ) -> Self: ...
-    def astimezone(self, tz: _TzInfo | None = ...) -> Self: ...
-    def isoformat(self, sep: str = ..., timespec: str = ...) -> str: ...
+    def astimezone(self, tz: _TzInfo | None = None) -> Self: ...
+    def isoformat(self, sep: str = "T", timespec: str = "auto") -> str: ...
     @classmethod
     def strptime(cls, date_string: str, format: str, /) -> Self: ...
     def utcoffset(self) -> timedelta | None: ...
diff --git a/mypy/typeshed/stdlib/dbm/__init__.pyi b/mypy/typeshed/stdlib/dbm/__init__.pyi
index 7f344060f9ab..7cbb63cf2f06 100644
--- a/mypy/typeshed/stdlib/dbm/__init__.pyi
+++ b/mypy/typeshed/stdlib/dbm/__init__.pyi
@@ -76,6 +76,7 @@ _TFlags: TypeAlias = Literal[
     "nusf",
 ]
 
+@type_check_only
 class _Database(MutableMapping[_KeyType, bytes]):
     def close(self) -> None: ...
     def __getitem__(self, key: _KeyType) -> bytes: ...
diff --git a/mypy/typeshed/stdlib/decimal.pyi b/mypy/typeshed/stdlib/decimal.pyi
index b85c00080092..2e06c2d1b724 100644
--- a/mypy/typeshed/stdlib/decimal.pyi
+++ b/mypy/typeshed/stdlib/decimal.pyi
@@ -27,7 +27,7 @@ from _decimal import (
 from collections.abc import Container, Sequence
 from types import TracebackType
 from typing import Any, ClassVar, Literal, NamedTuple, final, overload, type_check_only
-from typing_extensions import Self, TypeAlias
+from typing_extensions import Self, TypeAlias, disjoint_base
 
 if sys.version_info >= (3, 14):
     from _decimal import IEEE_CONTEXT_MAX_BITS as IEEE_CONTEXT_MAX_BITS, IEEEContext as IEEEContext
@@ -68,6 +68,7 @@ class Overflow(Inexact, Rounded): ...
 class Underflow(Inexact, Rounded, Subnormal): ...
 class FloatOperation(DecimalException, TypeError): ...
 
+@disjoint_base
 class Decimal:
     def __new__(cls, value: _DecimalNew = "0", context: Context | None = None) -> Self: ...
     if sys.version_info >= (3, 14):
@@ -173,6 +174,7 @@ class Decimal:
     def __deepcopy__(self, memo: Any, /) -> Self: ...
     def __format__(self, specifier: str, context: Context | None = None, /) -> str: ...
 
+@disjoint_base
 class Context:
     # TODO: Context doesn't allow you to delete *any* attributes from instances of the class at runtime,
     # even settable attributes like `prec` and `rounding`,
diff --git a/mypy/typeshed/stdlib/difflib.pyi b/mypy/typeshed/stdlib/difflib.pyi
index 18583a3acfe9..6efe68322bb6 100644
--- a/mypy/typeshed/stdlib/difflib.pyi
+++ b/mypy/typeshed/stdlib/difflib.pyi
@@ -1,3 +1,5 @@
+import re
+import sys
 from collections.abc import Callable, Iterable, Iterator, Sequence
 from types import GenericAlias
 from typing import Any, AnyStr, Generic, Literal, NamedTuple, TypeVar, overload
@@ -60,7 +62,12 @@ class Differ:
     def __init__(self, linejunk: Callable[[str], bool] | None = None, charjunk: Callable[[str], bool] | None = None) -> None: ...
     def compare(self, a: Sequence[str], b: Sequence[str]) -> Iterator[str]: ...
 
-def IS_LINE_JUNK(line: str, pat: Any = ...) -> bool: ...  # pat is undocumented
+if sys.version_info >= (3, 14):
+    def IS_LINE_JUNK(line: str, pat: Callable[[str], re.Match[str] | None] | None = None) -> bool: ...
+
+else:
+    def IS_LINE_JUNK(line: str, pat: Callable[[str], re.Match[str] | None] = ...) -> bool: ...
+
 def IS_CHARACTER_JUNK(ch: str, ws: str = " \t") -> bool: ...  # ws is undocumented
 def unified_diff(
     a: Sequence[str],
diff --git a/mypy/typeshed/stdlib/dis.pyi b/mypy/typeshed/stdlib/dis.pyi
index 86b6d01e3120..896b50fa9384 100644
--- a/mypy/typeshed/stdlib/dis.pyi
+++ b/mypy/typeshed/stdlib/dis.pyi
@@ -2,8 +2,8 @@ import sys
 import types
 from collections.abc import Callable, Iterator
 from opcode import *  # `dis` re-exports it as a part of public API
-from typing import IO, Any, NamedTuple
-from typing_extensions import Self, TypeAlias
+from typing import IO, Any, Final, NamedTuple
+from typing_extensions import Self, TypeAlias, disjoint_base
 
 __all__ = [
     "code_info",
@@ -88,39 +88,45 @@ else:
         starts_line: int | None
         is_jump_target: bool
 
-class Instruction(_Instruction):
-    if sys.version_info < (3, 13):
+if sys.version_info >= (3, 12):
+    class Instruction(_Instruction):
+        if sys.version_info < (3, 13):
+            def _disassemble(self, lineno_width: int = 3, mark_as_current: bool = False, offset_width: int = 4) -> str: ...
+        if sys.version_info >= (3, 13):
+            @property
+            def oparg(self) -> int: ...
+            @property
+            def baseopcode(self) -> int: ...
+            @property
+            def baseopname(self) -> str: ...
+            @property
+            def cache_offset(self) -> int: ...
+            @property
+            def end_offset(self) -> int: ...
+            @property
+            def jump_target(self) -> int: ...
+            @property
+            def is_jump_target(self) -> bool: ...
+        if sys.version_info >= (3, 14):
+            @staticmethod
+            def make(
+                opname: str,
+                arg: int | None,
+                argval: Any,
+                argrepr: str,
+                offset: int,
+                start_offset: int,
+                starts_line: bool,
+                line_number: int | None,
+                label: int | None = None,
+                positions: Positions | None = None,
+                cache_info: list[tuple[str, int, Any]] | None = None,
+            ) -> Instruction: ...
+
+else:
+    @disjoint_base
+    class Instruction(_Instruction):
         def _disassemble(self, lineno_width: int = 3, mark_as_current: bool = False, offset_width: int = 4) -> str: ...
-    if sys.version_info >= (3, 13):
-        @property
-        def oparg(self) -> int: ...
-        @property
-        def baseopcode(self) -> int: ...
-        @property
-        def baseopname(self) -> str: ...
-        @property
-        def cache_offset(self) -> int: ...
-        @property
-        def end_offset(self) -> int: ...
-        @property
-        def jump_target(self) -> int: ...
-        @property
-        def is_jump_target(self) -> bool: ...
-    if sys.version_info >= (3, 14):
-        @staticmethod
-        def make(
-            opname: str,
-            arg: int | None,
-            argval: Any,
-            argrepr: str,
-            offset: int,
-            start_offset: int,
-            starts_line: bool,
-            line_number: int | None,
-            label: int | None = None,
-            positions: Positions | None = None,
-            cache_info: list[tuple[str, int, Any]] | None = None,
-        ) -> Instruction: ...
 
 class Bytecode:
     codeobj: types.CodeType
@@ -178,7 +184,7 @@ class Bytecode:
     def info(self) -> str: ...
     def dis(self) -> str: ...
 
-COMPILER_FLAG_NAMES: dict[int, str]
+COMPILER_FLAG_NAMES: Final[dict[int, str]]
 
 def findlabels(code: _HaveCodeType) -> list[int]: ...
 def findlinestarts(code: _HaveCodeType) -> Iterator[tuple[int, int]]: ...
diff --git a/mypy/typeshed/stdlib/distutils/file_util.pyi b/mypy/typeshed/stdlib/distutils/file_util.pyi
index 873d23ea7e50..c763f91a958d 100644
--- a/mypy/typeshed/stdlib/distutils/file_util.pyi
+++ b/mypy/typeshed/stdlib/distutils/file_util.pyi
@@ -29,10 +29,10 @@ def copy_file(
 ) -> tuple[_BytesPathT | bytes, bool]: ...
 @overload
 def move_file(
-    src: StrPath, dst: _StrPathT, verbose: bool | Literal[0, 1] = 0, dry_run: bool | Literal[0, 1] = 0
+    src: StrPath, dst: _StrPathT, verbose: bool | Literal[0, 1] = 1, dry_run: bool | Literal[0, 1] = 0
 ) -> _StrPathT | str: ...
 @overload
 def move_file(
-    src: BytesPath, dst: _BytesPathT, verbose: bool | Literal[0, 1] = 0, dry_run: bool | Literal[0, 1] = 0
+    src: BytesPath, dst: _BytesPathT, verbose: bool | Literal[0, 1] = 1, dry_run: bool | Literal[0, 1] = 0
 ) -> _BytesPathT | bytes: ...
 def write_file(filename: StrOrBytesPath, contents: Iterable[str]) -> None: ...
diff --git a/mypy/typeshed/stdlib/doctest.pyi b/mypy/typeshed/stdlib/doctest.pyi
index 562b5a5bdac9..1bb96e1a7786 100644
--- a/mypy/typeshed/stdlib/doctest.pyi
+++ b/mypy/typeshed/stdlib/doctest.pyi
@@ -3,7 +3,7 @@ import types
 import unittest
 from _typeshed import ExcInfo
 from collections.abc import Callable
-from typing import Any, NamedTuple, type_check_only
+from typing import Any, Final, NamedTuple, type_check_only
 from typing_extensions import Self, TypeAlias
 
 __all__ = [
@@ -57,29 +57,29 @@ else:
         failed: int
         attempted: int
 
-OPTIONFLAGS_BY_NAME: dict[str, int]
+OPTIONFLAGS_BY_NAME: Final[dict[str, int]]
 
 def register_optionflag(name: str) -> int: ...
 
-DONT_ACCEPT_TRUE_FOR_1: int
-DONT_ACCEPT_BLANKLINE: int
-NORMALIZE_WHITESPACE: int
-ELLIPSIS: int
-SKIP: int
-IGNORE_EXCEPTION_DETAIL: int
+DONT_ACCEPT_TRUE_FOR_1: Final = 1
+DONT_ACCEPT_BLANKLINE: Final = 2
+NORMALIZE_WHITESPACE: Final = 4
+ELLIPSIS: Final = 8
+SKIP: Final = 16
+IGNORE_EXCEPTION_DETAIL: Final = 32
 
-COMPARISON_FLAGS: int
+COMPARISON_FLAGS: Final = 63
 
-REPORT_UDIFF: int
-REPORT_CDIFF: int
-REPORT_NDIFF: int
-REPORT_ONLY_FIRST_FAILURE: int
-FAIL_FAST: int
+REPORT_UDIFF: Final = 64
+REPORT_CDIFF: Final = 128
+REPORT_NDIFF: Final = 256
+REPORT_ONLY_FIRST_FAILURE: Final = 512
+FAIL_FAST: Final = 1024
 
-REPORTING_FLAGS: int
+REPORTING_FLAGS: Final = 1984
 
-BLANKLINE_MARKER: str
-ELLIPSIS_MARKER: str
+BLANKLINE_MARKER: Final = "<BLANKLINE>"
+ELLIPSIS_MARKER: Final = "..."
 
 class Example:
     source: str
diff --git a/mypy/typeshed/stdlib/email/_header_value_parser.pyi b/mypy/typeshed/stdlib/email/_header_value_parser.pyi
index a8abfead9217..dededd006e5b 100644
--- a/mypy/typeshed/stdlib/email/_header_value_parser.pyi
+++ b/mypy/typeshed/stdlib/email/_header_value_parser.pyi
@@ -1,4 +1,3 @@
-import sys
 from collections.abc import Iterable, Iterator
 from email.errors import HeaderParseError, MessageDefect
 from email.policy import Policy
@@ -22,13 +21,11 @@ NLSET: Final[set[str]]
 # Added in Python 3.9.20, 3.10.15, 3.11.10, 3.12.5
 SPECIALSNL: Final[set[str]]
 
-if sys.version_info >= (3, 10):
-    # Added in Python 3.10.17, 3.11.12, 3.12.9, 3.13.2 (may still be backported to 3.9)
-    def make_quoted_pairs(value: Any) -> str: ...
-
+# Added in Python 3.9.23, 3.10.17, 3.11.12, 3.12.9, 3.13.2
+def make_quoted_pairs(value: Any) -> str: ...
 def quote_string(value: Any) -> str: ...
 
-rfc2047_matcher: Pattern[str]
+rfc2047_matcher: Final[Pattern[str]]
 
 class TokenList(list[TokenList | Terminal]):
     token_type: str | None
diff --git a/mypy/typeshed/stdlib/email/charset.pyi b/mypy/typeshed/stdlib/email/charset.pyi
index 683daa468cf3..e1930835bbd1 100644
--- a/mypy/typeshed/stdlib/email/charset.pyi
+++ b/mypy/typeshed/stdlib/email/charset.pyi
@@ -4,9 +4,16 @@ from typing import ClassVar, Final, overload
 
 __all__ = ["Charset", "add_alias", "add_charset", "add_codec"]
 
-QP: Final[int]  # undocumented
-BASE64: Final[int]  # undocumented
-SHORTEST: Final[int]  # undocumented
+QP: Final = 1  # undocumented
+BASE64: Final = 2  # undocumented
+SHORTEST: Final = 3  # undocumented
+RFC2047_CHROME_LEN: Final = 7  # undocumented
+DEFAULT_CHARSET: Final = "us-ascii"  # undocumented
+UNKNOWN8BIT: Final = "unknown-8bit"  # undocumented
+EMPTYSTRING: Final = ""  # undocumented
+CHARSETS: Final[dict[str, tuple[int | None, int | None, str | None]]]
+ALIASES: Final[dict[str, str]]
+CODEC_MAP: Final[dict[str, str | None]]  # undocumented
 
 class Charset:
     input_charset: str
diff --git a/mypy/typeshed/stdlib/email/headerregistry.pyi b/mypy/typeshed/stdlib/email/headerregistry.pyi
index dc641c8c952b..dff9593b731f 100644
--- a/mypy/typeshed/stdlib/email/headerregistry.pyi
+++ b/mypy/typeshed/stdlib/email/headerregistry.pyi
@@ -13,7 +13,7 @@ from email._header_value_parser import (
 )
 from email.errors import MessageDefect
 from email.policy import Policy
-from typing import Any, ClassVar, Literal, Protocol
+from typing import Any, ClassVar, Literal, Protocol, type_check_only
 from typing_extensions import Self
 
 class BaseHeader(str):
@@ -137,6 +137,7 @@ class MessageIDHeader:
     @staticmethod
     def value_parser(value: str) -> MessageID: ...
 
+@type_check_only
 class _HeaderParser(Protocol):
     max_count: ClassVar[Literal[1] | None]
     @staticmethod
diff --git a/mypy/typeshed/stdlib/email/message.pyi b/mypy/typeshed/stdlib/email/message.pyi
index e4d14992168a..794882b140e6 100644
--- a/mypy/typeshed/stdlib/email/message.pyi
+++ b/mypy/typeshed/stdlib/email/message.pyi
@@ -5,7 +5,7 @@ from email.charset import Charset
 from email.contentmanager import ContentManager
 from email.errors import MessageDefect
 from email.policy import Policy
-from typing import Any, Generic, Literal, Protocol, TypeVar, overload
+from typing import Any, Generic, Literal, Protocol, TypeVar, overload, type_check_only
 from typing_extensions import Self, TypeAlias
 
 __all__ = ["Message", "EmailMessage"]
@@ -24,9 +24,11 @@ _EncodedPayloadType: TypeAlias = Message | bytes
 _MultipartPayloadType: TypeAlias = list[_PayloadType]
 _CharsetType: TypeAlias = Charset | str | None
 
+@type_check_only
 class _SupportsEncodeToPayload(Protocol):
     def encode(self, encoding: str, /) -> _PayloadType | _MultipartPayloadType | _SupportsDecodeToPayload: ...
 
+@type_check_only
 class _SupportsDecodeToPayload(Protocol):
     def decode(self, encoding: str, errors: str, /) -> _PayloadType | _MultipartPayloadType: ...
 
diff --git a/mypy/typeshed/stdlib/encodings/__init__.pyi b/mypy/typeshed/stdlib/encodings/__init__.pyi
index 12ec6792d49b..61f86d243c72 100644
--- a/mypy/typeshed/stdlib/encodings/__init__.pyi
+++ b/mypy/typeshed/stdlib/encodings/__init__.pyi
@@ -1,3 +1,4 @@
+import sys
 from codecs import CodecInfo
 
 class CodecRegistryError(LookupError, SystemError): ...
@@ -5,5 +6,8 @@ class CodecRegistryError(LookupError, SystemError): ...
 def normalize_encoding(encoding: str | bytes) -> str: ...
 def search_function(encoding: str) -> CodecInfo | None: ...
 
+if sys.version_info >= (3, 14) and sys.platform == "win32":
+    def win32_code_page_search_function(encoding: str) -> CodecInfo | None: ...
+
 # Needed for submodules
 def __getattr__(name: str): ...  # incomplete module
diff --git a/mypy/typeshed/stdlib/enum.pyi b/mypy/typeshed/stdlib/enum.pyi
index 327b135459a0..4ac860f5e611 100644
--- a/mypy/typeshed/stdlib/enum.pyi
+++ b/mypy/typeshed/stdlib/enum.pyi
@@ -4,8 +4,8 @@ import types
 from _typeshed import SupportsKeysAndGetItem, Unused
 from builtins import property as _builtins_property
 from collections.abc import Callable, Iterable, Iterator, Mapping
-from typing import Any, Generic, Literal, TypeVar, overload
-from typing_extensions import Self, TypeAlias
+from typing import Any, Final, Generic, Literal, TypeVar, overload
+from typing_extensions import Self, TypeAlias, disjoint_base
 
 __all__ = ["EnumMeta", "Enum", "IntEnum", "Flag", "IntFlag", "auto", "unique"]
 
@@ -219,20 +219,34 @@ class Enum(metaclass=EnumMeta):
     if sys.version_info >= (3, 12) and sys.version_info < (3, 14):
         @classmethod
         def __signature__(cls) -> str: ...
+    if sys.version_info >= (3, 13):
+        # Value may be any type, even in special enums. Enabling Enum parsing from
+        # multiple value types
+        def _add_value_alias_(self, value: Any) -> None: ...
+        def _add_alias_(self, name: str) -> None: ...
 
 if sys.version_info >= (3, 11):
     class ReprEnum(Enum): ...
 
-if sys.version_info >= (3, 11):
-    _IntEnumBase = ReprEnum
+if sys.version_info >= (3, 12):
+    class IntEnum(int, ReprEnum):
+        _value_: int
+        @_magic_enum_attr
+        def value(self) -> int: ...
+        def __new__(cls, value: int) -> Self: ...
+
 else:
-    _IntEnumBase = Enum
+    if sys.version_info >= (3, 11):
+        _IntEnumBase = ReprEnum
+    else:
+        _IntEnumBase = Enum
 
-class IntEnum(int, _IntEnumBase):
-    _value_: int
-    @_magic_enum_attr
-    def value(self) -> int: ...
-    def __new__(cls, value: int) -> Self: ...
+    @disjoint_base
+    class IntEnum(int, _IntEnumBase):
+        _value_: int
+        @_magic_enum_attr
+        def value(self) -> int: ...
+        def __new__(cls, value: int) -> Self: ...
 
 def unique(enumeration: _EnumerationT) -> _EnumerationT: ...
 
@@ -272,9 +286,9 @@ if sys.version_info >= (3, 11):
         NAMED_FLAGS = "multi-flag aliases may not contain unnamed flags"
         UNIQUE = "one name per value"
 
-    CONTINUOUS = EnumCheck.CONTINUOUS
-    NAMED_FLAGS = EnumCheck.NAMED_FLAGS
-    UNIQUE = EnumCheck.UNIQUE
+    CONTINUOUS: Final = EnumCheck.CONTINUOUS
+    NAMED_FLAGS: Final = EnumCheck.NAMED_FLAGS
+    UNIQUE: Final = EnumCheck.UNIQUE
 
     class verify:
         def __init__(self, *checks: EnumCheck) -> None: ...
@@ -286,18 +300,31 @@ if sys.version_info >= (3, 11):
         EJECT = "eject"
         KEEP = "keep"
 
-    STRICT = FlagBoundary.STRICT
-    CONFORM = FlagBoundary.CONFORM
-    EJECT = FlagBoundary.EJECT
-    KEEP = FlagBoundary.KEEP
+    STRICT: Final = FlagBoundary.STRICT
+    CONFORM: Final = FlagBoundary.CONFORM
+    EJECT: Final = FlagBoundary.EJECT
+    KEEP: Final = FlagBoundary.KEEP
 
     def global_str(self: Enum) -> str: ...
     def global_enum(cls: _EnumerationT, update_str: bool = False) -> _EnumerationT: ...
     def global_enum_repr(self: Enum) -> str: ...
     def global_flag_repr(self: Flag) -> str: ...
 
-if sys.version_info >= (3, 11):
+if sys.version_info >= (3, 12):
+    # The body of the class is the same, but the base classes are different.
+    class IntFlag(int, ReprEnum, Flag, boundary=KEEP):  # type: ignore[misc]  # complaints about incompatible bases
+        def __new__(cls, value: int) -> Self: ...
+        def __or__(self, other: int) -> Self: ...
+        def __and__(self, other: int) -> Self: ...
+        def __xor__(self, other: int) -> Self: ...
+        def __invert__(self) -> Self: ...
+        __ror__ = __or__
+        __rand__ = __and__
+        __rxor__ = __xor__
+
+elif sys.version_info >= (3, 11):
     # The body of the class is the same, but the base classes are different.
+    @disjoint_base
     class IntFlag(int, ReprEnum, Flag, boundary=KEEP):  # type: ignore[misc]  # complaints about incompatible bases
         def __new__(cls, value: int) -> Self: ...
         def __or__(self, other: int) -> Self: ...
@@ -309,6 +336,7 @@ if sys.version_info >= (3, 11):
         __rxor__ = __xor__
 
 else:
+    @disjoint_base
     class IntFlag(int, Flag):  # type: ignore[misc]  # complaints about incompatible bases
         def __new__(cls, value: int) -> Self: ...
         def __or__(self, other: int) -> Self: ...
diff --git a/mypy/typeshed/stdlib/errno.pyi b/mypy/typeshed/stdlib/errno.pyi
index 3ba8b66d2865..4f19b5aee87e 100644
--- a/mypy/typeshed/stdlib/errno.pyi
+++ b/mypy/typeshed/stdlib/errno.pyi
@@ -1,225 +1,226 @@
 import sys
 from collections.abc import Mapping
+from typing import Final
 
 errorcode: Mapping[int, str]
 
-EPERM: int
-ENOENT: int
-ESRCH: int
-EINTR: int
-EIO: int
-ENXIO: int
-E2BIG: int
-ENOEXEC: int
-EBADF: int
-ECHILD: int
-EAGAIN: int
-ENOMEM: int
-EACCES: int
-EFAULT: int
-EBUSY: int
-EEXIST: int
-EXDEV: int
-ENODEV: int
-ENOTDIR: int
-EISDIR: int
-EINVAL: int
-ENFILE: int
-EMFILE: int
-ENOTTY: int
-ETXTBSY: int
-EFBIG: int
-ENOSPC: int
-ESPIPE: int
-EROFS: int
-EMLINK: int
-EPIPE: int
-EDOM: int
-ERANGE: int
-EDEADLK: int
-ENAMETOOLONG: int
-ENOLCK: int
-ENOSYS: int
-ENOTEMPTY: int
-ELOOP: int
-EWOULDBLOCK: int
-ENOMSG: int
-EIDRM: int
-ENOSTR: int
-ENODATA: int
-ETIME: int
-ENOSR: int
-EREMOTE: int
-ENOLINK: int
-EPROTO: int
-EBADMSG: int
-EOVERFLOW: int
-EILSEQ: int
-EUSERS: int
-ENOTSOCK: int
-EDESTADDRREQ: int
-EMSGSIZE: int
-EPROTOTYPE: int
-ENOPROTOOPT: int
-EPROTONOSUPPORT: int
-ESOCKTNOSUPPORT: int
-ENOTSUP: int
-EOPNOTSUPP: int
-EPFNOSUPPORT: int
-EAFNOSUPPORT: int
-EADDRINUSE: int
-EADDRNOTAVAIL: int
-ENETDOWN: int
-ENETUNREACH: int
-ENETRESET: int
-ECONNABORTED: int
-ECONNRESET: int
-ENOBUFS: int
-EISCONN: int
-ENOTCONN: int
-ESHUTDOWN: int
-ETOOMANYREFS: int
-ETIMEDOUT: int
-ECONNREFUSED: int
-EHOSTDOWN: int
-EHOSTUNREACH: int
-EALREADY: int
-EINPROGRESS: int
-ESTALE: int
-EDQUOT: int
-ECANCELED: int  # undocumented
-ENOTRECOVERABLE: int  # undocumented
-EOWNERDEAD: int  # undocumented
+EPERM: Final[int]
+ENOENT: Final[int]
+ESRCH: Final[int]
+EINTR: Final[int]
+EIO: Final[int]
+ENXIO: Final[int]
+E2BIG: Final[int]
+ENOEXEC: Final[int]
+EBADF: Final[int]
+ECHILD: Final[int]
+EAGAIN: Final[int]
+ENOMEM: Final[int]
+EACCES: Final[int]
+EFAULT: Final[int]
+EBUSY: Final[int]
+EEXIST: Final[int]
+EXDEV: Final[int]
+ENODEV: Final[int]
+ENOTDIR: Final[int]
+EISDIR: Final[int]
+EINVAL: Final[int]
+ENFILE: Final[int]
+EMFILE: Final[int]
+ENOTTY: Final[int]
+ETXTBSY: Final[int]
+EFBIG: Final[int]
+ENOSPC: Final[int]
+ESPIPE: Final[int]
+EROFS: Final[int]
+EMLINK: Final[int]
+EPIPE: Final[int]
+EDOM: Final[int]
+ERANGE: Final[int]
+EDEADLK: Final[int]
+ENAMETOOLONG: Final[int]
+ENOLCK: Final[int]
+ENOSYS: Final[int]
+ENOTEMPTY: Final[int]
+ELOOP: Final[int]
+EWOULDBLOCK: Final[int]
+ENOMSG: Final[int]
+EIDRM: Final[int]
+ENOSTR: Final[int]
+ENODATA: Final[int]
+ETIME: Final[int]
+ENOSR: Final[int]
+EREMOTE: Final[int]
+ENOLINK: Final[int]
+EPROTO: Final[int]
+EBADMSG: Final[int]
+EOVERFLOW: Final[int]
+EILSEQ: Final[int]
+EUSERS: Final[int]
+ENOTSOCK: Final[int]
+EDESTADDRREQ: Final[int]
+EMSGSIZE: Final[int]
+EPROTOTYPE: Final[int]
+ENOPROTOOPT: Final[int]
+EPROTONOSUPPORT: Final[int]
+ESOCKTNOSUPPORT: Final[int]
+ENOTSUP: Final[int]
+EOPNOTSUPP: Final[int]
+EPFNOSUPPORT: Final[int]
+EAFNOSUPPORT: Final[int]
+EADDRINUSE: Final[int]
+EADDRNOTAVAIL: Final[int]
+ENETDOWN: Final[int]
+ENETUNREACH: Final[int]
+ENETRESET: Final[int]
+ECONNABORTED: Final[int]
+ECONNRESET: Final[int]
+ENOBUFS: Final[int]
+EISCONN: Final[int]
+ENOTCONN: Final[int]
+ESHUTDOWN: Final[int]
+ETOOMANYREFS: Final[int]
+ETIMEDOUT: Final[int]
+ECONNREFUSED: Final[int]
+EHOSTDOWN: Final[int]
+EHOSTUNREACH: Final[int]
+EALREADY: Final[int]
+EINPROGRESS: Final[int]
+ESTALE: Final[int]
+EDQUOT: Final[int]
+ECANCELED: Final[int]  # undocumented
+ENOTRECOVERABLE: Final[int]  # undocumented
+EOWNERDEAD: Final[int]  # undocumented
 
 if sys.platform == "sunos5" or sys.platform == "solaris":  # noqa: Y008
-    ELOCKUNMAPPED: int
-    ENOTACTIVE: int
+    ELOCKUNMAPPED: Final[int]
+    ENOTACTIVE: Final[int]
 
 if sys.platform != "win32":
-    ENOTBLK: int
-    EMULTIHOP: int
+    ENOTBLK: Final[int]
+    EMULTIHOP: Final[int]
 
 if sys.platform == "darwin":
     # All of the below are undocumented
-    EAUTH: int
-    EBADARCH: int
-    EBADEXEC: int
-    EBADMACHO: int
-    EBADRPC: int
-    EDEVERR: int
-    EFTYPE: int
-    ENEEDAUTH: int
-    ENOATTR: int
-    ENOPOLICY: int
-    EPROCLIM: int
-    EPROCUNAVAIL: int
-    EPROGMISMATCH: int
-    EPROGUNAVAIL: int
-    EPWROFF: int
-    ERPCMISMATCH: int
-    ESHLIBVERS: int
+    EAUTH: Final[int]
+    EBADARCH: Final[int]
+    EBADEXEC: Final[int]
+    EBADMACHO: Final[int]
+    EBADRPC: Final[int]
+    EDEVERR: Final[int]
+    EFTYPE: Final[int]
+    ENEEDAUTH: Final[int]
+    ENOATTR: Final[int]
+    ENOPOLICY: Final[int]
+    EPROCLIM: Final[int]
+    EPROCUNAVAIL: Final[int]
+    EPROGMISMATCH: Final[int]
+    EPROGUNAVAIL: Final[int]
+    EPWROFF: Final[int]
+    ERPCMISMATCH: Final[int]
+    ESHLIBVERS: Final[int]
     if sys.version_info >= (3, 11):
-        EQFULL: int
+        EQFULL: Final[int]
 
 if sys.platform != "darwin":
-    EDEADLOCK: int
+    EDEADLOCK: Final[int]
 
 if sys.platform != "win32" and sys.platform != "darwin":
-    ECHRNG: int
-    EL2NSYNC: int
-    EL3HLT: int
-    EL3RST: int
-    ELNRNG: int
-    EUNATCH: int
-    ENOCSI: int
-    EL2HLT: int
-    EBADE: int
-    EBADR: int
-    EXFULL: int
-    ENOANO: int
-    EBADRQC: int
-    EBADSLT: int
-    EBFONT: int
-    ENONET: int
-    ENOPKG: int
-    EADV: int
-    ESRMNT: int
-    ECOMM: int
-    EDOTDOT: int
-    ENOTUNIQ: int
-    EBADFD: int
-    EREMCHG: int
-    ELIBACC: int
-    ELIBBAD: int
-    ELIBSCN: int
-    ELIBMAX: int
-    ELIBEXEC: int
-    ERESTART: int
-    ESTRPIPE: int
-    EUCLEAN: int
-    ENOTNAM: int
-    ENAVAIL: int
-    EISNAM: int
-    EREMOTEIO: int
+    ECHRNG: Final[int]
+    EL2NSYNC: Final[int]
+    EL3HLT: Final[int]
+    EL3RST: Final[int]
+    ELNRNG: Final[int]
+    EUNATCH: Final[int]
+    ENOCSI: Final[int]
+    EL2HLT: Final[int]
+    EBADE: Final[int]
+    EBADR: Final[int]
+    EXFULL: Final[int]
+    ENOANO: Final[int]
+    EBADRQC: Final[int]
+    EBADSLT: Final[int]
+    EBFONT: Final[int]
+    ENONET: Final[int]
+    ENOPKG: Final[int]
+    EADV: Final[int]
+    ESRMNT: Final[int]
+    ECOMM: Final[int]
+    EDOTDOT: Final[int]
+    ENOTUNIQ: Final[int]
+    EBADFD: Final[int]
+    EREMCHG: Final[int]
+    ELIBACC: Final[int]
+    ELIBBAD: Final[int]
+    ELIBSCN: Final[int]
+    ELIBMAX: Final[int]
+    ELIBEXEC: Final[int]
+    ERESTART: Final[int]
+    ESTRPIPE: Final[int]
+    EUCLEAN: Final[int]
+    ENOTNAM: Final[int]
+    ENAVAIL: Final[int]
+    EISNAM: Final[int]
+    EREMOTEIO: Final[int]
     # All of the below are undocumented
-    EKEYEXPIRED: int
-    EKEYREJECTED: int
-    EKEYREVOKED: int
-    EMEDIUMTYPE: int
-    ENOKEY: int
-    ENOMEDIUM: int
-    ERFKILL: int
+    EKEYEXPIRED: Final[int]
+    EKEYREJECTED: Final[int]
+    EKEYREVOKED: Final[int]
+    EMEDIUMTYPE: Final[int]
+    ENOKEY: Final[int]
+    ENOMEDIUM: Final[int]
+    ERFKILL: Final[int]
 
     if sys.version_info >= (3, 14):
-        EHWPOISON: int
+        EHWPOISON: Final[int]
 
 if sys.platform == "win32":
     # All of these are undocumented
-    WSABASEERR: int
-    WSAEACCES: int
-    WSAEADDRINUSE: int
-    WSAEADDRNOTAVAIL: int
-    WSAEAFNOSUPPORT: int
-    WSAEALREADY: int
-    WSAEBADF: int
-    WSAECONNABORTED: int
-    WSAECONNREFUSED: int
-    WSAECONNRESET: int
-    WSAEDESTADDRREQ: int
-    WSAEDISCON: int
-    WSAEDQUOT: int
-    WSAEFAULT: int
-    WSAEHOSTDOWN: int
-    WSAEHOSTUNREACH: int
-    WSAEINPROGRESS: int
-    WSAEINTR: int
-    WSAEINVAL: int
-    WSAEISCONN: int
-    WSAELOOP: int
-    WSAEMFILE: int
-    WSAEMSGSIZE: int
-    WSAENAMETOOLONG: int
-    WSAENETDOWN: int
-    WSAENETRESET: int
-    WSAENETUNREACH: int
-    WSAENOBUFS: int
-    WSAENOPROTOOPT: int
-    WSAENOTCONN: int
-    WSAENOTEMPTY: int
-    WSAENOTSOCK: int
-    WSAEOPNOTSUPP: int
-    WSAEPFNOSUPPORT: int
-    WSAEPROCLIM: int
-    WSAEPROTONOSUPPORT: int
-    WSAEPROTOTYPE: int
-    WSAEREMOTE: int
-    WSAESHUTDOWN: int
-    WSAESOCKTNOSUPPORT: int
-    WSAESTALE: int
-    WSAETIMEDOUT: int
-    WSAETOOMANYREFS: int
-    WSAEUSERS: int
-    WSAEWOULDBLOCK: int
-    WSANOTINITIALISED: int
-    WSASYSNOTREADY: int
-    WSAVERNOTSUPPORTED: int
+    WSABASEERR: Final[int]
+    WSAEACCES: Final[int]
+    WSAEADDRINUSE: Final[int]
+    WSAEADDRNOTAVAIL: Final[int]
+    WSAEAFNOSUPPORT: Final[int]
+    WSAEALREADY: Final[int]
+    WSAEBADF: Final[int]
+    WSAECONNABORTED: Final[int]
+    WSAECONNREFUSED: Final[int]
+    WSAECONNRESET: Final[int]
+    WSAEDESTADDRREQ: Final[int]
+    WSAEDISCON: Final[int]
+    WSAEDQUOT: Final[int]
+    WSAEFAULT: Final[int]
+    WSAEHOSTDOWN: Final[int]
+    WSAEHOSTUNREACH: Final[int]
+    WSAEINPROGRESS: Final[int]
+    WSAEINTR: Final[int]
+    WSAEINVAL: Final[int]
+    WSAEISCONN: Final[int]
+    WSAELOOP: Final[int]
+    WSAEMFILE: Final[int]
+    WSAEMSGSIZE: Final[int]
+    WSAENAMETOOLONG: Final[int]
+    WSAENETDOWN: Final[int]
+    WSAENETRESET: Final[int]
+    WSAENETUNREACH: Final[int]
+    WSAENOBUFS: Final[int]
+    WSAENOPROTOOPT: Final[int]
+    WSAENOTCONN: Final[int]
+    WSAENOTEMPTY: Final[int]
+    WSAENOTSOCK: Final[int]
+    WSAEOPNOTSUPP: Final[int]
+    WSAEPFNOSUPPORT: Final[int]
+    WSAEPROCLIM: Final[int]
+    WSAEPROTONOSUPPORT: Final[int]
+    WSAEPROTOTYPE: Final[int]
+    WSAEREMOTE: Final[int]
+    WSAESHUTDOWN: Final[int]
+    WSAESOCKTNOSUPPORT: Final[int]
+    WSAESTALE: Final[int]
+    WSAETIMEDOUT: Final[int]
+    WSAETOOMANYREFS: Final[int]
+    WSAEUSERS: Final[int]
+    WSAEWOULDBLOCK: Final[int]
+    WSANOTINITIALISED: Final[int]
+    WSASYSNOTREADY: Final[int]
+    WSAVERNOTSUPPORTED: Final[int]
diff --git a/mypy/typeshed/stdlib/fcntl.pyi b/mypy/typeshed/stdlib/fcntl.pyi
index 2fe64eb53201..5a3e89b0c676 100644
--- a/mypy/typeshed/stdlib/fcntl.pyi
+++ b/mypy/typeshed/stdlib/fcntl.pyi
@@ -4,107 +4,107 @@ from typing import Any, Final, Literal, overload
 from typing_extensions import Buffer
 
 if sys.platform != "win32":
-    FASYNC: int
-    FD_CLOEXEC: int
-    F_DUPFD: int
-    F_DUPFD_CLOEXEC: int
-    F_GETFD: int
-    F_GETFL: int
-    F_GETLK: int
-    F_GETOWN: int
-    F_RDLCK: int
-    F_SETFD: int
-    F_SETFL: int
-    F_SETLK: int
-    F_SETLKW: int
-    F_SETOWN: int
-    F_UNLCK: int
-    F_WRLCK: int
+    FASYNC: Final[int]
+    FD_CLOEXEC: Final[int]
+    F_DUPFD: Final[int]
+    F_DUPFD_CLOEXEC: Final[int]
+    F_GETFD: Final[int]
+    F_GETFL: Final[int]
+    F_GETLK: Final[int]
+    F_GETOWN: Final[int]
+    F_RDLCK: Final[int]
+    F_SETFD: Final[int]
+    F_SETFL: Final[int]
+    F_SETLK: Final[int]
+    F_SETLKW: Final[int]
+    F_SETOWN: Final[int]
+    F_UNLCK: Final[int]
+    F_WRLCK: Final[int]
 
-    F_GETLEASE: int
-    F_SETLEASE: int
+    F_GETLEASE: Final[int]
+    F_SETLEASE: Final[int]
     if sys.platform == "darwin":
-        F_FULLFSYNC: int
-        F_NOCACHE: int
-        F_GETPATH: int
+        F_FULLFSYNC: Final[int]
+        F_NOCACHE: Final[int]
+        F_GETPATH: Final[int]
     if sys.platform == "linux":
-        F_SETLKW64: int
-        F_SETSIG: int
-        F_SHLCK: int
-        F_SETLK64: int
-        F_GETSIG: int
-        F_NOTIFY: int
-        F_EXLCK: int
-        F_GETLK64: int
-        F_ADD_SEALS: int
-        F_GET_SEALS: int
-        F_SEAL_GROW: int
-        F_SEAL_SEAL: int
-        F_SEAL_SHRINK: int
-        F_SEAL_WRITE: int
+        F_SETLKW64: Final[int]
+        F_SETSIG: Final[int]
+        F_SHLCK: Final[int]
+        F_SETLK64: Final[int]
+        F_GETSIG: Final[int]
+        F_NOTIFY: Final[int]
+        F_EXLCK: Final[int]
+        F_GETLK64: Final[int]
+        F_ADD_SEALS: Final[int]
+        F_GET_SEALS: Final[int]
+        F_SEAL_GROW: Final[int]
+        F_SEAL_SEAL: Final[int]
+        F_SEAL_SHRINK: Final[int]
+        F_SEAL_WRITE: Final[int]
         F_OFD_GETLK: Final[int]
         F_OFD_SETLK: Final[int]
         F_OFD_SETLKW: Final[int]
 
         if sys.version_info >= (3, 10):
-            F_GETPIPE_SZ: int
-            F_SETPIPE_SZ: int
+            F_GETPIPE_SZ: Final[int]
+            F_SETPIPE_SZ: Final[int]
 
-        DN_ACCESS: int
-        DN_ATTRIB: int
-        DN_CREATE: int
-        DN_DELETE: int
-        DN_MODIFY: int
-        DN_MULTISHOT: int
-        DN_RENAME: int
+        DN_ACCESS: Final[int]
+        DN_ATTRIB: Final[int]
+        DN_CREATE: Final[int]
+        DN_DELETE: Final[int]
+        DN_MODIFY: Final[int]
+        DN_MULTISHOT: Final[int]
+        DN_RENAME: Final[int]
 
-    LOCK_EX: int
-    LOCK_NB: int
-    LOCK_SH: int
-    LOCK_UN: int
+    LOCK_EX: Final[int]
+    LOCK_NB: Final[int]
+    LOCK_SH: Final[int]
+    LOCK_UN: Final[int]
     if sys.platform == "linux":
-        LOCK_MAND: int
-        LOCK_READ: int
-        LOCK_RW: int
-        LOCK_WRITE: int
+        LOCK_MAND: Final[int]
+        LOCK_READ: Final[int]
+        LOCK_RW: Final[int]
+        LOCK_WRITE: Final[int]
 
     if sys.platform == "linux":
         # Constants for the POSIX STREAMS interface. Present in glibc until 2.29 (released February 2019).
         # Never implemented on BSD, and considered "obsolescent" starting in POSIX 2008.
         # Probably still used on Solaris.
-        I_ATMARK: int
-        I_CANPUT: int
-        I_CKBAND: int
-        I_FDINSERT: int
-        I_FIND: int
-        I_FLUSH: int
-        I_FLUSHBAND: int
-        I_GETBAND: int
-        I_GETCLTIME: int
-        I_GETSIG: int
-        I_GRDOPT: int
-        I_GWROPT: int
-        I_LINK: int
-        I_LIST: int
-        I_LOOK: int
-        I_NREAD: int
-        I_PEEK: int
-        I_PLINK: int
-        I_POP: int
-        I_PUNLINK: int
-        I_PUSH: int
-        I_RECVFD: int
-        I_SENDFD: int
-        I_SETCLTIME: int
-        I_SETSIG: int
-        I_SRDOPT: int
-        I_STR: int
-        I_SWROPT: int
-        I_UNLINK: int
+        I_ATMARK: Final[int]
+        I_CANPUT: Final[int]
+        I_CKBAND: Final[int]
+        I_FDINSERT: Final[int]
+        I_FIND: Final[int]
+        I_FLUSH: Final[int]
+        I_FLUSHBAND: Final[int]
+        I_GETBAND: Final[int]
+        I_GETCLTIME: Final[int]
+        I_GETSIG: Final[int]
+        I_GRDOPT: Final[int]
+        I_GWROPT: Final[int]
+        I_LINK: Final[int]
+        I_LIST: Final[int]
+        I_LOOK: Final[int]
+        I_NREAD: Final[int]
+        I_PEEK: Final[int]
+        I_PLINK: Final[int]
+        I_POP: Final[int]
+        I_PUNLINK: Final[int]
+        I_PUSH: Final[int]
+        I_RECVFD: Final[int]
+        I_SENDFD: Final[int]
+        I_SETCLTIME: Final[int]
+        I_SETSIG: Final[int]
+        I_SRDOPT: Final[int]
+        I_STR: Final[int]
+        I_SWROPT: Final[int]
+        I_UNLINK: Final[int]
 
     if sys.version_info >= (3, 12) and sys.platform == "linux":
-        FICLONE: int
-        FICLONERANGE: int
+        FICLONE: Final[int]
+        FICLONERANGE: Final[int]
 
     if sys.version_info >= (3, 13) and sys.platform == "linux":
         F_OWNER_TID: Final = 0
diff --git a/mypy/typeshed/stdlib/filecmp.pyi b/mypy/typeshed/stdlib/filecmp.pyi
index a2a2b235fdad..620cc177a415 100644
--- a/mypy/typeshed/stdlib/filecmp.pyi
+++ b/mypy/typeshed/stdlib/filecmp.pyi
@@ -6,7 +6,7 @@ from typing import Any, AnyStr, Final, Generic, Literal
 
 __all__ = ["clear_cache", "cmp", "dircmp", "cmpfiles", "DEFAULT_IGNORES"]
 
-DEFAULT_IGNORES: list[str]
+DEFAULT_IGNORES: Final[list[str]]
 BUFSIZE: Final = 8192
 
 def cmp(f1: StrOrBytesPath, f2: StrOrBytesPath, shallow: bool | Literal[0, 1] = True) -> bool: ...
diff --git a/mypy/typeshed/stdlib/fileinput.pyi b/mypy/typeshed/stdlib/fileinput.pyi
index 1d5f9cf00f36..eb942bc55177 100644
--- a/mypy/typeshed/stdlib/fileinput.pyi
+++ b/mypy/typeshed/stdlib/fileinput.pyi
@@ -2,7 +2,7 @@ import sys
 from _typeshed import AnyStr_co, StrOrBytesPath
 from collections.abc import Callable, Iterable, Iterator
 from types import GenericAlias, TracebackType
-from typing import IO, Any, AnyStr, Literal, Protocol, overload
+from typing import IO, Any, AnyStr, Literal, Protocol, overload, type_check_only
 from typing_extensions import Self, TypeAlias
 
 __all__ = [
@@ -25,6 +25,7 @@ if sys.version_info >= (3, 11):
 else:
     _TextMode: TypeAlias = Literal["r", "rU", "U"]
 
+@type_check_only
 class _HasReadlineAndFileno(Protocol[AnyStr_co]):
     def readline(self) -> AnyStr_co: ...
     def fileno(self) -> int: ...
diff --git a/mypy/typeshed/stdlib/fractions.pyi b/mypy/typeshed/stdlib/fractions.pyi
index 83592eb58336..ef4066aa65b5 100644
--- a/mypy/typeshed/stdlib/fractions.pyi
+++ b/mypy/typeshed/stdlib/fractions.pyi
@@ -2,17 +2,19 @@ import sys
 from collections.abc import Callable
 from decimal import Decimal
 from numbers import Rational, Real
-from typing import Any, Literal, Protocol, SupportsIndex, overload
+from typing import Any, Literal, Protocol, SupportsIndex, overload, type_check_only
 from typing_extensions import Self, TypeAlias
 
 _ComparableNum: TypeAlias = int | float | Decimal | Real
 
 __all__ = ["Fraction"]
 
+@type_check_only
 class _ConvertibleToIntegerRatio(Protocol):
     def as_integer_ratio(self) -> tuple[int | Rational, int | Rational]: ...
 
 class Fraction(Rational):
+    __slots__ = ("_numerator", "_denominator")
     @overload
     def __new__(cls, numerator: int | Rational = 0, denominator: int | Rational | None = None) -> Self: ...
     @overload
@@ -107,16 +109,31 @@ class Fraction(Rational):
     def __rdivmod__(a, b: int | Fraction) -> tuple[int, Fraction]: ...
     @overload
     def __rdivmod__(a, b: float) -> tuple[float, Fraction]: ...
-    @overload
-    def __pow__(a, b: int) -> Fraction: ...
-    @overload
-    def __pow__(a, b: float | Fraction) -> float: ...
-    @overload
-    def __pow__(a, b: complex) -> complex: ...
-    @overload
-    def __rpow__(b, a: float | Fraction) -> float: ...
-    @overload
-    def __rpow__(b, a: complex) -> complex: ...
+    if sys.version_info >= (3, 14):
+        @overload
+        def __pow__(a, b: int, modulo: None = None) -> Fraction: ...
+        @overload
+        def __pow__(a, b: float | Fraction, modulo: None = None) -> float: ...
+        @overload
+        def __pow__(a, b: complex, modulo: None = None) -> complex: ...
+    else:
+        @overload
+        def __pow__(a, b: int) -> Fraction: ...
+        @overload
+        def __pow__(a, b: float | Fraction) -> float: ...
+        @overload
+        def __pow__(a, b: complex) -> complex: ...
+    if sys.version_info >= (3, 14):
+        @overload
+        def __rpow__(b, a: float | Fraction, modulo: None = None) -> float: ...
+        @overload
+        def __rpow__(b, a: complex, modulo: None = None) -> complex: ...
+    else:
+        @overload
+        def __rpow__(b, a: float | Fraction) -> float: ...
+        @overload
+        def __rpow__(b, a: complex) -> complex: ...
+
     def __pos__(a) -> Fraction: ...
     def __neg__(a) -> Fraction: ...
     def __abs__(a) -> Fraction: ...
diff --git a/mypy/typeshed/stdlib/functools.pyi b/mypy/typeshed/stdlib/functools.pyi
index e31399fb8705..47baf917294d 100644
--- a/mypy/typeshed/stdlib/functools.pyi
+++ b/mypy/typeshed/stdlib/functools.pyi
@@ -3,8 +3,8 @@ import types
 from _typeshed import SupportsAllComparisons, SupportsItems
 from collections.abc import Callable, Hashable, Iterable, Sized
 from types import GenericAlias
-from typing import Any, Final, Generic, Literal, NamedTuple, TypedDict, TypeVar, final, overload
-from typing_extensions import ParamSpec, Self, TypeAlias
+from typing import Any, Final, Generic, Literal, NamedTuple, TypedDict, TypeVar, final, overload, type_check_only
+from typing_extensions import ParamSpec, Self, TypeAlias, disjoint_base
 
 __all__ = [
     "update_wrapper",
@@ -48,6 +48,7 @@ class _CacheInfo(NamedTuple):
     maxsize: int | None
     currsize: int
 
+@type_check_only
 class _CacheParameters(TypedDict):
     maxsize: int
     typed: bool
@@ -94,8 +95,9 @@ else:
         tuple[Literal["__module__"], Literal["__name__"], Literal["__qualname__"], Literal["__doc__"], Literal["__annotations__"]]
     ]
 
-WRAPPER_UPDATES: tuple[Literal["__dict__"]]
+WRAPPER_UPDATES: Final[tuple[Literal["__dict__"]]]
 
+@type_check_only
 class _Wrapped(Generic[_PWrapped, _RWrapped, _PWrapper, _RWrapper]):
     __wrapped__: Callable[_PWrapped, _RWrapped]
     def __call__(self, *args: _PWrapper.args, **kwargs: _PWrapper.kwargs) -> _RWrapper: ...
@@ -103,6 +105,7 @@ class _Wrapped(Generic[_PWrapped, _RWrapped, _PWrapper, _RWrapper]):
     __name__: str
     __qualname__: str
 
+@type_check_only
 class _Wrapper(Generic[_PWrapped, _RWrapped]):
     def __call__(self, f: Callable[_PWrapper, _RWrapper]) -> _Wrapped[_PWrapped, _RWrapped, _PWrapper, _RWrapper]: ...
 
@@ -147,7 +150,7 @@ else:
 
 def total_ordering(cls: type[_T]) -> type[_T]: ...
 def cmp_to_key(mycmp: Callable[[_T, _T], int]) -> Callable[[_T], SupportsAllComparisons]: ...
-
+@disjoint_base
 class partial(Generic[_T]):
     @property
     def func(self) -> Callable[..., _T]: ...
@@ -166,10 +169,17 @@ class partialmethod(Generic[_T]):
     func: Callable[..., _T] | _Descriptor
     args: tuple[Any, ...]
     keywords: dict[str, Any]
-    @overload
-    def __init__(self, func: Callable[..., _T], /, *args: Any, **keywords: Any) -> None: ...
-    @overload
-    def __init__(self, func: _Descriptor, /, *args: Any, **keywords: Any) -> None: ...
+    if sys.version_info >= (3, 14):
+        @overload
+        def __new__(self, func: Callable[..., _T], /, *args: Any, **keywords: Any) -> Self: ...
+        @overload
+        def __new__(self, func: _Descriptor, /, *args: Any, **keywords: Any) -> Self: ...
+    else:
+        @overload
+        def __init__(self, func: Callable[..., _T], /, *args: Any, **keywords: Any) -> None: ...
+        @overload
+        def __init__(self, func: _Descriptor, /, *args: Any, **keywords: Any) -> None: ...
+
     def __get__(self, obj: Any, cls: type[Any] | None = None) -> Callable[..., _T]: ...
     @property
     def __isabstractmethod__(self) -> bool: ...
@@ -180,6 +190,7 @@ if sys.version_info >= (3, 11):
 else:
     _RegType: TypeAlias = type[Any]
 
+@type_check_only
 class _SingleDispatchCallable(Generic[_T]):
     registry: types.MappingProxyType[Any, Callable[..., _T]]
     def dispatch(self, cls: Any) -> Callable[..., _T]: ...
diff --git a/mypy/typeshed/stdlib/genericpath.pyi b/mypy/typeshed/stdlib/genericpath.pyi
index 9d87c48fd520..3caed77a661a 100644
--- a/mypy/typeshed/stdlib/genericpath.pyi
+++ b/mypy/typeshed/stdlib/genericpath.pyi
@@ -2,7 +2,7 @@ import os
 import sys
 from _typeshed import BytesPath, FileDescriptorOrPath, StrOrBytesPath, StrPath, SupportsRichComparisonT
 from collections.abc import Sequence
-from typing import Literal, overload
+from typing import Literal, NewType, overload
 from typing_extensions import LiteralString
 
 __all__ = [
@@ -17,6 +17,7 @@ __all__ = [
     "samefile",
     "sameopenfile",
     "samestat",
+    "ALLOW_MISSING",
 ]
 if sys.version_info >= (3, 12):
     __all__ += ["islink"]
@@ -57,3 +58,7 @@ if sys.version_info >= (3, 13):
     def isjunction(path: StrOrBytesPath) -> bool: ...
     def isdevdrive(path: StrOrBytesPath) -> bool: ...
     def lexists(path: StrOrBytesPath) -> bool: ...
+
+# Added in Python 3.9.23, 3.10.18, 3.11.13, 3.12.11, 3.13.4
+_AllowMissingType = NewType("_AllowMissingType", object)
+ALLOW_MISSING: _AllowMissingType
diff --git a/mypy/typeshed/stdlib/gettext.pyi b/mypy/typeshed/stdlib/gettext.pyi
index d8fd92a00e13..e9ffd7a4a4a4 100644
--- a/mypy/typeshed/stdlib/gettext.pyi
+++ b/mypy/typeshed/stdlib/gettext.pyi
@@ -2,7 +2,8 @@ import io
 import sys
 from _typeshed import StrPath
 from collections.abc import Callable, Container, Iterable, Sequence
-from typing import Any, Final, Literal, Protocol, TypeVar, overload
+from typing import Any, Final, Literal, Protocol, TypeVar, overload, type_check_only
+from typing_extensions import deprecated
 
 __all__ = [
     "NullTranslations",
@@ -26,6 +27,7 @@ __all__ = [
 if sys.version_info < (3, 11):
     __all__ += ["bind_textdomain_codeset", "ldgettext", "ldngettext", "lgettext", "lngettext"]
 
+@type_check_only
 class _TranslationsReader(Protocol):
     def read(self) -> bytes: ...
     # optional:
@@ -42,9 +44,13 @@ class NullTranslations:
     def info(self) -> dict[str, str]: ...
     def charset(self) -> str | None: ...
     if sys.version_info < (3, 11):
+        @deprecated("Deprecated since Python 3.8; removed in Python 3.11.")
         def output_charset(self) -> str | None: ...
+        @deprecated("Deprecated since Python 3.8; removed in Python 3.11.")
         def set_output_charset(self, charset: str) -> None: ...
+        @deprecated("Deprecated since Python 3.8; removed in Python 3.11. Use `gettext()` instead.")
         def lgettext(self, message: str) -> str: ...
+        @deprecated("Deprecated since Python 3.8; removed in Python 3.11. Use `ngettext()` instead.")
         def lngettext(self, msgid1: str, msgid2: str, n: int) -> str: ...
 
     def install(self, names: Container[str] | None = None) -> None: ...
@@ -114,7 +120,7 @@ else:
         languages: Iterable[str] | None = None,
         class_: None = None,
         fallback: Literal[False] = False,
-        codeset: str | None = None,
+        codeset: str | None = ...,
     ) -> GNUTranslations: ...
     @overload
     def translation(
@@ -124,7 +130,7 @@ else:
         *,
         class_: Callable[[io.BufferedReader], _NullTranslationsT],
         fallback: Literal[False] = False,
-        codeset: str | None = None,
+        codeset: str | None = ...,
     ) -> _NullTranslationsT: ...
     @overload
     def translation(
@@ -133,7 +139,7 @@ else:
         languages: Iterable[str] | None,
         class_: Callable[[io.BufferedReader], _NullTranslationsT],
         fallback: Literal[False] = False,
-        codeset: str | None = None,
+        codeset: str | None = ...,
     ) -> _NullTranslationsT: ...
     @overload
     def translation(
@@ -142,10 +148,17 @@ else:
         languages: Iterable[str] | None = None,
         class_: Callable[[io.BufferedReader], NullTranslations] | None = None,
         fallback: bool = False,
-        codeset: str | None = None,
+        codeset: str | None = ...,
     ) -> NullTranslations: ...
+    @overload
+    def install(domain: str, localedir: StrPath | None = None, names: Container[str] | None = None) -> None: ...
+    @overload
+    @deprecated("The `codeset` parameter is deprecated since Python 3.8; removed in Python 3.11.")
+    def install(domain: str, localedir: StrPath | None, codeset: str | None, /, names: Container[str] | None = None) -> None: ...
+    @overload
+    @deprecated("The `codeset` parameter is deprecated since Python 3.8; removed in Python 3.11.")
     def install(
-        domain: str, localedir: StrPath | None = None, codeset: str | None = None, names: Container[str] | None = None
+        domain: str, localedir: StrPath | None = None, *, codeset: str | None, names: Container[str] | None = None
     ) -> None: ...
 
 def textdomain(domain: str | None = None) -> str: ...
@@ -160,10 +173,15 @@ def npgettext(context: str, msgid1: str, msgid2: str, n: int) -> str: ...
 def dnpgettext(domain: str, context: str, msgid1: str, msgid2: str, n: int) -> str: ...
 
 if sys.version_info < (3, 11):
+    @deprecated("Deprecated since Python 3.8; removed in Python 3.11. Use `gettext()` instead.")
     def lgettext(message: str) -> str: ...
+    @deprecated("Deprecated since Python 3.8; removed in Python 3.11. Use `dgettext()` instead.")
     def ldgettext(domain: str, message: str) -> str: ...
+    @deprecated("Deprecated since Python 3.8; removed in Python 3.11. Use `ngettext()` instead.")
     def lngettext(msgid1: str, msgid2: str, n: int) -> str: ...
+    @deprecated("Deprecated since Python 3.8; removed in Python 3.11. Use `dngettext()` instead.")
     def ldngettext(domain: str, msgid1: str, msgid2: str, n: int) -> str: ...
+    @deprecated("Deprecated since Python 3.8; removed in Python 3.11. Use `bindtextdomain()` instead.")
     def bind_textdomain_codeset(domain: str, codeset: str | None = None) -> str: ...
 
 Catalog = translation
diff --git a/mypy/typeshed/stdlib/glob.pyi b/mypy/typeshed/stdlib/glob.pyi
index 03cb5418e256..942fd7396196 100644
--- a/mypy/typeshed/stdlib/glob.pyi
+++ b/mypy/typeshed/stdlib/glob.pyi
@@ -2,14 +2,26 @@ import sys
 from _typeshed import StrOrBytesPath
 from collections.abc import Iterator, Sequence
 from typing import AnyStr
+from typing_extensions import deprecated
 
 __all__ = ["escape", "glob", "iglob"]
 
 if sys.version_info >= (3, 13):
     __all__ += ["translate"]
 
-def glob0(dirname: AnyStr, pattern: AnyStr) -> list[AnyStr]: ...
-def glob1(dirname: AnyStr, pattern: AnyStr) -> list[AnyStr]: ...
+if sys.version_info >= (3, 10):
+    @deprecated(
+        "Deprecated since Python 3.10; will be removed in Python 3.15. Use `glob.glob()` with the *root_dir* argument instead."
+    )
+    def glob0(dirname: AnyStr, pattern: AnyStr) -> list[AnyStr]: ...
+    @deprecated(
+        "Deprecated since Python 3.10; will be removed in Python 3.15. Use `glob.glob()` with the *root_dir* argument instead."
+    )
+    def glob1(dirname: AnyStr, pattern: AnyStr) -> list[AnyStr]: ...
+
+else:
+    def glob0(dirname: AnyStr, pattern: AnyStr) -> list[AnyStr]: ...
+    def glob1(dirname: AnyStr, pattern: AnyStr) -> list[AnyStr]: ...
 
 if sys.version_info >= (3, 11):
     def glob(
diff --git a/mypy/typeshed/stdlib/gzip.pyi b/mypy/typeshed/stdlib/gzip.pyi
index 883456b1ddc3..b18f76f06e3e 100644
--- a/mypy/typeshed/stdlib/gzip.pyi
+++ b/mypy/typeshed/stdlib/gzip.pyi
@@ -1,9 +1,9 @@
 import sys
 import zlib
-from _typeshed import ReadableBuffer, SizedBuffer, StrOrBytesPath
+from _typeshed import ReadableBuffer, SizedBuffer, StrOrBytesPath, WriteableBuffer
 from io import FileIO, TextIOWrapper
-from typing import Final, Literal, Protocol, overload
-from typing_extensions import TypeAlias
+from typing import Final, Literal, Protocol, overload, type_check_only
+from typing_extensions import TypeAlias, deprecated
 
 if sys.version_info >= (3, 14):
     from compression._common._streams import BaseStream, DecompressReader
@@ -25,6 +25,7 @@ FEXTRA: Final[int]  # actually Literal[4] # undocumented
 FNAME: Final[int]  # actually Literal[8] # undocumented
 FCOMMENT: Final[int]  # actually Literal[16] # undocumented
 
+@type_check_only
 class _ReadableFileobj(Protocol):
     def read(self, n: int, /) -> bytes: ...
     def seek(self, n: int, /) -> object: ...
@@ -33,6 +34,7 @@ class _ReadableFileobj(Protocol):
     # mode: str
     # def fileno() -> int: ...
 
+@type_check_only
 class _WritableFileobj(Protocol):
     def write(self, b: bytes, /) -> object: ...
     def flush(self) -> object: ...
@@ -141,6 +143,7 @@ class GzipFile(BaseStream):
     ) -> None: ...
     if sys.version_info < (3, 12):
         @property
+        @deprecated("Deprecated since Python 2.6; removed in Python 3.12. Use `name` attribute instead.")
         def filename(self) -> str: ...
 
     @property
@@ -157,8 +160,17 @@ class GzipFile(BaseStream):
     def seek(self, offset: int, whence: int = 0) -> int: ...
     def readline(self, size: int | None = -1) -> bytes: ...
 
+    if sys.version_info >= (3, 14):
+        def readinto(self, b: WriteableBuffer) -> int: ...
+        def readinto1(self, b: WriteableBuffer) -> int: ...
+
 class _GzipReader(DecompressReader):
     def __init__(self, fp: _ReadableFileobj) -> None: ...
 
-def compress(data: SizedBuffer, compresslevel: int = 9, *, mtime: float | None = None) -> bytes: ...
+if sys.version_info >= (3, 14):
+    def compress(data: SizedBuffer, compresslevel: int = 9, *, mtime: float = 0) -> bytes: ...
+
+else:
+    def compress(data: SizedBuffer, compresslevel: int = 9, *, mtime: float | None = None) -> bytes: ...
+
 def decompress(data: ReadableBuffer) -> bytes: ...
diff --git a/mypy/typeshed/stdlib/hashlib.pyi b/mypy/typeshed/stdlib/hashlib.pyi
index b32c0e992574..924136301b21 100644
--- a/mypy/typeshed/stdlib/hashlib.pyi
+++ b/mypy/typeshed/stdlib/hashlib.pyi
@@ -20,7 +20,7 @@ from _hashlib import (
 )
 from _typeshed import ReadableBuffer
 from collections.abc import Callable, Set as AbstractSet
-from typing import Protocol
+from typing import Protocol, type_check_only
 
 if sys.version_info >= (3, 11):
     __all__ = (
@@ -72,9 +72,11 @@ algorithms_guaranteed: AbstractSet[str]
 algorithms_available: AbstractSet[str]
 
 if sys.version_info >= (3, 11):
+    @type_check_only
     class _BytesIOLike(Protocol):
         def getbuffer(self) -> ReadableBuffer: ...
 
+    @type_check_only
     class _FileDigestFileObj(Protocol):
         def readinto(self, buf: bytearray, /) -> int: ...
         def readable(self) -> bool: ...
diff --git a/mypy/typeshed/stdlib/hmac.pyi b/mypy/typeshed/stdlib/hmac.pyi
index 300ed9eb26d8..070c59b1c166 100644
--- a/mypy/typeshed/stdlib/hmac.pyi
+++ b/mypy/typeshed/stdlib/hmac.pyi
@@ -20,6 +20,7 @@ def new(key: bytes | bytearray, msg: ReadableBuffer | None, digestmod: _DigestMo
 def new(key: bytes | bytearray, *, digestmod: _DigestMod) -> HMAC: ...
 
 class HMAC:
+    __slots__ = ("_hmac", "_inner", "_outer", "block_size", "digest_size")
     digest_size: int
     block_size: int
     @property
diff --git a/mypy/typeshed/stdlib/html/entities.pyi b/mypy/typeshed/stdlib/html/entities.pyi
index be83fd1135be..e5890d1ecfbd 100644
--- a/mypy/typeshed/stdlib/html/entities.pyi
+++ b/mypy/typeshed/stdlib/html/entities.pyi
@@ -1,6 +1,8 @@
+from typing import Final
+
 __all__ = ["html5", "name2codepoint", "codepoint2name", "entitydefs"]
 
-name2codepoint: dict[str, int]
-html5: dict[str, str]
-codepoint2name: dict[int, str]
-entitydefs: dict[str, str]
+name2codepoint: Final[dict[str, int]]
+html5: Final[dict[str, str]]
+codepoint2name: Final[dict[int, str]]
+entitydefs: Final[dict[str, str]]
diff --git a/mypy/typeshed/stdlib/html/parser.pyi b/mypy/typeshed/stdlib/html/parser.pyi
index d322ade965d9..8b3fce0010b7 100644
--- a/mypy/typeshed/stdlib/html/parser.pyi
+++ b/mypy/typeshed/stdlib/html/parser.pyi
@@ -1,9 +1,16 @@
+import sys
 from _markupbase import ParserBase
 from re import Pattern
+from typing import Final
 
 __all__ = ["HTMLParser"]
 
 class HTMLParser(ParserBase):
+    CDATA_CONTENT_ELEMENTS: Final[tuple[str, ...]]
+    if sys.version_info >= (3, 13):
+        # Added in 3.13.6
+        RCDATA_CONTENT_ELEMENTS: Final[tuple[str, ...]]
+
     def __init__(self, *, convert_charrefs: bool = True) -> None: ...
     def feed(self, data: str) -> None: ...
     def close(self) -> None: ...
@@ -17,16 +24,19 @@ class HTMLParser(ParserBase):
     def handle_comment(self, data: str) -> None: ...
     def handle_decl(self, decl: str) -> None: ...
     def handle_pi(self, data: str) -> None: ...
-    CDATA_CONTENT_ELEMENTS: tuple[str, ...]
     def check_for_whole_start_tag(self, i: int) -> int: ...  # undocumented
     def clear_cdata_mode(self) -> None: ...  # undocumented
     def goahead(self, end: bool) -> None: ...  # undocumented
-    def parse_bogus_comment(self, i: int, report: bool = ...) -> int: ...  # undocumented
+    def parse_bogus_comment(self, i: int, report: bool = True) -> int: ...  # undocumented
     def parse_endtag(self, i: int) -> int: ...  # undocumented
     def parse_html_declaration(self, i: int) -> int: ...  # undocumented
     def parse_pi(self, i: int) -> int: ...  # undocumented
     def parse_starttag(self, i: int) -> int: ...  # undocumented
-    def set_cdata_mode(self, elem: str) -> None: ...  # undocumented
+    if sys.version_info >= (3, 13):
+        # `escapable` parameter added in 3.13.6
+        def set_cdata_mode(self, elem: str, *, escapable: bool = False) -> None: ...  # undocumented
+    else:
+        def set_cdata_mode(self, elem: str) -> None: ...  # undocumented
     rawdata: str  # undocumented
     cdata_elem: str | None  # undocumented
     convert_charrefs: bool  # undocumented
diff --git a/mypy/typeshed/stdlib/http/client.pyi b/mypy/typeshed/stdlib/http/client.pyi
index 5c35dff28d43..d259e84e6f2a 100644
--- a/mypy/typeshed/stdlib/http/client.pyi
+++ b/mypy/typeshed/stdlib/http/client.pyi
@@ -7,7 +7,7 @@ from _typeshed import MaybeNone, ReadableBuffer, SupportsRead, SupportsReadline,
 from collections.abc import Callable, Iterable, Iterator, Mapping
 from email._policybase import _MessageT
 from socket import socket
-from typing import BinaryIO, Literal, TypeVar, overload
+from typing import BinaryIO, Final, TypeVar, overload
 from typing_extensions import Self, TypeAlias
 
 __all__ = [
@@ -36,85 +36,85 @@ _DataType: TypeAlias = SupportsRead[bytes] | Iterable[ReadableBuffer] | Readable
 _T = TypeVar("_T")
 _HeaderValue: TypeAlias = ReadableBuffer | str | int
 
-HTTP_PORT: int
-HTTPS_PORT: int
+HTTP_PORT: Final = 80
+HTTPS_PORT: Final = 443
 
 # Keep these global constants in sync with http.HTTPStatus (http/__init__.pyi).
 # They are present for backward compatibility reasons.
-CONTINUE: Literal[100]
-SWITCHING_PROTOCOLS: Literal[101]
-PROCESSING: Literal[102]
-EARLY_HINTS: Literal[103]
+CONTINUE: Final = 100
+SWITCHING_PROTOCOLS: Final = 101
+PROCESSING: Final = 102
+EARLY_HINTS: Final = 103
 
-OK: Literal[200]
-CREATED: Literal[201]
-ACCEPTED: Literal[202]
-NON_AUTHORITATIVE_INFORMATION: Literal[203]
-NO_CONTENT: Literal[204]
-RESET_CONTENT: Literal[205]
-PARTIAL_CONTENT: Literal[206]
-MULTI_STATUS: Literal[207]
-ALREADY_REPORTED: Literal[208]
-IM_USED: Literal[226]
+OK: Final = 200
+CREATED: Final = 201
+ACCEPTED: Final = 202
+NON_AUTHORITATIVE_INFORMATION: Final = 203
+NO_CONTENT: Final = 204
+RESET_CONTENT: Final = 205
+PARTIAL_CONTENT: Final = 206
+MULTI_STATUS: Final = 207
+ALREADY_REPORTED: Final = 208
+IM_USED: Final = 226
 
-MULTIPLE_CHOICES: Literal[300]
-MOVED_PERMANENTLY: Literal[301]
-FOUND: Literal[302]
-SEE_OTHER: Literal[303]
-NOT_MODIFIED: Literal[304]
-USE_PROXY: Literal[305]
-TEMPORARY_REDIRECT: Literal[307]
-PERMANENT_REDIRECT: Literal[308]
+MULTIPLE_CHOICES: Final = 300
+MOVED_PERMANENTLY: Final = 301
+FOUND: Final = 302
+SEE_OTHER: Final = 303
+NOT_MODIFIED: Final = 304
+USE_PROXY: Final = 305
+TEMPORARY_REDIRECT: Final = 307
+PERMANENT_REDIRECT: Final = 308
 
-BAD_REQUEST: Literal[400]
-UNAUTHORIZED: Literal[401]
-PAYMENT_REQUIRED: Literal[402]
-FORBIDDEN: Literal[403]
-NOT_FOUND: Literal[404]
-METHOD_NOT_ALLOWED: Literal[405]
-NOT_ACCEPTABLE: Literal[406]
-PROXY_AUTHENTICATION_REQUIRED: Literal[407]
-REQUEST_TIMEOUT: Literal[408]
-CONFLICT: Literal[409]
-GONE: Literal[410]
-LENGTH_REQUIRED: Literal[411]
-PRECONDITION_FAILED: Literal[412]
+BAD_REQUEST: Final = 400
+UNAUTHORIZED: Final = 401
+PAYMENT_REQUIRED: Final = 402
+FORBIDDEN: Final = 403
+NOT_FOUND: Final = 404
+METHOD_NOT_ALLOWED: Final = 405
+NOT_ACCEPTABLE: Final = 406
+PROXY_AUTHENTICATION_REQUIRED: Final = 407
+REQUEST_TIMEOUT: Final = 408
+CONFLICT: Final = 409
+GONE: Final = 410
+LENGTH_REQUIRED: Final = 411
+PRECONDITION_FAILED: Final = 412
 if sys.version_info >= (3, 13):
-    CONTENT_TOO_LARGE: Literal[413]
-REQUEST_ENTITY_TOO_LARGE: Literal[413]
+    CONTENT_TOO_LARGE: Final = 413
+REQUEST_ENTITY_TOO_LARGE: Final = 413
 if sys.version_info >= (3, 13):
-    URI_TOO_LONG: Literal[414]
-REQUEST_URI_TOO_LONG: Literal[414]
-UNSUPPORTED_MEDIA_TYPE: Literal[415]
+    URI_TOO_LONG: Final = 414
+REQUEST_URI_TOO_LONG: Final = 414
+UNSUPPORTED_MEDIA_TYPE: Final = 415
 if sys.version_info >= (3, 13):
-    RANGE_NOT_SATISFIABLE: Literal[416]
-REQUESTED_RANGE_NOT_SATISFIABLE: Literal[416]
-EXPECTATION_FAILED: Literal[417]
-IM_A_TEAPOT: Literal[418]
-MISDIRECTED_REQUEST: Literal[421]
+    RANGE_NOT_SATISFIABLE: Final = 416
+REQUESTED_RANGE_NOT_SATISFIABLE: Final = 416
+EXPECTATION_FAILED: Final = 417
+IM_A_TEAPOT: Final = 418
+MISDIRECTED_REQUEST: Final = 421
 if sys.version_info >= (3, 13):
-    UNPROCESSABLE_CONTENT: Literal[422]
-UNPROCESSABLE_ENTITY: Literal[422]
-LOCKED: Literal[423]
-FAILED_DEPENDENCY: Literal[424]
-TOO_EARLY: Literal[425]
-UPGRADE_REQUIRED: Literal[426]
-PRECONDITION_REQUIRED: Literal[428]
-TOO_MANY_REQUESTS: Literal[429]
-REQUEST_HEADER_FIELDS_TOO_LARGE: Literal[431]
-UNAVAILABLE_FOR_LEGAL_REASONS: Literal[451]
+    UNPROCESSABLE_CONTENT: Final = 422
+UNPROCESSABLE_ENTITY: Final = 422
+LOCKED: Final = 423
+FAILED_DEPENDENCY: Final = 424
+TOO_EARLY: Final = 425
+UPGRADE_REQUIRED: Final = 426
+PRECONDITION_REQUIRED: Final = 428
+TOO_MANY_REQUESTS: Final = 429
+REQUEST_HEADER_FIELDS_TOO_LARGE: Final = 431
+UNAVAILABLE_FOR_LEGAL_REASONS: Final = 451
 
-INTERNAL_SERVER_ERROR: Literal[500]
-NOT_IMPLEMENTED: Literal[501]
-BAD_GATEWAY: Literal[502]
-SERVICE_UNAVAILABLE: Literal[503]
-GATEWAY_TIMEOUT: Literal[504]
-HTTP_VERSION_NOT_SUPPORTED: Literal[505]
-VARIANT_ALSO_NEGOTIATES: Literal[506]
-INSUFFICIENT_STORAGE: Literal[507]
-LOOP_DETECTED: Literal[508]
-NOT_EXTENDED: Literal[510]
-NETWORK_AUTHENTICATION_REQUIRED: Literal[511]
+INTERNAL_SERVER_ERROR: Final = 500
+NOT_IMPLEMENTED: Final = 501
+BAD_GATEWAY: Final = 502
+SERVICE_UNAVAILABLE: Final = 503
+GATEWAY_TIMEOUT: Final = 504
+HTTP_VERSION_NOT_SUPPORTED: Final = 505
+VARIANT_ALSO_NEGOTIATES: Final = 506
+INSUFFICIENT_STORAGE: Final = 507
+LOOP_DETECTED: Final = 508
+NOT_EXTENDED: Final = 510
+NETWORK_AUTHENTICATION_REQUIRED: Final = 511
 
 responses: dict[int, str]
 
diff --git a/mypy/typeshed/stdlib/http/server.pyi b/mypy/typeshed/stdlib/http/server.pyi
index 429bb65bb0ef..2c1a374331bc 100644
--- a/mypy/typeshed/stdlib/http/server.pyi
+++ b/mypy/typeshed/stdlib/http/server.pyi
@@ -119,12 +119,24 @@ class SimpleHTTPRequestHandler(BaseHTTPRequestHandler):
     def guess_type(self, path: StrPath) -> str: ...  # undocumented
 
 def executable(path: StrPath) -> bool: ...  # undocumented
-@deprecated("Deprecated in Python 3.13; removal scheduled for Python 3.15")
-class CGIHTTPRequestHandler(SimpleHTTPRequestHandler):
-    cgi_directories: list[str]
-    have_fork: bool  # undocumented
-    def do_POST(self) -> None: ...
-    def is_cgi(self) -> bool: ...  # undocumented
-    def is_executable(self, path: StrPath) -> bool: ...  # undocumented
-    def is_python(self, path: StrPath) -> bool: ...  # undocumented
-    def run_cgi(self) -> None: ...  # undocumented
+
+if sys.version_info >= (3, 13):
+    @deprecated("Deprecated since Python 3.13; will be removed in Python 3.15.")
+    class CGIHTTPRequestHandler(SimpleHTTPRequestHandler):
+        cgi_directories: list[str]
+        have_fork: bool  # undocumented
+        def do_POST(self) -> None: ...
+        def is_cgi(self) -> bool: ...  # undocumented
+        def is_executable(self, path: StrPath) -> bool: ...  # undocumented
+        def is_python(self, path: StrPath) -> bool: ...  # undocumented
+        def run_cgi(self) -> None: ...  # undocumented
+
+else:
+    class CGIHTTPRequestHandler(SimpleHTTPRequestHandler):
+        cgi_directories: list[str]
+        have_fork: bool  # undocumented
+        def do_POST(self) -> None: ...
+        def is_cgi(self) -> bool: ...  # undocumented
+        def is_executable(self, path: StrPath) -> bool: ...  # undocumented
+        def is_python(self, path: StrPath) -> bool: ...  # undocumented
+        def run_cgi(self) -> None: ...  # undocumented
diff --git a/mypy/typeshed/stdlib/imghdr.pyi b/mypy/typeshed/stdlib/imghdr.pyi
index 6e1b858b8f32..e45ca3eb5bdb 100644
--- a/mypy/typeshed/stdlib/imghdr.pyi
+++ b/mypy/typeshed/stdlib/imghdr.pyi
@@ -1,9 +1,10 @@
 from _typeshed import StrPath
 from collections.abc import Callable
-from typing import Any, BinaryIO, Protocol, overload
+from typing import Any, BinaryIO, Protocol, overload, type_check_only
 
 __all__ = ["what"]
 
+@type_check_only
 class _ReadableBinary(Protocol):
     def tell(self) -> int: ...
     def read(self, size: int, /) -> bytes: ...
diff --git a/mypy/typeshed/stdlib/imp.pyi b/mypy/typeshed/stdlib/imp.pyi
index ee5a0cd7bc72..b5b4223aa58e 100644
--- a/mypy/typeshed/stdlib/imp.pyi
+++ b/mypy/typeshed/stdlib/imp.pyi
@@ -13,18 +13,18 @@ from _imp import (
 from _typeshed import StrPath
 from os import PathLike
 from types import TracebackType
-from typing import IO, Any, Protocol
+from typing import IO, Any, Final, Protocol, type_check_only
 
-SEARCH_ERROR: int
-PY_SOURCE: int
-PY_COMPILED: int
-C_EXTENSION: int
-PY_RESOURCE: int
-PKG_DIRECTORY: int
-C_BUILTIN: int
-PY_FROZEN: int
-PY_CODERESOURCE: int
-IMP_HOOK: int
+SEARCH_ERROR: Final = 0
+PY_SOURCE: Final = 1
+PY_COMPILED: Final = 2
+C_EXTENSION: Final = 3
+PY_RESOURCE: Final = 4
+PKG_DIRECTORY: Final = 5
+C_BUILTIN: Final = 6
+PY_FROZEN: Final = 7
+PY_CODERESOURCE: Final = 8
+IMP_HOOK: Final = 9
 
 def new_module(name: str) -> types.ModuleType: ...
 def get_magic() -> bytes: ...
@@ -39,6 +39,7 @@ class NullImporter:
 
 # Technically, a text file has to support a slightly different set of operations than a binary file,
 # but we ignore that here.
+@type_check_only
 class _FileLike(Protocol):
     closed: bool
     mode: str
diff --git a/mypy/typeshed/stdlib/importlib/__init__.pyi b/mypy/typeshed/stdlib/importlib/__init__.pyi
index cab81512e92f..d60f90adee19 100644
--- a/mypy/typeshed/stdlib/importlib/__init__.pyi
+++ b/mypy/typeshed/stdlib/importlib/__init__.pyi
@@ -2,6 +2,7 @@ import sys
 from importlib._bootstrap import __import__ as __import__
 from importlib.abc import Loader
 from types import ModuleType
+from typing_extensions import deprecated
 
 __all__ = ["__import__", "import_module", "invalidate_caches", "reload"]
 
@@ -9,6 +10,7 @@ __all__ = ["__import__", "import_module", "invalidate_caches", "reload"]
 def import_module(name: str, package: str | None = None) -> ModuleType: ...
 
 if sys.version_info < (3, 12):
+    @deprecated("Deprecated since Python 3.4; removed in Python 3.12. Use `importlib.util.find_spec()` instead.")
     def find_loader(name: str, path: str | None = None) -> Loader | None: ...
 
 def invalidate_caches() -> None: ...
diff --git a/mypy/typeshed/stdlib/importlib/_abc.pyi b/mypy/typeshed/stdlib/importlib/_abc.pyi
index 1a21b9a72cd8..90ab34021917 100644
--- a/mypy/typeshed/stdlib/importlib/_abc.pyi
+++ b/mypy/typeshed/stdlib/importlib/_abc.pyi
@@ -2,11 +2,16 @@ import sys
 import types
 from abc import ABCMeta
 from importlib.machinery import ModuleSpec
+from typing_extensions import deprecated
 
 if sys.version_info >= (3, 10):
     class Loader(metaclass=ABCMeta):
         def load_module(self, fullname: str) -> types.ModuleType: ...
         if sys.version_info < (3, 12):
+            @deprecated(
+                "Deprecated since Python 3.4; removed in Python 3.12. "
+                "The module spec is now used by the import machinery to generate a module repr."
+            )
             def module_repr(self, module: types.ModuleType) -> str: ...
 
         def create_module(self, spec: ModuleSpec) -> types.ModuleType | None: ...
diff --git a/mypy/typeshed/stdlib/importlib/abc.pyi b/mypy/typeshed/stdlib/importlib/abc.pyi
index cf0fd0807b7b..72031e0e3bd2 100644
--- a/mypy/typeshed/stdlib/importlib/abc.pyi
+++ b/mypy/typeshed/stdlib/importlib/abc.pyi
@@ -37,9 +37,10 @@ else:
         def exec_module(self, module: types.ModuleType) -> None: ...
 
 if sys.version_info < (3, 12):
+    @deprecated("Deprecated since Python 3.3; removed in Python 3.12. Use `MetaPathFinder` or `PathEntryFinder` instead.")
     class Finder(metaclass=ABCMeta): ...
 
-@deprecated("Deprecated as of Python 3.7: Use importlib.resources.abc.TraversableResources instead.")
+@deprecated("Deprecated since Python 3.7. Use `importlib.resources.abc.TraversableResources` instead.")
 class ResourceLoader(Loader):
     @abstractmethod
     def get_data(self, path: str) -> bytes: ...
@@ -60,7 +61,7 @@ class ExecutionLoader(InspectLoader):
     def get_filename(self, fullname: str) -> str: ...
 
 class SourceLoader(_bootstrap_external.SourceLoader, ResourceLoader, ExecutionLoader, metaclass=ABCMeta):  # type: ignore[misc]  # incompatible definitions of source_to_code in the base classes
-    @deprecated("Deprecated as of Python 3.3: Use importlib.resources.abc.SourceLoader.path_stats instead.")
+    @deprecated("Deprecated since Python 3.3. Use `importlib.resources.abc.SourceLoader.path_stats` instead.")
     def path_mtime(self, path: str) -> float: ...
     def set_data(self, path: str, data: bytes) -> None: ...
     def get_source(self, fullname: str) -> str | None: ...
@@ -71,6 +72,7 @@ if sys.version_info >= (3, 10):
     # Please keep in sync with _typeshed.importlib.MetaPathFinderProtocol
     class MetaPathFinder(metaclass=ABCMeta):
         if sys.version_info < (3, 12):
+            @deprecated("Deprecated since Python 3.4; removed in Python 3.12. Use `MetaPathFinder.find_spec()` instead.")
             def find_module(self, fullname: str, path: Sequence[str] | None) -> Loader | None: ...
 
         def invalidate_caches(self) -> None: ...
@@ -81,7 +83,9 @@ if sys.version_info >= (3, 10):
 
     class PathEntryFinder(metaclass=ABCMeta):
         if sys.version_info < (3, 12):
+            @deprecated("Deprecated since Python 3.4; removed in Python 3.12. Use `PathEntryFinder.find_spec()` instead.")
             def find_module(self, fullname: str) -> Loader | None: ...
+            @deprecated("Deprecated since Python 3.4; removed in Python 3.12. Use `find_spec()` instead.")
             def find_loader(self, fullname: str) -> tuple[Loader | None, Sequence[str]]: ...
 
         def invalidate_caches(self) -> None: ...
diff --git a/mypy/typeshed/stdlib/importlib/metadata/__init__.pyi b/mypy/typeshed/stdlib/importlib/metadata/__init__.pyi
index 15d8b50b09d2..9286e92331c8 100644
--- a/mypy/typeshed/stdlib/importlib/metadata/__init__.pyi
+++ b/mypy/typeshed/stdlib/importlib/metadata/__init__.pyi
@@ -11,7 +11,7 @@ from os import PathLike
 from pathlib import Path
 from re import Pattern
 from typing import Any, ClassVar, Generic, NamedTuple, TypeVar, overload
-from typing_extensions import Self, TypeAlias
+from typing_extensions import Self, TypeAlias, deprecated, disjoint_base
 
 _T = TypeVar("_T")
 _KT = TypeVar("_KT")
@@ -59,23 +59,21 @@ else:
         value: str
         group: str
 
-class EntryPoint(_EntryPointBase):
-    pattern: ClassVar[Pattern[str]]
-    if sys.version_info >= (3, 11):
+if sys.version_info >= (3, 11):
+    class EntryPoint(_EntryPointBase):
+        pattern: ClassVar[Pattern[str]]
         name: str
         value: str
         group: str
 
         def __init__(self, name: str, value: str, group: str) -> None: ...
-
-    def load(self) -> Any: ...  # Callable[[], Any] or an importable module
-    @property
-    def extras(self) -> list[str]: ...
-    @property
-    def module(self) -> str: ...
-    @property
-    def attr(self) -> str: ...
-    if sys.version_info >= (3, 10):
+        def load(self) -> Any: ...  # Callable[[], Any] or an importable module
+        @property
+        def extras(self) -> list[str]: ...
+        @property
+        def module(self) -> str: ...
+        @property
+        def attr(self) -> str: ...
         dist: ClassVar[Distribution | None]
         def matches(
             self,
@@ -87,16 +85,43 @@ class EntryPoint(_EntryPointBase):
             attr: str = ...,
             extras: list[str] = ...,
         ) -> bool: ...  # undocumented
-
-    def __hash__(self) -> int: ...
-    def __eq__(self, other: object) -> bool: ...
-    if sys.version_info >= (3, 11):
+        def __hash__(self) -> int: ...
+        def __eq__(self, other: object) -> bool: ...
         def __lt__(self, other: object) -> bool: ...
-    if sys.version_info < (3, 12):
+        if sys.version_info < (3, 12):
+            def __iter__(self) -> Iterator[Any]: ...  # result of iter((str, Self)), really
+
+else:
+    @disjoint_base
+    class EntryPoint(_EntryPointBase):
+        pattern: ClassVar[Pattern[str]]
+
+        def load(self) -> Any: ...  # Callable[[], Any] or an importable module
+        @property
+        def extras(self) -> list[str]: ...
+        @property
+        def module(self) -> str: ...
+        @property
+        def attr(self) -> str: ...
+        if sys.version_info >= (3, 10):
+            dist: ClassVar[Distribution | None]
+            def matches(
+                self,
+                *,
+                name: str = ...,
+                value: str = ...,
+                group: str = ...,
+                module: str = ...,
+                attr: str = ...,
+                extras: list[str] = ...,
+            ) -> bool: ...  # undocumented
+
+        def __hash__(self) -> int: ...
         def __iter__(self) -> Iterator[Any]: ...  # result of iter((str, Self)), really
 
 if sys.version_info >= (3, 12):
     class EntryPoints(tuple[EntryPoint, ...]):
+        __slots__ = ()
         def __getitem__(self, name: str) -> EntryPoint: ...  # type: ignore[override]
         def select(
             self,
@@ -114,10 +139,12 @@ if sys.version_info >= (3, 12):
         def groups(self) -> set[str]: ...
 
 elif sys.version_info >= (3, 10):
-    class DeprecatedList(list[_T]): ...
+    class DeprecatedList(list[_T]):
+        __slots__ = ()
 
     class EntryPoints(DeprecatedList[EntryPoint]):  # use as list is deprecated since 3.10
         # int argument is deprecated since 3.10
+        __slots__ = ()
         def __getitem__(self, name: int | str) -> EntryPoint: ...  # type: ignore[override]
         def select(
             self,
@@ -140,12 +167,15 @@ if sys.version_info >= (3, 10) and sys.version_info < (3, 12):
         @overload
         def get(self, name: _KT, default: None = None) -> _VT | None: ...
         @overload
+        def get(self, name: _KT, default: _VT) -> _VT: ...
+        @overload
         def get(self, name: _KT, default: _T) -> _VT | _T: ...
         def __iter__(self) -> Iterator[_KT]: ...
         def __contains__(self, *args: object) -> bool: ...
         def keys(self) -> dict_keys[_KT, _VT]: ...
         def values(self) -> dict_values[_KT, _VT]: ...
 
+    @deprecated("Deprecated since Python 3.10; removed in Python 3.12. Use `select` instead.")
     class SelectableGroups(Deprecated[str, EntryPoints], dict[str, EntryPoints]):  # use as dict is deprecated since 3.10
         @classmethod
         def load(cls, eps: Iterable[EntryPoint]) -> Self: ...
@@ -227,7 +257,7 @@ class Distribution(_distribution_parent):
         def name(self) -> str: ...
     if sys.version_info >= (3, 13):
         @property
-        def origin(self) -> types.SimpleNamespace: ...
+        def origin(self) -> types.SimpleNamespace | None: ...
 
 class DistributionFinder(MetaPathFinder):
     class Context:
diff --git a/mypy/typeshed/stdlib/importlib/resources/abc.pyi b/mypy/typeshed/stdlib/importlib/resources/abc.pyi
index fe0fe64dba0d..80d92a608604 100644
--- a/mypy/typeshed/stdlib/importlib/resources/abc.pyi
+++ b/mypy/typeshed/stdlib/importlib/resources/abc.pyi
@@ -10,13 +10,8 @@ if sys.version_info >= (3, 11):
         def open_resource(self, resource: str) -> IO[bytes]: ...
         @abstractmethod
         def resource_path(self, resource: str) -> str: ...
-        if sys.version_info >= (3, 10):
-            @abstractmethod
-            def is_resource(self, path: str) -> bool: ...
-        else:
-            @abstractmethod
-            def is_resource(self, name: str) -> bool: ...
-
+        @abstractmethod
+        def is_resource(self, path: str) -> bool: ...
         @abstractmethod
         def contents(self) -> Iterator[str]: ...
 
@@ -28,12 +23,8 @@ if sys.version_info >= (3, 11):
         def is_file(self) -> bool: ...
         @abstractmethod
         def iterdir(self) -> Iterator[Traversable]: ...
-        if sys.version_info >= (3, 11):
-            @abstractmethod
-            def joinpath(self, *descendants: str) -> Traversable: ...
-        else:
-            @abstractmethod
-            def joinpath(self, child: str, /) -> Traversable: ...
+        @abstractmethod
+        def joinpath(self, *descendants: str) -> Traversable: ...
 
         # The documentation and runtime protocol allows *args, **kwargs arguments,
         # but this would mean that all implementers would have to support them,
@@ -47,12 +38,7 @@ if sys.version_info >= (3, 11):
         @property
         @abstractmethod
         def name(self) -> str: ...
-        if sys.version_info >= (3, 10):
-            def __truediv__(self, child: str, /) -> Traversable: ...
-        else:
-            @abstractmethod
-            def __truediv__(self, child: str, /) -> Traversable: ...
-
+        def __truediv__(self, child: str, /) -> Traversable: ...
         @abstractmethod
         def read_bytes(self) -> bytes: ...
         @abstractmethod
diff --git a/mypy/typeshed/stdlib/importlib/util.pyi b/mypy/typeshed/stdlib/importlib/util.pyi
index 370a08623842..05c4d0d1edb3 100644
--- a/mypy/typeshed/stdlib/importlib/util.pyi
+++ b/mypy/typeshed/stdlib/importlib/util.pyi
@@ -12,13 +12,25 @@ from importlib._bootstrap_external import (
     spec_from_file_location as spec_from_file_location,
 )
 from importlib.abc import Loader
-from typing_extensions import ParamSpec
+from typing_extensions import ParamSpec, deprecated
 
 _P = ParamSpec("_P")
 
 if sys.version_info < (3, 12):
+    @deprecated(
+        "Deprecated since Python 3.4; removed in Python 3.12. "
+        "`__name__`, `__package__` and `__loader__` are now set automatically."
+    )
     def module_for_loader(fxn: Callable[_P, types.ModuleType]) -> Callable[_P, types.ModuleType]: ...
+    @deprecated(
+        "Deprecated since Python 3.4; removed in Python 3.12. "
+        "`__name__`, `__package__` and `__loader__` are now set automatically."
+    )
     def set_loader(fxn: Callable[_P, types.ModuleType]) -> Callable[_P, types.ModuleType]: ...
+    @deprecated(
+        "Deprecated since Python 3.4; removed in Python 3.12. "
+        "`__name__`, `__package__` and `__loader__` are now set automatically."
+    )
     def set_package(fxn: Callable[_P, types.ModuleType]) -> Callable[_P, types.ModuleType]: ...
 
 def resolve_name(name: str, package: str | None) -> str: ...
diff --git a/mypy/typeshed/stdlib/inspect.pyi b/mypy/typeshed/stdlib/inspect.pyi
index e19c2a634aa0..55ae61617af7 100644
--- a/mypy/typeshed/stdlib/inspect.pyi
+++ b/mypy/typeshed/stdlib/inspect.pyi
@@ -25,8 +25,8 @@ from types import (
     TracebackType,
     WrapperDescriptorType,
 )
-from typing import Any, ClassVar, Final, Literal, NamedTuple, Protocol, TypeVar, overload
-from typing_extensions import ParamSpec, Self, TypeAlias, TypeGuard, TypeIs
+from typing import Any, ClassVar, Final, Literal, NamedTuple, Protocol, TypeVar, overload, type_check_only
+from typing_extensions import ParamSpec, Self, TypeAlias, TypeGuard, TypeIs, deprecated, disjoint_base
 
 if sys.version_info >= (3, 14):
     from annotationlib import Format
@@ -240,10 +240,11 @@ def isasyncgenfunction(obj: Callable[..., AsyncGenerator[Any, Any]]) -> bool: ..
 def isasyncgenfunction(obj: Callable[_P, Any]) -> TypeGuard[Callable[_P, AsyncGeneratorType[Any, Any]]]: ...
 @overload
 def isasyncgenfunction(obj: object) -> TypeGuard[Callable[..., AsyncGeneratorType[Any, Any]]]: ...
-
+@type_check_only
 class _SupportsSet(Protocol[_T_contra, _V_contra]):
     def __set__(self, instance: _T_contra, value: _V_contra, /) -> None: ...
 
+@type_check_only
 class _SupportsDelete(Protocol[_T_contra]):
     def __delete__(self, instance: _T_contra, /) -> None: ...
 
@@ -335,6 +336,7 @@ class _void: ...
 class _empty: ...
 
 class Signature:
+    __slots__ = ("_return_annotation", "_parameters")
     def __init__(
         self, parameters: Sequence[Parameter] | None = None, *, return_annotation: Any = ..., __validate_parameters__: bool = True
     ) -> None: ...
@@ -415,6 +417,7 @@ if sys.version_info >= (3, 12):
     def getasyncgenlocals(agen: AsyncGeneratorType[Any, Any]) -> dict[str, Any]: ...
 
 class Parameter:
+    __slots__ = ("_name", "_kind", "_default", "_annotation")
     def __init__(self, name: str, kind: _ParameterKind, *, default: Any = ..., annotation: Any = ...) -> None: ...
     empty = _empty
 
@@ -446,6 +449,7 @@ class Parameter:
     def __hash__(self) -> int: ...
 
 class BoundArguments:
+    __slots__ = ("arguments", "_signature", "__weakref__")
     arguments: OrderedDict[str, Any]
     @property
     def args(self) -> tuple[Any, ...]: ...
@@ -475,12 +479,14 @@ class Arguments(NamedTuple):
 def getargs(co: CodeType) -> Arguments: ...
 
 if sys.version_info < (3, 11):
+    @deprecated("Deprecated since Python 3.0; removed in Python 3.11.")
     class ArgSpec(NamedTuple):
         args: list[str]
         varargs: str | None
         keywords: str | None
         defaults: tuple[Any, ...]
 
+    @deprecated("Deprecated since Python 3.0; removed in Python 3.11. Use `inspect.signature()` instead.")
     def getargspec(func: object) -> ArgSpec: ...
 
 class FullArgSpec(NamedTuple):
@@ -511,6 +517,9 @@ else:
 def formatannotationrelativeto(object: object) -> Callable[[object], str]: ...
 
 if sys.version_info < (3, 11):
+    @deprecated(
+        "Deprecated since Python 3.5; removed in Python 3.11. Use `inspect.signature()` and the `Signature` class instead."
+    )
     def formatargspec(
         args: list[str],
         varargs: str | None = None,
@@ -561,19 +570,6 @@ if sys.version_info >= (3, 11):
         code_context: list[str] | None
         index: int | None  # type: ignore[assignment]
 
-    class Traceback(_Traceback):
-        positions: dis.Positions | None
-        def __new__(
-            cls,
-            filename: str,
-            lineno: int,
-            function: str,
-            code_context: list[str] | None,
-            index: int | None,
-            *,
-            positions: dis.Positions | None = None,
-        ) -> Self: ...
-
     class _FrameInfo(NamedTuple):
         frame: FrameType
         filename: str
@@ -582,19 +578,63 @@ if sys.version_info >= (3, 11):
         code_context: list[str] | None
         index: int | None  # type: ignore[assignment]
 
-    class FrameInfo(_FrameInfo):
-        positions: dis.Positions | None
-        def __new__(
-            cls,
-            frame: FrameType,
-            filename: str,
-            lineno: int,
-            function: str,
-            code_context: list[str] | None,
-            index: int | None,
-            *,
-            positions: dis.Positions | None = None,
-        ) -> Self: ...
+    if sys.version_info >= (3, 12):
+        class Traceback(_Traceback):
+            positions: dis.Positions | None
+            def __new__(
+                cls,
+                filename: str,
+                lineno: int,
+                function: str,
+                code_context: list[str] | None,
+                index: int | None,
+                *,
+                positions: dis.Positions | None = None,
+            ) -> Self: ...
+
+        class FrameInfo(_FrameInfo):
+            positions: dis.Positions | None
+            def __new__(
+                cls,
+                frame: FrameType,
+                filename: str,
+                lineno: int,
+                function: str,
+                code_context: list[str] | None,
+                index: int | None,
+                *,
+                positions: dis.Positions | None = None,
+            ) -> Self: ...
+
+    else:
+        @disjoint_base
+        class Traceback(_Traceback):
+            positions: dis.Positions | None
+            def __new__(
+                cls,
+                filename: str,
+                lineno: int,
+                function: str,
+                code_context: list[str] | None,
+                index: int | None,
+                *,
+                positions: dis.Positions | None = None,
+            ) -> Self: ...
+
+        @disjoint_base
+        class FrameInfo(_FrameInfo):
+            positions: dis.Positions | None
+            def __new__(
+                cls,
+                frame: FrameType,
+                filename: str,
+                lineno: int,
+                function: str,
+                code_context: list[str] | None,
+                index: int | None,
+                *,
+                positions: dis.Positions | None = None,
+            ) -> Self: ...
 
 else:
     class Traceback(NamedTuple):
diff --git a/mypy/typeshed/stdlib/io.pyi b/mypy/typeshed/stdlib/io.pyi
index 1313df183d36..d301d700e9d0 100644
--- a/mypy/typeshed/stdlib/io.pyi
+++ b/mypy/typeshed/stdlib/io.pyi
@@ -67,7 +67,9 @@ class TextIOBase(_TextIOBase, IOBase): ...
 
 if sys.version_info >= (3, 14):
     class Reader(Protocol[_T_co]):
+        __slots__ = ()
         def read(self, size: int = ..., /) -> _T_co: ...
 
     class Writer(Protocol[_T_contra]):
+        __slots__ = ()
         def write(self, data: _T_contra, /) -> int: ...
diff --git a/mypy/typeshed/stdlib/ipaddress.pyi b/mypy/typeshed/stdlib/ipaddress.pyi
index 9df6bab7c167..e2f3defa2dea 100644
--- a/mypy/typeshed/stdlib/ipaddress.pyi
+++ b/mypy/typeshed/stdlib/ipaddress.pyi
@@ -22,6 +22,7 @@ def ip_interface(
 ) -> IPv4Interface | IPv6Interface: ...
 
 class _IPAddressBase:
+    __slots__ = ()
     @property
     def compressed(self) -> str: ...
     @property
@@ -33,6 +34,7 @@ class _IPAddressBase:
         def version(self) -> int: ...
 
 class _BaseAddress(_IPAddressBase):
+    __slots__ = ()
     def __add__(self, other: int) -> Self: ...
     def __hash__(self) -> int: ...
     def __int__(self) -> int: ...
@@ -71,7 +73,7 @@ class _BaseNetwork(_IPAddressBase, Generic[_A]):
     @property
     def broadcast_address(self) -> _A: ...
     def compare_networks(self, other: Self) -> int: ...
-    def hosts(self) -> Iterator[_A]: ...
+    def hosts(self) -> Iterator[_A] | list[_A]: ...
     @property
     def is_global(self) -> bool: ...
     @property
@@ -105,6 +107,7 @@ class _BaseNetwork(_IPAddressBase, Generic[_A]):
     def hostmask(self) -> _A: ...
 
 class _BaseV4:
+    __slots__ = ()
     if sys.version_info >= (3, 14):
         version: Final = 4
         max_prefixlen: Final = 32
@@ -115,6 +118,7 @@ class _BaseV4:
         def max_prefixlen(self) -> Literal[32]: ...
 
 class IPv4Address(_BaseV4, _BaseAddress):
+    __slots__ = ("_ip", "__weakref__")
     def __init__(self, address: object) -> None: ...
     @property
     def is_global(self) -> bool: ...
@@ -137,7 +141,7 @@ class IPv4Address(_BaseV4, _BaseAddress):
         def ipv6_mapped(self) -> IPv6Address: ...
 
 class IPv4Network(_BaseV4, _BaseNetwork[IPv4Address]):
-    def __init__(self, address: object, strict: bool = ...) -> None: ...
+    def __init__(self, address: object, strict: bool = True) -> None: ...
 
 class IPv4Interface(IPv4Address):
     netmask: IPv4Address
@@ -156,6 +160,7 @@ class IPv4Interface(IPv4Address):
     def with_prefixlen(self) -> str: ...
 
 class _BaseV6:
+    __slots__ = ()
     if sys.version_info >= (3, 14):
         version: Final = 6
         max_prefixlen: Final = 128
@@ -166,6 +171,7 @@ class _BaseV6:
         def max_prefixlen(self) -> Literal[128]: ...
 
 class IPv6Address(_BaseV6, _BaseAddress):
+    __slots__ = ("_ip", "_scope_id", "__weakref__")
     def __init__(self, address: object) -> None: ...
     @property
     def is_global(self) -> bool: ...
@@ -197,7 +203,7 @@ class IPv6Address(_BaseV6, _BaseAddress):
     def __eq__(self, other: object) -> bool: ...
 
 class IPv6Network(_BaseV6, _BaseNetwork[IPv6Address]):
-    def __init__(self, address: object, strict: bool = ...) -> None: ...
+    def __init__(self, address: object, strict: bool = True) -> None: ...
     @property
     def is_site_local(self) -> bool: ...
 
diff --git a/mypy/typeshed/stdlib/itertools.pyi b/mypy/typeshed/stdlib/itertools.pyi
index 7d05b1318680..73745fe92d9e 100644
--- a/mypy/typeshed/stdlib/itertools.pyi
+++ b/mypy/typeshed/stdlib/itertools.pyi
@@ -3,7 +3,7 @@ from _typeshed import MaybeNone
 from collections.abc import Callable, Iterable, Iterator
 from types import GenericAlias
 from typing import Any, Generic, Literal, SupportsComplex, SupportsFloat, SupportsIndex, SupportsInt, TypeVar, overload
-from typing_extensions import Self, TypeAlias
+from typing_extensions import Self, TypeAlias, disjoint_base
 
 _T = TypeVar("_T")
 _S = TypeVar("_S")
@@ -27,6 +27,7 @@ _Predicate: TypeAlias = Callable[[_T], object]
 
 # Technically count can take anything that implements a number protocol and has an add method
 # but we can't enforce the add method
+@disjoint_base
 class count(Iterator[_N]):
     @overload
     def __new__(cls) -> count[int]: ...
@@ -37,11 +38,13 @@ class count(Iterator[_N]):
     def __next__(self) -> _N: ...
     def __iter__(self) -> Self: ...
 
+@disjoint_base
 class cycle(Iterator[_T]):
     def __new__(cls, iterable: Iterable[_T], /) -> Self: ...
     def __next__(self) -> _T: ...
     def __iter__(self) -> Self: ...
 
+@disjoint_base
 class repeat(Iterator[_T]):
     @overload
     def __new__(cls, object: _T) -> Self: ...
@@ -51,6 +54,7 @@ class repeat(Iterator[_T]):
     def __iter__(self) -> Self: ...
     def __length_hint__(self) -> int: ...
 
+@disjoint_base
 class accumulate(Iterator[_T]):
     @overload
     def __new__(cls, iterable: Iterable[_T], func: None = None, *, initial: _T | None = ...) -> Self: ...
@@ -59,6 +63,7 @@ class accumulate(Iterator[_T]):
     def __iter__(self) -> Self: ...
     def __next__(self) -> _T: ...
 
+@disjoint_base
 class chain(Iterator[_T]):
     def __new__(cls, *iterables: Iterable[_T]) -> Self: ...
     def __next__(self) -> _T: ...
@@ -68,21 +73,25 @@ class chain(Iterator[_T]):
     def from_iterable(cls: type[Any], iterable: Iterable[Iterable[_S]], /) -> chain[_S]: ...
     def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
+@disjoint_base
 class compress(Iterator[_T]):
     def __new__(cls, data: Iterable[_T], selectors: Iterable[Any]) -> Self: ...
     def __iter__(self) -> Self: ...
     def __next__(self) -> _T: ...
 
+@disjoint_base
 class dropwhile(Iterator[_T]):
     def __new__(cls, predicate: _Predicate[_T], iterable: Iterable[_T], /) -> Self: ...
     def __iter__(self) -> Self: ...
     def __next__(self) -> _T: ...
 
+@disjoint_base
 class filterfalse(Iterator[_T]):
     def __new__(cls, function: _Predicate[_T] | None, iterable: Iterable[_T], /) -> Self: ...
     def __iter__(self) -> Self: ...
     def __next__(self) -> _T: ...
 
+@disjoint_base
 class groupby(Iterator[tuple[_T_co, Iterator[_S_co]]], Generic[_T_co, _S_co]):
     @overload
     def __new__(cls, iterable: Iterable[_T1], key: None = None) -> groupby[_T1, _T1]: ...
@@ -91,6 +100,7 @@ class groupby(Iterator[tuple[_T_co, Iterator[_S_co]]], Generic[_T_co, _S_co]):
     def __iter__(self) -> Self: ...
     def __next__(self) -> tuple[_T_co, Iterator[_S_co]]: ...
 
+@disjoint_base
 class islice(Iterator[_T]):
     @overload
     def __new__(cls, iterable: Iterable[_T], stop: int | None, /) -> Self: ...
@@ -99,18 +109,20 @@ class islice(Iterator[_T]):
     def __iter__(self) -> Self: ...
     def __next__(self) -> _T: ...
 
+@disjoint_base
 class starmap(Iterator[_T_co]):
     def __new__(cls, function: Callable[..., _T], iterable: Iterable[Iterable[Any]], /) -> starmap[_T]: ...
     def __iter__(self) -> Self: ...
     def __next__(self) -> _T_co: ...
 
+@disjoint_base
 class takewhile(Iterator[_T]):
     def __new__(cls, predicate: _Predicate[_T], iterable: Iterable[_T], /) -> Self: ...
     def __iter__(self) -> Self: ...
     def __next__(self) -> _T: ...
 
 def tee(iterable: Iterable[_T], n: int = 2, /) -> tuple[Iterator[_T], ...]: ...
-
+@disjoint_base
 class zip_longest(Iterator[_T_co]):
     # one iterable (fillvalue doesn't matter)
     @overload
@@ -189,6 +201,7 @@ class zip_longest(Iterator[_T_co]):
     def __iter__(self) -> Self: ...
     def __next__(self) -> _T_co: ...
 
+@disjoint_base
 class product(Iterator[_T_co]):
     @overload
     def __new__(cls, iter1: Iterable[_T1], /) -> product[tuple[_T1]]: ...
@@ -274,6 +287,7 @@ class product(Iterator[_T_co]):
     def __iter__(self) -> Self: ...
     def __next__(self) -> _T_co: ...
 
+@disjoint_base
 class permutations(Iterator[_T_co]):
     @overload
     def __new__(cls, iterable: Iterable[_T], r: Literal[2]) -> permutations[tuple[_T, _T]]: ...
@@ -288,6 +302,7 @@ class permutations(Iterator[_T_co]):
     def __iter__(self) -> Self: ...
     def __next__(self) -> _T_co: ...
 
+@disjoint_base
 class combinations(Iterator[_T_co]):
     @overload
     def __new__(cls, iterable: Iterable[_T], r: Literal[2]) -> combinations[tuple[_T, _T]]: ...
@@ -302,6 +317,7 @@ class combinations(Iterator[_T_co]):
     def __iter__(self) -> Self: ...
     def __next__(self) -> _T_co: ...
 
+@disjoint_base
 class combinations_with_replacement(Iterator[_T_co]):
     @overload
     def __new__(cls, iterable: Iterable[_T], r: Literal[2]) -> combinations_with_replacement[tuple[_T, _T]]: ...
@@ -317,12 +333,14 @@ class combinations_with_replacement(Iterator[_T_co]):
     def __next__(self) -> _T_co: ...
 
 if sys.version_info >= (3, 10):
+    @disjoint_base
     class pairwise(Iterator[_T_co]):
         def __new__(cls, iterable: Iterable[_T], /) -> pairwise[tuple[_T, _T]]: ...
         def __iter__(self) -> Self: ...
         def __next__(self) -> _T_co: ...
 
 if sys.version_info >= (3, 12):
+    @disjoint_base
     class batched(Iterator[tuple[_T_co, ...]], Generic[_T_co]):
         if sys.version_info >= (3, 13):
             def __new__(cls, iterable: Iterable[_T_co], n: int, *, strict: bool = False) -> Self: ...
diff --git a/mypy/typeshed/stdlib/lib2to3/fixes/fix_tuple_params.pyi b/mypy/typeshed/stdlib/lib2to3/fixes/fix_tuple_params.pyi
index bfaa9970c996..7f4f7f4e8656 100644
--- a/mypy/typeshed/stdlib/lib2to3/fixes/fix_tuple_params.pyi
+++ b/mypy/typeshed/stdlib/lib2to3/fixes/fix_tuple_params.pyi
@@ -1,4 +1,3 @@
-from _typeshed import Incomplete
 from typing import ClassVar, Literal
 
 from .. import fixer_base
@@ -13,5 +12,5 @@ class FixTupleParams(fixer_base.BaseFix):
 
 def simplify_args(node): ...
 def find_params(node): ...
-def map_to_index(param_list, prefix=..., d: Incomplete | None = ...): ...
+def map_to_index(param_list, prefix=[], d=None): ...
 def tuple_name(param_list): ...
diff --git a/mypy/typeshed/stdlib/locale.pyi b/mypy/typeshed/stdlib/locale.pyi
index 58de65449572..fae9f849b637 100644
--- a/mypy/typeshed/stdlib/locale.pyi
+++ b/mypy/typeshed/stdlib/locale.pyi
@@ -18,6 +18,7 @@ from builtins import str as _str
 from collections.abc import Callable, Iterable
 from decimal import Decimal
 from typing import Any
+from typing_extensions import deprecated
 
 if sys.version_info >= (3, 11):
     from _locale import getencoding as getencoding
@@ -137,9 +138,14 @@ def getpreferredencoding(do_setlocale: bool = True) -> _str: ...
 def normalize(localename: _str) -> _str: ...
 
 if sys.version_info < (3, 13):
-    def resetlocale(category: int = ...) -> None: ...
+    if sys.version_info >= (3, 11):
+        @deprecated("Deprecated since Python 3.11; removed in Python 3.13. Use `locale.setlocale(locale.LC_ALL, '')` instead.")
+        def resetlocale(category: int = ...) -> None: ...
+    else:
+        def resetlocale(category: int = ...) -> None: ...
 
 if sys.version_info < (3, 12):
+    @deprecated("Deprecated since Python 3.7; removed in Python 3.12. Use `locale.format_string()` instead.")
     def format(
         percent: _str, value: float | Decimal, grouping: bool = False, monetary: bool = False, *additional: Any
     ) -> _str: ...
diff --git a/mypy/typeshed/stdlib/logging/__init__.pyi b/mypy/typeshed/stdlib/logging/__init__.pyi
index 24529bd48d6a..8248f82ea87a 100644
--- a/mypy/typeshed/stdlib/logging/__init__.pyi
+++ b/mypy/typeshed/stdlib/logging/__init__.pyi
@@ -7,7 +7,7 @@ from re import Pattern
 from string import Template
 from time import struct_time
 from types import FrameType, GenericAlias, TracebackType
-from typing import Any, ClassVar, Final, Generic, Literal, Protocol, TextIO, TypeVar, overload
+from typing import Any, ClassVar, Final, Generic, Literal, Protocol, TextIO, TypeVar, overload, type_check_only
 from typing_extensions import Self, TypeAlias, deprecated
 
 __all__ = [
@@ -67,11 +67,13 @@ _Level: TypeAlias = int | str
 _FormatStyle: TypeAlias = Literal["%", "{", "$"]
 
 if sys.version_info >= (3, 12):
+    @type_check_only
     class _SupportsFilter(Protocol):
         def filter(self, record: LogRecord, /) -> bool | LogRecord: ...
 
     _FilterType: TypeAlias = Filter | Callable[[LogRecord], bool | LogRecord] | _SupportsFilter
 else:
+    @type_check_only
     class _SupportsFilter(Protocol):
         def filter(self, record: LogRecord, /) -> bool: ...
 
@@ -153,7 +155,7 @@ class Logger(Filterer):
         stacklevel: int = 1,
         extra: Mapping[str, object] | None = None,
     ) -> None: ...
-    @deprecated("Deprecated; use warning() instead.")
+    @deprecated("Deprecated since Python 3.3. Use `Logger.warning()` instead.")
     def warn(
         self,
         msg: object,
@@ -407,7 +409,7 @@ class LoggerAdapter(Generic[_L]):
         extra: Mapping[str, object] | None = None,
         **kwargs: object,
     ) -> None: ...
-    @deprecated("Deprecated; use warning() instead.")
+    @deprecated("Deprecated since Python 3.3. Use `LoggerAdapter.warning()` instead.")
     def warn(
         self,
         msg: object,
@@ -517,7 +519,7 @@ def warning(
     stacklevel: int = 1,
     extra: Mapping[str, object] | None = None,
 ) -> None: ...
-@deprecated("Deprecated; use warning() instead.")
+@deprecated("Deprecated since Python 3.3. Use `warning()` instead.")
 def warn(
     msg: object,
     *args: object,
@@ -657,4 +659,4 @@ class StringTemplateStyle(PercentStyle):  # undocumented
 
 _STYLES: Final[dict[str, tuple[PercentStyle, str]]]
 
-BASIC_FORMAT: Final[str]
+BASIC_FORMAT: Final = "%(levelname)s:%(name)s:%(message)s"
diff --git a/mypy/typeshed/stdlib/logging/config.pyi b/mypy/typeshed/stdlib/logging/config.pyi
index 000ba1ebb06e..72412ddc2cea 100644
--- a/mypy/typeshed/stdlib/logging/config.pyi
+++ b/mypy/typeshed/stdlib/logging/config.pyi
@@ -5,11 +5,11 @@ from configparser import RawConfigParser
 from re import Pattern
 from threading import Thread
 from typing import IO, Any, Final, Literal, SupportsIndex, TypedDict, overload, type_check_only
-from typing_extensions import Required, TypeAlias
+from typing_extensions import Required, TypeAlias, disjoint_base
 
 from . import Filter, Filterer, Formatter, Handler, Logger, _FilterType, _FormatStyle, _Level
 
-DEFAULT_LOGGING_CONFIG_PORT: int
+DEFAULT_LOGGING_CONFIG_PORT: Final = 9030
 RESET_ERROR: Final[int]  # undocumented
 IDENTIFIER: Final[Pattern[str]]  # undocumented
 
@@ -100,13 +100,22 @@ class ConvertingList(list[Any], ConvertingMixin):  # undocumented
     def __getitem__(self, key: slice) -> Any: ...
     def pop(self, idx: SupportsIndex = -1) -> Any: ...
 
-class ConvertingTuple(tuple[Any, ...], ConvertingMixin):  # undocumented
-    @overload
-    def __getitem__(self, key: SupportsIndex) -> Any: ...
-    @overload
-    def __getitem__(self, key: slice) -> Any: ...
+if sys.version_info >= (3, 12):
+    class ConvertingTuple(tuple[Any, ...], ConvertingMixin):  # undocumented
+        @overload
+        def __getitem__(self, key: SupportsIndex) -> Any: ...
+        @overload
+        def __getitem__(self, key: slice) -> Any: ...
 
-class BaseConfigurator:  # undocumented
+else:
+    @disjoint_base
+    class ConvertingTuple(tuple[Any, ...], ConvertingMixin):  # undocumented
+        @overload
+        def __getitem__(self, key: SupportsIndex) -> Any: ...
+        @overload
+        def __getitem__(self, key: slice) -> Any: ...
+
+class BaseConfigurator:
     CONVERT_PATTERN: Pattern[str]
     WORD_PATTERN: Pattern[str]
     DOT_PATTERN: Pattern[str]
@@ -115,6 +124,8 @@ class BaseConfigurator:  # undocumented
     value_converters: dict[str, str]
     importer: Callable[..., Any]
 
+    config: dict[str, Any]  # undocumented
+
     def __init__(self, config: _DictConfigArgs | dict[str, Any]) -> None: ...
     def resolve(self, s: str) -> Any: ...
     def ext_convert(self, value: str) -> Any: ...
diff --git a/mypy/typeshed/stdlib/logging/handlers.pyi b/mypy/typeshed/stdlib/logging/handlers.pyi
index 9636b81dc4f3..535f1c685183 100644
--- a/mypy/typeshed/stdlib/logging/handlers.pyi
+++ b/mypy/typeshed/stdlib/logging/handlers.pyi
@@ -9,17 +9,17 @@ from re import Pattern
 from socket import SocketKind, socket
 from threading import Thread
 from types import TracebackType
-from typing import Any, ClassVar, Final, Protocol, TypeVar
+from typing import Any, ClassVar, Final, Protocol, TypeVar, type_check_only
 from typing_extensions import Self
 
 _T = TypeVar("_T")
 
-DEFAULT_TCP_LOGGING_PORT: Final[int]
-DEFAULT_UDP_LOGGING_PORT: Final[int]
-DEFAULT_HTTP_LOGGING_PORT: Final[int]
-DEFAULT_SOAP_LOGGING_PORT: Final[int]
-SYSLOG_UDP_PORT: Final[int]
-SYSLOG_TCP_PORT: Final[int]
+DEFAULT_TCP_LOGGING_PORT: Final = 9020
+DEFAULT_UDP_LOGGING_PORT: Final = 9021
+DEFAULT_HTTP_LOGGING_PORT: Final = 9022
+DEFAULT_SOAP_LOGGING_PORT: Final = 9023
+SYSLOG_UDP_PORT: Final = 514
+SYSLOG_TCP_PORT: Final = 514
 
 class WatchedFileHandler(FileHandler):
     dev: int  # undocumented
@@ -225,6 +225,7 @@ class HTTPHandler(Handler):
     def mapLogRecord(self, record: LogRecord) -> dict[str, Any]: ...
     def getConnection(self, host: str, secure: bool) -> http.client.HTTPConnection: ...  # undocumented
 
+@type_check_only
 class _QueueLike(Protocol[_T]):
     def get(self) -> _T: ...
     def put_nowait(self, item: _T, /) -> None: ...
diff --git a/mypy/typeshed/stdlib/lzma.pyi b/mypy/typeshed/stdlib/lzma.pyi
index b066d222466b..b7ef607b75cb 100644
--- a/mypy/typeshed/stdlib/lzma.pyi
+++ b/mypy/typeshed/stdlib/lzma.pyi
@@ -35,7 +35,8 @@ from _lzma import (
     is_check_supported as is_check_supported,
 )
 from _typeshed import ReadableBuffer, StrOrBytesPath
-from typing import IO, Literal, TextIO, overload
+from io import TextIOWrapper
+from typing import IO, Literal, overload
 from typing_extensions import Self, TypeAlias
 
 if sys.version_info >= (3, 14):
@@ -144,7 +145,7 @@ def open(
     encoding: str | None = None,
     errors: str | None = None,
     newline: str | None = None,
-) -> TextIO: ...
+) -> TextIOWrapper: ...
 @overload
 def open(
     filename: StrOrBytesPath,
@@ -157,7 +158,7 @@ def open(
     encoding: str | None = None,
     errors: str | None = None,
     newline: str | None = None,
-) -> TextIO: ...
+) -> TextIOWrapper: ...
 @overload
 def open(
     filename: _PathOrFile,
@@ -170,7 +171,7 @@ def open(
     encoding: str | None = None,
     errors: str | None = None,
     newline: str | None = None,
-) -> LZMAFile | TextIO: ...
+) -> LZMAFile | TextIOWrapper: ...
 def compress(
     data: ReadableBuffer, format: int = 1, check: int = -1, preset: int | None = None, filters: _FilterChain | None = None
 ) -> bytes: ...
diff --git a/mypy/typeshed/stdlib/mailbox.pyi b/mypy/typeshed/stdlib/mailbox.pyi
index ff605c0661fb..89bd998b4dfe 100644
--- a/mypy/typeshed/stdlib/mailbox.pyi
+++ b/mypy/typeshed/stdlib/mailbox.pyi
@@ -6,7 +6,7 @@ from abc import ABCMeta, abstractmethod
 from collections.abc import Callable, Iterable, Iterator, Mapping, Sequence
 from email._policybase import _MessageT
 from types import GenericAlias, TracebackType
-from typing import IO, Any, AnyStr, Generic, Literal, Protocol, TypeVar, overload
+from typing import IO, Any, AnyStr, Generic, Literal, Protocol, TypeVar, overload, type_check_only
 from typing_extensions import Self, TypeAlias
 
 __all__ = [
@@ -31,13 +31,16 @@ __all__ = [
 
 _T = TypeVar("_T")
 
+@type_check_only
 class _SupportsReadAndReadline(SupportsRead[bytes], SupportsNoArgReadline[bytes], Protocol): ...
 
 _MessageData: TypeAlias = email.message.Message | bytes | str | io.StringIO | _SupportsReadAndReadline
 
+@type_check_only
 class _HasIteritems(Protocol):
     def iteritems(self) -> Iterator[tuple[str, _MessageData]]: ...
 
+@type_check_only
 class _HasItems(Protocol):
     def items(self) -> Iterator[tuple[str, _MessageData]]: ...
 
diff --git a/mypy/typeshed/stdlib/math.pyi b/mypy/typeshed/stdlib/math.pyi
index 9e77f0cd7e06..1903d488f7bb 100644
--- a/mypy/typeshed/stdlib/math.pyi
+++ b/mypy/typeshed/stdlib/math.pyi
@@ -1,7 +1,7 @@
 import sys
 from _typeshed import SupportsMul, SupportsRMul
 from collections.abc import Iterable
-from typing import Any, Final, Literal, Protocol, SupportsFloat, SupportsIndex, TypeVar, overload
+from typing import Any, Final, Literal, Protocol, SupportsFloat, SupportsIndex, TypeVar, overload, type_check_only
 from typing_extensions import TypeAlias
 
 _T = TypeVar("_T")
@@ -26,6 +26,7 @@ def atanh(x: _SupportsFloatOrIndex, /) -> float: ...
 if sys.version_info >= (3, 11):
     def cbrt(x: _SupportsFloatOrIndex, /) -> float: ...
 
+@type_check_only
 class _SupportsCeil(Protocol[_T_co]):
     def __ceil__(self) -> _T_co: ...
 
@@ -49,7 +50,7 @@ if sys.version_info >= (3, 11):
 def expm1(x: _SupportsFloatOrIndex, /) -> float: ...
 def fabs(x: _SupportsFloatOrIndex, /) -> float: ...
 def factorial(x: SupportsIndex, /) -> int: ...
-
+@type_check_only
 class _SupportsFloor(Protocol[_T_co]):
     def __floor__(self) -> _T_co: ...
 
@@ -99,6 +100,7 @@ _LiteralInteger = _PositiveInteger | _NegativeInteger | Literal[0]  # noqa: Y026
 _MultiplicableT1 = TypeVar("_MultiplicableT1", bound=SupportsMul[Any, Any])
 _MultiplicableT2 = TypeVar("_MultiplicableT2", bound=SupportsMul[Any, Any])
 
+@type_check_only
 class _SupportsProdWithNoDefaultGiven(SupportsMul[Any, Any], SupportsRMul[int, Any], Protocol): ...
 
 _SupportsProdNoDefaultT = TypeVar("_SupportsProdNoDefaultT", bound=_SupportsProdWithNoDefaultGiven)
@@ -127,6 +129,7 @@ def tan(x: _SupportsFloatOrIndex, /) -> float: ...
 def tanh(x: _SupportsFloatOrIndex, /) -> float: ...
 
 # Is different from `_typeshed.SupportsTrunc`, which is not generic
+@type_check_only
 class _SupportsTrunc(Protocol[_T_co]):
     def __trunc__(self) -> _T_co: ...
 
diff --git a/mypy/typeshed/stdlib/mmap.pyi b/mypy/typeshed/stdlib/mmap.pyi
index c9b8358cde6c..8a5baba62914 100644
--- a/mypy/typeshed/stdlib/mmap.pyi
+++ b/mypy/typeshed/stdlib/mmap.pyi
@@ -1,38 +1,40 @@
+import os
 import sys
 from _typeshed import ReadableBuffer, Unused
 from collections.abc import Iterator
 from typing import Final, Literal, NoReturn, overload
-from typing_extensions import Self
+from typing_extensions import Self, disjoint_base
 
-ACCESS_DEFAULT: int
-ACCESS_READ: int
-ACCESS_WRITE: int
-ACCESS_COPY: int
+ACCESS_DEFAULT: Final = 0
+ACCESS_READ: Final = 1
+ACCESS_WRITE: Final = 2
+ACCESS_COPY: Final = 3
 
-ALLOCATIONGRANULARITY: int
+ALLOCATIONGRANULARITY: Final[int]
 
 if sys.platform == "linux":
-    MAP_DENYWRITE: int
-    MAP_EXECUTABLE: int
+    MAP_DENYWRITE: Final[int]
+    MAP_EXECUTABLE: Final[int]
     if sys.version_info >= (3, 10):
-        MAP_POPULATE: int
+        MAP_POPULATE: Final[int]
 if sys.version_info >= (3, 11) and sys.platform != "win32" and sys.platform != "darwin":
-    MAP_STACK: int
+    MAP_STACK: Final[int]
 
 if sys.platform != "win32":
-    MAP_ANON: int
-    MAP_ANONYMOUS: int
-    MAP_PRIVATE: int
-    MAP_SHARED: int
-    PROT_EXEC: int
-    PROT_READ: int
-    PROT_WRITE: int
+    MAP_ANON: Final[int]
+    MAP_ANONYMOUS: Final[int]
+    MAP_PRIVATE: Final[int]
+    MAP_SHARED: Final[int]
+    PROT_EXEC: Final[int]
+    PROT_READ: Final[int]
+    PROT_WRITE: Final[int]
 
-PAGESIZE: int
+PAGESIZE: Final[int]
 
+@disjoint_base
 class mmap:
     if sys.platform == "win32":
-        def __init__(self, fileno: int, length: int, tagname: str | None = ..., access: int = ..., offset: int = ...) -> None: ...
+        def __new__(self, fileno: int, length: int, tagname: str | None = None, access: int = 0, offset: int = 0) -> Self: ...
     else:
         if sys.version_info >= (3, 13):
             def __new__(
@@ -41,34 +43,38 @@ class mmap:
                 length: int,
                 flags: int = ...,
                 prot: int = ...,
-                access: int = ...,
-                offset: int = ...,
+                access: int = 0,
+                offset: int = 0,
                 *,
                 trackfd: bool = True,
             ) -> Self: ...
         else:
             def __new__(
-                cls, fileno: int, length: int, flags: int = ..., prot: int = ..., access: int = ..., offset: int = ...
+                cls, fileno: int, length: int, flags: int = ..., prot: int = ..., access: int = 0, offset: int = 0
             ) -> Self: ...
 
     def close(self) -> None: ...
-    def flush(self, offset: int = ..., size: int = ...) -> None: ...
+    def flush(self, offset: int = 0, size: int = ...) -> None: ...
     def move(self, dest: int, src: int, count: int) -> None: ...
     def read_byte(self) -> int: ...
     def readline(self) -> bytes: ...
     def resize(self, newsize: int) -> None: ...
-    def seek(self, pos: int, whence: int = ...) -> None: ...
+    if sys.platform != "win32":
+        def seek(self, pos: int, whence: Literal[0, 1, 2, 3, 4] = os.SEEK_SET) -> None: ...
+    else:
+        def seek(self, pos: int, whence: Literal[0, 1, 2] = os.SEEK_SET) -> None: ...
+
     def size(self) -> int: ...
     def tell(self) -> int: ...
     def write_byte(self, byte: int) -> None: ...
     def __len__(self) -> int: ...
     closed: bool
     if sys.platform != "win32":
-        def madvise(self, option: int, start: int = ..., length: int = ...) -> None: ...
+        def madvise(self, option: int, start: int = 0, length: int = ...) -> None: ...
 
     def find(self, sub: ReadableBuffer, start: int = ..., stop: int = ...) -> int: ...
     def rfind(self, sub: ReadableBuffer, start: int = ..., stop: int = ...) -> int: ...
-    def read(self, n: int | None = ...) -> bytes: ...
+    def read(self, n: int | None = None) -> bytes: ...
     def write(self, bytes: ReadableBuffer) -> int: ...
     @overload
     def __getitem__(self, key: int, /) -> int: ...
@@ -93,42 +99,42 @@ class mmap:
         def seekable(self) -> Literal[True]: ...
 
 if sys.platform != "win32":
-    MADV_NORMAL: int
-    MADV_RANDOM: int
-    MADV_SEQUENTIAL: int
-    MADV_WILLNEED: int
-    MADV_DONTNEED: int
-    MADV_FREE: int
+    MADV_NORMAL: Final[int]
+    MADV_RANDOM: Final[int]
+    MADV_SEQUENTIAL: Final[int]
+    MADV_WILLNEED: Final[int]
+    MADV_DONTNEED: Final[int]
+    MADV_FREE: Final[int]
 
 if sys.platform == "linux":
-    MADV_REMOVE: int
-    MADV_DONTFORK: int
-    MADV_DOFORK: int
-    MADV_HWPOISON: int
-    MADV_MERGEABLE: int
-    MADV_UNMERGEABLE: int
+    MADV_REMOVE: Final[int]
+    MADV_DONTFORK: Final[int]
+    MADV_DOFORK: Final[int]
+    MADV_HWPOISON: Final[int]
+    MADV_MERGEABLE: Final[int]
+    MADV_UNMERGEABLE: Final[int]
     # Seems like this constant is not defined in glibc.
     # See https://github.com/python/typeshed/pull/5360 for details
-    # MADV_SOFT_OFFLINE: int
-    MADV_HUGEPAGE: int
-    MADV_NOHUGEPAGE: int
-    MADV_DONTDUMP: int
-    MADV_DODUMP: int
+    # MADV_SOFT_OFFLINE: Final[int]
+    MADV_HUGEPAGE: Final[int]
+    MADV_NOHUGEPAGE: Final[int]
+    MADV_DONTDUMP: Final[int]
+    MADV_DODUMP: Final[int]
 
 # This Values are defined for FreeBSD but type checkers do not support conditions for these
 if sys.platform != "linux" and sys.platform != "darwin" and sys.platform != "win32":
-    MADV_NOSYNC: int
-    MADV_AUTOSYNC: int
-    MADV_NOCORE: int
-    MADV_CORE: int
-    MADV_PROTECT: int
+    MADV_NOSYNC: Final[int]
+    MADV_AUTOSYNC: Final[int]
+    MADV_NOCORE: Final[int]
+    MADV_CORE: Final[int]
+    MADV_PROTECT: Final[int]
 
 if sys.version_info >= (3, 10) and sys.platform == "darwin":
-    MADV_FREE_REUSABLE: int
-    MADV_FREE_REUSE: int
+    MADV_FREE_REUSABLE: Final[int]
+    MADV_FREE_REUSE: Final[int]
 
 if sys.version_info >= (3, 13) and sys.platform != "win32":
-    MAP_32BIT: Final = 32768
+    MAP_32BIT: Final[int]
 
 if sys.version_info >= (3, 13) and sys.platform == "darwin":
     MAP_NORESERVE: Final = 64
diff --git a/mypy/typeshed/stdlib/msilib/__init__.pyi b/mypy/typeshed/stdlib/msilib/__init__.pyi
index 3e43cbc44f52..622f585f5bee 100644
--- a/mypy/typeshed/stdlib/msilib/__init__.pyi
+++ b/mypy/typeshed/stdlib/msilib/__init__.pyi
@@ -1,26 +1,26 @@
 import sys
 from collections.abc import Container, Iterable, Sequence
 from types import ModuleType
-from typing import Any, Literal
+from typing import Any, Final
 
 if sys.platform == "win32":
     from _msi import *
     from _msi import _Database
 
-    AMD64: bool
-    Win64: bool
+    AMD64: Final[bool]
+    Win64: Final[bool]
 
-    datasizemask: Literal[0x00FF]
-    type_valid: Literal[0x0100]
-    type_localizable: Literal[0x0200]
-    typemask: Literal[0x0C00]
-    type_long: Literal[0x0000]
-    type_short: Literal[0x0400]
-    type_string: Literal[0x0C00]
-    type_binary: Literal[0x0800]
-    type_nullable: Literal[0x1000]
-    type_key: Literal[0x2000]
-    knownbits: Literal[0x3FFF]
+    datasizemask: Final = 0x00FF
+    type_valid: Final = 0x0100
+    type_localizable: Final = 0x0200
+    typemask: Final = 0x0C00
+    type_long: Final = 0x0000
+    type_short: Final = 0x0400
+    type_string: Final = 0x0C00
+    type_binary: Final = 0x0800
+    type_nullable: Final = 0x1000
+    type_key: Final = 0x2000
+    knownbits: Final = 0x3FFF
 
     class Table:
         name: str
diff --git a/mypy/typeshed/stdlib/msilib/schema.pyi b/mypy/typeshed/stdlib/msilib/schema.pyi
index 4ad9a1783fcd..3bbdc41a1e8e 100644
--- a/mypy/typeshed/stdlib/msilib/schema.pyi
+++ b/mypy/typeshed/stdlib/msilib/schema.pyi
@@ -1,4 +1,5 @@
 import sys
+from typing import Final
 
 if sys.platform == "win32":
     from . import Table
@@ -89,6 +90,6 @@ if sys.platform == "win32":
     Upgrade: Table
     Verb: Table
 
-    tables: list[Table]
+    tables: Final[list[Table]]
 
     _Validation_records: list[tuple[str, str, str, int | None, int | None, str | None, int | None, str | None, str | None, str]]
diff --git a/mypy/typeshed/stdlib/msilib/sequence.pyi b/mypy/typeshed/stdlib/msilib/sequence.pyi
index b8af09f46e65..a9f5c24717bd 100644
--- a/mypy/typeshed/stdlib/msilib/sequence.pyi
+++ b/mypy/typeshed/stdlib/msilib/sequence.pyi
@@ -1,13 +1,14 @@
 import sys
+from typing import Final
 from typing_extensions import TypeAlias
 
 if sys.platform == "win32":
     _SequenceType: TypeAlias = list[tuple[str, str | None, int]]
 
-    AdminExecuteSequence: _SequenceType
-    AdminUISequence: _SequenceType
-    AdvtExecuteSequence: _SequenceType
-    InstallExecuteSequence: _SequenceType
-    InstallUISequence: _SequenceType
+    AdminExecuteSequence: Final[_SequenceType]
+    AdminUISequence: Final[_SequenceType]
+    AdvtExecuteSequence: Final[_SequenceType]
+    InstallExecuteSequence: Final[_SequenceType]
+    InstallUISequence: Final[_SequenceType]
 
-    tables: list[str]
+    tables: Final[list[str]]
diff --git a/mypy/typeshed/stdlib/msilib/text.pyi b/mypy/typeshed/stdlib/msilib/text.pyi
index 441c843ca6cf..da3c5fd0fb7a 100644
--- a/mypy/typeshed/stdlib/msilib/text.pyi
+++ b/mypy/typeshed/stdlib/msilib/text.pyi
@@ -1,7 +1,8 @@
 import sys
+from typing import Final
 
 if sys.platform == "win32":
-    ActionText: list[tuple[str, str, str | None]]
-    UIText: list[tuple[str, str | None]]
+    ActionText: Final[list[tuple[str, str, str | None]]]
+    UIText: Final[list[tuple[str, str | None]]]
     dirname: str
-    tables: list[str]
+    tables: Final[list[str]]
diff --git a/mypy/typeshed/stdlib/msvcrt.pyi b/mypy/typeshed/stdlib/msvcrt.pyi
index 403a5d933522..5feca8eab5c1 100644
--- a/mypy/typeshed/stdlib/msvcrt.pyi
+++ b/mypy/typeshed/stdlib/msvcrt.pyi
@@ -9,10 +9,10 @@ if sys.platform == "win32":
     LK_NBLCK: Final = 2
     LK_RLCK: Final = 3
     LK_NBRLCK: Final = 4
-    SEM_FAILCRITICALERRORS: int
-    SEM_NOALIGNMENTFAULTEXCEPT: int
-    SEM_NOGPFAULTERRORBOX: int
-    SEM_NOOPENFILEERRORBOX: int
+    SEM_FAILCRITICALERRORS: Final = 0x0001
+    SEM_NOALIGNMENTFAULTEXCEPT: Final = 0x0004
+    SEM_NOGPFAULTERRORBOX: Final = 0x0002
+    SEM_NOOPENFILEERRORBOX: Final = 0x8000
     def locking(fd: int, mode: int, nbytes: int, /) -> None: ...
     def setmode(fd: int, mode: int, /) -> int: ...
     def open_osfhandle(handle: int, flags: int, /) -> int: ...
diff --git a/mypy/typeshed/stdlib/multiprocessing/heap.pyi b/mypy/typeshed/stdlib/multiprocessing/heap.pyi
index b5e2ced5e8ee..38191a099f1e 100644
--- a/mypy/typeshed/stdlib/multiprocessing/heap.pyi
+++ b/mypy/typeshed/stdlib/multiprocessing/heap.pyi
@@ -2,7 +2,7 @@ import sys
 from _typeshed import Incomplete
 from collections.abc import Callable
 from mmap import mmap
-from typing import Protocol
+from typing import Protocol, type_check_only
 from typing_extensions import TypeAlias
 
 __all__ = ["BufferWrapper"]
@@ -20,6 +20,7 @@ class Arena:
 _Block: TypeAlias = tuple[Arena, int, int]
 
 if sys.platform != "win32":
+    @type_check_only
     class _SupportsDetach(Protocol):
         def detach(self) -> int: ...
 
diff --git a/mypy/typeshed/stdlib/multiprocessing/managers.pyi b/mypy/typeshed/stdlib/multiprocessing/managers.pyi
index b0ccac41b925..5efe69a97377 100644
--- a/mypy/typeshed/stdlib/multiprocessing/managers.pyi
+++ b/mypy/typeshed/stdlib/multiprocessing/managers.pyi
@@ -38,6 +38,7 @@ class Namespace:
 _Namespace: TypeAlias = Namespace
 
 class Token:
+    __slots__ = ("typeid", "address", "id")
     typeid: str | bytes | None
     address: _Address | None
     id: str | bytes | int | None
diff --git a/mypy/typeshed/stdlib/multiprocessing/sharedctypes.pyi b/mypy/typeshed/stdlib/multiprocessing/sharedctypes.pyi
index 5283445d8545..e2ec15f05ea2 100644
--- a/mypy/typeshed/stdlib/multiprocessing/sharedctypes.pyi
+++ b/mypy/typeshed/stdlib/multiprocessing/sharedctypes.pyi
@@ -5,7 +5,7 @@ from ctypes import _SimpleCData, c_char
 from multiprocessing.context import BaseContext
 from multiprocessing.synchronize import _LockLike
 from types import TracebackType
-from typing import Any, Generic, Literal, Protocol, TypeVar, overload
+from typing import Any, Generic, Literal, Protocol, TypeVar, overload, type_check_only
 
 __all__ = ["RawValue", "RawArray", "Value", "Array", "copy", "synchronized"]
 
@@ -81,7 +81,7 @@ def synchronized(
 ) -> SynchronizedArray[_T]: ...
 @overload
 def synchronized(obj: _CT, lock: _LockLike | None = None, ctx: Any | None = None) -> SynchronizedBase[_CT]: ...
-
+@type_check_only
 class _AcquireFunc(Protocol):
     def __call__(self, block: bool = ..., timeout: float | None = ..., /) -> bool: ...
 
diff --git a/mypy/typeshed/stdlib/multiprocessing/util.pyi b/mypy/typeshed/stdlib/multiprocessing/util.pyi
index ecb4a7ddec7d..3583194c77e2 100644
--- a/mypy/typeshed/stdlib/multiprocessing/util.pyi
+++ b/mypy/typeshed/stdlib/multiprocessing/util.pyi
@@ -52,7 +52,7 @@ def get_logger() -> Logger: ...
 def log_to_stderr(level: _LoggingLevel | None = None) -> Logger: ...
 def is_abstract_socket_namespace(address: str | bytes | None) -> bool: ...
 
-abstract_sockets_supported: bool
+abstract_sockets_supported: Final[bool]
 
 def get_temp_dir() -> str: ...
 def register_after_fork(obj: _T, func: Callable[[_T], object]) -> None: ...
diff --git a/mypy/typeshed/stdlib/nt.pyi b/mypy/typeshed/stdlib/nt.pyi
index 3ed8f8af379b..0c87444d18f4 100644
--- a/mypy/typeshed/stdlib/nt.pyi
+++ b/mypy/typeshed/stdlib/nt.pyi
@@ -110,4 +110,7 @@ if sys.platform == "win32":
     if sys.version_info >= (3, 13):
         from os import fchmod as fchmod, lchmod as lchmod
 
+    if sys.version_info >= (3, 14):
+        from os import readinto as readinto
+
     environ: dict[str, str]
diff --git a/mypy/typeshed/stdlib/ntpath.pyi b/mypy/typeshed/stdlib/ntpath.pyi
index ebe305ef708c..074df075b972 100644
--- a/mypy/typeshed/stdlib/ntpath.pyi
+++ b/mypy/typeshed/stdlib/ntpath.pyi
@@ -1,6 +1,8 @@
 import sys
 from _typeshed import BytesPath, StrOrBytesPath, StrPath
 from genericpath import (
+    ALLOW_MISSING as ALLOW_MISSING,
+    _AllowMissingType,
     commonprefix as commonprefix,
     exists as exists,
     getatime as getatime,
@@ -89,6 +91,7 @@ __all__ = [
     "sameopenfile",
     "samestat",
     "commonpath",
+    "ALLOW_MISSING",
 ]
 if sys.version_info >= (3, 12):
     __all__ += ["isjunction", "splitroot"]
@@ -108,16 +111,10 @@ def join(path: StrPath, /, *paths: StrPath) -> str: ...
 def join(path: BytesPath, /, *paths: BytesPath) -> bytes: ...
 
 if sys.platform == "win32":
-    if sys.version_info >= (3, 10):
-        @overload
-        def realpath(path: PathLike[AnyStr], *, strict: bool = False) -> AnyStr: ...
-        @overload
-        def realpath(path: AnyStr, *, strict: bool = False) -> AnyStr: ...
-    else:
-        @overload
-        def realpath(path: PathLike[AnyStr]) -> AnyStr: ...
-        @overload
-        def realpath(path: AnyStr) -> AnyStr: ...
+    @overload
+    def realpath(path: PathLike[AnyStr], *, strict: bool | _AllowMissingType = False) -> AnyStr: ...
+    @overload
+    def realpath(path: AnyStr, *, strict: bool | _AllowMissingType = False) -> AnyStr: ...
 
 else:
     realpath = abspath
diff --git a/mypy/typeshed/stdlib/nturl2path.pyi b/mypy/typeshed/stdlib/nturl2path.pyi
index c38a359469d2..014af8a0fd2e 100644
--- a/mypy/typeshed/stdlib/nturl2path.pyi
+++ b/mypy/typeshed/stdlib/nturl2path.pyi
@@ -2,9 +2,9 @@ import sys
 from typing_extensions import deprecated
 
 if sys.version_info >= (3, 14):
-    @deprecated("nturl2path module was deprecated since Python 3.14")
+    @deprecated("The `nturl2path` module is deprecated since Python 3.14.")
     def url2pathname(url: str) -> str: ...
-    @deprecated("nturl2path module was deprecated since Python 3.14")
+    @deprecated("The `nturl2path` module is deprecated since Python 3.14.")
     def pathname2url(p: str) -> str: ...
 
 else:
diff --git a/mypy/typeshed/stdlib/numbers.pyi b/mypy/typeshed/stdlib/numbers.pyi
index 02d469ce0ee5..64fb16581e95 100644
--- a/mypy/typeshed/stdlib/numbers.pyi
+++ b/mypy/typeshed/stdlib/numbers.pyi
@@ -8,7 +8,7 @@
 # nor `float` as a subtype of `numbers.Real`, etc.)
 
 from abc import ABCMeta, abstractmethod
-from typing import ClassVar, Literal, Protocol, overload
+from typing import ClassVar, Literal, Protocol, overload, type_check_only
 
 __all__ = ["Number", "Complex", "Real", "Rational", "Integral"]
 
@@ -22,6 +22,7 @@ __all__ = ["Number", "Complex", "Real", "Rational", "Integral"]
 # NOTE: We can't include `__complex__` here,
 # as we want `int` to be seen as a subtype of `_ComplexLike`,
 # and `int.__complex__` does not exist :(
+@type_check_only
 class _ComplexLike(Protocol):
     def __neg__(self) -> _ComplexLike: ...
     def __pos__(self) -> _ComplexLike: ...
@@ -29,6 +30,7 @@ class _ComplexLike(Protocol):
 
 # _RealLike is a structural-typing approximation
 # of the `Real` ABC, which is not (and cannot be) a protocol
+@type_check_only
 class _RealLike(_ComplexLike, Protocol):
     def __trunc__(self) -> _IntegralLike: ...
     def __floor__(self) -> _IntegralLike: ...
@@ -41,6 +43,7 @@ class _RealLike(_ComplexLike, Protocol):
 
 # _IntegralLike is a structural-typing approximation
 # of the `Integral` ABC, which is not (and cannot be) a protocol
+@type_check_only
 class _IntegralLike(_RealLike, Protocol):
     def __invert__(self) -> _IntegralLike: ...
     def __int__(self) -> int: ...
@@ -58,12 +61,14 @@ class _IntegralLike(_RealLike, Protocol):
 #################
 
 class Number(metaclass=ABCMeta):
+    __slots__ = ()
     @abstractmethod
     def __hash__(self) -> int: ...
 
 # See comment at the top of the file
 # for why some of these return types are purposefully vague
 class Complex(Number, _ComplexLike):
+    __slots__ = ()
     @abstractmethod
     def __complex__(self) -> complex: ...
     def __bool__(self) -> bool: ...
@@ -106,6 +111,7 @@ class Complex(Number, _ComplexLike):
 # See comment at the top of the file
 # for why some of these return types are purposefully vague
 class Real(Complex, _RealLike):
+    __slots__ = ()
     @abstractmethod
     def __float__(self) -> float: ...
     @abstractmethod
@@ -150,6 +156,7 @@ class Real(Complex, _RealLike):
 # See comment at the top of the file
 # for why some of these return types are purposefully vague
 class Rational(Real):
+    __slots__ = ()
     @property
     @abstractmethod
     def numerator(self) -> _IntegralLike: ...
@@ -161,6 +168,7 @@ class Rational(Real):
 # See comment at the top of the file
 # for why some of these return types are purposefully vague
 class Integral(Rational, _IntegralLike):
+    __slots__ = ()
     @abstractmethod
     def __int__(self) -> int: ...
     def __index__(self) -> int: ...
diff --git a/mypy/typeshed/stdlib/opcode.pyi b/mypy/typeshed/stdlib/opcode.pyi
index a5a3a79c323b..ed0e96ef1cb9 100644
--- a/mypy/typeshed/stdlib/opcode.pyi
+++ b/mypy/typeshed/stdlib/opcode.pyi
@@ -1,5 +1,5 @@
 import sys
-from typing import Literal
+from typing import Final, Literal
 
 __all__ = [
     "cmp_op",
@@ -24,24 +24,24 @@ if sys.version_info >= (3, 13):
     __all__ += ["hasjump"]
 
 cmp_op: tuple[Literal["<"], Literal["<="], Literal["=="], Literal["!="], Literal[">"], Literal[">="]]
-hasconst: list[int]
-hasname: list[int]
-hasjrel: list[int]
-hasjabs: list[int]
-haslocal: list[int]
-hascompare: list[int]
-hasfree: list[int]
+hasconst: Final[list[int]]
+hasname: Final[list[int]]
+hasjrel: Final[list[int]]
+hasjabs: Final[list[int]]
+haslocal: Final[list[int]]
+hascompare: Final[list[int]]
+hasfree: Final[list[int]]
 if sys.version_info >= (3, 12):
-    hasarg: list[int]
-    hasexc: list[int]
+    hasarg: Final[list[int]]
+    hasexc: Final[list[int]]
 else:
-    hasnargs: list[int]
+    hasnargs: Final[list[int]]
 if sys.version_info >= (3, 13):
-    hasjump: list[int]
-opname: list[str]
+    hasjump: Final[list[int]]
+opname: Final[list[str]]
 
-opmap: dict[str, int]
-HAVE_ARGUMENT: int
-EXTENDED_ARG: int
+opmap: Final[dict[str, int]]
+HAVE_ARGUMENT: Final = 43
+EXTENDED_ARG: Final = 69
 
 def stack_effect(opcode: int, oparg: int | None = None, /, *, jump: bool | None = None) -> int: ...
diff --git a/mypy/typeshed/stdlib/optparse.pyi b/mypy/typeshed/stdlib/optparse.pyi
index 8b7fcd82e5a5..c52291799280 100644
--- a/mypy/typeshed/stdlib/optparse.pyi
+++ b/mypy/typeshed/stdlib/optparse.pyi
@@ -24,8 +24,7 @@ __all__ = [
     "BadOptionError",
     "check_choice",
 ]
-# pytype is not happy with `NO_DEFAULT: Final = ("NO", "DEFAULT")`
-NO_DEFAULT: Final[tuple[Literal["NO"], Literal["DEFAULT"]]]
+NO_DEFAULT: Final = ("NO", "DEFAULT")
 SUPPRESS_HELP: Final = "SUPPRESSHELP"
 SUPPRESS_USAGE: Final = "SUPPRESSUSAGE"
 
diff --git a/mypy/typeshed/stdlib/os/__init__.pyi b/mypy/typeshed/stdlib/os/__init__.pyi
index 5286c76d1b06..71c79dfac399 100644
--- a/mypy/typeshed/stdlib/os/__init__.pyi
+++ b/mypy/typeshed/stdlib/os/__init__.pyi
@@ -39,6 +39,7 @@ from typing import (
     final,
     overload,
     runtime_checkable,
+    type_check_only,
 )
 from typing_extensions import Self, TypeAlias, Unpack, deprecated
 
@@ -508,22 +509,22 @@ supports_follow_symlinks: set[Callable[..., Any]]
 
 if sys.platform != "win32":
     # Unix only
-    PRIO_PROCESS: int
-    PRIO_PGRP: int
-    PRIO_USER: int
+    PRIO_PROCESS: Final[int]
+    PRIO_PGRP: Final[int]
+    PRIO_USER: Final[int]
 
-    F_LOCK: int
-    F_TLOCK: int
-    F_ULOCK: int
-    F_TEST: int
+    F_LOCK: Final[int]
+    F_TLOCK: Final[int]
+    F_ULOCK: Final[int]
+    F_TEST: Final[int]
 
     if sys.platform != "darwin":
-        POSIX_FADV_NORMAL: int
-        POSIX_FADV_SEQUENTIAL: int
-        POSIX_FADV_RANDOM: int
-        POSIX_FADV_NOREUSE: int
-        POSIX_FADV_WILLNEED: int
-        POSIX_FADV_DONTNEED: int
+        POSIX_FADV_NORMAL: Final[int]
+        POSIX_FADV_SEQUENTIAL: Final[int]
+        POSIX_FADV_RANDOM: Final[int]
+        POSIX_FADV_NOREUSE: Final[int]
+        POSIX_FADV_WILLNEED: Final[int]
+        POSIX_FADV_DONTNEED: Final[int]
 
     if sys.platform != "linux" and sys.platform != "darwin":
         # In the os-module docs, these are marked as being available
@@ -533,145 +534,145 @@ if sys.platform != "win32":
         # so the sys-module docs recommend doing `if sys.platform.startswith('freebsd')`
         # to detect FreeBSD builds. Unfortunately that would be too dynamic
         # for type checkers, however.
-        SF_NODISKIO: int
-        SF_MNOWAIT: int
-        SF_SYNC: int
+        SF_NODISKIO: Final[int]
+        SF_MNOWAIT: Final[int]
+        SF_SYNC: Final[int]
 
         if sys.version_info >= (3, 11):
-            SF_NOCACHE: int
+            SF_NOCACHE: Final[int]
 
     if sys.platform == "linux":
-        XATTR_SIZE_MAX: int
-        XATTR_CREATE: int
-        XATTR_REPLACE: int
+        XATTR_SIZE_MAX: Final[int]
+        XATTR_CREATE: Final[int]
+        XATTR_REPLACE: Final[int]
 
-    P_PID: int
-    P_PGID: int
-    P_ALL: int
+    P_PID: Final[int]
+    P_PGID: Final[int]
+    P_ALL: Final[int]
 
     if sys.platform == "linux":
-        P_PIDFD: int
-
-    WEXITED: int
-    WSTOPPED: int
-    WNOWAIT: int
-
-    CLD_EXITED: int
-    CLD_DUMPED: int
-    CLD_TRAPPED: int
-    CLD_CONTINUED: int
-    CLD_KILLED: int
-    CLD_STOPPED: int
-
-    SCHED_OTHER: int
-    SCHED_FIFO: int
-    SCHED_RR: int
+        P_PIDFD: Final[int]
+
+    WEXITED: Final[int]
+    WSTOPPED: Final[int]
+    WNOWAIT: Final[int]
+
+    CLD_EXITED: Final[int]
+    CLD_DUMPED: Final[int]
+    CLD_TRAPPED: Final[int]
+    CLD_CONTINUED: Final[int]
+    CLD_KILLED: Final[int]
+    CLD_STOPPED: Final[int]
+
+    SCHED_OTHER: Final[int]
+    SCHED_FIFO: Final[int]
+    SCHED_RR: Final[int]
     if sys.platform != "darwin" and sys.platform != "linux":
-        SCHED_SPORADIC: int
+        SCHED_SPORADIC: Final[int]
 
 if sys.platform == "linux":
-    SCHED_BATCH: int
-    SCHED_IDLE: int
-    SCHED_RESET_ON_FORK: int
+    SCHED_BATCH: Final[int]
+    SCHED_IDLE: Final[int]
+    SCHED_RESET_ON_FORK: Final[int]
 
 if sys.version_info >= (3, 14) and sys.platform == "linux":
-    SCHED_DEADLINE: int
-    SCHED_NORMAL: int
+    SCHED_DEADLINE: Final[int]
+    SCHED_NORMAL: Final[int]
 
 if sys.platform != "win32":
-    RTLD_LAZY: int
-    RTLD_NOW: int
-    RTLD_GLOBAL: int
-    RTLD_LOCAL: int
-    RTLD_NODELETE: int
-    RTLD_NOLOAD: int
+    RTLD_LAZY: Final[int]
+    RTLD_NOW: Final[int]
+    RTLD_GLOBAL: Final[int]
+    RTLD_LOCAL: Final[int]
+    RTLD_NODELETE: Final[int]
+    RTLD_NOLOAD: Final[int]
 
 if sys.platform == "linux":
-    RTLD_DEEPBIND: int
-    GRND_NONBLOCK: int
-    GRND_RANDOM: int
+    RTLD_DEEPBIND: Final[int]
+    GRND_NONBLOCK: Final[int]
+    GRND_RANDOM: Final[int]
 
 if sys.platform == "darwin" and sys.version_info >= (3, 12):
-    PRIO_DARWIN_BG: int
-    PRIO_DARWIN_NONUI: int
-    PRIO_DARWIN_PROCESS: int
-    PRIO_DARWIN_THREAD: int
-
-SEEK_SET: int
-SEEK_CUR: int
-SEEK_END: int
+    PRIO_DARWIN_BG: Final[int]
+    PRIO_DARWIN_NONUI: Final[int]
+    PRIO_DARWIN_PROCESS: Final[int]
+    PRIO_DARWIN_THREAD: Final[int]
+
+SEEK_SET: Final = 0
+SEEK_CUR: Final = 1
+SEEK_END: Final = 2
 if sys.platform != "win32":
-    SEEK_DATA: int
-    SEEK_HOLE: int
-
-O_RDONLY: int
-O_WRONLY: int
-O_RDWR: int
-O_APPEND: int
-O_CREAT: int
-O_EXCL: int
-O_TRUNC: int
+    SEEK_DATA: Final = 3
+    SEEK_HOLE: Final = 4
+
+O_RDONLY: Final[int]
+O_WRONLY: Final[int]
+O_RDWR: Final[int]
+O_APPEND: Final[int]
+O_CREAT: Final[int]
+O_EXCL: Final[int]
+O_TRUNC: Final[int]
 if sys.platform == "win32":
-    O_BINARY: int
-    O_NOINHERIT: int
-    O_SHORT_LIVED: int
-    O_TEMPORARY: int
-    O_RANDOM: int
-    O_SEQUENTIAL: int
-    O_TEXT: int
+    O_BINARY: Final[int]
+    O_NOINHERIT: Final[int]
+    O_SHORT_LIVED: Final[int]
+    O_TEMPORARY: Final[int]
+    O_RANDOM: Final[int]
+    O_SEQUENTIAL: Final[int]
+    O_TEXT: Final[int]
 
 if sys.platform != "win32":
-    O_DSYNC: int
-    O_SYNC: int
-    O_NDELAY: int
-    O_NONBLOCK: int
-    O_NOCTTY: int
-    O_CLOEXEC: int
-    O_ASYNC: int  # Gnu extension if in C library
-    O_DIRECTORY: int  # Gnu extension if in C library
-    O_NOFOLLOW: int  # Gnu extension if in C library
-    O_ACCMODE: int  # TODO: when does this exist?
+    O_DSYNC: Final[int]
+    O_SYNC: Final[int]
+    O_NDELAY: Final[int]
+    O_NONBLOCK: Final[int]
+    O_NOCTTY: Final[int]
+    O_CLOEXEC: Final[int]
+    O_ASYNC: Final[int]  # Gnu extension if in C library
+    O_DIRECTORY: Final[int]  # Gnu extension if in C library
+    O_NOFOLLOW: Final[int]  # Gnu extension if in C library
+    O_ACCMODE: Final[int]  # TODO: when does this exist?
 
 if sys.platform == "linux":
-    O_RSYNC: int
-    O_DIRECT: int  # Gnu extension if in C library
-    O_NOATIME: int  # Gnu extension if in C library
-    O_PATH: int  # Gnu extension if in C library
-    O_TMPFILE: int  # Gnu extension if in C library
-    O_LARGEFILE: int  # Gnu extension if in C library
+    O_RSYNC: Final[int]
+    O_DIRECT: Final[int]  # Gnu extension if in C library
+    O_NOATIME: Final[int]  # Gnu extension if in C library
+    O_PATH: Final[int]  # Gnu extension if in C library
+    O_TMPFILE: Final[int]  # Gnu extension if in C library
+    O_LARGEFILE: Final[int]  # Gnu extension if in C library
 
 if sys.platform != "linux" and sys.platform != "win32":
-    O_SHLOCK: int
-    O_EXLOCK: int
+    O_SHLOCK: Final[int]
+    O_EXLOCK: Final[int]
 
 if sys.platform == "darwin" and sys.version_info >= (3, 10):
-    O_EVTONLY: int
-    O_NOFOLLOW_ANY: int
-    O_SYMLINK: int
+    O_EVTONLY: Final[int]
+    O_NOFOLLOW_ANY: Final[int]
+    O_SYMLINK: Final[int]
 
 if sys.platform != "win32" and sys.version_info >= (3, 10):
-    O_FSYNC: int
+    O_FSYNC: Final[int]
 
 if sys.platform != "linux" and sys.platform != "win32" and sys.version_info >= (3, 13):
-    O_EXEC: int
-    O_SEARCH: int
+    O_EXEC: Final[int]
+    O_SEARCH: Final[int]
 
 if sys.platform != "win32" and sys.platform != "darwin":
     # posix, but apparently missing on macos
-    ST_APPEND: int
-    ST_MANDLOCK: int
-    ST_NOATIME: int
-    ST_NODEV: int
-    ST_NODIRATIME: int
-    ST_NOEXEC: int
-    ST_RELATIME: int
-    ST_SYNCHRONOUS: int
-    ST_WRITE: int
+    ST_APPEND: Final[int]
+    ST_MANDLOCK: Final[int]
+    ST_NOATIME: Final[int]
+    ST_NODEV: Final[int]
+    ST_NODIRATIME: Final[int]
+    ST_NOEXEC: Final[int]
+    ST_RELATIME: Final[int]
+    ST_SYNCHRONOUS: Final[int]
+    ST_WRITE: Final[int]
 
 if sys.platform != "win32":
-    NGROUPS_MAX: int
-    ST_NOSUID: int
-    ST_RDONLY: int
+    NGROUPS_MAX: Final[int]
+    ST_NOSUID: Final[int]
+    ST_RDONLY: Final[int]
 
 curdir: str
 pardir: str
@@ -683,14 +684,14 @@ else:
 extsep: str
 pathsep: str
 defpath: str
-linesep: str
+linesep: Literal["\n", "\r\n"]
 devnull: str
 name: str
 
-F_OK: int
-R_OK: int
-W_OK: int
-X_OK: int
+F_OK: Final = 0
+R_OK: Final = 4
+W_OK: Final = 2
+X_OK: Final = 1
 
 _EnvironCodeFunc: TypeAlias = Callable[[AnyStr], AnyStr]
 
@@ -729,47 +730,47 @@ if sys.platform != "win32":
     environb: _Environ[bytes]
 
 if sys.version_info >= (3, 11) or sys.platform != "win32":
-    EX_OK: int
+    EX_OK: Final[int]
 
 if sys.platform != "win32":
     confstr_names: dict[str, int]
     pathconf_names: dict[str, int]
     sysconf_names: dict[str, int]
 
-    EX_USAGE: int
-    EX_DATAERR: int
-    EX_NOINPUT: int
-    EX_NOUSER: int
-    EX_NOHOST: int
-    EX_UNAVAILABLE: int
-    EX_SOFTWARE: int
-    EX_OSERR: int
-    EX_OSFILE: int
-    EX_CANTCREAT: int
-    EX_IOERR: int
-    EX_TEMPFAIL: int
-    EX_PROTOCOL: int
-    EX_NOPERM: int
-    EX_CONFIG: int
+    EX_USAGE: Final[int]
+    EX_DATAERR: Final[int]
+    EX_NOINPUT: Final[int]
+    EX_NOUSER: Final[int]
+    EX_NOHOST: Final[int]
+    EX_UNAVAILABLE: Final[int]
+    EX_SOFTWARE: Final[int]
+    EX_OSERR: Final[int]
+    EX_OSFILE: Final[int]
+    EX_CANTCREAT: Final[int]
+    EX_IOERR: Final[int]
+    EX_TEMPFAIL: Final[int]
+    EX_PROTOCOL: Final[int]
+    EX_NOPERM: Final[int]
+    EX_CONFIG: Final[int]
 
 # Exists on some Unix platforms, e.g. Solaris.
 if sys.platform != "win32" and sys.platform != "darwin" and sys.platform != "linux":
-    EX_NOTFOUND: int
+    EX_NOTFOUND: Final[int]
 
-P_NOWAIT: int
-P_NOWAITO: int
-P_WAIT: int
+P_NOWAIT: Final[int]
+P_NOWAITO: Final[int]
+P_WAIT: Final[int]
 if sys.platform == "win32":
-    P_DETACH: int
-    P_OVERLAY: int
+    P_DETACH: Final[int]
+    P_OVERLAY: Final[int]
 
 # wait()/waitpid() options
 if sys.platform != "win32":
-    WNOHANG: int  # Unix only
-    WCONTINUED: int  # some Unix systems
-    WUNTRACED: int  # Unix only
+    WNOHANG: Final[int]  # Unix only
+    WCONTINUED: Final[int]  # some Unix systems
+    WUNTRACED: Final[int]  # Unix only
 
-TMP_MAX: int  # Undocumented, but used by tempfile
+TMP_MAX: Final[int]  # Undocumented, but used by tempfile
 
 # ----- os classes (structures) -----
 @final
@@ -861,6 +862,7 @@ In the future, this property will contain the last metadata change time."""
 # on the allowlist for use as a Protocol starting in 3.14.
 @runtime_checkable
 class PathLike(ABC, Protocol[AnyStr_co]):  # type: ignore[misc]  # pyright: ignore[reportGeneralTypeIssues]
+    __slots__ = ()
     @abstractmethod
     def __fspath__(self) -> AnyStr_co: ...
 
@@ -1135,11 +1137,11 @@ if sys.platform != "win32":
     def pwritev(fd: int, buffers: SupportsLenAndGetItem[ReadableBuffer], offset: int, flags: int = 0, /) -> int: ...
     if sys.platform != "darwin":
         if sys.version_info >= (3, 10):
-            RWF_APPEND: int  # docs say available on 3.7+, stubtest says otherwise
-        RWF_DSYNC: int
-        RWF_SYNC: int
-        RWF_HIPRI: int
-        RWF_NOWAIT: int
+            RWF_APPEND: Final[int]  # docs say available on 3.7+, stubtest says otherwise
+        RWF_DSYNC: Final[int]
+        RWF_SYNC: Final[int]
+        RWF_HIPRI: Final[int]
+        RWF_NOWAIT: Final[int]
 
     if sys.platform == "linux":
         def sendfile(out_fd: FileDescriptor, in_fd: FileDescriptor, offset: int | None, count: int) -> int: ...
@@ -1149,8 +1151,8 @@ if sys.platform != "win32":
             in_fd: FileDescriptor,
             offset: int,
             count: int,
-            headers: Sequence[ReadableBuffer] = ...,
-            trailers: Sequence[ReadableBuffer] = ...,
+            headers: Sequence[ReadableBuffer] = (),
+            trailers: Sequence[ReadableBuffer] = (),
             flags: int = 0,
         ) -> int: ...  # FreeBSD and Mac OS X only
 
@@ -1195,7 +1197,7 @@ if sys.platform != "win32":
 
 def getcwd() -> str: ...
 def getcwdb() -> bytes: ...
-def chmod(path: FileDescriptorOrPath, mode: int, *, dir_fd: int | None = None, follow_symlinks: bool = ...) -> None: ...
+def chmod(path: FileDescriptorOrPath, mode: int, *, dir_fd: int | None = None, follow_symlinks: bool = True) -> None: ...
 
 if sys.platform != "win32" and sys.platform != "linux":
     def chflags(path: StrOrBytesPath, flags: int, follow_symlinks: bool = True) -> None: ...  # some flavors of Unix
@@ -1241,6 +1243,7 @@ def replace(
 ) -> None: ...
 def rmdir(path: StrOrBytesPath, *, dir_fd: int | None = None) -> None: ...
 @final
+@type_check_only
 class _ScandirIterator(Generic[AnyStr]):
     def __del__(self) -> None: ...
     def __iter__(self) -> Self: ...
@@ -1497,9 +1500,9 @@ else:
         setsigdef: Iterable[int] = ...,
         scheduler: tuple[Any, sched_param] | None = ...,
     ) -> int: ...
-    POSIX_SPAWN_OPEN: int
-    POSIX_SPAWN_CLOSE: int
-    POSIX_SPAWN_DUP2: int
+    POSIX_SPAWN_OPEN: Final = 0
+    POSIX_SPAWN_CLOSE: Final = 1
+    POSIX_SPAWN_DUP2: Final = 2
 
 if sys.platform != "win32":
     @final
@@ -1563,23 +1566,23 @@ if sys.platform == "win32":
     def add_dll_directory(path: str) -> _AddedDllDirectory: ...
 
 if sys.platform == "linux":
-    MFD_CLOEXEC: int
-    MFD_ALLOW_SEALING: int
-    MFD_HUGETLB: int
-    MFD_HUGE_SHIFT: int
-    MFD_HUGE_MASK: int
-    MFD_HUGE_64KB: int
-    MFD_HUGE_512KB: int
-    MFD_HUGE_1MB: int
-    MFD_HUGE_2MB: int
-    MFD_HUGE_8MB: int
-    MFD_HUGE_16MB: int
-    MFD_HUGE_32MB: int
-    MFD_HUGE_256MB: int
-    MFD_HUGE_512MB: int
-    MFD_HUGE_1GB: int
-    MFD_HUGE_2GB: int
-    MFD_HUGE_16GB: int
+    MFD_CLOEXEC: Final[int]
+    MFD_ALLOW_SEALING: Final[int]
+    MFD_HUGETLB: Final[int]
+    MFD_HUGE_SHIFT: Final[int]
+    MFD_HUGE_MASK: Final[int]
+    MFD_HUGE_64KB: Final[int]
+    MFD_HUGE_512KB: Final[int]
+    MFD_HUGE_1MB: Final[int]
+    MFD_HUGE_2MB: Final[int]
+    MFD_HUGE_8MB: Final[int]
+    MFD_HUGE_16MB: Final[int]
+    MFD_HUGE_32MB: Final[int]
+    MFD_HUGE_256MB: Final[int]
+    MFD_HUGE_512MB: Final[int]
+    MFD_HUGE_1GB: Final[int]
+    MFD_HUGE_2GB: Final[int]
+    MFD_HUGE_16GB: Final[int]
     def memfd_create(name: str, flags: int = ...) -> int: ...
     def copy_file_range(src: int, dst: int, count: int, offset_src: int | None = ..., offset_dst: int | None = ...) -> int: ...
 
@@ -1597,12 +1600,12 @@ if sys.version_info >= (3, 12) and sys.platform == "win32":
     def listvolumes() -> list[str]: ...
 
 if sys.version_info >= (3, 10) and sys.platform == "linux":
-    EFD_CLOEXEC: int
-    EFD_NONBLOCK: int
-    EFD_SEMAPHORE: int
-    SPLICE_F_MORE: int
-    SPLICE_F_MOVE: int
-    SPLICE_F_NONBLOCK: int
+    EFD_CLOEXEC: Final[int]
+    EFD_NONBLOCK: Final[int]
+    EFD_SEMAPHORE: Final[int]
+    SPLICE_F_MORE: Final[int]
+    SPLICE_F_MOVE: Final[int]
+    SPLICE_F_NONBLOCK: Final[int]
     def eventfd(initval: int, flags: int = 524288) -> FileDescriptor: ...
     def eventfd_read(fd: FileDescriptor) -> int: ...
     def eventfd_write(fd: FileDescriptor, value: int) -> None: ...
@@ -1616,20 +1619,20 @@ if sys.version_info >= (3, 10) and sys.platform == "linux":
     ) -> int: ...
 
 if sys.version_info >= (3, 12) and sys.platform == "linux":
-    CLONE_FILES: int
-    CLONE_FS: int
-    CLONE_NEWCGROUP: int  # Linux 4.6+
-    CLONE_NEWIPC: int  # Linux 2.6.19+
-    CLONE_NEWNET: int  # Linux 2.6.24+
-    CLONE_NEWNS: int
-    CLONE_NEWPID: int  # Linux 3.8+
-    CLONE_NEWTIME: int  # Linux 5.6+
-    CLONE_NEWUSER: int  # Linux 3.8+
-    CLONE_NEWUTS: int  # Linux 2.6.19+
-    CLONE_SIGHAND: int
-    CLONE_SYSVSEM: int  # Linux 2.6.26+
-    CLONE_THREAD: int
-    CLONE_VM: int
+    CLONE_FILES: Final[int]
+    CLONE_FS: Final[int]
+    CLONE_NEWCGROUP: Final[int]  # Linux 4.6+
+    CLONE_NEWIPC: Final[int]  # Linux 2.6.19+
+    CLONE_NEWNET: Final[int]  # Linux 2.6.24+
+    CLONE_NEWNS: Final[int]
+    CLONE_NEWPID: Final[int]  # Linux 3.8+
+    CLONE_NEWTIME: Final[int]  # Linux 5.6+
+    CLONE_NEWUSER: Final[int]  # Linux 3.8+
+    CLONE_NEWUTS: Final[int]  # Linux 2.6.19+
+    CLONE_SIGHAND: Final[int]
+    CLONE_SYSVSEM: Final[int]  # Linux 2.6.26+
+    CLONE_THREAD: Final[int]
+    CLONE_VM: Final[int]
     def unshare(flags: int) -> None: ...
     def setns(fd: FileDescriptorLike, nstype: int = 0) -> None: ...
 
diff --git a/mypy/typeshed/stdlib/ossaudiodev.pyi b/mypy/typeshed/stdlib/ossaudiodev.pyi
index b9ee3edab033..f8230b4f0212 100644
--- a/mypy/typeshed/stdlib/ossaudiodev.pyi
+++ b/mypy/typeshed/stdlib/ossaudiodev.pyi
@@ -1,119 +1,120 @@
 import sys
-from typing import Any, Literal, overload
+from typing import Any, Final, Literal, overload
 
 if sys.platform != "win32" and sys.platform != "darwin":
-    AFMT_AC3: int
-    AFMT_A_LAW: int
-    AFMT_IMA_ADPCM: int
-    AFMT_MPEG: int
-    AFMT_MU_LAW: int
-    AFMT_QUERY: int
-    AFMT_S16_BE: int
-    AFMT_S16_LE: int
-    AFMT_S16_NE: int
-    AFMT_S8: int
-    AFMT_U16_BE: int
-    AFMT_U16_LE: int
-    AFMT_U8: int
-    SNDCTL_COPR_HALT: int
-    SNDCTL_COPR_LOAD: int
-    SNDCTL_COPR_RCODE: int
-    SNDCTL_COPR_RCVMSG: int
-    SNDCTL_COPR_RDATA: int
-    SNDCTL_COPR_RESET: int
-    SNDCTL_COPR_RUN: int
-    SNDCTL_COPR_SENDMSG: int
-    SNDCTL_COPR_WCODE: int
-    SNDCTL_COPR_WDATA: int
-    SNDCTL_DSP_BIND_CHANNEL: int
-    SNDCTL_DSP_CHANNELS: int
-    SNDCTL_DSP_GETBLKSIZE: int
-    SNDCTL_DSP_GETCAPS: int
-    SNDCTL_DSP_GETCHANNELMASK: int
-    SNDCTL_DSP_GETFMTS: int
-    SNDCTL_DSP_GETIPTR: int
-    SNDCTL_DSP_GETISPACE: int
-    SNDCTL_DSP_GETODELAY: int
-    SNDCTL_DSP_GETOPTR: int
-    SNDCTL_DSP_GETOSPACE: int
-    SNDCTL_DSP_GETSPDIF: int
-    SNDCTL_DSP_GETTRIGGER: int
-    SNDCTL_DSP_MAPINBUF: int
-    SNDCTL_DSP_MAPOUTBUF: int
-    SNDCTL_DSP_NONBLOCK: int
-    SNDCTL_DSP_POST: int
-    SNDCTL_DSP_PROFILE: int
-    SNDCTL_DSP_RESET: int
-    SNDCTL_DSP_SAMPLESIZE: int
-    SNDCTL_DSP_SETDUPLEX: int
-    SNDCTL_DSP_SETFMT: int
-    SNDCTL_DSP_SETFRAGMENT: int
-    SNDCTL_DSP_SETSPDIF: int
-    SNDCTL_DSP_SETSYNCRO: int
-    SNDCTL_DSP_SETTRIGGER: int
-    SNDCTL_DSP_SPEED: int
-    SNDCTL_DSP_STEREO: int
-    SNDCTL_DSP_SUBDIVIDE: int
-    SNDCTL_DSP_SYNC: int
-    SNDCTL_FM_4OP_ENABLE: int
-    SNDCTL_FM_LOAD_INSTR: int
-    SNDCTL_MIDI_INFO: int
-    SNDCTL_MIDI_MPUCMD: int
-    SNDCTL_MIDI_MPUMODE: int
-    SNDCTL_MIDI_PRETIME: int
-    SNDCTL_SEQ_CTRLRATE: int
-    SNDCTL_SEQ_GETINCOUNT: int
-    SNDCTL_SEQ_GETOUTCOUNT: int
-    SNDCTL_SEQ_GETTIME: int
-    SNDCTL_SEQ_NRMIDIS: int
-    SNDCTL_SEQ_NRSYNTHS: int
-    SNDCTL_SEQ_OUTOFBAND: int
-    SNDCTL_SEQ_PANIC: int
-    SNDCTL_SEQ_PERCMODE: int
-    SNDCTL_SEQ_RESET: int
-    SNDCTL_SEQ_RESETSAMPLES: int
-    SNDCTL_SEQ_SYNC: int
-    SNDCTL_SEQ_TESTMIDI: int
-    SNDCTL_SEQ_THRESHOLD: int
-    SNDCTL_SYNTH_CONTROL: int
-    SNDCTL_SYNTH_ID: int
-    SNDCTL_SYNTH_INFO: int
-    SNDCTL_SYNTH_MEMAVL: int
-    SNDCTL_SYNTH_REMOVESAMPLE: int
-    SNDCTL_TMR_CONTINUE: int
-    SNDCTL_TMR_METRONOME: int
-    SNDCTL_TMR_SELECT: int
-    SNDCTL_TMR_SOURCE: int
-    SNDCTL_TMR_START: int
-    SNDCTL_TMR_STOP: int
-    SNDCTL_TMR_TEMPO: int
-    SNDCTL_TMR_TIMEBASE: int
-    SOUND_MIXER_ALTPCM: int
-    SOUND_MIXER_BASS: int
-    SOUND_MIXER_CD: int
-    SOUND_MIXER_DIGITAL1: int
-    SOUND_MIXER_DIGITAL2: int
-    SOUND_MIXER_DIGITAL3: int
-    SOUND_MIXER_IGAIN: int
-    SOUND_MIXER_IMIX: int
-    SOUND_MIXER_LINE: int
-    SOUND_MIXER_LINE1: int
-    SOUND_MIXER_LINE2: int
-    SOUND_MIXER_LINE3: int
-    SOUND_MIXER_MIC: int
-    SOUND_MIXER_MONITOR: int
-    SOUND_MIXER_NRDEVICES: int
-    SOUND_MIXER_OGAIN: int
-    SOUND_MIXER_PCM: int
-    SOUND_MIXER_PHONEIN: int
-    SOUND_MIXER_PHONEOUT: int
-    SOUND_MIXER_RADIO: int
-    SOUND_MIXER_RECLEV: int
-    SOUND_MIXER_SPEAKER: int
-    SOUND_MIXER_SYNTH: int
-    SOUND_MIXER_TREBLE: int
-    SOUND_MIXER_VIDEO: int
-    SOUND_MIXER_VOLUME: int
+    # Depends on soundcard.h
+    AFMT_AC3: Final[int]
+    AFMT_A_LAW: Final[int]
+    AFMT_IMA_ADPCM: Final[int]
+    AFMT_MPEG: Final[int]
+    AFMT_MU_LAW: Final[int]
+    AFMT_QUERY: Final[int]
+    AFMT_S16_BE: Final[int]
+    AFMT_S16_LE: Final[int]
+    AFMT_S16_NE: Final[int]
+    AFMT_S8: Final[int]
+    AFMT_U16_BE: Final[int]
+    AFMT_U16_LE: Final[int]
+    AFMT_U8: Final[int]
+    SNDCTL_COPR_HALT: Final[int]
+    SNDCTL_COPR_LOAD: Final[int]
+    SNDCTL_COPR_RCODE: Final[int]
+    SNDCTL_COPR_RCVMSG: Final[int]
+    SNDCTL_COPR_RDATA: Final[int]
+    SNDCTL_COPR_RESET: Final[int]
+    SNDCTL_COPR_RUN: Final[int]
+    SNDCTL_COPR_SENDMSG: Final[int]
+    SNDCTL_COPR_WCODE: Final[int]
+    SNDCTL_COPR_WDATA: Final[int]
+    SNDCTL_DSP_BIND_CHANNEL: Final[int]
+    SNDCTL_DSP_CHANNELS: Final[int]
+    SNDCTL_DSP_GETBLKSIZE: Final[int]
+    SNDCTL_DSP_GETCAPS: Final[int]
+    SNDCTL_DSP_GETCHANNELMASK: Final[int]
+    SNDCTL_DSP_GETFMTS: Final[int]
+    SNDCTL_DSP_GETIPTR: Final[int]
+    SNDCTL_DSP_GETISPACE: Final[int]
+    SNDCTL_DSP_GETODELAY: Final[int]
+    SNDCTL_DSP_GETOPTR: Final[int]
+    SNDCTL_DSP_GETOSPACE: Final[int]
+    SNDCTL_DSP_GETSPDIF: Final[int]
+    SNDCTL_DSP_GETTRIGGER: Final[int]
+    SNDCTL_DSP_MAPINBUF: Final[int]
+    SNDCTL_DSP_MAPOUTBUF: Final[int]
+    SNDCTL_DSP_NONBLOCK: Final[int]
+    SNDCTL_DSP_POST: Final[int]
+    SNDCTL_DSP_PROFILE: Final[int]
+    SNDCTL_DSP_RESET: Final[int]
+    SNDCTL_DSP_SAMPLESIZE: Final[int]
+    SNDCTL_DSP_SETDUPLEX: Final[int]
+    SNDCTL_DSP_SETFMT: Final[int]
+    SNDCTL_DSP_SETFRAGMENT: Final[int]
+    SNDCTL_DSP_SETSPDIF: Final[int]
+    SNDCTL_DSP_SETSYNCRO: Final[int]
+    SNDCTL_DSP_SETTRIGGER: Final[int]
+    SNDCTL_DSP_SPEED: Final[int]
+    SNDCTL_DSP_STEREO: Final[int]
+    SNDCTL_DSP_SUBDIVIDE: Final[int]
+    SNDCTL_DSP_SYNC: Final[int]
+    SNDCTL_FM_4OP_ENABLE: Final[int]
+    SNDCTL_FM_LOAD_INSTR: Final[int]
+    SNDCTL_MIDI_INFO: Final[int]
+    SNDCTL_MIDI_MPUCMD: Final[int]
+    SNDCTL_MIDI_MPUMODE: Final[int]
+    SNDCTL_MIDI_PRETIME: Final[int]
+    SNDCTL_SEQ_CTRLRATE: Final[int]
+    SNDCTL_SEQ_GETINCOUNT: Final[int]
+    SNDCTL_SEQ_GETOUTCOUNT: Final[int]
+    SNDCTL_SEQ_GETTIME: Final[int]
+    SNDCTL_SEQ_NRMIDIS: Final[int]
+    SNDCTL_SEQ_NRSYNTHS: Final[int]
+    SNDCTL_SEQ_OUTOFBAND: Final[int]
+    SNDCTL_SEQ_PANIC: Final[int]
+    SNDCTL_SEQ_PERCMODE: Final[int]
+    SNDCTL_SEQ_RESET: Final[int]
+    SNDCTL_SEQ_RESETSAMPLES: Final[int]
+    SNDCTL_SEQ_SYNC: Final[int]
+    SNDCTL_SEQ_TESTMIDI: Final[int]
+    SNDCTL_SEQ_THRESHOLD: Final[int]
+    SNDCTL_SYNTH_CONTROL: Final[int]
+    SNDCTL_SYNTH_ID: Final[int]
+    SNDCTL_SYNTH_INFO: Final[int]
+    SNDCTL_SYNTH_MEMAVL: Final[int]
+    SNDCTL_SYNTH_REMOVESAMPLE: Final[int]
+    SNDCTL_TMR_CONTINUE: Final[int]
+    SNDCTL_TMR_METRONOME: Final[int]
+    SNDCTL_TMR_SELECT: Final[int]
+    SNDCTL_TMR_SOURCE: Final[int]
+    SNDCTL_TMR_START: Final[int]
+    SNDCTL_TMR_STOP: Final[int]
+    SNDCTL_TMR_TEMPO: Final[int]
+    SNDCTL_TMR_TIMEBASE: Final[int]
+    SOUND_MIXER_ALTPCM: Final[int]
+    SOUND_MIXER_BASS: Final[int]
+    SOUND_MIXER_CD: Final[int]
+    SOUND_MIXER_DIGITAL1: Final[int]
+    SOUND_MIXER_DIGITAL2: Final[int]
+    SOUND_MIXER_DIGITAL3: Final[int]
+    SOUND_MIXER_IGAIN: Final[int]
+    SOUND_MIXER_IMIX: Final[int]
+    SOUND_MIXER_LINE: Final[int]
+    SOUND_MIXER_LINE1: Final[int]
+    SOUND_MIXER_LINE2: Final[int]
+    SOUND_MIXER_LINE3: Final[int]
+    SOUND_MIXER_MIC: Final[int]
+    SOUND_MIXER_MONITOR: Final[int]
+    SOUND_MIXER_NRDEVICES: Final[int]
+    SOUND_MIXER_OGAIN: Final[int]
+    SOUND_MIXER_PCM: Final[int]
+    SOUND_MIXER_PHONEIN: Final[int]
+    SOUND_MIXER_PHONEOUT: Final[int]
+    SOUND_MIXER_RADIO: Final[int]
+    SOUND_MIXER_RECLEV: Final[int]
+    SOUND_MIXER_SPEAKER: Final[int]
+    SOUND_MIXER_SYNTH: Final[int]
+    SOUND_MIXER_TREBLE: Final[int]
+    SOUND_MIXER_VIDEO: Final[int]
+    SOUND_MIXER_VOLUME: Final[int]
 
     control_labels: list[str]
     control_names: list[str]
diff --git a/mypy/typeshed/stdlib/pathlib/__init__.pyi b/mypy/typeshed/stdlib/pathlib/__init__.pyi
index b84fc69313a1..fa5143f20292 100644
--- a/mypy/typeshed/stdlib/pathlib/__init__.pyi
+++ b/mypy/typeshed/stdlib/pathlib/__init__.pyi
@@ -29,6 +29,31 @@ if sys.version_info >= (3, 13):
     __all__ += ["UnsupportedOperation"]
 
 class PurePath(PathLike[str]):
+    if sys.version_info >= (3, 13):
+        __slots__ = (
+            "_raw_paths",
+            "_drv",
+            "_root",
+            "_tail_cached",
+            "_str",
+            "_str_normcase_cached",
+            "_parts_normcase_cached",
+            "_hash",
+        )
+    elif sys.version_info >= (3, 12):
+        __slots__ = (
+            "_raw_paths",
+            "_drv",
+            "_root",
+            "_tail_cached",
+            "_str",
+            "_str_normcase_cached",
+            "_parts_normcase_cached",
+            "_lines_cached",
+            "_hash",
+        )
+    else:
+        __slots__ = ("_drv", "_root", "_parts", "_str", "_hash", "_pparts", "_cached_cparts")
     if sys.version_info >= (3, 13):
         parser: ClassVar[types.ModuleType]
         def full_match(self, pattern: StrPath, *, case_sensitive: bool | None = None) -> bool: ...
@@ -67,7 +92,14 @@ class PurePath(PathLike[str]):
     def as_posix(self) -> str: ...
     def as_uri(self) -> str: ...
     def is_absolute(self) -> bool: ...
-    def is_reserved(self) -> bool: ...
+    if sys.version_info >= (3, 13):
+        @deprecated(
+            "Deprecated since Python 3.13; will be removed in Python 3.15. "
+            "Use `os.path.isreserved()` to detect reserved paths on Windows."
+        )
+        def is_reserved(self) -> bool: ...
+    else:
+        def is_reserved(self) -> bool: ...
     if sys.version_info >= (3, 14):
         def is_relative_to(self, other: StrPath) -> bool: ...
     elif sys.version_info >= (3, 12):
@@ -101,10 +133,20 @@ class PurePath(PathLike[str]):
     if sys.version_info >= (3, 12):
         def with_segments(self, *args: StrPath) -> Self: ...
 
-class PurePosixPath(PurePath): ...
-class PureWindowsPath(PurePath): ...
+class PurePosixPath(PurePath):
+    __slots__ = ()
+
+class PureWindowsPath(PurePath):
+    __slots__ = ()
 
 class Path(PurePath):
+    if sys.version_info >= (3, 14):
+        __slots__ = ("_info",)
+    elif sys.version_info >= (3, 10):
+        __slots__ = ()
+    else:
+        __slots__ = ("_accessor",)
+
     if sys.version_info >= (3, 12):
         def __new__(cls, *args: StrPath, **kwargs: Unused) -> Self: ...  # pyright: ignore[reportInconsistentConstructor]
     else:
@@ -163,7 +205,6 @@ class Path(PurePath):
     def mkdir(self, mode: int = 0o777, parents: bool = False, exist_ok: bool = False) -> None: ...
 
     if sys.version_info >= (3, 14):
-
         @property
         def info(self) -> PathInfo: ...
         @overload
@@ -239,9 +280,13 @@ class Path(PurePath):
         self, mode: str, buffering: int = -1, encoding: str | None = None, errors: str | None = None, newline: str | None = None
     ) -> IO[Any]: ...
 
-    # These methods do "exist" on Windows on <3.13, but they always raise NotImplementedError.
+    # These methods do "exist" on Windows, but they always raise NotImplementedError.
     if sys.platform == "win32":
-        if sys.version_info < (3, 13):
+        if sys.version_info >= (3, 13):
+            # raises UnsupportedOperation:
+            def owner(self: Never, *, follow_symlinks: bool = True) -> str: ...  # type: ignore[misc]
+            def group(self: Never, *, follow_symlinks: bool = True) -> str: ...  # type: ignore[misc]
+        else:
             def owner(self: Never) -> str: ...  # type: ignore[misc]
             def group(self: Never) -> str: ...  # type: ignore[misc]
     else:
@@ -291,17 +336,20 @@ class Path(PurePath):
         def write_text(self, data: str, encoding: str | None = None, errors: str | None = None) -> int: ...
     if sys.version_info < (3, 12):
         if sys.version_info >= (3, 10):
-            @deprecated("Deprecated as of Python 3.10 and removed in Python 3.12. Use hardlink_to() instead.")
+            @deprecated("Deprecated since Python 3.10; removed in Python 3.12. Use `hardlink_to()` instead.")
             def link_to(self, target: StrOrBytesPath) -> None: ...
         else:
             def link_to(self, target: StrOrBytesPath) -> None: ...
     if sys.version_info >= (3, 12):
         def walk(
-            self, top_down: bool = ..., on_error: Callable[[OSError], object] | None = ..., follow_symlinks: bool = ...
+            self, top_down: bool = True, on_error: Callable[[OSError], object] | None = None, follow_symlinks: bool = False
         ) -> Iterator[tuple[Self, list[str], list[str]]]: ...
 
-class PosixPath(Path, PurePosixPath): ...
-class WindowsPath(Path, PureWindowsPath): ...
+class PosixPath(Path, PurePosixPath):
+    __slots__ = ()
+
+class WindowsPath(Path, PureWindowsPath):
+    __slots__ = ()
 
 if sys.version_info >= (3, 13):
     class UnsupportedOperation(NotImplementedError): ...
diff --git a/mypy/typeshed/stdlib/pdb.pyi b/mypy/typeshed/stdlib/pdb.pyi
index ad69fcab16de..0c16f48e2e22 100644
--- a/mypy/typeshed/stdlib/pdb.pyi
+++ b/mypy/typeshed/stdlib/pdb.pyi
@@ -17,7 +17,7 @@ _T = TypeVar("_T")
 _P = ParamSpec("_P")
 _Mode: TypeAlias = Literal["inline", "cli"]
 
-line_prefix: str  # undocumented
+line_prefix: Final[str]  # undocumented
 
 class Restart(Exception): ...
 
@@ -131,7 +131,11 @@ class Pdb(Bdb, Cmd):
         def completedefault(self, text: str, line: str, begidx: int, endidx: int) -> list[str]: ...
 
     def do_commands(self, arg: str) -> bool | None: ...
-    def do_break(self, arg: str, temporary: bool = ...) -> bool | None: ...
+    if sys.version_info >= (3, 14):
+        def do_break(self, arg: str, temporary: bool = False) -> bool | None: ...
+    else:
+        def do_break(self, arg: str, temporary: bool | Literal[0, 1] = 0) -> bool | None: ...
+
     def do_tbreak(self, arg: str) -> bool | None: ...
     def do_enable(self, arg: str) -> bool | None: ...
     def do_disable(self, arg: str) -> bool | None: ...
diff --git a/mypy/typeshed/stdlib/pickle.pyi b/mypy/typeshed/stdlib/pickle.pyi
index 2d80d61645e0..d94fe208f446 100644
--- a/mypy/typeshed/stdlib/pickle.pyi
+++ b/mypy/typeshed/stdlib/pickle.pyi
@@ -14,7 +14,7 @@ from _pickle import (
 )
 from _typeshed import ReadableBuffer, SupportsWrite
 from collections.abc import Callable, Iterable, Mapping
-from typing import Any, ClassVar, SupportsBytes, SupportsIndex, final
+from typing import Any, ClassVar, Final, SupportsBytes, SupportsIndex, final
 from typing_extensions import Self
 
 __all__ = [
@@ -102,8 +102,8 @@ __all__ = [
     "UNICODE",
 ]
 
-HIGHEST_PROTOCOL: int
-DEFAULT_PROTOCOL: int
+HIGHEST_PROTOCOL: Final = 5
+DEFAULT_PROTOCOL: Final = 5
 
 bytes_types: tuple[type[Any], ...]  # undocumented
 
@@ -115,85 +115,85 @@ class PickleBuffer:
     def __buffer__(self, flags: int, /) -> memoryview: ...
     def __release_buffer__(self, buffer: memoryview, /) -> None: ...
 
-MARK: bytes
-STOP: bytes
-POP: bytes
-POP_MARK: bytes
-DUP: bytes
-FLOAT: bytes
-INT: bytes
-BININT: bytes
-BININT1: bytes
-LONG: bytes
-BININT2: bytes
-NONE: bytes
-PERSID: bytes
-BINPERSID: bytes
-REDUCE: bytes
-STRING: bytes
-BINSTRING: bytes
-SHORT_BINSTRING: bytes
-UNICODE: bytes
-BINUNICODE: bytes
-APPEND: bytes
-BUILD: bytes
-GLOBAL: bytes
-DICT: bytes
-EMPTY_DICT: bytes
-APPENDS: bytes
-GET: bytes
-BINGET: bytes
-INST: bytes
-LONG_BINGET: bytes
-LIST: bytes
-EMPTY_LIST: bytes
-OBJ: bytes
-PUT: bytes
-BINPUT: bytes
-LONG_BINPUT: bytes
-SETITEM: bytes
-TUPLE: bytes
-EMPTY_TUPLE: bytes
-SETITEMS: bytes
-BINFLOAT: bytes
+MARK: Final = b"("
+STOP: Final = b"."
+POP: Final = b"0"
+POP_MARK: Final = b"1"
+DUP: Final = b"2"
+FLOAT: Final = b"F"
+INT: Final = b"I"
+BININT: Final = b"J"
+BININT1: Final = b"K"
+LONG: Final = b"L"
+BININT2: Final = b"M"
+NONE: Final = b"N"
+PERSID: Final = b"P"
+BINPERSID: Final = b"Q"
+REDUCE: Final = b"R"
+STRING: Final = b"S"
+BINSTRING: Final = b"T"
+SHORT_BINSTRING: Final = b"U"
+UNICODE: Final = b"V"
+BINUNICODE: Final = b"X"
+APPEND: Final = b"a"
+BUILD: Final = b"b"
+GLOBAL: Final = b"c"
+DICT: Final = b"d"
+EMPTY_DICT: Final = b"}"
+APPENDS: Final = b"e"
+GET: Final = b"g"
+BINGET: Final = b"h"
+INST: Final = b"i"
+LONG_BINGET: Final = b"j"
+LIST: Final = b"l"
+EMPTY_LIST: Final = b"]"
+OBJ: Final = b"o"
+PUT: Final = b"p"
+BINPUT: Final = b"q"
+LONG_BINPUT: Final = b"r"
+SETITEM: Final = b"s"
+TUPLE: Final = b"t"
+EMPTY_TUPLE: Final = b")"
+SETITEMS: Final = b"u"
+BINFLOAT: Final = b"G"
 
-TRUE: bytes
-FALSE: bytes
+TRUE: Final = b"I01\n"
+FALSE: Final = b"I00\n"
 
 # protocol 2
-PROTO: bytes
-NEWOBJ: bytes
-EXT1: bytes
-EXT2: bytes
-EXT4: bytes
-TUPLE1: bytes
-TUPLE2: bytes
-TUPLE3: bytes
-NEWTRUE: bytes
-NEWFALSE: bytes
-LONG1: bytes
-LONG4: bytes
+PROTO: Final = b"\x80"
+NEWOBJ: Final = b"\x81"
+EXT1: Final = b"\x82"
+EXT2: Final = b"\x83"
+EXT4: Final = b"\x84"
+TUPLE1: Final = b"\x85"
+TUPLE2: Final = b"\x86"
+TUPLE3: Final = b"\x87"
+NEWTRUE: Final = b"\x88"
+NEWFALSE: Final = b"\x89"
+LONG1: Final = b"\x8a"
+LONG4: Final = b"\x8b"
 
 # protocol 3
-BINBYTES: bytes
-SHORT_BINBYTES: bytes
+BINBYTES: Final = b"B"
+SHORT_BINBYTES: Final = b"C"
 
 # protocol 4
-SHORT_BINUNICODE: bytes
-BINUNICODE8: bytes
-BINBYTES8: bytes
-EMPTY_SET: bytes
-ADDITEMS: bytes
-FROZENSET: bytes
-NEWOBJ_EX: bytes
-STACK_GLOBAL: bytes
-MEMOIZE: bytes
-FRAME: bytes
+SHORT_BINUNICODE: Final = b"\x8c"
+BINUNICODE8: Final = b"\x8d"
+BINBYTES8: Final = b"\x8e"
+EMPTY_SET: Final = b"\x8f"
+ADDITEMS: Final = b"\x90"
+FROZENSET: Final = b"\x91"
+NEWOBJ_EX: Final = b"\x92"
+STACK_GLOBAL: Final = b"\x93"
+MEMOIZE: Final = b"\x94"
+FRAME: Final = b"\x95"
 
 # protocol 5
-BYTEARRAY8: bytes
-NEXT_BUFFER: bytes
-READONLY_BUFFER: bytes
+BYTEARRAY8: Final = b"\x96"
+NEXT_BUFFER: Final = b"\x97"
+READONLY_BUFFER: Final = b"\x98"
 
 def encode_long(x: int) -> bytes: ...  # undocumented
 def decode_long(data: Iterable[SupportsIndex] | SupportsBytes | ReadableBuffer) -> int: ...  # undocumented
diff --git a/mypy/typeshed/stdlib/pickletools.pyi b/mypy/typeshed/stdlib/pickletools.pyi
index cdade08d39a8..8bbfaba31b67 100644
--- a/mypy/typeshed/stdlib/pickletools.pyi
+++ b/mypy/typeshed/stdlib/pickletools.pyi
@@ -1,6 +1,6 @@
 import sys
 from collections.abc import Callable, Iterator, MutableMapping
-from typing import IO, Any
+from typing import IO, Any, Final
 from typing_extensions import TypeAlias
 
 __all__ = ["dis", "genops", "optimize"]
@@ -8,13 +8,14 @@ __all__ = ["dis", "genops", "optimize"]
 _Reader: TypeAlias = Callable[[IO[bytes]], Any]
 bytes_types: tuple[type[Any], ...]
 
-UP_TO_NEWLINE: int
-TAKEN_FROM_ARGUMENT1: int
-TAKEN_FROM_ARGUMENT4: int
-TAKEN_FROM_ARGUMENT4U: int
-TAKEN_FROM_ARGUMENT8U: int
+UP_TO_NEWLINE: Final = -1
+TAKEN_FROM_ARGUMENT1: Final = -2
+TAKEN_FROM_ARGUMENT4: Final = -3
+TAKEN_FROM_ARGUMENT4U: Final = -4
+TAKEN_FROM_ARGUMENT8U: Final = -5
 
 class ArgumentDescriptor:
+    __slots__ = ("name", "n", "reader", "doc")
     name: str
     n: int
     reader: _Reader
@@ -118,6 +119,7 @@ def read_long4(f: IO[bytes]) -> int: ...
 long4: ArgumentDescriptor
 
 class StackObject:
+    __slots__ = ("name", "obtype", "doc")
     name: str
     obtype: type[Any] | tuple[type[Any], ...]
     doc: str
@@ -143,6 +145,7 @@ markobject: StackObject
 stackslice: StackObject
 
 class OpcodeInfo:
+    __slots__ = ("name", "code", "arg", "stack_before", "stack_after", "proto", "doc")
     name: str
     code: str
     arg: ArgumentDescriptor | None
diff --git a/mypy/typeshed/stdlib/pkgutil.pyi b/mypy/typeshed/stdlib/pkgutil.pyi
index e764d08e79f8..7c70dcc4c5ab 100644
--- a/mypy/typeshed/stdlib/pkgutil.pyi
+++ b/mypy/typeshed/stdlib/pkgutil.pyi
@@ -30,17 +30,23 @@ class ModuleInfo(NamedTuple):
 def extend_path(path: _PathT, name: str) -> _PathT: ...
 
 if sys.version_info < (3, 12):
+    @deprecated("Deprecated since Python 3.3; removed in Python 3.12. Use the `importlib` module instead.")
     class ImpImporter:
         def __init__(self, path: StrOrBytesPath | None = None) -> None: ...
 
+    @deprecated("Deprecated since Python 3.3; removed in Python 3.12. Use the `importlib` module instead.")
     class ImpLoader:
         def __init__(self, fullname: str, file: IO[str], filename: StrOrBytesPath, etc: tuple[str, str, int]) -> None: ...
 
 if sys.version_info < (3, 14):
-    @deprecated("Use importlib.util.find_spec() instead. Will be removed in Python 3.14.")
-    def find_loader(fullname: str) -> LoaderProtocol | None: ...
-    @deprecated("Use importlib.util.find_spec() instead. Will be removed in Python 3.14.")
-    def get_loader(module_or_name: str) -> LoaderProtocol | None: ...
+    if sys.version_info >= (3, 12):
+        @deprecated("Deprecated since Python 3.12; removed in Python 3.14. Use `importlib.util.find_spec()` instead.")
+        def find_loader(fullname: str) -> LoaderProtocol | None: ...
+        @deprecated("Deprecated since Python 3.12; removed in Python 3.14. Use `importlib.util.find_spec()` instead.")
+        def get_loader(module_or_name: str) -> LoaderProtocol | None: ...
+    else:
+        def find_loader(fullname: str) -> LoaderProtocol | None: ...
+        def get_loader(module_or_name: str) -> LoaderProtocol | None: ...
 
 def get_importer(path_item: StrOrBytesPath) -> PathEntryFinderProtocol | None: ...
 def iter_importers(fullname: str = "") -> Iterator[MetaPathFinderProtocol | PathEntryFinderProtocol]: ...
diff --git a/mypy/typeshed/stdlib/platform.pyi b/mypy/typeshed/stdlib/platform.pyi
index fbc73c6c9177..69d702bb155c 100644
--- a/mypy/typeshed/stdlib/platform.pyi
+++ b/mypy/typeshed/stdlib/platform.pyi
@@ -1,6 +1,6 @@
 import sys
 from typing import NamedTuple, type_check_only
-from typing_extensions import Self
+from typing_extensions import Self, deprecated, disjoint_base
 
 def libc_ver(executable: str | None = None, lib: str = "", version: str = "", chunksize: int = 16384) -> tuple[str, str]: ...
 def win32_ver(release: str = "", version: str = "", csd: str = "", ptype: str = "") -> tuple[str, str, str, str]: ...
@@ -9,9 +9,24 @@ def win32_is_iot() -> bool: ...
 def mac_ver(
     release: str = "", versioninfo: tuple[str, str, str] = ("", "", ""), machine: str = ""
 ) -> tuple[str, tuple[str, str, str], str]: ...
-def java_ver(
-    release: str = "", vendor: str = "", vminfo: tuple[str, str, str] = ("", "", ""), osinfo: tuple[str, str, str] = ("", "", "")
-) -> tuple[str, str, tuple[str, str, str], tuple[str, str, str]]: ...
+
+if sys.version_info >= (3, 13):
+    @deprecated("Deprecated since Python 3.13; will be removed in Python 3.15.")
+    def java_ver(
+        release: str = "",
+        vendor: str = "",
+        vminfo: tuple[str, str, str] = ("", "", ""),
+        osinfo: tuple[str, str, str] = ("", "", ""),
+    ) -> tuple[str, str, tuple[str, str, str], tuple[str, str, str]]: ...
+
+else:
+    def java_ver(
+        release: str = "",
+        vendor: str = "",
+        vminfo: tuple[str, str, str] = ("", "", ""),
+        osinfo: tuple[str, str, str] = ("", "", ""),
+    ) -> tuple[str, str, tuple[str, str, str], tuple[str, str, str]]: ...
+
 def system_alias(system: str, release: str, version: str) -> tuple[str, str, str]: ...
 def architecture(executable: str = sys.executable, bits: str = "", linkage: str = "") -> tuple[str, str]: ...
 
@@ -31,13 +46,23 @@ class _uname_result_base(NamedTuple):
 
 # uname_result emulates a 6-field named tuple, but the processor field
 # is lazily evaluated rather than being passed in to the constructor.
-class uname_result(_uname_result_base):
-    if sys.version_info >= (3, 10):
+if sys.version_info >= (3, 12):
+    class uname_result(_uname_result_base):
         __match_args__ = ("system", "node", "release", "version", "machine")  # pyright: ignore[reportAssignmentType]
 
-    def __new__(_cls, system: str, node: str, release: str, version: str, machine: str) -> Self: ...
-    @property
-    def processor(self) -> str: ...
+        def __new__(_cls, system: str, node: str, release: str, version: str, machine: str) -> Self: ...
+        @property
+        def processor(self) -> str: ...
+
+else:
+    @disjoint_base
+    class uname_result(_uname_result_base):
+        if sys.version_info >= (3, 10):
+            __match_args__ = ("system", "node", "release", "version", "machine")  # pyright: ignore[reportAssignmentType]
+
+        def __new__(_cls, system: str, node: str, release: str, version: str, machine: str) -> Self: ...
+        @property
+        def processor(self) -> str: ...
 
 def uname() -> uname_result: ...
 def system() -> str: ...
@@ -53,7 +78,7 @@ def python_branch() -> str: ...
 def python_revision() -> str: ...
 def python_build() -> tuple[str, str]: ...
 def python_compiler() -> str: ...
-def platform(aliased: bool = ..., terse: bool = ...) -> str: ...
+def platform(aliased: bool = False, terse: bool = False) -> str: ...
 
 if sys.version_info >= (3, 10):
     def freedesktop_os_release() -> dict[str, str]: ...
diff --git a/mypy/typeshed/stdlib/plistlib.pyi b/mypy/typeshed/stdlib/plistlib.pyi
index 8b39b4217eae..dc3247ee47fb 100644
--- a/mypy/typeshed/stdlib/plistlib.pyi
+++ b/mypy/typeshed/stdlib/plistlib.pyi
@@ -3,7 +3,7 @@ from _typeshed import ReadableBuffer
 from collections.abc import Mapping, MutableMapping
 from datetime import datetime
 from enum import Enum
-from typing import IO, Any
+from typing import IO, Any, Final
 from typing_extensions import Self
 
 __all__ = ["InvalidFileException", "FMT_XML", "FMT_BINARY", "load", "dump", "loads", "dumps", "UID"]
@@ -12,8 +12,8 @@ class PlistFormat(Enum):
     FMT_XML = 1
     FMT_BINARY = 2
 
-FMT_XML = PlistFormat.FMT_XML
-FMT_BINARY = PlistFormat.FMT_BINARY
+FMT_XML: Final = PlistFormat.FMT_XML
+FMT_BINARY: Final = PlistFormat.FMT_BINARY
 if sys.version_info >= (3, 13):
     def load(
         fp: IO[bytes],
diff --git a/mypy/typeshed/stdlib/poplib.pyi b/mypy/typeshed/stdlib/poplib.pyi
index a1e41be86a7f..9ff2b764aeb6 100644
--- a/mypy/typeshed/stdlib/poplib.pyi
+++ b/mypy/typeshed/stdlib/poplib.pyi
@@ -17,7 +17,7 @@ POP3_SSL_PORT: Final = 995
 CR: Final = b"\r"
 LF: Final = b"\n"
 CRLF: Final = b"\r\n"
-HAVE_SSL: bool
+HAVE_SSL: Final[bool]
 
 class POP3:
     encoding: str
diff --git a/mypy/typeshed/stdlib/posixpath.pyi b/mypy/typeshed/stdlib/posixpath.pyi
index 3313667f1781..84e1b1e028bd 100644
--- a/mypy/typeshed/stdlib/posixpath.pyi
+++ b/mypy/typeshed/stdlib/posixpath.pyi
@@ -2,6 +2,8 @@ import sys
 from _typeshed import AnyOrLiteralStr, BytesPath, FileDescriptorOrPath, StrOrBytesPath, StrPath
 from collections.abc import Iterable
 from genericpath import (
+    ALLOW_MISSING as ALLOW_MISSING,
+    _AllowMissingType,
     commonprefix as commonprefix,
     exists as exists,
     getatime as getatime,
@@ -61,6 +63,7 @@ __all__ = [
     "relpath",
     "commonpath",
 ]
+__all__ += ["ALLOW_MISSING"]
 if sys.version_info >= (3, 12):
     __all__ += ["isjunction", "splitroot"]
 if sys.version_info >= (3, 13):
@@ -122,19 +125,10 @@ def join(a: LiteralString, /, *paths: LiteralString) -> LiteralString: ...
 def join(a: StrPath, /, *paths: StrPath) -> str: ...
 @overload
 def join(a: BytesPath, /, *paths: BytesPath) -> bytes: ...
-
-if sys.version_info >= (3, 10):
-    @overload
-    def realpath(filename: PathLike[AnyStr], *, strict: bool = False) -> AnyStr: ...
-    @overload
-    def realpath(filename: AnyStr, *, strict: bool = False) -> AnyStr: ...
-
-else:
-    @overload
-    def realpath(filename: PathLike[AnyStr]) -> AnyStr: ...
-    @overload
-    def realpath(filename: AnyStr) -> AnyStr: ...
-
+@overload
+def realpath(filename: PathLike[AnyStr], *, strict: bool | _AllowMissingType = False) -> AnyStr: ...
+@overload
+def realpath(filename: AnyStr, *, strict: bool | _AllowMissingType = False) -> AnyStr: ...
 @overload
 def relpath(path: LiteralString, start: LiteralString | None = None) -> LiteralString: ...
 @overload
diff --git a/mypy/typeshed/stdlib/pprint.pyi b/mypy/typeshed/stdlib/pprint.pyi
index 171878f4165d..1e80462e2565 100644
--- a/mypy/typeshed/stdlib/pprint.pyi
+++ b/mypy/typeshed/stdlib/pprint.pyi
@@ -1,4 +1,6 @@
 import sys
+from _typeshed import SupportsWrite
+from collections import deque
 from typing import IO
 
 __all__ = ["pprint", "pformat", "isreadable", "isrecursive", "saferepr", "PrettyPrinter", "pp"]
@@ -29,25 +31,25 @@ else:
 if sys.version_info >= (3, 10):
     def pp(
         object: object,
-        stream: IO[str] | None = ...,
-        indent: int = ...,
-        width: int = ...,
-        depth: int | None = ...,
+        stream: IO[str] | None = None,
+        indent: int = 1,
+        width: int = 80,
+        depth: int | None = None,
         *,
-        compact: bool = ...,
+        compact: bool = False,
         sort_dicts: bool = False,
-        underscore_numbers: bool = ...,
+        underscore_numbers: bool = False,
     ) -> None: ...
 
 else:
     def pp(
         object: object,
-        stream: IO[str] | None = ...,
-        indent: int = ...,
-        width: int = ...,
-        depth: int | None = ...,
+        stream: IO[str] | None = None,
+        indent: int = 1,
+        width: int = 80,
+        depth: int | None = None,
         *,
-        compact: bool = ...,
+        compact: bool = False,
         sort_dicts: bool = False,
     ) -> None: ...
 
@@ -110,3 +112,48 @@ class PrettyPrinter:
     def isreadable(self, object: object) -> bool: ...
     def isrecursive(self, object: object) -> bool: ...
     def format(self, object: object, context: dict[int, int], maxlevels: int, level: int) -> tuple[str, bool, bool]: ...
+    def _format(
+        self, object: object, stream: SupportsWrite[str], indent: int, allowance: int, context: dict[int, int], level: int
+    ) -> None: ...
+    def _pprint_dict(
+        self,
+        object: dict[object, object],
+        stream: SupportsWrite[str],
+        indent: int,
+        allowance: int,
+        context: dict[int, int],
+        level: int,
+    ) -> None: ...
+    def _pprint_list(
+        self, object: list[object], stream: SupportsWrite[str], indent: int, allowance: int, context: dict[int, int], level: int
+    ) -> None: ...
+    def _pprint_tuple(
+        self,
+        object: tuple[object, ...],
+        stream: SupportsWrite[str],
+        indent: int,
+        allowance: int,
+        context: dict[int, int],
+        level: int,
+    ) -> None: ...
+    def _pprint_set(
+        self, object: set[object], stream: SupportsWrite[str], indent: int, allowance: int, context: dict[int, int], level: int
+    ) -> None: ...
+    def _pprint_deque(
+        self, object: deque[object], stream: SupportsWrite[str], indent: int, allowance: int, context: dict[int, int], level: int
+    ) -> None: ...
+    def _format_dict_items(
+        self,
+        items: list[tuple[object, object]],
+        stream: SupportsWrite[str],
+        indent: int,
+        allowance: int,
+        context: dict[int, int],
+        level: int,
+    ) -> None: ...
+    def _format_items(
+        self, items: list[object], stream: SupportsWrite[str], indent: int, allowance: int, context: dict[int, int], level: int
+    ) -> None: ...
+    def _repr(self, object: object, context: dict[int, int], level: int) -> str: ...
+    if sys.version_info >= (3, 10):
+        def _safe_repr(self, object: object, context: dict[int, int], maxlevels: int, level: int) -> tuple[str, bool, bool]: ...
diff --git a/mypy/typeshed/stdlib/pty.pyi b/mypy/typeshed/stdlib/pty.pyi
index 941915179c4a..d1c78f9e3dd6 100644
--- a/mypy/typeshed/stdlib/pty.pyi
+++ b/mypy/typeshed/stdlib/pty.pyi
@@ -15,10 +15,14 @@ if sys.platform != "win32":
     def openpty() -> tuple[int, int]: ...
 
     if sys.version_info < (3, 14):
-        @deprecated("Deprecated in 3.12, to be removed in 3.14; use openpty() instead")
-        def master_open() -> tuple[int, str]: ...
-        @deprecated("Deprecated in 3.12, to be removed in 3.14; use openpty() instead")
-        def slave_open(tty_name: str) -> int: ...
+        if sys.version_info >= (3, 12):
+            @deprecated("Deprecated since Python 3.12; removed in Python 3.14. Use `openpty()` instead.")
+            def master_open() -> tuple[int, str]: ...
+            @deprecated("Deprecated since Python 3.12; removed in Python 3.14. Use `openpty()` instead.")
+            def slave_open(tty_name: str) -> int: ...
+        else:
+            def master_open() -> tuple[int, str]: ...
+            def slave_open(tty_name: str) -> int: ...
 
     def fork() -> tuple[int, int]: ...
     def spawn(argv: str | Iterable[str], master_read: _Reader = ..., stdin_read: _Reader = ...) -> int: ...
diff --git a/mypy/typeshed/stdlib/pydoc.pyi b/mypy/typeshed/stdlib/pydoc.pyi
index f14b9d1bb699..935f9420f88c 100644
--- a/mypy/typeshed/stdlib/pydoc.pyi
+++ b/mypy/typeshed/stdlib/pydoc.pyi
@@ -5,7 +5,7 @@ from builtins import list as _list  # "list" conflicts with method name
 from collections.abc import Callable, Container, Mapping, MutableMapping
 from reprlib import Repr
 from types import MethodType, ModuleType, TracebackType
-from typing import IO, Any, AnyStr, Final, NoReturn, Protocol, TypeVar
+from typing import IO, Any, AnyStr, Final, NoReturn, Protocol, TypeVar, type_check_only
 from typing_extensions import TypeGuard, deprecated
 
 __all__ = ["help"]
@@ -17,6 +17,7 @@ __date__: Final[str]
 __version__: Final[str]
 __credits__: Final[str]
 
+@type_check_only
 class _Pager(Protocol):
     def __call__(self, text: str, title: str = "") -> None: ...
 
@@ -33,11 +34,11 @@ def visiblename(name: str, all: Container[str] | None = None, obj: object = None
 def classify_class_attrs(object: object) -> list[tuple[str, str, type, str]]: ...
 
 if sys.version_info >= (3, 13):
-    @deprecated("Deprecated in Python 3.13.")
-    def ispackage(path: str) -> bool: ...
+    @deprecated("Deprecated since Python 3.13.")
+    def ispackage(path: str) -> bool: ...  # undocumented
 
 else:
-    def ispackage(path: str) -> bool: ...
+    def ispackage(path: str) -> bool: ...  # undocumented
 
 def source_synopsis(file: IO[AnyStr]) -> AnyStr | None: ...
 def synopsis(filename: str, cache: MutableMapping[str, tuple[int, str]] = {}) -> str | None: ...
diff --git a/mypy/typeshed/stdlib/pydoc_data/topics.pyi b/mypy/typeshed/stdlib/pydoc_data/topics.pyi
index 091d34300106..ce907a41c005 100644
--- a/mypy/typeshed/stdlib/pydoc_data/topics.pyi
+++ b/mypy/typeshed/stdlib/pydoc_data/topics.pyi
@@ -1 +1,3 @@
-topics: dict[str, str]
+from typing import Final
+
+topics: Final[dict[str, str]]
diff --git a/mypy/typeshed/stdlib/queue.pyi b/mypy/typeshed/stdlib/queue.pyi
index f5d9179e079d..65e2ac1559ad 100644
--- a/mypy/typeshed/stdlib/queue.pyi
+++ b/mypy/typeshed/stdlib/queue.pyi
@@ -1,5 +1,6 @@
 import sys
 from _queue import Empty as Empty, SimpleQueue as SimpleQueue
+from _typeshed import SupportsRichComparisonT
 from threading import Condition, Lock
 from types import GenericAlias
 from typing import Any, Generic, TypeVar
@@ -47,8 +48,8 @@ class Queue(Generic[_T]):
     def task_done(self) -> None: ...
     def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
-class PriorityQueue(Queue[_T]):
-    queue: list[_T]
+class PriorityQueue(Queue[SupportsRichComparisonT]):
+    queue: list[SupportsRichComparisonT]
 
 class LifoQueue(Queue[_T]):
     queue: list[_T]
diff --git a/mypy/typeshed/stdlib/quopri.pyi b/mypy/typeshed/stdlib/quopri.pyi
index b652e139bd0e..be6892fcbcd7 100644
--- a/mypy/typeshed/stdlib/quopri.pyi
+++ b/mypy/typeshed/stdlib/quopri.pyi
@@ -1,8 +1,9 @@
 from _typeshed import ReadableBuffer, SupportsNoArgReadline, SupportsRead, SupportsWrite
-from typing import Protocol
+from typing import Protocol, type_check_only
 
 __all__ = ["encode", "decode", "encodestring", "decodestring"]
 
+@type_check_only
 class _Input(SupportsRead[bytes], SupportsNoArgReadline[bytes], Protocol): ...
 
 def encode(input: _Input, output: SupportsWrite[bytes], quotetabs: int, header: bool = False) -> None: ...
diff --git a/mypy/typeshed/stdlib/random.pyi b/mypy/typeshed/stdlib/random.pyi
index 83e37113a941..a797794b8050 100644
--- a/mypy/typeshed/stdlib/random.pyi
+++ b/mypy/typeshed/stdlib/random.pyi
@@ -4,6 +4,7 @@ from _typeshed import SupportsLenAndGetItem
 from collections.abc import Callable, Iterable, MutableSequence, Sequence, Set as AbstractSet
 from fractions import Fraction
 from typing import Any, ClassVar, NoReturn, TypeVar
+from typing_extensions import Self
 
 __all__ = [
     "Random",
@@ -44,6 +45,10 @@ class Random(_random.Random):
     # Using other `seed` types is deprecated since 3.9 and removed in 3.11
     # Ignore Y041, since random.seed doesn't treat int like a float subtype. Having an explicit
     # int better documents conventional usage of random.seed.
+    if sys.version_info < (3, 10):
+        # this is a workaround for pyright correctly flagging an inconsistent inherited constructor, see #14624
+        def __new__(cls, x: int | float | str | bytes | bytearray | None = None) -> Self: ...  # noqa: Y041
+
     def seed(self, a: int | float | str | bytes | bytearray | None = None, version: int = 2) -> None: ...  # type: ignore[override]  # noqa: Y041
     def getstate(self) -> tuple[Any, ...]: ...
     def setstate(self, state: tuple[Any, ...]) -> None: ...
diff --git a/mypy/typeshed/stdlib/re.pyi b/mypy/typeshed/stdlib/re.pyi
index f25a0a376704..fb2a06d5e4c8 100644
--- a/mypy/typeshed/stdlib/re.pyi
+++ b/mypy/typeshed/stdlib/re.pyi
@@ -6,7 +6,7 @@ from _typeshed import MaybeNone, ReadableBuffer
 from collections.abc import Callable, Iterator, Mapping
 from types import GenericAlias
 from typing import Any, AnyStr, Final, Generic, Literal, TypeVar, final, overload
-from typing_extensions import TypeAlias
+from typing_extensions import TypeAlias, deprecated
 
 __all__ = [
     "match",
@@ -239,9 +239,7 @@ if sys.version_info < (3, 13):
     T: Final = RegexFlag.T
     TEMPLATE: Final = RegexFlag.TEMPLATE
 if sys.version_info >= (3, 11):
-    # pytype chokes on `NOFLAG: Final = RegexFlag.NOFLAG` with `LiteralValueError`
-    # mypy chokes on `NOFLAG: Final[Literal[RegexFlag.NOFLAG]]` with `Literal[...] is invalid`
-    NOFLAG = RegexFlag.NOFLAG
+    NOFLAG: Final = RegexFlag.NOFLAG
 _FlagsType: TypeAlias = int | RegexFlag
 
 # Type-wise the compile() overloads are unnecessary, they could also be modeled using
@@ -309,4 +307,8 @@ def escape(pattern: AnyStr) -> AnyStr: ...
 def purge() -> None: ...
 
 if sys.version_info < (3, 13):
-    def template(pattern: AnyStr | Pattern[AnyStr], flags: _FlagsType = 0) -> Pattern[AnyStr]: ...
+    if sys.version_info >= (3, 11):
+        @deprecated("Deprecated since Python 3.11; removed in Python 3.13. Use `re.compile()` instead.")
+        def template(pattern: AnyStr | Pattern[AnyStr], flags: _FlagsType = 0) -> Pattern[AnyStr]: ...  # undocumented
+    else:
+        def template(pattern: AnyStr | Pattern[AnyStr], flags: _FlagsType = 0) -> Pattern[AnyStr]: ...  # undocumented
diff --git a/mypy/typeshed/stdlib/resource.pyi b/mypy/typeshed/stdlib/resource.pyi
index 5e468c2cead5..f99cd5b08805 100644
--- a/mypy/typeshed/stdlib/resource.pyi
+++ b/mypy/typeshed/stdlib/resource.pyi
@@ -3,27 +3,28 @@ from _typeshed import structseq
 from typing import Final, final
 
 if sys.platform != "win32":
-    RLIMIT_AS: int
-    RLIMIT_CORE: int
-    RLIMIT_CPU: int
-    RLIMIT_DATA: int
-    RLIMIT_FSIZE: int
-    RLIMIT_MEMLOCK: int
-    RLIMIT_NOFILE: int
-    RLIMIT_NPROC: int
-    RLIMIT_RSS: int
-    RLIMIT_STACK: int
-    RLIM_INFINITY: int
-    RUSAGE_CHILDREN: int
-    RUSAGE_SELF: int
+    # Depends on resource.h
+    RLIMIT_AS: Final[int]
+    RLIMIT_CORE: Final[int]
+    RLIMIT_CPU: Final[int]
+    RLIMIT_DATA: Final[int]
+    RLIMIT_FSIZE: Final[int]
+    RLIMIT_MEMLOCK: Final[int]
+    RLIMIT_NOFILE: Final[int]
+    RLIMIT_NPROC: Final[int]
+    RLIMIT_RSS: Final[int]
+    RLIMIT_STACK: Final[int]
+    RLIM_INFINITY: Final[int]
+    RUSAGE_CHILDREN: Final[int]
+    RUSAGE_SELF: Final[int]
     if sys.platform == "linux":
-        RLIMIT_MSGQUEUE: int
-        RLIMIT_NICE: int
-        RLIMIT_OFILE: int
-        RLIMIT_RTPRIO: int
-        RLIMIT_RTTIME: int
-        RLIMIT_SIGPENDING: int
-        RUSAGE_THREAD: int
+        RLIMIT_MSGQUEUE: Final[int]
+        RLIMIT_NICE: Final[int]
+        RLIMIT_OFILE: Final[int]
+        RLIMIT_RTPRIO: Final[int]
+        RLIMIT_RTTIME: Final[int]
+        RLIMIT_SIGPENDING: Final[int]
+        RUSAGE_THREAD: Final[int]
 
     @final
     class struct_rusage(
diff --git a/mypy/typeshed/stdlib/select.pyi b/mypy/typeshed/stdlib/select.pyi
index 023547390273..587bc75376ef 100644
--- a/mypy/typeshed/stdlib/select.pyi
+++ b/mypy/typeshed/stdlib/select.pyi
@@ -2,25 +2,25 @@ import sys
 from _typeshed import FileDescriptorLike
 from collections.abc import Iterable
 from types import TracebackType
-from typing import Any, ClassVar, final
+from typing import Any, ClassVar, Final, final
 from typing_extensions import Self
 
 if sys.platform != "win32":
-    PIPE_BUF: int
-    POLLERR: int
-    POLLHUP: int
-    POLLIN: int
+    PIPE_BUF: Final[int]
+    POLLERR: Final[int]
+    POLLHUP: Final[int]
+    POLLIN: Final[int]
     if sys.platform == "linux":
-        POLLMSG: int
-    POLLNVAL: int
-    POLLOUT: int
-    POLLPRI: int
-    POLLRDBAND: int
+        POLLMSG: Final[int]
+    POLLNVAL: Final[int]
+    POLLOUT: Final[int]
+    POLLPRI: Final[int]
+    POLLRDBAND: Final[int]
     if sys.platform == "linux":
-        POLLRDHUP: int
-    POLLRDNORM: int
-    POLLWRBAND: int
-    POLLWRNORM: int
+        POLLRDHUP: Final[int]
+    POLLRDNORM: Final[int]
+    POLLWRBAND: Final[int]
+    POLLWRNORM: Final[int]
 
     # This is actually a function that returns an instance of a class.
     # The class is not accessible directly, and also calls itself select.poll.
@@ -71,50 +71,50 @@ if sys.platform != "linux" and sys.platform != "win32":
         @classmethod
         def fromfd(cls, fd: FileDescriptorLike, /) -> kqueue: ...
 
-    KQ_EV_ADD: int
-    KQ_EV_CLEAR: int
-    KQ_EV_DELETE: int
-    KQ_EV_DISABLE: int
-    KQ_EV_ENABLE: int
-    KQ_EV_EOF: int
-    KQ_EV_ERROR: int
-    KQ_EV_FLAG1: int
-    KQ_EV_ONESHOT: int
-    KQ_EV_SYSFLAGS: int
-    KQ_FILTER_AIO: int
+    KQ_EV_ADD: Final[int]
+    KQ_EV_CLEAR: Final[int]
+    KQ_EV_DELETE: Final[int]
+    KQ_EV_DISABLE: Final[int]
+    KQ_EV_ENABLE: Final[int]
+    KQ_EV_EOF: Final[int]
+    KQ_EV_ERROR: Final[int]
+    KQ_EV_FLAG1: Final[int]
+    KQ_EV_ONESHOT: Final[int]
+    KQ_EV_SYSFLAGS: Final[int]
+    KQ_FILTER_AIO: Final[int]
     if sys.platform != "darwin":
-        KQ_FILTER_NETDEV: int
-    KQ_FILTER_PROC: int
-    KQ_FILTER_READ: int
-    KQ_FILTER_SIGNAL: int
-    KQ_FILTER_TIMER: int
-    KQ_FILTER_VNODE: int
-    KQ_FILTER_WRITE: int
-    KQ_NOTE_ATTRIB: int
-    KQ_NOTE_CHILD: int
-    KQ_NOTE_DELETE: int
-    KQ_NOTE_EXEC: int
-    KQ_NOTE_EXIT: int
-    KQ_NOTE_EXTEND: int
-    KQ_NOTE_FORK: int
-    KQ_NOTE_LINK: int
+        KQ_FILTER_NETDEV: Final[int]
+    KQ_FILTER_PROC: Final[int]
+    KQ_FILTER_READ: Final[int]
+    KQ_FILTER_SIGNAL: Final[int]
+    KQ_FILTER_TIMER: Final[int]
+    KQ_FILTER_VNODE: Final[int]
+    KQ_FILTER_WRITE: Final[int]
+    KQ_NOTE_ATTRIB: Final[int]
+    KQ_NOTE_CHILD: Final[int]
+    KQ_NOTE_DELETE: Final[int]
+    KQ_NOTE_EXEC: Final[int]
+    KQ_NOTE_EXIT: Final[int]
+    KQ_NOTE_EXTEND: Final[int]
+    KQ_NOTE_FORK: Final[int]
+    KQ_NOTE_LINK: Final[int]
     if sys.platform != "darwin":
-        KQ_NOTE_LINKDOWN: int
-        KQ_NOTE_LINKINV: int
-        KQ_NOTE_LINKUP: int
-    KQ_NOTE_LOWAT: int
-    KQ_NOTE_PCTRLMASK: int
-    KQ_NOTE_PDATAMASK: int
-    KQ_NOTE_RENAME: int
-    KQ_NOTE_REVOKE: int
-    KQ_NOTE_TRACK: int
-    KQ_NOTE_TRACKERR: int
-    KQ_NOTE_WRITE: int
+        KQ_NOTE_LINKDOWN: Final[int]
+        KQ_NOTE_LINKINV: Final[int]
+        KQ_NOTE_LINKUP: Final[int]
+    KQ_NOTE_LOWAT: Final[int]
+    KQ_NOTE_PCTRLMASK: Final[int]
+    KQ_NOTE_PDATAMASK: Final[int]
+    KQ_NOTE_RENAME: Final[int]
+    KQ_NOTE_REVOKE: Final[int]
+    KQ_NOTE_TRACK: Final[int]
+    KQ_NOTE_TRACKERR: Final[int]
+    KQ_NOTE_WRITE: Final[int]
 
 if sys.platform == "linux":
     @final
     class epoll:
-        def __init__(self, sizehint: int = ..., flags: int = ...) -> None: ...
+        def __new__(self, sizehint: int = ..., flags: int = ...) -> Self: ...
         def __enter__(self) -> Self: ...
         def __exit__(
             self,
@@ -133,23 +133,23 @@ if sys.platform == "linux":
         @classmethod
         def fromfd(cls, fd: FileDescriptorLike, /) -> epoll: ...
 
-    EPOLLERR: int
-    EPOLLEXCLUSIVE: int
-    EPOLLET: int
-    EPOLLHUP: int
-    EPOLLIN: int
-    EPOLLMSG: int
-    EPOLLONESHOT: int
-    EPOLLOUT: int
-    EPOLLPRI: int
-    EPOLLRDBAND: int
-    EPOLLRDHUP: int
-    EPOLLRDNORM: int
-    EPOLLWRBAND: int
-    EPOLLWRNORM: int
-    EPOLL_CLOEXEC: int
+    EPOLLERR: Final[int]
+    EPOLLEXCLUSIVE: Final[int]
+    EPOLLET: Final[int]
+    EPOLLHUP: Final[int]
+    EPOLLIN: Final[int]
+    EPOLLMSG: Final[int]
+    EPOLLONESHOT: Final[int]
+    EPOLLOUT: Final[int]
+    EPOLLPRI: Final[int]
+    EPOLLRDBAND: Final[int]
+    EPOLLRDHUP: Final[int]
+    EPOLLRDNORM: Final[int]
+    EPOLLWRBAND: Final[int]
+    EPOLLWRNORM: Final[int]
+    EPOLL_CLOEXEC: Final[int]
     if sys.version_info >= (3, 14):
-        EPOLLWAKEUP: int
+        EPOLLWAKEUP: Final[int]
 
 if sys.platform != "linux" and sys.platform != "darwin" and sys.platform != "win32":
     # Solaris only
diff --git a/mypy/typeshed/stdlib/selectors.pyi b/mypy/typeshed/stdlib/selectors.pyi
index 0ba843a403d8..bcca4e341b9a 100644
--- a/mypy/typeshed/stdlib/selectors.pyi
+++ b/mypy/typeshed/stdlib/selectors.pyi
@@ -2,13 +2,13 @@ import sys
 from _typeshed import FileDescriptor, FileDescriptorLike, Unused
 from abc import ABCMeta, abstractmethod
 from collections.abc import Mapping
-from typing import Any, NamedTuple
+from typing import Any, Final, NamedTuple
 from typing_extensions import Self, TypeAlias
 
 _EventMask: TypeAlias = int
 
-EVENT_READ: _EventMask
-EVENT_WRITE: _EventMask
+EVENT_READ: Final = 1
+EVENT_WRITE: Final = 2
 
 class SelectorKey(NamedTuple):
     fileobj: FileDescriptorLike
diff --git a/mypy/typeshed/stdlib/shutil.pyi b/mypy/typeshed/stdlib/shutil.pyi
index c66d8fa128be..cc26cfc556a0 100644
--- a/mypy/typeshed/stdlib/shutil.pyi
+++ b/mypy/typeshed/stdlib/shutil.pyi
@@ -3,7 +3,7 @@ import sys
 from _typeshed import BytesPath, ExcInfo, FileDescriptorOrPath, MaybeNone, StrOrBytesPath, StrPath, SupportsRead, SupportsWrite
 from collections.abc import Callable, Iterable, Sequence
 from tarfile import _TarfileFilter
-from typing import Any, AnyStr, NamedTuple, NoReturn, Protocol, TypeVar, overload
+from typing import Any, AnyStr, NamedTuple, NoReturn, Protocol, TypeVar, overload, type_check_only
 from typing_extensions import TypeAlias, deprecated
 
 __all__ = [
@@ -79,6 +79,7 @@ def copytree(
 _OnErrorCallback: TypeAlias = Callable[[Callable[..., Any], str, ExcInfo], object]
 _OnExcCallback: TypeAlias = Callable[[Callable[..., Any], str, BaseException], object]
 
+@type_check_only
 class _RmtreeType(Protocol):
     avoids_symlink_attacks: bool
     if sys.version_info >= (3, 12):
diff --git a/mypy/typeshed/stdlib/signal.pyi b/mypy/typeshed/stdlib/signal.pyi
index d50565d1c8ac..c2668bd8b32d 100644
--- a/mypy/typeshed/stdlib/signal.pyi
+++ b/mypy/typeshed/stdlib/signal.pyi
@@ -3,7 +3,7 @@ from _typeshed import structseq
 from collections.abc import Callable, Iterable
 from enum import IntEnum
 from types import FrameType
-from typing import Any, Final, Literal, final
+from typing import Any, Final, final
 from typing_extensions import Never, TypeAlias
 
 NSIG: int
@@ -61,8 +61,8 @@ class Handlers(IntEnum):
     SIG_DFL = 0
     SIG_IGN = 1
 
-SIG_DFL: Literal[Handlers.SIG_DFL]
-SIG_IGN: Literal[Handlers.SIG_IGN]
+SIG_DFL: Final = Handlers.SIG_DFL
+SIG_IGN: Final = Handlers.SIG_IGN
 
 _SIGNUM: TypeAlias = int | Signals
 _HANDLER: TypeAlias = Callable[[int, FrameType | None], Any] | int | Handlers | None
@@ -77,45 +77,45 @@ else:
     def getsignal(signalnum: _SIGNUM, /) -> _HANDLER: ...
     def signal(signalnum: _SIGNUM, handler: _HANDLER, /) -> _HANDLER: ...
 
-SIGABRT: Literal[Signals.SIGABRT]
-SIGFPE: Literal[Signals.SIGFPE]
-SIGILL: Literal[Signals.SIGILL]
-SIGINT: Literal[Signals.SIGINT]
-SIGSEGV: Literal[Signals.SIGSEGV]
-SIGTERM: Literal[Signals.SIGTERM]
+SIGABRT: Final = Signals.SIGABRT
+SIGFPE: Final = Signals.SIGFPE
+SIGILL: Final = Signals.SIGILL
+SIGINT: Final = Signals.SIGINT
+SIGSEGV: Final = Signals.SIGSEGV
+SIGTERM: Final = Signals.SIGTERM
 
 if sys.platform == "win32":
-    SIGBREAK: Literal[Signals.SIGBREAK]
-    CTRL_C_EVENT: Literal[Signals.CTRL_C_EVENT]
-    CTRL_BREAK_EVENT: Literal[Signals.CTRL_BREAK_EVENT]
+    SIGBREAK: Final = Signals.SIGBREAK
+    CTRL_C_EVENT: Final = Signals.CTRL_C_EVENT
+    CTRL_BREAK_EVENT: Final = Signals.CTRL_BREAK_EVENT
 else:
     if sys.platform != "linux":
-        SIGINFO: Literal[Signals.SIGINFO]
-        SIGEMT: Literal[Signals.SIGEMT]
-    SIGALRM: Literal[Signals.SIGALRM]
-    SIGBUS: Literal[Signals.SIGBUS]
-    SIGCHLD: Literal[Signals.SIGCHLD]
-    SIGCONT: Literal[Signals.SIGCONT]
-    SIGHUP: Literal[Signals.SIGHUP]
-    SIGIO: Literal[Signals.SIGIO]
-    SIGIOT: Literal[Signals.SIGABRT]  # alias
-    SIGKILL: Literal[Signals.SIGKILL]
-    SIGPIPE: Literal[Signals.SIGPIPE]
-    SIGPROF: Literal[Signals.SIGPROF]
-    SIGQUIT: Literal[Signals.SIGQUIT]
-    SIGSTOP: Literal[Signals.SIGSTOP]
-    SIGSYS: Literal[Signals.SIGSYS]
-    SIGTRAP: Literal[Signals.SIGTRAP]
-    SIGTSTP: Literal[Signals.SIGTSTP]
-    SIGTTIN: Literal[Signals.SIGTTIN]
-    SIGTTOU: Literal[Signals.SIGTTOU]
-    SIGURG: Literal[Signals.SIGURG]
-    SIGUSR1: Literal[Signals.SIGUSR1]
-    SIGUSR2: Literal[Signals.SIGUSR2]
-    SIGVTALRM: Literal[Signals.SIGVTALRM]
-    SIGWINCH: Literal[Signals.SIGWINCH]
-    SIGXCPU: Literal[Signals.SIGXCPU]
-    SIGXFSZ: Literal[Signals.SIGXFSZ]
+        SIGINFO: Final = Signals.SIGINFO
+        SIGEMT: Final = Signals.SIGEMT
+    SIGALRM: Final = Signals.SIGALRM
+    SIGBUS: Final = Signals.SIGBUS
+    SIGCHLD: Final = Signals.SIGCHLD
+    SIGCONT: Final = Signals.SIGCONT
+    SIGHUP: Final = Signals.SIGHUP
+    SIGIO: Final = Signals.SIGIO
+    SIGIOT: Final = Signals.SIGABRT  # alias
+    SIGKILL: Final = Signals.SIGKILL
+    SIGPIPE: Final = Signals.SIGPIPE
+    SIGPROF: Final = Signals.SIGPROF
+    SIGQUIT: Final = Signals.SIGQUIT
+    SIGSTOP: Final = Signals.SIGSTOP
+    SIGSYS: Final = Signals.SIGSYS
+    SIGTRAP: Final = Signals.SIGTRAP
+    SIGTSTP: Final = Signals.SIGTSTP
+    SIGTTIN: Final = Signals.SIGTTIN
+    SIGTTOU: Final = Signals.SIGTTOU
+    SIGURG: Final = Signals.SIGURG
+    SIGUSR1: Final = Signals.SIGUSR1
+    SIGUSR2: Final = Signals.SIGUSR2
+    SIGVTALRM: Final = Signals.SIGVTALRM
+    SIGWINCH: Final = Signals.SIGWINCH
+    SIGXCPU: Final = Signals.SIGXCPU
+    SIGXFSZ: Final = Signals.SIGXFSZ
 
     class ItimerError(OSError): ...
     ITIMER_PROF: int
@@ -127,9 +127,9 @@ else:
         SIG_UNBLOCK = 1
         SIG_SETMASK = 2
 
-    SIG_BLOCK: Literal[Sigmasks.SIG_BLOCK]
-    SIG_UNBLOCK: Literal[Sigmasks.SIG_UNBLOCK]
-    SIG_SETMASK: Literal[Sigmasks.SIG_SETMASK]
+    SIG_BLOCK: Final = Sigmasks.SIG_BLOCK
+    SIG_UNBLOCK: Final = Sigmasks.SIG_UNBLOCK
+    SIG_SETMASK: Final = Sigmasks.SIG_SETMASK
     def alarm(seconds: int, /) -> int: ...
     def getitimer(which: int, /) -> tuple[float, float]: ...
     def pause() -> None: ...
@@ -147,13 +147,13 @@ else:
     else:
         def sigwait(sigset: Iterable[int], /) -> _SIGNUM: ...
     if sys.platform != "darwin":
-        SIGCLD: Literal[Signals.SIGCHLD]  # alias
-        SIGPOLL: Literal[Signals.SIGIO]  # alias
-        SIGPWR: Literal[Signals.SIGPWR]
-        SIGRTMAX: Literal[Signals.SIGRTMAX]
-        SIGRTMIN: Literal[Signals.SIGRTMIN]
+        SIGCLD: Final = Signals.SIGCHLD  # alias
+        SIGPOLL: Final = Signals.SIGIO  # alias
+        SIGPWR: Final = Signals.SIGPWR
+        SIGRTMAX: Final = Signals.SIGRTMAX
+        SIGRTMIN: Final = Signals.SIGRTMIN
         if sys.version_info >= (3, 11):
-            SIGSTKFLT: Literal[Signals.SIGSTKFLT]
+            SIGSTKFLT: Final = Signals.SIGSTKFLT
 
         @final
         class struct_siginfo(structseq[int], tuple[int, int, int, int, int, int, int]):
@@ -181,7 +181,7 @@ else:
 def strsignal(signalnum: _SIGNUM, /) -> str | None: ...
 def valid_signals() -> set[Signals]: ...
 def raise_signal(signalnum: _SIGNUM, /) -> None: ...
-def set_wakeup_fd(fd: int, /, *, warn_on_full_buffer: bool = ...) -> int: ...
+def set_wakeup_fd(fd: int, /, *, warn_on_full_buffer: bool = True) -> int: ...
 
 if sys.platform == "linux":
-    def pidfd_send_signal(pidfd: int, sig: int, siginfo: None = None, flags: int = ..., /) -> None: ...
+    def pidfd_send_signal(pidfd: int, sig: int, siginfo: None = None, flags: int = 0, /) -> None: ...
diff --git a/mypy/typeshed/stdlib/smtpd.pyi b/mypy/typeshed/stdlib/smtpd.pyi
index 7392bd51627d..dee7e949f42f 100644
--- a/mypy/typeshed/stdlib/smtpd.pyi
+++ b/mypy/typeshed/stdlib/smtpd.pyi
@@ -4,7 +4,7 @@ import socket
 import sys
 from collections import defaultdict
 from typing import Any
-from typing_extensions import TypeAlias
+from typing_extensions import TypeAlias, deprecated
 
 if sys.version_info >= (3, 11):
     __all__ = ["SMTPChannel", "SMTPServer", "DebuggingServer", "PureProxy"]
@@ -87,5 +87,6 @@ class PureProxy(SMTPServer):
     def process_message(self, peer: _Address, mailfrom: str, rcpttos: list[str], data: bytes | str) -> str | None: ...  # type: ignore[override]
 
 if sys.version_info < (3, 11):
+    @deprecated("Deprecated since Python 3.9; removed in Python 3.11.")
     class MailmanProxy(PureProxy):
         def process_message(self, peer: _Address, mailfrom: str, rcpttos: list[str], data: bytes | str) -> str | None: ...  # type: ignore[override]
diff --git a/mypy/typeshed/stdlib/smtplib.pyi b/mypy/typeshed/stdlib/smtplib.pyi
index 609b3e6426c4..6a8467689367 100644
--- a/mypy/typeshed/stdlib/smtplib.pyi
+++ b/mypy/typeshed/stdlib/smtplib.pyi
@@ -7,7 +7,7 @@ from re import Pattern
 from socket import socket
 from ssl import SSLContext
 from types import TracebackType
-from typing import Any, Protocol, overload
+from typing import Any, Final, Protocol, overload, type_check_only
 from typing_extensions import Self, TypeAlias
 
 __all__ = [
@@ -30,12 +30,12 @@ __all__ = [
 _Reply: TypeAlias = tuple[int, bytes]
 _SendErrs: TypeAlias = dict[str, _Reply]
 
-SMTP_PORT: int
-SMTP_SSL_PORT: int
-CRLF: str
-bCRLF: bytes
+SMTP_PORT: Final = 25
+SMTP_SSL_PORT: Final = 465
+CRLF: Final[str]
+bCRLF: Final[bytes]
 
-OLDSTYLE_AUTH: Pattern[str]
+OLDSTYLE_AUTH: Final[Pattern[str]]
 
 class SMTPException(OSError): ...
 class SMTPNotSupportedError(SMTPException): ...
@@ -65,7 +65,7 @@ class SMTPAuthenticationError(SMTPResponseException): ...
 
 def quoteaddr(addrstring: str) -> str: ...
 def quotedata(data: str) -> str: ...
-
+@type_check_only
 class _AuthObject(Protocol):
     @overload
     def __call__(self, challenge: None = None, /) -> str | None: ...
@@ -182,7 +182,7 @@ class SMTP_SSL(SMTP):
             context: SSLContext | None = None,
         ) -> None: ...
 
-LMTP_PORT: int
+LMTP_PORT: Final = 2003
 
 class LMTP(SMTP):
     def __init__(
diff --git a/mypy/typeshed/stdlib/socket.pyi b/mypy/typeshed/stdlib/socket.pyi
index 1ee006235ee6..b10b3560b91f 100644
--- a/mypy/typeshed/stdlib/socket.pyi
+++ b/mypy/typeshed/stdlib/socket.pyi
@@ -136,7 +136,7 @@ from _typeshed import ReadableBuffer, Unused, WriteableBuffer
 from collections.abc import Iterable
 from enum import IntEnum, IntFlag
 from io import BufferedReader, BufferedRWPair, BufferedWriter, IOBase, RawIOBase, TextIOWrapper
-from typing import Any, Literal, Protocol, SupportsIndex, overload
+from typing import Any, Final, Literal, Protocol, SupportsIndex, overload, type_check_only
 from typing_extensions import Self
 
 __all__ = [
@@ -773,6 +773,10 @@ if sys.platform == "linux":
     if sys.version_info < (3, 11):
         from _socket import CAN_RAW_ERR_FILTER as CAN_RAW_ERR_FILTER
 
+        __all__ += ["CAN_RAW_ERR_FILTER"]
+    if sys.version_info >= (3, 13):
+        from _socket import CAN_RAW_ERR_FILTER as CAN_RAW_ERR_FILTER
+
         __all__ += ["CAN_RAW_ERR_FILTER"]
 
 if sys.platform == "linux":
@@ -1047,19 +1051,17 @@ if sys.version_info >= (3, 14):
 
     if sys.platform == "linux":
         from _socket import (
-            CAN_RAW_ERR_FILTER as CAN_RAW_ERR_FILTER,
             IP_FREEBIND as IP_FREEBIND,
             IP_RECVORIGDSTADDR as IP_RECVORIGDSTADDR,
-            SO_ORIGINAL_DST as SO_ORIGINAL_DST,
             VMADDR_CID_LOCAL as VMADDR_CID_LOCAL,
         )
 
-        __all__ += ["CAN_RAW_ERR_FILTER", "IP_FREEBIND", "IP_RECVORIGDSTADDR", "VMADDR_CID_LOCAL"]
+        __all__ += ["IP_FREEBIND", "IP_RECVORIGDSTADDR", "VMADDR_CID_LOCAL"]
 
 # Re-exported from errno
-EBADF: int
-EAGAIN: int
-EWOULDBLOCK: int
+EBADF: Final[int]
+EAGAIN: Final[int]
+EWOULDBLOCK: Final[int]
 
 # These errors are implemented in _socket at runtime
 # but they consider themselves to live in socket so we'll put them here.
@@ -1122,60 +1124,60 @@ class AddressFamily(IntEnum):
         # FreeBSD >= 14.0
         AF_DIVERT = 44
 
-AF_INET = AddressFamily.AF_INET
-AF_INET6 = AddressFamily.AF_INET6
-AF_APPLETALK = AddressFamily.AF_APPLETALK
-AF_DECnet: Literal[12]
-AF_IPX = AddressFamily.AF_IPX
-AF_SNA = AddressFamily.AF_SNA
-AF_UNSPEC = AddressFamily.AF_UNSPEC
+AF_INET: Final = AddressFamily.AF_INET
+AF_INET6: Final = AddressFamily.AF_INET6
+AF_APPLETALK: Final = AddressFamily.AF_APPLETALK
+AF_DECnet: Final = 12
+AF_IPX: Final = AddressFamily.AF_IPX
+AF_SNA: Final = AddressFamily.AF_SNA
+AF_UNSPEC: Final = AddressFamily.AF_UNSPEC
 
 if sys.platform != "darwin":
-    AF_IRDA = AddressFamily.AF_IRDA
+    AF_IRDA: Final = AddressFamily.AF_IRDA
 
 if sys.platform != "win32":
-    AF_ROUTE = AddressFamily.AF_ROUTE
-    AF_UNIX = AddressFamily.AF_UNIX
+    AF_ROUTE: Final = AddressFamily.AF_ROUTE
+    AF_UNIX: Final = AddressFamily.AF_UNIX
 
 if sys.platform == "darwin":
-    AF_SYSTEM = AddressFamily.AF_SYSTEM
+    AF_SYSTEM: Final = AddressFamily.AF_SYSTEM
 
 if sys.platform != "win32" and sys.platform != "darwin":
-    AF_ASH = AddressFamily.AF_ASH
-    AF_ATMPVC = AddressFamily.AF_ATMPVC
-    AF_ATMSVC = AddressFamily.AF_ATMSVC
-    AF_AX25 = AddressFamily.AF_AX25
-    AF_BRIDGE = AddressFamily.AF_BRIDGE
-    AF_ECONET = AddressFamily.AF_ECONET
-    AF_KEY = AddressFamily.AF_KEY
-    AF_LLC = AddressFamily.AF_LLC
-    AF_NETBEUI = AddressFamily.AF_NETBEUI
-    AF_NETROM = AddressFamily.AF_NETROM
-    AF_PPPOX = AddressFamily.AF_PPPOX
-    AF_ROSE = AddressFamily.AF_ROSE
-    AF_SECURITY = AddressFamily.AF_SECURITY
-    AF_WANPIPE = AddressFamily.AF_WANPIPE
-    AF_X25 = AddressFamily.AF_X25
+    AF_ASH: Final = AddressFamily.AF_ASH
+    AF_ATMPVC: Final = AddressFamily.AF_ATMPVC
+    AF_ATMSVC: Final = AddressFamily.AF_ATMSVC
+    AF_AX25: Final = AddressFamily.AF_AX25
+    AF_BRIDGE: Final = AddressFamily.AF_BRIDGE
+    AF_ECONET: Final = AddressFamily.AF_ECONET
+    AF_KEY: Final = AddressFamily.AF_KEY
+    AF_LLC: Final = AddressFamily.AF_LLC
+    AF_NETBEUI: Final = AddressFamily.AF_NETBEUI
+    AF_NETROM: Final = AddressFamily.AF_NETROM
+    AF_PPPOX: Final = AddressFamily.AF_PPPOX
+    AF_ROSE: Final = AddressFamily.AF_ROSE
+    AF_SECURITY: Final = AddressFamily.AF_SECURITY
+    AF_WANPIPE: Final = AddressFamily.AF_WANPIPE
+    AF_X25: Final = AddressFamily.AF_X25
 
 if sys.platform == "linux":
-    AF_CAN = AddressFamily.AF_CAN
-    AF_PACKET = AddressFamily.AF_PACKET
-    AF_RDS = AddressFamily.AF_RDS
-    AF_TIPC = AddressFamily.AF_TIPC
-    AF_ALG = AddressFamily.AF_ALG
-    AF_NETLINK = AddressFamily.AF_NETLINK
-    AF_VSOCK = AddressFamily.AF_VSOCK
-    AF_QIPCRTR = AddressFamily.AF_QIPCRTR
+    AF_CAN: Final = AddressFamily.AF_CAN
+    AF_PACKET: Final = AddressFamily.AF_PACKET
+    AF_RDS: Final = AddressFamily.AF_RDS
+    AF_TIPC: Final = AddressFamily.AF_TIPC
+    AF_ALG: Final = AddressFamily.AF_ALG
+    AF_NETLINK: Final = AddressFamily.AF_NETLINK
+    AF_VSOCK: Final = AddressFamily.AF_VSOCK
+    AF_QIPCRTR: Final = AddressFamily.AF_QIPCRTR
 
 if sys.platform != "linux":
-    AF_LINK = AddressFamily.AF_LINK
+    AF_LINK: Final = AddressFamily.AF_LINK
 if sys.platform != "darwin" and sys.platform != "linux":
-    AF_BLUETOOTH = AddressFamily.AF_BLUETOOTH
+    AF_BLUETOOTH: Final = AddressFamily.AF_BLUETOOTH
 if sys.platform == "win32" and sys.version_info >= (3, 12):
-    AF_HYPERV = AddressFamily.AF_HYPERV
+    AF_HYPERV: Final = AddressFamily.AF_HYPERV
 if sys.platform != "linux" and sys.platform != "win32" and sys.platform != "darwin" and sys.version_info >= (3, 12):
     # FreeBSD >= 14.0
-    AF_DIVERT = AddressFamily.AF_DIVERT
+    AF_DIVERT: Final = AddressFamily.AF_DIVERT
 
 class SocketKind(IntEnum):
     SOCK_STREAM = 1
@@ -1187,14 +1189,14 @@ class SocketKind(IntEnum):
         SOCK_CLOEXEC = 524288
         SOCK_NONBLOCK = 2048
 
-SOCK_STREAM = SocketKind.SOCK_STREAM
-SOCK_DGRAM = SocketKind.SOCK_DGRAM
-SOCK_RAW = SocketKind.SOCK_RAW
-SOCK_RDM = SocketKind.SOCK_RDM
-SOCK_SEQPACKET = SocketKind.SOCK_SEQPACKET
+SOCK_STREAM: Final = SocketKind.SOCK_STREAM
+SOCK_DGRAM: Final = SocketKind.SOCK_DGRAM
+SOCK_RAW: Final = SocketKind.SOCK_RAW
+SOCK_RDM: Final = SocketKind.SOCK_RDM
+SOCK_SEQPACKET: Final = SocketKind.SOCK_SEQPACKET
 if sys.platform == "linux":
-    SOCK_CLOEXEC = SocketKind.SOCK_CLOEXEC
-    SOCK_NONBLOCK = SocketKind.SOCK_NONBLOCK
+    SOCK_CLOEXEC: Final = SocketKind.SOCK_CLOEXEC
+    SOCK_NONBLOCK: Final = SocketKind.SOCK_NONBLOCK
 
 class MsgFlag(IntFlag):
     MSG_CTRUNC = 8
@@ -1226,36 +1228,36 @@ class MsgFlag(IntFlag):
     if sys.platform != "win32" and sys.platform != "linux":
         MSG_EOF = 256
 
-MSG_CTRUNC = MsgFlag.MSG_CTRUNC
-MSG_DONTROUTE = MsgFlag.MSG_DONTROUTE
-MSG_OOB = MsgFlag.MSG_OOB
-MSG_PEEK = MsgFlag.MSG_PEEK
-MSG_TRUNC = MsgFlag.MSG_TRUNC
-MSG_WAITALL = MsgFlag.MSG_WAITALL
+MSG_CTRUNC: Final = MsgFlag.MSG_CTRUNC
+MSG_DONTROUTE: Final = MsgFlag.MSG_DONTROUTE
+MSG_OOB: Final = MsgFlag.MSG_OOB
+MSG_PEEK: Final = MsgFlag.MSG_PEEK
+MSG_TRUNC: Final = MsgFlag.MSG_TRUNC
+MSG_WAITALL: Final = MsgFlag.MSG_WAITALL
 
 if sys.platform == "win32":
-    MSG_BCAST = MsgFlag.MSG_BCAST
-    MSG_MCAST = MsgFlag.MSG_MCAST
+    MSG_BCAST: Final = MsgFlag.MSG_BCAST
+    MSG_MCAST: Final = MsgFlag.MSG_MCAST
 
 if sys.platform != "darwin":
-    MSG_ERRQUEUE = MsgFlag.MSG_ERRQUEUE
+    MSG_ERRQUEUE: Final = MsgFlag.MSG_ERRQUEUE
 
 if sys.platform != "win32":
-    MSG_DONTWAIT = MsgFlag.MSG_DONTWAIT
-    MSG_EOR = MsgFlag.MSG_EOR
-    MSG_NOSIGNAL = MsgFlag.MSG_NOSIGNAL  # Sometimes this exists on darwin, sometimes not
+    MSG_DONTWAIT: Final = MsgFlag.MSG_DONTWAIT
+    MSG_EOR: Final = MsgFlag.MSG_EOR
+    MSG_NOSIGNAL: Final = MsgFlag.MSG_NOSIGNAL  # Sometimes this exists on darwin, sometimes not
 
 if sys.platform != "win32" and sys.platform != "darwin":
-    MSG_CMSG_CLOEXEC = MsgFlag.MSG_CMSG_CLOEXEC
-    MSG_CONFIRM = MsgFlag.MSG_CONFIRM
-    MSG_FASTOPEN = MsgFlag.MSG_FASTOPEN
-    MSG_MORE = MsgFlag.MSG_MORE
+    MSG_CMSG_CLOEXEC: Final = MsgFlag.MSG_CMSG_CLOEXEC
+    MSG_CONFIRM: Final = MsgFlag.MSG_CONFIRM
+    MSG_FASTOPEN: Final = MsgFlag.MSG_FASTOPEN
+    MSG_MORE: Final = MsgFlag.MSG_MORE
 
 if sys.platform != "win32" and sys.platform != "darwin" and sys.platform != "linux":
-    MSG_NOTIFICATION = MsgFlag.MSG_NOTIFICATION
+    MSG_NOTIFICATION: Final = MsgFlag.MSG_NOTIFICATION
 
 if sys.platform != "win32" and sys.platform != "linux":
-    MSG_EOF = MsgFlag.MSG_EOF
+    MSG_EOF: Final = MsgFlag.MSG_EOF
 
 class AddressInfo(IntFlag):
     AI_ADDRCONFIG = 32
@@ -1270,22 +1272,23 @@ class AddressInfo(IntFlag):
         AI_MASK = 5127
         AI_V4MAPPED_CFG = 512
 
-AI_ADDRCONFIG = AddressInfo.AI_ADDRCONFIG
-AI_ALL = AddressInfo.AI_ALL
-AI_CANONNAME = AddressInfo.AI_CANONNAME
-AI_NUMERICHOST = AddressInfo.AI_NUMERICHOST
-AI_NUMERICSERV = AddressInfo.AI_NUMERICSERV
-AI_PASSIVE = AddressInfo.AI_PASSIVE
-AI_V4MAPPED = AddressInfo.AI_V4MAPPED
+AI_ADDRCONFIG: Final = AddressInfo.AI_ADDRCONFIG
+AI_ALL: Final = AddressInfo.AI_ALL
+AI_CANONNAME: Final = AddressInfo.AI_CANONNAME
+AI_NUMERICHOST: Final = AddressInfo.AI_NUMERICHOST
+AI_NUMERICSERV: Final = AddressInfo.AI_NUMERICSERV
+AI_PASSIVE: Final = AddressInfo.AI_PASSIVE
+AI_V4MAPPED: Final = AddressInfo.AI_V4MAPPED
 
 if sys.platform != "win32" and sys.platform != "linux":
-    AI_DEFAULT = AddressInfo.AI_DEFAULT
-    AI_MASK = AddressInfo.AI_MASK
-    AI_V4MAPPED_CFG = AddressInfo.AI_V4MAPPED_CFG
+    AI_DEFAULT: Final = AddressInfo.AI_DEFAULT
+    AI_MASK: Final = AddressInfo.AI_MASK
+    AI_V4MAPPED_CFG: Final = AddressInfo.AI_V4MAPPED_CFG
 
 if sys.platform == "win32":
     errorTab: dict[int, str]  # undocumented
 
+@type_check_only
 class _SendableFile(Protocol):
     def read(self, size: int, /) -> bytes: ...
     def seek(self, offset: int, /) -> object: ...
@@ -1297,6 +1300,7 @@ class _SendableFile(Protocol):
     # def fileno(self) -> int: ...
 
 class socket(_socket.socket):
+    __slots__ = ["__weakref__", "_io_refs", "_closed"]
     def __init__(
         self, family: AddressFamily | int = -1, type: SocketKind | int = -1, proto: int = -1, fileno: int | None = None
     ) -> None: ...
diff --git a/mypy/typeshed/stdlib/sqlite3/__init__.pyi b/mypy/typeshed/stdlib/sqlite3/__init__.pyi
index ab783dbde121..882cd143c29c 100644
--- a/mypy/typeshed/stdlib/sqlite3/__init__.pyi
+++ b/mypy/typeshed/stdlib/sqlite3/__init__.pyi
@@ -63,7 +63,7 @@ from sqlite3.dbapi2 import (
 )
 from types import TracebackType
 from typing import Any, Literal, Protocol, SupportsIndex, TypeVar, final, overload, type_check_only
-from typing_extensions import Self, TypeAlias
+from typing_extensions import Self, TypeAlias, disjoint_base
 
 if sys.version_info < (3, 14):
     from sqlite3.dbapi2 import version_info as version_info
@@ -220,23 +220,29 @@ _SqliteData: TypeAlias = str | ReadableBuffer | int | float | None
 _AdaptedInputData: TypeAlias = _SqliteData | Any
 # The Mapping must really be a dict, but making it invariant is too annoying.
 _Parameters: TypeAlias = SupportsLenAndGetItem[_AdaptedInputData] | Mapping[str, _AdaptedInputData]
+# Controls the legacy transaction handling mode of sqlite3.
+_IsolationLevel: TypeAlias = Literal["DEFERRED", "EXCLUSIVE", "IMMEDIATE"] | None
 
+@type_check_only
 class _AnyParamWindowAggregateClass(Protocol):
     def step(self, *args: Any) -> object: ...
     def inverse(self, *args: Any) -> object: ...
     def value(self) -> _SqliteData: ...
     def finalize(self) -> _SqliteData: ...
 
+@type_check_only
 class _WindowAggregateClass(Protocol):
     step: Callable[..., object]
     inverse: Callable[..., object]
     def value(self) -> _SqliteData: ...
     def finalize(self) -> _SqliteData: ...
 
+@type_check_only
 class _AggregateProtocol(Protocol):
     def step(self, value: int, /) -> object: ...
     def finalize(self) -> int: ...
 
+@type_check_only
 class _SingleParamWindowAggregateClass(Protocol):
     def step(self, param: Any, /) -> object: ...
     def inverse(self, param: Any, /) -> object: ...
@@ -262,6 +268,7 @@ class OperationalError(DatabaseError): ...
 class ProgrammingError(DatabaseError): ...
 class Warning(Exception): ...
 
+@disjoint_base
 class Connection:
     @property
     def DataError(self) -> type[DataError]: ...
@@ -285,7 +292,7 @@ class Connection:
     def Warning(self) -> type[Warning]: ...
     @property
     def in_transaction(self) -> bool: ...
-    isolation_level: str | None  # one of '', 'DEFERRED', 'IMMEDIATE' or 'EXCLUSIVE'
+    isolation_level: _IsolationLevel
     @property
     def total_changes(self) -> int: ...
     if sys.version_info >= (3, 12):
@@ -299,26 +306,26 @@ class Connection:
         def __init__(
             self,
             database: StrOrBytesPath,
-            timeout: float = ...,
-            detect_types: int = ...,
-            isolation_level: str | None = ...,
-            check_same_thread: bool = ...,
+            timeout: float = 5.0,
+            detect_types: int = 0,
+            isolation_level: _IsolationLevel = "DEFERRED",
+            check_same_thread: bool = True,
             factory: type[Connection] | None = ...,
-            cached_statements: int = ...,
-            uri: bool = ...,
+            cached_statements: int = 128,
+            uri: bool = False,
             autocommit: bool = ...,
         ) -> None: ...
     else:
         def __init__(
             self,
             database: StrOrBytesPath,
-            timeout: float = ...,
-            detect_types: int = ...,
-            isolation_level: str | None = ...,
-            check_same_thread: bool = ...,
+            timeout: float = 5.0,
+            detect_types: int = 0,
+            isolation_level: _IsolationLevel = "DEFERRED",
+            check_same_thread: bool = True,
             factory: type[Connection] | None = ...,
-            cached_statements: int = ...,
-            uri: bool = ...,
+            cached_statements: int = 128,
+            uri: bool = False,
         ) -> None: ...
 
     def close(self) -> None: ...
@@ -399,6 +406,7 @@ class Connection:
         self, type: type[BaseException] | None, value: BaseException | None, traceback: TracebackType | None, /
     ) -> Literal[False]: ...
 
+@disjoint_base
 class Cursor(Iterator[Any]):
     arraysize: int
     @property
@@ -430,6 +438,7 @@ class Cursor(Iterator[Any]):
 class PrepareProtocol:
     def __init__(self, *args: object, **kwargs: object) -> None: ...
 
+@disjoint_base
 class Row(Sequence[Any]):
     def __new__(cls, cursor: Cursor, data: tuple[Any, ...], /) -> Self: ...
     def keys(self) -> list[str]: ...
diff --git a/mypy/typeshed/stdlib/sqlite3/dbapi2.pyi b/mypy/typeshed/stdlib/sqlite3/dbapi2.pyi
index d3ea3ef0e896..9e170a81243d 100644
--- a/mypy/typeshed/stdlib/sqlite3/dbapi2.pyi
+++ b/mypy/typeshed/stdlib/sqlite3/dbapi2.pyi
@@ -66,6 +66,8 @@ from sqlite3 import (
     Row as Row,
     Warning as Warning,
 )
+from typing import Final, Literal
+from typing_extensions import deprecated
 
 if sys.version_info >= (3, 12):
     from _sqlite3 import (
@@ -210,11 +212,15 @@ if sys.version_info >= (3, 11):
 
 if sys.version_info < (3, 14):
     # Deprecated and removed from _sqlite3 in 3.12, but removed from here in 3.14.
-    version: str
+    version: Final[str]
 
 if sys.version_info < (3, 12):
     if sys.version_info >= (3, 10):
         # deprecation wrapper that has a different name for the argument...
+        @deprecated(
+            "Deprecated since Python 3.10; removed in Python 3.12. "
+            "Open database in URI mode using `cache=shared` parameter instead."
+        )
         def enable_shared_cache(enable: int) -> None: ...
     else:
         from _sqlite3 import enable_shared_cache as enable_shared_cache
@@ -222,9 +228,9 @@ if sys.version_info < (3, 12):
 if sys.version_info < (3, 10):
     from _sqlite3 import OptimizedUnicode as OptimizedUnicode
 
-paramstyle: str
-threadsafety: int
-apilevel: str
+paramstyle: Final = "qmark"
+threadsafety: Literal[0, 1, 3]
+apilevel: Final[str]
 Date = date
 Time = time
 Timestamp = datetime
@@ -235,7 +241,7 @@ def TimestampFromTicks(ticks: float) -> Timestamp: ...
 
 if sys.version_info < (3, 14):
     # Deprecated in 3.12, removed in 3.14.
-    version_info: tuple[int, int, int]
+    version_info: Final[tuple[int, int, int]]
 
-sqlite_version_info: tuple[int, int, int]
+sqlite_version_info: Final[tuple[int, int, int]]
 Binary = memoryview
diff --git a/mypy/typeshed/stdlib/sre_compile.pyi b/mypy/typeshed/stdlib/sre_compile.pyi
index 2d04a886c931..d8f0b7937e99 100644
--- a/mypy/typeshed/stdlib/sre_compile.pyi
+++ b/mypy/typeshed/stdlib/sre_compile.pyi
@@ -2,9 +2,9 @@ from re import Pattern
 from sre_constants import *
 from sre_constants import _NamedIntConstant
 from sre_parse import SubPattern
-from typing import Any
+from typing import Any, Final
 
-MAXCODE: int
+MAXCODE: Final[int]
 
 def dis(code: list[_NamedIntConstant]) -> None: ...
 def isstring(obj: Any) -> bool: ...
diff --git a/mypy/typeshed/stdlib/sre_constants.pyi b/mypy/typeshed/stdlib/sre_constants.pyi
index a3921aa0fc3b..9a1da4ac89e7 100644
--- a/mypy/typeshed/stdlib/sre_constants.pyi
+++ b/mypy/typeshed/stdlib/sre_constants.pyi
@@ -1,15 +1,22 @@
 import sys
 from re import error as error
 from typing import Final
-from typing_extensions import Self
+from typing_extensions import Self, disjoint_base
 
 MAXGROUPS: Final[int]
 
 MAGIC: Final[int]
 
-class _NamedIntConstant(int):
-    name: str
-    def __new__(cls, value: int, name: str) -> Self: ...
+if sys.version_info >= (3, 12):
+    class _NamedIntConstant(int):
+        name: str
+        def __new__(cls, value: int, name: str) -> Self: ...
+
+else:
+    @disjoint_base
+    class _NamedIntConstant(int):
+        name: str
+        def __new__(cls, value: int, name: str) -> Self: ...
 
 MAXREPEAT: Final[_NamedIntConstant]
 OPCODES: list[_NamedIntConstant]
diff --git a/mypy/typeshed/stdlib/sre_parse.pyi b/mypy/typeshed/stdlib/sre_parse.pyi
index c242bd2a065f..eaacbff312a9 100644
--- a/mypy/typeshed/stdlib/sre_parse.pyi
+++ b/mypy/typeshed/stdlib/sre_parse.pyi
@@ -3,24 +3,24 @@ from collections.abc import Iterable
 from re import Match, Pattern as _Pattern
 from sre_constants import *
 from sre_constants import _NamedIntConstant as _NIC, error as _Error
-from typing import Any, overload
+from typing import Any, Final, overload
 from typing_extensions import TypeAlias
 
-SPECIAL_CHARS: str
-REPEAT_CHARS: str
-DIGITS: frozenset[str]
-OCTDIGITS: frozenset[str]
-HEXDIGITS: frozenset[str]
-ASCIILETTERS: frozenset[str]
-WHITESPACE: frozenset[str]
-ESCAPES: dict[str, tuple[_NIC, int]]
-CATEGORIES: dict[str, tuple[_NIC, _NIC] | tuple[_NIC, list[tuple[_NIC, _NIC]]]]
-FLAGS: dict[str, int]
-TYPE_FLAGS: int
-GLOBAL_FLAGS: int
+SPECIAL_CHARS: Final = ".\\[{()*+?^$|"
+REPEAT_CHARS: Final = "*+?{"
+DIGITS: Final[frozenset[str]]
+OCTDIGITS: Final[frozenset[str]]
+HEXDIGITS: Final[frozenset[str]]
+ASCIILETTERS: Final[frozenset[str]]
+WHITESPACE: Final[frozenset[str]]
+ESCAPES: Final[dict[str, tuple[_NIC, int]]]
+CATEGORIES: Final[dict[str, tuple[_NIC, _NIC] | tuple[_NIC, list[tuple[_NIC, _NIC]]]]]
+FLAGS: Final[dict[str, int]]
+TYPE_FLAGS: Final[int]
+GLOBAL_FLAGS: Final[int]
 
 if sys.version_info >= (3, 11):
-    MAXWIDTH: int
+    MAXWIDTH: Final[int]
 
 if sys.version_info < (3, 11):
     class Verbose(Exception): ...
@@ -39,7 +39,7 @@ class State:
     lookbehindgroups: int | None
     @property
     def groups(self) -> int: ...
-    def opengroup(self, name: str | None = ...) -> int: ...
+    def opengroup(self, name: str | None = None) -> int: ...
     def closegroup(self, gid: int, p: SubPattern) -> None: ...
     def checkgroup(self, gid: int) -> bool: ...
     def checklookbehindgroup(self, gid: int, source: Tokenizer) -> None: ...
diff --git a/mypy/typeshed/stdlib/ssl.pyi b/mypy/typeshed/stdlib/ssl.pyi
index 9fbf5e8dfa84..faa98cb39920 100644
--- a/mypy/typeshed/stdlib/ssl.pyi
+++ b/mypy/typeshed/stdlib/ssl.pyi
@@ -27,7 +27,7 @@ from _ssl import (
 )
 from _typeshed import ReadableBuffer, StrOrBytesPath, WriteableBuffer
 from collections.abc import Callable, Iterable
-from typing import Any, Literal, NamedTuple, TypedDict, overload, type_check_only
+from typing import Any, Final, Literal, NamedTuple, TypedDict, overload, type_check_only
 from typing_extensions import Never, Self, TypeAlias, deprecated
 
 if sys.version_info >= (3, 13):
@@ -50,6 +50,7 @@ _SrvnmeCbType: TypeAlias = Callable[[SSLSocket | SSLObject, str | None, SSLSocke
 
 socket_error = OSError
 
+@type_check_only
 class _Cipher(TypedDict):
     aead: bool
     alg_bits: int
@@ -80,6 +81,7 @@ class SSLCertVerificationError(SSLError, ValueError):
 CertificateError = SSLCertVerificationError
 
 if sys.version_info < (3, 12):
+    @deprecated("Deprecated since Python 3.7; removed in Python 3.12. Use `SSLContext.wrap_socket()` instead.")
     def wrap_socket(
         sock: socket.socket,
         keyfile: StrOrBytesPath | None = None,
@@ -92,46 +94,7 @@ if sys.version_info < (3, 12):
         suppress_ragged_eofs: bool = True,
         ciphers: str | None = None,
     ) -> SSLSocket: ...
-
-def create_default_context(
-    purpose: Purpose = ...,
-    *,
-    cafile: StrOrBytesPath | None = None,
-    capath: StrOrBytesPath | None = None,
-    cadata: str | ReadableBuffer | None = None,
-) -> SSLContext: ...
-
-if sys.version_info >= (3, 10):
-    def _create_unverified_context(
-        protocol: int | None = None,
-        *,
-        cert_reqs: int = ...,
-        check_hostname: bool = False,
-        purpose: Purpose = ...,
-        certfile: StrOrBytesPath | None = None,
-        keyfile: StrOrBytesPath | None = None,
-        cafile: StrOrBytesPath | None = None,
-        capath: StrOrBytesPath | None = None,
-        cadata: str | ReadableBuffer | None = None,
-    ) -> SSLContext: ...
-
-else:
-    def _create_unverified_context(
-        protocol: int = ...,
-        *,
-        cert_reqs: int = ...,
-        check_hostname: bool = False,
-        purpose: Purpose = ...,
-        certfile: StrOrBytesPath | None = None,
-        keyfile: StrOrBytesPath | None = None,
-        cafile: StrOrBytesPath | None = None,
-        capath: StrOrBytesPath | None = None,
-        cadata: str | ReadableBuffer | None = None,
-    ) -> SSLContext: ...
-
-_create_default_https_context: Callable[..., SSLContext]
-
-if sys.version_info < (3, 12):
+    @deprecated("Deprecated since Python 3.7; removed in Python 3.12.")
     def match_hostname(cert: _PeerCertRetDictType, hostname: str) -> None: ...
 
 def cert_time_to_seconds(cert_time: str) -> int: ...
@@ -162,9 +125,9 @@ class VerifyMode(enum.IntEnum):
     CERT_OPTIONAL = 1
     CERT_REQUIRED = 2
 
-CERT_NONE: VerifyMode
-CERT_OPTIONAL: VerifyMode
-CERT_REQUIRED: VerifyMode
+CERT_NONE: Final = VerifyMode.CERT_NONE
+CERT_OPTIONAL: Final = VerifyMode.CERT_OPTIONAL
+CERT_REQUIRED: Final = VerifyMode.CERT_REQUIRED
 
 class VerifyFlags(enum.IntFlag):
     VERIFY_DEFAULT = 0
@@ -176,15 +139,15 @@ class VerifyFlags(enum.IntFlag):
         VERIFY_ALLOW_PROXY_CERTS = 64
         VERIFY_X509_PARTIAL_CHAIN = 524288
 
-VERIFY_DEFAULT: VerifyFlags
-VERIFY_CRL_CHECK_LEAF: VerifyFlags
-VERIFY_CRL_CHECK_CHAIN: VerifyFlags
-VERIFY_X509_STRICT: VerifyFlags
-VERIFY_X509_TRUSTED_FIRST: VerifyFlags
+VERIFY_DEFAULT: Final = VerifyFlags.VERIFY_DEFAULT
+VERIFY_CRL_CHECK_LEAF: Final = VerifyFlags.VERIFY_CRL_CHECK_LEAF
+VERIFY_CRL_CHECK_CHAIN: Final = VerifyFlags.VERIFY_CRL_CHECK_CHAIN
+VERIFY_X509_STRICT: Final = VerifyFlags.VERIFY_X509_STRICT
+VERIFY_X509_TRUSTED_FIRST: Final = VerifyFlags.VERIFY_X509_TRUSTED_FIRST
 
 if sys.version_info >= (3, 10):
-    VERIFY_ALLOW_PROXY_CERTS: VerifyFlags
-    VERIFY_X509_PARTIAL_CHAIN: VerifyFlags
+    VERIFY_ALLOW_PROXY_CERTS: Final = VerifyFlags.VERIFY_ALLOW_PROXY_CERTS
+    VERIFY_X509_PARTIAL_CHAIN: Final = VerifyFlags.VERIFY_X509_PARTIAL_CHAIN
 
 class _SSLMethod(enum.IntEnum):
     PROTOCOL_SSLv23 = 2
@@ -197,15 +160,15 @@ class _SSLMethod(enum.IntEnum):
     PROTOCOL_TLS_CLIENT = 16
     PROTOCOL_TLS_SERVER = 17
 
-PROTOCOL_SSLv23: _SSLMethod
-PROTOCOL_SSLv2: _SSLMethod
-PROTOCOL_SSLv3: _SSLMethod
-PROTOCOL_TLSv1: _SSLMethod
-PROTOCOL_TLSv1_1: _SSLMethod
-PROTOCOL_TLSv1_2: _SSLMethod
-PROTOCOL_TLS: _SSLMethod
-PROTOCOL_TLS_CLIENT: _SSLMethod
-PROTOCOL_TLS_SERVER: _SSLMethod
+PROTOCOL_SSLv23: Final = _SSLMethod.PROTOCOL_SSLv23
+PROTOCOL_SSLv2: Final = _SSLMethod.PROTOCOL_SSLv2
+PROTOCOL_SSLv3: Final = _SSLMethod.PROTOCOL_SSLv3
+PROTOCOL_TLSv1: Final = _SSLMethod.PROTOCOL_TLSv1
+PROTOCOL_TLSv1_1: Final = _SSLMethod.PROTOCOL_TLSv1_1
+PROTOCOL_TLSv1_2: Final = _SSLMethod.PROTOCOL_TLSv1_2
+PROTOCOL_TLS: Final = _SSLMethod.PROTOCOL_TLS
+PROTOCOL_TLS_CLIENT: Final = _SSLMethod.PROTOCOL_TLS_CLIENT
+PROTOCOL_TLS_SERVER: Final = _SSLMethod.PROTOCOL_TLS_SERVER
 
 class Options(enum.IntFlag):
     OP_ALL = 2147483728
@@ -228,29 +191,29 @@ class Options(enum.IntFlag):
     if sys.version_info >= (3, 11) or sys.platform == "linux":
         OP_IGNORE_UNEXPECTED_EOF = 128
 
-OP_ALL: Options
-OP_NO_SSLv2: Options
-OP_NO_SSLv3: Options
-OP_NO_TLSv1: Options
-OP_NO_TLSv1_1: Options
-OP_NO_TLSv1_2: Options
-OP_NO_TLSv1_3: Options
-OP_CIPHER_SERVER_PREFERENCE: Options
-OP_SINGLE_DH_USE: Options
-OP_SINGLE_ECDH_USE: Options
-OP_NO_COMPRESSION: Options
-OP_NO_TICKET: Options
-OP_NO_RENEGOTIATION: Options
-OP_ENABLE_MIDDLEBOX_COMPAT: Options
+OP_ALL: Final = Options.OP_ALL
+OP_NO_SSLv2: Final = Options.OP_NO_SSLv2
+OP_NO_SSLv3: Final = Options.OP_NO_SSLv3
+OP_NO_TLSv1: Final = Options.OP_NO_TLSv1
+OP_NO_TLSv1_1: Final = Options.OP_NO_TLSv1_1
+OP_NO_TLSv1_2: Final = Options.OP_NO_TLSv1_2
+OP_NO_TLSv1_3: Final = Options.OP_NO_TLSv1_3
+OP_CIPHER_SERVER_PREFERENCE: Final = Options.OP_CIPHER_SERVER_PREFERENCE
+OP_SINGLE_DH_USE: Final = Options.OP_SINGLE_DH_USE
+OP_SINGLE_ECDH_USE: Final = Options.OP_SINGLE_ECDH_USE
+OP_NO_COMPRESSION: Final = Options.OP_NO_COMPRESSION
+OP_NO_TICKET: Final = Options.OP_NO_TICKET
+OP_NO_RENEGOTIATION: Final = Options.OP_NO_RENEGOTIATION
+OP_ENABLE_MIDDLEBOX_COMPAT: Final = Options.OP_ENABLE_MIDDLEBOX_COMPAT
 if sys.version_info >= (3, 12):
-    OP_LEGACY_SERVER_CONNECT: Options
-    OP_ENABLE_KTLS: Options
+    OP_LEGACY_SERVER_CONNECT: Final = Options.OP_LEGACY_SERVER_CONNECT
+    OP_ENABLE_KTLS: Final = Options.OP_ENABLE_KTLS
 if sys.version_info >= (3, 11) or sys.platform == "linux":
-    OP_IGNORE_UNEXPECTED_EOF: Options
+    OP_IGNORE_UNEXPECTED_EOF: Final = Options.OP_IGNORE_UNEXPECTED_EOF
 
-HAS_NEVER_CHECK_COMMON_NAME: bool
+HAS_NEVER_CHECK_COMMON_NAME: Final[bool]
 
-CHANNEL_BINDING_TYPES: list[str]
+CHANNEL_BINDING_TYPES: Final[list[str]]
 
 class AlertDescription(enum.IntEnum):
     ALERT_DESCRIPTION_ACCESS_DENIED = 49
@@ -281,33 +244,33 @@ class AlertDescription(enum.IntEnum):
     ALERT_DESCRIPTION_UNSUPPORTED_EXTENSION = 110
     ALERT_DESCRIPTION_USER_CANCELLED = 90
 
-ALERT_DESCRIPTION_HANDSHAKE_FAILURE: AlertDescription
-ALERT_DESCRIPTION_INTERNAL_ERROR: AlertDescription
-ALERT_DESCRIPTION_ACCESS_DENIED: AlertDescription
-ALERT_DESCRIPTION_BAD_CERTIFICATE: AlertDescription
-ALERT_DESCRIPTION_BAD_CERTIFICATE_HASH_VALUE: AlertDescription
-ALERT_DESCRIPTION_BAD_CERTIFICATE_STATUS_RESPONSE: AlertDescription
-ALERT_DESCRIPTION_BAD_RECORD_MAC: AlertDescription
-ALERT_DESCRIPTION_CERTIFICATE_EXPIRED: AlertDescription
-ALERT_DESCRIPTION_CERTIFICATE_REVOKED: AlertDescription
-ALERT_DESCRIPTION_CERTIFICATE_UNKNOWN: AlertDescription
-ALERT_DESCRIPTION_CERTIFICATE_UNOBTAINABLE: AlertDescription
-ALERT_DESCRIPTION_CLOSE_NOTIFY: AlertDescription
-ALERT_DESCRIPTION_DECODE_ERROR: AlertDescription
-ALERT_DESCRIPTION_DECOMPRESSION_FAILURE: AlertDescription
-ALERT_DESCRIPTION_DECRYPT_ERROR: AlertDescription
-ALERT_DESCRIPTION_ILLEGAL_PARAMETER: AlertDescription
-ALERT_DESCRIPTION_INSUFFICIENT_SECURITY: AlertDescription
-ALERT_DESCRIPTION_NO_RENEGOTIATION: AlertDescription
-ALERT_DESCRIPTION_PROTOCOL_VERSION: AlertDescription
-ALERT_DESCRIPTION_RECORD_OVERFLOW: AlertDescription
-ALERT_DESCRIPTION_UNEXPECTED_MESSAGE: AlertDescription
-ALERT_DESCRIPTION_UNKNOWN_CA: AlertDescription
-ALERT_DESCRIPTION_UNKNOWN_PSK_IDENTITY: AlertDescription
-ALERT_DESCRIPTION_UNRECOGNIZED_NAME: AlertDescription
-ALERT_DESCRIPTION_UNSUPPORTED_CERTIFICATE: AlertDescription
-ALERT_DESCRIPTION_UNSUPPORTED_EXTENSION: AlertDescription
-ALERT_DESCRIPTION_USER_CANCELLED: AlertDescription
+ALERT_DESCRIPTION_HANDSHAKE_FAILURE: Final = AlertDescription.ALERT_DESCRIPTION_HANDSHAKE_FAILURE
+ALERT_DESCRIPTION_INTERNAL_ERROR: Final = AlertDescription.ALERT_DESCRIPTION_INTERNAL_ERROR
+ALERT_DESCRIPTION_ACCESS_DENIED: Final = AlertDescription.ALERT_DESCRIPTION_ACCESS_DENIED
+ALERT_DESCRIPTION_BAD_CERTIFICATE: Final = AlertDescription.ALERT_DESCRIPTION_BAD_CERTIFICATE
+ALERT_DESCRIPTION_BAD_CERTIFICATE_HASH_VALUE: Final = AlertDescription.ALERT_DESCRIPTION_BAD_CERTIFICATE_HASH_VALUE
+ALERT_DESCRIPTION_BAD_CERTIFICATE_STATUS_RESPONSE: Final = AlertDescription.ALERT_DESCRIPTION_BAD_CERTIFICATE_STATUS_RESPONSE
+ALERT_DESCRIPTION_BAD_RECORD_MAC: Final = AlertDescription.ALERT_DESCRIPTION_BAD_RECORD_MAC
+ALERT_DESCRIPTION_CERTIFICATE_EXPIRED: Final = AlertDescription.ALERT_DESCRIPTION_CERTIFICATE_EXPIRED
+ALERT_DESCRIPTION_CERTIFICATE_REVOKED: Final = AlertDescription.ALERT_DESCRIPTION_CERTIFICATE_REVOKED
+ALERT_DESCRIPTION_CERTIFICATE_UNKNOWN: Final = AlertDescription.ALERT_DESCRIPTION_CERTIFICATE_UNKNOWN
+ALERT_DESCRIPTION_CERTIFICATE_UNOBTAINABLE: Final = AlertDescription.ALERT_DESCRIPTION_CERTIFICATE_UNOBTAINABLE
+ALERT_DESCRIPTION_CLOSE_NOTIFY: Final = AlertDescription.ALERT_DESCRIPTION_CLOSE_NOTIFY
+ALERT_DESCRIPTION_DECODE_ERROR: Final = AlertDescription.ALERT_DESCRIPTION_DECODE_ERROR
+ALERT_DESCRIPTION_DECOMPRESSION_FAILURE: Final = AlertDescription.ALERT_DESCRIPTION_DECOMPRESSION_FAILURE
+ALERT_DESCRIPTION_DECRYPT_ERROR: Final = AlertDescription.ALERT_DESCRIPTION_DECRYPT_ERROR
+ALERT_DESCRIPTION_ILLEGAL_PARAMETER: Final = AlertDescription.ALERT_DESCRIPTION_ILLEGAL_PARAMETER
+ALERT_DESCRIPTION_INSUFFICIENT_SECURITY: Final = AlertDescription.ALERT_DESCRIPTION_INSUFFICIENT_SECURITY
+ALERT_DESCRIPTION_NO_RENEGOTIATION: Final = AlertDescription.ALERT_DESCRIPTION_NO_RENEGOTIATION
+ALERT_DESCRIPTION_PROTOCOL_VERSION: Final = AlertDescription.ALERT_DESCRIPTION_PROTOCOL_VERSION
+ALERT_DESCRIPTION_RECORD_OVERFLOW: Final = AlertDescription.ALERT_DESCRIPTION_RECORD_OVERFLOW
+ALERT_DESCRIPTION_UNEXPECTED_MESSAGE: Final = AlertDescription.ALERT_DESCRIPTION_UNEXPECTED_MESSAGE
+ALERT_DESCRIPTION_UNKNOWN_CA: Final = AlertDescription.ALERT_DESCRIPTION_UNKNOWN_CA
+ALERT_DESCRIPTION_UNKNOWN_PSK_IDENTITY: Final = AlertDescription.ALERT_DESCRIPTION_UNKNOWN_PSK_IDENTITY
+ALERT_DESCRIPTION_UNRECOGNIZED_NAME: Final = AlertDescription.ALERT_DESCRIPTION_UNRECOGNIZED_NAME
+ALERT_DESCRIPTION_UNSUPPORTED_CERTIFICATE: Final = AlertDescription.ALERT_DESCRIPTION_UNSUPPORTED_CERTIFICATE
+ALERT_DESCRIPTION_UNSUPPORTED_EXTENSION: Final = AlertDescription.ALERT_DESCRIPTION_UNSUPPORTED_EXTENSION
+ALERT_DESCRIPTION_USER_CANCELLED: Final = AlertDescription.ALERT_DESCRIPTION_USER_CANCELLED
 
 # This class is not exposed. It calls itself ssl._ASN1Object.
 @type_check_only
@@ -370,7 +333,7 @@ class SSLSocket(socket.socket):
     def get_channel_binding(self, cb_type: str = "tls-unique") -> bytes | None: ...
     def selected_alpn_protocol(self) -> str | None: ...
     if sys.version_info >= (3, 10):
-        @deprecated("Deprecated in 3.10. Use ALPN instead.")
+        @deprecated("Deprecated since Python 3.10. Use ALPN instead.")
         def selected_npn_protocol(self) -> str | None: ...
     else:
         def selected_npn_protocol(self) -> str | None: ...
@@ -416,13 +379,15 @@ class SSLContext(_SSLContext):
     if sys.version_info >= (3, 10):
         security_level: int
     if sys.version_info >= (3, 10):
-        # Using the default (None) for the `protocol` parameter is deprecated,
-        # but there isn't a good way of marking that in the stub unless/until PEP 702 is accepted
-        def __new__(cls, protocol: int | None = None, *args: Any, **kwargs: Any) -> Self: ...
+        @overload
+        def __new__(cls, protocol: int, *args: Any, **kwargs: Any) -> Self: ...
+        @overload
+        @deprecated("Deprecated since Python 3.10. Use a specific version of the SSL protocol.")
+        def __new__(cls, protocol: None = None, *args: Any, **kwargs: Any) -> Self: ...
     else:
         def __new__(cls, protocol: int = ..., *args: Any, **kwargs: Any) -> Self: ...
 
-    def load_default_certs(self, purpose: Purpose = ...) -> None: ...
+    def load_default_certs(self, purpose: Purpose = Purpose.SERVER_AUTH) -> None: ...
     def load_verify_locations(
         self,
         cafile: StrOrBytesPath | None = None,
@@ -440,7 +405,7 @@ class SSLContext(_SSLContext):
     def set_ciphers(self, cipherlist: str, /) -> None: ...
     def set_alpn_protocols(self, alpn_protocols: Iterable[str]) -> None: ...
     if sys.version_info >= (3, 10):
-        @deprecated("Deprecated in 3.10. Use ALPN instead.")
+        @deprecated("Deprecated since Python 3.10. Use ALPN instead.")
         def set_npn_protocols(self, npn_protocols: Iterable[str]) -> None: ...
     else:
         def set_npn_protocols(self, npn_protocols: Iterable[str]) -> None: ...
@@ -466,6 +431,44 @@ class SSLContext(_SSLContext):
         session: SSLSession | None = None,
     ) -> SSLObject: ...
 
+def create_default_context(
+    purpose: Purpose = Purpose.SERVER_AUTH,
+    *,
+    cafile: StrOrBytesPath | None = None,
+    capath: StrOrBytesPath | None = None,
+    cadata: str | ReadableBuffer | None = None,
+) -> SSLContext: ...
+
+if sys.version_info >= (3, 10):
+    def _create_unverified_context(
+        protocol: int | None = None,
+        *,
+        cert_reqs: int = ...,
+        check_hostname: bool = False,
+        purpose: Purpose = Purpose.SERVER_AUTH,
+        certfile: StrOrBytesPath | None = None,
+        keyfile: StrOrBytesPath | None = None,
+        cafile: StrOrBytesPath | None = None,
+        capath: StrOrBytesPath | None = None,
+        cadata: str | ReadableBuffer | None = None,
+    ) -> SSLContext: ...
+
+else:
+    def _create_unverified_context(
+        protocol: int = ...,
+        *,
+        cert_reqs: int = ...,
+        check_hostname: bool = False,
+        purpose: Purpose = Purpose.SERVER_AUTH,
+        certfile: StrOrBytesPath | None = None,
+        keyfile: StrOrBytesPath | None = None,
+        cafile: StrOrBytesPath | None = None,
+        capath: StrOrBytesPath | None = None,
+        cadata: str | ReadableBuffer | None = None,
+    ) -> SSLContext: ...
+
+_create_default_https_context = create_default_context
+
 class SSLObject:
     context: SSLContext
     @property
@@ -486,7 +489,7 @@ class SSLObject:
     def getpeercert(self, binary_form: bool) -> _PeerCertRetType: ...
     def selected_alpn_protocol(self) -> str | None: ...
     if sys.version_info >= (3, 10):
-        @deprecated("Deprecated in 3.10. Use ALPN instead.")
+        @deprecated("Deprecated since Python 3.10. Use ALPN instead.")
         def selected_npn_protocol(self) -> str | None: ...
     else:
         def selected_npn_protocol(self) -> str | None: ...
@@ -515,20 +518,20 @@ class SSLErrorNumber(enum.IntEnum):
     SSL_ERROR_WANT_X509_LOOKUP = 4
     SSL_ERROR_ZERO_RETURN = 6
 
-SSL_ERROR_EOF: SSLErrorNumber  # undocumented
-SSL_ERROR_INVALID_ERROR_CODE: SSLErrorNumber  # undocumented
-SSL_ERROR_SSL: SSLErrorNumber  # undocumented
-SSL_ERROR_SYSCALL: SSLErrorNumber  # undocumented
-SSL_ERROR_WANT_CONNECT: SSLErrorNumber  # undocumented
-SSL_ERROR_WANT_READ: SSLErrorNumber  # undocumented
-SSL_ERROR_WANT_WRITE: SSLErrorNumber  # undocumented
-SSL_ERROR_WANT_X509_LOOKUP: SSLErrorNumber  # undocumented
-SSL_ERROR_ZERO_RETURN: SSLErrorNumber  # undocumented
+SSL_ERROR_EOF: Final = SSLErrorNumber.SSL_ERROR_EOF  # undocumented
+SSL_ERROR_INVALID_ERROR_CODE: Final = SSLErrorNumber.SSL_ERROR_INVALID_ERROR_CODE  # undocumented
+SSL_ERROR_SSL: Final = SSLErrorNumber.SSL_ERROR_SSL  # undocumented
+SSL_ERROR_SYSCALL: Final = SSLErrorNumber.SSL_ERROR_SYSCALL  # undocumented
+SSL_ERROR_WANT_CONNECT: Final = SSLErrorNumber.SSL_ERROR_WANT_CONNECT  # undocumented
+SSL_ERROR_WANT_READ: Final = SSLErrorNumber.SSL_ERROR_WANT_READ  # undocumented
+SSL_ERROR_WANT_WRITE: Final = SSLErrorNumber.SSL_ERROR_WANT_WRITE  # undocumented
+SSL_ERROR_WANT_X509_LOOKUP: Final = SSLErrorNumber.SSL_ERROR_WANT_X509_LOOKUP  # undocumented
+SSL_ERROR_ZERO_RETURN: Final = SSLErrorNumber.SSL_ERROR_ZERO_RETURN  # undocumented
 
 def get_protocol_name(protocol_code: int) -> str: ...
 
-PEM_FOOTER: str
-PEM_HEADER: str
-SOCK_STREAM: int
-SOL_SOCKET: int
-SO_TYPE: int
+PEM_FOOTER: Final[str]
+PEM_HEADER: Final[str]
+SOCK_STREAM: Final = socket.SOCK_STREAM
+SOL_SOCKET: Final = socket.SOL_SOCKET
+SO_TYPE: Final = socket.SO_TYPE
diff --git a/mypy/typeshed/stdlib/statistics.pyi b/mypy/typeshed/stdlib/statistics.pyi
index 6d7d3fbb4956..ba9e5f1b6b71 100644
--- a/mypy/typeshed/stdlib/statistics.pyi
+++ b/mypy/typeshed/stdlib/statistics.pyi
@@ -79,6 +79,7 @@ def stdev(data: Iterable[_NumberT], xbar: _NumberT | None = None) -> _NumberT: .
 def variance(data: Iterable[_NumberT], xbar: _NumberT | None = None) -> _NumberT: ...
 
 class NormalDist:
+    __slots__ = {"_mu": "Arithmetic mean of a normal distribution", "_sigma": "Standard deviation of a normal distribution"}
     def __init__(self, mu: float = 0.0, sigma: float = 1.0) -> None: ...
     @property
     def mean(self) -> float: ...
diff --git a/mypy/typeshed/stdlib/string/__init__.pyi b/mypy/typeshed/stdlib/string/__init__.pyi
index 29fe27f39b80..c8b32a98e26d 100644
--- a/mypy/typeshed/stdlib/string/__init__.pyi
+++ b/mypy/typeshed/stdlib/string/__init__.pyi
@@ -2,7 +2,7 @@ import sys
 from _typeshed import StrOrLiteralStr
 from collections.abc import Iterable, Mapping, Sequence
 from re import Pattern, RegexFlag
-from typing import Any, ClassVar, overload
+from typing import Any, ClassVar, Final, overload
 from typing_extensions import LiteralString
 
 __all__ = [
@@ -20,15 +20,15 @@ __all__ = [
     "Template",
 ]
 
-ascii_letters: LiteralString
-ascii_lowercase: LiteralString
-ascii_uppercase: LiteralString
-digits: LiteralString
-hexdigits: LiteralString
-octdigits: LiteralString
-punctuation: LiteralString
-printable: LiteralString
-whitespace: LiteralString
+whitespace: Final = " \t\n\r\v\f"
+ascii_lowercase: Final = "abcdefghijklmnopqrstuvwxyz"
+ascii_uppercase: Final = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+ascii_letters: Final[LiteralString]  # string too long
+digits: Final = "0123456789"
+hexdigits: Final = "0123456789abcdefABCDEF"
+octdigits: Final = "01234567"
+punctuation: Final = r"""!"#$%&'()*+,-./:;<=>?@[\]^_`{|}~"""
+printable: Final[LiteralString]  # string too long
 
 def capwords(s: StrOrLiteralStr, sep: StrOrLiteralStr | None = None) -> StrOrLiteralStr: ...
 
diff --git a/mypy/typeshed/stdlib/string/templatelib.pyi b/mypy/typeshed/stdlib/string/templatelib.pyi
index 324447f5f34c..9906d31c6391 100644
--- a/mypy/typeshed/stdlib/string/templatelib.pyi
+++ b/mypy/typeshed/stdlib/string/templatelib.pyi
@@ -1,8 +1,8 @@
 from collections.abc import Iterator
 from types import GenericAlias
-from typing import Any, Literal, final
+from typing import Any, Literal, TypeVar, final, overload
 
-__all__ = ["Interpolation", "Template"]
+_T = TypeVar("_T")
 
 @final
 class Template:  # TODO: consider making `Template` generic on `TypeVarTuple`
@@ -11,7 +11,7 @@ class Template:  # TODO: consider making `Template` generic on `TypeVarTuple`
 
     def __new__(cls, *args: str | Interpolation) -> Template: ...
     def __iter__(self) -> Iterator[str | Interpolation]: ...
-    def __add__(self, other: Template | str) -> Template: ...
+    def __add__(self, other: Template, /) -> Template: ...
     def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
     @property
     def values(self) -> tuple[Any, ...]: ...  # Tuple of interpolation values, which can have any type
@@ -26,6 +26,11 @@ class Interpolation:
     __match_args__ = ("value", "expression", "conversion", "format_spec")
 
     def __new__(
-        cls, value: Any, expression: str, conversion: Literal["a", "r", "s"] | None = None, format_spec: str = ""
+        cls, value: Any, expression: str = "", conversion: Literal["a", "r", "s"] | None = None, format_spec: str = ""
     ) -> Interpolation: ...
     def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
+
+@overload
+def convert(obj: _T, /, conversion: None) -> _T: ...
+@overload
+def convert(obj: object, /, conversion: Literal["r", "s", "a"]) -> str: ...
diff --git a/mypy/typeshed/stdlib/stringprep.pyi b/mypy/typeshed/stdlib/stringprep.pyi
index fc28c027ca9b..d67955e499c8 100644
--- a/mypy/typeshed/stdlib/stringprep.pyi
+++ b/mypy/typeshed/stdlib/stringprep.pyi
@@ -1,10 +1,12 @@
-b1_set: set[int]
-b3_exceptions: dict[int, str]
-c22_specials: set[int]
-c6_set: set[int]
-c7_set: set[int]
-c8_set: set[int]
-c9_set: set[int]
+from typing import Final
+
+b1_set: Final[set[int]]
+b3_exceptions: Final[dict[int, str]]
+c22_specials: Final[set[int]]
+c6_set: Final[set[int]]
+c7_set: Final[set[int]]
+c8_set: Final[set[int]]
+c9_set: Final[set[int]]
 
 def in_table_a1(code: str) -> bool: ...
 def in_table_b1(code: str) -> bool: ...
diff --git a/mypy/typeshed/stdlib/subprocess.pyi b/mypy/typeshed/stdlib/subprocess.pyi
index 8b72e2ec7ae2..e1e25bcb50cb 100644
--- a/mypy/typeshed/stdlib/subprocess.pyi
+++ b/mypy/typeshed/stdlib/subprocess.pyi
@@ -106,7 +106,7 @@ if sys.version_info >= (3, 11):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         capture_output: bool = False,
         check: bool = False,
@@ -140,7 +140,7 @@ if sys.version_info >= (3, 11):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         capture_output: bool = False,
         check: bool = False,
@@ -174,7 +174,7 @@ if sys.version_info >= (3, 11):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         capture_output: bool = False,
         check: bool = False,
@@ -209,7 +209,7 @@ if sys.version_info >= (3, 11):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         # where the *real* keyword only args start
         capture_output: bool = False,
         check: bool = False,
@@ -243,7 +243,7 @@ if sys.version_info >= (3, 11):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         capture_output: bool = False,
         check: bool = False,
@@ -277,7 +277,7 @@ if sys.version_info >= (3, 11):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         capture_output: bool = False,
         check: bool = False,
@@ -314,7 +314,7 @@ elif sys.version_info >= (3, 10):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         capture_output: bool = False,
         check: bool = False,
@@ -347,7 +347,7 @@ elif sys.version_info >= (3, 10):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         capture_output: bool = False,
         check: bool = False,
@@ -380,7 +380,7 @@ elif sys.version_info >= (3, 10):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         capture_output: bool = False,
         check: bool = False,
@@ -414,7 +414,7 @@ elif sys.version_info >= (3, 10):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         # where the *real* keyword only args start
         capture_output: bool = False,
         check: bool = False,
@@ -447,7 +447,7 @@ elif sys.version_info >= (3, 10):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         capture_output: bool = False,
         check: bool = False,
@@ -480,7 +480,7 @@ elif sys.version_info >= (3, 10):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         capture_output: bool = False,
         check: bool = False,
@@ -516,7 +516,7 @@ else:
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         capture_output: bool = False,
         check: bool = False,
@@ -548,7 +548,7 @@ else:
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         capture_output: bool = False,
         check: bool = False,
@@ -580,7 +580,7 @@ else:
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         capture_output: bool = False,
         check: bool = False,
@@ -613,7 +613,7 @@ else:
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         # where the *real* keyword only args start
         capture_output: bool = False,
         check: bool = False,
@@ -645,7 +645,7 @@ else:
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         capture_output: bool = False,
         check: bool = False,
@@ -677,7 +677,7 @@ else:
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         capture_output: bool = False,
         check: bool = False,
@@ -712,7 +712,7 @@ if sys.version_info >= (3, 11):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         encoding: str | None = None,
         timeout: float | None = None,
@@ -744,7 +744,7 @@ elif sys.version_info >= (3, 10):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         encoding: str | None = None,
         timeout: float | None = None,
@@ -774,7 +774,7 @@ else:
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         encoding: str | None = None,
         timeout: float | None = None,
@@ -805,8 +805,8 @@ if sys.version_info >= (3, 11):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
-        timeout: float | None = ...,
+        pass_fds: Collection[int] = (),
+        timeout: float | None = None,
         *,
         encoding: str | None = None,
         text: bool | None = None,
@@ -837,8 +837,8 @@ elif sys.version_info >= (3, 10):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
-        timeout: float | None = ...,
+        pass_fds: Collection[int] = (),
+        timeout: float | None = None,
         *,
         encoding: str | None = None,
         text: bool | None = None,
@@ -867,8 +867,8 @@ else:
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
-        timeout: float | None = ...,
+        pass_fds: Collection[int] = (),
+        timeout: float | None = None,
         *,
         encoding: str | None = None,
         text: bool | None = None,
@@ -897,10 +897,10 @@ if sys.version_info >= (3, 11):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         timeout: float | None = None,
-        input: _InputString | None = ...,
+        input: _InputString | None = None,
         encoding: str | None = None,
         errors: str | None = None,
         text: Literal[True],
@@ -928,10 +928,10 @@ if sys.version_info >= (3, 11):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         timeout: float | None = None,
-        input: _InputString | None = ...,
+        input: _InputString | None = None,
         encoding: str,
         errors: str | None = None,
         text: bool | None = None,
@@ -959,10 +959,10 @@ if sys.version_info >= (3, 11):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         timeout: float | None = None,
-        input: _InputString | None = ...,
+        input: _InputString | None = None,
         encoding: str | None = None,
         errors: str,
         text: bool | None = None,
@@ -991,10 +991,10 @@ if sys.version_info >= (3, 11):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         # where the real keyword only ones start
         timeout: float | None = None,
-        input: _InputString | None = ...,
+        input: _InputString | None = None,
         encoding: str | None = None,
         errors: str | None = None,
         text: bool | None = None,
@@ -1022,10 +1022,10 @@ if sys.version_info >= (3, 11):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         timeout: float | None = None,
-        input: _InputString | None = ...,
+        input: _InputString | None = None,
         encoding: None = None,
         errors: None = None,
         text: Literal[False] | None = None,
@@ -1053,10 +1053,10 @@ if sys.version_info >= (3, 11):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         timeout: float | None = None,
-        input: _InputString | None = ...,
+        input: _InputString | None = None,
         encoding: str | None = None,
         errors: str | None = None,
         text: bool | None = None,
@@ -1087,10 +1087,10 @@ elif sys.version_info >= (3, 10):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         timeout: float | None = None,
-        input: _InputString | None = ...,
+        input: _InputString | None = None,
         encoding: str | None = None,
         errors: str | None = None,
         text: Literal[True],
@@ -1117,10 +1117,10 @@ elif sys.version_info >= (3, 10):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         timeout: float | None = None,
-        input: _InputString | None = ...,
+        input: _InputString | None = None,
         encoding: str,
         errors: str | None = None,
         text: bool | None = None,
@@ -1147,10 +1147,10 @@ elif sys.version_info >= (3, 10):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         timeout: float | None = None,
-        input: _InputString | None = ...,
+        input: _InputString | None = None,
         encoding: str | None = None,
         errors: str,
         text: bool | None = None,
@@ -1178,10 +1178,10 @@ elif sys.version_info >= (3, 10):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         # where the real keyword only ones start
         timeout: float | None = None,
-        input: _InputString | None = ...,
+        input: _InputString | None = None,
         encoding: str | None = None,
         errors: str | None = None,
         text: bool | None = None,
@@ -1208,10 +1208,10 @@ elif sys.version_info >= (3, 10):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         timeout: float | None = None,
-        input: _InputString | None = ...,
+        input: _InputString | None = None,
         encoding: None = None,
         errors: None = None,
         text: Literal[False] | None = None,
@@ -1238,10 +1238,10 @@ elif sys.version_info >= (3, 10):
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         timeout: float | None = None,
-        input: _InputString | None = ...,
+        input: _InputString | None = None,
         encoding: str | None = None,
         errors: str | None = None,
         text: bool | None = None,
@@ -1270,10 +1270,10 @@ else:
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         timeout: float | None = None,
-        input: _InputString | None = ...,
+        input: _InputString | None = None,
         encoding: str | None = None,
         errors: str | None = None,
         text: Literal[True],
@@ -1299,10 +1299,10 @@ else:
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         timeout: float | None = None,
-        input: _InputString | None = ...,
+        input: _InputString | None = None,
         encoding: str,
         errors: str | None = None,
         text: bool | None = None,
@@ -1328,10 +1328,10 @@ else:
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         timeout: float | None = None,
-        input: _InputString | None = ...,
+        input: _InputString | None = None,
         encoding: str | None = None,
         errors: str,
         text: bool | None = None,
@@ -1358,10 +1358,10 @@ else:
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         # where the real keyword only ones start
         timeout: float | None = None,
-        input: _InputString | None = ...,
+        input: _InputString | None = None,
         encoding: str | None = None,
         errors: str | None = None,
         text: bool | None = None,
@@ -1387,10 +1387,10 @@ else:
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         timeout: float | None = None,
-        input: _InputString | None = ...,
+        input: _InputString | None = None,
         encoding: None = None,
         errors: None = None,
         text: Literal[False] | None = None,
@@ -1416,10 +1416,10 @@ else:
         creationflags: int = 0,
         restore_signals: bool = True,
         start_new_session: bool = False,
-        pass_fds: Collection[int] = ...,
+        pass_fds: Collection[int] = (),
         *,
         timeout: float | None = None,
-        input: _InputString | None = ...,
+        input: _InputString | None = None,
         encoding: str | None = None,
         errors: str | None = None,
         text: bool | None = None,
diff --git a/mypy/typeshed/stdlib/sunau.pyi b/mypy/typeshed/stdlib/sunau.pyi
index d81645cb5687..f83a0a4c520e 100644
--- a/mypy/typeshed/stdlib/sunau.pyi
+++ b/mypy/typeshed/stdlib/sunau.pyi
@@ -1,25 +1,25 @@
 from _typeshed import Unused
-from typing import IO, Any, Literal, NamedTuple, NoReturn, overload
+from typing import IO, Any, Final, Literal, NamedTuple, NoReturn, overload
 from typing_extensions import Self, TypeAlias
 
 _File: TypeAlias = str | IO[bytes]
 
 class Error(Exception): ...
 
-AUDIO_FILE_MAGIC: int
-AUDIO_FILE_ENCODING_MULAW_8: int
-AUDIO_FILE_ENCODING_LINEAR_8: int
-AUDIO_FILE_ENCODING_LINEAR_16: int
-AUDIO_FILE_ENCODING_LINEAR_24: int
-AUDIO_FILE_ENCODING_LINEAR_32: int
-AUDIO_FILE_ENCODING_FLOAT: int
-AUDIO_FILE_ENCODING_DOUBLE: int
-AUDIO_FILE_ENCODING_ADPCM_G721: int
-AUDIO_FILE_ENCODING_ADPCM_G722: int
-AUDIO_FILE_ENCODING_ADPCM_G723_3: int
-AUDIO_FILE_ENCODING_ADPCM_G723_5: int
-AUDIO_FILE_ENCODING_ALAW_8: int
-AUDIO_UNKNOWN_SIZE: int
+AUDIO_FILE_MAGIC: Final = 0x2E736E64
+AUDIO_FILE_ENCODING_MULAW_8: Final = 1
+AUDIO_FILE_ENCODING_LINEAR_8: Final = 2
+AUDIO_FILE_ENCODING_LINEAR_16: Final = 3
+AUDIO_FILE_ENCODING_LINEAR_24: Final = 4
+AUDIO_FILE_ENCODING_LINEAR_32: Final = 5
+AUDIO_FILE_ENCODING_FLOAT: Final = 6
+AUDIO_FILE_ENCODING_DOUBLE: Final = 7
+AUDIO_FILE_ENCODING_ADPCM_G721: Final = 23
+AUDIO_FILE_ENCODING_ADPCM_G722: Final = 24
+AUDIO_FILE_ENCODING_ADPCM_G723_3: Final = 25
+AUDIO_FILE_ENCODING_ADPCM_G723_5: Final = 26
+AUDIO_FILE_ENCODING_ALAW_8: Final = 27
+AUDIO_UNKNOWN_SIZE: Final = 0xFFFFFFFF
 
 class _sunau_params(NamedTuple):
     nchannels: int
diff --git a/mypy/typeshed/stdlib/symbol.pyi b/mypy/typeshed/stdlib/symbol.pyi
index 48ae3567a1a5..5344ce504c6c 100644
--- a/mypy/typeshed/stdlib/symbol.pyi
+++ b/mypy/typeshed/stdlib/symbol.pyi
@@ -1,93 +1,95 @@
-single_input: int
-file_input: int
-eval_input: int
-decorator: int
-decorators: int
-decorated: int
-async_funcdef: int
-funcdef: int
-parameters: int
-typedargslist: int
-tfpdef: int
-varargslist: int
-vfpdef: int
-stmt: int
-simple_stmt: int
-small_stmt: int
-expr_stmt: int
-annassign: int
-testlist_star_expr: int
-augassign: int
-del_stmt: int
-pass_stmt: int
-flow_stmt: int
-break_stmt: int
-continue_stmt: int
-return_stmt: int
-yield_stmt: int
-raise_stmt: int
-import_stmt: int
-import_name: int
-import_from: int
-import_as_name: int
-dotted_as_name: int
-import_as_names: int
-dotted_as_names: int
-dotted_name: int
-global_stmt: int
-nonlocal_stmt: int
-assert_stmt: int
-compound_stmt: int
-async_stmt: int
-if_stmt: int
-while_stmt: int
-for_stmt: int
-try_stmt: int
-with_stmt: int
-with_item: int
-except_clause: int
-suite: int
-test: int
-test_nocond: int
-lambdef: int
-lambdef_nocond: int
-or_test: int
-and_test: int
-not_test: int
-comparison: int
-comp_op: int
-star_expr: int
-expr: int
-xor_expr: int
-and_expr: int
-shift_expr: int
-arith_expr: int
-term: int
-factor: int
-power: int
-atom_expr: int
-atom: int
-testlist_comp: int
-trailer: int
-subscriptlist: int
-subscript: int
-sliceop: int
-exprlist: int
-testlist: int
-dictorsetmaker: int
-classdef: int
-arglist: int
-argument: int
-comp_iter: int
-comp_for: int
-comp_if: int
-encoding_decl: int
-yield_expr: int
-yield_arg: int
-sync_comp_for: int
-func_body_suite: int
-func_type: int
-func_type_input: int
-namedexpr_test: int
-typelist: int
-sym_name: dict[int, str]
+from typing import Final
+
+single_input: Final[int]
+file_input: Final[int]
+eval_input: Final[int]
+decorator: Final[int]
+decorators: Final[int]
+decorated: Final[int]
+async_funcdef: Final[int]
+funcdef: Final[int]
+parameters: Final[int]
+typedargslist: Final[int]
+tfpdef: Final[int]
+varargslist: Final[int]
+vfpdef: Final[int]
+stmt: Final[int]
+simple_stmt: Final[int]
+small_stmt: Final[int]
+expr_stmt: Final[int]
+annassign: Final[int]
+testlist_star_expr: Final[int]
+augassign: Final[int]
+del_stmt: Final[int]
+pass_stmt: Final[int]
+flow_stmt: Final[int]
+break_stmt: Final[int]
+continue_stmt: Final[int]
+return_stmt: Final[int]
+yield_stmt: Final[int]
+raise_stmt: Final[int]
+import_stmt: Final[int]
+import_name: Final[int]
+import_from: Final[int]
+import_as_name: Final[int]
+dotted_as_name: Final[int]
+import_as_names: Final[int]
+dotted_as_names: Final[int]
+dotted_name: Final[int]
+global_stmt: Final[int]
+nonlocal_stmt: Final[int]
+assert_stmt: Final[int]
+compound_stmt: Final[int]
+async_stmt: Final[int]
+if_stmt: Final[int]
+while_stmt: Final[int]
+for_stmt: Final[int]
+try_stmt: Final[int]
+with_stmt: Final[int]
+with_item: Final[int]
+except_clause: Final[int]
+suite: Final[int]
+test: Final[int]
+test_nocond: Final[int]
+lambdef: Final[int]
+lambdef_nocond: Final[int]
+or_test: Final[int]
+and_test: Final[int]
+not_test: Final[int]
+comparison: Final[int]
+comp_op: Final[int]
+star_expr: Final[int]
+expr: Final[int]
+xor_expr: Final[int]
+and_expr: Final[int]
+shift_expr: Final[int]
+arith_expr: Final[int]
+term: Final[int]
+factor: Final[int]
+power: Final[int]
+atom_expr: Final[int]
+atom: Final[int]
+testlist_comp: Final[int]
+trailer: Final[int]
+subscriptlist: Final[int]
+subscript: Final[int]
+sliceop: Final[int]
+exprlist: Final[int]
+testlist: Final[int]
+dictorsetmaker: Final[int]
+classdef: Final[int]
+arglist: Final[int]
+argument: Final[int]
+comp_iter: Final[int]
+comp_for: Final[int]
+comp_if: Final[int]
+encoding_decl: Final[int]
+yield_expr: Final[int]
+yield_arg: Final[int]
+sync_comp_for: Final[int]
+func_body_suite: Final[int]
+func_type: Final[int]
+func_type_input: Final[int]
+namedexpr_test: Final[int]
+typelist: Final[int]
+sym_name: Final[dict[int, str]]
diff --git a/mypy/typeshed/stdlib/symtable.pyi b/mypy/typeshed/stdlib/symtable.pyi
index d5f2be04b600..a727b878688e 100644
--- a/mypy/typeshed/stdlib/symtable.pyi
+++ b/mypy/typeshed/stdlib/symtable.pyi
@@ -49,8 +49,11 @@ class Function(SymbolTable):
     def get_nonlocals(self) -> tuple[str, ...]: ...
 
 class Class(SymbolTable):
-    @deprecated("deprecated in Python 3.14, will be removed in Python 3.16")
-    def get_methods(self) -> tuple[str, ...]: ...
+    if sys.version_info >= (3, 14):
+        @deprecated("Deprecated since Python 3.14; will be removed in Python 3.16.")
+        def get_methods(self) -> tuple[str, ...]: ...
+    else:
+        def get_methods(self) -> tuple[str, ...]: ...
 
 class Symbol:
     def __init__(
diff --git a/mypy/typeshed/stdlib/sys/__init__.pyi b/mypy/typeshed/stdlib/sys/__init__.pyi
index ce06551f975a..7807b0eab01f 100644
--- a/mypy/typeshed/stdlib/sys/__init__.pyi
+++ b/mypy/typeshed/stdlib/sys/__init__.pyi
@@ -6,7 +6,7 @@ from collections.abc import AsyncGenerator, Callable, Sequence
 from io import TextIOWrapper
 from types import FrameType, ModuleType, TracebackType
 from typing import Any, Final, Literal, NoReturn, Protocol, TextIO, TypeVar, final, type_check_only
-from typing_extensions import LiteralString, TypeAlias
+from typing_extensions import LiteralString, TypeAlias, deprecated
 
 _T = TypeVar("_T")
 
@@ -181,6 +181,14 @@ class _flags(_UninstantiableStructseq, tuple[int, ...]):
     if sys.version_info >= (3, 11):
         @property
         def safe_path(self) -> bool: ...
+    if sys.version_info >= (3, 13):
+        @property
+        def gil(self) -> Literal[0, 1]: ...
+    if sys.version_info >= (3, 14):
+        @property
+        def thread_inherit_context(self) -> Literal[0, 1]: ...
+        @property
+        def context_aware_warnings(self) -> Literal[0, 1]: ...
     # Whether or not this exists on lower versions of Python
     # may depend on which patch release you're using
     # (it was backported to all Python versions on 3.8+ as a security fix)
@@ -335,9 +343,20 @@ class _version_info(_UninstantiableStructseq, tuple[int, int, int, _ReleaseLevel
 version_info: _version_info
 
 def call_tracing(func: Callable[..., _T], args: Any, /) -> _T: ...
-def _clear_type_cache() -> None: ...
+
+if sys.version_info >= (3, 13):
+    @deprecated("Deprecated since Python 3.13. Use `_clear_internal_caches()` instead.")
+    def _clear_type_cache() -> None: ...
+
+else:
+    def _clear_type_cache() -> None: ...
+
 def _current_frames() -> dict[int, FrameType]: ...
 def _getframe(depth: int = 0, /) -> FrameType: ...
+
+if sys.version_info >= (3, 12):
+    def _getframemodulename(depth: int = 0) -> str | None: ...
+
 def _debugmallocstats() -> None: ...
 def __displayhook__(object: object, /) -> None: ...
 def __excepthook__(exctype: type[BaseException], value: BaseException, traceback: TracebackType | None, /) -> None: ...
@@ -367,6 +386,7 @@ def settrace(function: TraceFunction | None, /) -> None: ...
 if sys.platform == "win32":
     # A tuple of length 5, even though it has more than 5 attributes.
     @final
+    @type_check_only
     class _WinVersion(_UninstantiableStructseq, tuple[int, int, int, int, str]):
         @property
         def major(self) -> int: ...
@@ -443,7 +463,14 @@ def get_asyncgen_hooks() -> _asyncgen_hooks: ...
 def set_asyncgen_hooks(firstiter: _AsyncgenHook = ..., finalizer: _AsyncgenHook = ...) -> None: ...
 
 if sys.platform == "win32":
-    def _enablelegacywindowsfsencoding() -> None: ...
+    if sys.version_info >= (3, 13):
+        @deprecated(
+            "Deprecated since Python 3.13; will be removed in Python 3.16. "
+            "Use the `PYTHONLEGACYWINDOWSFSENCODING` environment variable instead."
+        )
+        def _enablelegacywindowsfsencoding() -> None: ...
+    else:
+        def _enablelegacywindowsfsencoding() -> None: ...
 
 def get_coroutine_origin_tracking_depth() -> int: ...
 def set_coroutine_origin_tracking_depth(depth: int) -> None: ...
diff --git a/mypy/typeshed/stdlib/sys/_monitoring.pyi b/mypy/typeshed/stdlib/sys/_monitoring.pyi
index 0507eeedc26d..5d231c7a93b3 100644
--- a/mypy/typeshed/stdlib/sys/_monitoring.pyi
+++ b/mypy/typeshed/stdlib/sys/_monitoring.pyi
@@ -5,40 +5,52 @@
 # of being a `types.ModuleType` instance that cannot be directly imported,
 # and exists in the `sys`-module namespace despite `sys` not being a package.
 
+import sys
 from collections.abc import Callable
 from types import CodeType
-from typing import Any
+from typing import Any, Final, type_check_only
+from typing_extensions import deprecated
 
-DEBUGGER_ID: int
-COVERAGE_ID: int
-PROFILER_ID: int
-OPTIMIZER_ID: int
+DEBUGGER_ID: Final = 0
+COVERAGE_ID: Final = 1
+PROFILER_ID: Final = 2
+OPTIMIZER_ID: Final = 5
 
 def use_tool_id(tool_id: int, name: str, /) -> None: ...
 def free_tool_id(tool_id: int, /) -> None: ...
 def get_tool(tool_id: int, /) -> str | None: ...
 
-events: _events
+events: Final[_events]
 
+@type_check_only
 class _events:
-    BRANCH: int
-    CALL: int
-    C_RAISE: int
-    C_RETURN: int
-    EXCEPTION_HANDLED: int
-    INSTRUCTION: int
-    JUMP: int
-    LINE: int
-    NO_EVENTS: int
-    PY_RESUME: int
-    PY_RETURN: int
-    PY_START: int
-    PY_THROW: int
-    PY_UNWIND: int
-    PY_YIELD: int
-    RAISE: int
-    RERAISE: int
-    STOP_ITERATION: int
+    CALL: Final[int]
+    C_RAISE: Final[int]
+    C_RETURN: Final[int]
+    EXCEPTION_HANDLED: Final[int]
+    INSTRUCTION: Final[int]
+    JUMP: Final[int]
+    LINE: Final[int]
+    NO_EVENTS: Final[int]
+    PY_RESUME: Final[int]
+    PY_RETURN: Final[int]
+    PY_START: Final[int]
+    PY_THROW: Final[int]
+    PY_UNWIND: Final[int]
+    PY_YIELD: Final[int]
+    RAISE: Final[int]
+    RERAISE: Final[int]
+    STOP_ITERATION: Final[int]
+    if sys.version_info >= (3, 14):
+        BRANCH_LEFT: Final[int]
+        BRANCH_TAKEN: Final[int]
+
+        @property
+        @deprecated("Deprecated since Python 3.14. Use `BRANCH_LEFT` or `BRANCH_TAKEN` instead.")
+        def BRANCH(self) -> int: ...
+
+    else:
+        BRANCH: Final[int]
 
 def get_events(tool_id: int, /) -> int: ...
 def set_events(tool_id: int, event_set: int, /) -> None: ...
@@ -46,7 +58,7 @@ def get_local_events(tool_id: int, code: CodeType, /) -> int: ...
 def set_local_events(tool_id: int, code: CodeType, event_set: int, /) -> int: ...
 def restart_events() -> None: ...
 
-DISABLE: object
-MISSING: object
+DISABLE: Final[object]
+MISSING: Final[object]
 
 def register_callback(tool_id: int, event: int, func: Callable[..., Any] | None, /) -> Callable[..., Any] | None: ...
diff --git a/mypy/typeshed/stdlib/tarfile.pyi b/mypy/typeshed/stdlib/tarfile.pyi
index 31094f87872d..f6623ea9929d 100644
--- a/mypy/typeshed/stdlib/tarfile.pyi
+++ b/mypy/typeshed/stdlib/tarfile.pyi
@@ -6,9 +6,12 @@ from builtins import list as _list  # aliases to avoid name clashes with fields
 from collections.abc import Callable, Iterable, Iterator, Mapping
 from gzip import _ReadableFileobj as _GzipReadableFileobj, _WritableFileobj as _GzipWritableFileobj
 from types import TracebackType
-from typing import IO, ClassVar, Literal, Protocol, overload
+from typing import IO, ClassVar, Final, Literal, Protocol, overload, type_check_only
 from typing_extensions import Self, TypeAlias, deprecated
 
+if sys.version_info >= (3, 14):
+    from compression.zstd import ZstdDict
+
 __all__ = [
     "TarFile",
     "TarInfo",
@@ -38,10 +41,13 @@ if sys.version_info >= (3, 12):
         "AbsolutePathError",
         "LinkOutsideDestinationError",
     ]
+if sys.version_info >= (3, 13):
+    __all__ += ["LinkFallbackError"]
 
 _FilterFunction: TypeAlias = Callable[[TarInfo, str], TarInfo | None]
 _TarfileFilter: TypeAlias = Literal["fully_trusted", "tar", "data"] | _FilterFunction
 
+@type_check_only
 class _Fileobj(Protocol):
     def read(self, size: int, /) -> bytes: ...
     def write(self, b: bytes, /) -> object: ...
@@ -52,58 +58,61 @@ class _Fileobj(Protocol):
     # name: str | bytes
     # mode: Literal["rb", "r+b", "wb", "xb"]
 
+@type_check_only
 class _Bz2ReadableFileobj(bz2._ReadableFileobj):
     def close(self) -> object: ...
 
+@type_check_only
 class _Bz2WritableFileobj(bz2._WritableFileobj):
     def close(self) -> object: ...
 
 # tar constants
-NUL: bytes
-BLOCKSIZE: int
-RECORDSIZE: int
-GNU_MAGIC: bytes
-POSIX_MAGIC: bytes
-
-LENGTH_NAME: int
-LENGTH_LINK: int
-LENGTH_PREFIX: int
-
-REGTYPE: bytes
-AREGTYPE: bytes
-LNKTYPE: bytes
-SYMTYPE: bytes
-CONTTYPE: bytes
-BLKTYPE: bytes
-DIRTYPE: bytes
-FIFOTYPE: bytes
-CHRTYPE: bytes
-
-GNUTYPE_LONGNAME: bytes
-GNUTYPE_LONGLINK: bytes
-GNUTYPE_SPARSE: bytes
-
-XHDTYPE: bytes
-XGLTYPE: bytes
-SOLARIS_XHDTYPE: bytes
-
-USTAR_FORMAT: int
-GNU_FORMAT: int
-PAX_FORMAT: int
-DEFAULT_FORMAT: int
+NUL: Final = b"\0"
+BLOCKSIZE: Final = 512
+RECORDSIZE: Final = 10240
+GNU_MAGIC: Final = b"ustar  \0"
+POSIX_MAGIC: Final = b"ustar\x0000"
+
+LENGTH_NAME: Final = 100
+LENGTH_LINK: Final = 100
+LENGTH_PREFIX: Final = 155
+
+REGTYPE: Final = b"0"
+AREGTYPE: Final = b"\0"
+LNKTYPE: Final = b"1"
+SYMTYPE: Final = b"2"
+CHRTYPE: Final = b"3"
+BLKTYPE: Final = b"4"
+DIRTYPE: Final = b"5"
+FIFOTYPE: Final = b"6"
+CONTTYPE: Final = b"7"
+
+GNUTYPE_LONGNAME: Final = b"L"
+GNUTYPE_LONGLINK: Final = b"K"
+GNUTYPE_SPARSE: Final = b"S"
+
+XHDTYPE: Final = b"x"
+XGLTYPE: Final = b"g"
+SOLARIS_XHDTYPE: Final = b"X"
+
+_TarFormat: TypeAlias = Literal[0, 1, 2]  # does not exist at runtime
+USTAR_FORMAT: Final = 0
+GNU_FORMAT: Final = 1
+PAX_FORMAT: Final = 2
+DEFAULT_FORMAT: Final = PAX_FORMAT
 
 # tarfile constants
 
-SUPPORTED_TYPES: tuple[bytes, ...]
-REGULAR_TYPES: tuple[bytes, ...]
-GNU_TYPES: tuple[bytes, ...]
-PAX_FIELDS: tuple[str, ...]
-PAX_NUMBER_FIELDS: dict[str, type]
-PAX_NAME_FIELDS: set[str]
+SUPPORTED_TYPES: Final[tuple[bytes, ...]]
+REGULAR_TYPES: Final[tuple[bytes, ...]]
+GNU_TYPES: Final[tuple[bytes, ...]]
+PAX_FIELDS: Final[tuple[str, ...]]
+PAX_NUMBER_FIELDS: Final[dict[str, type]]
+PAX_NAME_FIELDS: Final[set[str]]
 
-ENCODING: str
+ENCODING: Final[str]
 
-class ExFileObject(io.BufferedReader):
+class ExFileObject(io.BufferedReader):  # undocumented
     def __init__(self, tarfile: TarFile, tarinfo: TarInfo) -> None: ...
 
 class TarFile:
@@ -111,13 +120,13 @@ class TarFile:
     name: StrOrBytesPath | None
     mode: Literal["r", "a", "w", "x"]
     fileobj: _Fileobj | None
-    format: int | None
+    format: _TarFormat | None
     tarinfo: type[TarInfo]
     dereference: bool | None
     ignore_zeros: bool | None
     encoding: str | None
     errors: str
-    fileobject: type[ExFileObject]
+    fileobject: type[ExFileObject]  # undocumented
     pax_headers: Mapping[str, str] | None
     debug: int | None
     errorlevel: int | None
@@ -184,6 +193,30 @@ class TarFile:
         debug: int | None = ...,
         errorlevel: int | None = ...,
     ) -> Self: ...
+    if sys.version_info >= (3, 14):
+        @overload
+        @classmethod
+        def open(
+            cls,
+            name: StrOrBytesPath | None,
+            mode: Literal["r:zst"],
+            fileobj: _Fileobj | None = None,
+            bufsize: int = 10240,
+            *,
+            format: int | None = ...,
+            tarinfo: type[TarInfo] | None = ...,
+            dereference: bool | None = ...,
+            ignore_zeros: bool | None = ...,
+            encoding: str | None = ...,
+            errors: str = ...,
+            pax_headers: Mapping[str, str] | None = ...,
+            debug: int | None = ...,
+            errorlevel: int | None = ...,
+            level: None = None,
+            options: Mapping[int, int] | None = None,
+            zstd_dict: ZstdDict | None = None,
+        ) -> Self: ...
+
     @overload
     @classmethod
     def open(
@@ -302,12 +335,56 @@ class TarFile:
         errorlevel: int | None = ...,
         preset: Literal[0, 1, 2, 3, 4, 5, 6, 7, 8, 9] | None = ...,
     ) -> Self: ...
+    if sys.version_info >= (3, 14):
+        @overload
+        @classmethod
+        def open(
+            cls,
+            name: StrOrBytesPath | None,
+            mode: Literal["x:zst", "w:zst"],
+            fileobj: _Fileobj | None = None,
+            bufsize: int = 10240,
+            *,
+            format: int | None = ...,
+            tarinfo: type[TarInfo] | None = ...,
+            dereference: bool | None = ...,
+            ignore_zeros: bool | None = ...,
+            encoding: str | None = ...,
+            errors: str = ...,
+            pax_headers: Mapping[str, str] | None = ...,
+            debug: int | None = ...,
+            errorlevel: int | None = ...,
+            options: Mapping[int, int] | None = None,
+            zstd_dict: ZstdDict | None = None,
+        ) -> Self: ...
+        @overload
+        @classmethod
+        def open(
+            cls,
+            name: StrOrBytesPath | None = None,
+            *,
+            mode: Literal["x:zst", "w:zst"],
+            fileobj: _Fileobj | None = None,
+            bufsize: int = 10240,
+            format: int | None = ...,
+            tarinfo: type[TarInfo] | None = ...,
+            dereference: bool | None = ...,
+            ignore_zeros: bool | None = ...,
+            encoding: str | None = ...,
+            errors: str = ...,
+            pax_headers: Mapping[str, str] | None = ...,
+            debug: int | None = ...,
+            errorlevel: int | None = ...,
+            options: Mapping[int, int] | None = None,
+            zstd_dict: ZstdDict | None = None,
+        ) -> Self: ...
+
     @overload
     @classmethod
     def open(
         cls,
         name: StrOrBytesPath | ReadableBuffer | None,
-        mode: Literal["r|*", "r|", "r|gz", "r|bz2", "r|xz"],
+        mode: Literal["r|*", "r|", "r|gz", "r|bz2", "r|xz", "r|zst"],
         fileobj: _Fileobj | None = None,
         bufsize: int = 10240,
         *,
@@ -327,7 +404,7 @@ class TarFile:
         cls,
         name: StrOrBytesPath | ReadableBuffer | None = None,
         *,
-        mode: Literal["r|*", "r|", "r|gz", "r|bz2", "r|xz"],
+        mode: Literal["r|*", "r|", "r|gz", "r|bz2", "r|xz", "r|zst"],
         fileobj: _Fileobj | None = None,
         bufsize: int = 10240,
         format: int | None = ...,
@@ -345,7 +422,7 @@ class TarFile:
     def open(
         cls,
         name: StrOrBytesPath | WriteableBuffer | None,
-        mode: Literal["w|", "w|xz"],
+        mode: Literal["w|", "w|xz", "w|zst"],
         fileobj: _Fileobj | None = None,
         bufsize: int = 10240,
         *,
@@ -365,7 +442,7 @@ class TarFile:
         cls,
         name: StrOrBytesPath | WriteableBuffer | None = None,
         *,
-        mode: Literal["w|", "w|xz"],
+        mode: Literal["w|", "w|xz", "w|zst"],
         fileobj: _Fileobj | None = None,
         bufsize: int = 10240,
         format: int | None = ...,
@@ -524,10 +601,52 @@ class TarFile:
         debug: int | None = ...,
         errorlevel: int | None = ...,
     ) -> Self: ...
+    if sys.version_info >= (3, 14):
+        @overload
+        @classmethod
+        def zstopen(
+            cls,
+            name: StrOrBytesPath | None,
+            mode: Literal["r"] = "r",
+            fileobj: IO[bytes] | None = None,
+            level: None = None,
+            options: Mapping[int, int] | None = None,
+            zstd_dict: ZstdDict | None = None,
+            *,
+            format: int | None = ...,
+            tarinfo: type[TarInfo] | None = ...,
+            dereference: bool | None = ...,
+            ignore_zeros: bool | None = ...,
+            encoding: str | None = ...,
+            pax_headers: Mapping[str, str] | None = ...,
+            debug: int | None = ...,
+            errorlevel: int | None = ...,
+        ) -> Self: ...
+        @overload
+        @classmethod
+        def zstopen(
+            cls,
+            name: StrOrBytesPath | None,
+            mode: Literal["w", "x"],
+            fileobj: IO[bytes] | None = None,
+            level: int | None = None,
+            options: Mapping[int, int] | None = None,
+            zstd_dict: ZstdDict | None = None,
+            *,
+            format: int | None = ...,
+            tarinfo: type[TarInfo] | None = ...,
+            dereference: bool | None = ...,
+            ignore_zeros: bool | None = ...,
+            encoding: str | None = ...,
+            pax_headers: Mapping[str, str] | None = ...,
+            debug: int | None = ...,
+            errorlevel: int | None = ...,
+        ) -> Self: ...
+
     def getmember(self, name: str) -> TarInfo: ...
     def getmembers(self) -> _list[TarInfo]: ...
     def getnames(self) -> _list[str]: ...
-    def list(self, verbose: bool = True, *, members: _list[TarInfo] | None = None) -> None: ...
+    def list(self, verbose: bool = True, *, members: Iterable[TarInfo] | None = None) -> None: ...
     def next(self) -> TarInfo | None: ...
     # Calling this method without `filter` is deprecated, but it may be set either on the class or in an
     # individual call, so we can't mark it as @deprecated here.
@@ -537,7 +656,7 @@ class TarFile:
         members: Iterable[TarInfo] | None = None,
         *,
         numeric_owner: bool = False,
-        filter: _TarfileFilter | None = ...,
+        filter: _TarfileFilter | None = None,
     ) -> None: ...
     # Same situation as for `extractall`.
     def extract(
@@ -547,10 +666,17 @@ class TarFile:
         set_attrs: bool = True,
         *,
         numeric_owner: bool = False,
-        filter: _TarfileFilter | None = ...,
+        filter: _TarfileFilter | None = None,
     ) -> None: ...
     def _extract_member(
-        self, tarinfo: TarInfo, targetpath: str, set_attrs: bool = True, numeric_owner: bool = False
+        self,
+        tarinfo: TarInfo,
+        targetpath: str,
+        set_attrs: bool = True,
+        numeric_owner: bool = False,
+        *,
+        filter_function: _FilterFunction | None = None,
+        extraction_root: str | None = None,
     ) -> None: ...  # undocumented
     def extractfile(self, member: str | TarInfo) -> IO[bytes] | None: ...
     def makedir(self, tarinfo: TarInfo, targetpath: StrOrBytesPath) -> None: ...  # undocumented
@@ -559,6 +685,9 @@ class TarFile:
     def makefifo(self, tarinfo: TarInfo, targetpath: StrOrBytesPath) -> None: ...  # undocumented
     def makedev(self, tarinfo: TarInfo, targetpath: StrOrBytesPath) -> None: ...  # undocumented
     def makelink(self, tarinfo: TarInfo, targetpath: StrOrBytesPath) -> None: ...  # undocumented
+    def makelink_with_filter(
+        self, tarinfo: TarInfo, targetpath: StrOrBytesPath, filter_function: _FilterFunction, extraction_root: str
+    ) -> None: ...  # undocumented
     def chown(self, tarinfo: TarInfo, targetpath: StrOrBytesPath, numeric_owner: bool) -> None: ...  # undocumented
     def chmod(self, tarinfo: TarInfo, targetpath: StrOrBytesPath) -> None: ...  # undocumented
     def utime(self, tarinfo: TarInfo, targetpath: StrOrBytesPath) -> None: ...  # undocumented
@@ -607,11 +736,36 @@ class AbsoluteLinkError(FilterError):
 class LinkOutsideDestinationError(FilterError):
     def __init__(self, tarinfo: TarInfo, path: str) -> None: ...
 
+class LinkFallbackError(FilterError):
+    def __init__(self, tarinfo: TarInfo, path: str) -> None: ...
+
 def fully_trusted_filter(member: TarInfo, dest_path: str) -> TarInfo: ...
 def tar_filter(member: TarInfo, dest_path: str) -> TarInfo: ...
 def data_filter(member: TarInfo, dest_path: str) -> TarInfo: ...
 
 class TarInfo:
+    __slots__ = (
+        "name",
+        "mode",
+        "uid",
+        "gid",
+        "size",
+        "mtime",
+        "chksum",
+        "type",
+        "linkname",
+        "uname",
+        "gname",
+        "devmajor",
+        "devminor",
+        "offset",
+        "offset_data",
+        "pax_headers",
+        "sparse",
+        "_tarfile",
+        "_sparse_structs",
+        "_link_target",
+    )
     name: str
     path: str
     size: int
@@ -623,7 +777,7 @@ class TarInfo:
     offset_data: int
     sparse: bytes | None
     mode: int
-    type: bytes
+    type: bytes  # usually one of the TYPE constants, but could be an arbitrary byte
     linkname: str
     uid: int
     gid: int
@@ -633,10 +787,10 @@ class TarInfo:
     def __init__(self, name: str = "") -> None: ...
     if sys.version_info >= (3, 13):
         @property
-        @deprecated("Deprecated in Python 3.13; removal scheduled for Python 3.16")
+        @deprecated("Deprecated since Python 3.13; will be removed in Python 3.16.")
         def tarfile(self) -> TarFile | None: ...
         @tarfile.setter
-        @deprecated("Deprecated in Python 3.13; removal scheduled for Python 3.16")
+        @deprecated("Deprecated since Python 3.13; will be removed in Python 3.16.")
         def tarfile(self, tarfile: TarFile | None) -> None: ...
     else:
         tarfile: TarFile | None
@@ -663,7 +817,7 @@ class TarInfo:
         deep: bool = True,
     ) -> Self: ...
     def get_info(self) -> Mapping[str, str | int | bytes | Mapping[str, str]]: ...
-    def tobuf(self, format: int | None = 2, encoding: str | None = "utf-8", errors: str = "surrogateescape") -> bytes: ...
+    def tobuf(self, format: _TarFormat | None = 2, encoding: str | None = "utf-8", errors: str = "surrogateescape") -> bytes: ...
     def create_ustar_header(
         self, info: Mapping[str, str | int | bytes | Mapping[str, str]], encoding: str, errors: str
     ) -> bytes: ...
diff --git a/mypy/typeshed/stdlib/telnetlib.pyi b/mypy/typeshed/stdlib/telnetlib.pyi
index 6b599256d17b..88aa43d24899 100644
--- a/mypy/typeshed/stdlib/telnetlib.pyi
+++ b/mypy/typeshed/stdlib/telnetlib.pyi
@@ -2,89 +2,89 @@ import socket
 from collections.abc import Callable, MutableSequence, Sequence
 from re import Match, Pattern
 from types import TracebackType
-from typing import Any
+from typing import Any, Final
 from typing_extensions import Self
 
 __all__ = ["Telnet"]
 
-DEBUGLEVEL: int
-TELNET_PORT: int
+DEBUGLEVEL: Final = 0
+TELNET_PORT: Final = 23
 
-IAC: bytes
-DONT: bytes
-DO: bytes
-WONT: bytes
-WILL: bytes
-theNULL: bytes
+IAC: Final = b"\xff"
+DONT: Final = b"\xfe"
+DO: Final = b"\xfd"
+WONT: Final = b"\xfc"
+WILL: Final = b"\xfb"
+theNULL: Final = b"\x00"
 
-SE: bytes
-NOP: bytes
-DM: bytes
-BRK: bytes
-IP: bytes
-AO: bytes
-AYT: bytes
-EC: bytes
-EL: bytes
-GA: bytes
-SB: bytes
+SE: Final = b"\xf0"
+NOP: Final = b"\xf1"
+DM: Final = b"\xf2"
+BRK: Final = b"\xf3"
+IP: Final = b"\xf4"
+AO: Final = b"\xf5"
+AYT: Final = b"\xf6"
+EC: Final = b"\xf7"
+EL: Final = b"\xf8"
+GA: Final = b"\xf9"
+SB: Final = b"\xfa"
 
-BINARY: bytes
-ECHO: bytes
-RCP: bytes
-SGA: bytes
-NAMS: bytes
-STATUS: bytes
-TM: bytes
-RCTE: bytes
-NAOL: bytes
-NAOP: bytes
-NAOCRD: bytes
-NAOHTS: bytes
-NAOHTD: bytes
-NAOFFD: bytes
-NAOVTS: bytes
-NAOVTD: bytes
-NAOLFD: bytes
-XASCII: bytes
-LOGOUT: bytes
-BM: bytes
-DET: bytes
-SUPDUP: bytes
-SUPDUPOUTPUT: bytes
-SNDLOC: bytes
-TTYPE: bytes
-EOR: bytes
-TUID: bytes
-OUTMRK: bytes
-TTYLOC: bytes
-VT3270REGIME: bytes
-X3PAD: bytes
-NAWS: bytes
-TSPEED: bytes
-LFLOW: bytes
-LINEMODE: bytes
-XDISPLOC: bytes
-OLD_ENVIRON: bytes
-AUTHENTICATION: bytes
-ENCRYPT: bytes
-NEW_ENVIRON: bytes
+BINARY: Final = b"\x00"
+ECHO: Final = b"\x01"
+RCP: Final = b"\x02"
+SGA: Final = b"\x03"
+NAMS: Final = b"\x04"
+STATUS: Final = b"\x05"
+TM: Final = b"\x06"
+RCTE: Final = b"\x07"
+NAOL: Final = b"\x08"
+NAOP: Final = b"\t"
+NAOCRD: Final = b"\n"
+NAOHTS: Final = b"\x0b"
+NAOHTD: Final = b"\x0c"
+NAOFFD: Final = b"\r"
+NAOVTS: Final = b"\x0e"
+NAOVTD: Final = b"\x0f"
+NAOLFD: Final = b"\x10"
+XASCII: Final = b"\x11"
+LOGOUT: Final = b"\x12"
+BM: Final = b"\x13"
+DET: Final = b"\x14"
+SUPDUP: Final = b"\x15"
+SUPDUPOUTPUT: Final = b"\x16"
+SNDLOC: Final = b"\x17"
+TTYPE: Final = b"\x18"
+EOR: Final = b"\x19"
+TUID: Final = b"\x1a"
+OUTMRK: Final = b"\x1b"
+TTYLOC: Final = b"\x1c"
+VT3270REGIME: Final = b"\x1d"
+X3PAD: Final = b"\x1e"
+NAWS: Final = b"\x1f"
+TSPEED: Final = b" "
+LFLOW: Final = b"!"
+LINEMODE: Final = b'"'
+XDISPLOC: Final = b"#"
+OLD_ENVIRON: Final = b"$"
+AUTHENTICATION: Final = b"%"
+ENCRYPT: Final = b"&"
+NEW_ENVIRON: Final = b"'"
 
-TN3270E: bytes
-XAUTH: bytes
-CHARSET: bytes
-RSP: bytes
-COM_PORT_OPTION: bytes
-SUPPRESS_LOCAL_ECHO: bytes
-TLS: bytes
-KERMIT: bytes
-SEND_URL: bytes
-FORWARD_X: bytes
-PRAGMA_LOGON: bytes
-SSPI_LOGON: bytes
-PRAGMA_HEARTBEAT: bytes
-EXOPL: bytes
-NOOPT: bytes
+TN3270E: Final = b"("
+XAUTH: Final = b")"
+CHARSET: Final = b"*"
+RSP: Final = b"+"
+COM_PORT_OPTION: Final = b","
+SUPPRESS_LOCAL_ECHO: Final = b"-"
+TLS: Final = b"."
+KERMIT: Final = b"/"
+SEND_URL: Final = b"0"
+FORWARD_X: Final = b"1"
+PRAGMA_LOGON: Final = b"\x8a"
+SSPI_LOGON: Final = b"\x8b"
+PRAGMA_HEARTBEAT: Final = b"\x8c"
+EXOPL: Final = b"\xff"
+NOOPT: Final = b"\x00"
 
 class Telnet:
     host: str | None  # undocumented
diff --git a/mypy/typeshed/stdlib/tempfile.pyi b/mypy/typeshed/stdlib/tempfile.pyi
index ea6e057e410d..26491074ff71 100644
--- a/mypy/typeshed/stdlib/tempfile.pyi
+++ b/mypy/typeshed/stdlib/tempfile.pyi
@@ -14,8 +14,8 @@ from _typeshed import (
 )
 from collections.abc import Iterable, Iterator
 from types import GenericAlias, TracebackType
-from typing import IO, Any, AnyStr, Generic, Literal, overload
-from typing_extensions import Self
+from typing import IO, Any, AnyStr, Final, Generic, Literal, overload
+from typing_extensions import Self, deprecated
 
 __all__ = [
     "NamedTemporaryFile",
@@ -34,7 +34,7 @@ __all__ = [
 ]
 
 # global variables
-TMP_MAX: int
+TMP_MAX: Final[int]
 tempdir: str | None
 template: str
 
@@ -471,6 +471,7 @@ def mkstemp(
 def mkdtemp(suffix: str | None = None, prefix: str | None = None, dir: StrPath | None = None) -> str: ...
 @overload
 def mkdtemp(suffix: bytes | None = None, prefix: bytes | None = None, dir: BytesPath | None = None) -> bytes: ...
+@deprecated("Deprecated since Python 2.3. Use `mkstemp()` or `NamedTemporaryFile(delete=False)` instead.")
 def mktemp(suffix: str = "", prefix: str = "tmp", dir: StrPath | None = None) -> str: ...
 def gettempdirb() -> bytes: ...
 def gettempprefixb() -> bytes: ...
diff --git a/mypy/typeshed/stdlib/termios.pyi b/mypy/typeshed/stdlib/termios.pyi
index 5a5a1f53be3c..a35be5dfe740 100644
--- a/mypy/typeshed/stdlib/termios.pyi
+++ b/mypy/typeshed/stdlib/termios.pyi
@@ -1,6 +1,6 @@
 import sys
 from _typeshed import FileDescriptorLike
-from typing import Any
+from typing import Any, Final
 from typing_extensions import TypeAlias
 
 # Must be a list of length 7, containing 6 ints and a list of NCCS 1-character bytes or ints.
@@ -9,286 +9,287 @@ _Attr: TypeAlias = list[int | list[bytes | int]] | list[int | list[bytes]] | lis
 _AttrReturn: TypeAlias = list[Any]
 
 if sys.platform != "win32":
-    B0: int
-    B110: int
-    B115200: int
-    B1200: int
-    B134: int
-    B150: int
-    B1800: int
-    B19200: int
-    B200: int
-    B230400: int
-    B2400: int
-    B300: int
-    B38400: int
-    B4800: int
-    B50: int
-    B57600: int
-    B600: int
-    B75: int
-    B9600: int
-    BRKINT: int
-    BS0: int
-    BS1: int
-    BSDLY: int
-    CDSUSP: int
-    CEOF: int
-    CEOL: int
-    CEOT: int
-    CERASE: int
-    CFLUSH: int
-    CINTR: int
-    CKILL: int
-    CLNEXT: int
-    CLOCAL: int
-    CQUIT: int
-    CR0: int
-    CR1: int
-    CR2: int
-    CR3: int
-    CRDLY: int
-    CREAD: int
-    CRPRNT: int
-    CRTSCTS: int
-    CS5: int
-    CS6: int
-    CS7: int
-    CS8: int
-    CSIZE: int
-    CSTART: int
-    CSTOP: int
-    CSTOPB: int
-    CSUSP: int
-    CWERASE: int
-    ECHO: int
-    ECHOCTL: int
-    ECHOE: int
-    ECHOK: int
-    ECHOKE: int
-    ECHONL: int
-    ECHOPRT: int
-    EXTA: int
-    EXTB: int
-    FF0: int
-    FF1: int
-    FFDLY: int
-    FIOASYNC: int
-    FIOCLEX: int
-    FIONBIO: int
-    FIONCLEX: int
-    FIONREAD: int
-    FLUSHO: int
-    HUPCL: int
-    ICANON: int
-    ICRNL: int
-    IEXTEN: int
-    IGNBRK: int
-    IGNCR: int
-    IGNPAR: int
-    IMAXBEL: int
-    INLCR: int
-    INPCK: int
-    ISIG: int
-    ISTRIP: int
-    IXANY: int
-    IXOFF: int
-    IXON: int
-    NCCS: int
-    NL0: int
-    NL1: int
-    NLDLY: int
-    NOFLSH: int
-    OCRNL: int
-    OFDEL: int
-    OFILL: int
-    ONLCR: int
-    ONLRET: int
-    ONOCR: int
-    OPOST: int
-    PARENB: int
-    PARMRK: int
-    PARODD: int
-    PENDIN: int
-    TAB0: int
-    TAB1: int
-    TAB2: int
-    TAB3: int
-    TABDLY: int
-    TCIFLUSH: int
-    TCIOFF: int
-    TCIOFLUSH: int
-    TCION: int
-    TCOFLUSH: int
-    TCOOFF: int
-    TCOON: int
-    TCSADRAIN: int
-    TCSAFLUSH: int
-    TCSANOW: int
-    TIOCCONS: int
-    TIOCEXCL: int
-    TIOCGETD: int
-    TIOCGPGRP: int
-    TIOCGWINSZ: int
-    TIOCM_CAR: int
-    TIOCM_CD: int
-    TIOCM_CTS: int
-    TIOCM_DSR: int
-    TIOCM_DTR: int
-    TIOCM_LE: int
-    TIOCM_RI: int
-    TIOCM_RNG: int
-    TIOCM_RTS: int
-    TIOCM_SR: int
-    TIOCM_ST: int
-    TIOCMBIC: int
-    TIOCMBIS: int
-    TIOCMGET: int
-    TIOCMSET: int
-    TIOCNOTTY: int
-    TIOCNXCL: int
-    TIOCOUTQ: int
-    TIOCPKT_DATA: int
-    TIOCPKT_DOSTOP: int
-    TIOCPKT_FLUSHREAD: int
-    TIOCPKT_FLUSHWRITE: int
-    TIOCPKT_NOSTOP: int
-    TIOCPKT_START: int
-    TIOCPKT_STOP: int
-    TIOCPKT: int
-    TIOCSCTTY: int
-    TIOCSETD: int
-    TIOCSPGRP: int
-    TIOCSTI: int
-    TIOCSWINSZ: int
-    TOSTOP: int
-    VDISCARD: int
-    VEOF: int
-    VEOL: int
-    VEOL2: int
-    VERASE: int
-    VINTR: int
-    VKILL: int
-    VLNEXT: int
-    VMIN: int
-    VQUIT: int
-    VREPRINT: int
-    VSTART: int
-    VSTOP: int
-    VSUSP: int
-    VT0: int
-    VT1: int
-    VTDLY: int
-    VTIME: int
-    VWERASE: int
+    # Values depends on the platform
+    B0: Final[int]
+    B110: Final[int]
+    B115200: Final[int]
+    B1200: Final[int]
+    B134: Final[int]
+    B150: Final[int]
+    B1800: Final[int]
+    B19200: Final[int]
+    B200: Final[int]
+    B230400: Final[int]
+    B2400: Final[int]
+    B300: Final[int]
+    B38400: Final[int]
+    B4800: Final[int]
+    B50: Final[int]
+    B57600: Final[int]
+    B600: Final[int]
+    B75: Final[int]
+    B9600: Final[int]
+    BRKINT: Final[int]
+    BS0: Final[int]
+    BS1: Final[int]
+    BSDLY: Final[int]
+    CDSUSP: Final[int]
+    CEOF: Final[int]
+    CEOL: Final[int]
+    CEOT: Final[int]
+    CERASE: Final[int]
+    CFLUSH: Final[int]
+    CINTR: Final[int]
+    CKILL: Final[int]
+    CLNEXT: Final[int]
+    CLOCAL: Final[int]
+    CQUIT: Final[int]
+    CR0: Final[int]
+    CR1: Final[int]
+    CR2: Final[int]
+    CR3: Final[int]
+    CRDLY: Final[int]
+    CREAD: Final[int]
+    CRPRNT: Final[int]
+    CRTSCTS: Final[int]
+    CS5: Final[int]
+    CS6: Final[int]
+    CS7: Final[int]
+    CS8: Final[int]
+    CSIZE: Final[int]
+    CSTART: Final[int]
+    CSTOP: Final[int]
+    CSTOPB: Final[int]
+    CSUSP: Final[int]
+    CWERASE: Final[int]
+    ECHO: Final[int]
+    ECHOCTL: Final[int]
+    ECHOE: Final[int]
+    ECHOK: Final[int]
+    ECHOKE: Final[int]
+    ECHONL: Final[int]
+    ECHOPRT: Final[int]
+    EXTA: Final[int]
+    EXTB: Final[int]
+    FF0: Final[int]
+    FF1: Final[int]
+    FFDLY: Final[int]
+    FIOASYNC: Final[int]
+    FIOCLEX: Final[int]
+    FIONBIO: Final[int]
+    FIONCLEX: Final[int]
+    FIONREAD: Final[int]
+    FLUSHO: Final[int]
+    HUPCL: Final[int]
+    ICANON: Final[int]
+    ICRNL: Final[int]
+    IEXTEN: Final[int]
+    IGNBRK: Final[int]
+    IGNCR: Final[int]
+    IGNPAR: Final[int]
+    IMAXBEL: Final[int]
+    INLCR: Final[int]
+    INPCK: Final[int]
+    ISIG: Final[int]
+    ISTRIP: Final[int]
+    IXANY: Final[int]
+    IXOFF: Final[int]
+    IXON: Final[int]
+    NCCS: Final[int]
+    NL0: Final[int]
+    NL1: Final[int]
+    NLDLY: Final[int]
+    NOFLSH: Final[int]
+    OCRNL: Final[int]
+    OFDEL: Final[int]
+    OFILL: Final[int]
+    ONLCR: Final[int]
+    ONLRET: Final[int]
+    ONOCR: Final[int]
+    OPOST: Final[int]
+    PARENB: Final[int]
+    PARMRK: Final[int]
+    PARODD: Final[int]
+    PENDIN: Final[int]
+    TAB0: Final[int]
+    TAB1: Final[int]
+    TAB2: Final[int]
+    TAB3: Final[int]
+    TABDLY: Final[int]
+    TCIFLUSH: Final[int]
+    TCIOFF: Final[int]
+    TCIOFLUSH: Final[int]
+    TCION: Final[int]
+    TCOFLUSH: Final[int]
+    TCOOFF: Final[int]
+    TCOON: Final[int]
+    TCSADRAIN: Final[int]
+    TCSAFLUSH: Final[int]
+    TCSANOW: Final[int]
+    TIOCCONS: Final[int]
+    TIOCEXCL: Final[int]
+    TIOCGETD: Final[int]
+    TIOCGPGRP: Final[int]
+    TIOCGWINSZ: Final[int]
+    TIOCM_CAR: Final[int]
+    TIOCM_CD: Final[int]
+    TIOCM_CTS: Final[int]
+    TIOCM_DSR: Final[int]
+    TIOCM_DTR: Final[int]
+    TIOCM_LE: Final[int]
+    TIOCM_RI: Final[int]
+    TIOCM_RNG: Final[int]
+    TIOCM_RTS: Final[int]
+    TIOCM_SR: Final[int]
+    TIOCM_ST: Final[int]
+    TIOCMBIC: Final[int]
+    TIOCMBIS: Final[int]
+    TIOCMGET: Final[int]
+    TIOCMSET: Final[int]
+    TIOCNOTTY: Final[int]
+    TIOCNXCL: Final[int]
+    TIOCOUTQ: Final[int]
+    TIOCPKT_DATA: Final[int]
+    TIOCPKT_DOSTOP: Final[int]
+    TIOCPKT_FLUSHREAD: Final[int]
+    TIOCPKT_FLUSHWRITE: Final[int]
+    TIOCPKT_NOSTOP: Final[int]
+    TIOCPKT_START: Final[int]
+    TIOCPKT_STOP: Final[int]
+    TIOCPKT: Final[int]
+    TIOCSCTTY: Final[int]
+    TIOCSETD: Final[int]
+    TIOCSPGRP: Final[int]
+    TIOCSTI: Final[int]
+    TIOCSWINSZ: Final[int]
+    TOSTOP: Final[int]
+    VDISCARD: Final[int]
+    VEOF: Final[int]
+    VEOL: Final[int]
+    VEOL2: Final[int]
+    VERASE: Final[int]
+    VINTR: Final[int]
+    VKILL: Final[int]
+    VLNEXT: Final[int]
+    VMIN: Final[int]
+    VQUIT: Final[int]
+    VREPRINT: Final[int]
+    VSTART: Final[int]
+    VSTOP: Final[int]
+    VSUSP: Final[int]
+    VT0: Final[int]
+    VT1: Final[int]
+    VTDLY: Final[int]
+    VTIME: Final[int]
+    VWERASE: Final[int]
 
     if sys.version_info >= (3, 13):
-        EXTPROC: int
-        IUTF8: int
+        EXTPROC: Final[int]
+        IUTF8: Final[int]
 
     if sys.platform == "darwin" and sys.version_info >= (3, 13):
-        ALTWERASE: int
-        B14400: int
-        B28800: int
-        B7200: int
-        B76800: int
-        CCAR_OFLOW: int
-        CCTS_OFLOW: int
-        CDSR_OFLOW: int
-        CDTR_IFLOW: int
-        CIGNORE: int
-        CRTS_IFLOW: int
-        MDMBUF: int
-        NL2: int
-        NL3: int
-        NOKERNINFO: int
-        ONOEOT: int
-        OXTABS: int
-        VDSUSP: int
-        VSTATUS: int
+        ALTWERASE: Final[int]
+        B14400: Final[int]
+        B28800: Final[int]
+        B7200: Final[int]
+        B76800: Final[int]
+        CCAR_OFLOW: Final[int]
+        CCTS_OFLOW: Final[int]
+        CDSR_OFLOW: Final[int]
+        CDTR_IFLOW: Final[int]
+        CIGNORE: Final[int]
+        CRTS_IFLOW: Final[int]
+        MDMBUF: Final[int]
+        NL2: Final[int]
+        NL3: Final[int]
+        NOKERNINFO: Final[int]
+        ONOEOT: Final[int]
+        OXTABS: Final[int]
+        VDSUSP: Final[int]
+        VSTATUS: Final[int]
 
     if sys.platform == "darwin" and sys.version_info >= (3, 11):
-        TIOCGSIZE: int
-        TIOCSSIZE: int
+        TIOCGSIZE: Final[int]
+        TIOCSSIZE: Final[int]
 
     if sys.platform == "linux":
-        B1152000: int
-        B576000: int
-        CBAUD: int
-        CBAUDEX: int
-        CIBAUD: int
-        IOCSIZE_MASK: int
-        IOCSIZE_SHIFT: int
-        IUCLC: int
-        N_MOUSE: int
-        N_PPP: int
-        N_SLIP: int
-        N_STRIP: int
-        N_TTY: int
-        NCC: int
-        OLCUC: int
-        TCFLSH: int
-        TCGETA: int
-        TCGETS: int
-        TCSBRK: int
-        TCSBRKP: int
-        TCSETA: int
-        TCSETAF: int
-        TCSETAW: int
-        TCSETS: int
-        TCSETSF: int
-        TCSETSW: int
-        TCXONC: int
-        TIOCGICOUNT: int
-        TIOCGLCKTRMIOS: int
-        TIOCGSERIAL: int
-        TIOCGSOFTCAR: int
-        TIOCINQ: int
-        TIOCLINUX: int
-        TIOCMIWAIT: int
-        TIOCTTYGSTRUCT: int
-        TIOCSER_TEMT: int
-        TIOCSERCONFIG: int
-        TIOCSERGETLSR: int
-        TIOCSERGETMULTI: int
-        TIOCSERGSTRUCT: int
-        TIOCSERGWILD: int
-        TIOCSERSETMULTI: int
-        TIOCSERSWILD: int
-        TIOCSLCKTRMIOS: int
-        TIOCSSERIAL: int
-        TIOCSSOFTCAR: int
-        VSWTC: int
-        VSWTCH: int
-        XCASE: int
-        XTABS: int
+        B1152000: Final[int]
+        B576000: Final[int]
+        CBAUD: Final[int]
+        CBAUDEX: Final[int]
+        CIBAUD: Final[int]
+        IOCSIZE_MASK: Final[int]
+        IOCSIZE_SHIFT: Final[int]
+        IUCLC: Final[int]
+        N_MOUSE: Final[int]
+        N_PPP: Final[int]
+        N_SLIP: Final[int]
+        N_STRIP: Final[int]
+        N_TTY: Final[int]
+        NCC: Final[int]
+        OLCUC: Final[int]
+        TCFLSH: Final[int]
+        TCGETA: Final[int]
+        TCGETS: Final[int]
+        TCSBRK: Final[int]
+        TCSBRKP: Final[int]
+        TCSETA: Final[int]
+        TCSETAF: Final[int]
+        TCSETAW: Final[int]
+        TCSETS: Final[int]
+        TCSETSF: Final[int]
+        TCSETSW: Final[int]
+        TCXONC: Final[int]
+        TIOCGICOUNT: Final[int]
+        TIOCGLCKTRMIOS: Final[int]
+        TIOCGSERIAL: Final[int]
+        TIOCGSOFTCAR: Final[int]
+        TIOCINQ: Final[int]
+        TIOCLINUX: Final[int]
+        TIOCMIWAIT: Final[int]
+        TIOCTTYGSTRUCT: Final[int]
+        TIOCSER_TEMT: Final[int]
+        TIOCSERCONFIG: Final[int]
+        TIOCSERGETLSR: Final[int]
+        TIOCSERGETMULTI: Final[int]
+        TIOCSERGSTRUCT: Final[int]
+        TIOCSERGWILD: Final[int]
+        TIOCSERSETMULTI: Final[int]
+        TIOCSERSWILD: Final[int]
+        TIOCSLCKTRMIOS: Final[int]
+        TIOCSSERIAL: Final[int]
+        TIOCSSOFTCAR: Final[int]
+        VSWTC: Final[int]
+        VSWTCH: Final[int]
+        XCASE: Final[int]
+        XTABS: Final[int]
 
     if sys.platform != "darwin":
-        B1000000: int
-        B1500000: int
-        B2000000: int
-        B2500000: int
-        B3000000: int
-        B3500000: int
-        B4000000: int
-        B460800: int
-        B500000: int
-        B921600: int
+        B1000000: Final[int]
+        B1500000: Final[int]
+        B2000000: Final[int]
+        B2500000: Final[int]
+        B3000000: Final[int]
+        B3500000: Final[int]
+        B4000000: Final[int]
+        B460800: Final[int]
+        B500000: Final[int]
+        B921600: Final[int]
 
     if sys.platform != "linux":
-        TCSASOFT: int
+        TCSASOFT: Final[int]
 
     if sys.platform != "darwin" and sys.platform != "linux":
         # not available on FreeBSD either.
-        CDEL: int
-        CEOL2: int
-        CESC: int
-        CNUL: int
-        COMMON: int
-        CSWTCH: int
-        IBSHIFT: int
-        INIT_C_CC: int
-        NSWTCH: int
+        CDEL: Final[int]
+        CEOL2: Final[int]
+        CESC: Final[int]
+        CNUL: Final[int]
+        COMMON: Final[int]
+        CSWTCH: Final[int]
+        IBSHIFT: Final[int]
+        INIT_C_CC: Final[int]
+        NSWTCH: Final[int]
 
     def tcgetattr(fd: FileDescriptorLike, /) -> _AttrReturn: ...
     def tcsetattr(fd: FileDescriptorLike, when: int, attributes: _Attr, /) -> None: ...
diff --git a/mypy/typeshed/stdlib/threading.pyi b/mypy/typeshed/stdlib/threading.pyi
index d31351754d05..28fa5267a997 100644
--- a/mypy/typeshed/stdlib/threading.pyi
+++ b/mypy/typeshed/stdlib/threading.pyi
@@ -5,7 +5,7 @@ from _typeshed import ProfileFunction, TraceFunction
 from collections.abc import Callable, Iterable, Mapping
 from contextvars import ContextVar
 from types import TracebackType
-from typing import Any, TypeVar, final
+from typing import Any, Final, TypeVar, final
 from typing_extensions import deprecated
 
 _T = TypeVar("_T")
@@ -46,10 +46,10 @@ if sys.version_info >= (3, 12):
 _profile_hook: ProfileFunction | None
 
 def active_count() -> int: ...
-@deprecated("Use active_count() instead")
+@deprecated("Deprecated since Python 3.10. Use `active_count()` instead.")
 def activeCount() -> int: ...
 def current_thread() -> Thread: ...
-@deprecated("Use current_thread() instead")
+@deprecated("Deprecated since Python 3.10. Use `current_thread()` instead.")
 def currentThread() -> Thread: ...
 def get_ident() -> int: ...
 def enumerate() -> list[Thread]: ...
@@ -67,7 +67,7 @@ if sys.version_info >= (3, 10):
 
 def stack_size(size: int = 0, /) -> int: ...
 
-TIMEOUT_MAX: float
+TIMEOUT_MAX: Final[float]
 
 ThreadError = _thread.error
 local = _thread._local
@@ -107,13 +107,13 @@ class Thread:
     @property
     def native_id(self) -> int | None: ...  # only available on some platforms
     def is_alive(self) -> bool: ...
-    @deprecated("Get the daemon attribute instead")
+    @deprecated("Deprecated since Python 3.10. Read the `daemon` attribute instead.")
     def isDaemon(self) -> bool: ...
-    @deprecated("Set the daemon attribute instead")
+    @deprecated("Deprecated since Python 3.10. Set the `daemon` attribute instead.")
     def setDaemon(self, daemonic: bool) -> None: ...
-    @deprecated("Use the name attribute instead")
+    @deprecated("Deprecated since Python 3.10. Read the `name` attribute instead.")
     def getName(self) -> str: ...
-    @deprecated("Use the name attribute instead")
+    @deprecated("Deprecated since Python 3.10. Set the `name` attribute instead.")
     def setName(self, name: str) -> None: ...
 
 class _DummyThread(Thread):
@@ -142,13 +142,13 @@ class Condition:
     def __exit__(
         self, exc_type: type[BaseException] | None, exc_val: BaseException | None, exc_tb: TracebackType | None
     ) -> None: ...
-    def acquire(self, blocking: bool = ..., timeout: float = ...) -> bool: ...
+    def acquire(self, blocking: bool = True, timeout: float = -1) -> bool: ...
     def release(self) -> None: ...
     def wait(self, timeout: float | None = None) -> bool: ...
     def wait_for(self, predicate: Callable[[], _T], timeout: float | None = None) -> _T: ...
     def notify(self, n: int = 1) -> None: ...
     def notify_all(self) -> None: ...
-    @deprecated("Use notify_all() instead")
+    @deprecated("Deprecated since Python 3.10. Use `notify_all()` instead.")
     def notifyAll(self) -> None: ...
 
 class Semaphore:
@@ -163,7 +163,7 @@ class BoundedSemaphore(Semaphore): ...
 
 class Event:
     def is_set(self) -> bool: ...
-    @deprecated("Use is_set() instead")
+    @deprecated("Deprecated since Python 3.10. Use `is_set()` instead.")
     def isSet(self) -> bool: ...
     def set(self) -> None: ...
     def clear(self) -> None: ...
diff --git a/mypy/typeshed/stdlib/time.pyi b/mypy/typeshed/stdlib/time.pyi
index 6d2538ea7e3e..5665efbba69d 100644
--- a/mypy/typeshed/stdlib/time.pyi
+++ b/mypy/typeshed/stdlib/time.pyi
@@ -1,6 +1,6 @@
 import sys
 from _typeshed import structseq
-from typing import Any, Final, Literal, Protocol, final
+from typing import Any, Final, Literal, Protocol, final, type_check_only
 from typing_extensions import TypeAlias
 
 _TimeTuple: TypeAlias = tuple[int, int, int, int, int, int, int, int, int]
@@ -11,28 +11,28 @@ timezone: int
 tzname: tuple[str, str]
 
 if sys.platform == "linux":
-    CLOCK_BOOTTIME: int
+    CLOCK_BOOTTIME: Final[int]
 if sys.platform != "linux" and sys.platform != "win32" and sys.platform != "darwin":
-    CLOCK_PROF: int  # FreeBSD, NetBSD, OpenBSD
-    CLOCK_UPTIME: int  # FreeBSD, OpenBSD
+    CLOCK_PROF: Final[int]  # FreeBSD, NetBSD, OpenBSD
+    CLOCK_UPTIME: Final[int]  # FreeBSD, OpenBSD
 
 if sys.platform != "win32":
-    CLOCK_MONOTONIC: int
-    CLOCK_MONOTONIC_RAW: int
-    CLOCK_PROCESS_CPUTIME_ID: int
-    CLOCK_REALTIME: int
-    CLOCK_THREAD_CPUTIME_ID: int
+    CLOCK_MONOTONIC: Final[int]
+    CLOCK_MONOTONIC_RAW: Final[int]
+    CLOCK_PROCESS_CPUTIME_ID: Final[int]
+    CLOCK_REALTIME: Final[int]
+    CLOCK_THREAD_CPUTIME_ID: Final[int]
     if sys.platform != "linux" and sys.platform != "darwin":
-        CLOCK_HIGHRES: int  # Solaris only
+        CLOCK_HIGHRES: Final[int]  # Solaris only
 
 if sys.platform == "darwin":
-    CLOCK_UPTIME_RAW: int
+    CLOCK_UPTIME_RAW: Final[int]
     if sys.version_info >= (3, 13):
-        CLOCK_UPTIME_RAW_APPROX: int
-        CLOCK_MONOTONIC_RAW_APPROX: int
+        CLOCK_UPTIME_RAW_APPROX: Final[int]
+        CLOCK_MONOTONIC_RAW_APPROX: Final[int]
 
 if sys.platform == "linux":
-    CLOCK_TAI: int
+    CLOCK_TAI: Final[int]
 
 # Constructor takes an iterable of any type, of length between 9 and 11 elements.
 # However, it always *behaves* like a tuple of 9 elements,
@@ -80,6 +80,7 @@ def time() -> float: ...
 if sys.platform != "win32":
     def tzset() -> None: ...  # Unix only
 
+@type_check_only
 class _ClockInfo(Protocol):
     adjustable: bool
     implementation: str
diff --git a/mypy/typeshed/stdlib/tkinter/__init__.pyi b/mypy/typeshed/stdlib/tkinter/__init__.pyi
index 2a4657f86ce1..54dd70baf199 100644
--- a/mypy/typeshed/stdlib/tkinter/__init__.pyi
+++ b/mypy/typeshed/stdlib/tkinter/__init__.pyi
@@ -4,9 +4,9 @@ from _typeshed import Incomplete, MaybeNone, StrOrBytesPath
 from collections.abc import Callable, Iterable, Mapping, Sequence
 from tkinter.constants import *
 from tkinter.font import _FontDescription
-from types import TracebackType
-from typing import Any, ClassVar, Generic, Literal, NamedTuple, Protocol, TypedDict, TypeVar, overload, type_check_only
-from typing_extensions import TypeAlias, TypeVarTuple, Unpack, deprecated
+from types import GenericAlias, TracebackType
+from typing import Any, ClassVar, Final, Generic, Literal, NamedTuple, Protocol, TypedDict, TypeVar, overload, type_check_only
+from typing_extensions import TypeAlias, TypeVarTuple, Unpack, deprecated, disjoint_base
 
 if sys.version_info >= (3, 11):
     from enum import StrEnum
@@ -153,11 +153,11 @@ __all__ = [
 
 TclError = _tkinter.TclError
 wantobjects: int
-TkVersion: float
-TclVersion: float
-READABLE = _tkinter.READABLE
-WRITABLE = _tkinter.WRITABLE
-EXCEPTION = _tkinter.EXCEPTION
+TkVersion: Final[float]
+TclVersion: Final[float]
+READABLE: Final = _tkinter.READABLE
+WRITABLE: Final = _tkinter.WRITABLE
+EXCEPTION: Final = _tkinter.EXCEPTION
 
 # Quick guide for figuring out which widget class to choose:
 #   - Misc: any widget (don't use BaseWidget because Tk doesn't inherit from BaseWidget)
@@ -198,7 +198,11 @@ if sys.version_info >= (3, 11):
         releaselevel: str
         serial: int
 
-    class _VersionInfoType(_VersionInfoTypeBase): ...
+    if sys.version_info >= (3, 12):
+        class _VersionInfoType(_VersionInfoTypeBase): ...
+    else:
+        @disjoint_base
+        class _VersionInfoType(_VersionInfoTypeBase): ...
 
 if sys.version_info >= (3, 11):
     class EventType(StrEnum):
@@ -308,6 +312,8 @@ class Event(Generic[_W_co]):
     type: EventType
     widget: _W_co
     delta: int
+    if sys.version_info >= (3, 14):
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 def NoDefaultRoot() -> None: ...
 
@@ -319,14 +325,21 @@ class Variable:
     def trace_add(self, mode: Literal["array", "read", "write", "unset"], callback: Callable[[str, str, str], object]) -> str: ...
     def trace_remove(self, mode: Literal["array", "read", "write", "unset"], cbname: str) -> None: ...
     def trace_info(self) -> list[tuple[tuple[Literal["array", "read", "write", "unset"], ...], str]]: ...
-    @deprecated("use trace_add() instead of trace()")
-    def trace(self, mode, callback): ...
-    @deprecated("use trace_add() instead of trace_variable()")
-    def trace_variable(self, mode, callback): ...
-    @deprecated("use trace_remove() instead of trace_vdelete()")
-    def trace_vdelete(self, mode, cbname) -> None: ...
-    @deprecated("use trace_info() instead of trace_vinfo()")
-    def trace_vinfo(self): ...
+    if sys.version_info >= (3, 14):
+        @deprecated("Deprecated since Python 3.14. Use `trace_add()` instead.")
+        def trace(self, mode, callback) -> str: ...
+        @deprecated("Deprecated since Python 3.14. Use `trace_add()` instead.")
+        def trace_variable(self, mode, callback) -> str: ...
+        @deprecated("Deprecated since Python 3.14. Use `trace_remove()` instead.")
+        def trace_vdelete(self, mode, cbname) -> None: ...
+        @deprecated("Deprecated since Python 3.14. Use `trace_info()` instead.")
+        def trace_vinfo(self): ...
+    else:
+        def trace(self, mode, callback) -> str: ...
+        def trace_variable(self, mode, callback) -> str: ...
+        def trace_vdelete(self, mode, cbname) -> None: ...
+        def trace_vinfo(self): ...
+
     def __eq__(self, other: object) -> bool: ...
     def __del__(self) -> None: ...
     __hash__: ClassVar[None]  # type: ignore[assignment]
@@ -357,19 +370,21 @@ class BooleanVar(Variable):
 
 def mainloop(n: int = 0) -> None: ...
 
-getint: Incomplete
-getdouble: Incomplete
+getint = int
+getdouble = float
 
 def getboolean(s): ...
 
 _Ts = TypeVarTuple("_Ts")
 
+@type_check_only
 class _GridIndexInfo(TypedDict, total=False):
     minsize: _ScreenUnits
     pad: _ScreenUnits
     uniform: str | None
     weight: int
 
+@type_check_only
 class _BusyInfo(TypedDict):
     cursor: _Cursor
 
@@ -1025,6 +1040,7 @@ class Tk(Misc, Wm):
     def loadtk(self) -> None: ...
     def record(self, script, /): ...
     if sys.version_info < (3, 11):
+        @deprecated("Deprecated since Python 3.9; removed in Python 3.11. Use `splitlist()` instead.")
         def split(self, arg, /): ...
 
     def splitlist(self, arg, /): ...
@@ -1037,6 +1053,7 @@ def Tcl(screenName: str | None = None, baseName: str | None = None, className: s
 _InMiscTotal = TypedDict("_InMiscTotal", {"in": Misc})
 _InMiscNonTotal = TypedDict("_InMiscNonTotal", {"in": Misc}, total=False)
 
+@type_check_only
 class _PackInfo(_InMiscTotal):
     # 'before' and 'after' never appear in _PackInfo
     anchor: _Anchor
@@ -1078,6 +1095,7 @@ class Pack:
     forget = pack_forget
     propagate = Misc.pack_propagate
 
+@type_check_only
 class _PlaceInfo(_InMiscNonTotal):  # empty dict if widget hasn't been placed
     anchor: _Anchor
     bordermode: Literal["inside", "outside", "ignore"]
@@ -1114,6 +1132,7 @@ class Place:
     place = place_configure
     info = place_info
 
+@type_check_only
 class _GridInfo(_InMiscNonTotal):  # empty dict if widget hasn't been gridded
     column: int
     columnspan: int
@@ -3460,7 +3479,7 @@ class Text(Widget, XView, YView):
     def image_configure(
         self,
         index: _TextIndex,
-        cnf: dict[str, Any] | None = {},
+        cnf: dict[str, Any] | None = None,
         *,
         align: Literal["baseline", "bottom", "center", "top"] = ...,
         image: _ImageSpec = ...,
diff --git a/mypy/typeshed/stdlib/tkinter/commondialog.pyi b/mypy/typeshed/stdlib/tkinter/commondialog.pyi
index d5fc2f05ceec..6dba6bd60928 100644
--- a/mypy/typeshed/stdlib/tkinter/commondialog.pyi
+++ b/mypy/typeshed/stdlib/tkinter/commondialog.pyi
@@ -1,12 +1,14 @@
-from _typeshed import Incomplete
 from collections.abc import Mapping
-from typing import ClassVar
+from tkinter import Misc
+from typing import Any, ClassVar
 
 __all__ = ["Dialog"]
 
 class Dialog:
     command: ClassVar[str | None]
-    master: Incomplete | None
-    options: Mapping[str, Incomplete]
-    def __init__(self, master=None, **options) -> None: ...
-    def show(self, **options): ...
+    master: Misc | None
+    # Types of options are very dynamic. They depend on the command and are
+    # sometimes changed to a different type.
+    options: Mapping[str, Any]
+    def __init__(self, master: Misc | None = None, **options: Any) -> None: ...
+    def show(self, **options: Any) -> Any: ...
diff --git a/mypy/typeshed/stdlib/tkinter/dnd.pyi b/mypy/typeshed/stdlib/tkinter/dnd.pyi
index fe2961701c61..521f451a9b2c 100644
--- a/mypy/typeshed/stdlib/tkinter/dnd.pyi
+++ b/mypy/typeshed/stdlib/tkinter/dnd.pyi
@@ -1,8 +1,9 @@
 from tkinter import Event, Misc, Tk, Widget
-from typing import ClassVar, Protocol
+from typing import ClassVar, Protocol, type_check_only
 
 __all__ = ["dnd_start", "DndHandler"]
 
+@type_check_only
 class _DndSource(Protocol):
     def dnd_end(self, target: Widget | None, event: Event[Misc] | None, /) -> None: ...
 
diff --git a/mypy/typeshed/stdlib/tkinter/filedialog.pyi b/mypy/typeshed/stdlib/tkinter/filedialog.pyi
index af033dae97c3..b6ef8f45d035 100644
--- a/mypy/typeshed/stdlib/tkinter/filedialog.pyi
+++ b/mypy/typeshed/stdlib/tkinter/filedialog.pyi
@@ -1,6 +1,6 @@
-from _typeshed import Incomplete, StrOrBytesPath
-from collections.abc import Iterable
-from tkinter import Button, Entry, Frame, Listbox, Misc, Scrollbar, StringVar, Toplevel, commondialog
+from _typeshed import Incomplete, StrOrBytesPath, StrPath
+from collections.abc import Hashable, Iterable
+from tkinter import Button, Entry, Event, Frame, Listbox, Misc, Scrollbar, StringVar, Toplevel, commondialog
 from typing import IO, ClassVar, Literal
 
 __all__ = [
@@ -19,12 +19,12 @@ __all__ = [
     "askdirectory",
 ]
 
-dialogstates: dict[Incomplete, tuple[Incomplete, Incomplete]]
+dialogstates: dict[Hashable, tuple[str, str]]
 
 class FileDialog:
     title: str
-    master: Incomplete
-    directory: Incomplete | None
+    master: Misc
+    directory: str | None
     top: Toplevel
     botframe: Frame
     selection: Entry
@@ -38,23 +38,23 @@ class FileDialog:
     filter_button: Button
     cancel_button: Button
     def __init__(
-        self, master, title=None
+        self, master: Misc, title: str | None = None
     ) -> None: ...  # title is usually a str or None, but e.g. int doesn't raise en exception either
-    how: Incomplete | None
-    def go(self, dir_or_file=".", pattern: str = "*", default: str = "", key=None): ...
-    def quit(self, how=None) -> None: ...
-    def dirs_double_event(self, event) -> None: ...
-    def dirs_select_event(self, event) -> None: ...
-    def files_double_event(self, event) -> None: ...
-    def files_select_event(self, event) -> None: ...
-    def ok_event(self, event) -> None: ...
+    how: str | None
+    def go(self, dir_or_file: StrPath = ".", pattern: StrPath = "*", default: StrPath = "", key: Hashable | None = None): ...
+    def quit(self, how: str | None = None) -> None: ...
+    def dirs_double_event(self, event: Event) -> None: ...
+    def dirs_select_event(self, event: Event) -> None: ...
+    def files_double_event(self, event: Event) -> None: ...
+    def files_select_event(self, event: Event) -> None: ...
+    def ok_event(self, event: Event) -> None: ...
     def ok_command(self) -> None: ...
-    def filter_command(self, event=None) -> None: ...
-    def get_filter(self): ...
-    def get_selection(self): ...
-    def cancel_command(self, event=None) -> None: ...
-    def set_filter(self, dir, pat) -> None: ...
-    def set_selection(self, file) -> None: ...
+    def filter_command(self, event: Event | None = None) -> None: ...
+    def get_filter(self) -> tuple[str, str]: ...
+    def get_selection(self) -> str: ...
+    def cancel_command(self, event: Event | None = None) -> None: ...
+    def set_filter(self, dir: StrPath, pat: StrPath) -> None: ...
+    def set_selection(self, file: StrPath) -> None: ...
 
 class LoadFileDialog(FileDialog):
     title: str
diff --git a/mypy/typeshed/stdlib/tkinter/font.pyi b/mypy/typeshed/stdlib/tkinter/font.pyi
index cab97490be34..327ba7a2432e 100644
--- a/mypy/typeshed/stdlib/tkinter/font.pyi
+++ b/mypy/typeshed/stdlib/tkinter/font.pyi
@@ -2,7 +2,7 @@ import _tkinter
 import itertools
 import sys
 import tkinter
-from typing import Any, ClassVar, Final, Literal, TypedDict, overload
+from typing import Any, ClassVar, Final, Literal, TypedDict, overload, type_check_only
 from typing_extensions import TypeAlias, Unpack
 
 __all__ = ["NORMAL", "ROMAN", "BOLD", "ITALIC", "nametofont", "Font", "families", "names"]
@@ -23,6 +23,7 @@ _FontDescription: TypeAlias = (
     | _tkinter.Tcl_Obj  # A font object constructed in Tcl
 )
 
+@type_check_only
 class _FontDict(TypedDict):
     family: str
     size: int
@@ -31,6 +32,7 @@ class _FontDict(TypedDict):
     underline: bool
     overstrike: bool
 
+@type_check_only
 class _MetricsDict(TypedDict):
     ascent: int
     descent: int
diff --git a/mypy/typeshed/stdlib/tkinter/messagebox.pyi b/mypy/typeshed/stdlib/tkinter/messagebox.pyi
index 902fab62ac05..cd95f0de5f80 100644
--- a/mypy/typeshed/stdlib/tkinter/messagebox.pyi
+++ b/mypy/typeshed/stdlib/tkinter/messagebox.pyi
@@ -1,5 +1,6 @@
+from tkinter import Misc
 from tkinter.commondialog import Dialog
-from typing import ClassVar, Final
+from typing import ClassVar, Final, Literal
 
 __all__ = ["showinfo", "showwarning", "showerror", "askquestion", "askokcancel", "askyesno", "askyesnocancel", "askretrycancel"]
 
@@ -23,11 +24,75 @@ NO: Final = "no"
 class Message(Dialog):
     command: ClassVar[str]
 
-def showinfo(title: str | None = None, message: str | None = None, **options) -> str: ...
-def showwarning(title: str | None = None, message: str | None = None, **options) -> str: ...
-def showerror(title: str | None = None, message: str | None = None, **options) -> str: ...
-def askquestion(title: str | None = None, message: str | None = None, **options) -> str: ...
-def askokcancel(title: str | None = None, message: str | None = None, **options) -> bool: ...
-def askyesno(title: str | None = None, message: str | None = None, **options) -> bool: ...
-def askyesnocancel(title: str | None = None, message: str | None = None, **options) -> bool | None: ...
-def askretrycancel(title: str | None = None, message: str | None = None, **options) -> bool: ...
+def showinfo(
+    title: str | None = None,
+    message: str | None = None,
+    *,
+    detail: str = ...,
+    icon: Literal["error", "info", "question", "warning"] = ...,
+    default: Literal["ok"] = "ok",
+    parent: Misc = ...,
+) -> str: ...
+def showwarning(
+    title: str | None = None,
+    message: str | None = None,
+    *,
+    detail: str = ...,
+    icon: Literal["error", "info", "question", "warning"] = ...,
+    default: Literal["ok"] = "ok",
+    parent: Misc = ...,
+) -> str: ...
+def showerror(
+    title: str | None = None,
+    message: str | None = None,
+    *,
+    detail: str = ...,
+    icon: Literal["error", "info", "question", "warning"] = ...,
+    default: Literal["ok"] = "ok",
+    parent: Misc = ...,
+) -> str: ...
+def askquestion(
+    title: str | None = None,
+    message: str | None = None,
+    *,
+    detail: str = ...,
+    icon: Literal["error", "info", "question", "warning"] = ...,
+    default: Literal["yes", "no"] = ...,
+    parent: Misc = ...,
+) -> str: ...
+def askokcancel(
+    title: str | None = None,
+    message: str | None = None,
+    *,
+    detail: str = ...,
+    icon: Literal["error", "info", "question", "warning"] = ...,
+    default: Literal["ok", "cancel"] = ...,
+    parent: Misc = ...,
+) -> bool: ...
+def askyesno(
+    title: str | None = None,
+    message: str | None = None,
+    *,
+    detail: str = ...,
+    icon: Literal["error", "info", "question", "warning"] = ...,
+    default: Literal["yes", "no"] = ...,
+    parent: Misc = ...,
+) -> bool: ...
+def askyesnocancel(
+    title: str | None = None,
+    message: str | None = None,
+    *,
+    detail: str = ...,
+    icon: Literal["error", "info", "question", "warning"] = ...,
+    default: Literal["cancel", "yes", "no"] = ...,
+    parent: Misc = ...,
+) -> bool | None: ...
+def askretrycancel(
+    title: str | None = None,
+    message: str | None = None,
+    *,
+    detail: str = ...,
+    icon: Literal["error", "info", "question", "warning"] = ...,
+    default: Literal["retry", "cancel"] = ...,
+    parent: Misc = ...,
+) -> bool: ...
diff --git a/mypy/typeshed/stdlib/tkinter/ttk.pyi b/mypy/typeshed/stdlib/tkinter/ttk.pyi
index 50b9cd8f9bcd..86c55eba7006 100644
--- a/mypy/typeshed/stdlib/tkinter/ttk.pyi
+++ b/mypy/typeshed/stdlib/tkinter/ttk.pyi
@@ -1,10 +1,11 @@
 import _tkinter
+import sys
 import tkinter
-from _typeshed import Incomplete, MaybeNone
-from collections.abc import Callable
+from _typeshed import MaybeNone
+from collections.abc import Callable, Iterable
 from tkinter.font import _FontDescription
-from typing import Any, Literal, TypedDict, overload
-from typing_extensions import TypeAlias
+from typing import Any, Literal, TypedDict, overload, type_check_only
+from typing_extensions import Never, TypeAlias, Unpack
 
 __all__ = [
     "Button",
@@ -35,7 +36,7 @@ __all__ = [
 ]
 
 def tclobjs_to_py(adict: dict[Any, Any]) -> dict[Any, Any]: ...
-def setup_master(master=None): ...
+def setup_master(master: tkinter.Misc | None = None): ...
 
 _Padding: TypeAlias = (
     tkinter._ScreenUnits
@@ -48,19 +49,153 @@ _Padding: TypeAlias = (
 # from ttk_widget (aka ttk::widget) manual page, differs from tkinter._Compound
 _TtkCompound: TypeAlias = Literal["", "text", "image", tkinter._Compound]
 
+# Last item (option value to apply) varies between different options so use Any.
+# It could also be any iterable with items matching the tuple, but that case
+# hasn't been added here for consistency with _Padding above.
+_Statespec: TypeAlias = tuple[Unpack[tuple[str, ...]], Any]
+_ImageStatespec: TypeAlias = tuple[Unpack[tuple[str, ...]], tkinter._ImageSpec]
+_VsapiStatespec: TypeAlias = tuple[Unpack[tuple[str, ...]], int]
+
+class _Layout(TypedDict, total=False):
+    side: Literal["left", "right", "top", "bottom"]
+    sticky: str  # consists of letters 'n', 's', 'w', 'e', may contain repeats, may be empty
+    unit: Literal[0, 1] | bool
+    children: _LayoutSpec
+    # Note: there seem to be some other undocumented keys sometimes
+
+# This could be any sequence when passed as a parameter but will always be a list when returned.
+_LayoutSpec: TypeAlias = list[tuple[str, _Layout | None]]
+
+# Keep these in sync with the appropriate methods in Style
+class _ElementCreateImageKwargs(TypedDict, total=False):
+    border: _Padding
+    height: tkinter._ScreenUnits
+    padding: _Padding
+    sticky: str
+    width: tkinter._ScreenUnits
+
+_ElementCreateArgsCrossPlatform: TypeAlias = (
+    # Could be any sequence here but types are not homogenous so just type it as tuple
+    tuple[Literal["image"], tkinter._ImageSpec, Unpack[tuple[_ImageStatespec, ...]], _ElementCreateImageKwargs]
+    | tuple[Literal["from"], str, str]
+    | tuple[Literal["from"], str]  # (fromelement is optional)
+)
+if sys.platform == "win32" and sys.version_info >= (3, 13):
+    class _ElementCreateVsapiKwargsPadding(TypedDict, total=False):
+        padding: _Padding
+
+    class _ElementCreateVsapiKwargsMargin(TypedDict, total=False):
+        padding: _Padding
+
+    class _ElementCreateVsapiKwargsSize(TypedDict):
+        width: tkinter._ScreenUnits
+        height: tkinter._ScreenUnits
+
+    _ElementCreateVsapiKwargsDict: TypeAlias = (
+        _ElementCreateVsapiKwargsPadding | _ElementCreateVsapiKwargsMargin | _ElementCreateVsapiKwargsSize
+    )
+    _ElementCreateArgs: TypeAlias = (  # noqa: Y047  # It doesn't recognise the usage below for whatever reason
+        _ElementCreateArgsCrossPlatform
+        | tuple[Literal["vsapi"], str, int, _ElementCreateVsapiKwargsDict]
+        | tuple[Literal["vsapi"], str, int, _VsapiStatespec, _ElementCreateVsapiKwargsDict]
+    )
+else:
+    _ElementCreateArgs: TypeAlias = _ElementCreateArgsCrossPlatform
+_ThemeSettingsValue = TypedDict(
+    "_ThemeSettingsValue",
+    {
+        "configure": dict[str, Any],
+        "map": dict[str, Iterable[_Statespec]],
+        "layout": _LayoutSpec,
+        "element create": _ElementCreateArgs,
+    },
+    total=False,
+)
+_ThemeSettings: TypeAlias = dict[str, _ThemeSettingsValue]
+
 class Style:
-    master: Incomplete
+    master: tkinter.Misc
     tk: _tkinter.TkappType
     def __init__(self, master: tkinter.Misc | None = None) -> None: ...
-    def configure(self, style, query_opt=None, **kw): ...
-    def map(self, style, query_opt=None, **kw): ...
-    def lookup(self, style, option, state=None, default=None): ...
-    def layout(self, style, layoutspec=None): ...
-    def element_create(self, elementname, etype, *args, **kw) -> None: ...
-    def element_names(self): ...
-    def element_options(self, elementname): ...
-    def theme_create(self, themename, parent=None, settings=None) -> None: ...
-    def theme_settings(self, themename, settings) -> None: ...
+    # For these methods, values given vary between options. Returned values
+    # seem to be str, but this might not always be the case.
+    @overload
+    def configure(self, style: str) -> dict[str, Any] | None: ...  # Returns None if no configuration.
+    @overload
+    def configure(self, style: str, query_opt: str, **kw: Any) -> Any: ...
+    @overload
+    def configure(self, style: str, query_opt: None = None, **kw: Any) -> None: ...
+    @overload
+    def map(self, style: str, query_opt: str) -> _Statespec: ...
+    @overload
+    def map(self, style: str, query_opt: None = None, **kw: Iterable[_Statespec]) -> dict[str, _Statespec]: ...
+    def lookup(self, style: str, option: str, state: Iterable[str] | None = None, default: Any | None = None) -> Any: ...
+    @overload
+    def layout(self, style: str, layoutspec: _LayoutSpec) -> list[Never]: ...  # Always seems to return an empty list
+    @overload
+    def layout(self, style: str, layoutspec: None = None) -> _LayoutSpec: ...
+    @overload
+    def element_create(
+        self,
+        elementname: str,
+        etype: Literal["image"],
+        default_image: tkinter._ImageSpec,
+        /,
+        *imagespec: _ImageStatespec,
+        border: _Padding = ...,
+        height: tkinter._ScreenUnits = ...,
+        padding: _Padding = ...,
+        sticky: str = ...,
+        width: tkinter._ScreenUnits = ...,
+    ) -> None: ...
+    @overload
+    def element_create(self, elementname: str, etype: Literal["from"], themename: str, fromelement: str = ..., /) -> None: ...
+    if sys.platform == "win32" and sys.version_info >= (3, 13):  # and tk version >= 8.6
+        # margin, padding, and (width + height) are mutually exclusive. width
+        # and height must either both be present or not present at all. Note:
+        # There are other undocumented options if you look at ttk's source code.
+        @overload
+        def element_create(
+            self,
+            elementname: str,
+            etype: Literal["vsapi"],
+            class_: str,
+            part: int,
+            vs_statespec: _VsapiStatespec = ...,
+            /,
+            *,
+            padding: _Padding = ...,
+        ) -> None: ...
+        @overload
+        def element_create(
+            self,
+            elementname: str,
+            etype: Literal["vsapi"],
+            class_: str,
+            part: int,
+            vs_statespec: _VsapiStatespec = ...,
+            /,
+            *,
+            margin: _Padding = ...,
+        ) -> None: ...
+        @overload
+        def element_create(
+            self,
+            elementname: str,
+            etype: Literal["vsapi"],
+            class_: str,
+            part: int,
+            vs_statespec: _VsapiStatespec = ...,
+            /,
+            *,
+            width: tkinter._ScreenUnits,
+            height: tkinter._ScreenUnits,
+        ) -> None: ...
+
+    def element_names(self) -> tuple[str, ...]: ...
+    def element_options(self, elementname: str) -> tuple[str, ...]: ...
+    def theme_create(self, themename: str, parent: str | None = None, settings: _ThemeSettings | None = None) -> None: ...
+    def theme_settings(self, themename: str, settings: _ThemeSettings) -> None: ...
     def theme_names(self) -> tuple[str, ...]: ...
     @overload
     def theme_use(self, themename: str) -> None: ...
@@ -615,7 +750,7 @@ class Panedwindow(Widget, tkinter.PanedWindow):
     ) -> dict[str, tuple[str, str, str, Any, Any]] | None: ...
     @overload
     def config(self, cnf: str) -> tuple[str, str, str, Any, Any]: ...
-    forget: Incomplete
+    forget = tkinter.PanedWindow.forget
     def insert(self, pos, child, **kw) -> None: ...
     def pane(self, pane, option=None, **kw): ...
     def sashpos(self, index, newpos=None): ...
@@ -928,6 +1063,7 @@ class Spinbox(Entry):
     config = configure  # type: ignore[assignment]
     def set(self, value: Any) -> None: ...
 
+@type_check_only
 class _TreeviewItemDict(TypedDict):
     text: str
     image: list[str] | Literal[""]  # no idea why it's wrapped in list
@@ -935,6 +1071,7 @@ class _TreeviewItemDict(TypedDict):
     open: bool  # actually 0 or 1
     tags: list[str] | Literal[""]
 
+@type_check_only
 class _TreeviewTagDict(TypedDict):
     # There is also 'text' and 'anchor', but they don't seem to do anything, using them is likely a bug
     foreground: str
@@ -942,6 +1079,7 @@ class _TreeviewTagDict(TypedDict):
     font: _FontDescription
     image: str  # not wrapped in list :D
 
+@type_check_only
 class _TreeviewHeaderDict(TypedDict):
     text: str
     image: list[str] | Literal[""]
@@ -949,6 +1087,7 @@ class _TreeviewHeaderDict(TypedDict):
     command: str
     state: str  # Doesn't seem to appear anywhere else than in these dicts
 
+@type_check_only
 class _TreeviewColumnDict(TypedDict):
     width: int
     minwidth: int
diff --git a/mypy/typeshed/stdlib/token.pyi b/mypy/typeshed/stdlib/token.pyi
index 7c13b15d95b7..fd1b10da1d12 100644
--- a/mypy/typeshed/stdlib/token.pyi
+++ b/mypy/typeshed/stdlib/token.pyi
@@ -1,4 +1,5 @@
 import sys
+from typing import Final
 
 __all__ = [
     "AMPER",
@@ -81,87 +82,87 @@ if sys.version_info >= (3, 12):
 if sys.version_info >= (3, 14):
     __all__ += ["TSTRING_START", "TSTRING_MIDDLE", "TSTRING_END"]
 
-ENDMARKER: int
-NAME: int
-NUMBER: int
-STRING: int
-NEWLINE: int
-INDENT: int
-DEDENT: int
-LPAR: int
-RPAR: int
-LSQB: int
-RSQB: int
-COLON: int
-COMMA: int
-SEMI: int
-PLUS: int
-MINUS: int
-STAR: int
-SLASH: int
-VBAR: int
-AMPER: int
-LESS: int
-GREATER: int
-EQUAL: int
-DOT: int
-PERCENT: int
-LBRACE: int
-RBRACE: int
-EQEQUAL: int
-NOTEQUAL: int
-LESSEQUAL: int
-GREATEREQUAL: int
-TILDE: int
-CIRCUMFLEX: int
-LEFTSHIFT: int
-RIGHTSHIFT: int
-DOUBLESTAR: int
-PLUSEQUAL: int
-MINEQUAL: int
-STAREQUAL: int
-SLASHEQUAL: int
-PERCENTEQUAL: int
-AMPEREQUAL: int
-VBAREQUAL: int
-CIRCUMFLEXEQUAL: int
-LEFTSHIFTEQUAL: int
-RIGHTSHIFTEQUAL: int
-DOUBLESTAREQUAL: int
-DOUBLESLASH: int
-DOUBLESLASHEQUAL: int
-AT: int
-RARROW: int
-ELLIPSIS: int
-ATEQUAL: int
+ENDMARKER: Final[int]
+NAME: Final[int]
+NUMBER: Final[int]
+STRING: Final[int]
+NEWLINE: Final[int]
+INDENT: Final[int]
+DEDENT: Final[int]
+LPAR: Final[int]
+RPAR: Final[int]
+LSQB: Final[int]
+RSQB: Final[int]
+COLON: Final[int]
+COMMA: Final[int]
+SEMI: Final[int]
+PLUS: Final[int]
+MINUS: Final[int]
+STAR: Final[int]
+SLASH: Final[int]
+VBAR: Final[int]
+AMPER: Final[int]
+LESS: Final[int]
+GREATER: Final[int]
+EQUAL: Final[int]
+DOT: Final[int]
+PERCENT: Final[int]
+LBRACE: Final[int]
+RBRACE: Final[int]
+EQEQUAL: Final[int]
+NOTEQUAL: Final[int]
+LESSEQUAL: Final[int]
+GREATEREQUAL: Final[int]
+TILDE: Final[int]
+CIRCUMFLEX: Final[int]
+LEFTSHIFT: Final[int]
+RIGHTSHIFT: Final[int]
+DOUBLESTAR: Final[int]
+PLUSEQUAL: Final[int]
+MINEQUAL: Final[int]
+STAREQUAL: Final[int]
+SLASHEQUAL: Final[int]
+PERCENTEQUAL: Final[int]
+AMPEREQUAL: Final[int]
+VBAREQUAL: Final[int]
+CIRCUMFLEXEQUAL: Final[int]
+LEFTSHIFTEQUAL: Final[int]
+RIGHTSHIFTEQUAL: Final[int]
+DOUBLESTAREQUAL: Final[int]
+DOUBLESLASH: Final[int]
+DOUBLESLASHEQUAL: Final[int]
+AT: Final[int]
+RARROW: Final[int]
+ELLIPSIS: Final[int]
+ATEQUAL: Final[int]
 if sys.version_info < (3, 13):
-    AWAIT: int
-    ASYNC: int
-OP: int
-ERRORTOKEN: int
-N_TOKENS: int
-NT_OFFSET: int
-tok_name: dict[int, str]
-COMMENT: int
-NL: int
-ENCODING: int
-TYPE_COMMENT: int
-TYPE_IGNORE: int
-COLONEQUAL: int
-EXACT_TOKEN_TYPES: dict[str, int]
+    AWAIT: Final[int]
+    ASYNC: Final[int]
+OP: Final[int]
+ERRORTOKEN: Final[int]
+N_TOKENS: Final[int]
+NT_OFFSET: Final[int]
+tok_name: Final[dict[int, str]]
+COMMENT: Final[int]
+NL: Final[int]
+ENCODING: Final[int]
+TYPE_COMMENT: Final[int]
+TYPE_IGNORE: Final[int]
+COLONEQUAL: Final[int]
+EXACT_TOKEN_TYPES: Final[dict[str, int]]
 if sys.version_info >= (3, 10):
-    SOFT_KEYWORD: int
+    SOFT_KEYWORD: Final[int]
 
 if sys.version_info >= (3, 12):
-    EXCLAMATION: int
-    FSTRING_END: int
-    FSTRING_MIDDLE: int
-    FSTRING_START: int
+    EXCLAMATION: Final[int]
+    FSTRING_END: Final[int]
+    FSTRING_MIDDLE: Final[int]
+    FSTRING_START: Final[int]
 
 if sys.version_info >= (3, 14):
-    TSTRING_START: int
-    TSTRING_MIDDLE: int
-    TSTRING_END: int
+    TSTRING_START: Final[int]
+    TSTRING_MIDDLE: Final[int]
+    TSTRING_END: Final[int]
 
 def ISTERMINAL(x: int) -> bool: ...
 def ISNONTERMINAL(x: int) -> bool: ...
diff --git a/mypy/typeshed/stdlib/tokenize.pyi b/mypy/typeshed/stdlib/tokenize.pyi
index b658740a1ad7..00a24b4eea07 100644
--- a/mypy/typeshed/stdlib/tokenize.pyi
+++ b/mypy/typeshed/stdlib/tokenize.pyi
@@ -3,9 +3,14 @@ from _typeshed import FileDescriptorOrPath
 from collections.abc import Callable, Generator, Iterable, Sequence
 from re import Pattern
 from token import *
-from token import EXACT_TOKEN_TYPES as EXACT_TOKEN_TYPES
-from typing import Any, NamedTuple, TextIO, type_check_only
-from typing_extensions import TypeAlias
+from typing import Any, Final, NamedTuple, TextIO, type_check_only
+from typing_extensions import TypeAlias, disjoint_base
+
+if sys.version_info < (3, 12):
+    # Avoid double assignment to Final name by imports, which pyright objects to.
+    # EXACT_TOKEN_TYPES is already defined by 'from token import *' above
+    # in Python 3.12+.
+    from token import EXACT_TOKEN_TYPES as EXACT_TOKEN_TYPES
 
 __all__ = [
     "AMPER",
@@ -96,8 +101,8 @@ if sys.version_info >= (3, 13):
 if sys.version_info >= (3, 14):
     __all__ += ["TSTRING_START", "TSTRING_MIDDLE", "TSTRING_END"]
 
-cookie_re: Pattern[str]
-blank_re: Pattern[bytes]
+cookie_re: Final[Pattern[str]]
+blank_re: Final[Pattern[bytes]]
 
 _Position: TypeAlias = tuple[int, int]
 
@@ -110,9 +115,16 @@ class _TokenInfo(NamedTuple):
     end: _Position
     line: str
 
-class TokenInfo(_TokenInfo):
-    @property
-    def exact_type(self) -> int: ...
+if sys.version_info >= (3, 12):
+    class TokenInfo(_TokenInfo):
+        @property
+        def exact_type(self) -> int: ...
+
+else:
+    @disjoint_base
+    class TokenInfo(_TokenInfo):
+        @property
+        def exact_type(self) -> int: ...
 
 # Backwards compatible tokens can be sequences of a shorter length too
 _Token: TypeAlias = TokenInfo | Sequence[int | str | _Position]
@@ -146,46 +158,46 @@ def group(*choices: str) -> str: ...  # undocumented
 def any(*choices: str) -> str: ...  # undocumented
 def maybe(*choices: str) -> str: ...  # undocumented
 
-Whitespace: str  # undocumented
-Comment: str  # undocumented
-Ignore: str  # undocumented
-Name: str  # undocumented
-
-Hexnumber: str  # undocumented
-Binnumber: str  # undocumented
-Octnumber: str  # undocumented
-Decnumber: str  # undocumented
-Intnumber: str  # undocumented
-Exponent: str  # undocumented
-Pointfloat: str  # undocumented
-Expfloat: str  # undocumented
-Floatnumber: str  # undocumented
-Imagnumber: str  # undocumented
-Number: str  # undocumented
+Whitespace: Final[str]  # undocumented
+Comment: Final[str]  # undocumented
+Ignore: Final[str]  # undocumented
+Name: Final[str]  # undocumented
+
+Hexnumber: Final[str]  # undocumented
+Binnumber: Final[str]  # undocumented
+Octnumber: Final[str]  # undocumented
+Decnumber: Final[str]  # undocumented
+Intnumber: Final[str]  # undocumented
+Exponent: Final[str]  # undocumented
+Pointfloat: Final[str]  # undocumented
+Expfloat: Final[str]  # undocumented
+Floatnumber: Final[str]  # undocumented
+Imagnumber: Final[str]  # undocumented
+Number: Final[str]  # undocumented
 
 def _all_string_prefixes() -> set[str]: ...  # undocumented
 
-StringPrefix: str  # undocumented
+StringPrefix: Final[str]  # undocumented
 
-Single: str  # undocumented
-Double: str  # undocumented
-Single3: str  # undocumented
-Double3: str  # undocumented
-Triple: str  # undocumented
-String: str  # undocumented
+Single: Final[str]  # undocumented
+Double: Final[str]  # undocumented
+Single3: Final[str]  # undocumented
+Double3: Final[str]  # undocumented
+Triple: Final[str]  # undocumented
+String: Final[str]  # undocumented
 
-Special: str  # undocumented
-Funny: str  # undocumented
+Special: Final[str]  # undocumented
+Funny: Final[str]  # undocumented
 
-PlainToken: str  # undocumented
-Token: str  # undocumented
+PlainToken: Final[str]  # undocumented
+Token: Final[str]  # undocumented
 
-ContStr: str  # undocumented
-PseudoExtras: str  # undocumented
-PseudoToken: str  # undocumented
+ContStr: Final[str]  # undocumented
+PseudoExtras: Final[str]  # undocumented
+PseudoToken: Final[str]  # undocumented
 
-endpats: dict[str, str]  # undocumented
-single_quoted: set[str]  # undocumented
-triple_quoted: set[str]  # undocumented
+endpats: Final[dict[str, str]]  # undocumented
+single_quoted: Final[set[str]]  # undocumented
+triple_quoted: Final[set[str]]  # undocumented
 
-tabsize: int  # undocumented
+tabsize: Final = 8  # undocumented
diff --git a/mypy/typeshed/stdlib/tomllib.pyi b/mypy/typeshed/stdlib/tomllib.pyi
index c160ffc38bfd..4ff4097f8313 100644
--- a/mypy/typeshed/stdlib/tomllib.pyi
+++ b/mypy/typeshed/stdlib/tomllib.pyi
@@ -16,7 +16,7 @@ if sys.version_info >= (3, 14):
         @overload
         def __init__(self, msg: str, doc: str, pos: int) -> None: ...
         @overload
-        @deprecated("Deprecated in Python 3.14; Please set 'msg', 'doc' and 'pos' arguments only.")
+        @deprecated("Deprecated since Python 3.14. Set the 'msg', 'doc' and 'pos' arguments only.")
         def __init__(self, msg: str | type = ..., doc: str | type = ..., pos: int | type = ..., *args: Any) -> None: ...
 
 else:
diff --git a/mypy/typeshed/stdlib/traceback.pyi b/mypy/typeshed/stdlib/traceback.pyi
index 4553dbd08384..d587295cd1cf 100644
--- a/mypy/typeshed/stdlib/traceback.pyi
+++ b/mypy/typeshed/stdlib/traceback.pyi
@@ -138,7 +138,7 @@ class TracebackException:
         @property
         def exc_type_str(self) -> str: ...
         @property
-        @deprecated("Deprecated in 3.13. Use exc_type_str instead.")
+        @deprecated("Deprecated since Python 3.13. Use `exc_type_str` instead.")
         def exc_type(self) -> type[BaseException] | None: ...
     else:
         exc_type: type[BaseException]
@@ -245,6 +245,23 @@ class TracebackException:
         def print(self, *, file: SupportsWrite[str] | None = None, chain: bool = True) -> None: ...
 
 class FrameSummary:
+    if sys.version_info >= (3, 13):
+        __slots__ = (
+            "filename",
+            "lineno",
+            "end_lineno",
+            "colno",
+            "end_colno",
+            "name",
+            "_lines",
+            "_lines_dedented",
+            "locals",
+            "_code",
+        )
+    elif sys.version_info >= (3, 11):
+        __slots__ = ("filename", "lineno", "end_lineno", "colno", "end_colno", "name", "_line", "locals")
+    else:
+        __slots__ = ("filename", "lineno", "name", "_line", "locals")
     if sys.version_info >= (3, 11):
         def __init__(
             self,
diff --git a/mypy/typeshed/stdlib/tracemalloc.pyi b/mypy/typeshed/stdlib/tracemalloc.pyi
index 05d98ae127d8..31d8f7445639 100644
--- a/mypy/typeshed/stdlib/tracemalloc.pyi
+++ b/mypy/typeshed/stdlib/tracemalloc.pyi
@@ -32,6 +32,7 @@ class Filter(BaseFilter):
     ) -> None: ...
 
 class Statistic:
+    __slots__ = ("traceback", "size", "count")
     count: int
     size: int
     traceback: Traceback
@@ -40,6 +41,7 @@ class Statistic:
     def __hash__(self) -> int: ...
 
 class StatisticDiff:
+    __slots__ = ("traceback", "size", "size_diff", "count", "count_diff")
     count: int
     count_diff: int
     size: int
@@ -52,6 +54,7 @@ class StatisticDiff:
 _FrameTuple: TypeAlias = tuple[str, int]
 
 class Frame:
+    __slots__ = ("_frame",)
     @property
     def filename(self) -> str: ...
     @property
@@ -72,6 +75,7 @@ class Frame:
 _TraceTuple: TypeAlias = tuple[int, int, Sequence[_FrameTuple], int | None] | tuple[int, int, Sequence[_FrameTuple]]
 
 class Trace:
+    __slots__ = ("_trace",)
     @property
     def domain(self) -> int: ...
     @property
@@ -83,6 +87,7 @@ class Trace:
     def __hash__(self) -> int: ...
 
 class Traceback(Sequence[Frame]):
+    __slots__ = ("_frames", "_total_nframe")
     @property
     def total_nframe(self) -> int | None: ...
     def __init__(self, frames: Sequence[_FrameTuple], total_nframe: int | None = None) -> None: ...
diff --git a/mypy/typeshed/stdlib/tty.pyi b/mypy/typeshed/stdlib/tty.pyi
index 0611879cf1b2..ca3f0013b20e 100644
--- a/mypy/typeshed/stdlib/tty.pyi
+++ b/mypy/typeshed/stdlib/tty.pyi
@@ -15,13 +15,13 @@ if sys.platform != "win32":
     _FD: TypeAlias = int | IO[str]
 
     # XXX: Undocumented integer constants
-    IFLAG: Final[int]
-    OFLAG: Final[int]
-    CFLAG: Final[int]
-    LFLAG: Final[int]
-    ISPEED: Final[int]
-    OSPEED: Final[int]
-    CC: Final[int]
+    IFLAG: Final = 0
+    OFLAG: Final = 1
+    CFLAG: Final = 2
+    LFLAG: Final = 3
+    ISPEED: Final = 4
+    OSPEED: Final = 5
+    CC: Final = 6
     def setraw(fd: _FD, when: int = 2) -> _ModeSetterReturn: ...
     def setcbreak(fd: _FD, when: int = 2) -> _ModeSetterReturn: ...
 
diff --git a/mypy/typeshed/stdlib/turtle.pyi b/mypy/typeshed/stdlib/turtle.pyi
index 9c62c64e718a..0b93429904c5 100644
--- a/mypy/typeshed/stdlib/turtle.pyi
+++ b/mypy/typeshed/stdlib/turtle.pyi
@@ -3,8 +3,8 @@ from _typeshed import StrPath
 from collections.abc import Callable, Generator, Sequence
 from contextlib import contextmanager
 from tkinter import Canvas, Frame, Misc, PhotoImage, Scrollbar
-from typing import Any, ClassVar, Literal, TypedDict, overload
-from typing_extensions import Self, TypeAlias
+from typing import Any, ClassVar, Literal, TypedDict, overload, type_check_only
+from typing_extensions import Self, TypeAlias, deprecated, disjoint_base
 
 __all__ = [
     "ScrolledCanvas",
@@ -146,6 +146,7 @@ if sys.version_info < (3, 13):
 _Color: TypeAlias = str | tuple[float, float, float]
 _AnyColor: TypeAlias = Any
 
+@type_check_only
 class _PenState(TypedDict):
     shown: bool
     pendown: bool
@@ -162,18 +163,34 @@ class _PenState(TypedDict):
 _Speed: TypeAlias = str | float
 _PolygonCoords: TypeAlias = Sequence[tuple[float, float]]
 
-class Vec2D(tuple[float, float]):
-    def __new__(cls, x: float, y: float) -> Self: ...
-    def __add__(self, other: tuple[float, float]) -> Vec2D: ...  # type: ignore[override]
-    @overload  # type: ignore[override]
-    def __mul__(self, other: Vec2D) -> float: ...
-    @overload
-    def __mul__(self, other: float) -> Vec2D: ...
-    def __rmul__(self, other: float) -> Vec2D: ...  # type: ignore[override]
-    def __sub__(self, other: tuple[float, float]) -> Vec2D: ...
-    def __neg__(self) -> Vec2D: ...
-    def __abs__(self) -> float: ...
-    def rotate(self, angle: float) -> Vec2D: ...
+if sys.version_info >= (3, 12):
+    class Vec2D(tuple[float, float]):
+        def __new__(cls, x: float, y: float) -> Self: ...
+        def __add__(self, other: tuple[float, float]) -> Vec2D: ...  # type: ignore[override]
+        @overload  # type: ignore[override]
+        def __mul__(self, other: Vec2D) -> float: ...
+        @overload
+        def __mul__(self, other: float) -> Vec2D: ...
+        def __rmul__(self, other: float) -> Vec2D: ...  # type: ignore[override]
+        def __sub__(self, other: tuple[float, float]) -> Vec2D: ...
+        def __neg__(self) -> Vec2D: ...
+        def __abs__(self) -> float: ...
+        def rotate(self, angle: float) -> Vec2D: ...
+
+else:
+    @disjoint_base
+    class Vec2D(tuple[float, float]):
+        def __new__(cls, x: float, y: float) -> Self: ...
+        def __add__(self, other: tuple[float, float]) -> Vec2D: ...  # type: ignore[override]
+        @overload  # type: ignore[override]
+        def __mul__(self, other: Vec2D) -> float: ...
+        @overload
+        def __mul__(self, other: float) -> Vec2D: ...
+        def __rmul__(self, other: float) -> Vec2D: ...  # type: ignore[override]
+        def __sub__(self, other: tuple[float, float]) -> Vec2D: ...
+        def __neg__(self) -> Vec2D: ...
+        def __abs__(self) -> float: ...
+        def rotate(self, angle: float) -> Vec2D: ...
 
 # Does not actually inherit from Canvas, but dynamically gets all methods of Canvas
 class ScrolledCanvas(Canvas, Frame):  # type: ignore[misc]
@@ -425,6 +442,7 @@ class RawTurtle(TPen, TNavigator):  # type: ignore[misc]  # Conflicting methods
     def get_shapepoly(self) -> _PolygonCoords | None: ...
 
     if sys.version_info < (3, 13):
+        @deprecated("Deprecated since Python 3.1; removed in Python 3.13. Use `tiltangle()` instead.")
         def settiltangle(self, angle: float) -> None: ...
 
     @overload
@@ -487,19 +505,8 @@ Pen = Turtle
 
 def write_docstringdict(filename: str = "turtle_docstringdict") -> None: ...
 
-# Note: it's somewhat unfortunate that we have to copy the function signatures.
-# It would be nice if we could partially reduce the redundancy by doing something
-# like the following:
-#
-#     _screen: Screen
-#     clear = _screen.clear
-#
-# However, it seems pytype does not support this type of syntax in pyi files.
-
 # Functions copied from TurtleScreenBase:
 
-# Note: mainloop() was always present in the global scope, but was added to
-# TurtleScreenBase in Python 3.0
 def mainloop() -> None: ...
 def textinput(title: str, prompt: str) -> str | None: ...
 def numinput(
@@ -717,6 +724,7 @@ def shapetransform(
 def get_shapepoly() -> _PolygonCoords | None: ...
 
 if sys.version_info < (3, 13):
+    @deprecated("Deprecated since Python 3.1; removed in Python 3.13. Use `tiltangle()` instead.")
     def settiltangle(angle: float) -> None: ...
 
 @overload
diff --git a/mypy/typeshed/stdlib/types.pyi b/mypy/typeshed/stdlib/types.pyi
index d9f8e8756833..591d5da2360d 100644
--- a/mypy/typeshed/stdlib/types.pyi
+++ b/mypy/typeshed/stdlib/types.pyi
@@ -17,7 +17,7 @@ from collections.abc import (
 )
 from importlib.machinery import ModuleSpec
 from typing import Any, ClassVar, Literal, TypeVar, final, overload
-from typing_extensions import ParamSpec, Self, TypeAliasType, TypeVarTuple, deprecated
+from typing_extensions import ParamSpec, Self, TypeAliasType, TypeVarTuple, deprecated, disjoint_base
 
 if sys.version_info >= (3, 14):
     from _typeshed import AnnotateFunc
@@ -151,7 +151,7 @@ class CodeType:
     def co_firstlineno(self) -> int: ...
     if sys.version_info >= (3, 10):
         @property
-        @deprecated("Will be removed in Python 3.15. Use the co_lines() method instead.")
+        @deprecated("Deprecated since Python 3.10; will be removed in Python 3.15. Use `CodeType.co_lines()` instead.")
         def co_lnotab(self) -> bytes: ...
     else:
         @property
@@ -323,26 +323,42 @@ class MappingProxyType(Mapping[_KT, _VT_co]):
     @overload
     def get(self, key: _KT, /) -> _VT_co | None: ...
     @overload
-    def get(self, key: _KT, default: _VT_co | _T2, /) -> _VT_co | _T2: ...
+    def get(self, key: _KT, default: _VT_co, /) -> _VT_co: ...  # type: ignore[misc] # pyright: ignore[reportGeneralTypeIssues] # Covariant type as parameter
+    @overload
+    def get(self, key: _KT, default: _T2, /) -> _VT_co | _T2: ...
     def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
     def __reversed__(self) -> Iterator[_KT]: ...
     def __or__(self, value: Mapping[_T1, _T2], /) -> dict[_KT | _T1, _VT_co | _T2]: ...
     def __ror__(self, value: Mapping[_T1, _T2], /) -> dict[_KT | _T1, _VT_co | _T2]: ...
 
-class SimpleNamespace:
-    __hash__: ClassVar[None]  # type: ignore[assignment]
-    if sys.version_info >= (3, 13):
-        def __init__(self, mapping_or_iterable: Mapping[str, Any] | Iterable[tuple[str, Any]] = (), /, **kwargs: Any) -> None: ...
-    else:
-        def __init__(self, **kwargs: Any) -> None: ...
+if sys.version_info >= (3, 12):
+    @disjoint_base
+    class SimpleNamespace:
+        __hash__: ClassVar[None]  # type: ignore[assignment]
+        if sys.version_info >= (3, 13):
+            def __init__(
+                self, mapping_or_iterable: Mapping[str, Any] | Iterable[tuple[str, Any]] = (), /, **kwargs: Any
+            ) -> None: ...
+        else:
+            def __init__(self, **kwargs: Any) -> None: ...
 
-    def __eq__(self, value: object, /) -> bool: ...
-    def __getattribute__(self, name: str, /) -> Any: ...
-    def __setattr__(self, name: str, value: Any, /) -> None: ...
-    def __delattr__(self, name: str, /) -> None: ...
-    if sys.version_info >= (3, 13):
-        def __replace__(self, **kwargs: Any) -> Self: ...
+        def __eq__(self, value: object, /) -> bool: ...
+        def __getattribute__(self, name: str, /) -> Any: ...
+        def __setattr__(self, name: str, value: Any, /) -> None: ...
+        def __delattr__(self, name: str, /) -> None: ...
+        if sys.version_info >= (3, 13):
+            def __replace__(self, **kwargs: Any) -> Self: ...
+
+else:
+    class SimpleNamespace:
+        __hash__: ClassVar[None]  # type: ignore[assignment]
+        def __init__(self, **kwargs: Any) -> None: ...
+        def __eq__(self, value: object, /) -> bool: ...
+        def __getattribute__(self, name: str, /) -> Any: ...
+        def __setattr__(self, name: str, value: Any, /) -> None: ...
+        def __delattr__(self, name: str, /) -> None: ...
 
+@disjoint_base
 class ModuleType:
     __name__: str
     __file__: str | None
@@ -388,7 +404,7 @@ class GeneratorType(Generator[_YieldT_co, _SendT_contra, _ReturnT_co]):
     @property
     def gi_running(self) -> bool: ...
     @property
-    def gi_yieldfrom(self) -> GeneratorType[_YieldT_co, _SendT_contra, Any] | None: ...
+    def gi_yieldfrom(self) -> Iterator[_YieldT_co] | None: ...
     if sys.version_info >= (3, 11):
         @property
         def gi_suspended(self) -> bool: ...
@@ -659,7 +675,7 @@ _P = ParamSpec("_P")
 def coroutine(func: Callable[_P, Generator[Any, Any, _R]]) -> Callable[_P, Awaitable[_R]]: ...
 @overload
 def coroutine(func: _Fn) -> _Fn: ...
-
+@disjoint_base
 class GenericAlias:
     @property
     def __origin__(self) -> type | TypeAliasType: ...
diff --git a/mypy/typeshed/stdlib/typing.pyi b/mypy/typeshed/stdlib/typing.pyi
index 79ab9eee924f..15a5864613d1 100644
--- a/mypy/typeshed/stdlib/typing.pyi
+++ b/mypy/typeshed/stdlib/typing.pyi
@@ -1,12 +1,11 @@
 # Since this module defines "overload" it is not recognized by Ruff as typing.overload
-# ruff: noqa: F811
 # TODO: The collections import is required, otherwise mypy crashes.
 # https://github.com/python/mypy/issues/16744
 import collections  # noqa: F401  # pyright: ignore[reportUnusedImport]
 import sys
 import typing_extensions
 from _collections_abc import dict_items, dict_keys, dict_values
-from _typeshed import IdentityFunction, ReadableBuffer, SupportsKeysAndGetItem
+from _typeshed import IdentityFunction, ReadableBuffer, SupportsGetItem, SupportsGetItemViewable, SupportsKeysAndGetItem, Viewable
 from abc import ABCMeta, abstractmethod
 from re import Match as Match, Pattern as Pattern
 from types import (
@@ -147,7 +146,9 @@ if sys.version_info >= (3, 13):
 # from _typeshed import AnnotationForm
 
 class Any: ...
-class _Final: ...
+
+class _Final:
+    __slots__ = ("__weakref__",)
 
 def final(f: _T) -> _T: ...
 @final
@@ -208,12 +209,12 @@ class TypeVar:
             contravariant: bool = False,
         ) -> None: ...
     if sys.version_info >= (3, 10):
-        def __or__(self, right: Any) -> _SpecialForm: ...  # AnnotationForm
-        def __ror__(self, left: Any) -> _SpecialForm: ...  # AnnotationForm
+        def __or__(self, right: Any, /) -> _SpecialForm: ...  # AnnotationForm
+        def __ror__(self, left: Any, /) -> _SpecialForm: ...  # AnnotationForm
     if sys.version_info >= (3, 11):
-        def __typing_subst__(self, arg: Any) -> Any: ...
+        def __typing_subst__(self, arg: Any, /) -> Any: ...
     if sys.version_info >= (3, 13):
-        def __typing_prepare_subst__(self, alias: Any, args: Any) -> tuple[Any, ...]: ...
+        def __typing_prepare_subst__(self, alias: Any, args: Any, /) -> tuple[Any, ...]: ...
         def has_default(self) -> bool: ...
     if sys.version_info >= (3, 14):
         @property
@@ -230,13 +231,13 @@ _promote = object()
 # N.B. Keep this definition in sync with typing_extensions._SpecialForm
 @final
 class _SpecialForm(_Final):
+    __slots__ = ("_name", "__doc__", "_getitem")
     def __getitem__(self, parameters: Any) -> object: ...
     if sys.version_info >= (3, 10):
         def __or__(self, other: Any) -> _SpecialForm: ...
         def __ror__(self, other: Any) -> _SpecialForm: ...
 
 Union: _SpecialForm
-Generic: _SpecialForm
 Protocol: _SpecialForm
 Callable: _SpecialForm
 Type: _SpecialForm
@@ -274,8 +275,8 @@ if sys.version_info >= (3, 11):
             def __init__(self, name: str) -> None: ...
 
         def __iter__(self) -> Any: ...
-        def __typing_subst__(self, arg: Never) -> Never: ...
-        def __typing_prepare_subst__(self, alias: Any, args: Any) -> tuple[Any, ...]: ...
+        def __typing_subst__(self, arg: Never, /) -> Never: ...
+        def __typing_prepare_subst__(self, alias: Any, args: Any, /) -> tuple[Any, ...]: ...
         if sys.version_info >= (3, 14):
             @property
             def evaluate_default(self) -> EvaluateFunc | None: ...
@@ -290,7 +291,7 @@ if sys.version_info >= (3, 10):
         else:
             def __init__(self, origin: ParamSpec) -> None: ...
 
-        def __eq__(self, other: object) -> bool: ...
+        def __eq__(self, other: object, /) -> bool: ...
         __hash__: ClassVar[None]  # type: ignore[assignment]
 
     @final
@@ -302,7 +303,7 @@ if sys.version_info >= (3, 10):
         else:
             def __init__(self, origin: ParamSpec) -> None: ...
 
-        def __eq__(self, other: object) -> bool: ...
+        def __eq__(self, other: object, /) -> bool: ...
         __hash__: ClassVar[None]  # type: ignore[assignment]
 
     @final
@@ -366,11 +367,11 @@ if sys.version_info >= (3, 10):
         @property
         def kwargs(self) -> ParamSpecKwargs: ...
         if sys.version_info >= (3, 11):
-            def __typing_subst__(self, arg: Any) -> Any: ...
-            def __typing_prepare_subst__(self, alias: Any, args: Any) -> tuple[Any, ...]: ...
+            def __typing_subst__(self, arg: Any, /) -> Any: ...
+            def __typing_prepare_subst__(self, alias: Any, args: Any, /) -> tuple[Any, ...]: ...
 
-        def __or__(self, right: Any) -> _SpecialForm: ...
-        def __ror__(self, left: Any) -> _SpecialForm: ...
+        def __or__(self, right: Any, /) -> _SpecialForm: ...
+        def __ror__(self, left: Any, /) -> _SpecialForm: ...
         if sys.version_info >= (3, 13):
             def has_default(self) -> bool: ...
         if sys.version_info >= (3, 14):
@@ -420,6 +421,7 @@ def type_check_only(func_or_cls: _FT) -> _FT: ...
 
 # Type aliases and type constructors
 
+@type_check_only
 class _Alias:
     # Class for defining generic aliases for library types.
     def __getitem__(self, typeargs: Any) -> Any: ...
@@ -440,6 +442,20 @@ Annotated: _SpecialForm
 # Predefined type variables.
 AnyStr = TypeVar("AnyStr", str, bytes)  # noqa: Y001
 
+@type_check_only
+class _Generic:
+    if sys.version_info < (3, 12):
+        __slots__ = ()
+
+    if sys.version_info >= (3, 10):
+        @classmethod
+        def __class_getitem__(cls, args: TypeVar | ParamSpec | tuple[TypeVar | ParamSpec, ...]) -> _Final: ...
+    else:
+        @classmethod
+        def __class_getitem__(cls, args: TypeVar | tuple[TypeVar, ...]) -> _Final: ...
+
+Generic: type[_Generic]
+
 class _ProtocolMeta(ABCMeta):
     if sys.version_info >= (3, 12):
         def __init__(cls, *args: Any, **kwargs: Any) -> None: ...
@@ -449,36 +465,43 @@ class _ProtocolMeta(ABCMeta):
 def runtime_checkable(cls: _TC) -> _TC: ...
 @runtime_checkable
 class SupportsInt(Protocol, metaclass=ABCMeta):
+    __slots__ = ()
     @abstractmethod
     def __int__(self) -> int: ...
 
 @runtime_checkable
 class SupportsFloat(Protocol, metaclass=ABCMeta):
+    __slots__ = ()
     @abstractmethod
     def __float__(self) -> float: ...
 
 @runtime_checkable
 class SupportsComplex(Protocol, metaclass=ABCMeta):
+    __slots__ = ()
     @abstractmethod
     def __complex__(self) -> complex: ...
 
 @runtime_checkable
 class SupportsBytes(Protocol, metaclass=ABCMeta):
+    __slots__ = ()
     @abstractmethod
     def __bytes__(self) -> bytes: ...
 
 @runtime_checkable
 class SupportsIndex(Protocol, metaclass=ABCMeta):
+    __slots__ = ()
     @abstractmethod
     def __index__(self) -> int: ...
 
 @runtime_checkable
 class SupportsAbs(Protocol[_T_co]):
+    __slots__ = ()
     @abstractmethod
     def __abs__(self) -> _T_co: ...
 
 @runtime_checkable
 class SupportsRound(Protocol[_T_co]):
+    __slots__ = ()
     @overload
     @abstractmethod
     def __round__(self) -> int: ...
@@ -703,14 +726,15 @@ class MutableSet(AbstractSet[_T]):
     def __isub__(self, it: AbstractSet[Any]) -> typing_extensions.Self: ...
 
 class MappingView(Sized):
-    def __init__(self, mapping: Mapping[Any, Any]) -> None: ...  # undocumented
+    __slots__ = ("_mapping",)
+    def __init__(self, mapping: Sized) -> None: ...  # undocumented
     def __len__(self) -> int: ...
 
 class ItemsView(MappingView, AbstractSet[tuple[_KT_co, _VT_co]], Generic[_KT_co, _VT_co]):
-    def __init__(self, mapping: Mapping[_KT_co, _VT_co]) -> None: ...  # undocumented
+    def __init__(self, mapping: SupportsGetItemViewable[_KT_co, _VT_co]) -> None: ...  # undocumented
     def __and__(self, other: Iterable[Any]) -> set[tuple[_KT_co, _VT_co]]: ...
     def __rand__(self, other: Iterable[_T]) -> set[_T]: ...
-    def __contains__(self, item: object) -> bool: ...
+    def __contains__(self, item: tuple[object, object]) -> bool: ...  # type: ignore[override]
     def __iter__(self) -> Iterator[tuple[_KT_co, _VT_co]]: ...
     def __or__(self, other: Iterable[_T]) -> set[tuple[_KT_co, _VT_co] | _T]: ...
     def __ror__(self, other: Iterable[_T]) -> set[tuple[_KT_co, _VT_co] | _T]: ...
@@ -720,7 +744,7 @@ class ItemsView(MappingView, AbstractSet[tuple[_KT_co, _VT_co]], Generic[_KT_co,
     def __rxor__(self, other: Iterable[_T]) -> set[tuple[_KT_co, _VT_co] | _T]: ...
 
 class KeysView(MappingView, AbstractSet[_KT_co]):
-    def __init__(self, mapping: Mapping[_KT_co, Any]) -> None: ...  # undocumented
+    def __init__(self, mapping: Viewable[_KT_co]) -> None: ...  # undocumented
     def __and__(self, other: Iterable[Any]) -> set[_KT_co]: ...
     def __rand__(self, other: Iterable[_T]) -> set[_T]: ...
     def __contains__(self, key: object) -> bool: ...
@@ -733,7 +757,7 @@ class KeysView(MappingView, AbstractSet[_KT_co]):
     def __rxor__(self, other: Iterable[_T]) -> set[_KT_co | _T]: ...
 
 class ValuesView(MappingView, Collection[_VT_co]):
-    def __init__(self, mapping: Mapping[Any, _VT_co]) -> None: ...  # undocumented
+    def __init__(self, mapping: SupportsGetItemViewable[Any, _VT_co]) -> None: ...  # undocumented
     def __contains__(self, value: object) -> bool: ...
     def __iter__(self) -> Iterator[_VT_co]: ...
 
@@ -746,7 +770,9 @@ class Mapping(Collection[_KT], Generic[_KT, _VT_co]):
     @overload
     def get(self, key: _KT, /) -> _VT_co | None: ...
     @overload
-    def get(self, key: _KT, /, default: _VT_co | _T) -> _VT_co | _T: ...
+    def get(self, key: _KT, /, default: _VT_co) -> _VT_co: ...  # type: ignore[misc] # pyright: ignore[reportGeneralTypeIssues] # Covariant type as parameter
+    @overload
+    def get(self, key: _KT, /, default: _T) -> _VT_co | _T: ...
     def items(self) -> ItemsView[_KT, _VT_co]: ...
     def keys(self) -> KeysView[_KT]: ...
     def values(self) -> ValuesView[_VT_co]: ...
@@ -799,13 +825,13 @@ class MutableMapping(Mapping[_KT, _VT]):
     @overload
     def update(self, m: SupportsKeysAndGetItem[_KT, _VT], /) -> None: ...
     @overload
-    def update(self: Mapping[str, _VT], m: SupportsKeysAndGetItem[str, _VT], /, **kwargs: _VT) -> None: ...
+    def update(self: SupportsGetItem[str, _VT], m: SupportsKeysAndGetItem[str, _VT], /, **kwargs: _VT) -> None: ...
     @overload
     def update(self, m: Iterable[tuple[_KT, _VT]], /) -> None: ...
     @overload
-    def update(self: Mapping[str, _VT], m: Iterable[tuple[str, _VT]], /, **kwargs: _VT) -> None: ...
+    def update(self: SupportsGetItem[str, _VT], m: Iterable[tuple[str, _VT]], /, **kwargs: _VT) -> None: ...
     @overload
-    def update(self: Mapping[str, _VT], **kwargs: _VT) -> None: ...
+    def update(self: SupportsGetItem[str, _VT], **kwargs: _VT) -> None: ...
 
 Text = str
 
@@ -818,6 +844,7 @@ class IO(Generic[AnyStr]):
     # At runtime these are all abstract properties,
     # but making them abstract in the stub is hugely disruptive, for not much gain.
     # See #8726
+    __slots__ = ()
     @property
     def mode(self) -> str: ...
     # Usually str, but may be bytes if a bytes path was passed to open(). See #10737.
@@ -876,11 +903,13 @@ class IO(Generic[AnyStr]):
     ) -> None: ...
 
 class BinaryIO(IO[bytes]):
+    __slots__ = ()
     @abstractmethod
     def __enter__(self) -> BinaryIO: ...
 
 class TextIO(IO[str]):
     # See comment regarding the @properties in the `IO` class
+    __slots__ = ()
     @property
     def buffer(self) -> BinaryIO: ...
     @property
@@ -1043,6 +1072,15 @@ if sys.version_info >= (3, 14):
 else:
     @final
     class ForwardRef(_Final):
+        __slots__ = (
+            "__forward_arg__",
+            "__forward_code__",
+            "__forward_evaluated__",
+            "__forward_value__",
+            "__forward_is_argument__",
+            "__forward_is_class__",
+            "__forward_module__",
+        )
         __forward_arg__: str
         __forward_code__: CodeType
         __forward_evaluated__: bool
@@ -1113,9 +1151,9 @@ if sys.version_info >= (3, 12):
         # It's writable on types, but not on instances of TypeAliasType.
         @property
         def __module__(self) -> str | None: ...  # type: ignore[override]
-        def __getitem__(self, parameters: Any) -> GenericAlias: ...  # AnnotationForm
-        def __or__(self, right: Any) -> _SpecialForm: ...
-        def __ror__(self, left: Any) -> _SpecialForm: ...
+        def __getitem__(self, parameters: Any, /) -> GenericAlias: ...  # AnnotationForm
+        def __or__(self, right: Any, /) -> _SpecialForm: ...
+        def __ror__(self, left: Any, /) -> _SpecialForm: ...
         if sys.version_info >= (3, 14):
             @property
             def evaluate_value(self) -> EvaluateFunc: ...
@@ -1124,6 +1162,7 @@ if sys.version_info >= (3, 13):
     def is_protocol(tp: type, /) -> bool: ...
     def get_protocol_members(tp: type, /) -> frozenset[str]: ...
     @final
+    @type_check_only
     class _NoDefaultType: ...
 
     NoDefault: _NoDefaultType
diff --git a/mypy/typeshed/stdlib/typing_extensions.pyi b/mypy/typeshed/stdlib/typing_extensions.pyi
index 07cd57ebc18f..f5ea13f67733 100644
--- a/mypy/typeshed/stdlib/typing_extensions.pyi
+++ b/mypy/typeshed/stdlib/typing_extensions.pyi
@@ -59,6 +59,7 @@ from typing import (  # noqa: Y022,Y037,Y038,Y039,UP035
     TypeVar as _TypeVar,
     Union as Union,
     _Alias,
+    _SpecialForm,
     cast as cast,
     no_type_check as no_type_check,
     no_type_check_decorator as no_type_check_decorator,
@@ -119,6 +120,7 @@ __all__ = [
     "clear_overloads",
     "dataclass_transform",
     "deprecated",
+    "disjoint_base",
     "Doc",
     "evaluate_forward_ref",
     "get_overloads",
@@ -149,6 +151,7 @@ __all__ = [
     "TypeGuard",
     "TypeIs",
     "TYPE_CHECKING",
+    "type_repr",
     "Never",
     "NoReturn",
     "ReadOnly",
@@ -204,15 +207,6 @@ _TC = _TypeVar("_TC", bound=type[object])
 _T_co = _TypeVar("_T_co", covariant=True)  # Any type covariant containers.
 _T_contra = _TypeVar("_T_contra", contravariant=True)
 
-class _Final: ...  # This should be imported from typing but that breaks pytype
-
-# unfortunately we have to duplicate this class definition from typing.pyi or we break pytype
-class _SpecialForm(_Final):
-    def __getitem__(self, parameters: Any) -> object: ...
-    if sys.version_info >= (3, 10):
-        def __or__(self, other: Any) -> _SpecialForm: ...
-        def __ror__(self, other: Any) -> _SpecialForm: ...
-
 # Do not import (and re-export) Protocol or runtime_checkable from
 # typing module because type checkers need to be able to distinguish
 # typing.Protocol and typing_extensions.Protocol so they can properly
@@ -227,6 +221,7 @@ runtime = runtime_checkable
 Final: _SpecialForm
 
 def final(f: _F) -> _F: ...
+def disjoint_base(cls: _TC) -> _TC: ...
 
 Literal: _SpecialForm
 
@@ -413,36 +408,43 @@ else:
 
     @runtime_checkable
     class SupportsInt(Protocol, metaclass=abc.ABCMeta):
+        __slots__ = ()
         @abc.abstractmethod
         def __int__(self) -> int: ...
 
     @runtime_checkable
     class SupportsFloat(Protocol, metaclass=abc.ABCMeta):
+        __slots__ = ()
         @abc.abstractmethod
         def __float__(self) -> float: ...
 
     @runtime_checkable
     class SupportsComplex(Protocol, metaclass=abc.ABCMeta):
+        __slots__ = ()
         @abc.abstractmethod
         def __complex__(self) -> complex: ...
 
     @runtime_checkable
     class SupportsBytes(Protocol, metaclass=abc.ABCMeta):
+        __slots__ = ()
         @abc.abstractmethod
         def __bytes__(self) -> bytes: ...
 
     @runtime_checkable
     class SupportsIndex(Protocol, metaclass=abc.ABCMeta):
+        __slots__ = ()
         @abc.abstractmethod
         def __index__(self) -> int: ...
 
     @runtime_checkable
     class SupportsAbs(Protocol[_T_co]):
+        __slots__ = ()
         @abc.abstractmethod
         def __abs__(self) -> _T_co: ...
 
     @runtime_checkable
     class SupportsRound(Protocol[_T_co]):
+        __slots__ = ()
         @overload
         @abc.abstractmethod
         def __round__(self) -> int: ...
@@ -455,11 +457,13 @@ if sys.version_info >= (3, 14):
 else:
     @runtime_checkable
     class Reader(Protocol[_T_co]):
+        __slots__ = ()
         @abc.abstractmethod
         def read(self, size: int = ..., /) -> _T_co: ...
 
     @runtime_checkable
     class Writer(Protocol[_T_contra]):
+        __slots__ = ()
         @abc.abstractmethod
         def write(self, data: _T_contra, /) -> int: ...
 
@@ -480,6 +484,7 @@ else:
     def is_protocol(tp: type, /) -> bool: ...
     def get_protocol_members(tp: type, /) -> frozenset[str]: ...
     @final
+    @type_check_only
     class _NoDefaultType: ...
 
     NoDefault: _NoDefaultType
@@ -600,8 +605,8 @@ else:
         def __getitem__(self, parameters: Incomplete | tuple[Incomplete, ...]) -> AnnotationForm: ...
         def __init_subclass__(cls, *args: Unused, **kwargs: Unused) -> NoReturn: ...
         if sys.version_info >= (3, 10):
-            def __or__(self, right: Any) -> _SpecialForm: ...
-            def __ror__(self, left: Any) -> _SpecialForm: ...
+            def __or__(self, right: Any, /) -> _SpecialForm: ...
+            def __ror__(self, left: Any, /) -> _SpecialForm: ...
 
 # PEP 727
 class Doc:
@@ -611,6 +616,7 @@ class Doc:
     def __eq__(self, other: object) -> bool: ...
 
 # PEP 728
+@type_check_only
 class _NoExtraItemsType: ...
 
 NoExtraItems: _NoExtraItemsType
@@ -622,7 +628,7 @@ TypeForm: _SpecialForm
 if sys.version_info >= (3, 14):
     from typing import evaluate_forward_ref as evaluate_forward_ref
 
-    from annotationlib import Format as Format, get_annotations as get_annotations
+    from annotationlib import Format as Format, get_annotations as get_annotations, type_repr as type_repr
 else:
     class Format(enum.IntEnum):
         VALUE = 1
@@ -690,6 +696,7 @@ else:
         format: Format | None = None,
         _recursive_guard: Container[str] = ...,
     ) -> AnnotationForm: ...
+    def type_repr(value: object) -> str: ...
 
 # PEP 661
 class Sentinel:
@@ -697,6 +704,6 @@ class Sentinel:
     if sys.version_info >= (3, 14):
         def __or__(self, other: Any) -> UnionType: ...  # other can be any type form legal for unions
         def __ror__(self, other: Any) -> UnionType: ...  # other can be any type form legal for unions
-    else:
+    elif sys.version_info >= (3, 10):
         def __or__(self, other: Any) -> _SpecialForm: ...  # other can be any type form legal for unions
         def __ror__(self, other: Any) -> _SpecialForm: ...  # other can be any type form legal for unions
diff --git a/mypy/typeshed/stdlib/unicodedata.pyi b/mypy/typeshed/stdlib/unicodedata.pyi
index 77d69edf06af..9fff042f0b96 100644
--- a/mypy/typeshed/stdlib/unicodedata.pyi
+++ b/mypy/typeshed/stdlib/unicodedata.pyi
@@ -1,10 +1,10 @@
 import sys
 from _typeshed import ReadOnlyBuffer
-from typing import Any, Literal, TypeVar, final, overload
+from typing import Any, Final, Literal, TypeVar, final, overload
 from typing_extensions import TypeAlias
 
 ucd_3_2_0: UCD
-unidata_version: str
+unidata_version: Final[str]
 
 if sys.version_info < (3, 10):
     ucnhash_CAPI: Any
diff --git a/mypy/typeshed/stdlib/unittest/case.pyi b/mypy/typeshed/stdlib/unittest/case.pyi
index 89bcabf104c2..a602196e73c6 100644
--- a/mypy/typeshed/stdlib/unittest/case.pyi
+++ b/mypy/typeshed/stdlib/unittest/case.pyi
@@ -2,18 +2,16 @@ import logging
 import sys
 import unittest.result
 from _typeshed import SupportsDunderGE, SupportsDunderGT, SupportsDunderLE, SupportsDunderLT, SupportsRSub, SupportsSub
+from builtins import _ClassInfo
 from collections.abc import Callable, Container, Iterable, Mapping, Sequence, Set as AbstractSet
 from contextlib import AbstractContextManager
 from re import Pattern
 from types import GenericAlias, TracebackType
-from typing import Any, AnyStr, Final, Generic, NoReturn, Protocol, SupportsAbs, SupportsRound, TypeVar, overload
-from typing_extensions import Never, ParamSpec, Self, TypeAlias
+from typing import Any, AnyStr, Final, Generic, NoReturn, Protocol, SupportsAbs, SupportsRound, TypeVar, overload, type_check_only
+from typing_extensions import Never, ParamSpec, Self
 from unittest._log import _AssertLogsContext, _LoggingWatcher
 from warnings import WarningMessage
 
-if sys.version_info >= (3, 10):
-    from types import UnionType
-
 _T = TypeVar("_T")
 _S = TypeVar("_S", bound=SupportsSub[Any, Any])
 _E = TypeVar("_E", bound=BaseException)
@@ -58,16 +56,9 @@ def skipUnless(condition: object, reason: str) -> Callable[[_FT], _FT]: ...
 class SkipTest(Exception):
     def __init__(self, reason: str) -> None: ...
 
+@type_check_only
 class _SupportsAbsAndDunderGE(SupportsDunderGE[Any], SupportsAbs[Any], Protocol): ...
 
-# Keep this alias in sync with builtins._ClassInfo
-# We can't import it from builtins or pytype crashes,
-# due to the fact that pytype uses a custom builtins stub rather than typeshed's builtins stub
-if sys.version_info >= (3, 10):
-    _ClassInfo: TypeAlias = type | UnionType | tuple[_ClassInfo, ...]
-else:
-    _ClassInfo: TypeAlias = type | tuple[_ClassInfo, ...]
-
 class TestCase:
     failureException: type[BaseException]
     longMessage: bool
diff --git a/mypy/typeshed/stdlib/unittest/loader.pyi b/mypy/typeshed/stdlib/unittest/loader.pyi
index 598e3cd84a5e..81de40c89849 100644
--- a/mypy/typeshed/stdlib/unittest/loader.pyi
+++ b/mypy/typeshed/stdlib/unittest/loader.pyi
@@ -35,21 +35,38 @@ class TestLoader:
 defaultTestLoader: TestLoader
 
 if sys.version_info < (3, 13):
-    @deprecated("Deprecated in Python 3.11; removal scheduled for Python 3.13")
-    def getTestCaseNames(
-        testCaseClass: type[unittest.case.TestCase],
-        prefix: str,
-        sortUsing: _SortComparisonMethod = ...,
-        testNamePatterns: list[str] | None = None,
-    ) -> Sequence[str]: ...
-    @deprecated("Deprecated in Python 3.11; removal scheduled for Python 3.13")
-    def makeSuite(
-        testCaseClass: type[unittest.case.TestCase],
-        prefix: str = "test",
-        sortUsing: _SortComparisonMethod = ...,
-        suiteClass: _SuiteClass = ...,
-    ) -> unittest.suite.TestSuite: ...
-    @deprecated("Deprecated in Python 3.11; removal scheduled for Python 3.13")
-    def findTestCases(
-        module: ModuleType, prefix: str = "test", sortUsing: _SortComparisonMethod = ..., suiteClass: _SuiteClass = ...
-    ) -> unittest.suite.TestSuite: ...
+    if sys.version_info >= (3, 11):
+        @deprecated("Deprecated since Python 3.11; removed in Python 3.13.")
+        def getTestCaseNames(
+            testCaseClass: type[unittest.case.TestCase],
+            prefix: str,
+            sortUsing: _SortComparisonMethod = ...,
+            testNamePatterns: list[str] | None = None,
+        ) -> Sequence[str]: ...
+        @deprecated("Deprecated since Python 3.11; removed in Python 3.13.")
+        def makeSuite(
+            testCaseClass: type[unittest.case.TestCase],
+            prefix: str = "test",
+            sortUsing: _SortComparisonMethod = ...,
+            suiteClass: _SuiteClass = ...,
+        ) -> unittest.suite.TestSuite: ...
+        @deprecated("Deprecated since Python 3.11; removed in Python 3.13.")
+        def findTestCases(
+            module: ModuleType, prefix: str = "test", sortUsing: _SortComparisonMethod = ..., suiteClass: _SuiteClass = ...
+        ) -> unittest.suite.TestSuite: ...
+    else:
+        def getTestCaseNames(
+            testCaseClass: type[unittest.case.TestCase],
+            prefix: str,
+            sortUsing: _SortComparisonMethod = ...,
+            testNamePatterns: list[str] | None = None,
+        ) -> Sequence[str]: ...
+        def makeSuite(
+            testCaseClass: type[unittest.case.TestCase],
+            prefix: str = "test",
+            sortUsing: _SortComparisonMethod = ...,
+            suiteClass: _SuiteClass = ...,
+        ) -> unittest.suite.TestSuite: ...
+        def findTestCases(
+            module: ModuleType, prefix: str = "test", sortUsing: _SortComparisonMethod = ..., suiteClass: _SuiteClass = ...
+        ) -> unittest.suite.TestSuite: ...
diff --git a/mypy/typeshed/stdlib/unittest/main.pyi b/mypy/typeshed/stdlib/unittest/main.pyi
index 22f2ec10634d..23ead1638ecc 100644
--- a/mypy/typeshed/stdlib/unittest/main.pyi
+++ b/mypy/typeshed/stdlib/unittest/main.pyi
@@ -5,12 +5,13 @@ import unittest.result
 import unittest.suite
 from collections.abc import Iterable
 from types import ModuleType
-from typing import Any, Final, Protocol
+from typing import Any, Final, Protocol, type_check_only
 from typing_extensions import deprecated
 
 MAIN_EXAMPLES: Final[str]
 MODULE_EXAMPLES: Final[str]
 
+@type_check_only
 class _TestRunner(Protocol):
     def run(self, test: unittest.suite.TestSuite | unittest.case.TestCase, /) -> unittest.result.TestResult: ...
 
@@ -63,8 +64,11 @@ class TestProgram:
         ) -> None: ...
 
     if sys.version_info < (3, 13):
-        @deprecated("Deprecated in Python 3.11; removal scheduled for Python 3.13")
-        def usageExit(self, msg: Any = None) -> None: ...
+        if sys.version_info >= (3, 11):
+            @deprecated("Deprecated since Python 3.11; removed in Python 3.13.")
+            def usageExit(self, msg: Any = None) -> None: ...
+        else:
+            def usageExit(self, msg: Any = None) -> None: ...
 
     def parseArgs(self, argv: list[str]) -> None: ...
     def createTests(self, from_discovery: bool = False, Loader: unittest.loader.TestLoader | None = None) -> None: ...
diff --git a/mypy/typeshed/stdlib/unittest/mock.pyi b/mypy/typeshed/stdlib/unittest/mock.pyi
index 9e353900f2d7..f3e58bcd1c00 100644
--- a/mypy/typeshed/stdlib/unittest/mock.pyi
+++ b/mypy/typeshed/stdlib/unittest/mock.pyi
@@ -3,8 +3,8 @@ from _typeshed import MaybeNone
 from collections.abc import Awaitable, Callable, Coroutine, Iterable, Mapping, Sequence
 from contextlib import _GeneratorContextManager
 from types import TracebackType
-from typing import Any, ClassVar, Final, Generic, Literal, TypeVar, overload
-from typing_extensions import ParamSpec, Self, TypeAlias
+from typing import Any, ClassVar, Final, Generic, Literal, TypeVar, overload, type_check_only
+from typing_extensions import ParamSpec, Self, TypeAlias, disjoint_base
 
 _T = TypeVar("_T")
 _TT = TypeVar("_TT", bound=type[Any])
@@ -52,7 +52,7 @@ else:
         "seal",
     )
 
-FILTER_DIR: Any
+FILTER_DIR: bool  # controls the way mock objects respond to `dir` function
 
 class _SentinelObject:
     name: Any
@@ -61,36 +61,73 @@ class _SentinelObject:
 class _Sentinel:
     def __getattr__(self, name: str) -> Any: ...
 
-sentinel: Any
+sentinel: _Sentinel
 DEFAULT: Any
 
 _ArgsKwargs: TypeAlias = tuple[tuple[Any, ...], Mapping[str, Any]]
 _NameArgsKwargs: TypeAlias = tuple[str, tuple[Any, ...], Mapping[str, Any]]
 _CallValue: TypeAlias = str | tuple[Any, ...] | Mapping[str, Any] | _ArgsKwargs | _NameArgsKwargs
 
-class _Call(tuple[Any, ...]):
-    def __new__(
-        cls, value: _CallValue = (), name: str | None = "", parent: _Call | None = None, two: bool = False, from_kall: bool = True
-    ) -> Self: ...
-    def __init__(
-        self,
-        value: _CallValue = (),
-        name: str | None = None,
-        parent: _Call | None = None,
-        two: bool = False,
-        from_kall: bool = True,
-    ) -> None: ...
-    __hash__: ClassVar[None]  # type: ignore[assignment]
-    def __eq__(self, other: object) -> bool: ...
-    def __ne__(self, value: object, /) -> bool: ...
-    def __call__(self, *args: Any, **kwargs: Any) -> _Call: ...
-    def __getattr__(self, attr: str) -> Any: ...
-    def __getattribute__(self, attr: str) -> Any: ...
-    @property
-    def args(self) -> tuple[Any, ...]: ...
-    @property
-    def kwargs(self) -> Mapping[str, Any]: ...
-    def call_list(self) -> Any: ...
+if sys.version_info >= (3, 12):
+    class _Call(tuple[Any, ...]):
+        def __new__(
+            cls,
+            value: _CallValue = (),
+            name: str | None = "",
+            parent: _Call | None = None,
+            two: bool = False,
+            from_kall: bool = True,
+        ) -> Self: ...
+        def __init__(
+            self,
+            value: _CallValue = (),
+            name: str | None = None,
+            parent: _Call | None = None,
+            two: bool = False,
+            from_kall: bool = True,
+        ) -> None: ...
+        __hash__: ClassVar[None]  # type: ignore[assignment]
+        def __eq__(self, other: object) -> bool: ...
+        def __ne__(self, value: object, /) -> bool: ...
+        def __call__(self, *args: Any, **kwargs: Any) -> _Call: ...
+        def __getattr__(self, attr: str) -> Any: ...
+        def __getattribute__(self, attr: str) -> Any: ...
+        @property
+        def args(self) -> tuple[Any, ...]: ...
+        @property
+        def kwargs(self) -> Mapping[str, Any]: ...
+        def call_list(self) -> Any: ...
+
+else:
+    @disjoint_base
+    class _Call(tuple[Any, ...]):
+        def __new__(
+            cls,
+            value: _CallValue = (),
+            name: str | None = "",
+            parent: _Call | None = None,
+            two: bool = False,
+            from_kall: bool = True,
+        ) -> Self: ...
+        def __init__(
+            self,
+            value: _CallValue = (),
+            name: str | None = None,
+            parent: _Call | None = None,
+            two: bool = False,
+            from_kall: bool = True,
+        ) -> None: ...
+        __hash__: ClassVar[None]  # type: ignore[assignment]
+        def __eq__(self, other: object) -> bool: ...
+        def __ne__(self, value: object, /) -> bool: ...
+        def __call__(self, *args: Any, **kwargs: Any) -> _Call: ...
+        def __getattr__(self, attr: str) -> Any: ...
+        def __getattribute__(self, attr: str) -> Any: ...
+        @property
+        def args(self) -> tuple[Any, ...]: ...
+        @property
+        def kwargs(self) -> Mapping[str, Any]: ...
+        def call_list(self) -> Any: ...
 
 call: _Call
 
@@ -262,7 +299,8 @@ class _patch(Generic[_T]):
 # This class does not exist at runtime, it's a hack to make this work:
 #     @patch("foo")
 #     def bar(..., mock: MagicMock) -> None: ...
-class _patch_default_new(_patch[MagicMock | AsyncMock]):
+@type_check_only
+class _patch_pass_arg(_patch[_T]):
     @overload
     def __call__(self, func: _TT) -> _TT: ...
     # Can't use the following as ParamSpec is only allowed as last parameter:
@@ -288,6 +326,7 @@ class _patch_dict:
 
 # This class does not exist at runtime, it's a hack to add methods to the
 # patch() function.
+@type_check_only
 class _patcher:
     TEST_PREFIX: str
     dict: type[_patch_dict]
@@ -295,41 +334,64 @@ class _patcher:
     # Ideally we'd be able to add an overload for it so that the return type is _patch[MagicMock],
     # but that's impossible with the current type system.
     @overload
-    def __call__(
+    def __call__(  # type: ignore[overload-overlap]
         self,
         target: str,
         new: _T,
-        spec: Any | None = ...,
-        create: bool = ...,
-        spec_set: Any | None = ...,
-        autospec: Any | None = ...,
-        new_callable: Any | None = ...,
-        **kwargs: Any,
+        spec: Literal[False] | None = None,
+        create: bool = False,
+        spec_set: Literal[False] | None = None,
+        autospec: Literal[False] | None = None,
+        new_callable: None = None,
+        *,
+        unsafe: bool = False,
     ) -> _patch[_T]: ...
     @overload
     def __call__(
         self,
         target: str,
         *,
-        spec: Any | None = ...,
-        create: bool = ...,
-        spec_set: Any | None = ...,
-        autospec: Any | None = ...,
-        new_callable: Any | None = ...,
+        # If not False or None, this is passed to new_callable
+        spec: Any | Literal[False] | None = None,
+        create: bool = False,
+        # If not False or None, this is passed to new_callable
+        spec_set: Any | Literal[False] | None = None,
+        autospec: Literal[False] | None = None,
+        new_callable: Callable[..., _T],
+        unsafe: bool = False,
+        # kwargs are passed to new_callable
         **kwargs: Any,
-    ) -> _patch_default_new: ...
+    ) -> _patch_pass_arg[_T]: ...
+    @overload
+    def __call__(
+        self,
+        target: str,
+        *,
+        spec: Any | bool | None = None,
+        create: bool = False,
+        spec_set: Any | bool | None = None,
+        autospec: Any | bool | None = None,
+        new_callable: None = None,
+        unsafe: bool = False,
+        # kwargs are passed to the MagicMock/AsyncMock constructor
+        **kwargs: Any,
+    ) -> _patch_pass_arg[MagicMock | AsyncMock]: ...
+    # This overload also covers the case, where new==DEFAULT. In this case, the return type is _patch[Any].
+    # Ideally we'd be able to add an overload for it so that the return type is _patch[MagicMock],
+    # but that's impossible with the current type system.
     @overload
     @staticmethod
     def object(
         target: Any,
         attribute: str,
         new: _T,
-        spec: Any | None = ...,
-        create: bool = ...,
-        spec_set: Any | None = ...,
-        autospec: Any | None = ...,
-        new_callable: Any | None = ...,
-        **kwargs: Any,
+        spec: Literal[False] | None = None,
+        create: bool = False,
+        spec_set: Literal[False] | None = None,
+        autospec: Literal[False] | None = None,
+        new_callable: None = None,
+        *,
+        unsafe: bool = False,
     ) -> _patch[_T]: ...
     @overload
     @staticmethod
@@ -337,21 +399,71 @@ class _patcher:
         target: Any,
         attribute: str,
         *,
-        spec: Any | None = ...,
-        create: bool = ...,
-        spec_set: Any | None = ...,
-        autospec: Any | None = ...,
-        new_callable: Any | None = ...,
+        # If not False or None, this is passed to new_callable
+        spec: Any | Literal[False] | None = None,
+        create: bool = False,
+        # If not False or None, this is passed to new_callable
+        spec_set: Any | Literal[False] | None = None,
+        autospec: Literal[False] | None = None,
+        new_callable: Callable[..., _T],
+        unsafe: bool = False,
+        # kwargs are passed to new_callable
         **kwargs: Any,
-    ) -> _patch[MagicMock | AsyncMock]: ...
+    ) -> _patch_pass_arg[_T]: ...
+    @overload
     @staticmethod
-    def multiple(
+    def object(
         target: Any,
-        spec: Any | None = ...,
-        create: bool = ...,
-        spec_set: Any | None = ...,
-        autospec: Any | None = ...,
-        new_callable: Any | None = ...,
+        attribute: str,
+        *,
+        spec: Any | bool | None = None,
+        create: bool = False,
+        spec_set: Any | bool | None = None,
+        autospec: Any | bool | None = None,
+        new_callable: None = None,
+        unsafe: bool = False,
+        # kwargs are passed to the MagicMock/AsyncMock constructor
+        **kwargs: Any,
+    ) -> _patch_pass_arg[MagicMock | AsyncMock]: ...
+    @overload
+    @staticmethod
+    def multiple(
+        target: Any | str,
+        # If not False or None, this is passed to new_callable
+        spec: Any | Literal[False] | None = None,
+        create: bool = False,
+        # If not False or None, this is passed to new_callable
+        spec_set: Any | Literal[False] | None = None,
+        autospec: Literal[False] | None = None,
+        *,
+        new_callable: Callable[..., _T],
+        # The kwargs must be DEFAULT
+        **kwargs: Any,
+    ) -> _patch_pass_arg[_T]: ...
+    @overload
+    @staticmethod
+    def multiple(
+        target: Any | str,
+        # If not False or None, this is passed to new_callable
+        spec: Any | Literal[False] | None,
+        create: bool,
+        # If not False or None, this is passed to new_callable
+        spec_set: Any | Literal[False] | None,
+        autospec: Literal[False] | None,
+        new_callable: Callable[..., _T],
+        # The kwargs must be DEFAULT
+        **kwargs: Any,
+    ) -> _patch_pass_arg[_T]: ...
+    @overload
+    @staticmethod
+    def multiple(
+        target: Any | str,
+        spec: Any | bool | None = None,
+        create: bool = False,
+        spec_set: Any | bool | None = None,
+        autospec: Any | bool | None = None,
+        new_callable: None = None,
+        # The kwargs are the mock objects or DEFAULT
         **kwargs: Any,
     ) -> _patch[Any]: ...
     @staticmethod
@@ -396,12 +508,13 @@ class MagicProxy(Base):
     def create_mock(self) -> Any: ...
     def __get__(self, obj: Any, _type: Any | None = None) -> Any: ...
 
-class _ANY:
+# See https://github.com/python/typeshed/issues/14701
+class _ANY(Any):
     def __eq__(self, other: object) -> Literal[True]: ...
     def __ne__(self, other: object) -> Literal[False]: ...
     __hash__: ClassVar[None]  # type: ignore[assignment]
 
-ANY: Any
+ANY: _ANY
 
 if sys.version_info >= (3, 10):
     def create_autospec(
diff --git a/mypy/typeshed/stdlib/unittest/runner.pyi b/mypy/typeshed/stdlib/unittest/runner.pyi
index 783764464a53..f76771f55e13 100644
--- a/mypy/typeshed/stdlib/unittest/runner.pyi
+++ b/mypy/typeshed/stdlib/unittest/runner.pyi
@@ -4,15 +4,17 @@ import unittest.result
 import unittest.suite
 from _typeshed import SupportsFlush, SupportsWrite
 from collections.abc import Callable, Iterable
-from typing import Any, Generic, Protocol, TypeVar
+from typing import Any, Generic, Protocol, TypeVar, type_check_only
 from typing_extensions import Never, TypeAlias
 from warnings import _ActionKind
 
 _ResultClassType: TypeAlias = Callable[[_TextTestStream, bool, int], TextTestResult[Any]]
 
+@type_check_only
 class _SupportsWriteAndFlush(SupportsWrite[str], SupportsFlush, Protocol): ...
 
 # All methods used by unittest.runner.TextTestResult's stream
+@type_check_only
 class _TextTestStream(_SupportsWriteAndFlush, Protocol):
     def writeln(self, arg: str | None = None, /) -> None: ...
 
diff --git a/mypy/typeshed/stdlib/unittest/util.pyi b/mypy/typeshed/stdlib/unittest/util.pyi
index 945b0cecfed0..31c830e8268a 100644
--- a/mypy/typeshed/stdlib/unittest/util.pyi
+++ b/mypy/typeshed/stdlib/unittest/util.pyi
@@ -5,12 +5,12 @@ from typing_extensions import TypeAlias
 _T = TypeVar("_T")
 _Mismatch: TypeAlias = tuple[_T, _T, int]
 
-_MAX_LENGTH: Final[int]
-_PLACEHOLDER_LEN: Final[int]
-_MIN_BEGIN_LEN: Final[int]
-_MIN_END_LEN: Final[int]
-_MIN_COMMON_LEN: Final[int]
-_MIN_DIFF_LEN: Final[int]
+_MAX_LENGTH: Final = 80
+_PLACEHOLDER_LEN: Final = 12
+_MIN_BEGIN_LEN: Final = 5
+_MIN_END_LEN: Final = 5
+_MIN_COMMON_LEN: Final = 5
+_MIN_DIFF_LEN: Final = 41
 
 def _shorten(s: str, prefixlen: int, suffixlen: int) -> str: ...
 def _common_shorten_repr(*args: str) -> tuple[str, ...]: ...
diff --git a/mypy/typeshed/stdlib/urllib/error.pyi b/mypy/typeshed/stdlib/urllib/error.pyi
index 89cec9bf289c..2173d7e6efaa 100644
--- a/mypy/typeshed/stdlib/urllib/error.pyi
+++ b/mypy/typeshed/stdlib/urllib/error.pyi
@@ -6,6 +6,8 @@ __all__ = ["URLError", "HTTPError", "ContentTooShortError"]
 
 class URLError(OSError):
     reason: str | BaseException
+    # The `filename` attribute only exists if it was provided to `__init__` and wasn't `None`.
+    filename: str
     def __init__(self, reason: str | BaseException, filename: str | None = None) -> None: ...
 
 class HTTPError(URLError, addinfourl):
@@ -16,6 +18,9 @@ class HTTPError(URLError, addinfourl):
     @property
     def reason(self) -> str: ...  # type: ignore[override]
     code: int
+    msg: str
+    hdrs: Message
+    fp: IO[bytes]
     def __init__(self, url: str, code: int, msg: str, hdrs: Message, fp: IO[bytes] | None) -> None: ...
 
 class ContentTooShortError(URLError):
diff --git a/mypy/typeshed/stdlib/urllib/parse.pyi b/mypy/typeshed/stdlib/urllib/parse.pyi
index a5ed616d25af..364892ecdf69 100644
--- a/mypy/typeshed/stdlib/urllib/parse.pyi
+++ b/mypy/typeshed/stdlib/urllib/parse.pyi
@@ -1,7 +1,7 @@
 import sys
 from collections.abc import Iterable, Mapping, Sequence
 from types import GenericAlias
-from typing import Any, AnyStr, Generic, Literal, NamedTuple, Protocol, overload, type_check_only
+from typing import Any, AnyStr, Final, Generic, Literal, NamedTuple, Protocol, overload, type_check_only
 from typing_extensions import TypeAlias
 
 __all__ = [
@@ -28,23 +28,26 @@ __all__ = [
     "SplitResultBytes",
 ]
 
-uses_relative: list[str]
-uses_netloc: list[str]
-uses_params: list[str]
-non_hierarchical: list[str]
-uses_query: list[str]
-uses_fragment: list[str]
-scheme_chars: str
+uses_relative: Final[list[str]]
+uses_netloc: Final[list[str]]
+uses_params: Final[list[str]]
+non_hierarchical: Final[list[str]]
+uses_query: Final[list[str]]
+uses_fragment: Final[list[str]]
+scheme_chars: Final[str]
 if sys.version_info < (3, 11):
-    MAX_CACHE_SIZE: int
+    MAX_CACHE_SIZE: Final[int]
 
 class _ResultMixinStr:
+    __slots__ = ()
     def encode(self, encoding: str = "ascii", errors: str = "strict") -> _ResultMixinBytes: ...
 
 class _ResultMixinBytes:
+    __slots__ = ()
     def decode(self, encoding: str = "ascii", errors: str = "strict") -> _ResultMixinStr: ...
 
 class _NetlocResultMixinBase(Generic[AnyStr]):
+    __slots__ = ()
     @property
     def username(self) -> AnyStr | None: ...
     @property
@@ -55,8 +58,11 @@ class _NetlocResultMixinBase(Generic[AnyStr]):
     def port(self) -> int | None: ...
     def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
-class _NetlocResultMixinStr(_NetlocResultMixinBase[str], _ResultMixinStr): ...
-class _NetlocResultMixinBytes(_NetlocResultMixinBase[bytes], _ResultMixinBytes): ...
+class _NetlocResultMixinStr(_NetlocResultMixinBase[str], _ResultMixinStr):
+    __slots__ = ()
+
+class _NetlocResultMixinBytes(_NetlocResultMixinBase[bytes], _ResultMixinBytes):
+    __slots__ = ()
 
 class _DefragResultBase(NamedTuple, Generic[AnyStr]):
     url: AnyStr
diff --git a/mypy/typeshed/stdlib/urllib/request.pyi b/mypy/typeshed/stdlib/urllib/request.pyi
index d8fc5e0d8f48..876b9d3f165c 100644
--- a/mypy/typeshed/stdlib/urllib/request.pyi
+++ b/mypy/typeshed/stdlib/urllib/request.pyi
@@ -6,7 +6,7 @@ from email.message import Message
 from http.client import HTTPConnection, HTTPMessage, HTTPResponse
 from http.cookiejar import CookieJar
 from re import Pattern
-from typing import IO, Any, ClassVar, NoReturn, Protocol, TypeVar, overload
+from typing import IO, Any, ClassVar, NoReturn, Protocol, TypeVar, overload, type_check_only
 from typing_extensions import TypeAlias, deprecated
 from urllib.error import HTTPError as HTTPError
 from urllib.response import addclosehook, addinfourl
@@ -237,6 +237,7 @@ class ProxyDigestAuthHandler(BaseHandler, AbstractDigestAuthHandler):
     auth_header: ClassVar[str]  # undocumented
     def http_error_407(self, req: Request, fp: IO[bytes], code: int, msg: str, headers: HTTPMessage) -> _UrlopenRet | None: ...
 
+@type_check_only
 class _HTTPConnectionProtocol(Protocol):
     def __call__(
         self,
@@ -324,7 +325,7 @@ def urlretrieve(
 def urlcleanup() -> None: ...
 
 if sys.version_info < (3, 14):
-    @deprecated("Deprecated since Python 3.3; Removed in 3.14; Use newer urlopen functions and methods.")
+    @deprecated("Deprecated since Python 3.3; removed in Python 3.14. Use newer `urlopen` functions and methods.")
     class URLopener:
         version: ClassVar[str]
         def __init__(self, proxies: dict[str, str] | None = None, **x509: str) -> None: ...
@@ -355,7 +356,7 @@ if sys.version_info < (3, 14):
         def open_unknown_proxy(self, proxy: str, fullurl: str, data: ReadableBuffer | None = None) -> None: ...  # undocumented
         def __del__(self) -> None: ...
 
-    @deprecated("Deprecated since Python 3.3; Removed in 3.14; Use newer urlopen functions and methods.")
+    @deprecated("Deprecated since Python 3.3; removed in Python 3.14. Use newer `urlopen` functions and methods.")
     class FancyURLopener(URLopener):
         def prompt_user_passwd(self, host: str, realm: str) -> tuple[str, str]: ...
         def get_user_passwd(self, host: str, realm: str, clear_cache: int = 0) -> tuple[str, str]: ...  # undocumented
diff --git a/mypy/typeshed/stdlib/uuid.pyi b/mypy/typeshed/stdlib/uuid.pyi
index 99ac6eb223ef..303fb10eaf53 100644
--- a/mypy/typeshed/stdlib/uuid.pyi
+++ b/mypy/typeshed/stdlib/uuid.pyi
@@ -12,6 +12,7 @@ class SafeUUID(Enum):
     unknown = None
 
 class UUID:
+    __slots__ = ("int", "is_safe", "__weakref__")
     def __init__(
         self,
         hex: str | None = None,
@@ -21,7 +22,7 @@ class UUID:
         int: builtins.int | None = None,
         version: builtins.int | None = None,
         *,
-        is_safe: SafeUUID = ...,
+        is_safe: SafeUUID = SafeUUID.unknown,
     ) -> None: ...
     @property
     def is_safe(self) -> SafeUUID: ...
diff --git a/mypy/typeshed/stdlib/venv/__init__.pyi b/mypy/typeshed/stdlib/venv/__init__.pyi
index 0f71f0e073f5..14db88523dba 100644
--- a/mypy/typeshed/stdlib/venv/__init__.pyi
+++ b/mypy/typeshed/stdlib/venv/__init__.pyi
@@ -3,10 +3,11 @@ import sys
 from _typeshed import StrOrBytesPath
 from collections.abc import Iterable, Sequence
 from types import SimpleNamespace
+from typing import Final
 
 logger: logging.Logger
 
-CORE_VENV_DEPS: tuple[str, ...]
+CORE_VENV_DEPS: Final[tuple[str, ...]]
 
 class EnvBuilder:
     system_site_packages: bool
diff --git a/mypy/typeshed/stdlib/wave.pyi b/mypy/typeshed/stdlib/wave.pyi
index ddc6f6bd02a5..fd7dbfade884 100644
--- a/mypy/typeshed/stdlib/wave.pyi
+++ b/mypy/typeshed/stdlib/wave.pyi
@@ -1,3 +1,4 @@
+import sys
 from _typeshed import ReadableBuffer, Unused
 from typing import IO, Any, BinaryIO, Final, Literal, NamedTuple, NoReturn, overload
 from typing_extensions import Self, TypeAlias, deprecated
@@ -8,7 +9,7 @@ _File: TypeAlias = str | IO[bytes]
 
 class Error(Exception): ...
 
-WAVE_FORMAT_PCM: Final = 1
+WAVE_FORMAT_PCM: Final = 0x0001
 
 class _wave_params(NamedTuple):
     nchannels: int
@@ -34,10 +35,15 @@ class Wave_read:
     def getcomptype(self) -> str: ...
     def getcompname(self) -> str: ...
     def getparams(self) -> _wave_params: ...
-    @deprecated("Deprecated in Python 3.13; removal scheduled for Python 3.15")
-    def getmarkers(self) -> None: ...
-    @deprecated("Deprecated in Python 3.13; removal scheduled for Python 3.15")
-    def getmark(self, id: Any) -> NoReturn: ...
+    if sys.version_info >= (3, 13):
+        @deprecated("Deprecated since Python 3.13; will be removed in Python 3.15.")
+        def getmarkers(self) -> None: ...
+        @deprecated("Deprecated since Python 3.13; will be removed in Python 3.15.")
+        def getmark(self, id: Any) -> NoReturn: ...
+    else:
+        def getmarkers(self) -> None: ...
+        def getmark(self, id: Any) -> NoReturn: ...
+
     def setpos(self, pos: int) -> None: ...
     def readframes(self, nframes: int) -> bytes: ...
 
@@ -59,12 +65,18 @@ class Wave_write:
     def getcompname(self) -> str: ...
     def setparams(self, params: _wave_params | tuple[int, int, int, int, str, str]) -> None: ...
     def getparams(self) -> _wave_params: ...
-    @deprecated("Deprecated in Python 3.13; removal scheduled for Python 3.15")
-    def setmark(self, id: Any, pos: Any, name: Any) -> NoReturn: ...
-    @deprecated("Deprecated in Python 3.13; removal scheduled for Python 3.15")
-    def getmark(self, id: Any) -> NoReturn: ...
-    @deprecated("Deprecated in Python 3.13; removal scheduled for Python 3.15")
-    def getmarkers(self) -> None: ...
+    if sys.version_info >= (3, 13):
+        @deprecated("Deprecated since Python 3.13; will be removed in Python 3.15.")
+        def setmark(self, id: Any, pos: Any, name: Any) -> NoReturn: ...
+        @deprecated("Deprecated since Python 3.13; will be removed in Python 3.15.")
+        def getmark(self, id: Any) -> NoReturn: ...
+        @deprecated("Deprecated since Python 3.13; will be removed in Python 3.15.")
+        def getmarkers(self) -> None: ...
+    else:
+        def setmark(self, id: Any, pos: Any, name: Any) -> NoReturn: ...
+        def getmark(self, id: Any) -> NoReturn: ...
+        def getmarkers(self) -> None: ...
+
     def tell(self) -> int: ...
     def writeframesraw(self, data: ReadableBuffer) -> None: ...
     def writeframes(self, data: ReadableBuffer) -> None: ...
diff --git a/mypy/typeshed/stdlib/weakref.pyi b/mypy/typeshed/stdlib/weakref.pyi
index 593eb4615c8f..76ab86b957a1 100644
--- a/mypy/typeshed/stdlib/weakref.pyi
+++ b/mypy/typeshed/stdlib/weakref.pyi
@@ -4,7 +4,7 @@ from _weakrefset import WeakSet as WeakSet
 from collections.abc import Callable, Iterable, Iterator, Mapping, MutableMapping
 from types import GenericAlias
 from typing import Any, ClassVar, Generic, TypeVar, final, overload
-from typing_extensions import ParamSpec, Self
+from typing_extensions import ParamSpec, Self, disjoint_base
 
 __all__ = [
     "ref",
@@ -52,6 +52,7 @@ class ProxyType(Generic[_T]):  # "weakproxy"
     def __getattr__(self, attr: str) -> Any: ...
     __hash__: ClassVar[None]  # type: ignore[assignment]
 
+@disjoint_base
 class ReferenceType(Generic[_T]):  # "weakref"
     __callback__: Callable[[Self], Any]
     def __new__(cls, o: _T, callback: Callable[[Self], Any] | None = ..., /) -> Self: ...
@@ -65,6 +66,7 @@ ref = ReferenceType
 # everything below here is implemented in weakref.py
 
 class WeakMethod(ref[_CallableT]):
+    __slots__ = ("_func_ref", "_meth_type", "_alive", "__weakref__")
     def __new__(cls, meth: _CallableT, callback: Callable[[Self], Any] | None = None) -> Self: ...
     def __call__(self) -> _CallableT | None: ...
     def __eq__(self, other: object) -> bool: ...
@@ -99,6 +101,8 @@ class WeakValueDictionary(MutableMapping[_KT, _VT]):
     @overload
     def get(self, key: _KT, default: None = None) -> _VT | None: ...
     @overload
+    def get(self, key: _KT, default: _VT) -> _VT: ...
+    @overload
     def get(self, key: _KT, default: _T) -> _VT | _T: ...
     # These are incompatible with Mapping
     def keys(self) -> Iterator[_KT]: ...  # type: ignore[override]
@@ -128,6 +132,7 @@ class WeakValueDictionary(MutableMapping[_KT, _VT]):
     def __ior__(self, other: Iterable[tuple[_KT, _VT]]) -> Self: ...
 
 class KeyedRef(ref[_T], Generic[_KT, _T]):
+    __slots__ = ("key",)
     key: _KT
     def __new__(type, ob: _T, callback: Callable[[Self], Any], key: _KT) -> Self: ...
     def __init__(self, ob: _T, callback: Callable[[Self], Any], key: _KT) -> None: ...
@@ -149,6 +154,8 @@ class WeakKeyDictionary(MutableMapping[_KT, _VT]):
     @overload
     def get(self, key: _KT, default: None = None) -> _VT | None: ...
     @overload
+    def get(self, key: _KT, default: _VT) -> _VT: ...
+    @overload
     def get(self, key: _KT, default: _T) -> _VT | _T: ...
     # These are incompatible with Mapping
     def keys(self) -> Iterator[_KT]: ...  # type: ignore[override]
@@ -181,6 +188,7 @@ class WeakKeyDictionary(MutableMapping[_KT, _VT]):
     def __ior__(self, other: Iterable[tuple[_KT, _VT]]) -> Self: ...
 
 class finalize(Generic[_P, _T]):
+    __slots__ = ()
     def __init__(self, obj: _T, func: Callable[_P, Any], /, *args: _P.args, **kwargs: _P.kwargs) -> None: ...
     def __call__(self, _: Any = None) -> Any | None: ...
     def detach(self) -> tuple[_T, Callable[_P, Any], tuple[Any, ...], dict[str, Any]] | None: ...
diff --git a/mypy/typeshed/stdlib/webbrowser.pyi b/mypy/typeshed/stdlib/webbrowser.pyi
index 773786c24821..56c30f872727 100644
--- a/mypy/typeshed/stdlib/webbrowser.pyi
+++ b/mypy/typeshed/stdlib/webbrowser.pyi
@@ -64,10 +64,16 @@ if sys.platform == "win32":
 
 if sys.platform == "darwin":
     if sys.version_info < (3, 13):
-        @deprecated("Deprecated in 3.11, to be removed in 3.13.")
-        class MacOSX(BaseBrowser):
-            def __init__(self, name: str) -> None: ...
-            def open(self, url: str, new: int = 0, autoraise: bool = True) -> bool: ...
+        if sys.version_info >= (3, 11):
+            @deprecated("Deprecated since Python 3.11; removed in Python 3.13.")
+            class MacOSX(BaseBrowser):
+                def __init__(self, name: str) -> None: ...
+                def open(self, url: str, new: int = 0, autoraise: bool = True) -> bool: ...
+
+        else:
+            class MacOSX(BaseBrowser):
+                def __init__(self, name: str) -> None: ...
+                def open(self, url: str, new: int = 0, autoraise: bool = True) -> bool: ...
 
     class MacOSXOSAScript(BaseBrowser):  # In runtime this class does not have `name` and `basename`
         if sys.version_info >= (3, 11):
diff --git a/mypy/typeshed/stdlib/winreg.pyi b/mypy/typeshed/stdlib/winreg.pyi
index d4d04817d7e0..53457112ee96 100644
--- a/mypy/typeshed/stdlib/winreg.pyi
+++ b/mypy/typeshed/stdlib/winreg.pyi
@@ -59,13 +59,13 @@ if sys.platform == "win32":
     def EnableReflectionKey(key: _KeyType, /) -> None: ...
     def QueryReflectionKey(key: _KeyType, /) -> bool: ...
 
-    HKEY_CLASSES_ROOT: int
-    HKEY_CURRENT_USER: int
-    HKEY_LOCAL_MACHINE: int
-    HKEY_USERS: int
-    HKEY_PERFORMANCE_DATA: int
-    HKEY_CURRENT_CONFIG: int
-    HKEY_DYN_DATA: int
+    HKEY_CLASSES_ROOT: Final[int]
+    HKEY_CURRENT_USER: Final[int]
+    HKEY_LOCAL_MACHINE: Final[int]
+    HKEY_USERS: Final[int]
+    HKEY_PERFORMANCE_DATA: Final[int]
+    HKEY_CURRENT_CONFIG: Final[int]
+    HKEY_DYN_DATA: Final[int]
 
     KEY_ALL_ACCESS: Final = 983103
     KEY_WRITE: Final = 131078
@@ -123,7 +123,7 @@ if sys.platform == "win32":
         def __int__(self) -> int: ...
         def __enter__(self) -> Self: ...
         def __exit__(
-            self, exc_type: type[BaseException] | None, exc_value: BaseException | None, traceback: TracebackType | None
+            self, exc_type: type[BaseException] | None, exc_value: BaseException | None, traceback: TracebackType | None, /
         ) -> bool | None: ...
         def Close(self) -> None: ...
         def Detach(self) -> int: ...
diff --git a/mypy/typeshed/stdlib/wsgiref/headers.pyi b/mypy/typeshed/stdlib/wsgiref/headers.pyi
index 2654d79bf4e5..9febad4b3277 100644
--- a/mypy/typeshed/stdlib/wsgiref/headers.pyi
+++ b/mypy/typeshed/stdlib/wsgiref/headers.pyi
@@ -1,10 +1,10 @@
 from re import Pattern
-from typing import overload
+from typing import Final, overload
 from typing_extensions import TypeAlias
 
 _HeaderList: TypeAlias = list[tuple[str, str]]
 
-tspecials: Pattern[str]  # undocumented
+tspecials: Final[Pattern[str]]  # undocumented
 
 class Headers:
     def __init__(self, headers: _HeaderList | None = None) -> None: ...
diff --git a/mypy/typeshed/stdlib/wsgiref/simple_server.pyi b/mypy/typeshed/stdlib/wsgiref/simple_server.pyi
index 547f562cc1d4..bdf58719c828 100644
--- a/mypy/typeshed/stdlib/wsgiref/simple_server.pyi
+++ b/mypy/typeshed/stdlib/wsgiref/simple_server.pyi
@@ -1,14 +1,14 @@
 from _typeshed.wsgi import ErrorStream, StartResponse, WSGIApplication, WSGIEnvironment
 from http.server import BaseHTTPRequestHandler, HTTPServer
-from typing import TypeVar, overload
+from typing import Final, TypeVar, overload
 
 from .handlers import SimpleHandler
 
 __all__ = ["WSGIServer", "WSGIRequestHandler", "demo_app", "make_server"]
 
-server_version: str  # undocumented
-sys_version: str  # undocumented
-software_version: str  # undocumented
+server_version: Final[str]  # undocumented
+sys_version: Final[str]  # undocumented
+software_version: Final[str]  # undocumented
 
 class ServerHandler(SimpleHandler):  # undocumented
     server_software: str
diff --git a/mypy/typeshed/stdlib/xml/dom/NodeFilter.pyi b/mypy/typeshed/stdlib/xml/dom/NodeFilter.pyi
index 007df982e06a..7b301373f528 100644
--- a/mypy/typeshed/stdlib/xml/dom/NodeFilter.pyi
+++ b/mypy/typeshed/stdlib/xml/dom/NodeFilter.pyi
@@ -1,22 +1,22 @@
-from typing import Literal
+from typing import Final
 from xml.dom.minidom import Node
 
 class NodeFilter:
-    FILTER_ACCEPT: Literal[1]
-    FILTER_REJECT: Literal[2]
-    FILTER_SKIP: Literal[3]
+    FILTER_ACCEPT: Final = 1
+    FILTER_REJECT: Final = 2
+    FILTER_SKIP: Final = 3
 
-    SHOW_ALL: int
-    SHOW_ELEMENT: int
-    SHOW_ATTRIBUTE: int
-    SHOW_TEXT: int
-    SHOW_CDATA_SECTION: int
-    SHOW_ENTITY_REFERENCE: int
-    SHOW_ENTITY: int
-    SHOW_PROCESSING_INSTRUCTION: int
-    SHOW_COMMENT: int
-    SHOW_DOCUMENT: int
-    SHOW_DOCUMENT_TYPE: int
-    SHOW_DOCUMENT_FRAGMENT: int
-    SHOW_NOTATION: int
+    SHOW_ALL: Final = 0xFFFFFFFF
+    SHOW_ELEMENT: Final = 0x00000001
+    SHOW_ATTRIBUTE: Final = 0x00000002
+    SHOW_TEXT: Final = 0x00000004
+    SHOW_CDATA_SECTION: Final = 0x00000008
+    SHOW_ENTITY_REFERENCE: Final = 0x00000010
+    SHOW_ENTITY: Final = 0x00000020
+    SHOW_PROCESSING_INSTRUCTION: Final = 0x00000040
+    SHOW_COMMENT: Final = 0x00000080
+    SHOW_DOCUMENT: Final = 0x00000100
+    SHOW_DOCUMENT_TYPE: Final = 0x00000200
+    SHOW_DOCUMENT_FRAGMENT: Final = 0x00000400
+    SHOW_NOTATION: Final = 0x00000800
     def acceptNode(self, node: Node) -> int: ...
diff --git a/mypy/typeshed/stdlib/xml/dom/__init__.pyi b/mypy/typeshed/stdlib/xml/dom/__init__.pyi
index d9615f9aacfe..5dbb6c536f61 100644
--- a/mypy/typeshed/stdlib/xml/dom/__init__.pyi
+++ b/mypy/typeshed/stdlib/xml/dom/__init__.pyi
@@ -3,18 +3,19 @@ from typing import Any, Final, Literal
 from .domreg import getDOMImplementation as getDOMImplementation, registerDOMImplementation as registerDOMImplementation
 
 class Node:
-    ELEMENT_NODE: Literal[1]
-    ATTRIBUTE_NODE: Literal[2]
-    TEXT_NODE: Literal[3]
-    CDATA_SECTION_NODE: Literal[4]
-    ENTITY_REFERENCE_NODE: Literal[5]
-    ENTITY_NODE: Literal[6]
-    PROCESSING_INSTRUCTION_NODE: Literal[7]
-    COMMENT_NODE: Literal[8]
-    DOCUMENT_NODE: Literal[9]
-    DOCUMENT_TYPE_NODE: Literal[10]
-    DOCUMENT_FRAGMENT_NODE: Literal[11]
-    NOTATION_NODE: Literal[12]
+    __slots__ = ()
+    ELEMENT_NODE: Final = 1
+    ATTRIBUTE_NODE: Final = 2
+    TEXT_NODE: Final = 3
+    CDATA_SECTION_NODE: Final = 4
+    ENTITY_REFERENCE_NODE: Final = 5
+    ENTITY_NODE: Final = 6
+    PROCESSING_INSTRUCTION_NODE: Final = 7
+    COMMENT_NODE: Final = 8
+    DOCUMENT_NODE: Final = 9
+    DOCUMENT_TYPE_NODE: Final = 10
+    DOCUMENT_FRAGMENT_NODE: Final = 11
+    NOTATION_NODE: Final = 12
 
 # ExceptionCode
 INDEX_SIZE_ERR: Final = 1
@@ -88,10 +89,10 @@ class ValidationErr(DOMException):
     code: Literal[16]
 
 class UserDataHandler:
-    NODE_CLONED: Literal[1]
-    NODE_IMPORTED: Literal[2]
-    NODE_DELETED: Literal[3]
-    NODE_RENAMED: Literal[4]
+    NODE_CLONED: Final = 1
+    NODE_IMPORTED: Final = 2
+    NODE_DELETED: Final = 3
+    NODE_RENAMED: Final = 4
 
 XML_NAMESPACE: Final = "http://www.w3.org/XML/1998/namespace"
 XMLNS_NAMESPACE: Final = "http://www.w3.org/2000/xmlns/"
diff --git a/mypy/typeshed/stdlib/xml/dom/expatbuilder.pyi b/mypy/typeshed/stdlib/xml/dom/expatbuilder.pyi
index 228ad07e15ad..2b9ac8876970 100644
--- a/mypy/typeshed/stdlib/xml/dom/expatbuilder.pyi
+++ b/mypy/typeshed/stdlib/xml/dom/expatbuilder.pyi
@@ -1,5 +1,5 @@
 from _typeshed import ReadableBuffer, SupportsRead
-from typing import Any, NoReturn
+from typing import Any, Final, NoReturn
 from typing_extensions import TypeAlias
 from xml.dom.minidom import Document, DocumentFragment, DOMImplementation, Element, Node, TypeInfo
 from xml.dom.xmlbuilder import DOMBuilderFilter, Options
@@ -7,16 +7,17 @@ from xml.parsers.expat import XMLParserType
 
 _Model: TypeAlias = tuple[int, int, str | None, tuple[Any, ...]]  # same as in pyexpat
 
-TEXT_NODE = Node.TEXT_NODE
-CDATA_SECTION_NODE = Node.CDATA_SECTION_NODE
-DOCUMENT_NODE = Node.DOCUMENT_NODE
-FILTER_ACCEPT = DOMBuilderFilter.FILTER_ACCEPT
-FILTER_REJECT = DOMBuilderFilter.FILTER_REJECT
-FILTER_SKIP = DOMBuilderFilter.FILTER_SKIP
-FILTER_INTERRUPT = DOMBuilderFilter.FILTER_INTERRUPT
+TEXT_NODE: Final = Node.TEXT_NODE
+CDATA_SECTION_NODE: Final = Node.CDATA_SECTION_NODE
+DOCUMENT_NODE: Final = Node.DOCUMENT_NODE
+FILTER_ACCEPT: Final = DOMBuilderFilter.FILTER_ACCEPT
+FILTER_REJECT: Final = DOMBuilderFilter.FILTER_REJECT
+FILTER_SKIP: Final = DOMBuilderFilter.FILTER_SKIP
+FILTER_INTERRUPT: Final = DOMBuilderFilter.FILTER_INTERRUPT
 theDOMImplementation: DOMImplementation
 
 class ElementInfo:
+    __slots__ = ("_attr_info", "_model", "tagName")
     tagName: str
     def __init__(self, tagName: str, model: _Model | None = None) -> None: ...
     def getAttributeType(self, aname: str) -> TypeInfo: ...
@@ -66,19 +67,23 @@ class ExpatBuilder:
     def xml_decl_handler(self, version: str, encoding: str | None, standalone: int) -> None: ...
 
 class FilterVisibilityController:
+    __slots__ = ("filter",)
     filter: DOMBuilderFilter
     def __init__(self, filter: DOMBuilderFilter) -> None: ...
     def startContainer(self, node: Node) -> int: ...
     def acceptNode(self, node: Node) -> int: ...
 
 class FilterCrutch:
+    __slots__ = ("_builder", "_level", "_old_start", "_old_end")
     def __init__(self, builder: ExpatBuilder) -> None: ...
 
 class Rejecter(FilterCrutch):
+    __slots__ = ()
     def start_element_handler(self, *args: Any) -> None: ...
     def end_element_handler(self, *args: Any) -> None: ...
 
 class Skipper(FilterCrutch):
+    __slots__ = ()
     def start_element_handler(self, *args: Any) -> None: ...
     def end_element_handler(self, *args: Any) -> None: ...
 
diff --git a/mypy/typeshed/stdlib/xml/dom/minicompat.pyi b/mypy/typeshed/stdlib/xml/dom/minicompat.pyi
index 162f60254a58..6fcaee019dc2 100644
--- a/mypy/typeshed/stdlib/xml/dom/minicompat.pyi
+++ b/mypy/typeshed/stdlib/xml/dom/minicompat.pyi
@@ -8,11 +8,13 @@ _T = TypeVar("_T")
 StringTypes: tuple[type[str]]
 
 class NodeList(list[_T]):
+    __slots__ = ()
     @property
     def length(self) -> int: ...
     def item(self, index: int) -> _T | None: ...
 
 class EmptyNodeList(tuple[()]):
+    __slots__ = ()
     @property
     def length(self) -> Literal[0]: ...
     def item(self, index: int) -> None: ...
diff --git a/mypy/typeshed/stdlib/xml/dom/minidom.pyi b/mypy/typeshed/stdlib/xml/dom/minidom.pyi
index ab2ef87e38a8..e0431417aa3c 100644
--- a/mypy/typeshed/stdlib/xml/dom/minidom.pyi
+++ b/mypy/typeshed/stdlib/xml/dom/minidom.pyi
@@ -3,7 +3,7 @@ from _collections_abc import dict_keys, dict_values
 from _typeshed import Incomplete, ReadableBuffer, SupportsRead, SupportsWrite
 from collections.abc import Iterable, Sequence
 from types import TracebackType
-from typing import Any, ClassVar, Generic, Literal, NoReturn, Protocol, TypeVar, overload
+from typing import Any, ClassVar, Generic, Literal, NoReturn, Protocol, TypeVar, overload, type_check_only
 from typing_extensions import Self, TypeAlias
 from xml.dom.minicompat import EmptyNodeList, NodeList
 from xml.dom.xmlbuilder import DocumentLS, DOMImplementationLS
@@ -40,9 +40,11 @@ _ImportableNodeVar = TypeVar(
     | Notation,
 )
 
+@type_check_only
 class _DOMErrorHandler(Protocol):
     def handleError(self, error: Exception) -> bool: ...
 
+@type_check_only
 class _UserDataHandler(Protocol):
     def handle(self, operation: int, key: str, data: Any, src: Node, dst: Node) -> None: ...
 
@@ -186,6 +188,7 @@ _AttrChildrenVar = TypeVar("_AttrChildrenVar", bound=_AttrChildren)
 _AttrChildrenPlusFragment = TypeVar("_AttrChildrenPlusFragment", bound=_AttrChildren | DocumentFragment)
 
 class Attr(Node):
+    __slots__ = ("_name", "_value", "namespaceURI", "_prefix", "childNodes", "_localName", "ownerDocument", "ownerElement")
     nodeType: ClassVar[Literal[2]]
     nodeName: str  # same as Attr.name
     nodeValue: str  # same as Attr.value
@@ -229,6 +232,7 @@ class Attr(Node):
 # In the DOM, this interface isn't specific to Attr, but our implementation is
 # because that's the only place we use it.
 class NamedNodeMap:
+    __slots__ = ("_attrs", "_attrsNS", "_ownerElement")
     def __init__(self, attrs: dict[str, Attr], attrsNS: dict[_NSName, Attr], ownerElement: Element) -> None: ...
     @property
     def length(self) -> int: ...
@@ -260,6 +264,7 @@ class NamedNodeMap:
 AttributeList = NamedNodeMap
 
 class TypeInfo:
+    __slots__ = ("namespace", "name")
     namespace: str | None
     name: str | None
     def __init__(self, namespace: Incomplete | None, name: str | None) -> None: ...
@@ -268,6 +273,20 @@ _ElementChildrenVar = TypeVar("_ElementChildrenVar", bound=_ElementChildren)
 _ElementChildrenPlusFragment = TypeVar("_ElementChildrenPlusFragment", bound=_ElementChildren | DocumentFragment)
 
 class Element(Node):
+    __slots__ = (
+        "ownerDocument",
+        "parentNode",
+        "tagName",
+        "nodeName",
+        "prefix",
+        "namespaceURI",
+        "_localName",
+        "childNodes",
+        "_attrs",
+        "_attrsNS",
+        "nextSibling",
+        "previousSibling",
+    )
     nodeType: ClassVar[Literal[1]]
     nodeName: str  # same as Element.tagName
     nodeValue: None
@@ -329,6 +348,7 @@ class Element(Node):
     def removeChild(self, oldChild: _ElementChildrenVar) -> _ElementChildrenVar: ...  # type: ignore[override]
 
 class Childless:
+    __slots__ = ()
     attributes: None
     childNodes: EmptyNodeList
     @property
@@ -345,6 +365,7 @@ class Childless:
     def replaceChild(self, newChild: _NodesThatAreChildren | DocumentFragment, oldChild: _NodesThatAreChildren) -> NoReturn: ...
 
 class ProcessingInstruction(Childless, Node):
+    __slots__ = ("target", "data")
     nodeType: ClassVar[Literal[7]]
     nodeName: str  # same as ProcessingInstruction.target
     nodeValue: str  # same as ProcessingInstruction.data
@@ -371,6 +392,7 @@ class ProcessingInstruction(Childless, Node):
     def writexml(self, writer: SupportsWrite[str], indent: str = "", addindent: str = "", newl: str = "") -> None: ...
 
 class CharacterData(Childless, Node):
+    __slots__ = ("_data", "ownerDocument", "parentNode", "previousSibling", "nextSibling")
     nodeValue: str
     attributes: None
 
@@ -395,6 +417,7 @@ class CharacterData(Childless, Node):
     def replaceData(self, offset: int, count: int, arg: str) -> None: ...
 
 class Text(CharacterData):
+    __slots__ = ()
     nodeType: ClassVar[Literal[3]]
     nodeName: Literal["#text"]
     nodeValue: str  # same as CharacterData.data, the content of the text node
@@ -446,6 +469,7 @@ class Comment(CharacterData):
     def writexml(self, writer: SupportsWrite[str], indent: str = "", addindent: str = "", newl: str = "") -> None: ...
 
 class CDATASection(Text):
+    __slots__ = ()
     nodeType: ClassVar[Literal[4]]  # type: ignore[assignment]
     nodeName: Literal["#cdata-section"]  # type: ignore[assignment]
     nodeValue: str  # same as CharacterData.data, the content of the CDATA Section
@@ -458,6 +482,7 @@ class CDATASection(Text):
     def writexml(self, writer: SupportsWrite[str], indent: str = "", addindent: str = "", newl: str = "") -> None: ...
 
 class ReadOnlySequentialNamedNodeMap(Generic[_N]):
+    __slots__ = ("_seq",)
     def __init__(self, seq: Sequence[_N] = ()) -> None: ...
     def __len__(self) -> int: ...
     def getNamedItem(self, name: str) -> _N | None: ...
@@ -472,6 +497,7 @@ class ReadOnlySequentialNamedNodeMap(Generic[_N]):
     def length(self) -> int: ...
 
 class Identified:
+    __slots__ = ("publicId", "systemId")
     publicId: str | None
     systemId: str | None
 
@@ -563,6 +589,7 @@ class DOMImplementation(DOMImplementationLS):
     def getInterface(self, feature: str) -> Self | None: ...
 
 class ElementInfo:
+    __slots__ = ("tagName",)
     tagName: str
     def __init__(self, name: str) -> None: ...
     def getAttributeType(self, aname: str) -> TypeInfo: ...
@@ -575,6 +602,7 @@ class ElementInfo:
 _DocumentChildrenPlusFragment = TypeVar("_DocumentChildrenPlusFragment", bound=_DocumentChildren | DocumentFragment)
 
 class Document(Node, DocumentLS):
+    __slots__ = ("_elem_info", "doctype", "_id_search_stack", "childNodes", "_id_cache")
     nodeType: ClassVar[Literal[9]]
     nodeName: Literal["#document"]
     nodeValue: None
diff --git a/mypy/typeshed/stdlib/xml/dom/pulldom.pyi b/mypy/typeshed/stdlib/xml/dom/pulldom.pyi
index d9458654c185..df7a3ad0eddb 100644
--- a/mypy/typeshed/stdlib/xml/dom/pulldom.pyi
+++ b/mypy/typeshed/stdlib/xml/dom/pulldom.pyi
@@ -99,7 +99,7 @@ class SAX2DOM(PullDOM):
     def ignorableWhitespace(self, chars: str) -> None: ...
     def characters(self, chars: str) -> None: ...
 
-default_bufsize: int
+default_bufsize: Final[int]
 
 def parse(
     stream_or_string: str | _SupportsReadClose[bytes] | _SupportsReadClose[str],
diff --git a/mypy/typeshed/stdlib/xml/dom/xmlbuilder.pyi b/mypy/typeshed/stdlib/xml/dom/xmlbuilder.pyi
index 6fb18bbc4eda..f19f7050b08d 100644
--- a/mypy/typeshed/stdlib/xml/dom/xmlbuilder.pyi
+++ b/mypy/typeshed/stdlib/xml/dom/xmlbuilder.pyi
@@ -1,5 +1,5 @@
 from _typeshed import SupportsRead
-from typing import Any, Literal, NoReturn
+from typing import Any, Final, Literal, NoReturn
 from xml.dom.minidom import Document, Node, _DOMErrorHandler
 
 __all__ = ["DOMBuilder", "DOMEntityResolver", "DOMInputSource"]
@@ -29,10 +29,10 @@ class DOMBuilder:
     entityResolver: DOMEntityResolver | None
     errorHandler: _DOMErrorHandler | None
     filter: DOMBuilderFilter | None
-    ACTION_REPLACE: Literal[1]
-    ACTION_APPEND_AS_CHILDREN: Literal[2]
-    ACTION_INSERT_AFTER: Literal[3]
-    ACTION_INSERT_BEFORE: Literal[4]
+    ACTION_REPLACE: Final = 1
+    ACTION_APPEND_AS_CHILDREN: Final = 2
+    ACTION_INSERT_AFTER: Final = 3
+    ACTION_INSERT_BEFORE: Final = 4
     def __init__(self) -> None: ...
     def setFeature(self, name: str, state: int) -> None: ...
     def supportsFeature(self, name: str) -> bool: ...
@@ -44,9 +44,11 @@ class DOMBuilder:
     def parseWithContext(self, input: DOMInputSource, cnode: Node, action: Literal[1, 2, 3, 4]) -> NoReturn: ...
 
 class DOMEntityResolver:
+    __slots__ = ("_opener",)
     def resolveEntity(self, publicId: str | None, systemId: str) -> DOMInputSource: ...
 
 class DOMInputSource:
+    __slots__ = ("byteStream", "characterStream", "stringData", "encoding", "publicId", "systemId", "baseURI")
     byteStream: SupportsRead[bytes] | None
     characterStream: SupportsRead[str] | None
     stringData: str | None
@@ -56,10 +58,10 @@ class DOMInputSource:
     baseURI: str | None
 
 class DOMBuilderFilter:
-    FILTER_ACCEPT: Literal[1]
-    FILTER_REJECT: Literal[2]
-    FILTER_SKIP: Literal[3]
-    FILTER_INTERRUPT: Literal[4]
+    FILTER_ACCEPT: Final = 1
+    FILTER_REJECT: Final = 2
+    FILTER_SKIP: Final = 3
+    FILTER_INTERRUPT: Final = 4
     whatToShow: int
     def acceptNode(self, element: Node) -> Literal[1, 2, 3, 4]: ...
     def startContainer(self, element: Node) -> Literal[1, 2, 3, 4]: ...
@@ -72,8 +74,8 @@ class DocumentLS:
     def saveXML(self, snode: Node | None) -> str: ...
 
 class DOMImplementationLS:
-    MODE_SYNCHRONOUS: Literal[1]
-    MODE_ASYNCHRONOUS: Literal[2]
+    MODE_SYNCHRONOUS: Final = 1
+    MODE_ASYNCHRONOUS: Final = 2
     def createDOMBuilder(self, mode: Literal[1], schemaType: None) -> DOMBuilder: ...
     def createDOMWriter(self) -> NoReturn: ...
     def createDOMInputSource(self) -> DOMInputSource: ...
diff --git a/mypy/typeshed/stdlib/xml/etree/ElementInclude.pyi b/mypy/typeshed/stdlib/xml/etree/ElementInclude.pyi
index 8f20ee15a14e..10784e7d4021 100644
--- a/mypy/typeshed/stdlib/xml/etree/ElementInclude.pyi
+++ b/mypy/typeshed/stdlib/xml/etree/ElementInclude.pyi
@@ -1,16 +1,18 @@
 from _typeshed import FileDescriptorOrPath
-from typing import Final, Literal, Protocol, overload
+from typing import Final, Literal, Protocol, overload, type_check_only
 from xml.etree.ElementTree import Element
 
+@type_check_only
 class _Loader(Protocol):
     @overload
     def __call__(self, href: FileDescriptorOrPath, parse: Literal["xml"], encoding: str | None = None) -> Element: ...
     @overload
     def __call__(self, href: FileDescriptorOrPath, parse: Literal["text"], encoding: str | None = None) -> str: ...
 
-XINCLUDE: Final[str]
-XINCLUDE_INCLUDE: Final[str]
-XINCLUDE_FALLBACK: Final[str]
+XINCLUDE: Final = "{http://www.w3.org/2001/XInclude}"
+
+XINCLUDE_INCLUDE: Final = "{http://www.w3.org/2001/XInclude}include"
+XINCLUDE_FALLBACK: Final = "{http://www.w3.org/2001/XInclude}fallback"
 
 DEFAULT_MAX_INCLUSION_DEPTH: Final = 6
 
diff --git a/mypy/typeshed/stdlib/xml/etree/ElementPath.pyi b/mypy/typeshed/stdlib/xml/etree/ElementPath.pyi
index ebfb4f1ffbb9..80f3c55c1489 100644
--- a/mypy/typeshed/stdlib/xml/etree/ElementPath.pyi
+++ b/mypy/typeshed/stdlib/xml/etree/ElementPath.pyi
@@ -1,10 +1,10 @@
 from collections.abc import Callable, Generator, Iterable
 from re import Pattern
-from typing import Any, Literal, TypeVar, overload
+from typing import Any, Final, Literal, TypeVar, overload
 from typing_extensions import TypeAlias
 from xml.etree.ElementTree import Element
 
-xpath_tokenizer_re: Pattern[str]
+xpath_tokenizer_re: Final[Pattern[str]]
 
 _Token: TypeAlias = tuple[str, str]
 _Next: TypeAlias = Callable[[], _Token]
@@ -20,7 +20,7 @@ def prepare_descendant(next: _Next, token: _Token) -> _Callback | None: ...
 def prepare_parent(next: _Next, token: _Token) -> _Callback: ...
 def prepare_predicate(next: _Next, token: _Token) -> _Callback | None: ...
 
-ops: dict[str, Callable[[_Next, _Token], _Callback | None]]
+ops: Final[dict[str, Callable[[_Next, _Token], _Callback | None]]]
 
 class _SelectorContext:
     parent_map: dict[Element, Element] | None
diff --git a/mypy/typeshed/stdlib/xml/etree/ElementTree.pyi b/mypy/typeshed/stdlib/xml/etree/ElementTree.pyi
index 4c55a1a7452e..e8f737778040 100644
--- a/mypy/typeshed/stdlib/xml/etree/ElementTree.pyi
+++ b/mypy/typeshed/stdlib/xml/etree/ElementTree.pyi
@@ -3,7 +3,7 @@ from _collections_abc import dict_keys
 from _typeshed import FileDescriptorOrPath, ReadableBuffer, SupportsRead, SupportsWrite
 from collections.abc import Callable, Generator, ItemsView, Iterable, Iterator, Mapping, Sequence
 from typing import Any, Final, Generic, Literal, Protocol, SupportsIndex, TypeVar, overload, type_check_only
-from typing_extensions import TypeAlias, TypeGuard, deprecated
+from typing_extensions import TypeAlias, TypeGuard, deprecated, disjoint_base
 from xml.parsers.expat import XMLParserType
 
 __all__ = [
@@ -78,14 +78,13 @@ def canonicalize(
 ) -> None: ...
 
 # The tag for Element can be set to the Comment or ProcessingInstruction
-# functions defined in this module. _ElementCallable could be a recursive
-# type, but defining it that way uncovered a bug in pytype.
-_ElementCallable: TypeAlias = Callable[..., Element[Any]]
-_CallableElement: TypeAlias = Element[_ElementCallable]
+# functions defined in this module.
+_ElementCallable: TypeAlias = Callable[..., Element[_ElementCallable]]
 
 _Tag = TypeVar("_Tag", default=str, bound=str | _ElementCallable)
 _OtherTag = TypeVar("_OtherTag", default=str, bound=str | _ElementCallable)
 
+@disjoint_base
 class Element(Generic[_Tag]):
     tag: _Tag
     attrib: dict[str, str]
@@ -138,8 +137,8 @@ class Element(Generic[_Tag]):
     def __bool__(self) -> bool: ...
 
 def SubElement(parent: Element, tag: str, attrib: dict[str, str] = ..., **extra: str) -> Element: ...
-def Comment(text: str | None = None) -> _CallableElement: ...
-def ProcessingInstruction(target: str, text: str | None = None) -> _CallableElement: ...
+def Comment(text: str | None = None) -> Element[_ElementCallable]: ...
+def ProcessingInstruction(target: str, text: str | None = None) -> Element[_ElementCallable]: ...
 
 PI = ProcessingInstruction
 
@@ -182,7 +181,7 @@ class ElementTree(Generic[_Root]):
     ) -> None: ...
     def write_c14n(self, file: _FileWriteC14N) -> None: ...
 
-HTML_EMPTY: set[str]
+HTML_EMPTY: Final[set[str]]
 
 def register_namespace(prefix: str, uri: str) -> None: ...
 @overload
@@ -288,6 +287,7 @@ def fromstringlist(sequence: Sequence[str | ReadableBuffer], parser: XMLParser |
 # elementfactories.
 _ElementFactory: TypeAlias = Callable[[Any, dict[Any, Any]], Element]
 
+@disjoint_base
 class TreeBuilder:
     # comment_factory can take None because passing None to Comment is not an error
     def __init__(
@@ -335,6 +335,7 @@ class C14NWriterTarget:
 # The target type is tricky, because the implementation doesn't
 # require any particular attribute to be present. This documents the attributes
 # that can be present, but uncommenting any of them would require them.
+@type_check_only
 class _Target(Protocol):
     # start: Callable[str, dict[str, str], Any] | None
     # end: Callable[[str], Any] | None
@@ -352,6 +353,7 @@ _E = TypeVar("_E", default=Element)
 # The default target is TreeBuilder, which returns Element.
 # C14NWriterTarget does not implement a close method, so using it results
 # in a type of XMLParser[None].
+@disjoint_base
 class XMLParser(Generic[_E]):
     parser: XMLParserType
     target: _Target
diff --git a/mypy/typeshed/stdlib/xml/sax/__init__.pyi b/mypy/typeshed/stdlib/xml/sax/__init__.pyi
index ebe92d28c74d..679466fa34d2 100644
--- a/mypy/typeshed/stdlib/xml/sax/__init__.pyi
+++ b/mypy/typeshed/stdlib/xml/sax/__init__.pyi
@@ -1,7 +1,7 @@
 import sys
 from _typeshed import ReadableBuffer, StrPath, SupportsRead, _T_co
 from collections.abc import Iterable
-from typing import Protocol
+from typing import Final, Protocol, type_check_only
 from typing_extensions import TypeAlias
 from xml.sax._exceptions import (
     SAXException as SAXException,
@@ -13,12 +13,13 @@ from xml.sax._exceptions import (
 from xml.sax.handler import ContentHandler as ContentHandler, ErrorHandler as ErrorHandler
 from xml.sax.xmlreader import InputSource as InputSource, XMLReader
 
+@type_check_only
 class _SupportsReadClose(SupportsRead[_T_co], Protocol[_T_co]):
     def close(self) -> None: ...
 
 _Source: TypeAlias = StrPath | _SupportsReadClose[bytes] | _SupportsReadClose[str]
 
-default_parser_list: list[str]
+default_parser_list: Final[list[str]]
 
 def make_parser(parser_list: Iterable[str] = ()) -> XMLReader: ...
 def parse(source: _Source, handler: ContentHandler, errorHandler: ErrorHandler = ...) -> None: ...
diff --git a/mypy/typeshed/stdlib/xml/sax/expatreader.pyi b/mypy/typeshed/stdlib/xml/sax/expatreader.pyi
index 012d6c03e121..3f9573a25f9a 100644
--- a/mypy/typeshed/stdlib/xml/sax/expatreader.pyi
+++ b/mypy/typeshed/stdlib/xml/sax/expatreader.pyi
@@ -1,7 +1,7 @@
 import sys
 from _typeshed import ReadableBuffer
 from collections.abc import Mapping
-from typing import Any, Literal, overload
+from typing import Any, Final, Literal, overload
 from typing_extensions import TypeAlias
 from xml.sax import _Source, xmlreader
 from xml.sax.handler import _ContentHandlerProtocol
@@ -11,7 +11,7 @@ if sys.version_info >= (3, 10):
 
 _BoolType: TypeAlias = Literal[0, 1] | bool
 
-version: str
+version: Final[str]
 AttributesImpl = xmlreader.AttributesImpl
 AttributesNSImpl = xmlreader.AttributesNSImpl
 
diff --git a/mypy/typeshed/stdlib/xml/sax/handler.pyi b/mypy/typeshed/stdlib/xml/sax/handler.pyi
index 550911734596..5ecbfa6f1272 100644
--- a/mypy/typeshed/stdlib/xml/sax/handler.pyi
+++ b/mypy/typeshed/stdlib/xml/sax/handler.pyi
@@ -1,8 +1,8 @@
 import sys
-from typing import Literal, NoReturn, Protocol, type_check_only
+from typing import Final, NoReturn, Protocol, type_check_only
 from xml.sax import xmlreader
 
-version: str
+version: Final[str]
 
 @type_check_only
 class _ErrorHandlerProtocol(Protocol):  # noqa: Y046  # Protocol is not used
@@ -62,20 +62,20 @@ class _EntityResolverProtocol(Protocol):  # noqa: Y046  # Protocol is not used
 class EntityResolver:
     def resolveEntity(self, publicId: str | None, systemId: str) -> str: ...
 
-feature_namespaces: str
-feature_namespace_prefixes: str
-feature_string_interning: str
-feature_validation: str
-feature_external_ges: str
-feature_external_pes: str
-all_features: list[str]
-property_lexical_handler: Literal["http://xml.org/sax/properties/lexical-handler"]
-property_declaration_handler: Literal["http://xml.org/sax/properties/declaration-handler"]
-property_dom_node: Literal["http://xml.org/sax/properties/dom-node"]
-property_xml_string: Literal["http://xml.org/sax/properties/xml-string"]
-property_encoding: Literal["http://www.python.org/sax/properties/encoding"]
-property_interning_dict: Literal["http://www.python.org/sax/properties/interning-dict"]
-all_properties: list[str]
+feature_namespaces: Final = "http://xml.org/sax/features/namespaces"
+feature_namespace_prefixes: Final = "http://xml.org/sax/features/namespace-prefixes"
+feature_string_interning: Final = "http://xml.org/sax/features/string-interning"
+feature_validation: Final = "http://xml.org/sax/features/validation"
+feature_external_ges: Final[str]  # too long string
+feature_external_pes: Final[str]  # too long string
+all_features: Final[list[str]]
+property_lexical_handler: Final = "http://xml.org/sax/properties/lexical-handler"
+property_declaration_handler: Final = "http://xml.org/sax/properties/declaration-handler"
+property_dom_node: Final = "http://xml.org/sax/properties/dom-node"
+property_xml_string: Final = "http://xml.org/sax/properties/xml-string"
+property_encoding: Final = "http://www.python.org/sax/properties/encoding"
+property_interning_dict: Final[str]  # too long string
+all_properties: Final[list[str]]
 
 if sys.version_info >= (3, 10):
     class LexicalHandler:
diff --git a/mypy/typeshed/stdlib/xmlrpc/client.pyi b/mypy/typeshed/stdlib/xmlrpc/client.pyi
index 6cc4361f4a09..42420ee85848 100644
--- a/mypy/typeshed/stdlib/xmlrpc/client.pyi
+++ b/mypy/typeshed/stdlib/xmlrpc/client.pyi
@@ -6,9 +6,10 @@ from collections.abc import Callable, Iterable, Mapping
 from datetime import datetime
 from io import BytesIO
 from types import TracebackType
-from typing import Any, ClassVar, Final, Literal, Protocol, overload
+from typing import Any, ClassVar, Final, Literal, Protocol, overload, type_check_only
 from typing_extensions import Self, TypeAlias
 
+@type_check_only
 class _SupportsTimeTuple(Protocol):
     def timetuple(self) -> time.struct_time: ...
 
diff --git a/mypy/typeshed/stdlib/xmlrpc/server.pyi b/mypy/typeshed/stdlib/xmlrpc/server.pyi
index 5f497aa7190e..286aaf980fbf 100644
--- a/mypy/typeshed/stdlib/xmlrpc/server.pyi
+++ b/mypy/typeshed/stdlib/xmlrpc/server.pyi
@@ -4,28 +4,34 @@ import socketserver
 from _typeshed import ReadableBuffer
 from collections.abc import Callable, Iterable, Mapping
 from re import Pattern
-from typing import Any, ClassVar, Protocol
+from typing import Any, ClassVar, Protocol, type_check_only
 from typing_extensions import TypeAlias
 from xmlrpc.client import Fault, _Marshallable
 
 # The dispatch accepts anywhere from 0 to N arguments, no easy way to allow this in mypy
+@type_check_only
 class _DispatchArity0(Protocol):
     def __call__(self) -> _Marshallable: ...
 
+@type_check_only
 class _DispatchArity1(Protocol):
     def __call__(self, arg1: _Marshallable, /) -> _Marshallable: ...
 
+@type_check_only
 class _DispatchArity2(Protocol):
     def __call__(self, arg1: _Marshallable, arg2: _Marshallable, /) -> _Marshallable: ...
 
+@type_check_only
 class _DispatchArity3(Protocol):
     def __call__(self, arg1: _Marshallable, arg2: _Marshallable, arg3: _Marshallable, /) -> _Marshallable: ...
 
+@type_check_only
 class _DispatchArity4(Protocol):
     def __call__(
         self, arg1: _Marshallable, arg2: _Marshallable, arg3: _Marshallable, arg4: _Marshallable, /
     ) -> _Marshallable: ...
 
+@type_check_only
 class _DispatchArityN(Protocol):
     def __call__(self, *args: _Marshallable) -> _Marshallable: ...
 
diff --git a/mypy/typeshed/stdlib/zipfile/__init__.pyi b/mypy/typeshed/stdlib/zipfile/__init__.pyi
index 27c1ef0246c7..e573d04dba05 100644
--- a/mypy/typeshed/stdlib/zipfile/__init__.pyi
+++ b/mypy/typeshed/stdlib/zipfile/__init__.pyi
@@ -5,7 +5,7 @@ from collections.abc import Callable, Iterable, Iterator
 from io import TextIOWrapper
 from os import PathLike
 from types import TracebackType
-from typing import IO, Final, Literal, Protocol, overload
+from typing import IO, Final, Literal, Protocol, overload, type_check_only
 from typing_extensions import Self, TypeAlias
 
 __all__ = [
@@ -41,6 +41,7 @@ error = BadZipfile
 
 class LargeZipFile(Exception): ...
 
+@type_check_only
 class _ZipStream(Protocol):
     def read(self, n: int, /) -> bytes: ...
     # The following methods are optional:
@@ -49,11 +50,13 @@ class _ZipStream(Protocol):
     # def seek(self, n: int, /) -> object: ...
 
 # Stream shape as required by _EndRecData() and _EndRecData64().
+@type_check_only
 class _SupportsReadSeekTell(Protocol):
     def read(self, n: int = ..., /) -> bytes: ...
     def seek(self, cookie: int, whence: int, /) -> object: ...
     def tell(self) -> int: ...
 
+@type_check_only
 class _ClosableZipStream(_ZipStream, Protocol):
     def close(self) -> object: ...
 
@@ -93,18 +96,23 @@ class ZipExtFile(io.BufferedIOBase):
     def read1(self, n: int | None) -> bytes: ...  # type: ignore[override]
     def seek(self, offset: int, whence: int = 0) -> int: ...
 
+@type_check_only
 class _Writer(Protocol):
     def write(self, s: str, /) -> object: ...
 
+@type_check_only
 class _ZipReadable(Protocol):
     def seek(self, offset: int, whence: int = 0, /) -> int: ...
     def read(self, n: int = -1, /) -> bytes: ...
 
+@type_check_only
 class _ZipTellable(Protocol):
     def tell(self) -> int: ...
 
+@type_check_only
 class _ZipReadableTellable(_ZipReadable, _ZipTellable, Protocol): ...
 
+@type_check_only
 class _ZipWritable(Protocol):
     def flush(self) -> None: ...
     def close(self) -> None: ...
@@ -153,7 +161,7 @@ class ZipFile:
         def __init__(
             self,
             file: StrPath | _ZipWritable,
-            mode: Literal["w", "x"] = ...,
+            mode: Literal["w", "x"],
             compression: int = 0,
             allowZip64: bool = True,
             compresslevel: int | None = None,
@@ -165,7 +173,7 @@ class ZipFile:
         def __init__(
             self,
             file: StrPath | _ZipReadableTellable,
-            mode: Literal["a"] = ...,
+            mode: Literal["a"],
             compression: int = 0,
             allowZip64: bool = True,
             compresslevel: int | None = None,
@@ -200,7 +208,7 @@ class ZipFile:
         def __init__(
             self,
             file: StrPath | _ZipWritable,
-            mode: Literal["w", "x"] = ...,
+            mode: Literal["w", "x"],
             compression: int = 0,
             allowZip64: bool = True,
             compresslevel: int | None = None,
@@ -211,7 +219,7 @@ class ZipFile:
         def __init__(
             self,
             file: StrPath | _ZipReadableTellable,
-            mode: Literal["a"] = ...,
+            mode: Literal["a"],
             compression: int = 0,
             allowZip64: bool = True,
             compresslevel: int | None = None,
@@ -254,9 +262,6 @@ class ZipFile:
     ) -> None: ...
     if sys.version_info >= (3, 11):
         def mkdir(self, zinfo_or_directory_name: str | ZipInfo, mode: int = 0o777) -> None: ...
-    if sys.version_info >= (3, 14):
-        @property
-        def data_offset(self) -> int | None: ...
 
     def __del__(self) -> None: ...
 
@@ -267,6 +272,29 @@ class PyZipFile(ZipFile):
     def writepy(self, pathname: str, basename: str = "", filterfunc: Callable[[str], bool] | None = None) -> None: ...
 
 class ZipInfo:
+    __slots__ = (
+        "orig_filename",
+        "filename",
+        "date_time",
+        "compress_type",
+        "compress_level",
+        "comment",
+        "extra",
+        "create_system",
+        "create_version",
+        "extract_version",
+        "reserved",
+        "flag_bits",
+        "volume",
+        "internal_attr",
+        "external_attr",
+        "header_offset",
+        "CRC",
+        "compress_size",
+        "file_size",
+        "_raw_time",
+        "_end_offset",
+    )
     filename: str
     date_time: _DateTuple
     compress_type: int
diff --git a/mypy/typeshed/stdlib/zipfile/_path/glob.pyi b/mypy/typeshed/stdlib/zipfile/_path/glob.pyi
index f25ae71725c0..f6a661be8cdf 100644
--- a/mypy/typeshed/stdlib/zipfile/_path/glob.pyi
+++ b/mypy/typeshed/stdlib/zipfile/_path/glob.pyi
@@ -4,7 +4,11 @@ from re import Match
 
 if sys.version_info >= (3, 13):
     class Translator:
-        def __init__(self, seps: str = ...) -> None: ...
+        if sys.platform == "win32":
+            def __init__(self, seps: str = "\\/") -> None: ...
+        else:
+            def __init__(self, seps: str = "/") -> None: ...
+
         def translate(self, pattern: str) -> str: ...
         def extend(self, pattern: str) -> str: ...
         def match_dirs(self, pattern: str) -> str: ...
diff --git a/mypy/typeshed/stdlib/zipimport.pyi b/mypy/typeshed/stdlib/zipimport.pyi
index 4aab318e7c71..22af3c272759 100644
--- a/mypy/typeshed/stdlib/zipimport.pyi
+++ b/mypy/typeshed/stdlib/zipimport.pyi
@@ -27,8 +27,14 @@ class zipimporter(_LoaderBasics):
         def __init__(self, path: StrOrBytesPath) -> None: ...
 
     if sys.version_info < (3, 12):
-        def find_loader(self, fullname: str, path: str | None = None) -> tuple[zipimporter | None, list[str]]: ...  # undocumented
-        def find_module(self, fullname: str, path: str | None = None) -> zipimporter | None: ...
+        if sys.version_info >= (3, 10):
+            @deprecated("Deprecated since Python 3.10; removed in Python 3.12. Use `find_spec()` instead.")
+            def find_loader(self, fullname: str, path: str | None = None) -> tuple[zipimporter | None, list[str]]: ...
+            @deprecated("Deprecated since Python 3.10; removed in Python 3.12. Use `find_spec()` instead.")
+            def find_module(self, fullname: str, path: str | None = None) -> zipimporter | None: ...
+        else:
+            def find_loader(self, fullname: str, path: str | None = None) -> tuple[zipimporter | None, list[str]]: ...
+            def find_module(self, fullname: str, path: str | None = None) -> zipimporter | None: ...
 
     def get_code(self, fullname: str) -> CodeType: ...
     def get_data(self, pathname: str) -> bytes: ...
@@ -42,10 +48,12 @@ class zipimporter(_LoaderBasics):
 
     def get_source(self, fullname: str) -> str | None: ...
     def is_package(self, fullname: str) -> bool: ...
-    @deprecated("Deprecated since 3.10; use exec_module() instead")
-    def load_module(self, fullname: str) -> ModuleType: ...
     if sys.version_info >= (3, 10):
+        @deprecated("Deprecated since Python 3.10; removed in Python 3.15. Use `exec_module()` instead.")
+        def load_module(self, fullname: str) -> ModuleType: ...
         def exec_module(self, module: ModuleType) -> None: ...
         def create_module(self, spec: ModuleSpec) -> None: ...
         def find_spec(self, fullname: str, target: ModuleType | None = None) -> ModuleSpec | None: ...
         def invalidate_caches(self) -> None: ...
+    else:
+        def load_module(self, fullname: str) -> ModuleType: ...
diff --git a/mypy/typeshed/stdlib/zlib.pyi b/mypy/typeshed/stdlib/zlib.pyi
index 7cafb44b34a7..4e410fdd18ad 100644
--- a/mypy/typeshed/stdlib/zlib.pyi
+++ b/mypy/typeshed/stdlib/zlib.pyi
@@ -4,11 +4,11 @@ from typing import Any, Final, final, type_check_only
 from typing_extensions import Self
 
 DEFLATED: Final = 8
-DEF_MEM_LEVEL: int  # can change
+DEF_MEM_LEVEL: Final[int]
 DEF_BUF_SIZE: Final = 16384
-MAX_WBITS: int
-ZLIB_VERSION: str  # can change
-ZLIB_RUNTIME_VERSION: str  # can change
+MAX_WBITS: Final[int]
+ZLIB_VERSION: Final[str]
+ZLIB_RUNTIME_VERSION: Final[str]
 Z_NO_COMPRESSION: Final = 0
 Z_PARTIAL_FLUSH: Final = 1
 Z_BEST_COMPRESSION: Final = 9
@@ -26,6 +26,10 @@ Z_RLE: Final = 3
 Z_SYNC_FLUSH: Final = 2
 Z_TREES: Final = 6
 
+if sys.version_info >= (3, 14) and sys.platform == "win32":
+    # Available when zlib was built with zlib-ng, usually only on Windows
+    ZLIBNG_VERSION: Final[str]
+
 class error(Exception): ...
 
 # This class is not exposed at runtime. It calls itself zlib.Compress.
diff --git a/mypy/typeshed/stdlib/zoneinfo/__init__.pyi b/mypy/typeshed/stdlib/zoneinfo/__init__.pyi
index 35381758a1b7..b7433f835f83 100644
--- a/mypy/typeshed/stdlib/zoneinfo/__init__.pyi
+++ b/mypy/typeshed/stdlib/zoneinfo/__init__.pyi
@@ -1,6 +1,7 @@
+import sys
 from collections.abc import Iterable
 from datetime import datetime, timedelta, tzinfo
-from typing_extensions import Self
+from typing_extensions import Self, disjoint_base
 from zoneinfo._common import ZoneInfoNotFoundError as ZoneInfoNotFoundError, _IOBytes
 from zoneinfo._tzpath import (
     TZPATH as TZPATH,
@@ -11,14 +12,20 @@ from zoneinfo._tzpath import (
 
 __all__ = ["ZoneInfo", "reset_tzpath", "available_timezones", "TZPATH", "ZoneInfoNotFoundError", "InvalidTZPathWarning"]
 
+@disjoint_base
 class ZoneInfo(tzinfo):
     @property
     def key(self) -> str: ...
     def __new__(cls, key: str) -> Self: ...
     @classmethod
     def no_cache(cls, key: str) -> Self: ...
-    @classmethod
-    def from_file(cls, fobj: _IOBytes, /, key: str | None = None) -> Self: ...
+    if sys.version_info >= (3, 12):
+        @classmethod
+        def from_file(cls, file_obj: _IOBytes, /, key: str | None = None) -> Self: ...
+    else:
+        @classmethod
+        def from_file(cls, fobj: _IOBytes, /, key: str | None = None) -> Self: ...
+
     @classmethod
     def clear_cache(cls, *, only_keys: Iterable[str] | None = None) -> None: ...
     def tzname(self, dt: datetime | None, /) -> str | None: ...
diff --git a/mypy/typeshed/stdlib/zoneinfo/_common.pyi b/mypy/typeshed/stdlib/zoneinfo/_common.pyi
index a2f29f2d14f0..e6d2d83caac1 100644
--- a/mypy/typeshed/stdlib/zoneinfo/_common.pyi
+++ b/mypy/typeshed/stdlib/zoneinfo/_common.pyi
@@ -1,6 +1,7 @@
 import io
-from typing import Any, Protocol
+from typing import Any, Protocol, type_check_only
 
+@type_check_only
 class _IOBytes(Protocol):
     def read(self, size: int, /) -> bytes: ...
     def seek(self, size: int, whence: int = ..., /) -> Any: ...
diff --git a/mypy/typeshed/stubs/mypy-native/METADATA.toml b/mypy/typeshed/stubs/mypy-native/METADATA.toml
new file mode 100644
index 000000000000..76574b01cb4b
--- /dev/null
+++ b/mypy/typeshed/stubs/mypy-native/METADATA.toml
@@ -0,0 +1 @@
+version = "0.0.*"
diff --git a/mypy/typeshed/stubs/mypy-native/native_internal.pyi b/mypy/typeshed/stubs/mypy-native/native_internal.pyi
new file mode 100644
index 000000000000..a47a4849fe20
--- /dev/null
+++ b/mypy/typeshed/stubs/mypy-native/native_internal.pyi
@@ -0,0 +1,16 @@
+from mypy_extensions import u8
+
+class Buffer:
+    def __init__(self, source: bytes = ...) -> None: ...
+    def getvalue(self) -> bytes: ...
+
+def write_bool(data: Buffer, value: bool) -> None: ...
+def read_bool(data: Buffer) -> bool: ...
+def write_str(data: Buffer, value: str) -> None: ...
+def read_str(data: Buffer) -> str: ...
+def write_float(data: Buffer, value: float) -> None: ...
+def read_float(data: Buffer) -> float: ...
+def write_int(data: Buffer, value: int) -> None: ...
+def read_int(data: Buffer) -> int: ...
+def write_tag(data: Buffer, value: u8) -> None: ...
+def read_tag(data: Buffer) -> u8: ...
diff --git a/mypy/typetraverser.py b/mypy/typetraverser.py
index cc6d4b637d2e..047c5caf6dae 100644
--- a/mypy/typetraverser.py
+++ b/mypy/typetraverser.py
@@ -67,7 +67,7 @@ def visit_param_spec(self, t: ParamSpecType, /) -> None:
         t.default.accept(self)
 
     def visit_parameters(self, t: Parameters, /) -> None:
-        self.traverse_types(t.arg_types)
+        self.traverse_type_list(t.arg_types)
 
     def visit_type_var_tuple(self, t: TypeVarTupleType, /) -> None:
         t.default.accept(self)
@@ -78,11 +78,11 @@ def visit_literal_type(self, t: LiteralType, /) -> None:
     # Composite types
 
     def visit_instance(self, t: Instance, /) -> None:
-        self.traverse_types(t.args)
+        self.traverse_type_tuple(t.args)
 
     def visit_callable_type(self, t: CallableType, /) -> None:
         # FIX generics
-        self.traverse_types(t.arg_types)
+        self.traverse_type_list(t.arg_types)
         t.ret_type.accept(self)
         t.fallback.accept(self)
 
@@ -93,7 +93,7 @@ def visit_callable_type(self, t: CallableType, /) -> None:
             t.type_is.accept(self)
 
     def visit_tuple_type(self, t: TupleType, /) -> None:
-        self.traverse_types(t.items)
+        self.traverse_type_list(t.items)
         t.partial_fallback.accept(self)
 
     def visit_typeddict_type(self, t: TypedDictType, /) -> None:
@@ -101,7 +101,7 @@ def visit_typeddict_type(self, t: TypedDictType, /) -> None:
         t.fallback.accept(self)
 
     def visit_union_type(self, t: UnionType, /) -> None:
-        self.traverse_types(t.items)
+        self.traverse_type_list(t.items)
 
     def visit_overloaded(self, t: Overloaded, /) -> None:
         self.traverse_types(t.items)
@@ -115,16 +115,16 @@ def visit_callable_argument(self, t: CallableArgument, /) -> None:
         t.typ.accept(self)
 
     def visit_unbound_type(self, t: UnboundType, /) -> None:
-        self.traverse_types(t.args)
+        self.traverse_type_tuple(t.args)
 
     def visit_type_list(self, t: TypeList, /) -> None:
-        self.traverse_types(t.items)
+        self.traverse_type_list(t.items)
 
     def visit_ellipsis_type(self, t: EllipsisType, /) -> None:
         pass
 
     def visit_placeholder_type(self, t: PlaceholderType, /) -> None:
-        self.traverse_types(t.args)
+        self.traverse_type_list(t.args)
 
     def visit_partial_type(self, t: PartialType, /) -> None:
         pass
@@ -136,7 +136,7 @@ def visit_type_alias_type(self, t: TypeAliasType, /) -> None:
         # TODO: sometimes we want to traverse target as well
         # We need to find a way to indicate explicitly the intent,
         # maybe make this method abstract (like for TypeTranslator)?
-        self.traverse_types(t.args)
+        self.traverse_type_list(t.args)
 
     def visit_unpack_type(self, t: UnpackType, /) -> None:
         t.type.accept(self)
@@ -146,3 +146,13 @@ def visit_unpack_type(self, t: UnpackType, /) -> None:
     def traverse_types(self, types: Iterable[Type], /) -> None:
         for typ in types:
             typ.accept(self)
+
+    def traverse_type_list(self, types: list[Type], /) -> None:
+        # Micro-optimization: Specialized for lists
+        for typ in types:
+            typ.accept(self)
+
+    def traverse_type_tuple(self, types: tuple[Type, ...], /) -> None:
+        # Micro-optimization: Specialized for tuples
+        for typ in types:
+            typ.accept(self)
diff --git a/mypy/version.py b/mypy/version.py
index 21d23758c6dc..fcfc04fcc40b 100644
--- a/mypy/version.py
+++ b/mypy/version.py
@@ -8,7 +8,7 @@
 # - Release versions have the form "1.2.3".
 # - Dev versions have the form "1.2.3+dev" (PLUS sign to conform to PEP 440).
 # - Before 1.0 we had the form "0.NNN".
-__version__ = "1.17.0+dev"
+__version__ = "1.18.2"
 base_version = __version__
 
 mypy_dir = os.path.abspath(os.path.dirname(os.path.dirname(__file__)))
diff --git a/mypyc/__main__.py b/mypyc/__main__.py
index 653199e0fb55..9b3973710efa 100644
--- a/mypyc/__main__.py
+++ b/mypyc/__main__.py
@@ -23,8 +23,15 @@
 from setuptools import setup
 from mypyc.build import mypycify
 
-setup(name='mypyc_output',
-      ext_modules=mypycify({}, opt_level="{}", debug_level="{}", strict_dunder_typing={}),
+setup(
+    name='mypyc_output',
+    ext_modules=mypycify(
+        {},
+        opt_level="{}",
+        debug_level="{}",
+        strict_dunder_typing={},
+        log_trace={},
+    ),
 )
 """
 
@@ -39,10 +46,17 @@ def main() -> None:
     opt_level = os.getenv("MYPYC_OPT_LEVEL", "3")
     debug_level = os.getenv("MYPYC_DEBUG_LEVEL", "1")
     strict_dunder_typing = bool(int(os.getenv("MYPYC_STRICT_DUNDER_TYPING", "0")))
+    # If enabled, compiled code writes a sampled log of executed ops (or events) to
+    # mypyc_trace.txt.
+    log_trace = bool(int(os.getenv("MYPYC_LOG_TRACE", "0")))
 
     setup_file = os.path.join(build_dir, "setup.py")
     with open(setup_file, "w") as f:
-        f.write(setup_format.format(sys.argv[1:], opt_level, debug_level, strict_dunder_typing))
+        f.write(
+            setup_format.format(
+                sys.argv[1:], opt_level, debug_level, strict_dunder_typing, log_trace
+            )
+        )
 
     # We don't use run_setup (like we do in the test suite) because it throws
     # away the error code from distutils, and we don't care about the slight
diff --git a/mypyc/analysis/attrdefined.py b/mypyc/analysis/attrdefined.py
index 896527bdcf14..1dfd33630f1c 100644
--- a/mypyc/analysis/attrdefined.py
+++ b/mypyc/analysis/attrdefined.py
@@ -138,6 +138,7 @@ def analyze_always_defined_attrs_in_class(cl: ClassIR, seen: set[ClassIR]) -> No
         or cl.builtin_base is not None
         or cl.children is None
         or cl.is_serializable()
+        or cl.has_method("__new__")
     ):
         # Give up -- we can't enforce that attributes are always defined.
         return
@@ -285,7 +286,7 @@ def mark_attr_initialization_ops(
 def attributes_initialized_by_init_call(op: Call) -> set[str]:
     """Calculate attributes that are always initialized by a super().__init__ call."""
     self_type = op.fn.sig.args[0].type
-    assert isinstance(self_type, RInstance)
+    assert isinstance(self_type, RInstance), self_type
     cl = self_type.class_ir
     return {a for base in cl.mro for a in base.attributes if base.is_always_defined(a)}
 
@@ -293,7 +294,7 @@ def attributes_initialized_by_init_call(op: Call) -> set[str]:
 def attributes_maybe_initialized_by_init_call(op: Call) -> set[str]:
     """Calculate attributes that may be initialized by a super().__init__ call."""
     self_type = op.fn.sig.args[0].type
-    assert isinstance(self_type, RInstance)
+    assert isinstance(self_type, RInstance), self_type
     cl = self_type.class_ir
     return attributes_initialized_by_init_call(op) | cl._sometimes_initialized_attrs
 
@@ -421,7 +422,7 @@ def detect_undefined_bitmap(cl: ClassIR, seen: set[ClassIR]) -> None:
         return
     seen.add(cl)
     for base in cl.base_mro[1:]:
-        detect_undefined_bitmap(cl, seen)
+        detect_undefined_bitmap(base, seen)
 
     if len(cl.base_mro) > 1:
         cl.bitmap_attrs.extend(cl.base_mro[1].bitmap_attrs)
diff --git a/mypyc/analysis/dataflow.py b/mypyc/analysis/dataflow.py
index db62ef1700fa..827c70a0eb4d 100644
--- a/mypyc/analysis/dataflow.py
+++ b/mypyc/analysis/dataflow.py
@@ -45,12 +45,14 @@
     RegisterOp,
     Return,
     SetAttr,
+    SetElement,
     SetMem,
     Truncate,
     TupleGet,
     TupleSet,
     Unborrow,
     Unbox,
+    Undef,
     Unreachable,
     Value,
 )
@@ -272,6 +274,9 @@ def visit_load_mem(self, op: LoadMem) -> GenAndKill[T]:
     def visit_get_element_ptr(self, op: GetElementPtr) -> GenAndKill[T]:
         return self.visit_register_op(op)
 
+    def visit_set_element(self, op: SetElement) -> GenAndKill[T]:
+        return self.visit_register_op(op)
+
     def visit_load_address(self, op: LoadAddress) -> GenAndKill[T]:
         return self.visit_register_op(op)
 
@@ -444,7 +449,7 @@ def visit_set_mem(self, op: SetMem) -> GenAndKill[Value]:
 def non_trivial_sources(op: Op) -> set[Value]:
     result = set()
     for source in op.sources():
-        if not isinstance(source, (Integer, Float)):
+        if not isinstance(source, (Integer, Float, Undef)):
             result.add(source)
     return result
 
diff --git a/mypyc/analysis/ircheck.py b/mypyc/analysis/ircheck.py
index 88737ac208de..6980c9cee419 100644
--- a/mypyc/analysis/ircheck.py
+++ b/mypyc/analysis/ircheck.py
@@ -17,6 +17,7 @@
     ControlOp,
     DecRef,
     Extend,
+    Float,
     FloatComparisonOp,
     FloatNeg,
     FloatOp,
@@ -42,17 +43,20 @@
     Register,
     Return,
     SetAttr,
+    SetElement,
     SetMem,
     Truncate,
     TupleGet,
     TupleSet,
     Unborrow,
     Unbox,
+    Undef,
     Unreachable,
     Value,
 )
 from mypyc.ir.pprint import format_func
 from mypyc.ir.rtypes import (
+    KNOWN_NATIVE_TYPES,
     RArray,
     RInstance,
     RPrimitive,
@@ -148,7 +152,7 @@ def check_op_sources_valid(fn: FuncIR) -> list[FnError]:
     for block in fn.blocks:
         for op in block.ops:
             for source in op.sources():
-                if isinstance(source, Integer):
+                if isinstance(source, (Integer, Float, Undef)):
                     pass
                 elif isinstance(source, Op):
                     if source not in valid_ops:
@@ -178,7 +182,7 @@ def check_op_sources_valid(fn: FuncIR) -> list[FnError]:
     set_rprimitive.name,
     tuple_rprimitive.name,
     range_rprimitive.name,
-}
+} | set(KNOWN_NATIVE_TYPES)
 
 
 def can_coerce_to(src: RType, dest: RType) -> bool:
@@ -423,6 +427,9 @@ def visit_set_mem(self, op: SetMem) -> None:
     def visit_get_element_ptr(self, op: GetElementPtr) -> None:
         pass
 
+    def visit_set_element(self, op: SetElement) -> None:
+        pass
+
     def visit_load_address(self, op: LoadAddress) -> None:
         pass
 
diff --git a/mypyc/analysis/selfleaks.py b/mypyc/analysis/selfleaks.py
index 4d3a7c87c5d1..8f46cbe3312b 100644
--- a/mypyc/analysis/selfleaks.py
+++ b/mypyc/analysis/selfleaks.py
@@ -35,6 +35,7 @@
     RegisterOp,
     Return,
     SetAttr,
+    SetElement,
     SetMem,
     Truncate,
     TupleGet,
@@ -92,7 +93,7 @@ def visit_call(self, op: Call) -> GenAndKill:
         fn = op.fn
         if fn.class_name and fn.name == "__init__":
             self_type = op.fn.sig.args[0].type
-            assert isinstance(self_type, RInstance)
+            assert isinstance(self_type, RInstance), self_type
             cl = self_type.class_ir
             if not cl.init_self_leak:
                 return CLEAN
@@ -181,6 +182,9 @@ def visit_load_mem(self, op: LoadMem) -> GenAndKill:
     def visit_get_element_ptr(self, op: GetElementPtr) -> GenAndKill:
         return CLEAN
 
+    def visit_set_element(self, op: SetElement) -> GenAndKill:
+        return CLEAN
+
     def visit_load_address(self, op: LoadAddress) -> GenAndKill:
         return CLEAN
 
diff --git a/mypyc/annotate.py b/mypyc/annotate.py
index 6736ca63c9e8..bc282fc3ea6c 100644
--- a/mypyc/annotate.py
+++ b/mypyc/annotate.py
@@ -77,6 +77,7 @@ def __init__(self, message: str, priority: int = 1) -> None:
     "PyNumber_Rshift": Annotation('Generic ">>" operation.'),
     "PyNumber_Invert": Annotation('Generic "~" operation.'),
     "PyObject_Call": Annotation("Generic call operation."),
+    "PyObject_CallObject": Annotation("Generic call operation."),
     "PyObject_RichCompare": Annotation("Generic comparison operation."),
     "PyObject_GetItem": Annotation("Generic indexing operation."),
     "PyObject_SetItem": Annotation("Generic indexed assignment."),
diff --git a/mypyc/build.py b/mypyc/build.py
index ab7ba5393614..efbd0dce31db 100644
--- a/mypyc/build.py
+++ b/mypyc/build.py
@@ -36,7 +36,7 @@
 from mypy.util import write_junit_xml
 from mypyc.annotate import generate_annotated_html
 from mypyc.codegen import emitmodule
-from mypyc.common import RUNTIME_C_FILES, shared_lib_name
+from mypyc.common import IS_FREE_THREADED, RUNTIME_C_FILES, shared_lib_name
 from mypyc.errors import Errors
 from mypyc.ir.pprint import format_modules
 from mypyc.namegen import exported_name
@@ -176,9 +176,15 @@ def generate_c_extension_shim(
     cname = "%s.c" % full_module_name.replace(".", os.sep)
     cpath = os.path.join(dir_name, cname)
 
+    if IS_FREE_THREADED:
+        # We use multi-phase init in free-threaded builds to enable free threading.
+        shim_name = "module_shim_no_gil_multiphase.tmpl"
+    else:
+        shim_name = "module_shim.tmpl"
+
     # We load the C extension shim template from a file.
     # (So that the file could be reused as a bazel template also.)
-    with open(os.path.join(include_dir(), "module_shim.tmpl")) as f:
+    with open(os.path.join(include_dir(), shim_name)) as f:
         shim_template = f.read()
 
     write_file(
@@ -270,12 +276,12 @@ def build_using_shared_lib(
 ) -> list[Extension]:
     """Produce the list of extension modules when a shared library is needed.
 
-    This creates one shared library extension module that all of the
-    others import and then one shim extension module for each
-    module in the build, that simply calls an initialization function
+    This creates one shared library extension module that all the
+    others import, and one shim extension module for each
+    module in the build. Each shim simply calls an initialization function
     in the shared library.
 
-    The shared library (which lib_name is the name of) is a python
+    The shared library (which lib_name is the name of) is a Python
     extension module that exports the real initialization functions in
     Capsules stored in module attributes.
     """
@@ -485,6 +491,9 @@ def mypycify(
     include_runtime_files: bool | None = None,
     strict_dunder_typing: bool = False,
     group_name: str | None = None,
+    log_trace: bool = False,
+    depends_on_native_internal: bool = False,
+    install_native_libs: bool = False,
 ) -> list[Extension]:
     """Main entry point to building using mypyc.
 
@@ -510,7 +519,7 @@ def mypycify(
         separate: Should compiled modules be placed in separate extension modules.
                   If False, all modules are placed in a single shared library.
                   If True, every module is placed in its own library.
-                  Otherwise separate should be a list of
+                  Otherwise, separate should be a list of
                   (file name list, optional shared library name) pairs specifying
                   groups of files that should be placed in the same shared library
                   (while all other modules will be placed in its own library).
@@ -531,6 +540,15 @@ def mypycify(
                     the hash of module names. This is used for the names of the
                     output C files and the shared library. This is only supported
                     if there is a single group. [Experimental]
+        log_trace: If True, compiled code writes a trace log of events in
+                   mypyc_trace.txt (derived from executed operations). This is
+                   useful for performance analysis, such as analyzing which
+                   primitive ops are used the most and on which lines.
+        depends_on_native_internal: This is True only for mypy itself.
+        install_native_libs: If True, also build the native extension modules. Normally,
+                             those are build and published on PyPI separately, but during
+                             tests, we want to use their development versions (i.e. from
+                             current commit).
     """
 
     # Figure out our configuration
@@ -543,6 +561,8 @@ def mypycify(
         include_runtime_files=include_runtime_files,
         strict_dunder_typing=strict_dunder_typing,
         group_name=group_name,
+        log_trace=log_trace,
+        depends_on_native_internal=depends_on_native_internal,
     )
 
     # Generate all the actual important C code
@@ -583,6 +603,8 @@ def mypycify(
             # See https://github.com/mypyc/mypyc/issues/956
             "-Wno-cpp",
         ]
+        if log_trace:
+            cflags.append("-DMYPYC_LOG_TRACE")
     elif compiler.compiler_type == "msvc":
         # msvc doesn't have levels, '/O2' is full and '/Od' is disable
         if opt_level == "0":
@@ -607,6 +629,8 @@ def mypycify(
             # that we actually get the compilation speed and memory
             # use wins that multi-file mode is intended for.
             cflags += ["/GL-", "/wd9025"]  # warning about overriding /GL
+        if log_trace:
+            cflags.append("/DMYPYC_LOG_TRACE")
 
     # If configured to (defaults to yes in multi-file mode), copy the
     # runtime library in. Otherwise it just gets #included to save on
@@ -637,4 +661,21 @@ def mypycify(
                 build_single_module(group_sources, cfilenames + shared_cfilenames, cflags)
             )
 
+    if install_native_libs:
+        for name in ["native_internal.c"] + RUNTIME_C_FILES:
+            rt_file = os.path.join(build_dir, name)
+            with open(os.path.join(include_dir(), name), encoding="utf-8") as f:
+                write_file(rt_file, f.read())
+        extensions.append(
+            get_extension()(
+                "native_internal",
+                sources=[
+                    os.path.join(build_dir, file)
+                    for file in ["native_internal.c"] + RUNTIME_C_FILES
+                ],
+                include_dirs=[include_dir()],
+                extra_compile_args=cflags,
+            )
+        )
+
     return extensions
diff --git a/mypyc/codegen/emit.py b/mypyc/codegen/emit.py
index d7d7d9c7abda..4ef53296ef0d 100644
--- a/mypyc/codegen/emit.py
+++ b/mypyc/codegen/emit.py
@@ -28,8 +28,7 @@
     RType,
     RUnion,
     int_rprimitive,
-    is_bit_rprimitive,
-    is_bool_rprimitive,
+    is_bool_or_bit_rprimitive,
     is_bytes_rprimitive,
     is_dict_rprimitive,
     is_fixed_width_rtype,
@@ -40,6 +39,7 @@
     is_int64_rprimitive,
     is_int_rprimitive,
     is_list_rprimitive,
+    is_native_rprimitive,
     is_none_rprimitive,
     is_object_rprimitive,
     is_optional_type,
@@ -615,8 +615,7 @@ def emit_cast(
             or is_range_rprimitive(typ)
             or is_float_rprimitive(typ)
             or is_int_rprimitive(typ)
-            or is_bool_rprimitive(typ)
-            or is_bit_rprimitive(typ)
+            or is_bool_or_bit_rprimitive(typ)
             or is_fixed_width_rtype(typ)
         ):
             if declare_dest:
@@ -638,7 +637,7 @@ def emit_cast(
             elif is_int_rprimitive(typ) or is_fixed_width_rtype(typ):
                 # TODO: Range check for fixed-width types?
                 prefix = "PyLong"
-            elif is_bool_rprimitive(typ) or is_bit_rprimitive(typ):
+            elif is_bool_or_bit_rprimitive(typ):
                 prefix = "PyBool"
             else:
                 assert False, f"unexpected primitive type: {typ}"
@@ -706,7 +705,7 @@ def emit_cast(
             self.emit_lines(f"    {dest} = {src};", "else {")
             self.emit_cast_error_handler(error, src, dest, typ, raise_exception)
             self.emit_line("}")
-        elif is_object_rprimitive(typ):
+        elif is_object_rprimitive(typ) or is_native_rprimitive(typ):
             if declare_dest:
                 self.emit_line(f"PyObject *{dest};")
             self.emit_arg_check(src, dest, typ, "", optional)
@@ -744,7 +743,7 @@ def emit_cast_error_handler(
             self.emit_traceback(error.source_path, error.module_name, error.traceback_entry)
             self.emit_line("goto %s;" % error.label)
         else:
-            assert isinstance(error, ReturnHandler)
+            assert isinstance(error, ReturnHandler), error
             self.emit_line("return %s;" % error.value)
 
     def emit_union_cast(
@@ -873,7 +872,7 @@ def emit_unbox(
         elif isinstance(error, GotoHandler):
             failure = "goto %s;" % error.label
         else:
-            assert isinstance(error, ReturnHandler)
+            assert isinstance(error, ReturnHandler), error
             failure = "return %s;" % error.value
         if raise_exception:
             raise_exc = f'CPy_TypeError("{self.pretty_name(typ)}", {src}); '
@@ -889,7 +888,7 @@ def emit_unbox(
             self.emit_line("else {")
             self.emit_line(failure)
             self.emit_line("}")
-        elif is_bool_rprimitive(typ) or is_bit_rprimitive(typ):
+        elif is_bool_or_bit_rprimitive(typ):
             # Whether we are borrowing or not makes no difference.
             if declare_dest:
                 self.emit_line(f"char {dest};")
@@ -1015,7 +1014,7 @@ def emit_box(
         if is_int_rprimitive(typ) or is_short_int_rprimitive(typ):
             # Steal the existing reference if it exists.
             self.emit_line(f"{declaration}{dest} = CPyTagged_StealAsObject({src});")
-        elif is_bool_rprimitive(typ) or is_bit_rprimitive(typ):
+        elif is_bool_or_bit_rprimitive(typ):
             # N.B: bool is special cased to produce a borrowed value
             # after boxing, so we don't need to increment the refcount
             # when this comes directly from a Box op.
@@ -1037,17 +1036,21 @@ def emit_box(
             self.emit_line(f"{declaration}{dest} = PyFloat_FromDouble({src});")
         elif isinstance(typ, RTuple):
             self.declare_tuple_struct(typ)
-            self.emit_line(f"{declaration}{dest} = PyTuple_New({len(typ.types)});")
-            self.emit_line(f"if (unlikely({dest} == NULL))")
-            self.emit_line("    CPyError_OutOfMemory();")
-            # TODO: Fail if dest is None
-            for i in range(len(typ.types)):
-                if not typ.is_unboxed:
-                    self.emit_line(f"PyTuple_SET_ITEM({dest}, {i}, {src}.f{i}")
-                else:
-                    inner_name = self.temp_name()
-                    self.emit_box(f"{src}.f{i}", inner_name, typ.types[i], declare_dest=True)
-                    self.emit_line(f"PyTuple_SET_ITEM({dest}, {i}, {inner_name});")
+            if not typ.types:
+                self.emit_line(f"{declaration}{dest} = CPyTuple_LoadEmptyTupleConstant();")
+            else:
+                self.emit_line(f"{declaration}{dest} = PyTuple_New({len(typ.types)});")
+                self.emit_line(f"if (unlikely({dest} == NULL))")
+                self.emit_line("    CPyError_OutOfMemory();")
+
+                # TODO: Fail if dest is None
+                for i in range(len(typ.types)):
+                    if not typ.is_unboxed:
+                        self.emit_line(f"PyTuple_SET_ITEM({dest}, {i}, {src}.f{i}")
+                    else:
+                        inner_name = self.temp_name()
+                        self.emit_box(f"{src}.f{i}", inner_name, typ.types[i], declare_dest=True)
+                        self.emit_line(f"PyTuple_SET_ITEM({dest}, {i}, {inner_name});")
         else:
             assert not typ.is_unboxed
             # Type is boxed -- trivially just assign.
@@ -1115,6 +1118,31 @@ def emit_gc_clear(self, target: str, rtype: RType) -> None:
         else:
             assert False, "emit_gc_clear() not implemented for %s" % repr(rtype)
 
+    def emit_reuse_clear(self, target: str, rtype: RType) -> None:
+        """Emit attribute clear before object is added into freelist.
+
+        Assume that 'target' represents a C expression that refers to a
+        struct member, such as 'self->x'.
+
+        Unlike emit_gc_clear(), initialize attribute value to match a freshly
+        allocated object.
+        """
+        if isinstance(rtype, RTuple):
+            for i, item_type in enumerate(rtype.types):
+                self.emit_reuse_clear(f"{target}.f{i}", item_type)
+        elif not rtype.is_refcounted:
+            self.emit_line(f"{target} = {rtype.c_undefined};")
+        elif isinstance(rtype, RPrimitive) and rtype.name == "builtins.int":
+            self.emit_line(f"if (CPyTagged_CheckLong({target})) {{")
+            self.emit_line(f"CPyTagged __tmp = {target};")
+            self.emit_line(f"{target} = {self.c_undefined_value(rtype)};")
+            self.emit_line("Py_XDECREF(CPyTagged_LongAsObject(__tmp));")
+            self.emit_line("} else {")
+            self.emit_line(f"{target} = {self.c_undefined_value(rtype)};")
+            self.emit_line("}")
+        else:
+            self.emit_gc_clear(target, rtype)
+
     def emit_traceback(
         self, source_path: str, module_name: str, traceback_entry: tuple[str, int]
     ) -> None:
diff --git a/mypyc/codegen/emitclass.py b/mypyc/codegen/emitclass.py
index da3d14f9dafe..0931c849131d 100644
--- a/mypyc/codegen/emitclass.py
+++ b/mypyc/codegen/emitclass.py
@@ -5,8 +5,10 @@
 from collections.abc import Mapping
 from typing import Callable
 
+from mypy.nodes import ARG_STAR, ARG_STAR2
+from mypyc.codegen.cstring import c_string_initializer
 from mypyc.codegen.emit import Emitter, HeaderDeclaration, ReturnHandler
-from mypyc.codegen.emitfunc import native_function_header
+from mypyc.codegen.emitfunc import native_function_doc_initializer, native_function_header
 from mypyc.codegen.emitwrapper import (
     generate_bin_op_wrapper,
     generate_bool_wrapper,
@@ -21,7 +23,13 @@
 )
 from mypyc.common import BITMAP_BITS, BITMAP_TYPE, NATIVE_PREFIX, PREFIX, REG_PREFIX
 from mypyc.ir.class_ir import ClassIR, VTableEntries
-from mypyc.ir.func_ir import FUNC_CLASSMETHOD, FUNC_STATICMETHOD, FuncDecl, FuncIR
+from mypyc.ir.func_ir import (
+    FUNC_CLASSMETHOD,
+    FUNC_STATICMETHOD,
+    FuncDecl,
+    FuncIR,
+    get_text_signature,
+)
 from mypyc.ir.rtypes import RTuple, RType, object_rprimitive
 from mypyc.namegen import NameGenerator
 from mypyc.sametype import is_same_type
@@ -186,6 +194,29 @@ def generate_class_type_decl(
         )
 
 
+def generate_class_reuse(
+    cl: ClassIR, c_emitter: Emitter, external_emitter: Emitter, emitter: Emitter
+) -> None:
+    """Generate a definition of a single-object per-class free "list".
+
+    This speeds up object allocation and freeing when there are many short-lived
+    objects.
+
+    TODO: Generalize to support a free list with up to N objects.
+    """
+    assert cl.reuse_freed_instance
+
+    # The free list implementation doesn't support class hierarchies
+    assert cl.is_final_class or cl.children == []
+
+    context = c_emitter.context
+    name = cl.name_prefix(c_emitter.names) + "_free_instance"
+    struct_name = cl.struct_name(c_emitter.names)
+    context.declarations[name] = HeaderDeclaration(
+        f"CPyThreadLocal {struct_name} *{name};", needs_export=True
+    )
+
+
 def generate_class(cl: ClassIR, module: str, emitter: Emitter) -> None:
     """Generate C code for a class.
 
@@ -194,7 +225,7 @@ def generate_class(cl: ClassIR, module: str, emitter: Emitter) -> None:
     name = cl.name
     name_prefix = cl.name_prefix(emitter.names)
 
-    setup_name = f"{name_prefix}_setup"
+    setup_name = emitter.native_function_name(cl.setup)
     new_name = f"{name_prefix}_new"
     finalize_name = f"{name_prefix}_finalize"
     members_name = f"{name_prefix}_members"
@@ -287,10 +318,8 @@ def emit_line() -> None:
         fields["tp_basicsize"] = base_size
 
     if generate_full:
-        # Declare setup method that allocates and initializes an object. type is the
-        # type of the class being initialized, which could be another class if there
-        # is an interpreted subclass.
-        emitter.emit_line(f"static PyObject *{setup_name}(PyTypeObject *type);")
+        assert cl.setup is not None
+        emitter.emit_line(native_function_header(cl.setup, emitter) + ";")
         assert cl.ctor is not None
         emitter.emit_line(native_function_header(cl.ctor, emitter) + ";")
 
@@ -345,6 +374,8 @@ def emit_line() -> None:
         flags.append("Py_TPFLAGS_MANAGED_DICT")
     fields["tp_flags"] = " | ".join(flags)
 
+    fields["tp_doc"] = f"PyDoc_STR({native_class_doc_initializer(cl)})"
+
     emitter.emit_line(f"static PyTypeObject {emitter.type_struct_name(cl)}_template_ = {{")
     emitter.emit_line("PyVarObject_HEAD_INIT(NULL, 0)")
     for field, value in fields.items():
@@ -358,9 +389,7 @@ def emit_line() -> None:
 
     emitter.emit_line()
     if generate_full:
-        generate_setup_for_class(
-            cl, setup_name, defaults_fn, vtable_name, shadow_vtable_name, emitter
-        )
+        generate_setup_for_class(cl, defaults_fn, vtable_name, shadow_vtable_name, emitter)
         emitter.emit_line()
         generate_constructor_for_class(cl, cl.ctor, init_fn, setup_name, vtable_name, emitter)
         emitter.emit_line()
@@ -547,17 +576,32 @@ def generate_vtable(
 
 def generate_setup_for_class(
     cl: ClassIR,
-    func_name: str,
     defaults_fn: FuncIR | None,
     vtable_name: str,
     shadow_vtable_name: str | None,
     emitter: Emitter,
 ) -> None:
     """Generate a native function that allocates an instance of a class."""
-    emitter.emit_line("static PyObject *")
-    emitter.emit_line(f"{func_name}(PyTypeObject *type)")
+    emitter.emit_line(native_function_header(cl.setup, emitter))
     emitter.emit_line("{")
-    emitter.emit_line(f"{cl.struct_name(emitter.names)} *self;")
+    type_arg_name = REG_PREFIX + cl.setup.sig.args[0].name
+    emitter.emit_line(f"PyTypeObject *type = (PyTypeObject*){type_arg_name};")
+    struct_name = cl.struct_name(emitter.names)
+    emitter.emit_line(f"{struct_name} *self;")
+
+    prefix = cl.name_prefix(emitter.names)
+    if cl.reuse_freed_instance:
+        # Attempt to use a per-type free list first (a free "list" with up to one object only).
+        emitter.emit_line(f"if ({prefix}_free_instance != NULL) {{")
+        emitter.emit_line(f"self = {prefix}_free_instance;")
+        emitter.emit_line(f"{prefix}_free_instance = NULL;")
+        emitter.emit_line("Py_SET_REFCNT(self, 1);")
+        emitter.emit_line("PyObject_GC_Track(self);")
+        if defaults_fn is not None:
+            emit_attr_defaults_func_call(defaults_fn, "self", emitter)
+        emitter.emit_line("return (PyObject *)self;")
+        emitter.emit_line("}")
+
     emitter.emit_line(f"self = ({cl.struct_name(emitter.names)} *)type->tp_alloc(type, 0);")
     emitter.emit_line("if (self == NULL)")
     emitter.emit_line("    return NULL;")
@@ -571,9 +615,7 @@ def generate_setup_for_class(
     else:
         emitter.emit_line(f"self->vtable = {vtable_name};")
 
-    for i in range(0, len(cl.bitmap_attrs), BITMAP_BITS):
-        field = emitter.bitmap_field(i)
-        emitter.emit_line(f"self->{field} = 0;")
+    emit_clear_bitmaps(cl, emitter)
 
     if cl.has_method("__call__"):
         name = cl.method_decl("__call__").cname(emitter.names)
@@ -590,19 +632,63 @@ def generate_setup_for_class(
 
     # Initialize attributes to default values, if necessary
     if defaults_fn is not None:
-        emitter.emit_lines(
-            "if ({}{}((PyObject *)self) == 0) {{".format(
-                NATIVE_PREFIX, defaults_fn.cname(emitter.names)
-            ),
-            "Py_DECREF(self);",
-            "return NULL;",
-            "}",
-        )
+        emit_attr_defaults_func_call(defaults_fn, "self", emitter)
 
     emitter.emit_line("return (PyObject *)self;")
     emitter.emit_line("}")
 
 
+def emit_clear_bitmaps(cl: ClassIR, emitter: Emitter) -> None:
+    """Emit C code to clear bitmaps that track if attributes have an assigned value."""
+    for i in range(0, len(cl.bitmap_attrs), BITMAP_BITS):
+        field = emitter.bitmap_field(i)
+        emitter.emit_line(f"self->{field} = 0;")
+
+
+def emit_attr_defaults_func_call(defaults_fn: FuncIR, self_name: str, emitter: Emitter) -> None:
+    """Emit C code to initialize attribute defaults by calling defaults_fn.
+
+    The code returns NULL on a raised exception.
+    """
+    emitter.emit_lines(
+        "if ({}{}((PyObject *){}) == 0) {{".format(
+            NATIVE_PREFIX, defaults_fn.cname(emitter.names), self_name
+        ),
+        "Py_DECREF(self);",
+        "return NULL;",
+        "}",
+    )
+
+
+def emit_setup_or_dunder_new_call(
+    cl: ClassIR,
+    setup_name: str,
+    type_arg: str,
+    native_prefix: bool,
+    new_args: str,
+    emitter: Emitter,
+) -> None:
+    def emit_null_check() -> None:
+        emitter.emit_line("if (self == NULL)")
+        emitter.emit_line("    return NULL;")
+
+    new_fn = cl.get_method("__new__")
+    if not new_fn:
+        emitter.emit_line(f"PyObject *self = {setup_name}({type_arg});")
+        emit_null_check()
+        return
+    prefix = emitter.get_group_prefix(new_fn.decl) + NATIVE_PREFIX if native_prefix else PREFIX
+    all_args = type_arg
+    if new_args != "":
+        all_args += ", " + new_args
+    emitter.emit_line(f"PyObject *self = {prefix}{new_fn.cname(emitter.names)}({all_args});")
+    emit_null_check()
+
+    # skip __init__ if __new__ returns some other type
+    emitter.emit_line(f"if (Py_TYPE(self) != {emitter.type_struct_name(cl)})")
+    emitter.emit_line("    return self;")
+
+
 def generate_constructor_for_class(
     cl: ClassIR,
     fn: FuncDecl,
@@ -614,17 +700,30 @@ def generate_constructor_for_class(
     """Generate a native function that allocates and initializes an instance of a class."""
     emitter.emit_line(f"{native_function_header(fn, emitter)}")
     emitter.emit_line("{")
-    emitter.emit_line(f"PyObject *self = {setup_name}({emitter.type_struct_name(cl)});")
-    emitter.emit_line("if (self == NULL)")
-    emitter.emit_line("    return NULL;")
-    args = ", ".join(["self"] + [REG_PREFIX + arg.name for arg in fn.sig.args])
+
+    fn_args = [REG_PREFIX + arg.name for arg in fn.sig.args]
+    type_arg = "(PyObject *)" + emitter.type_struct_name(cl)
+    new_args = ", ".join(fn_args)
+
+    use_wrapper = (
+        cl.has_method("__new__")
+        and len(fn.sig.args) == 2
+        and fn.sig.args[0].kind == ARG_STAR
+        and fn.sig.args[1].kind == ARG_STAR2
+    )
+    emit_setup_or_dunder_new_call(cl, setup_name, type_arg, not use_wrapper, new_args, emitter)
+
+    args = ", ".join(["self"] + fn_args)
     if init_fn is not None:
+        prefix = PREFIX if use_wrapper else NATIVE_PREFIX
+        cast = "!= NULL ? 0 : -1" if use_wrapper else ""
         emitter.emit_line(
-            "char res = {}{}{}({});".format(
+            "char res = {}{}{}({}){};".format(
                 emitter.get_group_prefix(init_fn.decl),
-                NATIVE_PREFIX,
+                prefix,
                 init_fn.cname(emitter.names),
                 args,
+                cast,
             )
         )
         emitter.emit_line("if (res == 2) {")
@@ -657,7 +756,7 @@ def generate_init_for_class(cl: ClassIR, init_fn: FuncIR, emitter: Emitter) -> s
     emitter.emit_line("static int")
     emitter.emit_line(f"{func_name}(PyObject *self, PyObject *args, PyObject *kwds)")
     emitter.emit_line("{")
-    if cl.allow_interpreted_subclasses or cl.builtin_base:
+    if cl.allow_interpreted_subclasses or cl.builtin_base or cl.has_method("__new__"):
         emitter.emit_line(
             "return {}{}(self, args, kwds) != NULL ? 0 : -1;".format(
                 PREFIX, init_fn.cname(emitter.names)
@@ -690,15 +789,22 @@ def generate_new_for_class(
         emitter.emit_line("return NULL;")
         emitter.emit_line("}")
 
-    if not init_fn or cl.allow_interpreted_subclasses or cl.builtin_base or cl.is_serializable():
+    type_arg = "(PyObject*)type"
+    new_args = "args, kwds"
+    emit_setup_or_dunder_new_call(cl, setup_name, type_arg, False, new_args, emitter)
+    if (
+        not init_fn
+        or cl.allow_interpreted_subclasses
+        or cl.builtin_base
+        or cl.is_serializable()
+        or cl.has_method("__new__")
+    ):
         # Match Python semantics -- __new__ doesn't call __init__.
-        emitter.emit_line(f"return {setup_name}(type);")
+        emitter.emit_line("return self;")
     else:
         # __new__ of a native class implicitly calls __init__ so that we
         # can enforce that instances are always properly initialized. This
         # is needed to support always defined attributes.
-        emitter.emit_line(f"PyObject *self = {setup_name}(type);")
-        emitter.emit_lines("if (self == NULL)", "    return NULL;")
         emitter.emit_line(
             f"PyObject *ret = {PREFIX}{init_fn.cname(emitter.names)}(self, args, kwds);"
         )
@@ -787,6 +893,8 @@ def generate_dealloc_for_class(
         emitter.emit_line("Py_TYPE(self)->tp_finalize((PyObject *)self);")
         emitter.emit_line("}")
     emitter.emit_line("PyObject_GC_UnTrack(self);")
+    if cl.reuse_freed_instance:
+        emit_reuse_dealloc(cl, emitter)
     # The trashcan is needed to handle deep recursive deallocations
     emitter.emit_line(f"CPy_TRASHCAN_BEGIN(self, {dealloc_func_name})")
     emitter.emit_line(f"{clear_func_name}(self);")
@@ -795,6 +903,27 @@ def generate_dealloc_for_class(
     emitter.emit_line("}")
 
 
+def emit_reuse_dealloc(cl: ClassIR, emitter: Emitter) -> None:
+    """Emit code to deallocate object by putting it to per-type free list.
+
+    The free "list" currently can have up to one object.
+    """
+    prefix = cl.name_prefix(emitter.names)
+    emitter.emit_line(f"if ({prefix}_free_instance == NULL) {{")
+    emitter.emit_line(f"{prefix}_free_instance = self;")
+
+    # Clear attributes and free referenced objects.
+
+    emit_clear_bitmaps(cl, emitter)
+
+    for base in reversed(cl.base_mro):
+        for attr, rtype in base.attributes.items():
+            emitter.emit_reuse_clear(f"self->{emitter.attr(attr)}", rtype)
+
+    emitter.emit_line("return;")
+    emitter.emit_line("}")
+
+
 def generate_finalize_for_class(
     del_method: FuncIR, finalize_func_name: str, emitter: Emitter
 ) -> None:
@@ -841,7 +970,8 @@ def generate_methods_table(cl: ClassIR, name: str, emitter: Emitter) -> None:
         elif fn.decl.kind == FUNC_CLASSMETHOD:
             flags.append("METH_CLASS")
 
-        emitter.emit_line(" {}, NULL}},".format(" | ".join(flags)))
+        doc = native_function_doc_initializer(fn)
+        emitter.emit_line(" {}, PyDoc_STR({})}},".format(" | ".join(flags), doc))
 
     # Provide a default __getstate__ and __setstate__
     if not cl.has_method("__setstate__") and not cl.has_method("__getstate__"):
@@ -1099,3 +1229,16 @@ def has_managed_dict(cl: ClassIR, emitter: Emitter) -> bool:
         and cl.has_dict
         and cl.builtin_base != "PyBaseExceptionObject"
     )
+
+
+def native_class_doc_initializer(cl: ClassIR) -> str:
+    init_fn = cl.get_method("__init__")
+    if init_fn is not None:
+        text_sig = get_text_signature(init_fn, bound=True)
+        if text_sig is None:
+            return "NULL"
+        text_sig = text_sig.replace("__init__", cl.name, 1)
+    else:
+        text_sig = f"{cl.name}()"
+    docstring = f"{text_sig}\n--\n\n"
+    return c_string_initializer(docstring.encode("ascii", errors="backslashreplace"))
diff --git a/mypyc/codegen/emitfunc.py b/mypyc/codegen/emitfunc.py
index c854516825af..a1e18353693e 100644
--- a/mypyc/codegen/emitfunc.py
+++ b/mypyc/codegen/emitfunc.py
@@ -5,8 +5,10 @@
 from typing import Final
 
 from mypyc.analysis.blockfreq import frequently_executed_blocks
+from mypyc.codegen.cstring import c_string_initializer
 from mypyc.codegen.emit import DEBUG_ERRORS, Emitter, TracebackAndGotoHandler, c_array_initializer
 from mypyc.common import (
+    GENERATOR_ATTRIBUTE_PREFIX,
     HAVE_IMMORTAL,
     MODULE_PREFIX,
     NATIVE_PREFIX,
@@ -16,7 +18,14 @@
     TYPE_VAR_PREFIX,
 )
 from mypyc.ir.class_ir import ClassIR
-from mypyc.ir.func_ir import FUNC_CLASSMETHOD, FUNC_STATICMETHOD, FuncDecl, FuncIR, all_values
+from mypyc.ir.func_ir import (
+    FUNC_CLASSMETHOD,
+    FUNC_STATICMETHOD,
+    FuncDecl,
+    FuncIR,
+    all_values,
+    get_text_signature,
+)
 from mypyc.ir.ops import (
     ERR_FALSE,
     NAMESPACE_MODULE,
@@ -33,6 +42,7 @@
     Cast,
     ComparisonOp,
     ControlOp,
+    CString,
     DecRef,
     Extend,
     Float,
@@ -61,12 +71,14 @@
     Register,
     Return,
     SetAttr,
+    SetElement,
     SetMem,
     Truncate,
     TupleGet,
     TupleSet,
     Unborrow,
     Unbox,
+    Undef,
     Unreachable,
     Value,
 )
@@ -77,7 +89,7 @@
     RStruct,
     RTuple,
     RType,
-    is_bool_rprimitive,
+    is_bool_or_bit_rprimitive,
     is_int32_rprimitive,
     is_int64_rprimitive,
     is_int_rprimitive,
@@ -105,6 +117,14 @@ def native_function_header(fn: FuncDecl, emitter: Emitter) -> str:
     )
 
 
+def native_function_doc_initializer(func: FuncIR) -> str:
+    text_sig = get_text_signature(func)
+    if text_sig is None:
+        return "NULL"
+    docstring = f"{text_sig}\n--\n\n"
+    return c_string_initializer(docstring.encode("ascii", errors="backslashreplace"))
+
+
 def generate_native_function(
     fn: FuncIR, emitter: Emitter, source_path: str, module_name: str
 ) -> None:
@@ -143,7 +163,7 @@ def generate_native_function(
     # eliminated during code generation.
     for block in fn.blocks:
         terminator = block.terminator
-        assert isinstance(terminator, ControlOp)
+        assert isinstance(terminator, ControlOp), terminator
 
         for target in terminator.targets():
             is_next_block = target.label == block.label + 1
@@ -209,6 +229,16 @@ def visit_goto(self, op: Goto) -> None:
         if op.label is not self.next_block:
             self.emit_line("goto %s;" % self.label(op.label))
 
+    def error_value_check(self, value: Value, compare: str) -> str:
+        typ = value.type
+        if isinstance(typ, RTuple):
+            # TODO: What about empty tuple?
+            return self.emitter.tuple_undefined_check_cond(
+                typ, self.reg(value), self.c_error_value, compare
+            )
+        else:
+            return f"{self.reg(value)} {compare} {self.c_error_value(typ)}"
+
     def visit_branch(self, op: Branch) -> None:
         true, false = op.true, op.false
         negated = op.negated
@@ -225,15 +255,8 @@ def visit_branch(self, op: Branch) -> None:
             expr_result = self.reg(op.value)
             cond = f"{neg}{expr_result}"
         elif op.op == Branch.IS_ERROR:
-            typ = op.value.type
             compare = "!=" if negated else "=="
-            if isinstance(typ, RTuple):
-                # TODO: What about empty tuple?
-                cond = self.emitter.tuple_undefined_check_cond(
-                    typ, self.reg(op.value), self.c_error_value, compare
-                )
-            else:
-                cond = f"{self.reg(op.value)} {compare} {self.c_error_value(typ)}"
+            cond = self.error_value_check(op.value, compare)
         else:
             assert False, "Invalid branch"
 
@@ -289,7 +312,7 @@ def visit_assign(self, op: Assign) -> None:
 
     def visit_assign_multi(self, op: AssignMulti) -> None:
         typ = op.dest.type
-        assert isinstance(typ, RArray)
+        assert isinstance(typ, RArray), typ
         dest = self.reg(op.dest)
         # RArray values can only be assigned to once, so we can always
         # declare them on initialization.
@@ -358,6 +381,9 @@ def get_attr_expr(self, obj: str, op: GetAttr | SetAttr, decl_cl: ClassIR) -> st
             return f"({cast}{obj})->{self.emitter.attr(op.attr)}"
 
     def visit_get_attr(self, op: GetAttr) -> None:
+        if op.allow_error_value:
+            self.get_attr_with_allow_error_value(op)
+            return
         dest = self.reg(op)
         obj = self.reg(op.obj)
         rtype = op.class_type
@@ -411,7 +437,9 @@ def visit_get_attr(self, op: GetAttr) -> None:
                     exc_class = "PyExc_AttributeError"
                     self.emitter.emit_line(
                         'PyErr_SetString({}, "attribute {} of {} undefined");'.format(
-                            exc_class, repr(op.attr), repr(cl.name)
+                            exc_class,
+                            repr(op.attr.removeprefix(GENERATOR_ATTRIBUTE_PREFIX)),
+                            repr(cl.name),
                         )
                     )
 
@@ -426,6 +454,28 @@ def visit_get_attr(self, op: GetAttr) -> None:
             elif not always_defined:
                 self.emitter.emit_line("}")
 
+    def get_attr_with_allow_error_value(self, op: GetAttr) -> None:
+        """Handle GetAttr with allow_error_value=True.
+
+        This allows NULL or other error value without raising AttributeError.
+        """
+        dest = self.reg(op)
+        obj = self.reg(op.obj)
+        rtype = op.class_type
+        cl = rtype.class_ir
+        attr_rtype, decl_cl = cl.attr_details(op.attr)
+
+        # Direct struct access without NULL check
+        attr_expr = self.get_attr_expr(obj, op, decl_cl)
+        self.emitter.emit_line(f"{dest} = {attr_expr};")
+
+        # Only emit inc_ref if not NULL
+        if attr_rtype.is_refcounted and not op.is_borrowed:
+            check = self.error_value_check(op, "!=")
+            self.emitter.emit_line(f"if ({check}) {{")
+            self.emitter.emit_inc_ref(dest, attr_rtype)
+            self.emitter.emit_line("}")
+
     def next_branch(self) -> Branch | None:
         if self.op_index + 1 < len(self.ops):
             next_op = self.ops[self.op_index + 1]
@@ -541,7 +591,7 @@ def visit_method_call(self, op: MethodCall) -> None:
     def emit_method_call(self, dest: str, op_obj: Value, name: str, op_args: list[Value]) -> None:
         obj = self.reg(op_obj)
         rtype = op_obj.type
-        assert isinstance(rtype, RInstance)
+        assert isinstance(rtype, RInstance), rtype
         class_ir = rtype.class_ir
         method = rtype.class_ir.get_method(name)
         assert method is not None
@@ -583,7 +633,7 @@ def emit_method_call(self, dest: str, op_obj: Value, name: str, op_args: list[Va
     def visit_inc_ref(self, op: IncRef) -> None:
         if (
             isinstance(op.src, Box)
-            and (is_none_rprimitive(op.src.src.type) or is_bool_rprimitive(op.src.src.type))
+            and (is_none_rprimitive(op.src.src.type) or is_bool_or_bit_rprimitive(op.src.src.type))
             and HAVE_IMMORTAL
         ):
             # On Python 3.12+, None/True/False are immortal, and we can skip inc ref
@@ -607,6 +657,9 @@ def visit_box(self, op: Box) -> None:
         self.emitter.emit_box(self.reg(op.src), self.reg(op), op.src.type, can_borrow=True)
 
     def visit_cast(self, op: Cast) -> None:
+        if op.is_unchecked and op.is_borrowed:
+            self.emit_line(f"{self.reg(op)} = {self.reg(op.src)};")
+            return
         branch = self.next_branch()
         handler = None
         if branch is not None:
@@ -746,6 +799,8 @@ def visit_load_mem(self, op: LoadMem) -> None:
         # TODO: we shouldn't dereference to type that are pointer type so far
         type = self.ctype(op.type)
         self.emit_line(f"{dest} = *({type} *){src};")
+        if not op.is_borrowed:
+            self.emit_inc_ref(dest, op.type)
 
     def visit_set_mem(self, op: SetMem) -> None:
         dest = self.reg(op.dest)
@@ -760,7 +815,7 @@ def visit_get_element_ptr(self, op: GetElementPtr) -> None:
         dest = self.reg(op)
         src = self.reg(op.src)
         # TODO: support tuple type
-        assert isinstance(op.src_type, RStruct)
+        assert isinstance(op.src_type, RStruct), op.src_type
         assert op.field in op.src_type.names, "Invalid field name."
         self.emit_line(
             "{} = ({})&(({} *){})->{};".format(
@@ -768,6 +823,31 @@ def visit_get_element_ptr(self, op: GetElementPtr) -> None:
             )
         )
 
+    def visit_set_element(self, op: SetElement) -> None:
+        dest = self.reg(op)
+        item = self.reg(op.item)
+        field = op.field
+        if isinstance(op.src, Undef):
+            # First assignment to an undefined struct is trivial.
+            self.emit_line(f"{dest}.{field} = {item};")
+        else:
+            # In the general case create a copy of the struct with a single
+            # item modified.
+            #
+            # TODO: Can we do better if only a subset of fields are initialized?
+            # TODO: Make this less verbose in the common case
+            # TODO: Support tuples (or use RStruct for tuples)?
+            src = self.reg(op.src)
+            src_type = op.src.type
+            assert isinstance(src_type, RStruct), src_type
+            init_items = []
+            for n in src_type.names:
+                if n != field:
+                    init_items.append(f"{src}.{n}")
+                else:
+                    init_items.append(item)
+            self.emit_line(f"{dest} = ({self.ctype(src_type)}) {{ {', '.join(init_items)} }};")
+
     def visit_load_address(self, op: LoadAddress) -> None:
         typ = op.type
         dest = self.reg(op)
@@ -822,6 +902,8 @@ def reg(self, reg: Value) -> str:
             elif r == "nan":
                 return "NAN"
             return r
+        elif isinstance(reg, CString):
+            return '"' + encode_c_string_literal(reg.value) + '"'
         else:
             return self.emitter.reg(reg)
 
@@ -862,7 +944,7 @@ def emit_attribute_error(self, op: Branch, class_name: str, attr: str) -> None:
                 self.source_path.replace("\\", "\\\\"),
                 op.traceback_entry[0],
                 class_name,
-                attr,
+                attr.removeprefix(GENERATOR_ATTRIBUTE_PREFIX),
                 op.traceback_entry[1],
                 globals_static,
             )
@@ -883,3 +965,30 @@ def emit_unsigned_int_cast(self, type: RType) -> str:
             return "(uint64_t)"
         else:
             return ""
+
+
+_translation_table: Final[dict[int, str]] = {}
+
+
+def encode_c_string_literal(b: bytes) -> str:
+    """Convert bytestring to the C string literal syntax (with necessary escaping).
+
+    For example, b'foo\n' gets converted to 'foo\\n' (note that double quotes are not added).
+    """
+    if not _translation_table:
+        # Initialize the translation table on the first call.
+        d = {
+            ord("\n"): "\\n",
+            ord("\r"): "\\r",
+            ord("\t"): "\\t",
+            ord('"'): '\\"',
+            ord("\\"): "\\\\",
+        }
+        for i in range(256):
+            if i not in d:
+                if i < 32 or i >= 127:
+                    d[i] = "\\x%.2x" % i
+                else:
+                    d[i] = chr(i)
+        _translation_table.update(str.maketrans(d))
+    return b.decode("latin1").translate(_translation_table)
diff --git a/mypyc/codegen/emitmodule.py b/mypyc/codegen/emitmodule.py
index f914bfd6345d..ca5db52ab7da 100644
--- a/mypyc/codegen/emitmodule.py
+++ b/mypyc/codegen/emitmodule.py
@@ -1,7 +1,7 @@
 """Generate C code for a Python C extension module from Python source code."""
 
 # FIXME: Basically nothing in this file operates on the level of a
-# single module and it should be renamed.
+#        single module and it should be renamed.
 
 from __future__ import annotations
 
@@ -29,8 +29,12 @@
 from mypy.util import hash_digest, json_dumps
 from mypyc.codegen.cstring import c_string_initializer
 from mypyc.codegen.emit import Emitter, EmitterContext, HeaderDeclaration, c_array_initializer
-from mypyc.codegen.emitclass import generate_class, generate_class_type_decl
-from mypyc.codegen.emitfunc import generate_native_function, native_function_header
+from mypyc.codegen.emitclass import generate_class, generate_class_reuse, generate_class_type_decl
+from mypyc.codegen.emitfunc import (
+    generate_native_function,
+    native_function_doc_initializer,
+    native_function_header,
+)
 from mypyc.codegen.emitwrapper import (
     generate_legacy_wrapper_function,
     generate_wrapper_function,
@@ -61,12 +65,13 @@
 from mypyc.transform.copy_propagation import do_copy_propagation
 from mypyc.transform.exceptions import insert_exception_handling
 from mypyc.transform.flag_elimination import do_flag_elimination
+from mypyc.transform.log_trace import insert_event_trace_logging
 from mypyc.transform.lower import lower_ir
 from mypyc.transform.refcount import insert_ref_count_opcodes
 from mypyc.transform.spill import insert_spills
 from mypyc.transform.uninit import insert_uninit_checks
 
-# All of the modules being compiled are divided into "groups". A group
+# All the modules being compiled are divided into "groups". A group
 # is a set of modules that are placed into the same shared library.
 # Two common configurations are that every module is placed in a group
 # by itself (fully separate compilation) and that every module is
@@ -159,7 +164,7 @@ def report_config_data(self, ctx: ReportConfigContext) -> tuple[str | None, list
         if hash_digest(meta_json) != ir_data["meta_hash"]:
             return None
 
-        # Check that all of the source files are present and as
+        # Check that all the source files are present and as
         # expected. The main situation where this would come up is the
         # user deleting the build directory without deleting
         # .mypy_cache, which we should handle gracefully.
@@ -210,8 +215,8 @@ def compile_scc_to_ir(
 ) -> ModuleIRs:
     """Compile an SCC into ModuleIRs.
 
-    Any modules that this SCC depends on must have either compiled or
-    loaded from a cache into mapper.
+    Any modules that this SCC depends on must have either been compiled,
+    type checked, or loaded from a cache into mapper.
 
     Arguments:
         scc: The list of MypyFiles to compile
@@ -239,16 +244,19 @@ def compile_scc_to_ir(
 
     for module in modules.values():
         for fn in module.functions:
-            # Insert uninit checks.
+            # Insert checks for uninitialized values.
             insert_uninit_checks(fn)
             # Insert exception handling.
             insert_exception_handling(fn)
-            # Insert refcount handling.
+            # Insert reference count handling.
             insert_ref_count_opcodes(fn)
 
             if fn in env_user_functions:
                 insert_spills(fn, env_user_functions[fn])
 
+            if compiler_options.log_trace:
+                insert_event_trace_logging(fn, compiler_options)
+
             # Switch to lower abstraction level IR.
             lower_ir(fn, compiler_options)
             # Perform optimizations.
@@ -361,7 +369,7 @@ def write_cache(
         cache are in sync and refer to the same version of the code.
         This is particularly important if mypyc crashes/errors/is
         stopped after mypy has written its cache but before mypyc has.
-      * The hashes of all of the source file outputs for the group
+      * The hashes of all the source file outputs for the group
         the module is in. This is so that the module will be
         recompiled if the source outputs are missing.
     """
@@ -421,7 +429,7 @@ def compile_modules_to_c(
     Each shared library module provides, for each module in its group,
     a PyCapsule containing an initialization function.
     Additionally, it provides a capsule containing an export table of
-    pointers to all of the group's functions and static variables.
+    pointers to all the group's functions and static variables.
 
     Arguments:
         result: The BuildResult from the mypy front-end
@@ -496,7 +504,7 @@ def __init__(
 
         The code for a compilation group contains an internal and an
         external .h file, and then one .c if not in multi_file mode or
-        one .c file per module if in multi_file mode.)
+        one .c file per module if in multi_file mode.
 
         Arguments:
             modules: (name, ir) pairs for each module in the group
@@ -504,8 +512,7 @@ def __init__(
             group_name: The name of the group (or None if this is single-module compilation)
             group_map: A map of modules to their group names
             names: The name generator for the compilation
-            multi_file: Whether to put each module in its own source file regardless
-                        of group structure.
+            compiler_options: Mypyc specific options, including multi_file mode
         """
         self.modules = modules
         self.source_paths = source_paths
@@ -594,6 +601,8 @@ def generate_c_for_modules(self) -> list[tuple[str, str]]:
         ext_declarations.emit_line(f"#define MYPYC_NATIVE{self.group_suffix}_H")
         ext_declarations.emit_line("#include <Python.h>")
         ext_declarations.emit_line("#include <CPy.h>")
+        if self.compiler_options.depends_on_native_internal:
+            ext_declarations.emit_line("#include <native_internal.h>")
 
         declarations = Emitter(self.context)
         declarations.emit_line(f"#ifndef MYPYC_NATIVE_INTERNAL{self.group_suffix}_H")
@@ -609,6 +618,8 @@ def generate_c_for_modules(self) -> list[tuple[str, str]]:
             self.declare_finals(module_name, module.final_names, declarations)
             for cl in module.classes:
                 generate_class_type_decl(cl, emitter, ext_declarations, declarations)
+                if cl.reuse_freed_instance:
+                    generate_class_reuse(cl, emitter, ext_declarations, declarations)
             self.declare_type_vars(module_name, module.type_var_names, declarations)
             for fn in module.functions:
                 generate_function_declaration(fn, declarations)
@@ -632,7 +643,7 @@ def generate_c_for_modules(self) -> list[tuple[str, str]]:
             decls = ext_declarations if declaration.is_type else declarations
             if not declaration.is_type:
                 decls.emit_lines(f"extern {declaration.decl[0]}", *declaration.decl[1:])
-                # If there is a definition, emit it. Otherwise repeat the declaration
+                # If there is a definition, emit it. Otherwise, repeat the declaration
                 # (without an extern).
                 if declaration.defn:
                     emitter.emit_lines(*declaration.defn)
@@ -642,7 +653,8 @@ def generate_c_for_modules(self) -> list[tuple[str, str]]:
                 decls.emit_lines(*declaration.decl)
 
         if self.group_name:
-            self.generate_export_table(ext_declarations, emitter)
+            if self.compiler_options.separate:
+                self.generate_export_table(ext_declarations, emitter)
 
             self.generate_shared_lib_init(emitter)
 
@@ -760,13 +772,13 @@ def generate_export_table(self, decl_emitter: Emitter, code_emitter: Emitter) ->
     def generate_shared_lib_init(self, emitter: Emitter) -> None:
         """Generate the init function for a shared library.
 
-        A shared library contains all of the actual code for a
+        A shared library contains all the actual code for a
         compilation group.
 
         The init function is responsible for creating Capsules that
         wrap pointers to the initialization function of all the real
         init functions for modules in this shared library as well as
-        the export table containing all of the exported functions and
+        the export table containing all the exported functions and
         values from all the modules.
 
         These capsules are stored in attributes of the shared library.
@@ -774,57 +786,56 @@ def generate_shared_lib_init(self, emitter: Emitter) -> None:
         assert self.group_name is not None
 
         emitter.emit_line()
+
+        short_name = shared_lib_name(self.group_name).split(".")[-1]
+
         emitter.emit_lines(
-            "PyMODINIT_FUNC PyInit_{}(void)".format(
-                shared_lib_name(self.group_name).split(".")[-1]
-            ),
+            f"static int exec_{short_name}(PyObject *module)",
             "{",
-            (
-                'static PyModuleDef def = {{ PyModuleDef_HEAD_INIT, "{}", NULL, -1, NULL, NULL }};'.format(
-                    shared_lib_name(self.group_name)
-                )
-            ),
             "int res;",
             "PyObject *capsule;",
             "PyObject *tmp;",
-            "static PyObject *module;",
-            "if (module) {",
-            "Py_INCREF(module);",
-            "return module;",
-            "}",
-            "module = PyModule_Create(&def);",
-            "if (!module) {",
-            "goto fail;",
-            "}",
             "",
         )
 
-        emitter.emit_lines(
-            'capsule = PyCapsule_New(&exports, "{}.exports", NULL);'.format(
-                shared_lib_name(self.group_name)
-            ),
-            "if (!capsule) {",
-            "goto fail;",
-            "}",
-            'res = PyObject_SetAttrString(module, "exports", capsule);',
-            "Py_DECREF(capsule);",
-            "if (res < 0) {",
-            "goto fail;",
-            "}",
-            "",
-        )
+        if self.compiler_options.separate:
+            emitter.emit_lines(
+                'capsule = PyCapsule_New(&exports, "{}.exports", NULL);'.format(
+                    shared_lib_name(self.group_name)
+                ),
+                "if (!capsule) {",
+                "goto fail;",
+                "}",
+                'res = PyObject_SetAttrString(module, "exports", capsule);',
+                "Py_DECREF(capsule);",
+                "if (res < 0) {",
+                "goto fail;",
+                "}",
+                "",
+            )
 
         for mod in self.modules:
             name = exported_name(mod)
+            if self.multi_phase_init:
+                capsule_func_prefix = "CPyExec_"
+                capsule_name_prefix = "exec_"
+                emitter.emit_line(f"extern int CPyExec_{name}(PyObject *);")
+            else:
+                capsule_func_prefix = "CPyInit_"
+                capsule_name_prefix = "init_"
+                emitter.emit_line(f"extern PyObject *CPyInit_{name}(void);")
             emitter.emit_lines(
-                f"extern PyObject *CPyInit_{name}(void);",
-                'capsule = PyCapsule_New((void *)CPyInit_{}, "{}.init_{}", NULL);'.format(
-                    name, shared_lib_name(self.group_name), name
+                'capsule = PyCapsule_New((void *){}{}, "{}.{}{}", NULL);'.format(
+                    capsule_func_prefix,
+                    name,
+                    shared_lib_name(self.group_name),
+                    capsule_name_prefix,
+                    name,
                 ),
                 "if (!capsule) {",
                 "goto fail;",
                 "}",
-                f'res = PyObject_SetAttrString(module, "init_{name}", capsule);',
+                f'res = PyObject_SetAttrString(module, "{capsule_name_prefix}{name}", capsule);',
                 "Py_DECREF(capsule);",
                 "if (res < 0) {",
                 "goto fail;",
@@ -850,7 +861,56 @@ def generate_shared_lib_init(self, emitter: Emitter) -> None:
                 "",
             )
 
-        emitter.emit_lines("return module;", "fail:", "Py_XDECREF(module);", "return NULL;", "}")
+        emitter.emit_lines("return 0;", "fail:", "return -1;", "}")
+
+        if self.multi_phase_init:
+            emitter.emit_lines(
+                f"static PyModuleDef_Slot slots_{short_name}[] = {{",
+                f"{{Py_mod_exec, exec_{short_name}}},",
+                "{Py_mod_multiple_interpreters, Py_MOD_MULTIPLE_INTERPRETERS_NOT_SUPPORTED},",
+                "{Py_mod_gil, Py_MOD_GIL_NOT_USED},",
+                "{0, NULL},",
+                "};",
+            )
+
+        size = 0 if self.multi_phase_init else -1
+        emitter.emit_lines(
+            f"static PyModuleDef module_def_{short_name} = {{",
+            "PyModuleDef_HEAD_INIT,",
+            f'.m_name = "{shared_lib_name(self.group_name)}",',
+            ".m_doc = NULL,",
+            f".m_size = {size},",
+            ".m_methods = NULL,",
+        )
+        if self.multi_phase_init:
+            emitter.emit_line(f".m_slots = slots_{short_name},")
+        emitter.emit_line("};")
+
+        if self.multi_phase_init:
+            emitter.emit_lines(
+                f"PyMODINIT_FUNC PyInit_{short_name}(void) {{",
+                f"return PyModuleDef_Init(&module_def_{short_name});",
+                "}",
+            )
+        else:
+            emitter.emit_lines(
+                f"PyMODINIT_FUNC PyInit_{short_name}(void) {{",
+                "static PyObject *module = NULL;",
+                "if (module) {",
+                "Py_INCREF(module);",
+                "return module;",
+                "}",
+                f"module = PyModule_Create(&module_def_{short_name});",
+                "if (!module) {",
+                "return NULL;",
+                "}",
+                f"if (exec_{short_name}(module) < 0) {{",
+                "Py_DECREF(module);",
+                "return NULL;",
+                "}",
+                "return module;",
+                "}",
+            )
 
     def generate_globals_init(self, emitter: Emitter) -> None:
         emitter.emit_lines(
@@ -876,16 +936,22 @@ def generate_globals_init(self, emitter: Emitter) -> None:
     def generate_module_def(self, emitter: Emitter, module_name: str, module: ModuleIR) -> None:
         """Emit the PyModuleDef struct for a module and the module init function."""
         module_prefix = emitter.names.private_name(module_name)
-        self.emit_module_exec_func(emitter, module_name, module_prefix, module)
-        if self.multi_phase_init:
-            self.emit_module_def_slots(emitter, module_prefix)
         self.emit_module_methods(emitter, module_name, module_prefix, module)
-        self.emit_module_def_struct(emitter, module_name, module_prefix)
-        self.emit_module_init_func(emitter, module_name, module_prefix)
+        self.emit_module_exec_func(emitter, module_name, module_prefix, module)
+
+        # If using multi-phase init and a shared lib, parts of module definition
+        # will happen in the shim modules, so we skip some steps here.
+        if not (self.multi_phase_init and self.use_shared_lib):
+            if self.multi_phase_init:
+                self.emit_module_def_slots(emitter, module_prefix, module_name)
+            self.emit_module_def_struct(emitter, module_name, module_prefix)
+            self.emit_module_init_func(emitter, module_name, module_prefix)
 
-    def emit_module_def_slots(self, emitter: Emitter, module_prefix: str) -> None:
+    def emit_module_def_slots(
+        self, emitter: Emitter, module_prefix: str, module_name: str
+    ) -> None:
         name = f"{module_prefix}_slots"
-        exec_name = f"{module_prefix}_exec"
+        exec_name = f"CPyExec_{exported_name(module_name)}"
 
         emitter.emit_line(f"static PyModuleDef_Slot {name}[] = {{")
         emitter.emit_line(f"{{Py_mod_exec, {exec_name}}},")
@@ -915,11 +981,14 @@ def emit_module_methods(
                 flag = "METH_FASTCALL"
             else:
                 flag = "METH_VARARGS"
+            doc = native_function_doc_initializer(fn)
             emitter.emit_line(
                 (
                     '{{"{name}", (PyCFunction){prefix}{cname}, {flag} | METH_KEYWORDS, '
-                    "NULL /* docstring */}},"
-                ).format(name=name, cname=fn.cname(emitter.names), prefix=PREFIX, flag=flag)
+                    "PyDoc_STR({doc}) /* docstring */}},"
+                ).format(
+                    name=name, cname=fn.cname(emitter.names), prefix=PREFIX, flag=flag, doc=doc
+                )
             )
         emitter.emit_line("{NULL, NULL, 0, NULL}")
         emitter.emit_line("};")
@@ -937,7 +1006,7 @@ def emit_module_def_struct(
             "0,       /* size of per-interpreter state of the module */",
             f"{module_prefix}module_methods,",
         )
-        if self.multi_phase_init:
+        if self.multi_phase_init and not self.use_shared_lib:
             slots_name = f"{module_prefix}_slots"
             emitter.emit_line(f"{slots_name}, /* m_slots */")
         else:
@@ -948,17 +1017,22 @@ def emit_module_def_struct(
     def emit_module_exec_func(
         self, emitter: Emitter, module_name: str, module_prefix: str, module: ModuleIR
     ) -> None:
-        """Emit the module init function.
+        """Emit the module exec function.
 
-        If we are compiling just one module, this will be the C API init
-        function. If we are compiling 2+ modules, we generate a shared
+        If we are compiling just one module, this will be the normal C API
+        exec function. If we are compiling 2+ modules, we generate a shared
         library for the modules and shims that call into the shared
-        library, and in this case we use an internal module initialized
-        function that will be called by the shim.
+        library, and in this case the shared module defines an internal
+        exec function for each module and these will be called by the shims
+        via Capsules.
         """
-        declaration = f"static int {module_prefix}_exec(PyObject *module)"
+        declaration = f"int CPyExec_{exported_name(module_name)}(PyObject *module)"
         module_static = self.module_internal_static_name(module_name, emitter)
         emitter.emit_lines(declaration, "{")
+        if self.compiler_options.depends_on_native_internal:
+            emitter.emit_line("if (import_native_internal() < 0) {")
+            emitter.emit_line("return -1;")
+            emitter.emit_line("}")
         emitter.emit_line("PyObject* modname = NULL;")
         if self.multi_phase_init:
             emitter.emit_line(f"{module_static} = module;")
@@ -973,6 +1047,12 @@ def emit_module_exec_func(
             "    goto fail;",
         )
 
+        if self.multi_phase_init:
+            emitter.emit_lines(
+                f"if (PyModule_AddFunctions(module, {module_prefix}module_methods) < 0)",
+                "    goto fail;",
+            )
+
         # HACK: Manually instantiate generated classes here
         type_structs: list[str] = []
         for cl in module.classes:
@@ -1024,7 +1104,7 @@ def emit_module_init_func(
             emitter.emit_line("}")
             return
 
-        exec_func = f"{module_prefix}_exec"
+        exec_func = f"CPyExec_{exported_name(module_name)}"
 
         # Store the module reference in a static and return it when necessary.
         # This is separate from the *global* reference to the module that will
@@ -1113,7 +1193,7 @@ def declare_internal_globals(self, module_name: str, emitter: Emitter) -> None:
         self.declare_global("PyObject *", static_name)
 
     def module_internal_static_name(self, module_name: str, emitter: Emitter) -> str:
-        return emitter.static_name(module_name + "_internal", None, prefix=MODULE_PREFIX)
+        return emitter.static_name(module_name + "__internal", None, prefix=MODULE_PREFIX)
 
     def declare_module(self, module_name: str, emitter: Emitter) -> None:
         # We declare two globals for each compiled module:
@@ -1194,8 +1274,8 @@ def is_fastcall_supported(fn: FuncIR, capi_version: tuple[int, int]) -> bool:
         if fn.name == "__call__":
             # We can use vectorcalls (PEP 590) when supported
             return True
-        # TODO: Support fastcall for __init__.
-        return fn.name != "__init__"
+        # TODO: Support fastcall for __init__ and __new__.
+        return fn.name != "__init__" and fn.name != "__new__"
     return True
 
 
diff --git a/mypyc/codegen/emitwrapper.py b/mypyc/codegen/emitwrapper.py
index cd1684255855..2e5d7efa4e98 100644
--- a/mypyc/codegen/emitwrapper.py
+++ b/mypyc/codegen/emitwrapper.py
@@ -238,7 +238,7 @@ def generate_legacy_wrapper_function(
     real_args = list(fn.args)
     if fn.sig.num_bitmap_args:
         real_args = real_args[: -fn.sig.num_bitmap_args]
-    if fn.class_name and fn.decl.kind != FUNC_STATICMETHOD:
+    if fn.class_name and (fn.decl.name == "__new__" or fn.decl.kind != FUNC_STATICMETHOD):
         arg = real_args.pop(0)
         emitter.emit_line(f"PyObject *obj_{arg.name} = self;")
 
diff --git a/mypyc/common.py b/mypyc/common.py
index b5506eed89c2..2de63c09bb2c 100644
--- a/mypyc/common.py
+++ b/mypyc/common.py
@@ -15,6 +15,7 @@
 MODULE_PREFIX: Final = "CPyModule_"  # Cached modules
 TYPE_VAR_PREFIX: Final = "CPyTypeVar_"  # Type variables when using new-style Python 3.12 syntax
 ATTR_PREFIX: Final = "_"  # Attributes
+FAST_PREFIX: Final = "__mypyc_fast_"  # Optimized methods in non-extension classes
 
 ENV_ATTR_NAME: Final = "__mypyc_env__"
 NEXT_LABEL_ATTR_NAME: Final = "__mypyc_next_label__"
@@ -22,6 +23,7 @@
 LAMBDA_NAME: Final = "__mypyc_lambda__"
 PROPSET_PREFIX: Final = "__mypyc_setter__"
 SELF_NAME: Final = "__mypyc_self__"
+GENERATOR_ATTRIBUTE_PREFIX: Final = "__mypyc_generator_attribute__"
 
 # Max short int we accept as a literal is based on 32-bit platforms,
 # so that we can just always emit the same code.
diff --git a/mypyc/doc/differences_from_python.rst b/mypyc/doc/differences_from_python.rst
index 65ad709677af..b910e3b3c929 100644
--- a/mypyc/doc/differences_from_python.rst
+++ b/mypyc/doc/differences_from_python.rst
@@ -316,7 +316,9 @@ non-exhaustive list of what won't work:
 - Instance ``__annotations__`` is usually not kept
 - Frames of compiled functions can't be inspected using ``inspect``
 - Compiled methods aren't considered methods by ``inspect.ismethod``
-- ``inspect.signature`` chokes on compiled functions
+- ``inspect.signature`` chokes on compiled functions with default arguments that
+  are not simple literals
+- ``inspect.iscoroutinefunction`` and ``asyncio.iscoroutinefunction`` will always return False for compiled functions, even those defined with `async def`
 
 Profiling hooks and tracing
 ***************************
diff --git a/mypyc/ir/class_ir.py b/mypyc/ir/class_ir.py
index c88b9b0c7afc..0a56aaf5d101 100644
--- a/mypyc/ir/class_ir.py
+++ b/mypyc/ir/class_ir.py
@@ -5,9 +5,9 @@
 from typing import NamedTuple
 
 from mypyc.common import PROPSET_PREFIX, JsonDict
-from mypyc.ir.func_ir import FuncDecl, FuncIR, FuncSignature
+from mypyc.ir.func_ir import FuncDecl, FuncIR, FuncSignature, RuntimeArg
 from mypyc.ir.ops import DeserMaps, Value
-from mypyc.ir.rtypes import RInstance, RType, deserialize_type
+from mypyc.ir.rtypes import RInstance, RType, deserialize_type, object_rprimitive
 from mypyc.namegen import NameGenerator, exported_name
 
 # Some notes on the vtable layout: Each concrete class has a vtable
@@ -133,6 +133,16 @@ def __init__(
         self.builtin_base: str | None = None
         # Default empty constructor
         self.ctor = FuncDecl(name, None, module_name, FuncSignature([], RInstance(self)))
+        # Declare setup method that allocates and initializes an object. type is the
+        # type of the class being initialized, which could be another class if there
+        # is an interpreted subclass.
+        # TODO: Make it a regular method and generate its body in IR
+        self.setup = FuncDecl(
+            "__mypyc__" + name + "_setup",
+            None,
+            module_name,
+            FuncSignature([RuntimeArg("type", object_rprimitive)], RInstance(self)),
+        )
         # Attributes defined in the class (not inherited)
         self.attributes: dict[str, RType] = {}
         # Deletable attributes
@@ -204,6 +214,15 @@ def __init__(
         # If this is a generator environment class, what is the actual method for it
         self.env_user_function: FuncIR | None = None
 
+        # If True, keep one freed, cleared instance available for immediate reuse to
+        # speed up allocations. This helps if many objects are freed quickly, before
+        # other instances of the same class are allocated. This is effectively a
+        # per-type free "list" of up to length 1.
+        self.reuse_freed_instance = False
+
+        # Is this a class inheriting from enum.Enum? Such classes can be special-cased.
+        self.is_enum = False
+
     def __repr__(self) -> str:
         return (
             "ClassIR("
@@ -403,6 +422,8 @@ def serialize(self) -> JsonDict:
             "_sometimes_initialized_attrs": sorted(self._sometimes_initialized_attrs),
             "init_self_leak": self.init_self_leak,
             "env_user_function": self.env_user_function.id if self.env_user_function else None,
+            "reuse_freed_instance": self.reuse_freed_instance,
+            "is_enum": self.is_enum,
         }
 
     @classmethod
@@ -458,6 +479,8 @@ def deserialize(cls, data: JsonDict, ctx: DeserMaps) -> ClassIR:
         ir.env_user_function = (
             ctx.functions[data["env_user_function"]] if data["env_user_function"] else None
         )
+        ir.reuse_freed_instance = data["reuse_freed_instance"]
+        ir.is_enum = data["is_enum"]
 
         return ir
 
diff --git a/mypyc/ir/func_ir.py b/mypyc/ir/func_ir.py
index beef8def7f43..881ac5939c27 100644
--- a/mypyc/ir/func_ir.py
+++ b/mypyc/ir/func_ir.py
@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import inspect
 from collections.abc import Sequence
 from typing import Final
 
@@ -11,13 +12,24 @@
     Assign,
     AssignMulti,
     BasicBlock,
+    Box,
     ControlOp,
     DeserMaps,
+    Float,
+    Integer,
     LoadAddress,
+    LoadLiteral,
     Register,
+    TupleSet,
     Value,
 )
-from mypyc.ir.rtypes import RType, bitmap_rprimitive, deserialize_type
+from mypyc.ir.rtypes import (
+    RType,
+    bitmap_rprimitive,
+    deserialize_type,
+    is_bool_rprimitive,
+    is_none_rprimitive,
+)
 from mypyc.namegen import NameGenerator
 
 
@@ -379,3 +391,85 @@ def all_values_full(args: list[Register], blocks: list[BasicBlock]) -> list[Valu
                     values.append(op)
 
     return values
+
+
+_ARG_KIND_TO_INSPECT: Final = {
+    ArgKind.ARG_POS: inspect.Parameter.POSITIONAL_OR_KEYWORD,
+    ArgKind.ARG_OPT: inspect.Parameter.POSITIONAL_OR_KEYWORD,
+    ArgKind.ARG_STAR: inspect.Parameter.VAR_POSITIONAL,
+    ArgKind.ARG_NAMED: inspect.Parameter.KEYWORD_ONLY,
+    ArgKind.ARG_STAR2: inspect.Parameter.VAR_KEYWORD,
+    ArgKind.ARG_NAMED_OPT: inspect.Parameter.KEYWORD_ONLY,
+}
+
+# Sentinel indicating a value that cannot be represented in a text signature.
+_NOT_REPRESENTABLE = object()
+
+
+def get_text_signature(fn: FuncIR, *, bound: bool = False) -> str | None:
+    """Return a text signature in CPython's internal doc format, or None
+    if the function's signature cannot be represented.
+    """
+    parameters = []
+    mark_self = (fn.class_name is not None) and (fn.decl.kind != FUNC_STATICMETHOD) and not bound
+    sig = fn.decl.bound_sig if bound and fn.decl.bound_sig is not None else fn.decl.sig
+    # Pre-scan for end of positional-only parameters.
+    # This is needed to handle signatures like 'def foo(self, __x)', where mypy
+    # currently sees 'self' as being positional-or-keyword and '__x' as positional-only.
+    pos_only_idx = -1
+    for idx, arg in enumerate(sig.args):
+        if arg.pos_only and arg.kind in (ArgKind.ARG_POS, ArgKind.ARG_OPT):
+            pos_only_idx = idx
+    for idx, arg in enumerate(sig.args):
+        if arg.name.startswith(("__bitmap", "__mypyc")):
+            continue
+        kind = (
+            inspect.Parameter.POSITIONAL_ONLY
+            if idx <= pos_only_idx
+            else _ARG_KIND_TO_INSPECT[arg.kind]
+        )
+        default: object = inspect.Parameter.empty
+        if arg.optional:
+            default = _find_default_argument(arg.name, fn.blocks)
+            if default is _NOT_REPRESENTABLE:
+                # This default argument cannot be represented in a __text_signature__
+                return None
+
+        curr_param = inspect.Parameter(arg.name, kind, default=default)
+        parameters.append(curr_param)
+        if mark_self:
+            # Parameter.__init__/Parameter.replace do not accept $
+            curr_param._name = f"${arg.name}"  # type: ignore[attr-defined]
+            mark_self = False
+    return f"{fn.name}{inspect.Signature(parameters)}"
+
+
+def _find_default_argument(name: str, blocks: list[BasicBlock]) -> object:
+    # Find assignment inserted by gen_arg_defaults. Assumed to be the first assignment.
+    for block in blocks:
+        for op in block.ops:
+            if isinstance(op, Assign) and op.dest.name == name:
+                return _extract_python_literal(op.src)
+    return _NOT_REPRESENTABLE
+
+
+def _extract_python_literal(value: Value) -> object:
+    if isinstance(value, Integer):
+        if is_none_rprimitive(value.type):
+            return None
+        val = value.numeric_value()
+        if is_bool_rprimitive(value.type):
+            return bool(val)
+        return val
+    elif isinstance(value, Float):
+        return value.value
+    elif isinstance(value, LoadLiteral):
+        return value.value
+    elif isinstance(value, Box):
+        return _extract_python_literal(value.src)
+    elif isinstance(value, TupleSet):
+        items = tuple(_extract_python_literal(item) for item in value.items)
+        if any(itm is _NOT_REPRESENTABLE for itm in items):
+            return _NOT_REPRESENTABLE
+        return items
+    return _NOT_REPRESENTABLE
diff --git a/mypyc/ir/ops.py b/mypyc/ir/ops.py
index eec9c34a965e..4b3b5eb3c8ca 100644
--- a/mypyc/ir/ops.py
+++ b/mypyc/ir/ops.py
@@ -3,32 +3,47 @@
 Opcodes operate on abstract values (Value) in a register machine. Each
 value has a type (RType). A value can hold various things, such as:
 
-- local variables (Register)
+- local variables or temporaries (Register)
 - intermediate values of expressions (RegisterOp subclasses)
 - condition flags (true/false)
 - literals (integer literals, True, False, etc.)
+
+NOTE: As a convention, we don't create subclasses of concrete Value/Op
+      subclasses (e.g. you shouldn't define a subclass of Integer, which
+      is a concrete class).
+
+      If you want to introduce a variant of an existing class, you'd
+      typically add an attribute (e.g. a flag) to an existing concrete
+      class to enable the new behavior. Sometimes adding a new abstract
+      base class is also an option, or just creating a new subclass
+      without any inheritance relationship (some duplication of code
+      is preferred over introducing complex implementation inheritance).
+
+      This makes it possible to use isinstance(x, <concrete Value
+      subclass>) checks without worrying about potential subclasses.
 """
 
 from __future__ import annotations
 
 from abc import abstractmethod
 from collections.abc import Sequence
-from typing import TYPE_CHECKING, Final, Generic, NamedTuple, TypeVar, Union
+from typing import TYPE_CHECKING, Final, Generic, NamedTuple, TypeVar, Union, final
 
 from mypy_extensions import trait
 
 from mypyc.ir.rtypes import (
     RArray,
     RInstance,
+    RStruct,
     RTuple,
     RType,
     RVoid,
     bit_rprimitive,
     bool_rprimitive,
+    cstring_rprimitive,
     float_rprimitive,
     int_rprimitive,
-    is_bit_rprimitive,
-    is_bool_rprimitive,
+    is_bool_or_bit_rprimitive,
     is_int_rprimitive,
     is_none_rprimitive,
     is_pointer_rprimitive,
@@ -47,6 +62,7 @@
 T = TypeVar("T")
 
 
+@final
 class BasicBlock:
     """IR basic block.
 
@@ -142,6 +158,7 @@ def is_void(self) -> bool:
         return isinstance(self.type, RVoid)
 
 
+@final
 class Register(Value):
     """A Register holds a value of a specific type, and it can be read and mutated.
 
@@ -168,6 +185,7 @@ def __repr__(self) -> str:
         return f"<Register {self.name!r} at {hex(id(self))}>"
 
 
+@final
 class Integer(Value):
     """Short integer literal.
 
@@ -198,6 +216,7 @@ def numeric_value(self) -> int:
         return self.value
 
 
+@final
 class Float(Value):
     """Float literal.
 
@@ -212,6 +231,40 @@ def __init__(self, value: float, line: int = -1) -> None:
         self.line = line
 
 
+@final
+class CString(Value):
+    """C string literal (zero-terminated).
+
+    You can also include zero values in the value, but then you'll need to track
+    the length of the string separately.
+    """
+
+    def __init__(self, value: bytes, line: int = -1) -> None:
+        self.value = value
+        self.type = cstring_rprimitive
+        self.line = line
+
+
+@final
+class Undef(Value):
+    """An undefined value.
+
+    Use Undef() as the initial value followed by one or more SetElement
+    ops to initialize a struct. Pseudocode example:
+
+      r0 = set_element undef MyStruct, "field1", f1
+      r1 = set_element r0, "field2", f2
+      # r1 now has new struct value with two fields set
+
+    Warning: Always initialize undefined values before using them,
+    as otherwise the values are garbage. You shouldn't expect that
+    undefined values are zeroed, in particular.
+    """
+
+    def __init__(self, rtype: RType) -> None:
+        self.type = rtype
+
+
 class Op(Value):
     """Abstract base class for all IR operations.
 
@@ -257,13 +310,14 @@ def accept(self, visitor: OpVisitor[T]) -> T:
 
 
 class BaseAssign(Op):
-    """Base class for ops that assign to a register."""
+    """Abstract base class for ops that assign to a register."""
 
     def __init__(self, dest: Register, line: int = -1) -> None:
         super().__init__(line)
         self.dest = dest
 
 
+@final
 class Assign(BaseAssign):
     """Assign a value to a Register (dest = src)."""
 
@@ -286,6 +340,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_assign(self)
 
 
+@final
 class AssignMulti(BaseAssign):
     """Assign multiple values to a Register (dest = src1, src2, ...).
 
@@ -320,7 +375,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
 
 
 class ControlOp(Op):
-    """Control flow operation."""
+    """Abstract base class for control flow operations."""
 
     def targets(self) -> Sequence[BasicBlock]:
         """Get all basic block targets of the control operation."""
@@ -331,6 +386,7 @@ def set_target(self, i: int, new: BasicBlock) -> None:
         raise AssertionError(f"Invalid set_target({self}, {i})")
 
 
+@final
 class Goto(ControlOp):
     """Unconditional jump."""
 
@@ -360,6 +416,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_goto(self)
 
 
+@final
 class Branch(ControlOp):
     """Branch based on a value.
 
@@ -426,6 +483,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_branch(self)
 
 
+@final
 class Return(ControlOp):
     """Return a value from a function."""
 
@@ -455,6 +513,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_return(self)
 
 
+@final
 class Unreachable(ControlOp):
     """Mark the end of basic block as unreachable.
 
@@ -511,6 +570,7 @@ def can_raise(self) -> bool:
         return self.error_kind != ERR_NEVER
 
 
+@final
 class IncRef(RegisterOp):
     """Increase reference count (inc_ref src)."""
 
@@ -531,6 +591,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_inc_ref(self)
 
 
+@final
 class DecRef(RegisterOp):
     """Decrease reference count and free object if zero (dec_ref src).
 
@@ -559,6 +620,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_dec_ref(self)
 
 
+@final
 class Call(RegisterOp):
     """Native call f(arg, ...).
 
@@ -587,6 +649,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_call(self)
 
 
+@final
 class MethodCall(RegisterOp):
     """Native method call obj.method(arg, ...)"""
 
@@ -618,6 +681,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_method_call(self)
 
 
+@final
 class PrimitiveDescription:
     """Description of a primitive op.
 
@@ -670,6 +734,7 @@ def __repr__(self) -> str:
         return f"<PrimitiveDescription {self.name!r}: {self.arg_types}>"
 
 
+@final
 class PrimitiveOp(RegisterOp):
     """A higher-level primitive operation.
 
@@ -707,6 +772,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_primitive_op(self)
 
 
+@final
 class LoadErrorValue(RegisterOp):
     """Load an error value.
 
@@ -737,6 +803,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_load_error_value(self)
 
 
+@final
 class LoadLiteral(RegisterOp):
     """Load a Python literal object (dest = 'foo' / b'foo' / ...).
 
@@ -772,20 +839,32 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_load_literal(self)
 
 
+@final
 class GetAttr(RegisterOp):
     """obj.attr (for a native object)"""
 
     error_kind = ERR_MAGIC
 
-    def __init__(self, obj: Value, attr: str, line: int, *, borrow: bool = False) -> None:
+    def __init__(
+        self,
+        obj: Value,
+        attr: str,
+        line: int,
+        *,
+        borrow: bool = False,
+        allow_error_value: bool = False,
+    ) -> None:
         super().__init__(line)
         self.obj = obj
         self.attr = attr
+        self.allow_error_value = allow_error_value
         assert isinstance(obj.type, RInstance), "Attribute access not supported: %s" % obj.type
         self.class_type = obj.type
         attr_type = obj.type.attr_type(attr)
         self.type = attr_type
-        if attr_type.error_overlap:
+        if allow_error_value:
+            self.error_kind = ERR_NEVER
+        elif attr_type.error_overlap:
             self.error_kind = ERR_MAGIC_OVERLAPPING
         self.is_borrowed = borrow and attr_type.is_refcounted
 
@@ -799,6 +878,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_get_attr(self)
 
 
+@final
 class SetAttr(RegisterOp):
     """obj.attr = src (for a native object)
 
@@ -850,6 +930,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
 NAMESPACE_TYPE_VAR: Final = "typevar"
 
 
+@final
 class LoadStatic(RegisterOp):
     """Load a static name (name :: static).
 
@@ -890,6 +971,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_load_static(self)
 
 
+@final
 class InitStatic(RegisterOp):
     """static = value :: static
 
@@ -922,6 +1004,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_init_static(self)
 
 
+@final
 class TupleSet(RegisterOp):
     """dest = (reg, ...) (for fixed-length tuple)"""
 
@@ -954,6 +1037,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_tuple_set(self)
 
 
+@final
 class TupleGet(RegisterOp):
     """Get item of a fixed-length tuple (src[index])."""
 
@@ -978,6 +1062,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_tuple_get(self)
 
 
+@final
 class Cast(RegisterOp):
     """cast(type, src)
 
@@ -988,11 +1073,19 @@ class Cast(RegisterOp):
 
     error_kind = ERR_MAGIC
 
-    def __init__(self, src: Value, typ: RType, line: int, *, borrow: bool = False) -> None:
+    def __init__(
+        self, src: Value, typ: RType, line: int, *, borrow: bool = False, unchecked: bool = False
+    ) -> None:
         super().__init__(line)
         self.src = src
         self.type = typ
+        # If true, don't incref the result.
         self.is_borrowed = borrow
+        # If true, don't perform a runtime type check (only changes the static type of
+        # the operand). Used when we know that the cast will always succeed.
+        self.is_unchecked = unchecked
+        if unchecked:
+            self.error_kind = ERR_NEVER
 
     def sources(self) -> list[Value]:
         return [self.src]
@@ -1009,6 +1102,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_cast(self)
 
 
+@final
 class Box(RegisterOp):
     """box(type, src)
 
@@ -1023,11 +1117,7 @@ def __init__(self, src: Value, line: int = -1) -> None:
         self.src = src
         self.type = object_rprimitive
         # When we box None and bool values, we produce a borrowed result
-        if (
-            is_none_rprimitive(self.src.type)
-            or is_bool_rprimitive(self.src.type)
-            or is_bit_rprimitive(self.src.type)
-        ):
+        if is_none_rprimitive(self.src.type) or is_bool_or_bit_rprimitive(self.src.type):
             self.is_borrowed = True
 
     def sources(self) -> list[Value]:
@@ -1043,6 +1133,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_box(self)
 
 
+@final
 class Unbox(RegisterOp):
     """unbox(type, src)
 
@@ -1069,6 +1160,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_unbox(self)
 
 
+@final
 class RaiseStandardError(RegisterOp):
     """Raise built-in exception with an optional error string.
 
@@ -1108,6 +1200,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
 StealsDescription = Union[bool, list[bool]]
 
 
+@final
 class CallC(RegisterOp):
     """result = function(arg0, arg1, ...)
 
@@ -1162,6 +1255,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_call_c(self)
 
 
+@final
 class Truncate(RegisterOp):
     """result = truncate src from src_type to dst_type
 
@@ -1192,6 +1286,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_truncate(self)
 
 
+@final
 class Extend(RegisterOp):
     """result = extend src from src_type to dst_type
 
@@ -1226,6 +1321,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_extend(self)
 
 
+@final
 class LoadGlobal(RegisterOp):
     """Load a low-level global variable/pointer.
 
@@ -1253,6 +1349,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_load_global(self)
 
 
+@final
 class IntOp(RegisterOp):
     """Binary arithmetic or bitwise op on integer operands (e.g., r1 = r2 + r3).
 
@@ -1317,6 +1414,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
 int_op_to_id: Final = {op: op_id for op_id, op in IntOp.op_str.items()}
 
 
+@final
 class ComparisonOp(RegisterOp):
     """Low-level comparison op for integers and pointers.
 
@@ -1378,6 +1476,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_comparison_op(self)
 
 
+@final
 class FloatOp(RegisterOp):
     """Binary float arithmetic op (e.g., r1 = r2 + r3).
 
@@ -1419,6 +1518,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
 float_op_to_id: Final = {op: op_id for op_id, op in FloatOp.op_str.items()}
 
 
+@final
 class FloatNeg(RegisterOp):
     """Float negation op (r1 = -r2)."""
 
@@ -1439,6 +1539,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_float_neg(self)
 
 
+@final
 class FloatComparisonOp(RegisterOp):
     """Low-level comparison op for floats."""
 
@@ -1475,6 +1576,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
 float_comparison_op_to_id: Final = {op: op_id for op_id, op in FloatComparisonOp.op_str.items()}
 
 
+@final
 class LoadMem(RegisterOp):
     """Read a memory location: result = *(type *)src.
 
@@ -1485,14 +1587,13 @@ class LoadMem(RegisterOp):
 
     error_kind = ERR_NEVER
 
-    def __init__(self, type: RType, src: Value, line: int = -1) -> None:
+    def __init__(self, type: RType, src: Value, line: int = -1, *, borrow: bool = False) -> None:
         super().__init__(line)
         self.type = type
-        # TODO: for now we enforce that the src memory address should be Py_ssize_t
-        #       later we should also support same width unsigned int
+        # TODO: Support other native integer types
         assert is_pointer_rprimitive(src.type)
         self.src = src
-        self.is_borrowed = True
+        self.is_borrowed = borrow and type.is_refcounted
 
     def sources(self) -> list[Value]:
         return [self.src]
@@ -1504,6 +1605,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_load_mem(self)
 
 
+@final
 class SetMem(Op):
     """Write to a memory location: *(type *)dest = src
 
@@ -1535,6 +1637,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_set_mem(self)
 
 
+@final
 class GetElementPtr(RegisterOp):
     """Get the address of a struct element.
 
@@ -1561,6 +1664,40 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_get_element_ptr(self)
 
 
+@final
+class SetElement(RegisterOp):
+    """Set the value of a struct element.
+
+    This evaluates to a new struct with the changed value.
+
+    Use together with Undef to initialize a fresh struct value
+    (see Undef for more details).
+    """
+
+    error_kind = ERR_NEVER
+
+    def __init__(self, src: Value, field: str, item: Value, line: int = -1) -> None:
+        super().__init__(line)
+        assert isinstance(src.type, RStruct), src.type
+        self.type = src.type
+        self.src = src
+        self.item = item
+        self.field = field
+
+    def sources(self) -> list[Value]:
+        return [self.src]
+
+    def set_sources(self, new: list[Value]) -> None:
+        (self.src,) = new
+
+    def stolen(self) -> list[Value]:
+        return [self.src]
+
+    def accept(self, visitor: OpVisitor[T]) -> T:
+        return visitor.visit_set_element(self)
+
+
+@final
 class LoadAddress(RegisterOp):
     """Get the address of a value: result = (type)&src
 
@@ -1595,6 +1732,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_load_address(self)
 
 
+@final
 class KeepAlive(RegisterOp):
     """A no-op operation that ensures source values aren't freed.
 
@@ -1642,6 +1780,7 @@ def accept(self, visitor: OpVisitor[T]) -> T:
         return visitor.visit_keep_alive(self)
 
 
+@final
 class Unborrow(RegisterOp):
     """A no-op op to create a regular reference from a borrowed one.
 
@@ -1830,6 +1969,10 @@ def visit_set_mem(self, op: SetMem) -> T:
     def visit_get_element_ptr(self, op: GetElementPtr) -> T:
         raise NotImplementedError
 
+    @abstractmethod
+    def visit_set_element(self, op: SetElement) -> T:
+        raise NotImplementedError
+
     @abstractmethod
     def visit_load_address(self, op: LoadAddress) -> T:
         raise NotImplementedError
diff --git a/mypyc/ir/pprint.py b/mypyc/ir/pprint.py
index 6c96a21e473b..efefd76d15f0 100644
--- a/mypyc/ir/pprint.py
+++ b/mypyc/ir/pprint.py
@@ -21,6 +21,7 @@
     Cast,
     ComparisonOp,
     ControlOp,
+    CString,
     DecRef,
     Extend,
     Float,
@@ -49,12 +50,14 @@
     Register,
     Return,
     SetAttr,
+    SetElement,
     SetMem,
     Truncate,
     TupleGet,
     TupleSet,
     Unborrow,
     Unbox,
+    Undef,
     Unreachable,
     Value,
 )
@@ -193,7 +196,13 @@ def visit_method_call(self, op: MethodCall) -> str:
         return s
 
     def visit_cast(self, op: Cast) -> str:
-        return self.format("%r = %scast(%s, %r)", op, self.borrow_prefix(op), op.type, op.src)
+        if op.is_unchecked:
+            prefix = "unchecked "
+        else:
+            prefix = ""
+        return self.format(
+            "%r = %s%scast(%s, %r)", op, prefix, self.borrow_prefix(op), op.type, op.src
+        )
 
     def visit_box(self, op: Box) -> str:
         return self.format("%r = box(%s, %r)", op, op.src.type, op.src)
@@ -264,7 +273,9 @@ def visit_float_comparison_op(self, op: FloatComparisonOp) -> str:
         return self.format("%r = %r %s %r", op, op.lhs, op.op_str[op.op], op.rhs)
 
     def visit_load_mem(self, op: LoadMem) -> str:
-        return self.format("%r = load_mem %r :: %t*", op, op.src, op.type)
+        return self.format(
+            "%r = %sload_mem %r :: %t*", op, self.borrow_prefix(op), op.src, op.type
+        )
 
     def visit_set_mem(self, op: SetMem) -> str:
         return self.format("set_mem %r, %r :: %t*", op.dest, op.src, op.dest_type)
@@ -272,6 +283,9 @@ def visit_set_mem(self, op: SetMem) -> str:
     def visit_get_element_ptr(self, op: GetElementPtr) -> str:
         return self.format("%r = get_element_ptr %r %s :: %t", op, op.src, op.field, op.src_type)
 
+    def visit_set_element(self, op: SetElement) -> str:
+        return self.format("%r = set_element %r, %s, %r", op, op.src, op.field, op.item)
+
     def visit_load_address(self, op: LoadAddress) -> str:
         if isinstance(op.src, Register):
             return self.format("%r = load_address %r", op, op.src)
@@ -327,6 +341,10 @@ def format(self, fmt: str, *args: Any) -> str:
                         result.append(str(arg.value))
                     elif isinstance(arg, Float):
                         result.append(repr(arg.value))
+                    elif isinstance(arg, CString):
+                        result.append(f"CString({arg.value!r})")
+                    elif isinstance(arg, Undef):
+                        result.append(f"undef {arg.type.name}")
                     else:
                         result.append(self.names[arg])
                 elif typespec == "d":
@@ -483,7 +501,7 @@ def generate_names_for_ir(args: list[Register], blocks: list[BasicBlock]) -> dic
                     continue
                 if isinstance(value, Register) and value.name:
                     name = value.name
-                elif isinstance(value, (Integer, Float)):
+                elif isinstance(value, (Integer, Float, Undef)):
                     continue
                 else:
                     name = "r%d" % temp_index
diff --git a/mypyc/ir/rtypes.py b/mypyc/ir/rtypes.py
index 60a56065006f..34824a59cd5c 100644
--- a/mypyc/ir/rtypes.py
+++ b/mypyc/ir/rtypes.py
@@ -18,12 +18,27 @@
 
 mypyc.irbuild.mapper.Mapper.type_to_rtype converts mypy Types to mypyc
 RTypes.
+
+NOTE: As a convention, we don't create subclasses of concrete RType
+      subclasses (e.g. you shouldn't define a subclass of RTuple, which
+      is a concrete class). We prefer a flat class hierarchy.
+
+      If you want to introduce a variant of an existing class, you'd
+      typically add an attribute (e.g. a flag) to an existing concrete
+      class to enable the new behavior. In rare cases, adding a new
+      abstract base class could also be an option. Adding a completely
+      separate class and sharing some functionality using module-level
+      helper functions may also be reasonable.
+
+      This makes it possible to use isinstance(x, <concrete RType
+      subclass>) checks without worrying about potential subclasses
+      and avoids most trouble caused by implementation inheritance.
 """
 
 from __future__ import annotations
 
 from abc import abstractmethod
-from typing import TYPE_CHECKING, ClassVar, Final, Generic, TypeVar
+from typing import TYPE_CHECKING, ClassVar, Final, Generic, TypeVar, final
 from typing_extensions import TypeGuard
 
 from mypyc.common import HAVE_IMMORTAL, IS_32_BIT_PLATFORM, PLATFORM_SIZE, JsonDict, short_name
@@ -155,6 +170,7 @@ def visit_rvoid(self, typ: RVoid, /) -> T:
         raise NotImplementedError
 
 
+@final
 class RVoid(RType):
     """The void type (no value).
 
@@ -176,7 +192,7 @@ def may_be_immortal(self) -> bool:
     def serialize(self) -> str:
         return "void"
 
-    def __eq__(self, other: object) -> bool:
+    def __eq__(self, other: object) -> TypeGuard[RVoid]:
         return isinstance(other, RVoid)
 
     def __hash__(self) -> int:
@@ -187,6 +203,7 @@ def __hash__(self) -> int:
 void_rtype: Final = RVoid()
 
 
+@final
 class RPrimitive(RType):
     """Primitive type such as 'object' or 'int'.
 
@@ -237,13 +254,11 @@ def __init__(
         elif ctype == "CPyPtr":
             # TODO: Invent an overlapping error value?
             self.c_undefined = "0"
-        elif ctype == "PyObject *":
-            # Boxed types use the null pointer as the error value.
+        elif ctype.endswith("*"):
+            # Boxed and pointer types use the null pointer as the error value.
             self.c_undefined = "NULL"
         elif ctype == "char":
             self.c_undefined = "2"
-        elif ctype in ("PyObject **", "void *"):
-            self.c_undefined = "NULL"
         elif ctype == "double":
             self.c_undefined = "-113.0"
         elif ctype in ("uint8_t", "uint16_t", "uint32_t", "uint64_t"):
@@ -264,7 +279,7 @@ def serialize(self) -> str:
     def __repr__(self) -> str:
         return "<RPrimitive %s>" % self.name
 
-    def __eq__(self, other: object) -> bool:
+    def __eq__(self, other: object) -> TypeGuard[RPrimitive]:
         return isinstance(other, RPrimitive) and other.name == self.name
 
     def __hash__(self) -> int:
@@ -428,6 +443,10 @@ def __hash__(self) -> int:
     "c_ptr", is_unboxed=False, is_refcounted=False, ctype="void *"
 )
 
+cstring_rprimitive: Final = RPrimitive(
+    "cstring", is_unboxed=True, is_refcounted=False, ctype="const char *"
+)
+
 # The type corresponding to mypyc.common.BITMAP_TYPE
 bitmap_rprimitive: Final = uint32_rprimitive
 
@@ -493,16 +512,25 @@ def __hash__(self) -> int:
 # Python range object.
 range_rprimitive: Final = RPrimitive("builtins.range", is_unboxed=False, is_refcounted=True)
 
+KNOWN_NATIVE_TYPES: Final = {
+    name: RPrimitive(name, is_unboxed=False, is_refcounted=True)
+    for name in ["native_internal.Buffer"]
+}
+
+
+def is_native_rprimitive(rtype: RType) -> bool:
+    return isinstance(rtype, RPrimitive) and rtype.name in KNOWN_NATIVE_TYPES
 
-def is_tagged(rtype: RType) -> bool:
+
+def is_tagged(rtype: RType) -> TypeGuard[RPrimitive]:
     return rtype is int_rprimitive or rtype is short_int_rprimitive
 
 
-def is_int_rprimitive(rtype: RType) -> bool:
+def is_int_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
     return rtype is int_rprimitive
 
 
-def is_short_int_rprimitive(rtype: RType) -> bool:
+def is_short_int_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
     return rtype is short_int_rprimitive
 
 
@@ -516,7 +544,7 @@ def is_int32_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
     )
 
 
-def is_int64_rprimitive(rtype: RType) -> bool:
+def is_int64_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
     return rtype is int64_rprimitive or (
         rtype is c_pyssize_t_rprimitive and rtype._ctype == "int64_t"
     )
@@ -535,77 +563,93 @@ def is_uint8_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
     return rtype is uint8_rprimitive
 
 
-def is_uint32_rprimitive(rtype: RType) -> bool:
+def is_uint32_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
     return rtype is uint32_rprimitive
 
 
-def is_uint64_rprimitive(rtype: RType) -> bool:
+def is_uint64_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
     return rtype is uint64_rprimitive
 
 
-def is_c_py_ssize_t_rprimitive(rtype: RType) -> bool:
+def is_c_py_ssize_t_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
     return rtype is c_pyssize_t_rprimitive
 
 
-def is_pointer_rprimitive(rtype: RType) -> bool:
+def is_pointer_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
     return rtype is pointer_rprimitive
 
 
-def is_float_rprimitive(rtype: RType) -> bool:
+def is_float_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
     return isinstance(rtype, RPrimitive) and rtype.name == "builtins.float"
 
 
-def is_bool_rprimitive(rtype: RType) -> bool:
+def is_bool_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
     return isinstance(rtype, RPrimitive) and rtype.name == "builtins.bool"
 
 
-def is_bit_rprimitive(rtype: RType) -> bool:
+def is_bit_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
     return isinstance(rtype, RPrimitive) and rtype.name == "bit"
 
 
-def is_object_rprimitive(rtype: RType) -> bool:
+def is_bool_or_bit_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
+    return is_bool_rprimitive(rtype) or is_bit_rprimitive(rtype)
+
+
+def is_object_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
     return isinstance(rtype, RPrimitive) and rtype.name == "builtins.object"
 
 
-def is_none_rprimitive(rtype: RType) -> bool:
+def is_none_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
     return isinstance(rtype, RPrimitive) and rtype.name == "builtins.None"
 
 
-def is_list_rprimitive(rtype: RType) -> bool:
+def is_list_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
     return isinstance(rtype, RPrimitive) and rtype.name == "builtins.list"
 
 
-def is_dict_rprimitive(rtype: RType) -> bool:
+def is_dict_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
     return isinstance(rtype, RPrimitive) and rtype.name == "builtins.dict"
 
 
-def is_set_rprimitive(rtype: RType) -> bool:
+def is_set_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
     return isinstance(rtype, RPrimitive) and rtype.name == "builtins.set"
 
 
-def is_frozenset_rprimitive(rtype: RType) -> bool:
+def is_frozenset_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
     return isinstance(rtype, RPrimitive) and rtype.name == "builtins.frozenset"
 
 
-def is_str_rprimitive(rtype: RType) -> bool:
+def is_str_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
     return isinstance(rtype, RPrimitive) and rtype.name == "builtins.str"
 
 
-def is_bytes_rprimitive(rtype: RType) -> bool:
+def is_bytes_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
     return isinstance(rtype, RPrimitive) and rtype.name == "builtins.bytes"
 
 
-def is_tuple_rprimitive(rtype: RType) -> bool:
+def is_tuple_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
     return isinstance(rtype, RPrimitive) and rtype.name == "builtins.tuple"
 
 
-def is_range_rprimitive(rtype: RType) -> bool:
+def is_range_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
     return isinstance(rtype, RPrimitive) and rtype.name == "builtins.range"
 
 
-def is_sequence_rprimitive(rtype: RType) -> bool:
+def is_sequence_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
     return isinstance(rtype, RPrimitive) and (
-        is_list_rprimitive(rtype) or is_tuple_rprimitive(rtype) or is_str_rprimitive(rtype)
+        is_list_rprimitive(rtype)
+        or is_tuple_rprimitive(rtype)
+        or is_str_rprimitive(rtype)
+        or is_bytes_rprimitive(rtype)
+    )
+
+
+def is_immutable_rprimitive(rtype: RType) -> TypeGuard[RPrimitive]:
+    return (
+        is_str_rprimitive(rtype)
+        or is_bytes_rprimitive(rtype)
+        or is_tuple_rprimitive(rtype)
+        or is_frozenset_rprimitive(rtype)
     )
 
 
@@ -650,6 +694,7 @@ def visit_rvoid(self, t: RVoid) -> str:
         assert False, "rvoid in tuple?"
 
 
+@final
 class RTuple(RType):
     """Fixed-length unboxed tuple (represented as a C struct).
 
@@ -693,7 +738,7 @@ def __str__(self) -> str:
     def __repr__(self) -> str:
         return "<RTuple %s>" % ", ".join(repr(typ) for typ in self.types)
 
-    def __eq__(self, other: object) -> bool:
+    def __eq__(self, other: object) -> TypeGuard[RTuple]:
         return isinstance(other, RTuple) and self.types == other.types
 
     def __hash__(self) -> int:
@@ -791,6 +836,7 @@ def compute_aligned_offsets_and_size(types: list[RType]) -> tuple[list[int], int
     return offsets, final_size
 
 
+@final
 class RStruct(RType):
     """C struct type"""
 
@@ -825,7 +871,7 @@ def __repr__(self) -> str:
             ", ".join(name + ":" + repr(typ) for name, typ in zip(self.names, self.types)),
         )
 
-    def __eq__(self, other: object) -> bool:
+    def __eq__(self, other: object) -> TypeGuard[RStruct]:
         return (
             isinstance(other, RStruct)
             and self.name == other.name
@@ -844,6 +890,7 @@ def deserialize(cls, data: JsonDict, ctx: DeserMaps) -> RStruct:
         assert False
 
 
+@final
 class RInstance(RType):
     """Instance of user-defined class (compiled to C extension class).
 
@@ -894,7 +941,7 @@ def attr_type(self, name: str) -> RType:
     def __repr__(self) -> str:
         return "<RInstance %s>" % self.name
 
-    def __eq__(self, other: object) -> bool:
+    def __eq__(self, other: object) -> TypeGuard[RInstance]:
         return isinstance(other, RInstance) and other.name == self.name
 
     def __hash__(self) -> int:
@@ -904,6 +951,7 @@ def serialize(self) -> str:
         return self.name
 
 
+@final
 class RUnion(RType):
     """union[x, ..., y]"""
 
@@ -947,7 +995,7 @@ def __str__(self) -> str:
         return "union[%s]" % ", ".join(str(item) for item in self.items)
 
     # We compare based on the set because order in a union doesn't matter
-    def __eq__(self, other: object) -> bool:
+    def __eq__(self, other: object) -> TypeGuard[RUnion]:
         return isinstance(other, RUnion) and self.items_set == other.items_set
 
     def __hash__(self) -> int:
@@ -979,7 +1027,7 @@ def flatten_nested_unions(types: list[RType]) -> list[RType]:
 def optional_value_type(rtype: RType) -> RType | None:
     """If rtype is the union of none_rprimitive and another type X, return X.
 
-    Otherwise return None.
+    Otherwise, return None.
     """
     if isinstance(rtype, RUnion) and len(rtype.items) == 2:
         if rtype.items[0] == none_rprimitive:
@@ -989,11 +1037,12 @@ def optional_value_type(rtype: RType) -> RType | None:
     return None
 
 
-def is_optional_type(rtype: RType) -> bool:
+def is_optional_type(rtype: RType) -> TypeGuard[RUnion]:
     """Is rtype an optional type with exactly two union items?"""
     return optional_value_type(rtype) is not None
 
 
+@final
 class RArray(RType):
     """Fixed-length C array type (for example, int[5]).
 
@@ -1020,7 +1069,7 @@ def __str__(self) -> str:
     def __repr__(self) -> str:
         return f"<RArray {self.item_type!r}[{self.length}]>"
 
-    def __eq__(self, other: object) -> bool:
+    def __eq__(self, other: object) -> TypeGuard[RArray]:
         return (
             isinstance(other, RArray)
             and self.item_type == other.item_type
diff --git a/mypyc/irbuild/builder.py b/mypyc/irbuild/builder.py
index 75e059a5b570..4f2f539118d7 100644
--- a/mypyc/irbuild/builder.py
+++ b/mypyc/irbuild/builder.py
@@ -59,7 +59,7 @@
 )
 from mypy.util import module_prefix, split_target
 from mypy.visitor import ExpressionVisitor, StatementVisitor
-from mypyc.common import BITMAP_BITS, SELF_NAME, TEMP_ATTR_NAME
+from mypyc.common import BITMAP_BITS, GENERATOR_ATTRIBUTE_PREFIX, SELF_NAME, TEMP_ATTR_NAME
 from mypyc.crash import catch_errors
 from mypyc.errors import Errors
 from mypyc.ir.class_ir import ClassIR, NonExtClassInfo
@@ -91,6 +91,7 @@
     RType,
     RUnion,
     bitmap_rprimitive,
+    bytes_rprimitive,
     c_pyssize_t_rprimitive,
     dict_rprimitive,
     int_rprimitive,
@@ -129,6 +130,7 @@
 from mypyc.primitives.list_ops import list_get_item_unsafe_op, list_pop_last, to_list
 from mypyc.primitives.misc_ops import check_unpack_count_op, get_module_dict_op, import_op
 from mypyc.primitives.registry import CFunctionDescription, function_ops
+from mypyc.primitives.tuple_ops import tuple_get_item_unsafe_op
 
 # These int binary operations can borrow their operands safely, since the
 # primitives take this into consideration.
@@ -423,6 +425,10 @@ def new_tuple(self, items: list[Value], line: int) -> Value:
     def debug_print(self, toprint: str | Value) -> None:
         return self.builder.debug_print(toprint)
 
+    def set_immortal_if_free_threaded(self, v: Value, line: int) -> None:
+        """Make an object immortal on free-threaded builds (to avoid contention)."""
+        self.builder.set_immortal_if_free_threaded(v, line)
+
     # Helpers for IR building
 
     def add_to_non_ext_dict(
@@ -432,6 +438,10 @@ def add_to_non_ext_dict(
         key_unicode = self.load_str(key)
         self.primitive_op(dict_set_item_op, [non_ext.dict, key_unicode, val], line)
 
+        # It's important that accessing class dictionary items from multiple threads
+        # doesn't cause contention.
+        self.builder.set_immortal_if_free_threaded(val, line)
+
     def gen_import(self, id: str, line: int) -> None:
         self.imports[id] = None
 
@@ -551,8 +561,8 @@ def init_final_static(
         *,
         type_override: RType | None = None,
     ) -> None:
-        assert isinstance(lvalue, NameExpr)
-        assert isinstance(lvalue.node, Var)
+        assert isinstance(lvalue, NameExpr), lvalue
+        assert isinstance(lvalue.node, Var), lvalue.node
         if lvalue.node.final_value is None:
             if class_name is None:
                 name = lvalue.name
@@ -642,7 +652,11 @@ def get_assignment_target(
                     # current environment.
                     if self.fn_info.is_generator:
                         return self.add_var_to_env_class(
-                            symbol, reg_type, self.fn_info.generator_class, reassign=False
+                            symbol,
+                            reg_type,
+                            self.fn_info.generator_class,
+                            reassign=False,
+                            prefix=GENERATOR_ATTRIBUTE_PREFIX,
                         )
 
                     # Otherwise define a new local variable.
@@ -708,6 +722,11 @@ def read(
 
         assert False, "Unsupported lvalue: %r" % target
 
+    def read_nullable_attr(self, obj: Value, attr: str, line: int = -1) -> Value:
+        """Read an attribute that might have an error value without raising AttributeError."""
+        assert isinstance(obj.type, RInstance) and obj.type.class_ir.is_ext_class
+        return self.add(GetAttr(obj, attr, line, allow_error_value=True))
+
     def assign(self, target: Register | AssignmentTarget, rvalue_reg: Value, line: int) -> None:
         if isinstance(target, Register):
             self.add(Assign(target, self.coerce_rvalue(rvalue_reg, target.type, line)))
@@ -767,10 +786,15 @@ def process_sequence_assignment(
         values = []
         for i in range(len(target.items)):
             item = target.items[i]
-            index = self.builder.load_int(i)
+            index: Value
             if is_list_rprimitive(rvalue.type):
+                index = Integer(i, c_pyssize_t_rprimitive)
                 item_value = self.primitive_op(list_get_item_unsafe_op, [rvalue, index], line)
+            elif is_tuple_rprimitive(rvalue.type):
+                index = Integer(i, c_pyssize_t_rprimitive)
+                item_value = self.call_c(tuple_get_item_unsafe_op, [rvalue, index], line)
             else:
+                index = self.builder.load_int(i)
                 item_value = self.builder.gen_method_call(
                     rvalue, "__getitem__", [index], item.type, line
                 )
@@ -939,8 +963,12 @@ def get_sequence_type_from_type(self, target_type: Type) -> RType:
         elif isinstance(target_type, Instance):
             if target_type.type.fullname == "builtins.str":
                 return str_rprimitive
-            else:
+            elif target_type.type.fullname == "builtins.bytes":
+                return bytes_rprimitive
+            try:
                 return self.type_to_rtype(target_type.args[0])
+            except IndexError:
+                raise ValueError(f"{target_type!r} is not a valid sequence.") from None
         # This elif-blocks are needed for iterating over classes derived from NamedTuple.
         elif isinstance(target_type, TypeVarLikeType):
             return self.get_sequence_type_from_type(target_type.upper_bound)
@@ -1136,12 +1164,20 @@ def call_refexpr_with_args(
         )
 
     def shortcircuit_expr(self, expr: OpExpr) -> Value:
+        def handle_right() -> Value:
+            if expr.right_unreachable:
+                self.builder.add(
+                    RaiseStandardError(
+                        RaiseStandardError.RUNTIME_ERROR,
+                        "mypyc internal error: should be unreachable",
+                        expr.right.line,
+                    )
+                )
+                return self.builder.none()
+            return self.accept(expr.right)
+
         return self.builder.shortcircuit_helper(
-            expr.op,
-            self.node_type(expr),
-            lambda: self.accept(expr.left),
-            lambda: self.accept(expr.right),
-            expr.line,
+            expr.op, self.node_type(expr), lambda: self.accept(expr.left), handle_right, expr.line
         )
 
     # Basic helpers
@@ -1258,7 +1294,7 @@ def add_local(self, symbol: SymbolNode, typ: RType, is_arg: bool = False) -> Reg
         Args:
             is_arg: is this a function argument
         """
-        assert isinstance(symbol, SymbolNode)
+        assert isinstance(symbol, SymbolNode), symbol
         reg = Register(
             typ, remangle_redefinition_name(symbol.name), is_arg=is_arg, line=symbol.line
         )
@@ -1273,7 +1309,7 @@ def add_local_reg(
         """Like add_local, but return an assignment target instead of value."""
         self.add_local(symbol, typ, is_arg)
         target = self.symtables[-1][symbol]
-        assert isinstance(target, AssignmentTargetRegister)
+        assert isinstance(target, AssignmentTargetRegister), target
         return target
 
     def add_self_to_env(self, cls: ClassIR) -> AssignmentTargetRegister:
@@ -1306,10 +1342,11 @@ def add_var_to_env_class(
         base: FuncInfo | ImplicitClass,
         reassign: bool = False,
         always_defined: bool = False,
+        prefix: str = "",
     ) -> AssignmentTarget:
         # First, define the variable name as an attribute of the environment class, and then
         # construct a target for that attribute.
-        name = remangle_redefinition_name(var.name)
+        name = prefix + remangle_redefinition_name(var.name)
         self.fn_info.env_class.attributes[name] = rtype
         if always_defined:
             self.fn_info.env_class.attrs_with_defaults.add(name)
@@ -1433,7 +1470,7 @@ def get_default() -> Value:
                         GetAttr(builder.fn_info.callable_class.self_reg, name, arg.line)
                     )
 
-            assert isinstance(target, AssignmentTargetRegister)
+            assert isinstance(target, AssignmentTargetRegister), target
             reg = target.register
             if not reg.type.error_overlap:
                 builder.assign_if_null(target.register, get_default, arg.initializer.line)
diff --git a/mypyc/irbuild/callable_class.py b/mypyc/irbuild/callable_class.py
index c7c3c7677cda..bbd1b909afb6 100644
--- a/mypyc/irbuild/callable_class.py
+++ b/mypyc/irbuild/callable_class.py
@@ -56,6 +56,7 @@ class for the nested function.
     # environment to point at the previously defined environment
     # class.
     callable_class_ir = ClassIR(name, builder.module_name, is_generated=True, is_final_class=True)
+    callable_class_ir.reuse_freed_instance = True
 
     # The functools @wraps decorator attempts to call setattr on
     # nested functions, so we create a dict for these nested
diff --git a/mypyc/irbuild/classdef.py b/mypyc/irbuild/classdef.py
index 13121707773a..324b44b95dc4 100644
--- a/mypyc/irbuild/classdef.py
+++ b/mypyc/irbuild/classdef.py
@@ -64,8 +64,9 @@
     handle_non_ext_method,
     load_type,
 )
+from mypyc.irbuild.prepare import GENERATOR_HELPER_NAME
 from mypyc.irbuild.util import dataclass_type, get_func_def, is_constant, is_dataclass_decorator
-from mypyc.primitives.dict_ops import dict_new_op, dict_set_item_op
+from mypyc.primitives.dict_ops import dict_new_op, exact_dict_set_item_op
 from mypyc.primitives.generic_ops import (
     iter_op,
     next_op,
@@ -135,6 +136,14 @@ def transform_class_def(builder: IRBuilder, cdef: ClassDef) -> None:
         cls_builder = NonExtClassBuilder(builder, cdef)
 
     for stmt in cdef.defs.body:
+        if (
+            isinstance(stmt, (FuncDef, Decorator, OverloadedFuncDef))
+            and stmt.name == GENERATOR_HELPER_NAME
+        ):
+            builder.error(
+                f'Method name "{stmt.name}" is reserved for mypyc internal use', stmt.line
+            )
+
         if isinstance(stmt, OverloadedFuncDef) and stmt.is_property:
             if isinstance(cls_builder, NonExtClassBuilder):
                 # properties with both getters and setters in non_extension
@@ -253,14 +262,17 @@ def finalize(self, ir: ClassIR) -> None:
         non_ext_class = load_non_ext_class(self.builder, ir, self.non_ext, self.cdef.line)
         non_ext_class = load_decorated_class(self.builder, self.cdef, non_ext_class)
 
+        # Try to avoid contention when using free threading.
+        self.builder.set_immortal_if_free_threaded(non_ext_class, self.cdef.line)
+
         # Save the decorated class
         self.builder.add(
             InitStatic(non_ext_class, self.cdef.name, self.builder.module_name, NAMESPACE_TYPE)
         )
 
         # Add the non-extension class to the dict
-        self.builder.primitive_op(
-            dict_set_item_op,
+        self.builder.call_c(
+            exact_dict_set_item_op,
             [
                 self.builder.load_globals_dict(),
                 self.builder.load_str(self.cdef.name),
@@ -415,7 +427,7 @@ def get_type_annotation(self, stmt: AssignmentStmt) -> TypeInfo | None:
                 type_name = stmt.rvalue.args[index]
                 if isinstance(type_name, NameExpr) and isinstance(type_name.node, TypeInfo):
                     lvalue = stmt.lvalues[0]
-                    assert isinstance(lvalue, NameExpr)
+                    assert isinstance(lvalue, NameExpr), lvalue
                     return type_name.node
         return None
 
@@ -440,6 +452,11 @@ def allocate_class(builder: IRBuilder, cdef: ClassDef) -> Value:
     )
     # Create the class
     tp = builder.call_c(pytype_from_template_op, [template, tp_bases, modname], cdef.line)
+
+    # Set type object to be immortal if free threaded, as otherwise reference count contention
+    # can cause a big performance hit.
+    builder.set_immortal_if_free_threaded(tp, cdef.line)
+
     # Immediately fix up the trait vtables, before doing anything with the class.
     ir = builder.mapper.type_to_ir[cdef.info]
     if not ir.is_trait and not ir.builtin_base:
@@ -470,8 +487,10 @@ def allocate_class(builder: IRBuilder, cdef: ClassDef) -> Value:
     builder.add(InitStatic(tp, cdef.name, builder.module_name, NAMESPACE_TYPE))
 
     # Add it to the dict
-    builder.primitive_op(
-        dict_set_item_op, [builder.load_globals_dict(), builder.load_str(cdef.name), tp], cdef.line
+    builder.call_c(
+        exact_dict_set_item_op,
+        [builder.load_globals_dict(), builder.load_str(cdef.name), tp],
+        cdef.line,
     )
 
     return tp
@@ -655,7 +674,7 @@ def add_non_ext_class_attr_ann(
             typ = builder.add(LoadAddress(type_object_op.type, type_object_op.src, stmt.line))
 
     key = builder.load_str(lvalue.name)
-    builder.primitive_op(dict_set_item_op, [non_ext.anns, key, typ], stmt.line)
+    builder.call_c(exact_dict_set_item_op, [non_ext.anns, key, typ], stmt.line)
 
 
 def add_non_ext_class_attr(
@@ -756,7 +775,7 @@ def generate_attr_defaults_init(
         self_var = builder.self()
         for stmt in default_assignments:
             lvalue = stmt.lvalues[0]
-            assert isinstance(lvalue, NameExpr)
+            assert isinstance(lvalue, NameExpr), lvalue
             if not stmt.is_final_def and not is_constant(stmt.rvalue):
                 builder.warning("Unsupported default attribute value", stmt.rvalue.line)
 
@@ -826,7 +845,9 @@ def gen_glue_ne_method(builder: IRBuilder, cls: ClassIR, line: int) -> None:
             )
             builder.activate_block(regular_block)
             rettype = bool_rprimitive if return_bool and strict_typing else object_rprimitive
-            retval = builder.coerce(builder.unary_op(eqval, "not", line), rettype, line)
+            retval = builder.coerce(
+                builder.builder.unary_not(eqval, line, likely_bool=True), rettype, line
+            )
             builder.add(Return(retval))
             builder.activate_block(not_implemented_block)
             builder.add(Return(not_implemented))
@@ -862,7 +883,7 @@ def load_decorated_class(builder: IRBuilder, cdef: ClassDef, type_obj: Value) ->
     dec_class = type_obj
     for d in reversed(decorators):
         decorator = d.accept(builder.visitor)
-        assert isinstance(decorator, Value)
+        assert isinstance(decorator, Value), decorator
         dec_class = builder.py_call(decorator, [dec_class], dec_class.line)
     return dec_class
 
@@ -873,7 +894,7 @@ def cache_class_attrs(
     """Add class attributes to be cached to the global cache."""
     typ = builder.load_native_type_object(cdef.info.fullname)
     for lval, rtype in attrs_to_cache:
-        assert isinstance(lval, NameExpr)
+        assert isinstance(lval, NameExpr), lval
         rval = builder.py_get_attr(typ, lval.name, cdef.line)
         builder.init_final_static(lval, rval, cdef.name, type_override=rtype)
 
diff --git a/mypyc/irbuild/context.py b/mypyc/irbuild/context.py
index 8d35c0ce2599..8d2e55ed96fb 100644
--- a/mypyc/irbuild/context.py
+++ b/mypyc/irbuild/context.py
@@ -167,6 +167,11 @@ def __init__(self, ir: ClassIR) -> None:
         # Holds the arg passed to send
         self.send_arg_reg: Value | None = None
 
+        # Holds the PyObject ** pointer through which return value can be passed
+        # instead of raising StopIteration(ret_value) (only if not NULL). This
+        # is used for faster native-to-native calls.
+        self.stop_iter_value_reg: Value | None = None
+
         # The switch block is used to decide which instruction to go using the value held in the
         # next-label register.
         self.switch_block = BasicBlock()
diff --git a/mypyc/irbuild/env_class.py b/mypyc/irbuild/env_class.py
index 9e72f7efcf94..2334b4370103 100644
--- a/mypyc/irbuild/env_class.py
+++ b/mypyc/irbuild/env_class.py
@@ -18,7 +18,13 @@ def g() -> int:
 from __future__ import annotations
 
 from mypy.nodes import Argument, FuncDef, SymbolNode, Var
-from mypyc.common import BITMAP_BITS, ENV_ATTR_NAME, SELF_NAME, bitmap_name
+from mypyc.common import (
+    BITMAP_BITS,
+    ENV_ATTR_NAME,
+    GENERATOR_ATTRIBUTE_PREFIX,
+    SELF_NAME,
+    bitmap_name,
+)
 from mypyc.ir.class_ir import ClassIR
 from mypyc.ir.ops import Call, GetAttr, SetAttr, Value
 from mypyc.ir.rtypes import RInstance, bitmap_rprimitive, object_rprimitive
@@ -48,6 +54,7 @@ class is generated, the function environment has not yet been
         is_generated=True,
         is_final_class=True,
     )
+    env_class.reuse_freed_instance = True
     env_class.attributes[SELF_NAME] = RInstance(env_class)
     if builder.fn_info.is_nested:
         # If the function is nested, its environment class must contain an environment
@@ -59,7 +66,7 @@ class is generated, the function environment has not yet been
     return env_class
 
 
-def finalize_env_class(builder: IRBuilder) -> None:
+def finalize_env_class(builder: IRBuilder, prefix: str = "") -> None:
     """Generate, instantiate, and set up the environment of an environment class."""
     if not builder.fn_info.can_merge_generator_and_env_classes():
         instantiate_env_class(builder)
@@ -68,9 +75,9 @@ def finalize_env_class(builder: IRBuilder) -> None:
     # that were previously added to the environment with references to the function's
     # environment class.
     if builder.fn_info.is_nested:
-        add_args_to_env(builder, local=False, base=builder.fn_info.callable_class)
+        add_args_to_env(builder, local=False, base=builder.fn_info.callable_class, prefix=prefix)
     else:
-        add_args_to_env(builder, local=False, base=builder.fn_info)
+        add_args_to_env(builder, local=False, base=builder.fn_info, prefix=prefix)
 
 
 def instantiate_env_class(builder: IRBuilder) -> Value:
@@ -95,7 +102,7 @@ def instantiate_env_class(builder: IRBuilder) -> Value:
     return curr_env_reg
 
 
-def load_env_registers(builder: IRBuilder) -> None:
+def load_env_registers(builder: IRBuilder, prefix: str = "") -> None:
     """Load the registers for the current FuncItem being visited.
 
     Adds the arguments of the FuncItem to the environment. If the
@@ -103,7 +110,7 @@ def load_env_registers(builder: IRBuilder) -> None:
     loads all of the outer environments of the FuncItem into registers
     so that they can be used when accessing free variables.
     """
-    add_args_to_env(builder, local=True)
+    add_args_to_env(builder, local=True, prefix=prefix)
 
     fn_info = builder.fn_info
     fitem = fn_info.fitem
@@ -112,7 +119,7 @@ def load_env_registers(builder: IRBuilder) -> None:
         # If this is a FuncDef, then make sure to load the FuncDef into its own environment
         # class so that the function can be called recursively.
         if isinstance(fitem, FuncDef) and fn_info.add_nested_funcs_to_env:
-            setup_func_for_recursive_call(builder, fitem, fn_info.callable_class)
+            setup_func_for_recursive_call(builder, fitem, fn_info.callable_class, prefix=prefix)
 
 
 def load_outer_env(
@@ -133,8 +140,11 @@ def load_outer_env(
     assert isinstance(env.type, RInstance), f"{env} must be of type RInstance"
 
     for symbol, target in outer_env.items():
-        env.type.class_ir.attributes[symbol.name] = target.type
-        symbol_target = AssignmentTargetAttr(env, symbol.name)
+        attr_name = symbol.name
+        if isinstance(target, AssignmentTargetAttr):
+            attr_name = target.attr
+        env.type.class_ir.attributes[attr_name] = target.type
+        symbol_target = AssignmentTargetAttr(env, attr_name)
         builder.add_target(symbol, symbol_target)
 
     return env
@@ -177,6 +187,7 @@ def add_args_to_env(
     local: bool = True,
     base: FuncInfo | ImplicitClass | None = None,
     reassign: bool = True,
+    prefix: str = "",
 ) -> None:
     fn_info = builder.fn_info
     args = fn_info.fitem.arguments
@@ -192,10 +203,12 @@ def add_args_to_env(
             if is_free_variable(builder, arg.variable) or fn_info.is_generator:
                 rtype = builder.type_to_rtype(arg.variable.type)
                 assert base is not None, "base cannot be None for adding nonlocal args"
-                builder.add_var_to_env_class(arg.variable, rtype, base, reassign=reassign)
+                builder.add_var_to_env_class(
+                    arg.variable, rtype, base, reassign=reassign, prefix=prefix
+                )
 
 
-def add_vars_to_env(builder: IRBuilder) -> None:
+def add_vars_to_env(builder: IRBuilder, prefix: str = "") -> None:
     """Add relevant local variables and nested functions to the environment class.
 
     Add all variables and functions that are declared/defined within current
@@ -215,7 +228,9 @@ def add_vars_to_env(builder: IRBuilder) -> None:
         for var in sorted(builder.free_variables[builder.fn_info.fitem], key=lambda x: x.name):
             if isinstance(var, Var):
                 rtype = builder.type_to_rtype(var.type)
-                builder.add_var_to_env_class(var, rtype, env_for_func, reassign=False)
+                builder.add_var_to_env_class(
+                    var, rtype, env_for_func, reassign=False, prefix=prefix
+                )
 
     if builder.fn_info.fitem in builder.encapsulating_funcs:
         for nested_fn in builder.encapsulating_funcs[builder.fn_info.fitem]:
@@ -225,12 +240,16 @@ def add_vars_to_env(builder: IRBuilder) -> None:
                 # the same name and signature across conditional blocks
                 # will generate different callable classes, so the callable
                 # class that gets instantiated must be generic.
+                if nested_fn.is_generator:
+                    prefix = GENERATOR_ATTRIBUTE_PREFIX
                 builder.add_var_to_env_class(
-                    nested_fn, object_rprimitive, env_for_func, reassign=False
+                    nested_fn, object_rprimitive, env_for_func, reassign=False, prefix=prefix
                 )
 
 
-def setup_func_for_recursive_call(builder: IRBuilder, fdef: FuncDef, base: ImplicitClass) -> None:
+def setup_func_for_recursive_call(
+    builder: IRBuilder, fdef: FuncDef, base: ImplicitClass, prefix: str = ""
+) -> None:
     """Enable calling a nested function (with a callable class) recursively.
 
     Adds the instance of the callable class representing the given
@@ -240,7 +259,8 @@ def setup_func_for_recursive_call(builder: IRBuilder, fdef: FuncDef, base: Impli
     """
     # First, set the attribute of the environment class so that GetAttr can be called on it.
     prev_env = builder.fn_infos[-2].env_class
-    prev_env.attributes[fdef.name] = builder.type_to_rtype(fdef.type)
+    attr_name = prefix + fdef.name
+    prev_env.attributes[attr_name] = builder.type_to_rtype(fdef.type)
 
     if isinstance(base, GeneratorClass):
         # If we are dealing with a generator class, then we need to first get the register
@@ -252,7 +272,7 @@ def setup_func_for_recursive_call(builder: IRBuilder, fdef: FuncDef, base: Impli
 
     # Obtain the instance of the callable class representing the FuncDef, and add it to the
     # current environment.
-    val = builder.add(GetAttr(prev_env_reg, fdef.name, -1))
+    val = builder.add(GetAttr(prev_env_reg, attr_name, -1))
     target = builder.add_local_reg(fdef, object_rprimitive)
     builder.assign(target, val, -1)
 
diff --git a/mypyc/irbuild/expression.py b/mypyc/irbuild/expression.py
index c8c67cae309b..4409b1acff26 100644
--- a/mypyc/irbuild/expression.py
+++ b/mypyc/irbuild/expression.py
@@ -57,6 +57,7 @@
 from mypyc.ir.ops import (
     Assign,
     BasicBlock,
+    Call,
     ComparisonOp,
     Integer,
     LoadAddress,
@@ -69,6 +70,7 @@
     Value,
 )
 from mypyc.ir.rtypes import (
+    RInstance,
     RTuple,
     bool_rprimitive,
     int_rprimitive,
@@ -76,6 +78,7 @@
     is_int_rprimitive,
     is_list_rprimitive,
     is_none_rprimitive,
+    is_object_rprimitive,
     object_rprimitive,
     set_rprimitive,
 )
@@ -97,8 +100,8 @@
 )
 from mypyc.irbuild.specialize import apply_function_specialization, apply_method_specialization
 from mypyc.primitives.bytes_ops import bytes_slice_op
-from mypyc.primitives.dict_ops import dict_get_item_op, dict_new_op, dict_set_item_op
-from mypyc.primitives.generic_ops import iter_op
+from mypyc.primitives.dict_ops import dict_get_item_op, dict_new_op, exact_dict_set_item_op
+from mypyc.primitives.generic_ops import iter_op, name_op
 from mypyc.primitives.list_ops import list_append_op, list_extend_op, list_slice_op
 from mypyc.primitives.misc_ops import ellipsis_op, get_module_dict_op, new_slice_op, type_op
 from mypyc.primitives.registry import builtin_names
@@ -117,9 +120,7 @@ def transform_name_expr(builder: IRBuilder, expr: NameExpr) -> Value:
     if expr.node is None:
         builder.add(
             RaiseStandardError(
-                RaiseStandardError.RUNTIME_ERROR,
-                "mypyc internal error: should be unreachable",
-                expr.line,
+                RaiseStandardError.NAME_ERROR, f'name "{expr.name}" is not defined', expr.line
             )
         )
         return builder.none()
@@ -220,6 +221,18 @@ def transform_member_expr(builder: IRBuilder, expr: MemberExpr) -> Value:
     obj = builder.accept(expr.expr, can_borrow=can_borrow)
     rtype = builder.node_type(expr)
 
+    if (
+        is_object_rprimitive(obj.type)
+        and expr.name == "__name__"
+        and builder.options.capi_version >= (3, 11)
+    ):
+        return builder.primitive_op(name_op, [obj], expr.line)
+
+    if isinstance(obj.type, RInstance) and expr.name == "__class__":
+        # A non-native class could override "__class__" using "__getattribute__", so
+        # only apply to RInstance types.
+        return builder.primitive_op(type_op, [obj], expr.line)
+
     # Special case: for named tuples transform attribute access to faster index access.
     typ = get_proper_type(builder.types.get(expr.expr))
     if isinstance(typ, TupleType) and typ.partial_fallback.type.is_named_tuple:
@@ -361,7 +374,7 @@ def translate_method_call(builder: IRBuilder, expr: CallExpr, callee: MemberExpr
         and all(kind in (ARG_POS, ARG_NAMED) for kind in expr.arg_kinds)
     ):
         # Call a method via the *class*
-        assert isinstance(callee.expr.node, TypeInfo)
+        assert isinstance(callee.expr.node, TypeInfo), callee.expr.node
         ir = builder.mapper.type_to_ir[callee.expr.node]
         return call_classmethod(builder, ir, expr, callee)
     elif builder.is_module_member_expr(callee):
@@ -460,23 +473,42 @@ def translate_super_method_call(builder: IRBuilder, expr: CallExpr, callee: Supe
         if callee.name in base.method_decls:
             break
     else:
-        if (
-            ir.is_ext_class
-            and ir.builtin_base is None
-            and not ir.inherits_python
-            and callee.name == "__init__"
-            and len(expr.args) == 0
-        ):
-            # Call translates to object.__init__(self), which is a
-            # no-op, so omit the call.
-            return builder.none()
+        if ir.is_ext_class and ir.builtin_base is None and not ir.inherits_python:
+            if callee.name == "__init__" and len(expr.args) == 0:
+                # Call translates to object.__init__(self), which is a
+                # no-op, so omit the call.
+                return builder.none()
+            elif callee.name == "__new__":
+                # object.__new__(cls)
+                assert (
+                    len(expr.args) == 1
+                ), f"Expected object.__new__() call to have exactly 1 argument, got {len(expr.args)}"
+                typ_arg = expr.args[0]
+                method_args = builder.fn_info.fitem.arg_names
+                if (
+                    isinstance(typ_arg, NameExpr)
+                    and len(method_args) > 0
+                    and method_args[0] == typ_arg.name
+                ):
+                    subtype = builder.accept(expr.args[0])
+                    return builder.add(Call(ir.setup, [subtype], expr.line))
+
+        if callee.name == "__new__":
+            call = "super().__new__()"
+            if not ir.is_ext_class:
+                builder.error(f"{call} not supported for non-extension classes", expr.line)
+            if ir.inherits_python:
+                builder.error(
+                    f"{call} not supported for classes inheriting from non-native classes",
+                    expr.line,
+                )
         return translate_call(builder, expr, callee)
 
     decl = base.method_decl(callee.name)
     arg_values = [builder.accept(arg) for arg in expr.args]
     arg_kinds, arg_names = expr.arg_kinds.copy(), expr.arg_names.copy()
 
-    if decl.kind != FUNC_STATICMETHOD:
+    if decl.kind != FUNC_STATICMETHOD and decl.name != "__new__":
         # Grab first argument
         vself: Value = builder.self()
         if decl.kind == FUNC_CLASSMETHOD:
@@ -703,72 +735,9 @@ def transform_comparison_expr(builder: IRBuilder, e: ComparisonExpr) -> Value:
     # x in (...)/[...]
     # x not in (...)/[...]
     first_op = e.operators[0]
-    if (
-        first_op in ["in", "not in"]
-        and len(e.operators) == 1
-        and isinstance(e.operands[1], (TupleExpr, ListExpr))
-    ):
-        items = e.operands[1].items
-        n_items = len(items)
-        # x in y -> x == y[0] or ... or x == y[n]
-        # x not in y -> x != y[0] and ... and x != y[n]
-        # 16 is arbitrarily chosen to limit code size
-        if 1 < n_items < 16:
-            if e.operators[0] == "in":
-                bin_op = "or"
-                cmp_op = "=="
-            else:
-                bin_op = "and"
-                cmp_op = "!="
-            lhs = e.operands[0]
-            mypy_file = builder.graph["builtins"].tree
-            assert mypy_file is not None
-            info = mypy_file.names["bool"].node
-            assert isinstance(info, TypeInfo)
-            bool_type = Instance(info, [])
-            exprs = []
-            for item in items:
-                expr = ComparisonExpr([cmp_op], [lhs, item])
-                builder.types[expr] = bool_type
-                exprs.append(expr)
-
-            or_expr: Expression = exprs.pop(0)
-            for expr in exprs:
-                or_expr = OpExpr(bin_op, or_expr, expr)
-                builder.types[or_expr] = bool_type
-            return builder.accept(or_expr)
-        # x in [y]/(y) -> x == y
-        # x not in [y]/(y) -> x != y
-        elif n_items == 1:
-            if e.operators[0] == "in":
-                cmp_op = "=="
-            else:
-                cmp_op = "!="
-            e.operators = [cmp_op]
-            e.operands[1] = items[0]
-        # x in []/() -> False
-        # x not in []/() -> True
-        elif n_items == 0:
-            if e.operators[0] == "in":
-                return builder.false()
-            else:
-                return builder.true()
-
-    # x in {...}
-    # x not in {...}
-    if (
-        first_op in ("in", "not in")
-        and len(e.operators) == 1
-        and isinstance(e.operands[1], SetExpr)
-    ):
-        set_literal = precompute_set_literal(builder, e.operands[1])
-        if set_literal is not None:
-            lhs = e.operands[0]
-            result = builder.builder.primitive_op(
-                set_in_op, [builder.accept(lhs), set_literal], e.line, bool_rprimitive
-            )
-            if first_op == "not in":
-                return builder.unary_op(result, "not", e.line)
+    if first_op in ["in", "not in"] and len(e.operators) == 1:
+        result = try_specialize_in_expr(builder, first_op, e.operands[0], e.operands[1], e.line)
+        if result is not None:
             return result
 
     if len(e.operators) == 1:
@@ -814,6 +783,86 @@ def go(i: int, prev: Value) -> Value:
     return go(0, builder.accept(e.operands[0]))
 
 
+def try_specialize_in_expr(
+    builder: IRBuilder, op: str, lhs: Expression, rhs: Expression, line: int
+) -> Value | None:
+    left: Value | None = None
+    items: list[Value] | None = None
+
+    if isinstance(rhs, (TupleExpr, ListExpr)):
+        left = builder.accept(lhs)
+        items = [builder.accept(item) for item in rhs.items]
+    elif isinstance(builder.node_type(rhs), RTuple):
+        left = builder.accept(lhs)
+        tuple_val = builder.accept(rhs)
+        assert isinstance(tuple_val.type, RTuple)
+        items = [builder.add(TupleGet(tuple_val, i)) for i in range(len(tuple_val.type.types))]
+
+    if items is not None:
+        assert left is not None
+        n_items = len(items)
+        # x in y -> x == y[0] or ... or x == y[n]
+        # x not in y -> x != y[0] and ... and x != y[n]
+        if n_items > 1:
+            if op == "in":
+                cmp_op = "=="
+            else:
+                cmp_op = "!="
+            out = BasicBlock()
+            for item in items:
+                cmp = transform_basic_comparison(builder, cmp_op, left, item, line)
+                bool_val = builder.builder.bool_value(cmp)
+                next_block = BasicBlock()
+                if op == "in":
+                    builder.add_bool_branch(bool_val, out, next_block)
+                else:
+                    builder.add_bool_branch(bool_val, next_block, out)
+                builder.activate_block(next_block)
+            result_reg = Register(bool_rprimitive)
+            end = BasicBlock()
+            if op == "in":
+                values = builder.false(), builder.true()
+            else:
+                values = builder.true(), builder.false()
+            builder.assign(result_reg, values[0], line)
+            builder.goto(end)
+            builder.activate_block(out)
+            builder.assign(result_reg, values[1], line)
+            builder.goto(end)
+            builder.activate_block(end)
+            return result_reg
+        # x in [y]/(y) -> x == y
+        # x not in [y]/(y) -> x != y
+        elif n_items == 1:
+            if op == "in":
+                cmp_op = "=="
+            else:
+                cmp_op = "!="
+            right = items[0]
+            return transform_basic_comparison(builder, cmp_op, left, right, line)
+        # x in []/() -> False
+        # x not in []/() -> True
+        elif n_items == 0:
+            if op == "in":
+                return builder.false()
+            else:
+                return builder.true()
+
+    # x in {...}
+    # x not in {...}
+    if isinstance(rhs, SetExpr):
+        set_literal = precompute_set_literal(builder, rhs)
+        if set_literal is not None:
+            result = builder.builder.primitive_op(
+                set_in_op, [builder.accept(lhs), set_literal], line, bool_rprimitive
+            )
+            if op == "not in":
+                return builder.unary_op(result, "not", line)
+            return result
+
+    return None
+
+
 def translate_is_none(builder: IRBuilder, expr: Expression, negated: bool) -> Value:
     v = builder.accept(expr, can_borrow=True)
     return builder.binary_op(v, builder.none_object(), "is not" if negated else "is", expr.line)
@@ -1032,7 +1081,7 @@ def transform_dictionary_comprehension(builder: IRBuilder, o: DictionaryComprehe
     def gen_inner_stmts() -> None:
         k = builder.accept(o.key)
         v = builder.accept(o.value)
-        builder.primitive_op(dict_set_item_op, [builder.read(d), k, v], o.line)
+        builder.call_c(exact_dict_set_item_op, [builder.read(d), k, v], o.line)
 
     comprehension_helper(builder, loop_params, gen_inner_stmts, o.line)
     return builder.read(d)
diff --git a/mypyc/irbuild/for_helpers.py b/mypyc/irbuild/for_helpers.py
index c5b1d1273bef..762b41866a05 100644
--- a/mypyc/irbuild/for_helpers.py
+++ b/mypyc/irbuild/for_helpers.py
@@ -24,12 +24,15 @@
     TypeAlias,
 )
 from mypyc.ir.ops import (
+    ERR_NEVER,
     BasicBlock,
     Branch,
     Integer,
     IntOp,
     LoadAddress,
+    LoadErrorValue,
     LoadMem,
+    MethodCall,
     RaiseStandardError,
     Register,
     TupleGet,
@@ -37,21 +40,27 @@
     Value,
 )
 from mypyc.ir.rtypes import (
+    RInstance,
     RTuple,
     RType,
     bool_rprimitive,
+    c_pyssize_t_rprimitive,
     int_rprimitive,
     is_dict_rprimitive,
     is_fixed_width_rtype,
+    is_immutable_rprimitive,
     is_list_rprimitive,
     is_sequence_rprimitive,
     is_short_int_rprimitive,
     is_str_rprimitive,
     is_tuple_rprimitive,
+    object_pointer_rprimitive,
+    object_rprimitive,
     pointer_rprimitive,
     short_int_rprimitive,
 )
 from mypyc.irbuild.builder import IRBuilder
+from mypyc.irbuild.prepare import GENERATOR_HELPER_NAME
 from mypyc.irbuild.targets import AssignmentTarget, AssignmentTargetTuple
 from mypyc.primitives.dict_ops import (
     dict_check_size_op,
@@ -62,12 +71,14 @@
     dict_next_value_op,
     dict_value_iter_op,
 )
-from mypyc.primitives.exc_ops import no_err_occurred_op
+from mypyc.primitives.exc_ops import no_err_occurred_op, propagate_if_error_op
 from mypyc.primitives.generic_ops import aiter_op, anext_op, iter_op, next_op
 from mypyc.primitives.list_ops import list_append_op, list_get_item_unsafe_op, new_list_set_item_op
 from mypyc.primitives.misc_ops import stop_async_iteration_op
 from mypyc.primitives.registry import CFunctionDescription
 from mypyc.primitives.set_ops import set_add_op
+from mypyc.primitives.str_ops import str_get_item_unsafe_op
+from mypyc.primitives.tuple_ops import tuple_get_item_unsafe_op
 
 GenFunc = Callable[[], None]
 
@@ -195,9 +206,9 @@ def sequence_from_generator_preallocate_helper(
     there is no condition list in the generator and only one original sequence with
     one index is allowed.
 
-    e.g.  (1) tuple(f(x) for x in a_list/a_tuple)
-          (2) list(f(x) for x in a_list/a_tuple)
-          (3) [f(x) for x in a_list/a_tuple]
+    e.g.  (1) tuple(f(x) for x in a_list/a_tuple/a_str/a_bytes)
+          (2) list(f(x) for x in a_list/a_tuple/a_str/a_bytes)
+          (3) [f(x) for x in a_list/a_tuple/a_str/a_bytes]
     RTuple as an original sequence is not supported yet.
 
     Args:
@@ -214,7 +225,7 @@ def sequence_from_generator_preallocate_helper(
     """
     if len(gen.sequences) == 1 and len(gen.indices) == 1 and len(gen.condlists[0]) == 0:
         rtype = builder.node_type(gen.sequences[0])
-        if is_list_rprimitive(rtype) or is_tuple_rprimitive(rtype) or is_str_rprimitive(rtype):
+        if is_sequence_rprimitive(rtype):
             sequence = builder.accept(gen.sequences[0])
             length = builder.builder.builtin_len(sequence, gen.line, use_pyssize_t=True)
             target_op = empty_op_llbuilder(length, gen.line)
@@ -511,7 +522,15 @@ def make_for_loop_generator(
     # Default to a generic for loop.
     if iterable_expr_reg is None:
         iterable_expr_reg = builder.accept(expr)
-    for_obj = ForIterable(builder, index, body_block, loop_exit, line, nested)
+
+    it = iterable_expr_reg.type
+    for_obj: ForNativeGenerator | ForIterable
+    if isinstance(it, RInstance) and it.class_ir.has_method(GENERATOR_HELPER_NAME):
+        # Directly call generator object methods if iterating over a native generator.
+        for_obj = ForNativeGenerator(builder, index, body_block, loop_exit, line, nested)
+    else:
+        # Generic implementation that works of arbitrary iterables.
+        for_obj = ForIterable(builder, index, body_block, loop_exit, line, nested)
     item_type = builder._analyze_iterable_item_type(expr)
     item_rtype = builder.type_to_rtype(item_type)
     for_obj.init(iterable_expr_reg, item_rtype)
@@ -571,7 +590,9 @@ def gen_cleanup(self) -> None:
 
     def load_len(self, expr: Value | AssignmentTarget) -> Value:
         """A helper to get collection length, used by several subclasses."""
-        return self.builder.builder.builtin_len(self.builder.read(expr, self.line), self.line)
+        return self.builder.builder.builtin_len(
+            self.builder.read(expr, self.line), self.line, use_pyssize_t=True
+        )
 
 
 class ForIterable(ForGenerator):
@@ -623,6 +644,63 @@ def gen_cleanup(self) -> None:
         self.builder.call_c(no_err_occurred_op, [], self.line)
 
 
+class ForNativeGenerator(ForGenerator):
+    """Generate IR for a for loop over a native generator."""
+
+    def need_cleanup(self) -> bool:
+        # Create a new cleanup block for when the loop is finished.
+        return True
+
+    def init(self, expr_reg: Value, target_type: RType) -> None:
+        # Define target to contains the generator expression. It's also the iterator.
+        # If we are inside a generator function, spill these into the environment class.
+        builder = self.builder
+        self.iter_target = builder.maybe_spill(expr_reg)
+        self.target_type = target_type
+
+    def gen_condition(self) -> None:
+        builder = self.builder
+        line = self.line
+        self.return_value = Register(object_rprimitive)
+        err = builder.add(LoadErrorValue(object_rprimitive, undefines=True))
+        builder.assign(self.return_value, err, line)
+
+        # Call generated generator helper method, passing a PyObject ** as the final
+        # argument that will be used to store the return value in the return value
+        # register. We ignore the return value but the presence of a return value
+        # indicates that the generator has finished. This is faster than raising
+        # and catching StopIteration, which is the non-native way of doing this.
+        ptr = builder.add(LoadAddress(object_pointer_rprimitive, self.return_value))
+        nn = builder.none_object()
+        helper_call = MethodCall(
+            builder.read(self.iter_target), GENERATOR_HELPER_NAME, [nn, nn, nn, nn, ptr], line
+        )
+        # We provide custom handling for error values.
+        helper_call.error_kind = ERR_NEVER
+
+        self.next_reg = builder.add(helper_call)
+        builder.add(Branch(self.next_reg, self.loop_exit, self.body_block, Branch.IS_ERROR))
+
+    def begin_body(self) -> None:
+        # Assign the value obtained from the generator helper method to the
+        # lvalue so that it can be referenced by code in the body of the loop.
+        builder = self.builder
+        line = self.line
+        # We unbox here so that iterating with tuple unpacking generates a tuple based
+        # unpack instead of an iterator based one.
+        next_reg = builder.coerce(self.next_reg, self.target_type, line)
+        builder.assign(builder.get_assignment_target(self.index), next_reg, line)
+
+    def gen_step(self) -> None:
+        # Nothing to do here, since we get the next item as part of gen_condition().
+        pass
+
+    def gen_cleanup(self) -> None:
+        # If return value is NULL (it wasn't assigned to by the generator helper method),
+        # an exception was raised that we need to propagate.
+        self.builder.primitive_op(propagate_if_error_op, [self.return_value], self.line)
+
+
 class ForAsyncIterable(ForGenerator):
     """Generate IR for an async for loop."""
 
@@ -656,7 +734,7 @@ def gen_condition(self) -> None:
 
         def except_match() -> Value:
             addr = builder.add(LoadAddress(pointer_rprimitive, stop_async_iteration_op.src, line))
-            return builder.add(LoadMem(stop_async_iteration_op.type, addr))
+            return builder.add(LoadMem(stop_async_iteration_op.type, addr, borrow=True))
 
         def try_body() -> None:
             awaitable = builder.call_c(anext_op, [builder.read(self.iter_target)], line)
@@ -694,6 +772,10 @@ def unsafe_index(builder: IRBuilder, target: Value, index: Value, line: int) ->
     # so we just check manually.
     if is_list_rprimitive(target.type):
         return builder.primitive_op(list_get_item_unsafe_op, [target, index], line)
+    elif is_tuple_rprimitive(target.type):
+        return builder.call_c(tuple_get_item_unsafe_op, [target, index], line)
+    elif is_str_rprimitive(target.type):
+        return builder.call_c(str_get_item_unsafe_op, [target, index], line)
     else:
         return builder.gen_method_call(target, "__getitem__", [index], None, line)
 
@@ -704,19 +786,31 @@ class ForSequence(ForGenerator):
     Supports iterating in both forward and reverse.
     """
 
+    length_reg: Value | AssignmentTarget | None
+
     def init(self, expr_reg: Value, target_type: RType, reverse: bool) -> None:
+        assert is_sequence_rprimitive(expr_reg.type), expr_reg
         builder = self.builder
         self.reverse = reverse
         # Define target to contain the expression, along with the index that will be used
         # for the for-loop. If we are inside of a generator function, spill these into the
         # environment class.
         self.expr_target = builder.maybe_spill(expr_reg)
+        if is_immutable_rprimitive(expr_reg.type):
+            # If the expression is an immutable type, we can load the length just once.
+            self.length_reg = builder.maybe_spill(self.load_len(self.expr_target))
+        else:
+            # Otherwise, even if the length is known, we must recalculate the length
+            # at every iteration for compatibility with python semantics.
+            self.length_reg = None
         if not reverse:
-            index_reg: Value = Integer(0)
+            index_reg: Value = Integer(0, c_pyssize_t_rprimitive)
         else:
-            index_reg = builder.binary_op(
-                self.load_len(self.expr_target), Integer(1), "-", self.line
-            )
+            if self.length_reg is not None:
+                len_val = builder.read(self.length_reg)
+            else:
+                len_val = self.load_len(self.expr_target)
+            index_reg = builder.builder.int_sub(len_val, 1)
         self.index_target = builder.maybe_spill_assignable(index_reg)
         self.target_type = target_type
 
@@ -735,9 +829,13 @@ def gen_condition(self) -> None:
             second_check = BasicBlock()
             builder.add_bool_branch(comparison, second_check, self.loop_exit)
             builder.activate_block(second_check)
-        # For compatibility with python semantics we recalculate the length
-        # at every iteration.
-        len_reg = self.load_len(self.expr_target)
+        if self.length_reg is None:
+            # For compatibility with python semantics we recalculate the length
+            # at every iteration.
+            len_reg = self.load_len(self.expr_target)
+        else:
+            # (unless input is immutable type).
+            len_reg = builder.read(self.length_reg, line)
         comparison = builder.binary_op(builder.read(self.index_target, line), len_reg, "<", line)
         builder.add_bool_branch(comparison, self.body_block, self.loop_exit)
 
@@ -766,13 +864,7 @@ def gen_step(self) -> None:
         builder = self.builder
         line = self.line
         step = 1 if not self.reverse else -1
-        add = builder.int_op(
-            short_int_rprimitive,
-            builder.read(self.index_target, line),
-            Integer(step),
-            IntOp.ADD,
-            line,
-        )
+        add = builder.builder.int_add(builder.read(self.index_target, line), step)
         builder.assign(self.index_target, add, line)
 
 
@@ -902,7 +994,7 @@ def begin_body(self) -> None:
         value = builder.add(TupleGet(self.next_tuple, 3, line))
 
         # Coerce just in case e.g. key is itself a tuple to be unpacked.
-        assert isinstance(self.target_type, RTuple)
+        assert isinstance(self.target_type, RTuple), self.target_type
         key = builder.coerce(key, self.target_type.types[0], line)
         value = builder.coerce(value, self.target_type.types[1], line)
 
diff --git a/mypyc/irbuild/format_str_tokenizer.py b/mypyc/irbuild/format_str_tokenizer.py
index eaa4027ed768..5a35900006d2 100644
--- a/mypyc/irbuild/format_str_tokenizer.py
+++ b/mypyc/irbuild/format_str_tokenizer.py
@@ -12,7 +12,7 @@
 )
 from mypy.errors import Errors
 from mypy.messages import MessageBuilder
-from mypy.nodes import Context, Expression
+from mypy.nodes import Context, Expression, StrExpr
 from mypy.options import Options
 from mypyc.ir.ops import Integer, Value
 from mypyc.ir.rtypes import (
@@ -143,7 +143,9 @@ def convert_format_expr_to_str(
     for x, format_op in zip(exprs, format_ops):
         node_type = builder.node_type(x)
         if format_op == FormatOp.STR:
-            if is_str_rprimitive(node_type):
+            if is_str_rprimitive(node_type) or isinstance(
+                x, StrExpr
+            ):  # NOTE: why does mypyc think our fake StrExprs are not str rprimitives?
                 var_str = builder.accept(x)
             elif is_int_rprimitive(node_type) or is_short_int_rprimitive(node_type):
                 var_str = builder.primitive_op(int_to_str_op, [builder.accept(x)], line)
diff --git a/mypyc/irbuild/function.py b/mypyc/irbuild/function.py
index dbebc350bb6c..f0fc424aea54 100644
--- a/mypyc/irbuild/function.py
+++ b/mypyc/irbuild/function.py
@@ -29,7 +29,7 @@
     Var,
 )
 from mypy.types import CallableType, Type, UnboundType, get_proper_type
-from mypyc.common import LAMBDA_NAME, PROPSET_PREFIX, SELF_NAME
+from mypyc.common import FAST_PREFIX, LAMBDA_NAME, PROPSET_PREFIX, SELF_NAME
 from mypyc.ir.class_ir import ClassIR, NonExtClassInfo
 from mypyc.ir.func_ir import (
     FUNC_CLASSMETHOD,
@@ -76,7 +76,11 @@
 )
 from mypyc.irbuild.generator import gen_generator_func, gen_generator_func_body
 from mypyc.irbuild.targets import AssignmentTarget
-from mypyc.primitives.dict_ops import dict_get_method_with_none, dict_new_op, dict_set_item_op
+from mypyc.primitives.dict_ops import (
+    dict_get_method_with_none,
+    dict_new_op,
+    exact_dict_set_item_op,
+)
 from mypyc.primitives.generic_ops import py_setattr_op
 from mypyc.primitives.misc_ops import register_function
 from mypyc.primitives.registry import builtin_names
@@ -123,8 +127,8 @@ def transform_decorator(builder: IRBuilder, dec: Decorator) -> None:
 
     if decorated_func is not None:
         # Set the callable object representing the decorated function as a global.
-        builder.primitive_op(
-            dict_set_item_op,
+        builder.call_c(
+            exact_dict_set_item_op,
             [builder.load_globals_dict(), builder.load_str(dec.func.name), decorated_func],
             decorated_func.line,
         )
@@ -136,7 +140,7 @@ def transform_decorator(builder: IRBuilder, dec: Decorator) -> None:
 
 def transform_lambda_expr(builder: IRBuilder, expr: LambdaExpr) -> Value:
     typ = get_proper_type(builder.types[expr])
-    assert isinstance(typ, CallableType)
+    assert isinstance(typ, CallableType), typ
 
     runtime_args = []
     for arg, arg_type in zip(expr.arguments, typ.arg_types):
@@ -166,6 +170,7 @@ def gen_func_item(
     name: str,
     sig: FuncSignature,
     cdef: ClassDef | None = None,
+    make_ext_method: bool = False,
 ) -> tuple[FuncIR, Value | None]:
     """Generate and return the FuncIR for a given FuncDef.
 
@@ -217,7 +222,7 @@ def c() -> None:
     class_name = None
     if cdef:
         ir = builder.mapper.type_to_ir[cdef.info]
-        in_non_ext = not ir.is_ext_class
+        in_non_ext = not ir.is_ext_class and not make_ext_method
         class_name = cdef.name
 
     if is_singledispatch:
@@ -261,7 +266,7 @@ def c() -> None:
         )
 
         # Re-enter the FuncItem and visit the body of the function this time.
-        gen_generator_func_body(builder, fn_info, sig, func_reg)
+        gen_generator_func_body(builder, fn_info, func_reg)
     else:
         func_ir, func_reg = gen_func_body(builder, sig, cdef, is_singledispatch)
 
@@ -269,7 +274,7 @@ def c() -> None:
         # add the generated main singledispatch function
         builder.functions.append(func_ir)
         # create the dispatch function
-        assert isinstance(fitem, FuncDef)
+        assert isinstance(fitem, FuncDef), fitem
         return gen_dispatch_func_ir(builder, fitem, fn_info.name, name, sig)
 
     return func_ir, func_reg
@@ -336,8 +341,12 @@ def gen_func_ir(
         add_get_to_callable_class(builder, fn_info)
         func_reg = instantiate_callable_class(builder, fn_info)
     else:
-        assert isinstance(fn_info.fitem, FuncDef)
-        func_decl = builder.mapper.func_to_decl[fn_info.fitem]
+        fitem = fn_info.fitem
+        assert isinstance(fitem, FuncDef), fitem
+        func_decl = builder.mapper.func_to_decl[fitem]
+        if cdef and fn_info.name == FAST_PREFIX + func_decl.name:
+            # Special-cased version of a method has a separate FuncDecl, use that one.
+            func_decl = builder.mapper.type_to_ir[cdef.info].method_decls[fn_info.name]
         if fn_info.is_decorated or is_singledispatch_main_func:
             class_name = None if cdef is None else cdef.name
             func_decl = FuncDecl(
@@ -349,13 +358,9 @@ def gen_func_ir(
                 func_decl.is_prop_getter,
                 func_decl.is_prop_setter,
             )
-            func_ir = FuncIR(
-                func_decl, args, blocks, fn_info.fitem.line, traceback_name=fn_info.fitem.name
-            )
+            func_ir = FuncIR(func_decl, args, blocks, fitem.line, traceback_name=fitem.name)
         else:
-            func_ir = FuncIR(
-                func_decl, args, blocks, fn_info.fitem.line, traceback_name=fn_info.fitem.name
-            )
+            func_ir = FuncIR(func_decl, args, blocks, fitem.line, traceback_name=fitem.name)
     return (func_ir, func_reg)
 
 
@@ -456,6 +461,15 @@ def handle_non_ext_method(
 
     builder.add_to_non_ext_dict(non_ext, name, func_reg, fdef.line)
 
+    # If we identified that this non-extension class method can be special-cased for
+    # direct access during prepare phase, generate a "static" version of it.
+    class_ir = builder.mapper.type_to_ir[cdef.info]
+    name = FAST_PREFIX + fdef.name
+    if name in class_ir.method_decls:
+        func_ir, func_reg = gen_func_item(builder, fdef, name, sig, cdef, make_ext_method=True)
+        class_ir.methods[name] = func_ir
+        builder.functions.append(func_ir)
+
 
 def gen_func_ns(builder: IRBuilder) -> str:
     """Generate a namespace for a nested function using its outer function names."""
@@ -483,7 +497,7 @@ def load_decorated_func(builder: IRBuilder, fdef: FuncDef, orig_func_reg: Value)
     func_reg = orig_func_reg
     for d in reversed(decorators):
         decorator = d.accept(builder.visitor)
-        assert isinstance(decorator, Value)
+        assert isinstance(decorator, Value), decorator
         func_reg = builder.py_call(decorator, [func_reg], func_reg.line)
     return func_reg
 
@@ -816,7 +830,7 @@ def generate_singledispatch_dispatch_function(
     find_impl = builder.load_module_attr_by_fullname("functools._find_impl", line)
     registry = load_singledispatch_registry(builder, dispatch_func_obj, line)
     uncached_impl = builder.py_call(find_impl, [arg_type, registry], line)
-    builder.primitive_op(dict_set_item_op, [dispatch_cache, arg_type, uncached_impl], line)
+    builder.call_c(exact_dict_set_item_op, [dispatch_cache, arg_type, uncached_impl], line)
     builder.assign(impl_to_use, uncached_impl, line)
     builder.goto(call_func)
 
@@ -993,7 +1007,7 @@ def maybe_insert_into_registry_dict(builder: IRBuilder, fitem: FuncDef) -> None:
         registry = load_singledispatch_registry(builder, dispatch_func_obj, line)
         for typ in types:
             loaded_type = load_type(builder, typ, None, line)
-            builder.primitive_op(dict_set_item_op, [registry, loaded_type, to_insert], line)
+            builder.call_c(exact_dict_set_item_op, [registry, loaded_type, to_insert], line)
         dispatch_cache = builder.builder.get_attr(
             dispatch_func_obj, "dispatch_cache", dict_rprimitive, line
         )
diff --git a/mypyc/irbuild/generator.py b/mypyc/irbuild/generator.py
index 782cb4319757..b3a417ed6a3e 100644
--- a/mypyc/irbuild/generator.py
+++ b/mypyc/irbuild/generator.py
@@ -13,9 +13,9 @@
 from typing import Callable
 
 from mypy.nodes import ARG_OPT, FuncDef, Var
-from mypyc.common import ENV_ATTR_NAME, NEXT_LABEL_ATTR_NAME, SELF_NAME
+from mypyc.common import ENV_ATTR_NAME, GENERATOR_ATTRIBUTE_PREFIX, NEXT_LABEL_ATTR_NAME
 from mypyc.ir.class_ir import ClassIR
-from mypyc.ir.func_ir import FuncDecl, FuncIR, FuncSignature, RuntimeArg
+from mypyc.ir.func_ir import FuncDecl, FuncIR
 from mypyc.ir.ops import (
     NO_TRACEBACK_LINE_NO,
     BasicBlock,
@@ -32,7 +32,12 @@
     Unreachable,
     Value,
 )
-from mypyc.ir.rtypes import RInstance, int32_rprimitive, object_rprimitive
+from mypyc.ir.rtypes import (
+    RInstance,
+    int32_rprimitive,
+    object_pointer_rprimitive,
+    object_rprimitive,
+)
 from mypyc.irbuild.builder import IRBuilder, calculate_arg_defaults, gen_arg_defaults
 from mypyc.irbuild.context import FuncInfo, GeneratorClass
 from mypyc.irbuild.env_class import (
@@ -45,6 +50,7 @@
     setup_func_for_recursive_call,
 )
 from mypyc.irbuild.nonlocalcontrol import ExceptNonlocalControl
+from mypyc.irbuild.prepare import GENERATOR_HELPER_NAME
 from mypyc.primitives.exc_ops import (
     error_catch_op,
     exc_matches_op,
@@ -62,14 +68,14 @@ def gen_generator_func(
 ) -> tuple[FuncIR, Value | None]:
     """Generate IR for generator function that returns generator object."""
     setup_generator_class(builder)
-    load_env_registers(builder)
+    load_env_registers(builder, prefix=GENERATOR_ATTRIBUTE_PREFIX)
     gen_arg_defaults(builder)
     if builder.fn_info.can_merge_generator_and_env_classes():
         gen = instantiate_generator_class(builder)
         builder.fn_info._curr_env_reg = gen
-        finalize_env_class(builder)
+        finalize_env_class(builder, prefix=GENERATOR_ATTRIBUTE_PREFIX)
     else:
-        finalize_env_class(builder)
+        finalize_env_class(builder, prefix=GENERATOR_ATTRIBUTE_PREFIX)
         gen = instantiate_generator_class(builder)
     builder.add(Return(gen))
 
@@ -78,9 +84,7 @@ def gen_generator_func(
     return func_ir, func_reg
 
 
-def gen_generator_func_body(
-    builder: IRBuilder, fn_info: FuncInfo, sig: FuncSignature, func_reg: Value | None
-) -> None:
+def gen_generator_func_body(builder: IRBuilder, fn_info: FuncInfo, func_reg: Value | None) -> None:
     """Generate IR based on the body of a generator function.
 
     Add "__next__", "__iter__" and other generator methods to the generator
@@ -88,7 +92,7 @@ class that implements the function (each function gets a separate class).
 
     Return the symbol table for the body.
     """
-    builder.enter(fn_info, ret_type=sig.ret_type)
+    builder.enter(fn_info, ret_type=object_rprimitive)
     setup_env_for_generator_class(builder)
 
     load_outer_envs(builder, builder.fn_info.generator_class)
@@ -100,11 +104,13 @@ class that implements the function (each function gets a separate class).
         and top_level
         and top_level.add_nested_funcs_to_env
     ):
-        setup_func_for_recursive_call(builder, fitem, builder.fn_info.generator_class)
+        setup_func_for_recursive_call(
+            builder, fitem, builder.fn_info.generator_class, prefix=GENERATOR_ATTRIBUTE_PREFIX
+        )
     create_switch_for_generator_class(builder)
     add_raise_exception_blocks_to_generator_class(builder, fitem.line)
 
-    add_vars_to_env(builder)
+    add_vars_to_env(builder, prefix=GENERATOR_ATTRIBUTE_PREFIX)
 
     builder.accept(fitem.body)
     builder.maybe_add_implicit_return()
@@ -117,7 +123,7 @@ class that implements the function (each function gets a separate class).
 
     args, _, blocks, ret_type, fn_info = builder.leave()
 
-    add_methods_to_generator_class(builder, fn_info, sig, args, blocks, fitem.is_coroutine)
+    add_methods_to_generator_class(builder, fn_info, args, blocks, fitem.is_coroutine)
 
     # Evaluate argument defaults in the surrounding scope, since we
     # calculate them *once* when the function definition is evaluated.
@@ -153,9 +159,9 @@ def instantiate_generator_class(builder: IRBuilder) -> Value:
 
 
 def setup_generator_class(builder: IRBuilder) -> ClassIR:
-    name = f"{builder.fn_info.namespaced_name()}_gen"
-
-    generator_class_ir = ClassIR(name, builder.module_name, is_generated=True, is_final_class=True)
+    mapper = builder.mapper
+    assert isinstance(builder.fn_info.fitem, FuncDef), builder.fn_info.fitem
+    generator_class_ir = mapper.fdef_to_generator[builder.fn_info.fitem]
     if builder.fn_info.can_merge_generator_and_env_classes():
         builder.fn_info.env_class = generator_class_ir
     else:
@@ -215,50 +221,29 @@ def add_raise_exception_blocks_to_generator_class(builder: IRBuilder, line: int)
 def add_methods_to_generator_class(
     builder: IRBuilder,
     fn_info: FuncInfo,
-    sig: FuncSignature,
     arg_regs: list[Register],
     blocks: list[BasicBlock],
     is_coroutine: bool,
 ) -> None:
-    helper_fn_decl = add_helper_to_generator_class(builder, arg_regs, blocks, sig, fn_info)
-    add_next_to_generator_class(builder, fn_info, helper_fn_decl, sig)
-    add_send_to_generator_class(builder, fn_info, helper_fn_decl, sig)
+    helper_fn_decl = add_helper_to_generator_class(builder, arg_regs, blocks, fn_info)
+    add_next_to_generator_class(builder, fn_info, helper_fn_decl)
+    add_send_to_generator_class(builder, fn_info, helper_fn_decl)
     add_iter_to_generator_class(builder, fn_info)
-    add_throw_to_generator_class(builder, fn_info, helper_fn_decl, sig)
+    add_throw_to_generator_class(builder, fn_info, helper_fn_decl)
     add_close_to_generator_class(builder, fn_info)
     if is_coroutine:
         add_await_to_generator_class(builder, fn_info)
 
 
 def add_helper_to_generator_class(
-    builder: IRBuilder,
-    arg_regs: list[Register],
-    blocks: list[BasicBlock],
-    sig: FuncSignature,
-    fn_info: FuncInfo,
+    builder: IRBuilder, arg_regs: list[Register], blocks: list[BasicBlock], fn_info: FuncInfo
 ) -> FuncDecl:
     """Generates a helper method for a generator class, called by '__next__' and 'throw'."""
-    sig = FuncSignature(
-        (
-            RuntimeArg(SELF_NAME, object_rprimitive),
-            RuntimeArg("type", object_rprimitive),
-            RuntimeArg("value", object_rprimitive),
-            RuntimeArg("traceback", object_rprimitive),
-            RuntimeArg("arg", object_rprimitive),
-        ),
-        sig.ret_type,
-    )
-    helper_fn_decl = FuncDecl(
-        "__mypyc_generator_helper__",
-        fn_info.generator_class.ir.name,
-        builder.module_name,
-        sig,
-        internal=True,
-    )
+    helper_fn_decl = fn_info.generator_class.ir.method_decls[GENERATOR_HELPER_NAME]
     helper_fn_ir = FuncIR(
         helper_fn_decl, arg_regs, blocks, fn_info.fitem.line, traceback_name=fn_info.fitem.name
     )
-    fn_info.generator_class.ir.methods["__mypyc_generator_helper__"] = helper_fn_ir
+    fn_info.generator_class.ir.methods[GENERATOR_HELPER_NAME] = helper_fn_ir
     builder.functions.append(helper_fn_ir)
     fn_info.env_class.env_user_function = helper_fn_ir
 
@@ -271,9 +256,7 @@ def add_iter_to_generator_class(builder: IRBuilder, fn_info: FuncInfo) -> None:
         builder.add(Return(builder.self()))
 
 
-def add_next_to_generator_class(
-    builder: IRBuilder, fn_info: FuncInfo, fn_decl: FuncDecl, sig: FuncSignature
-) -> None:
+def add_next_to_generator_class(builder: IRBuilder, fn_info: FuncInfo, fn_decl: FuncDecl) -> None:
     """Generates the '__next__' method for a generator class."""
     with builder.enter_method(fn_info.generator_class.ir, "__next__", object_rprimitive, fn_info):
         none_reg = builder.none_object()
@@ -281,16 +264,21 @@ def add_next_to_generator_class(
         result = builder.add(
             Call(
                 fn_decl,
-                [builder.self(), none_reg, none_reg, none_reg, none_reg],
+                [
+                    builder.self(),
+                    none_reg,
+                    none_reg,
+                    none_reg,
+                    none_reg,
+                    Integer(0, object_pointer_rprimitive),
+                ],
                 fn_info.fitem.line,
             )
         )
         builder.add(Return(result))
 
 
-def add_send_to_generator_class(
-    builder: IRBuilder, fn_info: FuncInfo, fn_decl: FuncDecl, sig: FuncSignature
-) -> None:
+def add_send_to_generator_class(builder: IRBuilder, fn_info: FuncInfo, fn_decl: FuncDecl) -> None:
     """Generates the 'send' method for a generator class."""
     with builder.enter_method(fn_info.generator_class.ir, "send", object_rprimitive, fn_info):
         arg = builder.add_argument("arg", object_rprimitive)
@@ -299,16 +287,21 @@ def add_send_to_generator_class(
         result = builder.add(
             Call(
                 fn_decl,
-                [builder.self(), none_reg, none_reg, none_reg, builder.read(arg)],
+                [
+                    builder.self(),
+                    none_reg,
+                    none_reg,
+                    none_reg,
+                    builder.read(arg),
+                    Integer(0, object_pointer_rprimitive),
+                ],
                 fn_info.fitem.line,
             )
         )
         builder.add(Return(result))
 
 
-def add_throw_to_generator_class(
-    builder: IRBuilder, fn_info: FuncInfo, fn_decl: FuncDecl, sig: FuncSignature
-) -> None:
+def add_throw_to_generator_class(builder: IRBuilder, fn_info: FuncInfo, fn_decl: FuncDecl) -> None:
     """Generates the 'throw' method for a generator class."""
     with builder.enter_method(fn_info.generator_class.ir, "throw", object_rprimitive, fn_info):
         typ = builder.add_argument("type", object_rprimitive)
@@ -326,7 +319,14 @@ def add_throw_to_generator_class(
         result = builder.add(
             Call(
                 fn_decl,
-                [builder.self(), builder.read(typ), builder.read(val), builder.read(tb), none_reg],
+                [
+                    builder.self(),
+                    builder.read(typ),
+                    builder.read(val),
+                    builder.read(tb),
+                    none_reg,
+                    Integer(0, object_pointer_rprimitive),
+                ],
                 fn_info.fitem.line,
             )
         )
@@ -406,8 +406,15 @@ def setup_env_for_generator_class(builder: IRBuilder) -> None:
     # TODO: Use the right type here instead of object?
     exc_arg = builder.add_local(Var("arg"), object_rprimitive, is_arg=True)
 
+    # Parameter that can used to pass a pointer which can used instead of
+    # raising StopIteration(value). If the value is NULL, this won't be used.
+    stop_iter_value_arg = builder.add_local(
+        Var("stop_iter_ptr"), object_pointer_rprimitive, is_arg=True
+    )
+
     cls.exc_regs = (exc_type, exc_val, exc_tb)
     cls.send_arg_reg = exc_arg
+    cls.stop_iter_value_reg = stop_iter_value_arg
 
     cls.self_reg = builder.read(self_target, fitem.line)
     if builder.fn_info.can_merge_generator_and_env_classes():
@@ -424,7 +431,9 @@ def setup_env_for_generator_class(builder: IRBuilder) -> None:
 
     # Add arguments from the original generator function to the
     # environment of the generator class.
-    add_args_to_env(builder, local=False, base=cls, reassign=False)
+    add_args_to_env(
+        builder, local=False, base=cls, reassign=False, prefix=GENERATOR_ATTRIBUTE_PREFIX
+    )
 
     # Set the next label register for the generator class.
     cls.next_label_reg = builder.read(cls.next_label_target, fitem.line)
diff --git a/mypyc/irbuild/ll_builder.py b/mypyc/irbuild/ll_builder.py
index 6bc1eb9d0493..475d490a48f2 100644
--- a/mypyc/irbuild/ll_builder.py
+++ b/mypyc/irbuild/ll_builder.py
@@ -6,6 +6,7 @@
 
 from __future__ import annotations
 
+import sys
 from collections.abc import Sequence
 from typing import Callable, Final, Optional
 
@@ -16,6 +17,8 @@
 from mypyc.common import (
     BITMAP_BITS,
     FAST_ISINSTANCE_MAX_SUBCLASSES,
+    FAST_PREFIX,
+    IS_FREE_THREADED,
     MAX_LITERAL_SHORT_INT,
     MAX_SHORT_INT,
     MIN_LITERAL_SHORT_INT,
@@ -53,6 +56,7 @@
     KeepAlive,
     LoadAddress,
     LoadErrorValue,
+    LoadGlobal,
     LoadLiteral,
     LoadMem,
     LoadStatic,
@@ -93,8 +97,7 @@
     dict_rprimitive,
     float_rprimitive,
     int_rprimitive,
-    is_bit_rprimitive,
-    is_bool_rprimitive,
+    is_bool_or_bit_rprimitive,
     is_bytes_rprimitive,
     is_dict_rprimitive,
     is_fixed_width_rtype,
@@ -106,6 +109,7 @@
     is_int_rprimitive,
     is_list_rprimitive,
     is_none_rprimitive,
+    is_object_rprimitive,
     is_set_rprimitive,
     is_short_int_rprimitive,
     is_str_rprimitive,
@@ -126,6 +130,8 @@
 from mypyc.primitives.bytes_ops import bytes_compare
 from mypyc.primitives.dict_ops import (
     dict_build_op,
+    dict_copy,
+    dict_copy_op,
     dict_new_op,
     dict_ssize_t_size_op,
     dict_update_in_display_op,
@@ -137,6 +143,7 @@
     generic_ssize_t_len_op,
     py_call_op,
     py_call_with_kwargs_op,
+    py_call_with_posargs_op,
     py_getattr_op,
     py_method_call_op,
     py_vectorcall_method_op,
@@ -165,6 +172,7 @@
     fast_isinstance_op,
     none_object_op,
     not_implemented_op,
+    set_immortal_op,
     var_object_size,
 )
 from mypyc.primitives.registry import (
@@ -175,8 +183,19 @@
     unary_ops,
 )
 from mypyc.primitives.set_ops import new_set_op
-from mypyc.primitives.str_ops import str_check_if_true, str_ssize_t_size_op, unicode_compare
-from mypyc.primitives.tuple_ops import list_tuple_op, new_tuple_op, new_tuple_with_length_op
+from mypyc.primitives.str_ops import (
+    str_check_if_true,
+    str_eq,
+    str_ssize_t_size_op,
+    unicode_compare,
+)
+from mypyc.primitives.tuple_ops import (
+    list_tuple_op,
+    load_empty_tuple_constant_op,
+    new_tuple_op,
+    new_tuple_with_length_op,
+    sequence_tuple_op,
+)
 from mypyc.rt_subtype import is_runtime_subtype
 from mypyc.sametype import is_same_type
 from mypyc.subtype import is_subtype
@@ -282,6 +301,9 @@ def goto_and_activate(self, block: BasicBlock) -> None:
     def keep_alive(self, values: list[Value], *, steal: bool = False) -> None:
         self.add(KeepAlive(values, steal=steal))
 
+    def load_mem(self, ptr: Value, value_type: RType, *, borrow: bool = False) -> Value:
+        return self.add(LoadMem(value_type, ptr, borrow=borrow))
+
     def push_error_handler(self, handler: BasicBlock | None) -> None:
         self.error_handlers.append(handler)
 
@@ -316,14 +338,20 @@ def box(self, src: Value) -> Value:
             return src
 
     def unbox_or_cast(
-        self, src: Value, target_type: RType, line: int, *, can_borrow: bool = False
+        self,
+        src: Value,
+        target_type: RType,
+        line: int,
+        *,
+        can_borrow: bool = False,
+        unchecked: bool = False,
     ) -> Value:
         if target_type.is_unboxed:
             return self.add(Unbox(src, target_type, line))
         else:
             if can_borrow:
                 self.keep_alives.append(src)
-            return self.add(Cast(src, target_type, line, borrow=can_borrow))
+            return self.add(Cast(src, target_type, line, borrow=can_borrow, unchecked=unchecked))
 
     def coerce(
         self,
@@ -376,16 +404,12 @@ def coerce(
             ):
                 # Equivalent types
                 return src
-            elif (is_bool_rprimitive(src_type) or is_bit_rprimitive(src_type)) and is_tagged(
-                target_type
-            ):
+            elif is_bool_or_bit_rprimitive(src_type) and is_tagged(target_type):
                 shifted = self.int_op(
                     bool_rprimitive, src, Integer(1, bool_rprimitive), IntOp.LEFT_SHIFT
                 )
                 return self.add(Extend(shifted, target_type, signed=False))
-            elif (
-                is_bool_rprimitive(src_type) or is_bit_rprimitive(src_type)
-            ) and is_fixed_width_rtype(target_type):
+            elif is_bool_or_bit_rprimitive(src_type) and is_fixed_width_rtype(target_type):
                 return self.add(Extend(src, target_type, signed=False))
             elif isinstance(src, Integer) and is_float_rprimitive(target_type):
                 if is_tagged(src_type):
@@ -432,7 +456,7 @@ def coerce(
 
     def coerce_int_to_fixed_width(self, src: Value, target_type: RType, line: int) -> Value:
         assert is_fixed_width_rtype(target_type), target_type
-        assert isinstance(target_type, RPrimitive)
+        assert isinstance(target_type, RPrimitive), target_type
 
         res = Register(target_type)
 
@@ -538,10 +562,11 @@ def coerce_fixed_width_to_int(self, src: Value, line: int) -> Value:
                 line,
             )
 
-        assert is_fixed_width_rtype(src.type)
-        assert isinstance(src.type, RPrimitive)
         src_type = src.type
 
+        assert is_fixed_width_rtype(src_type), src_type
+        assert isinstance(src_type, RPrimitive), src_type
+
         res = Register(int_rprimitive)
 
         fast, fast2, slow, end = BasicBlock(), BasicBlock(), BasicBlock(), BasicBlock()
@@ -659,7 +684,7 @@ def other() -> Value:
 
     def get_type_of_obj(self, obj: Value, line: int) -> Value:
         ob_type_address = self.add(GetElementPtr(obj, PyObject, "ob_type", line))
-        ob_type = self.add(LoadMem(object_rprimitive, ob_type_address))
+        ob_type = self.load_mem(ob_type_address, object_rprimitive, borrow=True)
         self.add(KeepAlive([obj]))
         return ob_type
 
@@ -781,10 +806,52 @@ def _construct_varargs(
         for value, kind, name in args:
             if kind == ARG_STAR:
                 if star_result is None:
+                    # star args fastpath
+                    if len(args) == 1:
+                        # fn(*args)
+                        if is_list_rprimitive(value.type):
+                            value = self.primitive_op(list_tuple_op, [value], line)
+                        elif not is_tuple_rprimitive(value.type) and not isinstance(
+                            value.type, RTuple
+                        ):
+                            value = self.primitive_op(sequence_tuple_op, [value], line)
+                        return value, None
+                    elif len(args) == 2 and args[1][1] == ARG_STAR2:
+                        # fn(*args, **kwargs)
+                        # TODO: extend to cover(*args, **k, **w, **a, **r, **g, **s)
+                        if is_tuple_rprimitive(value.type) or isinstance(value.type, RTuple):
+                            star_result = value
+                        elif is_list_rprimitive(value.type):
+                            star_result = self.primitive_op(list_tuple_op, [value], line)
+                        else:
+                            star_result = self.primitive_op(sequence_tuple_op, [value], line)
+
+                        star2_arg = args[1]
+                        star2_value = star2_arg[0]
+                        if is_dict_rprimitive(star2_value.type):
+                            star2_fastpath_op = dict_copy_op
+                        else:
+                            star2_fastpath_op = dict_copy
+                        return star_result, self.primitive_op(
+                            star2_fastpath_op, [star2_value], line
+                        )
+                        # elif ...: TODO extend this to optimize fn(*args, k=1, **kwargs) case
+                    # TODO optimize this case using the length utils - currently in review
                     star_result = self.new_list_op(star_values, line)
                 self.primitive_op(list_extend_op, [star_result, value], line)
             elif kind == ARG_STAR2:
                 if star2_result is None:
+                    if len(args) == 1:
+                        # early exit with fastpath if the only arg is ARG_STAR2
+                        # TODO: can we maintain an empty tuple in memory and just reuse it again and again?
+                        if is_dict_rprimitive(value.type):
+                            star2_fastpath_op = dict_copy_op
+                        else:
+                            star2_fastpath_op = dict_copy
+                        return self.new_tuple([], line), self.primitive_op(
+                            star2_fastpath_op, [value], line
+                        )
+
                     star2_result = self._create_dict(star2_keys, star2_values, line)
 
                 self.call_c(dict_update_in_display_op, [star2_result, value], line=line)
@@ -878,9 +945,11 @@ def _construct_varargs(
             # tuple. Otherwise create the tuple from the list.
             if star_result is None:
                 star_result = self.new_tuple(star_values, line)
-            else:
+            elif not is_tuple_rprimitive(star_result.type):
+                # if star_result is a tuple we took the fast path
                 star_result = self.primitive_op(list_tuple_op, [star_result], line)
-        if has_star2 and star2_result is None:
+        if has_star2 and star2_result is None and len(star2_keys) > 0:
+            # TODO: use dict_copy_op for simple cases of **kwargs
             star2_result = self._create_dict(star2_keys, star2_values, line)
 
         return star_result, star2_result
@@ -905,13 +974,16 @@ def py_call(
         if arg_kinds is None or all(kind == ARG_POS for kind in arg_kinds):
             return self.call_c(py_call_op, [function] + arg_values, line)
 
-        # Otherwise fallback to py_call_with_kwargs_op.
+        # Otherwise fallback to py_call_with_posargs_op or py_call_with_kwargs_op.
         assert arg_names is not None
 
         pos_args_tuple, kw_args_dict = self._construct_varargs(
             list(zip(arg_values, arg_kinds, arg_names)), line, has_star=True, has_star2=True
         )
-        assert pos_args_tuple and kw_args_dict
+        assert pos_args_tuple
+
+        if kw_args_dict is None:
+            return self.call_c(py_call_with_posargs_op, [function, pos_args_tuple], line)
 
         return self.call_c(py_call_with_kwargs_op, [function, pos_args_tuple, kw_args_dict], line)
 
@@ -1110,8 +1182,7 @@ def native_args_to_positional(
                 assert star_arg
                 output_arg = star_arg
             elif arg.kind == ARG_STAR2:
-                assert star2_arg
-                output_arg = star2_arg
+                output_arg = star2_arg or self._create_dict([], [], line)
             elif not lst:
                 if is_fixed_width_rtype(arg.type):
                     output_arg = Integer(0, arg.type)
@@ -1164,11 +1235,13 @@ def gen_method_call(
             return self.py_method_call(base, name, arg_values, line, arg_kinds, arg_names)
 
         # If the base type is one of ours, do a MethodCall
+        fast_name = FAST_PREFIX + name
         if (
             isinstance(base.type, RInstance)
-            and base.type.class_ir.is_ext_class
+            and (base.type.class_ir.is_ext_class or base.type.class_ir.has_method(fast_name))
             and not base.type.class_ir.builtin_base
         ):
+            name = name if base.type.class_ir.is_ext_class else fast_name
             if base.type.class_ir.has_method(name):
                 decl = base.type.class_ir.method_decl(name)
                 if arg_kinds is None:
@@ -1247,6 +1320,14 @@ def none_object(self) -> Value:
         """Load Python None value (type: object_rprimitive)."""
         return self.add(LoadAddress(none_object_op.type, none_object_op.src, line=-1))
 
+    def true_object(self) -> Value:
+        """Load Python True object (type: object_rprimitive)."""
+        return self.add(LoadGlobal(object_rprimitive, "Py_True"))
+
+    def false_object(self) -> Value:
+        """Load Python False object (type: object_rprimitive)."""
+        return self.add(LoadGlobal(object_rprimitive, "Py_False"))
+
     def load_int(self, value: int) -> Value:
         """Load a tagged (Python) integer literal value."""
         if value > MAX_LITERAL_SHORT_INT or value < MIN_LITERAL_SHORT_INT:
@@ -1330,13 +1411,11 @@ def binary_op(self, lreg: Value, rreg: Value, op: str, line: int) -> Value:
         # Special case various ops
         if op in ("is", "is not"):
             return self.translate_is_op(lreg, rreg, op, line)
-        # TODO: modify 'str' to use same interface as 'compare_bytes' as it avoids
-        # call to PyErr_Occurred()
-        if is_str_rprimitive(ltype) and is_str_rprimitive(rtype) and op in ("==", "!="):
-            return self.compare_strings(lreg, rreg, op, line)
-        if is_bytes_rprimitive(ltype) and is_bytes_rprimitive(rtype) and op in ("==", "!="):
-            return self.compare_bytes(lreg, rreg, op, line)
-        if is_bool_rprimitive(ltype) and is_bool_rprimitive(rtype) and op in BOOL_BINARY_OPS:
+        if (
+            is_bool_or_bit_rprimitive(ltype)
+            and is_bool_or_bit_rprimitive(rtype)
+            and op in BOOL_BINARY_OPS
+        ):
             if op in ComparisonOp.signed_ops:
                 return self.bool_comparison_op(lreg, rreg, op, line)
             else:
@@ -1350,7 +1429,7 @@ def binary_op(self, lreg: Value, rreg: Value, op: str, line: int) -> Value:
                     op_id = int_op_to_id[op]
                 else:
                     op_id = IntOp.DIV
-                if is_bool_rprimitive(rtype) or is_bit_rprimitive(rtype):
+                if is_bool_or_bit_rprimitive(rtype):
                     rreg = self.coerce(rreg, ltype, line)
                     rtype = ltype
                 if is_fixed_width_rtype(rtype) or is_tagged(rtype):
@@ -1362,7 +1441,7 @@ def binary_op(self, lreg: Value, rreg: Value, op: str, line: int) -> Value:
             elif op in ComparisonOp.signed_ops:
                 if is_int_rprimitive(rtype):
                     rreg = self.coerce_int_to_fixed_width(rreg, ltype, line)
-                elif is_bool_rprimitive(rtype) or is_bit_rprimitive(rtype):
+                elif is_bool_or_bit_rprimitive(rtype):
                     rreg = self.coerce(rreg, ltype, line)
                 op_id = ComparisonOp.signed_ops[op]
                 if is_fixed_width_rtype(rreg.type):
@@ -1382,13 +1461,13 @@ def binary_op(self, lreg: Value, rreg: Value, op: str, line: int) -> Value:
                     )
                 if is_tagged(ltype):
                     return self.fixed_width_int_op(rtype, lreg, rreg, op_id, line)
-                if is_bool_rprimitive(ltype) or is_bit_rprimitive(ltype):
+                if is_bool_or_bit_rprimitive(ltype):
                     lreg = self.coerce(lreg, rtype, line)
                     return self.fixed_width_int_op(rtype, lreg, rreg, op_id, line)
             elif op in ComparisonOp.signed_ops:
                 if is_int_rprimitive(ltype):
                     lreg = self.coerce_int_to_fixed_width(lreg, rtype, line)
-                elif is_bool_rprimitive(ltype) or is_bit_rprimitive(ltype):
+                elif is_bool_or_bit_rprimitive(ltype):
                     lreg = self.coerce(lreg, rtype, line)
                 op_id = ComparisonOp.signed_ops[op]
                 if isinstance(lreg, Integer):
@@ -1427,6 +1506,7 @@ def binary_op(self, lreg: Value, rreg: Value, op: str, line: int) -> Value:
     def dunder_op(self, lreg: Value, rreg: Value | None, op: str, line: int) -> Value | None:
         """
         Dispatch a dunder method if applicable.
+
         For example for `a + b` it will use `a.__add__(b)` which can lead to higher performance
         due to the fact that the method could be already compiled and optimized instead of going
         all the way through `PyNumber_Add(a, b)` python api (making a jump into the python DL).
@@ -1471,6 +1551,15 @@ def check_tagged_short_int(self, val: Value, line: int, negated: bool = False) -
 
     def compare_strings(self, lhs: Value, rhs: Value, op: str, line: int) -> Value:
         """Compare two strings"""
+        if op == "==":
+            return self.primitive_op(str_eq, [lhs, rhs], line)
+        elif op == "!=":
+            eq = self.primitive_op(str_eq, [lhs, rhs], line)
+            return self.add(ComparisonOp(eq, self.false(), ComparisonOp.EQ, line))
+
+        # TODO: modify 'str' to use same interface as 'compare_bytes' as it would avoid
+        # call to PyErr_Occurred() below
+
         compare_result = self.call_c(unicode_compare, [lhs, rhs], line)
         error_constant = Integer(-1, c_int_rprimitive, line)
         compare_error_check = self.add(
@@ -1504,9 +1593,13 @@ def compare_bytes(self, lhs: Value, rhs: Value, op: str, line: int) -> Value:
     def compare_tuples(self, lhs: Value, rhs: Value, op: str, line: int = -1) -> Value:
         """Compare two tuples item by item"""
         # type cast to pass mypy check
-        assert isinstance(lhs.type, RTuple) and isinstance(rhs.type, RTuple)
+        assert isinstance(lhs.type, RTuple) and isinstance(rhs.type, RTuple), (lhs.type, rhs.type)
         equal = True if op == "==" else False
         result = Register(bool_rprimitive)
+        # tuples of different lengths
+        if len(lhs.type.types) != len(rhs.type.types):
+            self.add(Assign(result, self.false() if equal else self.true(), line))
+            return result
         # empty tuples
         if len(lhs.type.types) == 0 and len(rhs.type.types) == 0:
             self.add(Assign(result, self.true() if equal else self.false(), line))
@@ -1530,7 +1623,7 @@ def compare_tuples(self, lhs: Value, rhs: Value, op: str, line: int = -1) -> Val
             compare = self.binary_op(lhs_item, rhs_item, op, line)
             # Cast to bool if necessary since most types uses comparison returning a object type
             # See generic_ops.py for more information
-            if not is_bool_rprimitive(compare.type):
+            if not is_bool_or_bit_rprimitive(compare.type):
                 compare = self.primitive_op(bool_op, [compare], line)
             if i < len(lhs.type.types) - 1:
                 branch = Branch(compare, early_stop, check_blocks[i + 1], Branch.BOOL)
@@ -1549,7 +1642,7 @@ def compare_tuples(self, lhs: Value, rhs: Value, op: str, line: int = -1) -> Val
 
     def translate_instance_contains(self, inst: Value, item: Value, op: str, line: int) -> Value:
         res = self.gen_method_call(inst, "__contains__", [item], None, line)
-        if not is_bool_rprimitive(res.type):
+        if not is_bool_or_bit_rprimitive(res.type):
             res = self.primitive_op(bool_op, [res], line)
         if op == "not in":
             res = self.bool_bitwise_op(res, Integer(1, rtype=bool_rprimitive), "^", line)
@@ -1570,55 +1663,102 @@ def bool_comparison_op(self, lreg: Value, rreg: Value, op: str, line: int) -> Va
         op_id = ComparisonOp.signed_ops[op]
         return self.comparison_op(lreg, rreg, op_id, line)
 
-    def unary_not(self, value: Value, line: int) -> Value:
-        mask = Integer(1, value.type, line)
-        return self.int_op(value.type, value, mask, IntOp.XOR, line)
+    def _non_specialized_unary_op(self, value: Value, op: str, line: int) -> Value:
+        if isinstance(value.type, RInstance):
+            result = self.dunder_op(value, None, op, line)
+            if result is not None:
+                return result
+        primitive_ops_candidates = unary_ops.get(op, [])
+        target = self.matching_primitive_op(primitive_ops_candidates, [value], line)
+        assert target, "Unsupported unary operation: %s" % op
+        return target
 
-    def unary_op(self, value: Value, expr_op: str, line: int) -> Value:
-        typ = value.type
-        if is_bool_rprimitive(typ) or is_bit_rprimitive(typ):
-            if expr_op == "not":
-                return self.unary_not(value, line)
-            if expr_op == "+":
-                return value
-        if is_fixed_width_rtype(typ):
-            if expr_op == "-":
-                # Translate to '0 - x'
-                return self.int_op(typ, Integer(0, typ), value, IntOp.SUB, line)
-            elif expr_op == "~":
-                if typ.is_signed:
-                    # Translate to 'x ^ -1'
-                    return self.int_op(typ, value, Integer(-1, typ), IntOp.XOR, line)
-                else:
-                    # Translate to 'x ^ 0xff...'
-                    mask = (1 << (typ.size * 8)) - 1
-                    return self.int_op(typ, value, Integer(mask, typ), IntOp.XOR, line)
-            elif expr_op == "+":
-                return value
-        if is_float_rprimitive(typ):
-            if expr_op == "-":
-                return self.add(FloatNeg(value, line))
-            elif expr_op == "+":
-                return value
+    def unary_not(self, value: Value, line: int, *, likely_bool: bool = False) -> Value:
+        """Perform unary 'not'.
 
+        Args:
+            likely_bool: The operand is likely a bool value, even if the type is something
+                more general, so specialize for bool values
+        """
+        typ = value.type
+        if is_bool_or_bit_rprimitive(typ):
+            mask = Integer(1, typ, line)
+            return self.int_op(typ, value, mask, IntOp.XOR, line)
+        if likely_bool and is_object_rprimitive(typ):
+            # First quickly check if it's a bool, and otherwise fall back to generic op.
+            res = Register(bit_rprimitive)
+            false, not_false, true, other = BasicBlock(), BasicBlock(), BasicBlock(), BasicBlock()
+            out = BasicBlock()
+            cmp = self.add(ComparisonOp(value, self.true_object(), ComparisonOp.EQ, line))
+            self.add(Branch(cmp, false, not_false, Branch.BOOL))
+            self.activate_block(false)
+            self.add(Assign(res, self.false()))
+            self.goto(out)
+            self.activate_block(not_false)
+            cmp = self.add(ComparisonOp(value, self.false_object(), ComparisonOp.EQ, line))
+            self.add(Branch(cmp, true, other, Branch.BOOL))
+            self.activate_block(true)
+            self.add(Assign(res, self.true()))
+            self.goto(out)
+            self.activate_block(other)
+            val = self._non_specialized_unary_op(value, "not", line)
+            self.add(Assign(res, val))
+            self.goto(out)
+            self.activate_block(out)
+            return res
+        return self._non_specialized_unary_op(value, "not", line)
+
+    def unary_minus(self, value: Value, line: int) -> Value:
+        """Perform unary '-'."""
+        typ = value.type
         if isinstance(value, Integer):
             # TODO: Overflow? Unsigned?
-            num = value.value
-            if is_short_int_rprimitive(typ):
-                num >>= 1
-            return Integer(-num, typ, value.line)
-        if is_tagged(typ) and expr_op == "+":
+            return Integer(-value.numeric_value(), typ, line)
+        elif isinstance(value, Float):
+            return Float(-value.value, line)
+        elif is_fixed_width_rtype(typ):
+            # Translate to '0 - x'
+            return self.int_op(typ, Integer(0, typ), value, IntOp.SUB, line)
+        elif is_float_rprimitive(typ):
+            return self.add(FloatNeg(value, line))
+        return self._non_specialized_unary_op(value, "-", line)
+
+    def unary_plus(self, value: Value, line: int) -> Value:
+        """Perform unary '+'."""
+        typ = value.type
+        if (
+            is_tagged(typ)
+            or is_float_rprimitive(typ)
+            or is_bool_or_bit_rprimitive(typ)
+            or is_fixed_width_rtype(typ)
+        ):
             return value
-        if isinstance(value, Float):
-            return Float(-value.value, value.line)
-        if isinstance(typ, RInstance):
-            result = self.dunder_op(value, None, expr_op, line)
-            if result is not None:
-                return result
-        primitive_ops_candidates = unary_ops.get(expr_op, [])
-        target = self.matching_primitive_op(primitive_ops_candidates, [value], line)
-        assert target, "Unsupported unary operation: %s" % expr_op
-        return target
+        return self._non_specialized_unary_op(value, "+", line)
+
+    def unary_invert(self, value: Value, line: int) -> Value:
+        """Perform unary '~'."""
+        typ = value.type
+        if is_fixed_width_rtype(typ):
+            if typ.is_signed:
+                # Translate to 'x ^ -1'
+                return self.int_op(typ, value, Integer(-1, typ), IntOp.XOR, line)
+            else:
+                # Translate to 'x ^ 0xff...'
+                mask = (1 << (typ.size * 8)) - 1
+                return self.int_op(typ, value, Integer(mask, typ), IntOp.XOR, line)
+        return self._non_specialized_unary_op(value, "~", line)
+
+    def unary_op(self, value: Value, op: str, line: int) -> Value:
+        """Perform a unary operation."""
+        if op == "not":
+            return self.unary_not(value, line)
+        elif op == "-":
+            return self.unary_minus(value, line)
+        elif op == "+":
+            return self.unary_plus(value, line)
+        elif op == "~":
+            return self.unary_invert(value, line)
+        raise RuntimeError("Unsupported unary operation: %s" % op)
 
     def make_dict(self, key_value_pairs: Sequence[DictEntry], line: int) -> Value:
         result: Value | None = None
@@ -1734,7 +1874,7 @@ def bool_value(self, value: Value) -> Value:
 
         The result type can be bit_rprimitive or bool_rprimitive.
         """
-        if is_bool_rprimitive(value.type) or is_bit_rprimitive(value.type):
+        if is_bool_or_bit_rprimitive(value.type):
             result = value
         elif is_runtime_subtype(value.type, int_rprimitive):
             zero = Integer(0, short_int_rprimitive)
@@ -2090,6 +2230,33 @@ def float_mod(self, lhs: Value, rhs: Value, line: int) -> Value:
     def compare_floats(self, lhs: Value, rhs: Value, op: int, line: int) -> Value:
         return self.add(FloatComparisonOp(lhs, rhs, op, line))
 
+    def int_add(self, lhs: Value, rhs: Value | int) -> Value:
+        """Helper to add two native integers.
+
+        The result has the type of lhs.
+        """
+        if isinstance(rhs, int):
+            rhs = Integer(rhs, lhs.type)
+        return self.int_op(lhs.type, lhs, rhs, IntOp.ADD, line=-1)
+
+    def int_sub(self, lhs: Value, rhs: Value | int) -> Value:
+        """Helper to subtract a native integer from another one.
+
+        The result has the type of lhs.
+        """
+        if isinstance(rhs, int):
+            rhs = Integer(rhs, lhs.type)
+        return self.int_op(lhs.type, lhs, rhs, IntOp.SUB, line=-1)
+
+    def int_mul(self, lhs: Value, rhs: Value | int) -> Value:
+        """Helper to multiply two native integers.
+
+        The result has the type of lhs.
+        """
+        if isinstance(rhs, int):
+            rhs = Integer(rhs, lhs.type)
+        return self.int_op(lhs.type, lhs, rhs, IntOp.MUL, line=-1)
+
     def fixed_width_int_op(
         self, type: RPrimitive, lhs: Value, rhs: Value, op: int, line: int
     ) -> Value:
@@ -2220,7 +2387,7 @@ def builtin_len(self, val: Value, line: int, use_pyssize_t: bool = False) -> Val
             size_value = self.primitive_op(var_object_size, [val], line)
         elif is_set_rprimitive(typ) or is_frozenset_rprimitive(typ):
             elem_address = self.add(GetElementPtr(val, PySetObject, "used"))
-            size_value = self.add(LoadMem(c_pyssize_t_rprimitive, elem_address))
+            size_value = self.load_mem(elem_address, c_pyssize_t_rprimitive)
             self.add(KeepAlive([val]))
         elif is_dict_rprimitive(typ):
             size_value = self.call_c(dict_ssize_t_size_op, [val], line)
@@ -2258,8 +2425,11 @@ def builtin_len(self, val: Value, line: int, use_pyssize_t: bool = False) -> Val
             return self.call_c(generic_len_op, [val], line)
 
     def new_tuple(self, items: list[Value], line: int) -> Value:
-        size: Value = Integer(len(items), c_pyssize_t_rprimitive)
-        return self.call_c(new_tuple_op, [size] + items, line)
+        if items:
+            size: Value = Integer(len(items), c_pyssize_t_rprimitive)
+            return self.call_c(new_tuple_op, [size] + items, line)
+        else:
+            return self.call_c(load_empty_tuple_constant_op, [], line)
 
     def new_tuple_with_length(self, length: Value, line: int) -> Value:
         """This function returns an uninitialized tuple.
@@ -2278,6 +2448,11 @@ def new_tuple_with_length(self, length: Value, line: int) -> Value:
     def int_to_float(self, n: Value, line: int) -> Value:
         return self.primitive_op(int_to_float_op, [n], line)
 
+    def set_immortal_if_free_threaded(self, v: Value, line: int) -> None:
+        """Make an object immortal on free-threaded builds (to avoid contention)."""
+        if IS_FREE_THREADED and sys.version_info >= (3, 14):
+            self.primitive_op(set_immortal_op, [v], line)
+
     # Internal helpers
 
     def decompose_union_helper(
@@ -2367,13 +2542,37 @@ def translate_special_method_call(
         return primitive_op
 
     def translate_eq_cmp(self, lreg: Value, rreg: Value, expr_op: str, line: int) -> Value | None:
-        """Add a equality comparison operation.
+        """Add an equality comparison operation.
+
+        Note that this doesn't cover all possible types.
 
         Args:
             expr_op: either '==' or '!='
         """
         ltype = lreg.type
         rtype = rreg.type
+
+        if is_str_rprimitive(ltype) and is_str_rprimitive(rtype):
+            return self.compare_strings(lreg, rreg, expr_op, line)
+        if is_bytes_rprimitive(ltype) and is_bytes_rprimitive(rtype):
+            return self.compare_bytes(lreg, rreg, expr_op, line)
+
+        lopt = optional_value_type(ltype)
+        ropt = optional_value_type(rtype)
+
+        # Can we do a quick comparison of two optional types (special case None values)?
+        fast_opt_eq = False
+        if lopt is not None:
+            if ropt is not None and is_same_type(lopt, ropt) and self._never_equal_to_none(lopt):
+                fast_opt_eq = True
+            if is_same_type(lopt, rtype) and self._never_equal_to_none(lopt):
+                fast_opt_eq = True
+        elif ropt is not None:
+            if is_same_type(ropt, ltype) and self._never_equal_to_none(ropt):
+                fast_opt_eq = True
+        if fast_opt_eq:
+            return self._translate_fast_optional_eq_cmp(lreg, rreg, expr_op, line)
+
         if not (isinstance(ltype, RInstance) and ltype == rtype):
             return None
 
@@ -2400,6 +2599,76 @@ def translate_eq_cmp(self, lreg: Value, rreg: Value, expr_op: str, line: int) ->
 
         return self.gen_method_call(lreg, op_methods[expr_op], [rreg], ltype, line)
 
+    def _never_equal_to_none(self, typ: RType) -> bool:
+        """Are the values of type never equal to None?"""
+        # TODO: Support RInstance with no custom __eq__/__ne__ and other primitive types.
+        return is_str_rprimitive(typ) or is_bytes_rprimitive(typ)
+
+    def _translate_fast_optional_eq_cmp(
+        self, lreg: Value, rreg: Value, expr_op: str, line: int
+    ) -> Value:
+        """Generate eq/ne fast path between 'X | None' and ('X | None' or X).
+
+        Assume 'X' never compares equal to None.
+        """
+        if not isinstance(lreg.type, RUnion):
+            lreg, rreg = rreg, lreg
+        value_typ = optional_value_type(lreg.type)
+        assert value_typ
+        res = Register(bool_rprimitive)
+
+        # Fast path: left value is None?
+        cmp = self.add(ComparisonOp(lreg, self.none_object(), ComparisonOp.EQ, line))
+        l_none = BasicBlock()
+        l_not_none = BasicBlock()
+        out = BasicBlock()
+        self.add(Branch(cmp, l_none, l_not_none, Branch.BOOL))
+        self.activate_block(l_none)
+        if not isinstance(rreg.type, RUnion):
+            val = self.false() if expr_op == "==" else self.true()
+            self.add(Assign(res, val))
+        else:
+            op = ComparisonOp.EQ if expr_op == "==" else ComparisonOp.NEQ
+            cmp = self.add(ComparisonOp(rreg, self.none_object(), op, line))
+            self.add(Assign(res, cmp))
+        self.goto(out)
+
+        self.activate_block(l_not_none)
+        if not isinstance(rreg.type, RUnion):
+            # Both operands are known to be not None, perform specialized comparison
+            eq = self.translate_eq_cmp(
+                self.unbox_or_cast(lreg, value_typ, line, can_borrow=True, unchecked=True),
+                rreg,
+                expr_op,
+                line,
+            )
+            assert eq is not None
+            self.add(Assign(res, eq))
+        else:
+            r_none = BasicBlock()
+            r_not_none = BasicBlock()
+            # Fast path: right value is None?
+            cmp = self.add(ComparisonOp(rreg, self.none_object(), ComparisonOp.EQ, line))
+            self.add(Branch(cmp, r_none, r_not_none, Branch.BOOL))
+            self.activate_block(r_none)
+            # None vs not-None
+            val = self.false() if expr_op == "==" else self.true()
+            self.add(Assign(res, val))
+            self.goto(out)
+            self.activate_block(r_not_none)
+            # Both operands are known to be not None, perform specialized comparison
+            eq = self.translate_eq_cmp(
+                self.unbox_or_cast(lreg, value_typ, line, can_borrow=True, unchecked=True),
+                self.unbox_or_cast(rreg, value_typ, line, can_borrow=True, unchecked=True),
+                expr_op,
+                line,
+            )
+            assert eq is not None
+            self.add(Assign(res, eq))
+        self.goto(out)
+        self.activate_block(out)
+        return res
+
     def translate_is_op(self, lreg: Value, rreg: Value, expr_op: str, line: int) -> Value:
         """Create equality comparison operation between object identities
 
diff --git a/mypyc/irbuild/main.py b/mypyc/irbuild/main.py
index 7cdc6b686778..d2c8924a7298 100644
--- a/mypyc/irbuild/main.py
+++ b/mypyc/irbuild/main.py
@@ -25,7 +25,7 @@ def f(x: int) -> int:
 from typing import Any, Callable, TypeVar, cast
 
 from mypy.build import Graph
-from mypy.nodes import ClassDef, Expression, MypyFile
+from mypy.nodes import ClassDef, Expression, FuncDef, MypyFile
 from mypy.state import state
 from mypy.types import Type
 from mypyc.analysis.attrdefined import analyze_always_defined_attrs
@@ -37,7 +37,11 @@ def f(x: int) -> int:
 from mypyc.irbuild.builder import IRBuilder
 from mypyc.irbuild.mapper import Mapper
 from mypyc.irbuild.prebuildvisitor import PreBuildVisitor
-from mypyc.irbuild.prepare import build_type_map, find_singledispatch_register_impls
+from mypyc.irbuild.prepare import (
+    build_type_map,
+    create_generator_class_if_needed,
+    find_singledispatch_register_impls,
+)
 from mypyc.irbuild.visitor import IRBuilderVisitor
 from mypyc.irbuild.vtable import compute_vtable
 from mypyc.options import CompilerOptions
@@ -67,6 +71,8 @@ def build_ir(
     singledispatch_info = find_singledispatch_register_impls(modules, errors)
 
     result: ModuleIRs = {}
+    if errors.num_errors > 0:
+        return result
 
     # Generate IR for all modules.
     class_irs = []
@@ -76,6 +82,15 @@ def build_ir(
         pbv = PreBuildVisitor(errors, module, singledispatch_info.decorators_to_remove, types)
         module.accept(pbv)
 
+        # Declare generator classes for nested async functions and generators.
+        for fdef in pbv.nested_funcs:
+            if isinstance(fdef, FuncDef):
+                # Make generator class name sufficiently unique.
+                suffix = f"___{fdef.line}"
+                create_generator_class_if_needed(
+                    module.fullname, None, fdef, mapper, name_suffix=suffix
+                )
+
         # Construct and configure builder objects (cyclic runtime dependency).
         visitor = IRBuilderVisitor()
         builder = IRBuilder(
diff --git a/mypyc/irbuild/mapper.py b/mypyc/irbuild/mapper.py
index 7c6e03d0037c..05aa0e45c569 100644
--- a/mypyc/irbuild/mapper.py
+++ b/mypyc/irbuild/mapper.py
@@ -25,6 +25,7 @@
 from mypyc.ir.class_ir import ClassIR
 from mypyc.ir.func_ir import FuncDecl, FuncSignature, RuntimeArg
 from mypyc.ir.rtypes import (
+    KNOWN_NATIVE_TYPES,
     RInstance,
     RTuple,
     RType,
@@ -64,6 +65,8 @@ def __init__(self, group_map: dict[str, str | None]) -> None:
         self.type_to_ir: dict[TypeInfo, ClassIR] = {}
         self.func_to_decl: dict[SymbolNode, FuncDecl] = {}
         self.symbol_fullnames: set[str] = set()
+        # The corresponding generator class that implements a generator/async function
+        self.fdef_to_generator: dict[FuncDef, ClassIR] = {}
 
     def type_to_rtype(self, typ: Type | None) -> RType:
         if typ is None:
@@ -71,6 +74,10 @@ def type_to_rtype(self, typ: Type | None) -> RType:
 
         typ = get_proper_type(typ)
         if isinstance(typ, Instance):
+            if typ.type.is_newtype:
+                # Unwrap NewType to its base type for rprimitive mapping
+                assert len(typ.type.bases) == 1, typ.type.bases
+                return self.type_to_rtype(typ.type.bases[0])
             if typ.type.fullname == "builtins.int":
                 return int_rprimitive
             elif typ.type.fullname == "builtins.float":
@@ -113,6 +120,8 @@ def type_to_rtype(self, typ: Type | None) -> RType:
                 return int16_rprimitive
             elif typ.type.fullname == "mypy_extensions.u8":
                 return uint8_rprimitive
+            elif typ.type.fullname in KNOWN_NATIVE_TYPES:
+                return KNOWN_NATIVE_TYPES[typ.type.fullname]
             else:
                 return object_rprimitive
         elif isinstance(typ, TupleType):
@@ -171,7 +180,14 @@ def fdef_to_sig(self, fdef: FuncDef, strict_dunders_typing: bool) -> FuncSignatu
                 for typ, kind in zip(fdef.type.arg_types, fdef.type.arg_kinds)
             ]
             arg_pos_onlys = [name is None for name in fdef.type.arg_names]
-            ret = self.type_to_rtype(fdef.type.ret_type)
+            # TODO: We could probably support decorators sometimes (static and class method?)
+            if (fdef.is_coroutine or fdef.is_generator) and not fdef.is_decorated:
+                # Give a more precise type for generators, so that we can optimize
+                # code that uses them. They return a generator object, which has a
+                # specific class. Without this, the type would have to be 'object'.
+                ret: RType = RInstance(self.fdef_to_generator[fdef])
+            else:
+                ret = self.type_to_rtype(fdef.type.ret_type)
         else:
             # Handle unannotated functions
             arg_types = [object_rprimitive for _ in fdef.arguments]
diff --git a/mypyc/irbuild/match.py b/mypyc/irbuild/match.py
index d7bf9e0b94de..c2ca9cfd32ff 100644
--- a/mypyc/irbuild/match.py
+++ b/mypyc/irbuild/match.py
@@ -151,7 +151,7 @@ def visit_class_pattern(self, pattern: ClassPattern) -> None:
                 return
 
             node = pattern.class_ref.node
-            assert isinstance(node, TypeInfo)
+            assert isinstance(node, TypeInfo), node
             match_args = extract_dunder_match_args_names(node)
 
             for i, expr in enumerate(pattern.positionals):
@@ -345,7 +345,7 @@ def extract_dunder_match_args_names(info: TypeInfo) -> list[str]:
     ty = info.names.get("__match_args__")
     assert ty
     match_args_type = get_proper_type(ty.type)
-    assert isinstance(match_args_type, TupleType)
+    assert isinstance(match_args_type, TupleType), match_args_type
 
     match_args: list[str] = []
     for item in match_args_type.items:
diff --git a/mypyc/irbuild/nonlocalcontrol.py b/mypyc/irbuild/nonlocalcontrol.py
index 0ac9bd3cee31..4a7136fbd18d 100644
--- a/mypyc/irbuild/nonlocalcontrol.py
+++ b/mypyc/irbuild/nonlocalcontrol.py
@@ -16,9 +16,11 @@
     Integer,
     Register,
     Return,
+    SetMem,
     Unreachable,
     Value,
 )
+from mypyc.ir.rtypes import object_rprimitive
 from mypyc.irbuild.targets import AssignmentTarget
 from mypyc.primitives.exc_ops import restore_exc_info_op, set_stop_iteration_value
 
@@ -108,10 +110,27 @@ def gen_return(self, builder: IRBuilder, value: Value, line: int) -> None:
         # StopIteration instead of using RaiseStandardError because
         # the obvious thing doesn't work if the value is a tuple
         # (???).
+
+        true, false = BasicBlock(), BasicBlock()
+        stop_iter_reg = builder.fn_info.generator_class.stop_iter_value_reg
+        assert stop_iter_reg is not None
+
+        builder.add(Branch(stop_iter_reg, true, false, Branch.IS_ERROR))
+
+        builder.activate_block(true)
+        # The default/slow path is to raise a StopIteration exception with
+        # return value.
         builder.call_c(set_stop_iteration_value, [value], NO_TRACEBACK_LINE_NO)
         builder.add(Unreachable())
         builder.builder.pop_error_handler()
 
+        builder.activate_block(false)
+        # The fast path is to store return value via caller-provided pointer
+        # instead of raising an exception. This can only be used when the
+        # caller is a native function.
+        builder.add(SetMem(object_rprimitive, stop_iter_reg, value))
+        builder.add(Return(Integer(0, object_rprimitive)))
+
 
 class CleanupNonlocalControl(NonlocalControl):
     """Abstract nonlocal control that runs some cleanup code."""
@@ -156,7 +175,7 @@ def gen_return(self, builder: IRBuilder, value: Value, line: int) -> None:
                 self.ret_reg = Register(builder.ret_types[-1])
         # assert needed because of apparent mypy bug... it loses track of the union
         # and infers the type as object
-        assert isinstance(self.ret_reg, (Register, AssignmentTarget))
+        assert isinstance(self.ret_reg, (Register, AssignmentTarget)), self.ret_reg
         builder.assign(self.ret_reg, value, line)
 
         builder.add(Goto(self.target))
diff --git a/mypyc/irbuild/prepare.py b/mypyc/irbuild/prepare.py
index 65951999dcf9..95c8c448d642 100644
--- a/mypyc/irbuild/prepare.py
+++ b/mypyc/irbuild/prepare.py
@@ -15,7 +15,7 @@
 
 from collections import defaultdict
 from collections.abc import Iterable
-from typing import NamedTuple
+from typing import Final, NamedTuple
 
 from mypy.build import Graph
 from mypy.nodes import (
@@ -38,7 +38,7 @@
 from mypy.semanal import refers_to_fullname
 from mypy.traverser import TraverserVisitor
 from mypy.types import Instance, Type, get_proper_type
-from mypyc.common import PROPSET_PREFIX, get_id_from_name
+from mypyc.common import FAST_PREFIX, PROPSET_PREFIX, SELF_NAME, get_id_from_name
 from mypyc.crash import catch_errors
 from mypyc.errors import Errors
 from mypyc.ir.class_ir import ClassIR
@@ -51,7 +51,15 @@
     RuntimeArg,
 )
 from mypyc.ir.ops import DeserMaps
-from mypyc.ir.rtypes import RInstance, RType, dict_rprimitive, none_rprimitive, tuple_rprimitive
+from mypyc.ir.rtypes import (
+    RInstance,
+    RType,
+    dict_rprimitive,
+    none_rprimitive,
+    object_pointer_rprimitive,
+    object_rprimitive,
+    tuple_rprimitive,
+)
 from mypyc.irbuild.mapper import Mapper
 from mypyc.irbuild.util import (
     get_func_def,
@@ -63,6 +71,8 @@
 from mypyc.options import CompilerOptions
 from mypyc.sametype import is_same_type
 
+GENERATOR_HELPER_NAME: Final = "__mypyc_generator_helper__"
+
 
 def build_type_map(
     mapper: Mapper,
@@ -96,6 +106,7 @@ def build_type_map(
             class_ir.children = None
         mapper.type_to_ir[cdef.info] = class_ir
         mapper.symbol_fullnames.add(class_ir.fullname)
+        class_ir.is_enum = cdef.info.is_enum and len(cdef.info.enum_members) > 0
 
     # Populate structural information in class IR for extension classes.
     for module, cdef in classes:
@@ -115,7 +126,7 @@ def build_type_map(
 
     # Collect all the functions also. We collect from the symbol table
     # so that we can easily pick out the right copy of a function that
-    # is conditionally defined.
+    # is conditionally defined. This doesn't include nested functions!
     for module in modules:
         for func in get_module_func_defs(module):
             prepare_func_def(module.fullname, None, func, mapper, options)
@@ -179,10 +190,12 @@ def prepare_func_def(
     mapper: Mapper,
     options: CompilerOptions,
 ) -> FuncDecl:
+    create_generator_class_if_needed(module_name, class_name, fdef, mapper)
+
     kind = (
-        FUNC_STATICMETHOD
-        if fdef.is_static
-        else (FUNC_CLASSMETHOD if fdef.is_class else FUNC_NORMAL)
+        FUNC_CLASSMETHOD
+        if fdef.is_class
+        else (FUNC_STATICMETHOD if fdef.is_static else FUNC_NORMAL)
     )
     sig = mapper.fdef_to_sig(fdef, options.strict_dunders_typing)
     decl = FuncDecl(fdef.name, class_name, module_name, sig, kind)
@@ -190,6 +203,40 @@ def prepare_func_def(
     return decl
 
 
+def create_generator_class_if_needed(
+    module_name: str, class_name: str | None, fdef: FuncDef, mapper: Mapper, name_suffix: str = ""
+) -> None:
+    """If function is a generator/async function, declare a generator class.
+
+    Each generator and async function gets a dedicated class that implements the
+    generator protocol with generated methods.
+    """
+    if fdef.is_coroutine or fdef.is_generator:
+        name = "_".join(x for x in [fdef.name, class_name] if x) + "_gen" + name_suffix
+        cir = ClassIR(name, module_name, is_generated=True, is_final_class=True)
+        cir.reuse_freed_instance = True
+        mapper.fdef_to_generator[fdef] = cir
+
+        helper_sig = FuncSignature(
+            (
+                RuntimeArg(SELF_NAME, object_rprimitive),
+                RuntimeArg("type", object_rprimitive),
+                RuntimeArg("value", object_rprimitive),
+                RuntimeArg("traceback", object_rprimitive),
+                RuntimeArg("arg", object_rprimitive),
+                # If non-NULL, used to store return value instead of raising StopIteration(retv)
+                RuntimeArg("stop_iter_ptr", object_pointer_rprimitive),
+            ),
+            object_rprimitive,
+        )
+
+        # The implementation of most generator functionality is behind this magic method.
+        helper_fn_decl = FuncDecl(
+            GENERATOR_HELPER_NAME, name, module_name, helper_sig, internal=True
+        )
+        cir.method_decls[helper_fn_decl.name] = helper_fn_decl
+
+
 def prepare_method_def(
     ir: ClassIR,
     module_name: str,
@@ -224,6 +271,36 @@ def prepare_method_def(
             ir.property_types[node.name] = decl.sig.ret_type
 
 
+def prepare_fast_path(
+    ir: ClassIR,
+    module_name: str,
+    cdef: ClassDef,
+    mapper: Mapper,
+    node: SymbolNode | None,
+    options: CompilerOptions,
+) -> None:
+    """Add fast (direct) variants of methods in non-extension classes."""
+    if ir.is_enum:
+        # We check that non-empty enums are implicitly final in mypy, so we
+        # can generate direct calls to enum methods.
+        if isinstance(node, OverloadedFuncDef):
+            if node.is_property:
+                return
+            node = node.impl
+        if not isinstance(node, FuncDef):
+            # TODO: support decorated methods (at least @classmethod and @staticmethod).
+            return
+        # The simplest case is a regular or overloaded method without decorators. In this
+        # case we can generate practically identical IR method body, but with a signature
+        # suitable for direct calls (usual non-extension class methods are converted to
+        # callable classes, and thus have an extra __mypyc_self__ argument).
+        name = FAST_PREFIX + node.name
+        sig = mapper.fdef_to_sig(node, options.strict_dunders_typing)
+        decl = FuncDecl(name, cdef.name, module_name, sig, FUNC_NORMAL)
+        ir.method_decls[name] = decl
+    return
+
+
 def is_valid_multipart_property_def(prop: OverloadedFuncDef) -> bool:
     # Checks to ensure supported property decorator semantics
     if len(prop.items) != 2:
@@ -478,21 +555,57 @@ def add_setter_declaration(
     ir.method_decls[setter_name] = decl
 
 
+def check_matching_args(init_sig: FuncSignature, new_sig: FuncSignature) -> bool:
+    num_init_args = len(init_sig.args) - init_sig.num_bitmap_args
+    num_new_args = len(new_sig.args) - new_sig.num_bitmap_args
+    if num_init_args != num_new_args:
+        return False
+
+    for idx in range(1, num_init_args):
+        init_arg = init_sig.args[idx]
+        new_arg = new_sig.args[idx]
+        if init_arg.type != new_arg.type:
+            return False
+
+        if init_arg.kind != new_arg.kind:
+            return False
+
+    return True
+
+
 def prepare_init_method(cdef: ClassDef, ir: ClassIR, module_name: str, mapper: Mapper) -> None:
     # Set up a constructor decl
     init_node = cdef.info["__init__"].node
+
+    new_node: SymbolNode | None = None
+    new_symbol = cdef.info.get("__new__")
+    # We are only interested in __new__ method defined in a user-defined class,
+    # so we ignore it if it comes from a builtin type. It's usually builtins.object
+    # but could also be builtins.type for metaclasses so we detect the prefix which
+    # matches both.
+    if new_symbol and new_symbol.fullname and not new_symbol.fullname.startswith("builtins."):
+        new_node = new_symbol.node
+    if isinstance(new_node, (Decorator, OverloadedFuncDef)):
+        new_node = get_func_def(new_node)
     if not ir.is_trait and not ir.builtin_base and isinstance(init_node, FuncDef):
         init_sig = mapper.fdef_to_sig(init_node, True)
+        args_match = True
+        if isinstance(new_node, FuncDef):
+            new_sig = mapper.fdef_to_sig(new_node, True)
+            args_match = check_matching_args(init_sig, new_sig)
 
         defining_ir = mapper.type_to_ir.get(init_node.info)
         # If there is a nontrivial __init__ that wasn't defined in an
         # extension class, we need to make the constructor take *args,
         # **kwargs so it can call tp_init.
         if (
-            defining_ir is None
-            or not defining_ir.is_ext_class
-            or cdef.info["__init__"].plugin_generated
-        ) and init_node.info.fullname != "builtins.object":
+            (
+                defining_ir is None
+                or not defining_ir.is_ext_class
+                or cdef.info["__init__"].plugin_generated
+            )
+            and init_node.info.fullname != "builtins.object"
+        ) or not args_match:
             init_sig = FuncSignature(
                 [
                     init_sig.args[0],
@@ -533,6 +646,8 @@ def prepare_non_ext_class_def(
             else:
                 prepare_method_def(ir, module_name, cdef, mapper, get_func_def(node.node), options)
 
+        prepare_fast_path(ir, module_name, cdef, mapper, node.node, options)
+
     if any(cls in mapper.type_to_ir and mapper.type_to_ir[cls].is_ext_class for cls in info.mro):
         errors.error(
             "Non-extension classes may not inherit from extension classes", path, cdef.line
@@ -570,6 +685,12 @@ def __init__(self, errors: Errors) -> None:
         self.decorators_to_remove: dict[FuncDef, list[int]] = {}
 
         self.errors: Errors = errors
+        self.func_stack_depth = 0
+
+    def visit_func_def(self, o: FuncDef) -> None:
+        self.func_stack_depth += 1
+        super().visit_func_def(o)
+        self.func_stack_depth -= 1
 
     def visit_decorator(self, dec: Decorator) -> None:
         if dec.decorators:
@@ -581,6 +702,10 @@ def visit_decorator(self, dec: Decorator) -> None:
             for i, d in enumerate(decorators_to_store):
                 impl = get_singledispatch_register_call_info(d, dec.func)
                 if impl is not None:
+                    if self.func_stack_depth > 0:
+                        self.errors.error(
+                            "Registering nested functions not supported", self.current_path, d.line
+                        )
                     self.singledispatch_impls[impl.singledispatch_func].append(
                         (impl.dispatch_type, dec.func)
                     )
@@ -597,6 +722,12 @@ def visit_decorator(self, dec: Decorator) -> None:
                         )
                 else:
                     if refers_to_fullname(d, "functools.singledispatch"):
+                        if self.func_stack_depth > 0:
+                            self.errors.error(
+                                "Nested singledispatch functions not supported",
+                                self.current_path,
+                                d.line,
+                            )
                         decorators_to_remove.append(i)
                         # make sure that we still treat the function as a singledispatch function
                         # even if we don't find any registered implementations (which might happen
diff --git a/mypyc/irbuild/specialize.py b/mypyc/irbuild/specialize.py
index f652449f5289..576b7a7ebffd 100644
--- a/mypyc/irbuild/specialize.py
+++ b/mypyc/irbuild/specialize.py
@@ -14,7 +14,7 @@
 
 from __future__ import annotations
 
-from typing import Callable, Optional
+from typing import Callable, Final, Optional
 
 from mypy.nodes import (
     ARG_NAMED,
@@ -31,6 +31,7 @@
     RefExpr,
     StrExpr,
     TupleExpr,
+    Var,
 )
 from mypy.types import AnyType, TypeOfAny
 from mypyc.ir.ops import (
@@ -49,6 +50,7 @@
     RTuple,
     RType,
     bool_rprimitive,
+    bytes_rprimitive,
     c_int_rprimitive,
     dict_rprimitive,
     int16_rprimitive,
@@ -83,19 +85,29 @@
     join_formatted_strings,
     tokenizer_format_call,
 )
+from mypyc.primitives.bytes_ops import isinstance_bytearray, isinstance_bytes
 from mypyc.primitives.dict_ops import (
     dict_items_op,
     dict_keys_op,
     dict_setdefault_spec_init_op,
     dict_values_op,
+    isinstance_dict,
 )
-from mypyc.primitives.list_ops import new_list_set_item_op
+from mypyc.primitives.float_ops import isinstance_float
+from mypyc.primitives.int_ops import isinstance_int
+from mypyc.primitives.list_ops import isinstance_list, new_list_set_item_op
+from mypyc.primitives.misc_ops import isinstance_bool
+from mypyc.primitives.set_ops import isinstance_frozenset, isinstance_set
 from mypyc.primitives.str_ops import (
+    bytes_decode_ascii_strict,
+    bytes_decode_latin1_strict,
+    bytes_decode_utf8_strict,
+    isinstance_str,
     str_encode_ascii_strict,
     str_encode_latin1_strict,
     str_encode_utf8_strict,
 )
-from mypyc.primitives.tuple_ops import new_tuple_set_item_op
+from mypyc.primitives.tuple_ops import isinstance_tuple, new_tuple_set_item_op
 
 # Specializers are attempted before compiling the arguments to the
 # function.  Specializers can return None to indicate that they failed
@@ -281,7 +293,7 @@ def translate_tuple_from_generator_call(
     """Special case for simplest tuple creation from a generator.
 
     For example:
-        tuple(f(x) for x in some_list/some_tuple/some_str)
+        tuple(f(x) for x in some_list/some_tuple/some_str/some_bytes)
     'translate_safe_generator_call()' would take care of other cases
     if this fails.
     """
@@ -546,6 +558,21 @@ def gen_inner_stmts() -> None:
     return retval
 
 
+isinstance_primitives: Final = {
+    "builtins.bool": isinstance_bool,
+    "builtins.bytearray": isinstance_bytearray,
+    "builtins.bytes": isinstance_bytes,
+    "builtins.dict": isinstance_dict,
+    "builtins.float": isinstance_float,
+    "builtins.frozenset": isinstance_frozenset,
+    "builtins.int": isinstance_int,
+    "builtins.list": isinstance_list,
+    "builtins.set": isinstance_set,
+    "builtins.str": isinstance_str,
+    "builtins.tuple": isinstance_tuple,
+}
+
+
 @specialize_function("builtins.isinstance")
 def translate_isinstance(builder: IRBuilder, expr: CallExpr, callee: RefExpr) -> Value | None:
     """Special case for builtins.isinstance.
@@ -554,11 +581,10 @@ def translate_isinstance(builder: IRBuilder, expr: CallExpr, callee: RefExpr) ->
     there is no need to coerce something to a new type before checking
     what type it is, and the coercion could lead to bugs.
     """
-    if (
-        len(expr.args) == 2
-        and expr.arg_kinds == [ARG_POS, ARG_POS]
-        and isinstance(expr.args[1], (RefExpr, TupleExpr))
-    ):
+    if not (len(expr.args) == 2 and expr.arg_kinds == [ARG_POS, ARG_POS]):
+        return None
+
+    if isinstance(expr.args[1], (RefExpr, TupleExpr)):
         builder.types[expr.args[0]] = AnyType(TypeOfAny.from_error)
 
         irs = builder.flatten_classes(expr.args[1])
@@ -569,6 +595,15 @@ def translate_isinstance(builder: IRBuilder, expr: CallExpr, callee: RefExpr) ->
             )
             obj = builder.accept(expr.args[0], can_borrow=can_borrow)
             return builder.builder.isinstance_helper(obj, irs, expr.line)
+
+    if isinstance(expr.args[1], RefExpr):
+        node = expr.args[1].node
+        if node:
+            desc = isinstance_primitives.get(node.fullname)
+            if desc:
+                obj = builder.accept(expr.args[0])
+                return builder.primitive_op(desc, [obj], expr.line)
+
     return None
 
 
@@ -680,6 +715,24 @@ def translate_fstring(builder: IRBuilder, expr: CallExpr, callee: RefExpr) -> Va
                 format_ops.append(FormatOp.STR)
                 exprs.append(item.args[0])
 
+        def get_literal_str(expr: Expression) -> str | None:
+            if isinstance(expr, StrExpr):
+                return expr.value
+            elif isinstance(expr, RefExpr) and isinstance(expr.node, Var) and expr.node.is_final:
+                final_value = expr.node.final_value
+                if final_value is not None:
+                    return str(final_value)
+            return None
+
+        for i in range(len(exprs) - 1):
+            while (
+                len(exprs) >= i + 2
+                and (first := get_literal_str(exprs[i])) is not None
+                and (second := get_literal_str(exprs[i + 1])) is not None
+            ):
+                exprs = [*exprs[:i], StrExpr(first + second), *exprs[i + 2 :]]
+                format_ops = [*format_ops[:i], FormatOp.STR, *format_ops[i + 2 :]]
+
         substitutions = convert_format_expr_to_str(builder, format_ops, exprs, expr.line)
         if substitutions is None:
             return None
@@ -740,6 +793,67 @@ def str_encode_fast_path(builder: IRBuilder, expr: CallExpr, callee: RefExpr) ->
     return None
 
 
+@specialize_function("decode", bytes_rprimitive)
+def bytes_decode_fast_path(builder: IRBuilder, expr: CallExpr, callee: RefExpr) -> Value | None:
+    """Specialize common cases of obj.decode for most used encodings and strict errors."""
+
+    if not isinstance(callee, MemberExpr):
+        return None
+
+    # We can only specialize if we have string literals as args
+    if len(expr.arg_kinds) > 0 and not isinstance(expr.args[0], StrExpr):
+        return None
+    if len(expr.arg_kinds) > 1 and not isinstance(expr.args[1], StrExpr):
+        return None
+
+    encoding = "utf8"
+    errors = "strict"
+    if len(expr.arg_kinds) > 0 and isinstance(expr.args[0], StrExpr):
+        if expr.arg_kinds[0] == ARG_NAMED:
+            if expr.arg_names[0] == "encoding":
+                encoding = expr.args[0].value
+            elif expr.arg_names[0] == "errors":
+                errors = expr.args[0].value
+        elif expr.arg_kinds[0] == ARG_POS:
+            encoding = expr.args[0].value
+        else:
+            return None
+    if len(expr.arg_kinds) > 1 and isinstance(expr.args[1], StrExpr):
+        if expr.arg_kinds[1] == ARG_NAMED:
+            if expr.arg_names[1] == "encoding":
+                encoding = expr.args[1].value
+            elif expr.arg_names[1] == "errors":
+                errors = expr.args[1].value
+        elif expr.arg_kinds[1] == ARG_POS:
+            errors = expr.args[1].value
+        else:
+            return None
+
+    if errors != "strict":
+        # We can only specialize strict errors
+        return None
+
+    encoding = encoding.lower().replace("_", "-")  # normalize
+    # Specialized encodings and their accepted aliases
+    if encoding in ["u8", "utf", "utf8", "utf-8", "cp65001"]:
+        return builder.call_c(bytes_decode_utf8_strict, [builder.accept(callee.expr)], expr.line)
+    elif encoding in ["646", "ascii", "usascii", "us-ascii"]:
+        return builder.call_c(bytes_decode_ascii_strict, [builder.accept(callee.expr)], expr.line)
+    elif encoding in [
+        "iso8859-1",
+        "iso-8859-1",
+        "8859",
+        "cp819",
+        "latin",
+        "latin1",
+        "latin-1",
+        "l1",
+    ]:
+        return builder.call_c(bytes_decode_latin1_strict, [builder.accept(callee.expr)], expr.line)
+
+    return None
+
+
 @specialize_function("mypy_extensions.i64")
 def translate_i64(builder: IRBuilder, expr: CallExpr, callee: RefExpr) -> Value | None:
     if len(expr.args) != 1 or expr.arg_kinds[0] != ARG_POS:
diff --git a/mypyc/irbuild/statement.py b/mypyc/irbuild/statement.py
index 16a0483a8729..eeeb40ac672f 100644
--- a/mypyc/irbuild/statement.py
+++ b/mypyc/irbuild/statement.py
@@ -12,6 +12,7 @@
 from collections.abc import Sequence
 from typing import Callable
 
+import mypy.nodes
 from mypy.nodes import (
     ARG_NAMED,
     ARG_POS,
@@ -46,12 +47,15 @@
     YieldExpr,
     YieldFromExpr,
 )
+from mypyc.common import TEMP_ATTR_NAME
 from mypyc.ir.ops import (
+    ERR_NEVER,
     NAMESPACE_MODULE,
     NO_TRACEBACK_LINE_NO,
     Assign,
     BasicBlock,
     Branch,
+    Call,
     InitStatic,
     Integer,
     LoadAddress,
@@ -87,6 +91,7 @@
     FinallyNonlocalControl,
     TryFinallyNonlocalControl,
 )
+from mypyc.irbuild.prepare import GENERATOR_HELPER_NAME
 from mypyc.irbuild.targets import (
     AssignmentTarget,
     AssignmentTargetAttr,
@@ -100,6 +105,8 @@
     get_exc_info_op,
     get_exc_value_op,
     keep_propagating_op,
+    no_err_occurred_op,
+    propagate_if_error_op,
     raise_exception_op,
     reraise_exception_op,
     restore_exc_info_op,
@@ -653,10 +660,15 @@ def try_finally_resolve_control(
     if ret_reg:
         builder.activate_block(rest)
         return_block, rest = BasicBlock(), BasicBlock()
-        builder.add(Branch(builder.read(ret_reg), rest, return_block, Branch.IS_ERROR))
+        # For spill targets in try/finally, use nullable read to avoid AttributeError
+        if isinstance(ret_reg, AssignmentTargetAttr) and ret_reg.attr.startswith(TEMP_ATTR_NAME):
+            ret_val = builder.read_nullable_attr(ret_reg.obj, ret_reg.attr, -1)
+        else:
+            ret_val = builder.read(ret_reg)
+        builder.add(Branch(ret_val, rest, return_block, Branch.IS_ERROR))
 
         builder.activate_block(return_block)
-        builder.nonlocal_control[-1].gen_return(builder, builder.read(ret_reg), -1)
+        builder.nonlocal_control[-1].gen_return(builder, ret_val, -1)
 
     # TODO: handle break/continue
     builder.activate_block(rest)
@@ -673,7 +685,7 @@ def try_finally_resolve_control(
 
 
 def transform_try_finally_stmt(
-    builder: IRBuilder, try_body: GenFunc, finally_body: GenFunc
+    builder: IRBuilder, try_body: GenFunc, finally_body: GenFunc, line: int = -1
 ) -> None:
     """Generalized try/finally handling that takes functions to gen the bodies.
 
@@ -709,6 +721,118 @@ def transform_try_finally_stmt(
     builder.activate_block(out_block)
 
 
+def transform_try_finally_stmt_async(
+    builder: IRBuilder, try_body: GenFunc, finally_body: GenFunc, line: int = -1
+) -> None:
+    """Async-aware try/finally handling for when finally contains await.
+
+    This version uses a modified approach that preserves exceptions across await."""
+
+    # We need to handle returns properly, so we'll use TryFinallyNonlocalControl
+    # to track return values, similar to the regular try/finally implementation
+
+    err_handler, main_entry, return_entry, finally_entry = (
+        BasicBlock(),
+        BasicBlock(),
+        BasicBlock(),
+        BasicBlock(),
+    )
+
+    # Track if we're returning from the try block
+    control = TryFinallyNonlocalControl(return_entry)
+    builder.builder.push_error_handler(err_handler)
+    builder.nonlocal_control.append(control)
+    builder.goto_and_activate(BasicBlock())
+    try_body()
+    builder.goto(main_entry)
+    builder.nonlocal_control.pop()
+    builder.builder.pop_error_handler()
+    ret_reg = control.ret_reg
+
+    # Normal case - no exception or return
+    builder.activate_block(main_entry)
+    builder.goto(finally_entry)
+
+    # Return case
+    builder.activate_block(return_entry)
+    builder.goto(finally_entry)
+
+    # Exception case - need to catch to clear the error indicator
+    builder.activate_block(err_handler)
+    # Catch the error to clear Python's error indicator
+    builder.call_c(error_catch_op, [], line)
+    # We're not going to use old_exc since it won't survive await
+    # The exception is now in sys.exc_info()
+    builder.goto(finally_entry)
+
+    # Finally block
+    builder.activate_block(finally_entry)
+
+    # Execute finally body
+    finally_body()
+
+    # After finally, we need to handle exceptions carefully:
+    # 1. If finally raised a new exception, it's in the error indicator - let it propagate
+    # 2. If finally didn't raise, check if we need to reraise the original from sys.exc_info()
+    # 3. If there was a return, return that value
+    # 4. Otherwise, normal exit
+
+    # First, check if there's a current exception in the error indicator
+    # (this would be from the finally block)
+    no_current_exc = builder.call_c(no_err_occurred_op, [], line)
+    finally_raised = BasicBlock()
+    check_original = BasicBlock()
+    builder.add(Branch(no_current_exc, check_original, finally_raised, Branch.BOOL))
+
+    # Finally raised an exception - let it propagate naturally
+    builder.activate_block(finally_raised)
+    builder.call_c(keep_propagating_op, [], NO_TRACEBACK_LINE_NO)
+    builder.add(Unreachable())
+
+    # No exception from finally, check if we need to handle return or original exception
+    builder.activate_block(check_original)
+
+    # Check if we have a return value
+    if ret_reg:
+        return_block, check_old_exc = BasicBlock(), BasicBlock()
+        builder.add(Branch(builder.read(ret_reg), check_old_exc, return_block, Branch.IS_ERROR))
+
+        builder.activate_block(return_block)
+        builder.nonlocal_control[-1].gen_return(builder, builder.read(ret_reg), -1)
+
+        builder.activate_block(check_old_exc)
+
+    # Check if we need to reraise the original exception from sys.exc_info
+    exc_info = builder.call_c(get_exc_info_op, [], line)
+    exc_type = builder.add(TupleGet(exc_info, 0, line))
+
+    # Check if exc_type is None
+    none_obj = builder.none_object()
+    has_exc = builder.binary_op(exc_type, none_obj, "is not", line)
+
+    reraise_block, exit_block = BasicBlock(), BasicBlock()
+    builder.add(Branch(has_exc, reraise_block, exit_block, Branch.BOOL))
+
+    # Reraise the original exception
+    builder.activate_block(reraise_block)
+    builder.call_c(reraise_exception_op, [], NO_TRACEBACK_LINE_NO)
+    builder.add(Unreachable())
+
+    # Normal exit
+    builder.activate_block(exit_block)
+
+
+# A simple visitor to detect await expressions
+class AwaitDetector(mypy.traverser.TraverserVisitor):
+    def __init__(self) -> None:
+        super().__init__()
+        self.has_await = False
+
+    def visit_await_expr(self, o: mypy.nodes.AwaitExpr) -> None:
+        self.has_await = True
+        super().visit_await_expr(o)
+
+
 def transform_try_stmt(builder: IRBuilder, t: TryStmt) -> None:
     # Our compilation strategy for try/except/else/finally is to
     # treat try/except/else and try/finally as separate language
@@ -717,6 +841,17 @@ def transform_try_stmt(builder: IRBuilder, t: TryStmt) -> None:
     # body of a try/finally block.
     if t.is_star:
         builder.error("Exception groups and except* cannot be compiled yet", t.line)
+
+    # Check if we're in an async function with a finally block that contains await
+    use_async_version = False
+    if t.finally_body and builder.fn_info.is_coroutine:
+        detector = AwaitDetector()
+        t.finally_body.accept(detector)
+
+        if detector.has_await:
+            # Use the async version that handles exceptions correctly
+            use_async_version = True
+
     if t.finally_body:
 
         def transform_try_body() -> None:
@@ -727,7 +862,14 @@ def transform_try_body() -> None:
 
         body = t.finally_body
 
-        transform_try_finally_stmt(builder, transform_try_body, lambda: builder.accept(body))
+        if use_async_version:
+            transform_try_finally_stmt_async(
+                builder, transform_try_body, lambda: builder.accept(body), t.line
+            )
+        else:
+            transform_try_finally_stmt(
+                builder, transform_try_body, lambda: builder.accept(body), t.line
+            )
     else:
         transform_try_except_stmt(builder, t)
 
@@ -775,7 +917,7 @@ def maybe_natively_call_exit(exc_info: bool) -> Value:
             args = [none, none, none]
 
         if is_native:
-            assert isinstance(mgr_v.type, RInstance)
+            assert isinstance(mgr_v.type, RInstance), mgr_v.type
             exit_val = builder.gen_method_call(
                 builder.read(mgr),
                 f"__{al}exit__",
@@ -818,6 +960,7 @@ def finally_body() -> None:
         builder,
         lambda: transform_try_except(builder, try_body, [(None, None, except_body)], None, line),
         finally_body,
+        line,
     )
 
 
@@ -924,25 +1067,63 @@ def emit_yield_from_or_await(
     to_yield_reg = Register(object_rprimitive)
     received_reg = Register(object_rprimitive)
 
-    get_op = coro_op if is_await else iter_op
-    if isinstance(get_op, PrimitiveDescription):
-        iter_val = builder.primitive_op(get_op, [val], line)
+    helper_method = GENERATOR_HELPER_NAME
+    if (
+        isinstance(val, (Call, MethodCall))
+        and isinstance(val.type, RInstance)
+        and val.type.class_ir.has_method(helper_method)
+    ):
+        # This is a generated native generator class, and we can use a fast path.
+        # This allows two optimizations:
+        # 1) No need to call CPy_GetCoro() or iter() since for native generators
+        #    it just returns the generator object (implemented here).
+        # 2) Instead of calling next(), call generator helper method directly,
+        #    since next() just calls __next__ which calls the helper method.
+        iter_val: Value = val
     else:
-        iter_val = builder.call_c(get_op, [val], line)
+        get_op = coro_op if is_await else iter_op
+        if isinstance(get_op, PrimitiveDescription):
+            iter_val = builder.primitive_op(get_op, [val], line)
+        else:
+            iter_val = builder.call_c(get_op, [val], line)
 
     iter_reg = builder.maybe_spill_assignable(iter_val)
 
     stop_block, main_block, done_block = BasicBlock(), BasicBlock(), BasicBlock()
-    _y_init = builder.call_c(next_raw_op, [builder.read(iter_reg)], line)
+
+    if isinstance(iter_reg.type, RInstance) and iter_reg.type.class_ir.has_method(helper_method):
+        # Second fast path optimization: call helper directly (see also comment above).
+        #
+        # Calling a generated generator, so avoid raising StopIteration by passing
+        # an extra PyObject ** argument to helper where the stop iteration value is stored.
+        fast_path = True
+        obj = builder.read(iter_reg)
+        nn = builder.none_object()
+        stop_iter_val = Register(object_rprimitive)
+        err = builder.add(LoadErrorValue(object_rprimitive, undefines=True))
+        builder.assign(stop_iter_val, err, line)
+        ptr = builder.add(LoadAddress(object_pointer_rprimitive, stop_iter_val))
+        m = MethodCall(obj, helper_method, [nn, nn, nn, nn, ptr], line)
+        # Generators have custom error handling, so disable normal error handling.
+        m.error_kind = ERR_NEVER
+        _y_init = builder.add(m)
+    else:
+        fast_path = False
+        _y_init = builder.call_c(next_raw_op, [builder.read(iter_reg)], line)
+
     builder.add(Branch(_y_init, stop_block, main_block, Branch.IS_ERROR))
 
-    # Try extracting a return value from a StopIteration and return it.
-    # If it wasn't, this reraises the exception.
     builder.activate_block(stop_block)
-    builder.assign(result, builder.call_c(check_stop_op, [], line), line)
+    if fast_path:
+        builder.primitive_op(propagate_if_error_op, [stop_iter_val], line)
+        builder.assign(result, stop_iter_val, line)
+    else:
+        # Try extracting a return value from a StopIteration and return it.
+        # If it wasn't, this reraises the exception.
+        builder.assign(result, builder.call_c(check_stop_op, [], line), line)
     # Clear the spilled iterator/coroutine so that it will be freed.
     # Otherwise, the freeing of the spilled register would likely be delayed.
-    err = builder.add(LoadErrorValue(object_rprimitive))
+    err = builder.add(LoadErrorValue(iter_reg.type))
     builder.assign(iter_reg, err, line)
     builder.goto(done_block)
 
diff --git a/mypyc/lib-rt/CPy.h b/mypyc/lib-rt/CPy.h
index 1f0cf4dd63d6..5dec7509ac7b 100644
--- a/mypyc/lib-rt/CPy.h
+++ b/mypyc/lib-rt/CPy.h
@@ -64,6 +64,15 @@ typedef struct tuple_T4CIOO {
 } tuple_T4CIOO;
 #endif
 
+// System-wide empty tuple constant
+extern PyObject * __mypyc_empty_tuple__;
+
+static inline PyObject *CPyTuple_LoadEmptyTupleConstant(void) {
+#if !CPY_3_12_FEATURES
+    Py_INCREF(__mypyc_empty_tuple__);
+#endif
+    return __mypyc_empty_tuple__;
+}
 
 // Native object operations
 
@@ -646,14 +655,13 @@ PyObject *CPyObject_GetSlice(PyObject *obj, CPyTagged start, CPyTagged end);
 
 PyObject *CPyList_Build(Py_ssize_t len, ...);
 PyObject *CPyList_GetItem(PyObject *list, CPyTagged index);
-PyObject *CPyList_GetItemUnsafe(PyObject *list, CPyTagged index);
 PyObject *CPyList_GetItemShort(PyObject *list, CPyTagged index);
 PyObject *CPyList_GetItemBorrow(PyObject *list, CPyTagged index);
 PyObject *CPyList_GetItemShortBorrow(PyObject *list, CPyTagged index);
 PyObject *CPyList_GetItemInt64(PyObject *list, int64_t index);
 PyObject *CPyList_GetItemInt64Borrow(PyObject *list, int64_t index);
 bool CPyList_SetItem(PyObject *list, CPyTagged index, PyObject *value);
-bool CPyList_SetItemUnsafe(PyObject *list, CPyTagged index, PyObject *value);
+void CPyList_SetItemUnsafe(PyObject *list, Py_ssize_t index, PyObject *value);
 bool CPyList_SetItemInt64(PyObject *list, int64_t index, PyObject *value);
 PyObject *CPyList_PopLast(PyObject *obj);
 PyObject *CPyList_Pop(PyObject *obj, CPyTagged index);
@@ -667,6 +675,7 @@ PyObject *CPySequence_Multiply(PyObject *seq, CPyTagged t_size);
 PyObject *CPySequence_RMultiply(CPyTagged t_size, PyObject *seq);
 PyObject *CPySequence_InPlaceMultiply(PyObject *seq, CPyTagged t_size);
 PyObject *CPyList_GetSlice(PyObject *obj, CPyTagged start, CPyTagged end);
+char CPyList_Clear(PyObject *list);
 PyObject *CPyList_Copy(PyObject *list);
 int CPySequence_Check(PyObject *obj);
 
@@ -703,14 +712,13 @@ tuple_T4CIOO CPyDict_NextItem(PyObject *dict_or_iter, CPyTagged offset);
 int CPyMapping_Check(PyObject *obj);
 
 // Check that dictionary didn't change size during iteration.
-static inline char CPyDict_CheckSize(PyObject *dict, CPyTagged size) {
+static inline char CPyDict_CheckSize(PyObject *dict, Py_ssize_t size) {
     if (!PyDict_CheckExact(dict)) {
         // Dict subclasses will be checked by Python runtime.
         return 1;
     }
-    Py_ssize_t py_size = CPyTagged_AsSsize_t(size);
     Py_ssize_t dict_size = PyDict_Size(dict);
-    if (py_size != dict_size) {
+    if (size != dict_size) {
         PyErr_SetString(PyExc_RuntimeError, "dictionary changed size during iteration");
         return 0;
     }
@@ -725,8 +733,10 @@ static inline char CPyDict_CheckSize(PyObject *dict, CPyTagged size) {
 #define RIGHTSTRIP 1
 #define BOTHSTRIP  2
 
+char CPyStr_Equal(PyObject *str1, PyObject *str2);
 PyObject *CPyStr_Build(Py_ssize_t len, ...);
 PyObject *CPyStr_GetItem(PyObject *str, CPyTagged index);
+PyObject *CPyStr_GetItemUnsafe(PyObject *str, Py_ssize_t index);
 CPyTagged CPyStr_Find(PyObject *str, PyObject *substr, CPyTagged start, int direction);
 CPyTagged CPyStr_FindWithEnd(PyObject *str, PyObject *substr, CPyTagged start, CPyTagged end, int direction);
 PyObject *CPyStr_Split(PyObject *str, PyObject *sep, CPyTagged max_split);
@@ -751,7 +761,12 @@ PyObject *CPyStr_Removesuffix(PyObject *self, PyObject *suffix);
 bool CPyStr_IsTrue(PyObject *obj);
 Py_ssize_t CPyStr_Size_size_t(PyObject *str);
 PyObject *CPy_Decode(PyObject *obj, PyObject *encoding, PyObject *errors);
+PyObject *CPy_DecodeUTF8(PyObject *bytes);
+PyObject *CPy_DecodeASCII(PyObject *bytes);
+PyObject *CPy_DecodeLatin1(PyObject *bytes);
 PyObject *CPy_Encode(PyObject *obj, PyObject *encoding, PyObject *errors);
+Py_ssize_t CPyStr_Count(PyObject *unicode, PyObject *substring, CPyTagged start);
+Py_ssize_t CPyStr_CountFull(PyObject *unicode, PyObject *substring, CPyTagged start, CPyTagged end);
 CPyTagged CPyStr_Ord(PyObject *obj);
 
 
@@ -780,7 +795,8 @@ bool CPySet_Remove(PyObject *set, PyObject *key);
 
 PyObject *CPySequenceTuple_GetItem(PyObject *tuple, CPyTagged index);
 PyObject *CPySequenceTuple_GetSlice(PyObject *obj, CPyTagged start, CPyTagged end);
-bool CPySequenceTuple_SetItemUnsafe(PyObject *tuple, CPyTagged index, PyObject *value);
+PyObject *CPySequenceTuple_GetItemUnsafe(PyObject *tuple, Py_ssize_t index);
+void CPySequenceTuple_SetItemUnsafe(PyObject *tuple, Py_ssize_t index, PyObject *value);
 
 
 // Exception operations
@@ -870,6 +886,12 @@ static inline bool CPy_TypeCheck(PyObject *o, PyObject *type) {
     return PyObject_TypeCheck(o, (PyTypeObject *)type);
 }
 
+static inline PyObject *CPy_TYPE(PyObject *obj) {
+    PyObject *result = (PyObject *)Py_TYPE(obj);
+    Py_INCREF(result);
+    return result;
+}
+
 PyObject *CPy_CalculateMetaclass(PyObject *type, PyObject *o);
 PyObject *CPy_GetCoro(PyObject *obj);
 PyObject *CPyIter_Send(PyObject *iter, PyObject *val);
@@ -925,6 +947,15 @@ PyObject *CPySingledispatch_RegisterFunction(PyObject *singledispatch_func, PyOb
 PyObject *CPy_GetAIter(PyObject *obj);
 PyObject *CPy_GetANext(PyObject *aiter);
 void CPy_SetTypeAliasTypeComputeFunction(PyObject *alias, PyObject *compute_value);
+void CPyTrace_LogEvent(const char *location, const char *line, const char *op, const char *details);
+
+#if CPY_3_11_FEATURES
+PyObject *CPy_GetName(PyObject *obj);
+#endif
+
+#if CPY_3_14_FEATURES
+void CPy_SetImmortal(PyObject *obj);
+#endif
 
 #ifdef __cplusplus
 }
diff --git a/mypyc/lib-rt/init.c b/mypyc/lib-rt/init.c
index 01b133233489..9215c2d59019 100644
--- a/mypyc/lib-rt/init.c
+++ b/mypyc/lib-rt/init.c
@@ -4,10 +4,21 @@
 struct ExcDummyStruct _CPy_ExcDummyStruct = { PyObject_HEAD_INIT(NULL) };
 PyObject *_CPy_ExcDummy = (PyObject *)&_CPy_ExcDummyStruct;
 
+// System-wide empty tuple constant
+PyObject * __mypyc_empty_tuple__ = NULL;
+
 // Because its dynamic linker is more restricted than linux/OS X,
 // Windows doesn't allow initializing globals with values from
 // other dynamic libraries. This means we need to initialize
 // things at load time.
 void CPy_Init(void) {
     _CPy_ExcDummyStruct.ob_base.ob_type = &PyBaseObject_Type;
+
+    // Initialize system-wide empty tuple constant
+    if (__mypyc_empty_tuple__ == NULL) {
+        __mypyc_empty_tuple__ = PyTuple_New(0);
+        if (!__mypyc_empty_tuple__) {
+            CPyError_OutOfMemory();
+        }
+    }
 }
diff --git a/mypyc/lib-rt/list_ops.c b/mypyc/lib-rt/list_ops.c
index 4dddb2249f06..c611907fb601 100644
--- a/mypyc/lib-rt/list_ops.c
+++ b/mypyc/lib-rt/list_ops.c
@@ -29,6 +29,23 @@ PyObject *CPyList_Build(Py_ssize_t len, ...) {
     return res;
 }
 
+char CPyList_Clear(PyObject *list) {
+    if (PyList_CheckExact(list)) {
+        PyList_Clear(list);
+    } else {
+        _Py_IDENTIFIER(clear);
+        PyObject *name = _PyUnicode_FromId(&PyId_clear);
+        if (name == NULL) {
+            return 0;
+        }
+        PyObject *res = PyObject_CallMethodNoArgs(list, name);
+        if (res == NULL) {
+            return 0;
+        }
+    }
+    return 1;
+}
+
 PyObject *CPyList_Copy(PyObject *list) {
     if(PyList_CheckExact(list)) {
         return PyList_GetSlice(list, 0, PyList_GET_SIZE(list));
@@ -42,14 +59,6 @@ PyObject *CPyList_Copy(PyObject *list) {
     return PyObject_CallMethodNoArgs(list, name);
 }
 
-
-PyObject *CPyList_GetItemUnsafe(PyObject *list, CPyTagged index) {
-    Py_ssize_t n = CPyTagged_ShortAsSsize_t(index);
-    PyObject *result = PyList_GET_ITEM(list, n);
-    Py_INCREF(result);
-    return result;
-}
-
 PyObject *CPyList_GetItemShort(PyObject *list, CPyTagged index) {
     Py_ssize_t n = CPyTagged_ShortAsSsize_t(index);
     Py_ssize_t size = PyList_GET_SIZE(list);
@@ -222,30 +231,55 @@ bool CPyList_SetItemInt64(PyObject *list, int64_t index, PyObject *value) {
 }
 
 // This function should only be used to fill in brand new lists.
-bool CPyList_SetItemUnsafe(PyObject *list, CPyTagged index, PyObject *value) {
-    if (CPyTagged_CheckShort(index)) {
-        Py_ssize_t n = CPyTagged_ShortAsSsize_t(index);
-        PyList_SET_ITEM(list, n, value);
-        return true;
-    } else {
-        PyErr_SetString(PyExc_OverflowError, CPYTHON_LARGE_INT_ERRMSG);
-        return false;
+void CPyList_SetItemUnsafe(PyObject *list, Py_ssize_t index, PyObject *value) {
+    PyList_SET_ITEM(list, index, value);
+}
+
+#ifdef Py_GIL_DISABLED
+// The original optimized list.pop implementation doesn't work on free-threaded
+// builds, so provide an alternative that is a bit slower but works.
+//
+// Note that this implementation isn't intended to be atomic.
+static inline PyObject *list_pop_index(PyObject *list, Py_ssize_t index) {
+    PyObject *item = PyList_GetItemRef(list, index);
+    if (item == NULL) {
+        return NULL;
     }
+    if (PySequence_DelItem(list, index) < 0) {
+        Py_DECREF(item);
+        return NULL;
+    }
+    return item;
 }
+#endif
 
-PyObject *CPyList_PopLast(PyObject *obj)
+PyObject *CPyList_PopLast(PyObject *list)
 {
+#ifdef Py_GIL_DISABLED
+    // The other implementation causes segfaults on a free-threaded Python 3.14b4 build.
+    Py_ssize_t index = PyList_GET_SIZE(list) - 1;
+    return list_pop_index(list, index);
+#else
     // I tried a specalized version of pop_impl for just removing the
     // last element and it wasn't any faster in microbenchmarks than
     // the generic one so I ditched it.
-    return list_pop_impl((PyListObject *)obj, -1);
+    return list_pop_impl((PyListObject *)list, -1);
+#endif
 }
 
 PyObject *CPyList_Pop(PyObject *obj, CPyTagged index)
 {
     if (CPyTagged_CheckShort(index)) {
         Py_ssize_t n = CPyTagged_ShortAsSsize_t(index);
+#ifdef Py_GIL_DISABLED
+        // We must use a slower implementation on free-threaded builds.
+        if (n < 0) {
+            n += PyList_GET_SIZE(obj);
+        }
+        return list_pop_index(obj, n);
+#else
         return list_pop_impl((PyListObject *)obj, n);
+#endif
     } else {
         PyErr_SetString(PyExc_OverflowError, CPYTHON_LARGE_INT_ERRMSG);
         return NULL;
diff --git a/mypyc/lib-rt/misc_ops.c b/mypyc/lib-rt/misc_ops.c
index d234138b2ff7..ca09c347b4ff 100644
--- a/mypyc/lib-rt/misc_ops.c
+++ b/mypyc/lib-rt/misc_ops.c
@@ -227,6 +227,17 @@ PyObject *CPyType_FromTemplate(PyObject *template,
     if (!name)
         goto error;
 
+    if (template_->tp_doc) {
+        // cpython expects tp_doc to be heap-allocated so convert it here to
+        // avoid segfaults on deallocation.
+        Py_ssize_t size = strlen(template_->tp_doc) + 1;
+        char *doc = (char *)PyMem_Malloc(size);
+        if (!doc)
+            goto error;
+        memcpy(doc, template_->tp_doc, size);
+        template_->tp_doc = doc;
+    }
+
     // Allocate the type and then copy the main stuff in.
     t = (PyHeapTypeObject*)PyType_GenericAlloc(&PyType_Type, 0);
     if (!t)
@@ -300,6 +311,21 @@ PyObject *CPyType_FromTemplate(PyObject *template,
 
     Py_XDECREF(dummy_class);
 
+    // Unlike the tp_doc slots of most other object, a heap type's tp_doc
+    // must be heap allocated.
+    if (template_->tp_doc) {
+        // Silently truncate the docstring if it contains a null byte
+        Py_ssize_t size = strlen(template_->tp_doc) + 1;
+        char *tp_doc = (char *)PyMem_Malloc(size);
+        if (tp_doc == NULL) {
+            PyErr_NoMemory();
+            goto error;
+        }
+
+        memcpy(tp_doc, template_->tp_doc, size);
+        t->ht_type.tp_doc = tp_doc;
+    }
+
 #if PY_MINOR_VERSION == 11
     // This is a hack. Python 3.11 doesn't include good public APIs to work with managed
     // dicts, which are the default for heap types. So we try to opt-out until Python 3.12.
@@ -1030,7 +1056,49 @@ PyObject *CPy_GetANext(PyObject *aiter)
     return NULL;
 }
 
-#ifdef CPY_3_12_FEATURES
+#if CPY_3_11_FEATURES
+
+// Return obj.__name__ (specialized to type objects, which are the most common target).
+PyObject *CPy_GetName(PyObject *obj) {
+    if (PyType_Check(obj)) {
+        return PyType_GetName((PyTypeObject *)obj);
+    }
+    _Py_IDENTIFIER(__name__);
+    PyObject *name = _PyUnicode_FromId(&PyId___name__); /* borrowed */
+    return PyObject_GetAttr(obj, name);
+}
+
+#endif
+
+#ifdef MYPYC_LOG_TRACE
+
+// This is only compiled in if trace logging is enabled by user
+
+static int TraceCounter = 0;
+static const int TRACE_EVERY_NTH = 1009;  // Should be a prime number
+#define TRACE_LOG_FILE_NAME "mypyc_trace.txt"
+static FILE *TraceLogFile = NULL;
+
+// Log a tracing event on every Nth call
+void CPyTrace_LogEvent(const char *location, const char *line, const char *op, const char *details) {
+    if (TraceLogFile == NULL) {
+        if ((TraceLogFile = fopen(TRACE_LOG_FILE_NAME, "w")) == NULL) {
+            fprintf(stderr, "error: Could not open trace file %s\n", TRACE_LOG_FILE_NAME);
+            abort();
+        }
+    }
+    if (TraceCounter == 0) {
+        fprintf(TraceLogFile, "%s:%s:%s:%s\n", location, line, op, details);
+    }
+    TraceCounter++;
+    if (TraceCounter == TRACE_EVERY_NTH) {
+        TraceCounter = 0;
+    }
+}
+
+#endif
+
+#if CPY_3_12_FEATURES
 
 // Copied from Python 3.12.3, since this struct is internal to CPython. It defines
 // the structure of typing.TypeAliasType objects. We need it since compute_value is
@@ -1060,3 +1128,13 @@ void CPy_SetTypeAliasTypeComputeFunction(PyObject *alias, PyObject *compute_valu
 }
 
 #endif
+
+#if CPY_3_14_FEATURES
+
+#include "internal/pycore_object.h"
+
+void CPy_SetImmortal(PyObject *obj) {
+    _Py_SetImmortal(obj);
+}
+
+#endif
diff --git a/mypyc/lib-rt/module_shim_no_gil_multiphase.tmpl b/mypyc/lib-rt/module_shim_no_gil_multiphase.tmpl
new file mode 100644
index 000000000000..b9bfe9c91962
--- /dev/null
+++ b/mypyc/lib-rt/module_shim_no_gil_multiphase.tmpl
@@ -0,0 +1,41 @@
+#include <Python.h>
+
+static int {modname}_exec(PyObject *module)
+{{
+    PyObject *tmp;
+    if (!(tmp = PyImport_ImportModule("{libname}"))) return -1;
+    PyObject *capsule = PyObject_GetAttrString(tmp, "exec_{full_modname}");
+    Py_DECREF(tmp);
+    if (capsule == NULL) return -1;
+    void *exec_func = PyCapsule_GetPointer(capsule, "{libname}.exec_{full_modname}");
+    Py_DECREF(capsule);
+    if (!exec_func) return -1;
+    if (((int (*)(PyObject *))exec_func)(module) != 0) return -1;
+    return 0;
+}}
+
+static PyModuleDef_Slot {modname}_slots[] = {{
+    {{Py_mod_exec, {modname}_exec}},
+    {{Py_mod_multiple_interpreters, Py_MOD_MULTIPLE_INTERPRETERS_NOT_SUPPORTED}},
+    {{Py_mod_gil, Py_MOD_GIL_NOT_USED}},
+    {{0, NULL}},
+}};
+
+static struct PyModuleDef {modname}_module = {{
+    PyModuleDef_HEAD_INIT,
+    .m_name = "{modname}",
+    .m_doc = NULL,
+    .m_methods = NULL,
+    .m_size = 0,
+    .m_slots = {modname}_slots,
+}};
+
+PyMODINIT_FUNC
+PyInit_{modname}(void)
+{{
+    return PyModuleDef_Init(&{modname}_module);
+}}
+
+// distutils sometimes spuriously tells cl to export CPyInit___init__,
+// so provide that so it chills out
+PyMODINIT_FUNC PyInit___init__(void) {{ return PyInit_{modname}(); }}
diff --git a/mypyc/lib-rt/mypyc_util.h b/mypyc/lib-rt/mypyc_util.h
index 27a11ab9f581..4168d3c53ee2 100644
--- a/mypyc/lib-rt/mypyc_util.h
+++ b/mypyc/lib-rt/mypyc_util.h
@@ -23,6 +23,31 @@
 #define CPy_NOINLINE
 #endif
 
+#ifndef Py_GIL_DISABLED
+
+// Everything is running in the same thread, so no need for thread locals
+#define CPyThreadLocal
+
+#else
+
+// 1. Use C11 standard thread_local storage, if available
+#if defined(__STDC_VERSION__)  && __STDC_VERSION__ >= 201112L && !defined(__STDC_NO_THREADS__)
+#define CPyThreadLocal _Thread_local
+
+// 2. Microsoft Visual Studio fallback
+#elif defined(_MSC_VER)
+#define CPyThreadLocal __declspec(thread)
+
+// 3. GNU thread local storage for GCC/Clang targets that still need it
+#elif defined(__GNUC__) || defined(__clang__)
+#define CPyThreadLocal __thread
+
+#else
+#error "Can't define CPyThreadLocal for this compiler/target (consider using a non-free-threaded Python build)"
+#endif
+
+#endif // Py_GIL_DISABLED
+
 // INCREF and DECREF that assert the pointer is not NULL.
 // asserts are disabled in release builds so there shouldn't be a perf hit.
 // I'm honestly kind of surprised that this isn't done by default.
@@ -114,8 +139,10 @@ static inline CPyTagged CPyTagged_ShortFromSsize_t(Py_ssize_t x) {
     return x << 1;
 }
 
-// Are we targeting Python 3.12 or newer?
+// Are we targeting Python 3.X or newer?
+#define CPY_3_11_FEATURES (PY_VERSION_HEX >= 0x030b0000)
 #define CPY_3_12_FEATURES (PY_VERSION_HEX >= 0x030c0000)
+#define CPY_3_14_FEATURES (PY_VERSION_HEX >= 0x030e0000)
 
 #if CPY_3_12_FEATURES
 
diff --git a/mypyc/lib-rt/native_internal.c b/mypyc/lib-rt/native_internal.c
new file mode 100644
index 000000000000..a6511a1caf25
--- /dev/null
+++ b/mypyc/lib-rt/native_internal.c
@@ -0,0 +1,635 @@
+#define PY_SSIZE_T_CLEAN
+#include <Python.h>
+#include <stdint.h>
+#include "CPy.h"
+#define NATIVE_INTERNAL_MODULE
+#include "native_internal.h"
+
+#define START_SIZE 512
+#define MAX_SHORT_INT_TAGGED (255 << 1)
+
+#define MAX_SHORT_LEN 127
+#define LONG_STR_TAG 1
+
+#define MIN_SHORT_INT -10
+#define MAX_SHORT_INT 117
+#define MEDIUM_INT_TAG 1
+#define LONG_INT_TAG 3
+
+#define CPY_BOOL_ERROR 2
+#define CPY_NONE_ERROR 2
+#define CPY_NONE 1
+
+#define _CHECK_BUFFER(data, err)      if (unlikely(_check_buffer(data) == CPY_NONE_ERROR)) \
+                                          return err;
+#define _CHECK_SIZE(data, need)       if (unlikely(_check_size((BufferObject *)data, need) == CPY_NONE_ERROR)) \
+                                          return CPY_NONE_ERROR;
+#define _CHECK_READ(data, size, err)  if (unlikely(_check_read((BufferObject *)data, size) == CPY_NONE_ERROR)) \
+                                          return err;
+
+#define _READ(data, type)  *(type *)(((BufferObject *)data)->buf + ((BufferObject *)data)->pos); \
+                           ((BufferObject *)data)->pos += sizeof(type);
+
+#define _WRITE(data, type, v)  *(type *)(((BufferObject *)data)->buf + ((BufferObject *)data)->pos) = v; \
+                               ((BufferObject *)data)->pos += sizeof(type);
+
+typedef struct {
+    PyObject_HEAD
+    Py_ssize_t pos;
+    Py_ssize_t end;
+    Py_ssize_t size;
+    char *buf;
+    PyObject *source;
+} BufferObject;
+
+static PyTypeObject BufferType;
+
+static PyObject*
+Buffer_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
+{
+    if (type != &BufferType) {
+        PyErr_SetString(PyExc_TypeError, "Buffer should not be subclassed");
+        return NULL;
+    }
+
+    BufferObject *self = (BufferObject *)type->tp_alloc(type, 0);
+    if (self != NULL) {
+        self->pos = 0;
+        self->end = 0;
+        self->size = 0;
+        self->buf = NULL;
+    }
+    return (PyObject *) self;
+}
+
+
+static int
+Buffer_init_internal(BufferObject *self, PyObject *source) {
+    if (source) {
+        if (!PyBytes_Check(source)) {
+            PyErr_SetString(PyExc_TypeError, "source must be a bytes object");
+            return -1;
+        }
+        self->size = PyBytes_GET_SIZE(source);
+        self->end = self->size;
+        // This returns a pointer to internal bytes data, so make our own copy.
+        char *buf = PyBytes_AsString(source);
+        self->buf = PyMem_Malloc(self->size);
+        memcpy(self->buf, buf, self->size);
+    } else {
+        self->buf = PyMem_Malloc(START_SIZE);
+        self->size = START_SIZE;
+    }
+    return 0;
+}
+
+static PyObject*
+Buffer_internal(PyObject *source) {
+    BufferObject *self = (BufferObject *)BufferType.tp_alloc(&BufferType, 0);
+    if (self == NULL)
+        return NULL;
+    self->pos = 0;
+    self->end = 0;
+    self->size = 0;
+    self->buf = NULL;
+    if (Buffer_init_internal(self, source) == -1) {
+        Py_DECREF(self);
+        return NULL;
+    }
+    return (PyObject *)self;
+}
+
+static PyObject*
+Buffer_internal_empty(void) {
+    return Buffer_internal(NULL);
+}
+
+static int
+Buffer_init(BufferObject *self, PyObject *args, PyObject *kwds)
+{
+    static char *kwlist[] = {"source", NULL};
+    PyObject *source = NULL;
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "|O", kwlist, &source))
+        return -1;
+
+    return Buffer_init_internal(self, source);
+}
+
+static void
+Buffer_dealloc(BufferObject *self)
+{
+    PyMem_Free(self->buf);
+    Py_TYPE(self)->tp_free((PyObject *)self);
+}
+
+static PyObject*
+Buffer_getvalue_internal(PyObject *self)
+{
+    return PyBytes_FromStringAndSize(((BufferObject *)self)->buf, ((BufferObject *)self)->end);
+}
+
+static PyObject*
+Buffer_getvalue(BufferObject *self, PyObject *Py_UNUSED(ignored))
+{
+    return PyBytes_FromStringAndSize(self->buf, self->end);
+}
+
+static PyMethodDef Buffer_methods[] = {
+    {"getvalue", (PyCFunction) Buffer_getvalue, METH_NOARGS,
+     "Return the buffer content as bytes object"
+    },
+    {NULL}  /* Sentinel */
+};
+
+static PyTypeObject BufferType = {
+    .ob_base = PyVarObject_HEAD_INIT(NULL, 0)
+    .tp_name = "Buffer",
+    .tp_doc = PyDoc_STR("Mypy cache buffer objects"),
+    .tp_basicsize = sizeof(BufferObject),
+    .tp_itemsize = 0,
+    .tp_flags = Py_TPFLAGS_DEFAULT,
+    .tp_new = Buffer_new,
+    .tp_init = (initproc) Buffer_init,
+    .tp_dealloc = (destructor) Buffer_dealloc,
+    .tp_methods = Buffer_methods,
+};
+
+static inline char
+_check_buffer(PyObject *data) {
+    if (unlikely(Py_TYPE(data) != &BufferType)) {
+        PyErr_Format(
+            PyExc_TypeError, "data must be a Buffer object, got %s", Py_TYPE(data)->tp_name
+        );
+        return CPY_NONE_ERROR;
+    }
+    return CPY_NONE;
+}
+
+static inline char
+_check_size(BufferObject *data, Py_ssize_t need) {
+    Py_ssize_t target = data->pos + need;
+    if (target <= data->size)
+        return CPY_NONE;
+    do
+        data->size *= 2;
+    while (target >= data->size);
+    data->buf = PyMem_Realloc(data->buf, data->size);
+    if (unlikely(data->buf == NULL)) {
+        PyErr_NoMemory();
+        return CPY_NONE_ERROR;
+    }
+    return CPY_NONE;
+}
+
+static inline char
+_check_read(BufferObject *data, Py_ssize_t need) {
+    if (unlikely(data->pos + need > data->end)) {
+        PyErr_SetString(PyExc_ValueError, "reading past the buffer end");
+        return CPY_NONE_ERROR;
+    }
+    return CPY_NONE;
+}
+
+/*
+bool format: single byte
+    \x00 - False
+    \x01 - True
+*/
+
+static char
+read_bool_internal(PyObject *data) {
+    _CHECK_BUFFER(data, CPY_BOOL_ERROR)
+    _CHECK_READ(data, 1, CPY_BOOL_ERROR)
+    char res = _READ(data, char)
+    return res;
+}
+
+static PyObject*
+read_bool(PyObject *self, PyObject *const *args, size_t nargs, PyObject *kwnames) {
+    static const char * const kwlist[] = {"data", 0};
+    static CPyArg_Parser parser = {"O:read_bool", kwlist, 0};
+    PyObject *data;
+    if (unlikely(!CPyArg_ParseStackAndKeywordsOneArg(args, nargs, kwnames, &parser, &data))) {
+        return NULL;
+    }
+    char res = read_bool_internal(data);
+    if (unlikely(res == CPY_BOOL_ERROR))
+        return NULL;
+    PyObject *retval = res ? Py_True : Py_False;
+    Py_INCREF(retval);
+    return retval;
+}
+
+static char
+write_bool_internal(PyObject *data, char value) {
+    _CHECK_BUFFER(data, CPY_NONE_ERROR)
+    _CHECK_SIZE(data, 1)
+    _WRITE(data, char, value)
+    ((BufferObject *)data)->end += 1;
+    return CPY_NONE;
+}
+
+static PyObject*
+write_bool(PyObject *self, PyObject *const *args, size_t nargs, PyObject *kwnames) {
+    static const char * const kwlist[] = {"data", "value", 0};
+    static CPyArg_Parser parser = {"OO:write_bool", kwlist, 0};
+    PyObject *data;
+    PyObject *value;
+    if (unlikely(!CPyArg_ParseStackAndKeywordsSimple(args, nargs, kwnames, &parser, &data, &value))) {
+        return NULL;
+    }
+    if (unlikely(!PyBool_Check(value))) {
+        PyErr_SetString(PyExc_TypeError, "value must be a bool");
+        return NULL;
+    }
+    if (unlikely(write_bool_internal(data, value == Py_True) == CPY_NONE_ERROR)) {
+        return NULL;
+    }
+    Py_INCREF(Py_None);
+    return Py_None;
+}
+
+/*
+str format: size followed by UTF-8 bytes
+    short strings (len <= 127): single byte for size as `(uint8_t)size << 1`
+    long strings: \x01 followed by size as Py_ssize_t
+*/
+
+static PyObject*
+read_str_internal(PyObject *data) {
+    _CHECK_BUFFER(data, NULL)
+
+    // Read string length.
+    Py_ssize_t size;
+    _CHECK_READ(data, 1, NULL)
+    uint8_t first = _READ(data, uint8_t)
+    if (likely(first != LONG_STR_TAG)) {
+        // Common case: short string (len <= 127).
+        size = (Py_ssize_t)(first >> 1);
+    } else {
+        _CHECK_READ(data, sizeof(CPyTagged), NULL)
+        size = _READ(data, Py_ssize_t)
+    }
+    // Read string content.
+    char *buf = ((BufferObject *)data)->buf;
+    _CHECK_READ(data, size, NULL)
+    PyObject *res = PyUnicode_FromStringAndSize(
+        buf + ((BufferObject *)data)->pos, (Py_ssize_t)size
+    );
+    if (unlikely(res == NULL))
+        return NULL;
+    ((BufferObject *)data)->pos += size;
+    return res;
+}
+
+static PyObject*
+read_str(PyObject *self, PyObject *const *args, size_t nargs, PyObject *kwnames) {
+    static const char * const kwlist[] = {"data", 0};
+    static CPyArg_Parser parser = {"O:read_str", kwlist, 0};
+    PyObject *data;
+    if (unlikely(!CPyArg_ParseStackAndKeywordsOneArg(args, nargs, kwnames, &parser, &data))) {
+        return NULL;
+    }
+    return read_str_internal(data);
+}
+
+static char
+write_str_internal(PyObject *data, PyObject *value) {
+    _CHECK_BUFFER(data, CPY_NONE_ERROR)
+
+    Py_ssize_t size;
+    const char *chunk = PyUnicode_AsUTF8AndSize(value, &size);
+    if (unlikely(chunk == NULL))
+        return CPY_NONE_ERROR;
+
+    Py_ssize_t need;
+    // Write string length.
+    if (likely(size <= MAX_SHORT_LEN)) {
+        // Common case: short string (len <= 127) store as single byte.
+        need = size + 1;
+        _CHECK_SIZE(data, need)
+        _WRITE(data, uint8_t, (uint8_t)size << 1)
+    } else {
+        need = size + sizeof(Py_ssize_t) + 1;
+        _CHECK_SIZE(data, need)
+        _WRITE(data, uint8_t, LONG_STR_TAG)
+        _WRITE(data, Py_ssize_t, size)
+    }
+    // Write string content.
+    char *buf = ((BufferObject *)data)->buf;
+    memcpy(buf + ((BufferObject *)data)->pos, chunk, size);
+    ((BufferObject *)data)->pos += size;
+    ((BufferObject *)data)->end += need;
+    return CPY_NONE;
+}
+
+static PyObject*
+write_str(PyObject *self, PyObject *const *args, size_t nargs, PyObject *kwnames) {
+    static const char * const kwlist[] = {"data", "value", 0};
+    static CPyArg_Parser parser = {"OO:write_str", kwlist, 0};
+    PyObject *data;
+    PyObject *value;
+    if (unlikely(!CPyArg_ParseStackAndKeywordsSimple(args, nargs, kwnames, &parser, &data, &value))) {
+        return NULL;
+    }
+    if (unlikely(!PyUnicode_Check(value))) {
+        PyErr_SetString(PyExc_TypeError, "value must be a str");
+        return NULL;
+    }
+    if (unlikely(write_str_internal(data, value) == CPY_NONE_ERROR)) {
+        return NULL;
+    }
+    Py_INCREF(Py_None);
+    return Py_None;
+}
+
+/*
+float format:
+    stored as a C double
+*/
+
+static double
+read_float_internal(PyObject *data) {
+    _CHECK_BUFFER(data, CPY_FLOAT_ERROR)
+    _CHECK_READ(data, sizeof(double), CPY_FLOAT_ERROR)
+    double res = _READ(data, double);
+    return res;
+}
+
+static PyObject*
+read_float(PyObject *self, PyObject *const *args, size_t nargs, PyObject *kwnames) {
+    static const char * const kwlist[] = {"data", 0};
+    static CPyArg_Parser parser = {"O:read_float", kwlist, 0};
+    PyObject *data;
+    if (unlikely(!CPyArg_ParseStackAndKeywordsOneArg(args, nargs, kwnames, &parser, &data))) {
+        return NULL;
+    }
+    double retval = read_float_internal(data);
+    if (unlikely(retval == CPY_FLOAT_ERROR && PyErr_Occurred())) {
+        return NULL;
+    }
+    return PyFloat_FromDouble(retval);
+}
+
+static char
+write_float_internal(PyObject *data, double value) {
+    _CHECK_BUFFER(data, CPY_NONE_ERROR)
+    _CHECK_SIZE(data, sizeof(double))
+    _WRITE(data, double, value)
+    ((BufferObject *)data)->end += sizeof(double);
+    return CPY_NONE;
+}
+
+static PyObject*
+write_float(PyObject *self, PyObject *const *args, size_t nargs, PyObject *kwnames) {
+    static const char * const kwlist[] = {"data", "value", 0};
+    static CPyArg_Parser parser = {"OO:write_float", kwlist, 0};
+    PyObject *data;
+    PyObject *value;
+    if (unlikely(!CPyArg_ParseStackAndKeywordsSimple(args, nargs, kwnames, &parser, &data, &value))) {
+        return NULL;
+    }
+    if (unlikely(!PyFloat_Check(value))) {
+        PyErr_SetString(PyExc_TypeError, "value must be a float");
+        return NULL;
+    }
+    if (unlikely(write_float_internal(data, PyFloat_AsDouble(value)) == CPY_NONE_ERROR)) {
+        return NULL;
+    }
+    Py_INCREF(Py_None);
+    return Py_None;
+}
+
+/*
+int format:
+    most common values (-10 <= value <= 117): single byte as `(uint8_t)(value + 10) << 1`
+    medium values (fit in CPyTagged): \x01 followed by CPyTagged value
+    long values (very rare): \x03 followed by decimal string (see str format)
+*/
+
+static CPyTagged
+read_int_internal(PyObject *data) {
+    _CHECK_BUFFER(data, CPY_INT_TAG)
+    _CHECK_READ(data, 1, CPY_INT_TAG)
+
+    uint8_t first = _READ(data, uint8_t)
+    if ((first & MEDIUM_INT_TAG) == 0) {
+       // Most common case: int that is small in absolute value.
+       return ((Py_ssize_t)(first >> 1) + MIN_SHORT_INT) << 1;
+    }
+    if (first == MEDIUM_INT_TAG) {
+        _CHECK_READ(data, sizeof(CPyTagged), CPY_INT_TAG)
+        CPyTagged ret = _READ(data, CPyTagged)
+        return ret;
+    }
+    // People who have literal ints not fitting in size_t should be punished :-)
+    PyObject *str_ret = read_str_internal(data);
+    if (unlikely(str_ret == NULL))
+        return CPY_INT_TAG;
+    PyObject* ret_long = PyLong_FromUnicodeObject(str_ret, 10);
+    Py_DECREF(str_ret);
+    return ((CPyTagged)ret_long) | CPY_INT_TAG;
+}
+
+static PyObject*
+read_int(PyObject *self, PyObject *const *args, size_t nargs, PyObject *kwnames) {
+    static const char * const kwlist[] = {"data", 0};
+    static CPyArg_Parser parser = {"O:read_int", kwlist, 0};
+    PyObject *data;
+    if (unlikely(!CPyArg_ParseStackAndKeywordsOneArg(args, nargs, kwnames, &parser, &data))) {
+        return NULL;
+    }
+    CPyTagged retval = read_int_internal(data);
+    if (unlikely(retval == CPY_INT_TAG)) {
+        return NULL;
+    }
+    return CPyTagged_StealAsObject(retval);
+}
+
+static char
+write_int_internal(PyObject *data, CPyTagged value) {
+    _CHECK_BUFFER(data, CPY_NONE_ERROR)
+
+    if (likely((value & CPY_INT_TAG) == 0)) {
+        Py_ssize_t real_value = CPyTagged_ShortAsSsize_t(value);
+        if (real_value >= MIN_SHORT_INT && real_value <= MAX_SHORT_INT) {
+            // Most common case: int that is small in absolute value.
+            _CHECK_SIZE(data, 1)
+            _WRITE(data, uint8_t, (uint8_t)(real_value - MIN_SHORT_INT) << 1)
+            ((BufferObject *)data)->end += 1;
+        } else {
+            _CHECK_SIZE(data, sizeof(CPyTagged) + 1)
+            _WRITE(data, uint8_t, MEDIUM_INT_TAG)
+            _WRITE(data, CPyTagged, value)
+            ((BufferObject *)data)->end += sizeof(CPyTagged) + 1;
+        }
+    } else {
+        _CHECK_SIZE(data, 1)
+        _WRITE(data, uint8_t, LONG_INT_TAG)
+        ((BufferObject *)data)->end += 1;
+        PyObject *str_value = PyObject_Str(CPyTagged_LongAsObject(value));
+        if (unlikely(str_value == NULL))
+            return CPY_NONE_ERROR;
+        char res = write_str_internal(data, str_value);
+        Py_DECREF(str_value);
+        if (unlikely(res == CPY_NONE_ERROR))
+            return CPY_NONE_ERROR;
+    }
+    return CPY_NONE;
+}
+
+static PyObject*
+write_int(PyObject *self, PyObject *const *args, size_t nargs, PyObject *kwnames) {
+    static const char * const kwlist[] = {"data", "value", 0};
+    static CPyArg_Parser parser = {"OO:write_int", kwlist, 0};
+    PyObject *data;
+    PyObject *value;
+    if (unlikely(!CPyArg_ParseStackAndKeywordsSimple(args, nargs, kwnames, &parser, &data, &value))) {
+        return NULL;
+    }
+    if (unlikely(!PyLong_Check(value))) {
+        PyErr_SetString(PyExc_TypeError, "value must be an int");
+        return NULL;
+    }
+    CPyTagged tagged_value = CPyTagged_BorrowFromObject(value);
+    if (unlikely(write_int_internal(data, tagged_value) == CPY_NONE_ERROR)) {
+        return NULL;
+    }
+    Py_INCREF(Py_None);
+    return Py_None;
+}
+
+/*
+integer tag format (0 <= t <= 255):
+    stored as a uint8_t
+*/
+
+static uint8_t
+read_tag_internal(PyObject *data) {
+    _CHECK_BUFFER(data, CPY_LL_UINT_ERROR)
+    _CHECK_READ(data, 1, CPY_LL_UINT_ERROR)
+    uint8_t ret = _READ(data, uint8_t)
+    return ret;
+}
+
+static PyObject*
+read_tag(PyObject *self, PyObject *const *args, size_t nargs, PyObject *kwnames) {
+    static const char * const kwlist[] = {"data", 0};
+    static CPyArg_Parser parser = {"O:read_tag", kwlist, 0};
+    PyObject *data;
+    if (unlikely(!CPyArg_ParseStackAndKeywordsOneArg(args, nargs, kwnames, &parser, &data))) {
+        return NULL;
+    }
+    uint8_t retval = read_tag_internal(data);
+    if (unlikely(retval == CPY_LL_UINT_ERROR && PyErr_Occurred())) {
+        return NULL;
+    }
+    return PyLong_FromLong(retval);
+}
+
+static char
+write_tag_internal(PyObject *data, uint8_t value) {
+    _CHECK_BUFFER(data, CPY_NONE_ERROR)
+    _CHECK_SIZE(data, 1)
+    _WRITE(data, uint8_t, value)
+    ((BufferObject *)data)->end += 1;
+    return CPY_NONE;
+}
+
+static PyObject*
+write_tag(PyObject *self, PyObject *const *args, size_t nargs, PyObject *kwnames) {
+    static const char * const kwlist[] = {"data", "value", 0};
+    static CPyArg_Parser parser = {"OO:write_tag", kwlist, 0};
+    PyObject *data;
+    PyObject *value;
+    if (unlikely(!CPyArg_ParseStackAndKeywordsSimple(args, nargs, kwnames, &parser, &data, &value))) {
+        return NULL;
+    }
+    uint8_t unboxed = CPyLong_AsUInt8(value);
+    if (unlikely(unboxed == CPY_LL_UINT_ERROR && PyErr_Occurred())) {
+        CPy_TypeError("u8", value);
+        return NULL;
+    }
+    if (unlikely(write_tag_internal(data, unboxed) == CPY_NONE_ERROR)) {
+        return NULL;
+    }
+    Py_INCREF(Py_None);
+    return Py_None;
+}
+
+static PyMethodDef native_internal_module_methods[] = {
+    {"write_bool", (PyCFunction)write_bool, METH_FASTCALL | METH_KEYWORDS, PyDoc_STR("write a bool")},
+    {"read_bool", (PyCFunction)read_bool, METH_FASTCALL | METH_KEYWORDS, PyDoc_STR("read a bool")},
+    {"write_str", (PyCFunction)write_str, METH_FASTCALL | METH_KEYWORDS, PyDoc_STR("write a string")},
+    {"read_str", (PyCFunction)read_str, METH_FASTCALL | METH_KEYWORDS, PyDoc_STR("read a string")},
+    {"write_float", (PyCFunction)write_float, METH_FASTCALL | METH_KEYWORDS, PyDoc_STR("write a float")},
+    {"read_float", (PyCFunction)read_float, METH_FASTCALL | METH_KEYWORDS, PyDoc_STR("read a float")},
+    {"write_int", (PyCFunction)write_int, METH_FASTCALL | METH_KEYWORDS, PyDoc_STR("write an int")},
+    {"read_int", (PyCFunction)read_int, METH_FASTCALL | METH_KEYWORDS, PyDoc_STR("read an int")},
+    {"write_tag", (PyCFunction)write_tag, METH_FASTCALL | METH_KEYWORDS, PyDoc_STR("write a short int")},
+    {"read_tag", (PyCFunction)read_tag, METH_FASTCALL | METH_KEYWORDS, PyDoc_STR("read a short int")},
+    {NULL, NULL, 0, NULL}
+};
+
+static int
+NativeInternal_ABI_Version(void) {
+    return NATIVE_INTERNAL_ABI_VERSION;
+}
+
+static int
+native_internal_module_exec(PyObject *m)
+{
+    if (PyType_Ready(&BufferType) < 0) {
+        return -1;
+    }
+    if (PyModule_AddObjectRef(m, "Buffer", (PyObject *) &BufferType) < 0) {
+        return -1;
+    }
+
+    // Export mypy internal C API, be careful with the order!
+    static void *NativeInternal_API[14] = {
+        (void *)Buffer_internal,
+        (void *)Buffer_internal_empty,
+        (void *)Buffer_getvalue_internal,
+        (void *)write_bool_internal,
+        (void *)read_bool_internal,
+        (void *)write_str_internal,
+        (void *)read_str_internal,
+        (void *)write_float_internal,
+        (void *)read_float_internal,
+        (void *)write_int_internal,
+        (void *)read_int_internal,
+        (void *)write_tag_internal,
+        (void *)read_tag_internal,
+        (void *)NativeInternal_ABI_Version,
+    };
+    PyObject *c_api_object = PyCapsule_New((void *)NativeInternal_API, "native_internal._C_API", NULL);
+    if (PyModule_Add(m, "_C_API", c_api_object) < 0) {
+        return -1;
+    }
+    return 0;
+}
+
+static PyModuleDef_Slot native_internal_module_slots[] = {
+    {Py_mod_exec, native_internal_module_exec},
+#ifdef Py_MOD_GIL_NOT_USED
+    {Py_mod_gil, Py_MOD_GIL_NOT_USED},
+#endif
+    {0, NULL}
+};
+
+static PyModuleDef native_internal_module = {
+    .m_base = PyModuleDef_HEAD_INIT,
+    .m_name = "native_internal",
+    .m_doc = "Mypy cache serialization utils",
+    .m_size = 0,
+    .m_methods = native_internal_module_methods,
+    .m_slots = native_internal_module_slots,
+};
+
+PyMODINIT_FUNC
+PyInit_native_internal(void)
+{
+    return PyModuleDef_Init(&native_internal_module);
+}
diff --git a/mypyc/lib-rt/native_internal.h b/mypyc/lib-rt/native_internal.h
new file mode 100644
index 000000000000..63e902a6e1bf
--- /dev/null
+++ b/mypyc/lib-rt/native_internal.h
@@ -0,0 +1,56 @@
+#ifndef NATIVE_INTERNAL_H
+#define NATIVE_INTERNAL_H
+
+#define NATIVE_INTERNAL_ABI_VERSION 0
+
+#ifdef NATIVE_INTERNAL_MODULE
+
+static PyObject *Buffer_internal(PyObject *source);
+static PyObject *Buffer_internal_empty(void);
+static PyObject *Buffer_getvalue_internal(PyObject *self);
+static char write_bool_internal(PyObject *data, char value);
+static char read_bool_internal(PyObject *data);
+static char write_str_internal(PyObject *data, PyObject *value);
+static PyObject *read_str_internal(PyObject *data);
+static char write_float_internal(PyObject *data, double value);
+static double read_float_internal(PyObject *data);
+static char write_int_internal(PyObject *data, CPyTagged value);
+static CPyTagged read_int_internal(PyObject *data);
+static char write_tag_internal(PyObject *data, uint8_t value);
+static uint8_t read_tag_internal(PyObject *data);
+static int NativeInternal_ABI_Version(void);
+
+#else
+
+static void **NativeInternal_API;
+
+#define Buffer_internal (*(PyObject* (*)(PyObject *source)) NativeInternal_API[0])
+#define Buffer_internal_empty (*(PyObject* (*)(void)) NativeInternal_API[1])
+#define Buffer_getvalue_internal (*(PyObject* (*)(PyObject *source)) NativeInternal_API[2])
+#define write_bool_internal (*(char (*)(PyObject *source, char value)) NativeInternal_API[3])
+#define read_bool_internal (*(char (*)(PyObject *source)) NativeInternal_API[4])
+#define write_str_internal (*(char (*)(PyObject *source, PyObject *value)) NativeInternal_API[5])
+#define read_str_internal (*(PyObject* (*)(PyObject *source)) NativeInternal_API[6])
+#define write_float_internal (*(char (*)(PyObject *source, double value)) NativeInternal_API[7])
+#define read_float_internal (*(double (*)(PyObject *source)) NativeInternal_API[8])
+#define write_int_internal (*(char (*)(PyObject *source, CPyTagged value)) NativeInternal_API[9])
+#define read_int_internal (*(CPyTagged (*)(PyObject *source)) NativeInternal_API[10])
+#define write_tag_internal (*(char (*)(PyObject *source, uint8_t value)) NativeInternal_API[11])
+#define read_tag_internal (*(uint8_t (*)(PyObject *source)) NativeInternal_API[12])
+#define NativeInternal_ABI_Version (*(int (*)(void)) NativeInternal_API[13])
+
+static int
+import_native_internal(void)
+{
+    NativeInternal_API = (void **)PyCapsule_Import("native_internal._C_API", 0);
+    if (NativeInternal_API == NULL)
+        return -1;
+    if (NativeInternal_ABI_Version() != NATIVE_INTERNAL_ABI_VERSION) {
+        PyErr_SetString(PyExc_ValueError, "ABI version conflict for native_internal");
+        return -1;
+    }
+    return 0;
+}
+
+#endif
+#endif  // NATIVE_INTERNAL_H
diff --git a/mypyc/lib-rt/setup.py b/mypyc/lib-rt/setup.py
index 1faacc8fc136..3a5976cf88b2 100644
--- a/mypyc/lib-rt/setup.py
+++ b/mypyc/lib-rt/setup.py
@@ -12,60 +12,81 @@
 from distutils.core import Extension, setup
 from typing import Any
 
-kwargs: dict[str, Any]
-if sys.platform == "darwin":
-    kwargs = {"language": "c++"}
-    compile_args = []
-else:
-    kwargs = {}
-    compile_args = ["--std=c++11"]
+C_APIS_TO_TEST = [
+    "init.c",
+    "int_ops.c",
+    "float_ops.c",
+    "list_ops.c",
+    "exc_ops.c",
+    "generic_ops.c",
+    "pythonsupport.c",
+]
 
 
-class build_ext_custom(build_ext):  # noqa: N801
-    def get_library_names(self):
+class BuildExtGtest(build_ext):
+    def get_library_names(self) -> list[str]:
         return ["gtest"]
 
-    def run(self):
+    def run(self) -> None:
+        # Build Google Test, the C++ framework we use for testing C code.
+        # The source code for Google Test is copied to this repository.
         gtest_dir = os.path.abspath(
             os.path.join(os.path.dirname(__file__), "..", "external", "googletest")
         )
-
         os.makedirs(self.build_temp, exist_ok=True)
-
-        # Build Google Test, the C++ framework we use for testing C code.
-        # The source code for Google Test is copied to this repository.
         subprocess.check_call(
             ["make", "-f", os.path.join(gtest_dir, "make", "Makefile"), f"GTEST_DIR={gtest_dir}"],
             cwd=self.build_temp,
         )
-
         self.library_dirs = [self.build_temp]
-
         return build_ext.run(self)
 
 
-setup(
-    name="test_capi",
-    version="0.1",
-    ext_modules=[
-        Extension(
-            "test_capi",
-            [
-                "test_capi.cc",
-                "init.c",
-                "int_ops.c",
-                "float_ops.c",
-                "list_ops.c",
-                "exc_ops.c",
-                "generic_ops.c",
-                "pythonsupport.c",
-            ],
-            depends=["CPy.h", "mypyc_util.h", "pythonsupport.h"],
-            extra_compile_args=["-Wno-unused-function", "-Wno-sign-compare"] + compile_args,
-            libraries=["gtest"],
-            include_dirs=["../external/googletest", "../external/googletest/include"],
-            **kwargs,
-        )
-    ],
-    cmdclass={"build_ext": build_ext_custom},
-)
+if "--run-capi-tests" in sys.argv:
+    sys.argv.pop()
+
+    kwargs: dict[str, Any]
+    if sys.platform == "darwin":
+        kwargs = {"language": "c++"}
+        compile_args = []
+    else:
+        kwargs = {}
+        compile_args = ["--std=c++11"]
+
+    setup(
+        name="test_capi",
+        version="0.1",
+        ext_modules=[
+            Extension(
+                "test_capi",
+                ["test_capi.cc"] + C_APIS_TO_TEST,
+                depends=["CPy.h", "mypyc_util.h", "pythonsupport.h"],
+                extra_compile_args=["-Wno-unused-function", "-Wno-sign-compare"] + compile_args,
+                libraries=["gtest"],
+                include_dirs=["../external/googletest", "../external/googletest/include"],
+                **kwargs,
+            )
+        ],
+        cmdclass={"build_ext": BuildExtGtest},
+    )
+else:
+    # TODO: we need a way to share our preferred C flags and get_extension() logic with
+    # mypyc/build.py without code duplication.
+    setup(
+        name="mypy-native",
+        version="0.0.1",
+        ext_modules=[
+            Extension(
+                "native_internal",
+                [
+                    "native_internal.c",
+                    "init.c",
+                    "int_ops.c",
+                    "exc_ops.c",
+                    "pythonsupport.c",
+                    "getargsfast.c",
+                ],
+                include_dirs=["."],
+            )
+        ],
+    )
diff --git a/mypyc/lib-rt/str_ops.c b/mypyc/lib-rt/str_ops.c
index 49fcbb8c6876..337ef14fc955 100644
--- a/mypyc/lib-rt/str_ops.c
+++ b/mypyc/lib-rt/str_ops.c
@@ -64,6 +64,22 @@ make_bloom_mask(int kind, const void* ptr, Py_ssize_t len)
 #undef BLOOM_UPDATE
 }
 
+// Adapted from CPython 3.13.1 (_PyUnicode_Equal)
+char CPyStr_Equal(PyObject *str1, PyObject *str2) {
+    if (str1 == str2) {
+        return 1;
+    }
+    Py_ssize_t len = PyUnicode_GET_LENGTH(str1);
+    if (PyUnicode_GET_LENGTH(str2) != len)
+        return 0;
+    int kind = PyUnicode_KIND(str1);
+    if (PyUnicode_KIND(str2) != kind)
+        return 0;
+    const void *data1 = PyUnicode_DATA(str1);
+    const void *data2 = PyUnicode_DATA(str2);
+    return memcmp(data1, data2, len * kind) == 0;
+}
+
 PyObject *CPyStr_GetItem(PyObject *str, CPyTagged index) {
     if (PyUnicode_READY(str) != -1) {
         if (CPyTagged_CheckShort(index)) {
@@ -101,6 +117,11 @@ PyObject *CPyStr_GetItem(PyObject *str, CPyTagged index) {
     }
 }
 
+PyObject *CPyStr_GetItemUnsafe(PyObject *str, Py_ssize_t index) {
+    // This is unsafe since we don't check for overflow when doing <<.
+    return CPyStr_GetItem(str, index << 1);
+}
+
 // A simplification of _PyUnicode_JoinArray() from CPython 3.9.6
 PyObject *CPyStr_Build(Py_ssize_t len, ...) {
     Py_ssize_t i;
@@ -492,6 +513,45 @@ PyObject *CPy_Decode(PyObject *obj, PyObject *encoding, PyObject *errors) {
     }
 }
 
+PyObject *CPy_DecodeUTF8(PyObject *bytes) {
+    if (PyBytes_CheckExact(bytes)) {
+        char *buffer = PyBytes_AsString(bytes);   // Borrowed reference
+        if (buffer == NULL) {
+            return NULL;
+        }
+        Py_ssize_t size = PyBytes_Size(bytes);
+        return PyUnicode_DecodeUTF8(buffer, size, "strict");
+    } else {
+        return PyUnicode_FromEncodedObject(bytes, "utf-8", "strict");
+    }
+}
+
+PyObject *CPy_DecodeASCII(PyObject *bytes) {
+    if (PyBytes_CheckExact(bytes)) {
+        char *buffer = PyBytes_AsString(bytes);   // Borrowed reference
+        if (buffer == NULL) {
+            return NULL;
+        }
+        Py_ssize_t size = PyBytes_Size(bytes);
+        return PyUnicode_DecodeASCII(buffer, size, "strict");;
+    } else {
+        return PyUnicode_FromEncodedObject(bytes, "ascii", "strict");
+    }
+}
+
+PyObject *CPy_DecodeLatin1(PyObject *bytes) {
+    if (PyBytes_CheckExact(bytes)) {
+        char *buffer = PyBytes_AsString(bytes);   // Borrowed reference
+        if (buffer == NULL) {
+            return NULL;
+        }
+        Py_ssize_t size = PyBytes_Size(bytes);
+        return PyUnicode_DecodeLatin1(buffer, size, "strict");
+    } else {
+        return PyUnicode_FromEncodedObject(bytes, "latin1", "strict");
+    }
+}
+
 PyObject *CPy_Encode(PyObject *obj, PyObject *encoding, PyObject *errors) {
     const char *enc = NULL;
     const char *err = NULL;
@@ -511,6 +571,30 @@ PyObject *CPy_Encode(PyObject *obj, PyObject *encoding, PyObject *errors) {
     }
 }
 
+Py_ssize_t CPyStr_Count(PyObject *unicode, PyObject *substring, CPyTagged start) {
+    Py_ssize_t temp_start = CPyTagged_AsSsize_t(start);
+    if (temp_start == -1 && PyErr_Occurred()) {
+        PyErr_SetString(PyExc_OverflowError, CPYTHON_LARGE_INT_ERRMSG);
+        return -1;
+    }
+    Py_ssize_t end = PyUnicode_GET_LENGTH(unicode);
+    return PyUnicode_Count(unicode, substring, temp_start, end);
+}
+
+Py_ssize_t CPyStr_CountFull(PyObject *unicode, PyObject *substring, CPyTagged start, CPyTagged end) {
+    Py_ssize_t temp_start = CPyTagged_AsSsize_t(start);
+    if (temp_start == -1 && PyErr_Occurred()) {
+        PyErr_SetString(PyExc_OverflowError, CPYTHON_LARGE_INT_ERRMSG);
+        return -1;
+    }
+    Py_ssize_t temp_end = CPyTagged_AsSsize_t(end);
+    if (temp_end == -1 && PyErr_Occurred()) {
+        PyErr_SetString(PyExc_OverflowError, CPYTHON_LARGE_INT_ERRMSG);
+        return -1;
+    }
+    return PyUnicode_Count(unicode, substring, temp_start, temp_end);
+}
+
 
 CPyTagged CPyStr_Ord(PyObject *obj) {
     Py_ssize_t s = PyUnicode_GET_LENGTH(obj);
diff --git a/mypyc/lib-rt/tuple_ops.c b/mypyc/lib-rt/tuple_ops.c
index 64418974666f..1df73f1907e2 100644
--- a/mypyc/lib-rt/tuple_ops.c
+++ b/mypyc/lib-rt/tuple_ops.c
@@ -46,16 +46,17 @@ PyObject *CPySequenceTuple_GetSlice(PyObject *obj, CPyTagged start, CPyTagged en
     return CPyObject_GetSlice(obj, start, end);
 }
 
+// No error checking
+PyObject *CPySequenceTuple_GetItemUnsafe(PyObject *tuple, Py_ssize_t index)
+{
+    PyObject *result = PyTuple_GET_ITEM(tuple, index);
+    Py_INCREF(result);
+    return result;
+}
+
 // PyTuple_SET_ITEM does no error checking,
 // and should only be used to fill in brand new tuples.
-bool CPySequenceTuple_SetItemUnsafe(PyObject *tuple, CPyTagged index, PyObject *value)
+void CPySequenceTuple_SetItemUnsafe(PyObject *tuple, Py_ssize_t index, PyObject *value)
 {
-    if (CPyTagged_CheckShort(index)) {
-        Py_ssize_t n = CPyTagged_ShortAsSsize_t(index);
-        PyTuple_SET_ITEM(tuple, n, value);
-        return true;
-    } else {
-        PyErr_SetString(PyExc_OverflowError, CPYTHON_LARGE_INT_ERRMSG);
-        return false;
-    }
+    PyTuple_SET_ITEM(tuple, index, value);
 }
diff --git a/mypyc/lower/list_ops.py b/mypyc/lower/list_ops.py
index f719a9fcd23d..631008db5db6 100644
--- a/mypyc/lower/list_ops.py
+++ b/mypyc/lower/list_ops.py
@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 from mypyc.common import PLATFORM_SIZE
-from mypyc.ir.ops import GetElementPtr, IncRef, Integer, IntOp, LoadMem, SetMem, Value
+from mypyc.ir.ops import GetElementPtr, Integer, IntOp, SetMem, Value
 from mypyc.ir.rtypes import (
     PyListObject,
     c_pyssize_t_rprimitive,
@@ -22,7 +22,7 @@ def buf_init_item(builder: LowLevelIRBuilder, args: list[Value], line: int) -> V
     base = args[0]
     index_value = args[1]
     value = args[2]
-    assert isinstance(index_value, Integer)
+    assert isinstance(index_value, Integer), index_value
     index = index_value.numeric_value()
     if index == 0:
         ptr = base
@@ -42,7 +42,7 @@ def buf_init_item(builder: LowLevelIRBuilder, args: list[Value], line: int) -> V
 @lower_primitive_op("list_items")
 def list_items(builder: LowLevelIRBuilder, args: list[Value], line: int) -> Value:
     ob_item_ptr = builder.add(GetElementPtr(args[0], PyListObject, "ob_item", line))
-    return builder.add(LoadMem(pointer_rprimitive, ob_item_ptr, line))
+    return builder.load_mem(ob_item_ptr, pointer_rprimitive)
 
 
 def list_item_ptr(builder: LowLevelIRBuilder, obj: Value, index: Value, line: int) -> Value:
@@ -68,6 +68,4 @@ def list_item_ptr(builder: LowLevelIRBuilder, obj: Value, index: Value, line: in
 def list_get_item_unsafe(builder: LowLevelIRBuilder, args: list[Value], line: int) -> Value:
     index = builder.coerce(args[1], c_pyssize_t_rprimitive, line)
     item_ptr = list_item_ptr(builder, args[0], index, line)
-    value = builder.add(LoadMem(object_rprimitive, item_ptr, line))
-    builder.add(IncRef(value))
-    return value
+    return builder.load_mem(item_ptr, object_rprimitive)
diff --git a/mypyc/lower/misc_ops.py b/mypyc/lower/misc_ops.py
index 1effcd4f42ac..3c42257c0dbe 100644
--- a/mypyc/lower/misc_ops.py
+++ b/mypyc/lower/misc_ops.py
@@ -1,7 +1,7 @@
 from __future__ import annotations
 
-from mypyc.ir.ops import GetElementPtr, LoadMem, Value
-from mypyc.ir.rtypes import PyVarObject, c_pyssize_t_rprimitive
+from mypyc.ir.ops import ComparisonOp, GetElementPtr, Integer, LoadMem, Value
+from mypyc.ir.rtypes import PyVarObject, c_pyssize_t_rprimitive, object_rprimitive
 from mypyc.irbuild.ll_builder import LowLevelIRBuilder
 from mypyc.lower.registry import lower_primitive_op
 
@@ -10,3 +10,9 @@
 def var_object_size(builder: LowLevelIRBuilder, args: list[Value], line: int) -> Value:
     elem_address = builder.add(GetElementPtr(args[0], PyVarObject, "ob_size"))
     return builder.add(LoadMem(c_pyssize_t_rprimitive, elem_address))
+
+
+@lower_primitive_op("propagate_if_error")
+def propagate_if_error_op(builder: LowLevelIRBuilder, args: list[Value], line: int) -> Value:
+    # Return False on NULL. The primitive uses ERR_FALSE, so this is an error.
+    return builder.add(ComparisonOp(args[0], Integer(0, object_rprimitive), ComparisonOp.NEQ))
diff --git a/mypyc/options.py b/mypyc/options.py
index 51114926f6b2..c009d3c6a7a4 100644
--- a/mypyc/options.py
+++ b/mypyc/options.py
@@ -16,6 +16,8 @@ def __init__(
         python_version: tuple[int, int] | None = None,
         strict_dunder_typing: bool = False,
         group_name: str | None = None,
+        log_trace: bool = False,
+        depends_on_native_internal: bool = False,
     ) -> None:
         self.strip_asserts = strip_asserts
         self.multi_file = multi_file
@@ -45,3 +47,11 @@ def __init__(
         # library is generated (with shims). This can be used to make the output
         # file names more predictable.
         self.group_name = group_name
+        # If enabled, write a trace log of events based on executed operations to
+        # mypyc_trace.txt when compiled module is executed. This is useful for
+        # performance analysis.
+        self.log_trace = log_trace
+        # If enabled, add capsule imports of native_internal API. This should be used
+        # only for mypy itself, third-party code compiled with mypyc should not use
+        # native_internal.
+        self.depends_on_native_internal = depends_on_native_internal
diff --git a/mypyc/primitives/bytes_ops.py b/mypyc/primitives/bytes_ops.py
index 1afd196cff84..c88e89d1a2ba 100644
--- a/mypyc/primitives/bytes_ops.py
+++ b/mypyc/primitives/bytes_ops.py
@@ -2,9 +2,10 @@
 
 from __future__ import annotations
 
-from mypyc.ir.ops import ERR_MAGIC
+from mypyc.ir.ops import ERR_MAGIC, ERR_NEVER
 from mypyc.ir.rtypes import (
     RUnion,
+    bit_rprimitive,
     bytes_rprimitive,
     c_int_rprimitive,
     c_pyssize_t_rprimitive,
@@ -35,6 +36,15 @@
     error_kind=ERR_MAGIC,
 )
 
+# translate isinstance(obj, bytes)
+isinstance_bytes = function_op(
+    name="builtins.isinstance",
+    arg_types=[object_rprimitive],
+    return_type=bit_rprimitive,
+    c_function_name="PyBytes_Check",
+    error_kind=ERR_NEVER,
+)
+
 # bytearray(obj)
 function_op(
     name="builtins.bytearray",
@@ -44,6 +54,15 @@
     error_kind=ERR_MAGIC,
 )
 
+# translate isinstance(obj, bytearray)
+isinstance_bytearray = function_op(
+    name="builtins.isinstance",
+    arg_types=[object_rprimitive],
+    return_type=bit_rprimitive,
+    c_function_name="PyByteArray_Check",
+    error_kind=ERR_NEVER,
+)
+
 # bytes ==/!= (return -1/0/1)
 bytes_compare = custom_op(
     arg_types=[bytes_rprimitive, bytes_rprimitive],
diff --git a/mypyc/primitives/dict_ops.py b/mypyc/primitives/dict_ops.py
index ce7b9bb8d70e..f98bcc8ac2ec 100644
--- a/mypyc/primitives/dict_ops.py
+++ b/mypyc/primitives/dict_ops.py
@@ -53,7 +53,7 @@
 )
 
 # Construct a dictionary from another dictionary.
-function_op(
+dict_copy_op = function_op(
     name="builtins.dict",
     arg_types=[dict_rprimitive],
     return_type=dict_rprimitive,
@@ -71,6 +71,15 @@
     error_kind=ERR_MAGIC,
 )
 
+# translate isinstance(obj, dict)
+isinstance_dict = function_op(
+    name="builtins.isinstance",
+    arg_types=[object_rprimitive],
+    return_type=bit_rprimitive,
+    c_function_name="PyDict_Check",
+    error_kind=ERR_NEVER,
+)
+
 # dict[key]
 dict_get_item_op = method_op(
     name="__getitem__",
@@ -89,6 +98,15 @@
     error_kind=ERR_NEG_INT,
 )
 
+# dict[key] = value (exact dict only, no subclasses)
+# NOTE: this is currently for internal use only, and not used for CallExpr specialization
+exact_dict_set_item_op = custom_op(
+    arg_types=[dict_rprimitive, object_rprimitive, object_rprimitive],
+    return_type=c_int_rprimitive,
+    c_function_name="PyDict_SetItem",
+    error_kind=ERR_NEG_INT,
+)
+
 # key in dict
 binary_op(
     name="in",
@@ -289,7 +307,7 @@
 
 # check that len(dict) == const during iteration
 dict_check_size_op = custom_op(
-    arg_types=[dict_rprimitive, int_rprimitive],
+    arg_types=[dict_rprimitive, c_pyssize_t_rprimitive],
     return_type=bit_rprimitive,
     c_function_name="CPyDict_CheckSize",
     error_kind=ERR_FALSE,
diff --git a/mypyc/primitives/exc_ops.py b/mypyc/primitives/exc_ops.py
index 9a5f6392a917..e1234f807afa 100644
--- a/mypyc/primitives/exc_ops.py
+++ b/mypyc/primitives/exc_ops.py
@@ -4,7 +4,7 @@
 
 from mypyc.ir.ops import ERR_ALWAYS, ERR_FALSE, ERR_NEVER
 from mypyc.ir.rtypes import bit_rprimitive, exc_rtuple, object_rprimitive, void_rtype
-from mypyc.primitives.registry import custom_op
+from mypyc.primitives.registry import custom_op, custom_primitive_op
 
 # If the argument is a class, raise an instance of the class. Otherwise, assume
 # that the argument is an exception object, and raise it.
@@ -62,6 +62,16 @@
     error_kind=ERR_FALSE,
 )
 
+# If argument is NULL, propagate currently raised exception (in this case
+# an exception must have been raised). If this can be used, it's faster
+# than using PyErr_Occurred().
+propagate_if_error_op = custom_primitive_op(
+    "propagate_if_error",
+    arg_types=[object_rprimitive],
+    return_type=bit_rprimitive,
+    error_kind=ERR_FALSE,
+)
+
 # Catches a propagating exception and makes it the "currently
 # handled exception" (by sticking it into sys.exc_info()). Returns the
 # exception that was previously being handled, which must be restored
diff --git a/mypyc/primitives/float_ops.py b/mypyc/primitives/float_ops.py
index 14e8d4caf09c..542192add542 100644
--- a/mypyc/primitives/float_ops.py
+++ b/mypyc/primitives/float_ops.py
@@ -4,6 +4,7 @@
 
 from mypyc.ir.ops import ERR_MAGIC, ERR_MAGIC_OVERLAPPING, ERR_NEVER
 from mypyc.ir.rtypes import (
+    bit_rprimitive,
     bool_rprimitive,
     float_rprimitive,
     int_rprimitive,
@@ -166,3 +167,12 @@
     c_function_name="CPyFloat_IsNaN",
     error_kind=ERR_NEVER,
 )
+
+# translate isinstance(obj, float)
+isinstance_float = function_op(
+    name="builtins.isinstance",
+    arg_types=[object_rprimitive],
+    return_type=bit_rprimitive,
+    c_function_name="PyFloat_Check",
+    error_kind=ERR_NEVER,
+)
diff --git a/mypyc/primitives/generic_ops.py b/mypyc/primitives/generic_ops.py
index 54510d99cf87..8a4ddc370280 100644
--- a/mypyc/primitives/generic_ops.py
+++ b/mypyc/primitives/generic_ops.py
@@ -26,6 +26,7 @@
     ERR_NEG_INT,
     binary_op,
     custom_op,
+    custom_primitive_op,
     function_op,
     method_op,
     unary_op,
@@ -307,6 +308,15 @@
     error_kind=ERR_MAGIC,
 )
 
+# Call callable object with positional args only: func(*args)
+# Arguments are (func, *args tuple).
+py_call_with_posargs_op = custom_op(
+    arg_types=[object_rprimitive, object_rprimitive],
+    return_type=object_rprimitive,
+    c_function_name="PyObject_CallObject",
+    error_kind=ERR_MAGIC,
+)
+
 # Call method with positional arguments: obj.method(arg1, ...)
 # Arguments are (object, attribute name, arg1, ...).
 py_method_call_op = custom_op(
@@ -382,3 +392,12 @@
     c_function_name="CPy_GetANext",
     error_kind=ERR_MAGIC,
 )
+
+# x.__name__ (requires Python 3.11+)
+name_op = custom_primitive_op(
+    name="__name__",
+    arg_types=[object_rprimitive],
+    return_type=object_rprimitive,
+    c_function_name="CPy_GetName",
+    error_kind=ERR_MAGIC,
+)
diff --git a/mypyc/primitives/int_ops.py b/mypyc/primitives/int_ops.py
index 9b8b48da602d..d723c9b63a86 100644
--- a/mypyc/primitives/int_ops.py
+++ b/mypyc/primitives/int_ops.py
@@ -296,3 +296,12 @@ def int_unary_op(name: str, c_function_name: str) -> PrimitiveDescription:
     c_function_name="CPyUInt8_Overflow",
     error_kind=ERR_ALWAYS,
 )
+
+# translate isinstance(obj, int)
+isinstance_int = function_op(
+    name="builtints.isinstance",
+    arg_types=[object_rprimitive],
+    return_type=bit_rprimitive,
+    c_function_name="PyLong_Check",
+    error_kind=ERR_NEVER,
+)
diff --git a/mypyc/primitives/list_ops.py b/mypyc/primitives/list_ops.py
index 99df6fe0dc9c..b9d20a25bea3 100644
--- a/mypyc/primitives/list_ops.py
+++ b/mypyc/primitives/list_ops.py
@@ -13,6 +13,7 @@
     object_rprimitive,
     pointer_rprimitive,
     short_int_rprimitive,
+    void_rtype,
 )
 from mypyc.primitives.registry import (
     ERR_NEG_INT,
@@ -55,6 +56,15 @@
     extra_int_constants=[(0, int_rprimitive)],
 )
 
+# translate isinstance(obj, list)
+isinstance_list = function_op(
+    name="builtins.isinstance",
+    arg_types=[object_rprimitive],
+    return_type=bit_rprimitive,
+    c_function_name="PyList_Check",
+    error_kind=ERR_NEVER,
+)
+
 new_list_op = custom_op(
     arg_types=[c_pyssize_t_rprimitive],
     return_type=list_rprimitive,
@@ -145,7 +155,7 @@
 # that is in-bounds for the list.
 list_get_item_unsafe_op = custom_primitive_op(
     name="list_get_item_unsafe",
-    arg_types=[list_rprimitive, short_int_rprimitive],
+    arg_types=[list_rprimitive, c_pyssize_t_rprimitive],
     return_type=object_rprimitive,
     error_kind=ERR_NEVER,
 )
@@ -174,10 +184,10 @@
 # PyList_SET_ITEM does no error checking,
 # and should only be used to fill in brand new lists.
 new_list_set_item_op = custom_op(
-    arg_types=[list_rprimitive, int_rprimitive, object_rprimitive],
-    return_type=bit_rprimitive,
+    arg_types=[list_rprimitive, c_pyssize_t_rprimitive, object_rprimitive],
+    return_type=void_rtype,
     c_function_name="CPyList_SetItemUnsafe",
-    error_kind=ERR_FALSE,
+    error_kind=ERR_NEVER,
     steals=[False, False, True],
 )
 
@@ -209,7 +219,7 @@
 )
 
 # list.pop(index)
-list_pop = method_op(
+method_op(
     name="pop",
     arg_types=[list_rprimitive, int_rprimitive],
     return_type=object_rprimitive,
@@ -271,6 +281,15 @@
     error_kind=ERR_MAGIC,
 )
 
+# list.clear()
+method_op(
+    name="clear",
+    arg_types=[list_rprimitive],
+    return_type=bit_rprimitive,
+    c_function_name="CPyList_Clear",
+    error_kind=ERR_FALSE,
+)
+
 # list.copy()
 method_op(
     name="copy",
diff --git a/mypyc/primitives/misc_ops.py b/mypyc/primitives/misc_ops.py
index 7494b46790ce..8e6e450c64dc 100644
--- a/mypyc/primitives/misc_ops.py
+++ b/mypyc/primitives/misc_ops.py
@@ -2,19 +2,25 @@
 
 from __future__ import annotations
 
-from mypyc.ir.ops import ERR_FALSE, ERR_MAGIC, ERR_NEVER
+from mypyc.ir.ops import ERR_FALSE, ERR_MAGIC, ERR_MAGIC_OVERLAPPING, ERR_NEVER
 from mypyc.ir.rtypes import (
+    KNOWN_NATIVE_TYPES,
     bit_rprimitive,
     bool_rprimitive,
+    bytes_rprimitive,
     c_int_rprimitive,
     c_pointer_rprimitive,
     c_pyssize_t_rprimitive,
+    cstring_rprimitive,
     dict_rprimitive,
+    float_rprimitive,
     int_rprimitive,
+    none_rprimitive,
     object_pointer_rprimitive,
     object_rprimitive,
     pointer_rprimitive,
     str_rprimitive,
+    uint8_rprimitive,
     void_rtype,
 )
 from mypyc.primitives.registry import (
@@ -23,6 +29,7 @@
     custom_primitive_op,
     function_op,
     load_address_op,
+    method_op,
 )
 
 # Get the 'bool' type object.
@@ -191,6 +198,15 @@
     truncated_type=bool_rprimitive,
 )
 
+# isinstance(obj, bool)
+isinstance_bool = function_op(
+    name="builtins.isinstance",
+    arg_types=[object_rprimitive],
+    return_type=bit_rprimitive,
+    c_function_name="PyBool_Check",
+    error_kind=ERR_NEVER,
+)
+
 # slice(start, stop, step)
 new_slice_op = function_op(
     name="builtins.slice",
@@ -204,7 +220,7 @@
 type_op = function_op(
     name="builtins.type",
     arg_types=[object_rprimitive],
-    c_function_name="PyObject_Type",
+    c_function_name="CPy_TYPE",
     return_type=object_rprimitive,
     error_kind=ERR_NEVER,
 )
@@ -291,3 +307,136 @@
     return_type=void_rtype,
     error_kind=ERR_NEVER,
 )
+
+# Log an event to a trace log, which is written to a file during execution.
+log_trace_event = custom_primitive_op(
+    name="log_trace_event",
+    c_function_name="CPyTrace_LogEvent",
+    # (fullname of function/location, line number, operation name, operation details)
+    arg_types=[cstring_rprimitive, cstring_rprimitive, cstring_rprimitive, cstring_rprimitive],
+    return_type=void_rtype,
+    error_kind=ERR_NEVER,
+)
+
+# Mark object as immortal -- it won't be freed via reference counting, as
+# the reference count won't be updated any longer. Immortal objects support
+# fast concurrent read-only access from multiple threads when using free
+# threading, since this eliminates contention from concurrent reference count
+# updates.
+#
+# Needs at least Python 3.14.
+set_immortal_op = custom_primitive_op(
+    name="set_immmortal",
+    c_function_name="CPy_SetImmortal",
+    arg_types=[object_rprimitive],
+    return_type=void_rtype,
+    error_kind=ERR_NEVER,
+)
+
+buffer_rprimitive = KNOWN_NATIVE_TYPES["native_internal.Buffer"]
+
+# Buffer(source)
+function_op(
+    name="native_internal.Buffer",
+    arg_types=[bytes_rprimitive],
+    return_type=buffer_rprimitive,
+    c_function_name="Buffer_internal",
+    error_kind=ERR_MAGIC,
+)
+
+# Buffer()
+function_op(
+    name="native_internal.Buffer",
+    arg_types=[],
+    return_type=buffer_rprimitive,
+    c_function_name="Buffer_internal_empty",
+    error_kind=ERR_MAGIC,
+)
+
+method_op(
+    name="getvalue",
+    arg_types=[buffer_rprimitive],
+    return_type=bytes_rprimitive,
+    c_function_name="Buffer_getvalue_internal",
+    error_kind=ERR_MAGIC,
+)
+
+function_op(
+    name="native_internal.write_bool",
+    arg_types=[object_rprimitive, bool_rprimitive],
+    return_type=none_rprimitive,
+    c_function_name="write_bool_internal",
+    error_kind=ERR_MAGIC,
+)
+
+function_op(
+    name="native_internal.read_bool",
+    arg_types=[object_rprimitive],
+    return_type=bool_rprimitive,
+    c_function_name="read_bool_internal",
+    error_kind=ERR_MAGIC,
+)
+
+function_op(
+    name="native_internal.write_str",
+    arg_types=[object_rprimitive, str_rprimitive],
+    return_type=none_rprimitive,
+    c_function_name="write_str_internal",
+    error_kind=ERR_MAGIC,
+)
+
+function_op(
+    name="native_internal.read_str",
+    arg_types=[object_rprimitive],
+    return_type=str_rprimitive,
+    c_function_name="read_str_internal",
+    error_kind=ERR_MAGIC,
+)
+
+function_op(
+    name="native_internal.write_float",
+    arg_types=[object_rprimitive, float_rprimitive],
+    return_type=none_rprimitive,
+    c_function_name="write_float_internal",
+    error_kind=ERR_MAGIC,
+)
+
+function_op(
+    name="native_internal.read_float",
+    arg_types=[object_rprimitive],
+    return_type=float_rprimitive,
+    c_function_name="read_float_internal",
+    error_kind=ERR_MAGIC,
+)
+
+function_op(
+    name="native_internal.write_int",
+    arg_types=[object_rprimitive, int_rprimitive],
+    return_type=none_rprimitive,
+    c_function_name="write_int_internal",
+    error_kind=ERR_MAGIC,
+)
+
+function_op(
+    name="native_internal.read_int",
+    arg_types=[object_rprimitive],
+    return_type=int_rprimitive,
+    c_function_name="read_int_internal",
+    error_kind=ERR_MAGIC,
+)
+
+function_op(
+    name="native_internal.write_tag",
+    arg_types=[object_rprimitive, uint8_rprimitive],
+    return_type=none_rprimitive,
+    c_function_name="write_tag_internal",
+    error_kind=ERR_MAGIC,
+)
+
+function_op(
+    name="native_internal.read_tag",
+    arg_types=[object_rprimitive],
+    return_type=uint8_rprimitive,
+    c_function_name="read_tag_internal",
+    error_kind=ERR_MAGIC_OVERLAPPING,
+)
diff --git a/mypyc/primitives/registry.py b/mypyc/primitives/registry.py
index 5e7ecb70f55d..07546663d08e 100644
--- a/mypyc/primitives/registry.py
+++ b/mypyc/primitives/registry.py
@@ -371,4 +371,5 @@ def load_address_op(name: str, type: RType, src: str) -> LoadAddressDescription:
 import mypyc.primitives.list_ops
 import mypyc.primitives.misc_ops
 import mypyc.primitives.str_ops
-import mypyc.primitives.tuple_ops  # noqa: F401
+import mypyc.primitives.tuple_ops
+import mypyc.primitives.weakref_ops  # noqa: F401
diff --git a/mypyc/primitives/set_ops.py b/mypyc/primitives/set_ops.py
index eb7c9b46609d..786de008746d 100644
--- a/mypyc/primitives/set_ops.py
+++ b/mypyc/primitives/set_ops.py
@@ -2,7 +2,7 @@
 
 from __future__ import annotations
 
-from mypyc.ir.ops import ERR_FALSE, ERR_MAGIC
+from mypyc.ir.ops import ERR_FALSE, ERR_MAGIC, ERR_NEVER
 from mypyc.ir.rtypes import (
     bit_rprimitive,
     bool_rprimitive,
@@ -64,6 +64,24 @@
     error_kind=ERR_MAGIC,
 )
 
+# translate isinstance(obj, set)
+isinstance_set = function_op(
+    name="builtins.isinstance",
+    arg_types=[object_rprimitive],
+    return_type=bit_rprimitive,
+    c_function_name="PySet_Check",
+    error_kind=ERR_NEVER,
+)
+
+# translate isinstance(obj, frozenset)
+isinstance_frozenset = function_op(
+    name="builtins.isinstance",
+    arg_types=[object_rprimitive],
+    return_type=bit_rprimitive,
+    c_function_name="PyFrozenSet_Check",
+    error_kind=ERR_NEVER,
+)
+
 # item in set
 set_in_op = binary_op(
     name="in",
diff --git a/mypyc/primitives/str_ops.py b/mypyc/primitives/str_ops.py
index ded339b9672c..a8f4e4df74c2 100644
--- a/mypyc/primitives/str_ops.py
+++ b/mypyc/primitives/str_ops.py
@@ -21,6 +21,7 @@
     ERR_NEG_INT,
     binary_op,
     custom_op,
+    custom_primitive_op,
     function_op,
     load_address_op,
     method_op,
@@ -47,6 +48,15 @@
     error_kind=ERR_MAGIC,
 )
 
+# translate isinstance(obj, str)
+isinstance_str = function_op(
+    name="builtins.isinstance",
+    arg_types=[object_rprimitive],
+    return_type=bit_rprimitive,
+    c_function_name="PyUnicode_Check",
+    error_kind=ERR_NEVER,
+)
+
 # str1 + str2
 binary_op(
     name="+",
@@ -69,6 +79,15 @@
     steals=[True, False],
 )
 
+# str1 == str2 (very common operation, so we provide our own)
+str_eq = custom_primitive_op(
+    name="str_eq",
+    c_function_name="CPyStr_Equal",
+    arg_types=[str_rprimitive, str_rprimitive],
+    return_type=bool_rprimitive,
+    error_kind=ERR_NEVER,
+)
+
 unicode_compare = custom_op(
     arg_types=[str_rprimitive, str_rprimitive],
     return_type=c_int_rprimitive,
@@ -85,6 +104,15 @@
     error_kind=ERR_MAGIC,
 )
 
+# This is unsafe since it assumes that the index is within reasonable bounds.
+# In the future this might do no bounds checking at all.
+str_get_item_unsafe_op = custom_op(
+    arg_types=[str_rprimitive, c_pyssize_t_rprimitive],
+    return_type=str_rprimitive,
+    c_function_name="CPyStr_GetItemUnsafe",
+    error_kind=ERR_MAGIC,
+)
+
 # str[begin:end]
 str_slice_op = custom_op(
     arg_types=[str_rprimitive, int_rprimitive, int_rprimitive],
@@ -277,6 +305,34 @@
     error_kind=ERR_MAGIC,
 )
 
+# str.count(substring)
+method_op(
+    name="count",
+    arg_types=[str_rprimitive, str_rprimitive],
+    return_type=c_pyssize_t_rprimitive,
+    c_function_name="CPyStr_Count",
+    error_kind=ERR_NEG_INT,
+    extra_int_constants=[(0, c_pyssize_t_rprimitive)],
+)
+
+# str.count(substring, start)
+method_op(
+    name="count",
+    arg_types=[str_rprimitive, str_rprimitive, int_rprimitive],
+    return_type=c_pyssize_t_rprimitive,
+    c_function_name="CPyStr_Count",
+    error_kind=ERR_NEG_INT,
+)
+
+# str.count(substring, start, end)
+method_op(
+    name="count",
+    arg_types=[str_rprimitive, str_rprimitive, int_rprimitive, int_rprimitive],
+    return_type=c_pyssize_t_rprimitive,
+    c_function_name="CPyStr_CountFull",
+    error_kind=ERR_NEG_INT,
+)
+
 # str.replace(old, new)
 method_op(
     name="replace",
@@ -331,7 +387,7 @@
     extra_int_constants=[(0, pointer_rprimitive)],
 )
 
-# obj.decode(encoding, errors)
+# bytes.decode(encoding, errors)
 method_op(
     name="decode",
     arg_types=[bytes_rprimitive, str_rprimitive, str_rprimitive],
@@ -340,6 +396,30 @@
     error_kind=ERR_MAGIC,
 )
 
+# bytes.decode(encoding) - utf8 strict specialization
+bytes_decode_utf8_strict = custom_op(
+    arg_types=[bytes_rprimitive],
+    return_type=str_rprimitive,
+    c_function_name="CPy_DecodeUTF8",
+    error_kind=ERR_MAGIC,
+)
+
+# bytes.decode(encoding) - ascii strict specialization
+bytes_decode_ascii_strict = custom_op(
+    arg_types=[bytes_rprimitive],
+    return_type=str_rprimitive,
+    c_function_name="CPy_DecodeASCII",
+    error_kind=ERR_MAGIC,
+)
+
+# bytes.decode(encoding) - latin1 strict specialization
+bytes_decode_latin1_strict = custom_op(
+    arg_types=[bytes_rprimitive],
+    return_type=str_rprimitive,
+    c_function_name="CPy_DecodeLatin1",
+    error_kind=ERR_MAGIC,
+)
+
 # str.encode()
 method_op(
     name="encode",
diff --git a/mypyc/primitives/tuple_ops.py b/mypyc/primitives/tuple_ops.py
index a9bbaa80fb5c..ab23f8c441f5 100644
--- a/mypyc/primitives/tuple_ops.py
+++ b/mypyc/primitives/tuple_ops.py
@@ -6,7 +6,7 @@
 
 from __future__ import annotations
 
-from mypyc.ir.ops import ERR_FALSE, ERR_MAGIC
+from mypyc.ir.ops import ERR_MAGIC, ERR_NEVER
 from mypyc.ir.rtypes import (
     bit_rprimitive,
     c_pyssize_t_rprimitive,
@@ -14,6 +14,7 @@
     list_rprimitive,
     object_rprimitive,
     tuple_rprimitive,
+    void_rtype,
 )
 from mypyc.primitives.registry import binary_op, custom_op, function_op, load_address_op, method_op
 
@@ -29,6 +30,15 @@
     error_kind=ERR_MAGIC,
 )
 
+# This is unsafe because it assumes that the index is a non-negative integer
+# that is in-bounds for the tuple.
+tuple_get_item_unsafe_op = custom_op(
+    arg_types=[tuple_rprimitive, c_pyssize_t_rprimitive],
+    return_type=object_rprimitive,
+    c_function_name="CPySequenceTuple_GetItemUnsafe",
+    error_kind=ERR_NEVER,
+)
+
 # Construct a boxed tuple from items: (item1, item2, ...)
 new_tuple_op = custom_op(
     arg_types=[c_pyssize_t_rprimitive],
@@ -45,13 +55,20 @@
     error_kind=ERR_MAGIC,
 )
 
+load_empty_tuple_constant_op = custom_op(
+    arg_types=[],
+    return_type=tuple_rprimitive,
+    c_function_name="CPyTuple_LoadEmptyTupleConstant",
+    error_kind=ERR_NEVER,
+)
+
 # PyTuple_SET_ITEM does no error checking,
 # and should only be used to fill in brand new tuples.
 new_tuple_set_item_op = custom_op(
-    arg_types=[tuple_rprimitive, int_rprimitive, object_rprimitive],
-    return_type=bit_rprimitive,
+    arg_types=[tuple_rprimitive, c_pyssize_t_rprimitive, object_rprimitive],
+    return_type=void_rtype,
     c_function_name="CPySequenceTuple_SetItemUnsafe",
-    error_kind=ERR_FALSE,
+    error_kind=ERR_NEVER,
     steals=[False, False, True],
 )
 
@@ -66,7 +83,7 @@
 )
 
 # Construct tuple from an arbitrary (iterable) object.
-function_op(
+sequence_tuple_op = function_op(
     name="builtins.tuple",
     arg_types=[object_rprimitive],
     return_type=tuple_rprimitive,
@@ -74,6 +91,15 @@
     error_kind=ERR_MAGIC,
 )
 
+# translate isinstance(obj, tuple)
+isinstance_tuple = function_op(
+    name="builtins.isinstance",
+    arg_types=[object_rprimitive],
+    return_type=bit_rprimitive,
+    c_function_name="PyTuple_Check",
+    error_kind=ERR_NEVER,
+)
+
 # tuple + tuple
 binary_op(
     name="+",
diff --git a/mypyc/primitives/weakref_ops.py b/mypyc/primitives/weakref_ops.py
new file mode 100644
index 000000000000..21379d3b2c82
--- /dev/null
+++ b/mypyc/primitives/weakref_ops.py
@@ -0,0 +1,40 @@
+from mypyc.ir.ops import ERR_MAGIC
+from mypyc.ir.rtypes import object_rprimitive, pointer_rprimitive
+from mypyc.primitives.registry import function_op
+
+# Weakref operations
+
+new_ref_op = function_op(
+    name="weakref.ReferenceType",
+    arg_types=[object_rprimitive],
+    return_type=object_rprimitive,
+    c_function_name="PyWeakref_NewRef",
+    extra_int_constants=[(0, pointer_rprimitive)],
+    error_kind=ERR_MAGIC,
+)
+
+new_ref__with_callback_op = function_op(
+    name="weakref.ReferenceType",
+    arg_types=[object_rprimitive, object_rprimitive],
+    return_type=object_rprimitive,
+    c_function_name="PyWeakref_NewRef",
+    error_kind=ERR_MAGIC,
+)
+
+new_proxy_op = function_op(
+    name="_weakref.proxy",
+    arg_types=[object_rprimitive],
+    return_type=object_rprimitive,
+    c_function_name="PyWeakref_NewProxy",
+    extra_int_constants=[(0, pointer_rprimitive)],
+    error_kind=ERR_MAGIC,
+)
+
+new_proxy_with_callback_op = function_op(
+    name="_weakref.proxy",
+    arg_types=[object_rprimitive, object_rprimitive],
+    # steals=[True, False],
+    return_type=object_rprimitive,
+    c_function_name="PyWeakref_NewProxy",
+    error_kind=ERR_MAGIC,
+)
diff --git a/mypyc/test-data/commandline.test b/mypyc/test-data/commandline.test
index 77c2e08bcf34..392ad3620790 100644
--- a/mypyc/test-data/commandline.test
+++ b/mypyc/test-data/commandline.test
@@ -101,13 +101,71 @@ assert a.f(10) == 100
 def f(x: int) -> int:
     return x*x
 
-[case testErrorOutput]
+[case testErrorOutput1]
+# cmd: test.py
+
+[file test.py]
+from functools import singledispatch
+from mypy_extensions import trait
+from typing import Any
+
+def decorator(x: Any) -> Any:
+    return x
+
+class NeverMetaclass(type):  # E: Inheriting from most builtin types is unimplemented \
+                             # N: Potential workaround: @mypy_extensions.mypyc_attr(native_class=False) \
+                             # N: https://mypyc.readthedocs.io/en/stable/native_classes.html#defining-non-native-classes
+    pass
+
+class Concrete1:
+    pass
+
+@trait
+class Trait1:
+    pass
+
+class Concrete2:
+    pass
+
+@decorator
+class NonExt(Concrete1):  # E: Non-extension classes may not inherit from extension classes
+    pass
+
+class NopeMultipleInheritanceAndBadOrder3(Trait1, Concrete1, Concrete2):  # E: Non-trait base must appear first in parent list
+    pass
+
+class NopeBadOrder(Trait1, Concrete2):  # E: Non-trait base must appear first in parent list
+    pass
+
+class Foo:
+    pass
+
+@singledispatch
+def a(arg) -> None:
+    pass
+
+@decorator # E: Calling decorator after registering function not supported
+@a.register
+def g(arg: int) -> None:
+    pass
+
+@a.register
+@decorator
+def h(arg: str) -> None:
+    pass
+
+@decorator
+@decorator # E: Calling decorator after registering function not supported
+@a.register
+def i(arg: Foo) -> None:
+    pass
+
+[case testErrorOutput2]
 # cmd: test.py
 
 [file test.py]
 from typing import Final, List, Any, AsyncIterable
 from mypy_extensions import trait, mypyc_attr
-from functools import singledispatch
 
 def busted(b: bool) -> None:
     for i in range(1, 10, 0):  # E: range() step can't be zero
@@ -138,11 +196,6 @@ Foo.lol = 50  # E: Only class variables defined as ClassVar can be assigned to
 def decorator(x: Any) -> Any:
     return x
 
-class NeverMetaclass(type):  # E: Inheriting from most builtin types is unimplemented \
-                             # N: Potential workaround: @mypy_extensions.mypyc_attr(native_class=False) \
-                             # N: https://mypyc.readthedocs.io/en/stable/native_classes.html#defining-non-native-classes
-    pass
-
 class Concrete1:
     pass
 
@@ -161,11 +214,6 @@ class Concrete2:
 class Trait2(Concrete2):
     pass
 
-@decorator
-class NonExt(Concrete1):  # E: Non-extension classes may not inherit from extension classes
-    pass
-
-
 class NopeMultipleInheritance(Concrete1, Concrete2):  # E: Multiple inheritance is not supported (except for traits)
     pass
 
@@ -175,13 +223,6 @@ class NopeMultipleInheritanceAndBadOrder(Concrete1, Trait1, Concrete2):  # E: Mu
 class NopeMultipleInheritanceAndBadOrder2(Concrete1, Concrete2, Trait1):  # E: Multiple inheritance is not supported (except for traits)
     pass
 
-class NopeMultipleInheritanceAndBadOrder3(Trait1, Concrete1, Concrete2):  # E: Non-trait base must appear first in parent list # E: Multiple inheritance is not supported (except for traits)
-    pass
-
-class NopeBadOrder(Trait1, Concrete2):  # E: Non-trait base must appear first in parent list
-    pass
-
-
 @decorator
 class NonExt2:
     @property  # E: Property setters not supported in non-extension classes
@@ -219,26 +260,6 @@ class AllowInterp2(PureTrait):  # E: Base class "test.PureTrait" does not allow
 async def async_generators() -> AsyncIterable[int]:
     yield 1  # E: async generators are unimplemented
 
-@singledispatch
-def a(arg) -> None:
-    pass
-
-@decorator # E: Calling decorator after registering function not supported
-@a.register
-def g(arg: int) -> None:
-    pass
-
-@a.register
-@decorator
-def h(arg: str) -> None:
-    pass
-
-@decorator
-@decorator # E: Calling decorator after registering function not supported
-@a.register
-def i(arg: Foo) -> None:
-    pass
-
 [case testOnlyWarningOutput]
 # cmd: test.py
 
diff --git a/mypyc/test-data/driver/driver.py b/mypyc/test-data/driver/driver.py
index c9d179224a30..395be6e1630e 100644
--- a/mypyc/test-data/driver/driver.py
+++ b/mypyc/test-data/driver/driver.py
@@ -9,14 +9,23 @@
 
 import sys
 import native
+import asyncio
+import inspect
+
+evloop = asyncio.new_event_loop()
 
 failures = []
+tests_run = 0
 
 for name in dir(native):
     if name.startswith('test_'):
         test_func = getattr(native, name)
+        tests_run += 1
         try:
-            test_func()
+            if inspect.iscoroutinefunction(test_func):
+                evloop.run_until_complete(test_func)
+            else:
+                test_func()
         except Exception as e:
             failures.append((name, sys.exc_info()))
 
@@ -46,3 +55,5 @@ def extract_line(tb):
     print(f'<< {failures[-1][0]} >>')
     sys.stdout.flush()
     raise failures[-1][1][1]
+
+assert tests_run > 0, 'Default test driver did not find any functions prefixed "test_" to run.'
diff --git a/mypyc/test-data/fixtures/ir.py b/mypyc/test-data/fixtures/ir.py
index 1b92590a5fd4..d3f7bc7ae4f6 100644
--- a/mypyc/test-data/fixtures/ir.py
+++ b/mypyc/test-data/fixtures/ir.py
@@ -3,7 +3,7 @@
 
 import _typeshed
 from typing import (
-    TypeVar, Generic, List, Iterator, Iterable, Dict, Optional, Tuple, Any, Set,
+    Self, TypeVar, Generic, List, Iterator, Iterable, Dict, Optional, Tuple, Any, Set,
     overload, Mapping, Union, Callable, Sequence, FrozenSet, Protocol
 )
 
@@ -39,9 +39,12 @@ def __pow__(self, other: T_contra, modulo: _M) -> T_co: ...
 ]
 
 class object:
+    __class__: type
+    def __new__(cls) -> Self: pass
     def __init__(self) -> None: pass
     def __eq__(self, x: object) -> bool: pass
     def __ne__(self, x: object) -> bool: pass
+    def __str__(self) -> str: pass
 
 class type:
     def __init__(self, o: object) -> None: ...
@@ -122,6 +125,7 @@ def rpartition(self, sep: str, /) -> Tuple[str, str, str]: ...
     def removeprefix(self, prefix: str, /) -> str: ...
     def removesuffix(self, suffix: str, /) -> str: ...
     def islower(self) -> bool: ...
+    def count(self, substr: str, start: Optional[int] = None, end: Optional[int] = None) -> int: pass
 
 class float:
     def __init__(self, x: object) -> None: pass
@@ -170,7 +174,8 @@ def __getitem__(self, i: int) -> int: ...
     @overload
     def __getitem__(self, i: slice) -> bytes: ...
     def join(self, x: Iterable[object]) -> bytes: ...
-    def decode(self, x: str=..., y: str=...) -> str: ...
+    def decode(self, encoding: str=..., errors: str=...) -> str: ...
+    def __iter__(self) -> Iterator[int]: ...
 
 class bytearray:
     @overload
@@ -245,6 +250,7 @@ def sort(self) -> None: pass
     def reverse(self) -> None: pass
     def remove(self, o: _T) -> None: pass
     def index(self, o: _T) -> int: pass
+    def clear(self) -> None: pass
     def copy(self) -> List[_T]: pass
 
 class dict(Mapping[_K, _V]):
@@ -337,6 +343,7 @@ class RuntimeError(Exception): pass
 class UnicodeEncodeError(RuntimeError): pass
 class UnicodeDecodeError(RuntimeError): pass
 class NotImplementedError(RuntimeError): pass
+class ReferenceError(Exception): pass
 
 class StopIteration(Exception):
     value: Any
@@ -349,7 +356,12 @@ class GeneratorExit(BaseException): pass
 
 def any(i: Iterable[_T]) -> bool: pass
 def all(i: Iterable[_T]) -> bool: pass
-def sum(i: Iterable[_T]) -> int: pass
+@overload
+def sum(i: Iterable[bool]) -> int: pass
+@overload
+def sum(i: Iterable[_T]) -> _T: pass
+@overload
+def sum(i: Iterable[_T], start: _T) -> _T: pass
 def reversed(object: Sequence[_T]) -> Iterator[_T]: ...
 def id(o: object) -> int: pass
 # This type is obviously wrong but the test stubs don't have Sized anymore
diff --git a/mypyc/test-data/fixtures/typing-full.pyi b/mypyc/test-data/fixtures/typing-full.pyi
index d37129bc2e0b..8d89e4f93bc9 100644
--- a/mypyc/test-data/fixtures/typing-full.pyi
+++ b/mypyc/test-data/fixtures/typing-full.pyi
@@ -32,6 +32,7 @@ Final = 0
 TypedDict = 0
 NoReturn = 0
 NewType = 0
+Self = 0
 Callable: _SpecialForm
 Union: _SpecialForm
 Literal: _SpecialForm
diff --git a/mypyc/test-data/irbuild-basic.test b/mypyc/test-data/irbuild-basic.test
index 6e5267fc34dd..612f3266fd79 100644
--- a/mypyc/test-data/irbuild-basic.test
+++ b/mypyc/test-data/irbuild-basic.test
@@ -1581,24 +1581,18 @@ def main() -> None:
 [out]
 def foo(x):
     x :: union[int, str]
-    r0 :: object
-    r1 :: i32
-    r2 :: bit
-    r3 :: bool
-    r4 :: __main__.B
-    r5 :: __main__.A
+    r0 :: bit
+    r1 :: __main__.B
+    r2 :: __main__.A
 L0:
-    r0 = load_address PyLong_Type
-    r1 = PyObject_IsInstance(x, r0)
-    r2 = r1 >= 0 :: signed
-    r3 = truncate r1: i32 to builtins.bool
-    if r3 goto L1 else goto L2 :: bool
+    r0 = PyLong_Check(x)
+    if r0 goto L1 else goto L2 :: bool
 L1:
-    r4 = B()
-    return r4
+    r1 = B()
+    return r1
 L2:
-    r5 = A()
-    return r5
+    r2 = A()
+    return r2
 def main():
     r0 :: object
     r1 :: __main__.A
@@ -1680,26 +1674,17 @@ def g():
     r0 :: tuple[int, int, int]
     r1 :: dict
     r2 :: str
-    r3 :: object
-    r4 :: list
-    r5, r6 :: object
-    r7 :: tuple
-    r8 :: dict
-    r9 :: object
-    r10 :: tuple[int, int, int]
+    r3, r4, r5 :: object
+    r6 :: tuple[int, int, int]
 L0:
     r0 = (2, 4, 6)
     r1 = __main__.globals :: static
     r2 = 'f'
     r3 = CPyDict_GetItem(r1, r2)
-    r4 = PyList_New(0)
-    r5 = box(tuple[int, int, int], r0)
-    r6 = CPyList_Extend(r4, r5)
-    r7 = PyList_AsTuple(r4)
-    r8 = PyDict_New()
-    r9 = PyObject_Call(r3, r7, r8)
-    r10 = unbox(tuple[int, int, int], r9)
-    return r10
+    r4 = box(tuple[int, int, int], r0)
+    r5 = PyObject_CallObject(r3, r4)
+    r6 = unbox(tuple[int, int, int], r5)
+    return r6
 def h():
     r0 :: tuple[int, int]
     r1 :: dict
@@ -1710,9 +1695,8 @@ def h():
     r6 :: ptr
     r7, r8 :: object
     r9 :: tuple
-    r10 :: dict
-    r11 :: object
-    r12 :: tuple[int, int, int]
+    r10 :: object
+    r11 :: tuple[int, int, int]
 L0:
     r0 = (4, 6)
     r1 = __main__.globals :: static
@@ -1726,10 +1710,9 @@ L0:
     r7 = box(tuple[int, int], r0)
     r8 = CPyList_Extend(r4, r7)
     r9 = PyList_AsTuple(r4)
-    r10 = PyDict_New()
-    r11 = PyObject_Call(r3, r9, r10)
-    r12 = unbox(tuple[int, int, int], r11)
-    return r12
+    r10 = PyObject_CallObject(r3, r9)
+    r11 = unbox(tuple[int, int, int], r10)
+    return r11
 
 [case testStar2Args]
 from typing import Tuple
@@ -1752,12 +1735,10 @@ def g():
     r6, r7 :: dict
     r8 :: str
     r9 :: object
-    r10 :: dict
-    r11 :: i32
-    r12 :: bit
-    r13 :: tuple
-    r14 :: object
-    r15 :: tuple[int, int, int]
+    r10 :: tuple
+    r11 :: dict
+    r12 :: object
+    r13 :: tuple[int, int, int]
 L0:
     r0 = 'a'
     r1 = 'b'
@@ -1769,13 +1750,11 @@ L0:
     r7 = __main__.globals :: static
     r8 = 'f'
     r9 = CPyDict_GetItem(r7, r8)
-    r10 = PyDict_New()
-    r11 = CPyDict_UpdateInDisplay(r10, r6)
-    r12 = r11 >= 0 :: signed
-    r13 = PyTuple_Pack(0)
-    r14 = PyObject_Call(r9, r13, r10)
-    r15 = unbox(tuple[int, int, int], r14)
-    return r15
+    r10 = CPyTuple_LoadEmptyTupleConstant()
+    r11 = PyDict_Copy(r6)
+    r12 = PyObject_Call(r9, r10, r11)
+    r13 = unbox(tuple[int, int, int], r12)
+    return r13
 def h():
     r0, r1 :: str
     r2, r3 :: object
@@ -1895,18 +1874,16 @@ def f():
     r0, r1 :: list
     r2, r3, r4 :: object
     r5 :: ptr
-    r6 :: short_int
-    r7 :: native_int
-    r8 :: short_int
-    r9 :: bit
-    r10 :: object
-    r11, x :: int
-    r12, r13 :: bit
-    r14 :: int
-    r15 :: object
-    r16 :: i32
-    r17 :: bit
-    r18 :: short_int
+    r6, r7 :: native_int
+    r8 :: bit
+    r9 :: object
+    r10, x :: int
+    r11, r12 :: bit
+    r13 :: int
+    r14 :: object
+    r15 :: i32
+    r16 :: bit
+    r17 :: native_int
 L0:
     r0 = PyList_New(0)
     r1 = PyList_New(3)
@@ -1921,30 +1898,29 @@ L0:
     r6 = 0
 L1:
     r7 = var_object_size r1
-    r8 = r7 << 1
-    r9 = int_lt r6, r8
-    if r9 goto L2 else goto L8 :: bool
+    r8 = r6 < r7 :: signed
+    if r8 goto L2 else goto L8 :: bool
 L2:
-    r10 = list_get_item_unsafe r1, r6
-    r11 = unbox(int, r10)
-    x = r11
-    r12 = int_ne x, 4
-    if r12 goto L4 else goto L3 :: bool
+    r9 = list_get_item_unsafe r1, r6
+    r10 = unbox(int, r9)
+    x = r10
+    r11 = int_ne x, 4
+    if r11 goto L4 else goto L3 :: bool
 L3:
     goto L7
 L4:
-    r13 = int_ne x, 6
-    if r13 goto L6 else goto L5 :: bool
+    r12 = int_ne x, 6
+    if r12 goto L6 else goto L5 :: bool
 L5:
     goto L7
 L6:
-    r14 = CPyTagged_Multiply(x, x)
-    r15 = box(int, r14)
-    r16 = PyList_Append(r0, r15)
-    r17 = r16 >= 0 :: signed
+    r13 = CPyTagged_Multiply(x, x)
+    r14 = box(int, r13)
+    r15 = PyList_Append(r0, r14)
+    r16 = r15 >= 0 :: signed
 L7:
-    r18 = r6 + 2
-    r6 = r18
+    r17 = r6 + 1
+    r6 = r17
     goto L1
 L8:
     return r0
@@ -1959,18 +1935,16 @@ def f():
     r1 :: list
     r2, r3, r4 :: object
     r5 :: ptr
-    r6 :: short_int
-    r7 :: native_int
-    r8 :: short_int
-    r9 :: bit
-    r10 :: object
-    r11, x :: int
-    r12, r13 :: bit
-    r14 :: int
-    r15, r16 :: object
-    r17 :: i32
-    r18 :: bit
-    r19 :: short_int
+    r6, r7 :: native_int
+    r8 :: bit
+    r9 :: object
+    r10, x :: int
+    r11, r12 :: bit
+    r13 :: int
+    r14, r15 :: object
+    r16 :: i32
+    r17 :: bit
+    r18 :: native_int
 L0:
     r0 = PyDict_New()
     r1 = PyList_New(3)
@@ -1985,31 +1959,30 @@ L0:
     r6 = 0
 L1:
     r7 = var_object_size r1
-    r8 = r7 << 1
-    r9 = int_lt r6, r8
-    if r9 goto L2 else goto L8 :: bool
+    r8 = r6 < r7 :: signed
+    if r8 goto L2 else goto L8 :: bool
 L2:
-    r10 = list_get_item_unsafe r1, r6
-    r11 = unbox(int, r10)
-    x = r11
-    r12 = int_ne x, 4
-    if r12 goto L4 else goto L3 :: bool
+    r9 = list_get_item_unsafe r1, r6
+    r10 = unbox(int, r9)
+    x = r10
+    r11 = int_ne x, 4
+    if r11 goto L4 else goto L3 :: bool
 L3:
     goto L7
 L4:
-    r13 = int_ne x, 6
-    if r13 goto L6 else goto L5 :: bool
+    r12 = int_ne x, 6
+    if r12 goto L6 else goto L5 :: bool
 L5:
     goto L7
 L6:
-    r14 = CPyTagged_Multiply(x, x)
-    r15 = box(int, x)
-    r16 = box(int, r14)
-    r17 = CPyDict_SetItem(r0, r15, r16)
-    r18 = r17 >= 0 :: signed
+    r13 = CPyTagged_Multiply(x, x)
+    r14 = box(int, x)
+    r15 = box(int, r13)
+    r16 = PyDict_SetItem(r0, r14, r15)
+    r17 = r16 >= 0 :: signed
 L7:
-    r19 = r6 + 2
-    r6 = r19
+    r18 = r6 + 1
+    r6 = r18
     goto L1
 L8:
     return r0
@@ -2023,74 +1996,66 @@ def f(l: List[Tuple[int, int, int]]) -> List[int]:
 [out]
 def f(l):
     l :: list
-    r0 :: short_int
-    r1 :: native_int
-    r2 :: short_int
-    r3 :: bit
-    r4 :: object
-    r5 :: tuple[int, int, int]
-    r6, x, r7, y, r8, z :: int
-    r9 :: short_int
-    r10 :: native_int
-    r11 :: list
-    r12 :: short_int
-    r13 :: native_int
-    r14 :: short_int
-    r15 :: bit
-    r16 :: object
-    r17 :: tuple[int, int, int]
-    r18, x_2, r19, y_2, r20, z_2, r21, r22 :: int
-    r23 :: object
-    r24 :: bit
-    r25 :: short_int
+    r0, r1 :: native_int
+    r2 :: bit
+    r3 :: object
+    r4 :: tuple[int, int, int]
+    r5, x, r6, y, r7, z :: int
+    r8, r9 :: native_int
+    r10 :: list
+    r11, r12 :: native_int
+    r13 :: bit
+    r14 :: object
+    r15 :: tuple[int, int, int]
+    r16, x_2, r17, y_2, r18, z_2, r19, r20 :: int
+    r21 :: object
+    r22 :: native_int
 L0:
     r0 = 0
 L1:
     r1 = var_object_size l
-    r2 = r1 << 1
-    r3 = int_lt r0, r2
-    if r3 goto L2 else goto L4 :: bool
+    r2 = r0 < r1 :: signed
+    if r2 goto L2 else goto L4 :: bool
 L2:
-    r4 = list_get_item_unsafe l, r0
-    r5 = unbox(tuple[int, int, int], r4)
-    r6 = r5[0]
-    x = r6
-    r7 = r5[1]
-    y = r7
-    r8 = r5[2]
-    z = r8
+    r3 = list_get_item_unsafe l, r0
+    r4 = unbox(tuple[int, int, int], r3)
+    r5 = r4[0]
+    x = r5
+    r6 = r4[1]
+    y = r6
+    r7 = r4[2]
+    z = r7
 L3:
-    r9 = r0 + 2
-    r0 = r9
+    r8 = r0 + 1
+    r0 = r8
     goto L1
 L4:
-    r10 = var_object_size l
-    r11 = PyList_New(r10)
-    r12 = 0
+    r9 = var_object_size l
+    r10 = PyList_New(r9)
+    r11 = 0
 L5:
-    r13 = var_object_size l
-    r14 = r13 << 1
-    r15 = int_lt r12, r14
-    if r15 goto L6 else goto L8 :: bool
+    r12 = var_object_size l
+    r13 = r11 < r12 :: signed
+    if r13 goto L6 else goto L8 :: bool
 L6:
-    r16 = list_get_item_unsafe l, r12
-    r17 = unbox(tuple[int, int, int], r16)
-    r18 = r17[0]
-    x_2 = r18
-    r19 = r17[1]
-    y_2 = r19
-    r20 = r17[2]
-    z_2 = r20
-    r21 = CPyTagged_Add(x_2, y_2)
-    r22 = CPyTagged_Add(r21, z_2)
-    r23 = box(int, r22)
-    r24 = CPyList_SetItemUnsafe(r11, r12, r23)
+    r14 = list_get_item_unsafe l, r11
+    r15 = unbox(tuple[int, int, int], r14)
+    r16 = r15[0]
+    x_2 = r16
+    r17 = r15[1]
+    y_2 = r17
+    r18 = r15[2]
+    z_2 = r18
+    r19 = CPyTagged_Add(x_2, y_2)
+    r20 = CPyTagged_Add(r19, z_2)
+    r21 = box(int, r20)
+    CPyList_SetItemUnsafe(r10, r11, r21)
 L7:
-    r25 = r12 + 2
-    r12 = r25
+    r22 = r11 + 1
+    r11 = r22
     goto L5
 L8:
-    return r11
+    return r10
 
 [case testProperty]
 class PropertyHolder:
@@ -2382,22 +2347,42 @@ def A.__ne__(__mypyc_self__, rhs):
     __mypyc_self__ :: __main__.A
     rhs, r0, r1 :: object
     r2 :: bit
-    r3 :: i32
-    r4 :: bit
-    r5 :: bool
+    r3 :: object
+    r4, r5 :: bit
     r6 :: object
+    r7 :: bit
+    r8 :: i32
+    r9 :: bit
+    r10 :: bool
+    r11 :: object
 L0:
     r0 = __mypyc_self__.__eq__(rhs)
     r1 = load_address _Py_NotImplementedStruct
     r2 = r0 == r1
-    if r2 goto L2 else goto L1 :: bool
+    if r2 goto L7 else goto L1 :: bool
 L1:
-    r3 = PyObject_Not(r0)
-    r4 = r3 >= 0 :: signed
-    r5 = truncate r3: i32 to builtins.bool
-    r6 = box(bool, r5)
-    return r6
+    r3 = load_global Py_True :: static
+    r4 = r0 == r3
+    if r4 goto L2 else goto L3 :: bool
 L2:
+    r5 = 0
+    goto L6
+L3:
+    r6 = load_global Py_False :: static
+    r7 = r0 == r6
+    if r7 goto L4 else goto L5 :: bool
+L4:
+    r5 = 1
+    goto L6
+L5:
+    r8 = PyObject_Not(r0)
+    r9 = r8 >= 0 :: signed
+    r10 = truncate r8: i32 to builtins.bool
+    r5 = r10
+L6:
+    r11 = box(bit, r5)
+    return r11
+L7:
     return r1
 
 [case testDecorators_toplevel]
@@ -2640,7 +2625,7 @@ L0:
     d = r14
     r15 = __main__.globals :: static
     r16 = 'd'
-    r17 = CPyDict_SetItem(r15, r16, r14)
+    r17 = PyDict_SetItem(r15, r16, r14)
     r18 = r17 >= 0 :: signed
     r19 = 'c'
     r20 = builtins :: module
@@ -2713,7 +2698,7 @@ L2:
     keep_alive r17
     r24 = __main__.globals :: static
     r25 = 'c'
-    r26 = CPyDict_SetItem(r24, r25, r23)
+    r26 = PyDict_SetItem(r24, r25, r23)
     r27 = r26 >= 0 :: signed
     return 1
 
@@ -3403,16 +3388,11 @@ def f(x: object) -> bool:
     return isinstance(x, bool)
 [out]
 def f(x):
-    x, r0 :: object
-    r1 :: i32
-    r2 :: bit
-    r3 :: bool
+    x :: object
+    r0 :: bit
 L0:
-    r0 = load_address PyBool_Type
-    r1 = PyObject_IsInstance(x, r0)
-    r2 = r1 >= 0 :: signed
-    r3 = truncate r1: i32 to builtins.bool
-    return r3
+    r0 = PyBool_Check(x)
+    return r0
 
 [case testRangeObject]
 def range_object() -> None:
@@ -3556,3 +3536,266 @@ L3:
     s = arg
     r3 = CPyObject_Size(s)
     return r3
+
+[case testUndefinedFunction]
+def f():
+    non_existent_function()
+
+[out]
+def f():
+    r0 :: bool
+    r1, r2, r3 :: object
+L0:
+    r0 = raise NameError('name "non_existent_function" is not defined')
+    r1 = box(None, 1)
+    r2 = PyObject_Vectorcall(r1, 0, 0, 0)
+    r3 = box(None, 1)
+    return r3
+
+[case testStarArgFastPathTuple]
+from typing import Any, Callable
+def deco(fn: Callable[..., Any]) -> Callable[..., Any]:
+    def wrapper(*args: Any) -> Any:
+        return fn(*args)
+    return wrapper
+
+[out]
+def wrapper_deco_obj.__get__(__mypyc_self__, instance, owner):
+    __mypyc_self__, instance, owner, r0 :: object
+    r1 :: bit
+    r2 :: object
+L0:
+    r0 = load_address _Py_NoneStruct
+    r1 = instance == r0
+    if r1 goto L1 else goto L2 :: bool
+L1:
+    return __mypyc_self__
+L2:
+    r2 = PyMethod_New(__mypyc_self__, instance)
+    return r2
+def wrapper_deco_obj.__call__(__mypyc_self__, args):
+    __mypyc_self__ :: __main__.wrapper_deco_obj
+    args :: tuple
+    r0 :: __main__.deco_env
+    r1, r2 :: object
+L0:
+    r0 = __mypyc_self__.__mypyc_env__
+    r1 = r0.fn
+    r2 = PyObject_CallObject(r1, args)
+    return r2
+def deco(fn):
+    fn :: object
+    r0 :: __main__.deco_env
+    r1 :: bool
+    r2 :: __main__.wrapper_deco_obj
+    r3 :: bool
+    wrapper :: object
+L0:
+    r0 = deco_env()
+    r0.fn = fn; r1 = is_error
+    r2 = wrapper_deco_obj()
+    r2.__mypyc_env__ = r0; r3 = is_error
+    wrapper = r2
+    return wrapper
+
+[case testStarArgFastPathList]
+from typing import Any, Callable
+def deco(fn: Callable[..., Any]) -> Callable[[list[Any]], Any]:
+    def wrapper(args: list[Any]) -> Any:
+        return fn(*args)
+    return wrapper
+
+[out]
+def wrapper_deco_obj.__get__(__mypyc_self__, instance, owner):
+    __mypyc_self__, instance, owner, r0 :: object
+    r1 :: bit
+    r2 :: object
+L0:
+    r0 = load_address _Py_NoneStruct
+    r1 = instance == r0
+    if r1 goto L1 else goto L2 :: bool
+L1:
+    return __mypyc_self__
+L2:
+    r2 = PyMethod_New(__mypyc_self__, instance)
+    return r2
+def wrapper_deco_obj.__call__(__mypyc_self__, args):
+    __mypyc_self__ :: __main__.wrapper_deco_obj
+    args :: list
+    r0 :: __main__.deco_env
+    r1 :: object
+    r2 :: tuple
+    r3 :: object
+L0:
+    r0 = __mypyc_self__.__mypyc_env__
+    r1 = r0.fn
+    r2 = PyList_AsTuple(args)
+    r3 = PyObject_CallObject(r1, r2)
+    return r3
+def deco(fn):
+    fn :: object
+    r0 :: __main__.deco_env
+    r1 :: bool
+    r2 :: __main__.wrapper_deco_obj
+    r3 :: bool
+    wrapper :: object
+L0:
+    r0 = deco_env()
+    r0.fn = fn; r1 = is_error
+    r2 = wrapper_deco_obj()
+    r2.__mypyc_env__ = r0; r3 = is_error
+    wrapper = r2
+    return wrapper
+
+[case testStarArgFastPathListWithKwargs]
+from typing import Any, Callable
+def deco(fn: Callable[..., Any]) -> Callable[..., Any]:
+    def wrapper(lst: list[Any], kwargs: dict[str, Any]) -> Any:
+        return fn(*lst, **kwargs)
+    return wrapper
+
+[out]
+def wrapper_deco_obj.__get__(__mypyc_self__, instance, owner):
+    __mypyc_self__, instance, owner, r0 :: object
+    r1 :: bit
+    r2 :: object
+L0:
+    r0 = load_address _Py_NoneStruct
+    r1 = instance == r0
+    if r1 goto L1 else goto L2 :: bool
+L1:
+    return __mypyc_self__
+L2:
+    r2 = PyMethod_New(__mypyc_self__, instance)
+    return r2
+def wrapper_deco_obj.__call__(__mypyc_self__, lst, kwargs):
+    __mypyc_self__ :: __main__.wrapper_deco_obj
+    lst :: list
+    kwargs :: dict
+    r0 :: __main__.deco_env
+    r1 :: object
+    r2 :: tuple
+    r3 :: dict
+    r4 :: object
+L0:
+    r0 = __mypyc_self__.__mypyc_env__
+    r1 = r0.fn
+    r2 = PyList_AsTuple(lst)
+    r3 = PyDict_Copy(kwargs)
+    r4 = PyObject_Call(r1, r2, r3)
+    return r4
+def deco(fn):
+    fn :: object
+    r0 :: __main__.deco_env
+    r1 :: bool
+    r2 :: __main__.wrapper_deco_obj
+    r3 :: bool
+    wrapper :: object
+L0:
+    r0 = deco_env()
+    r0.fn = fn; r1 = is_error
+    r2 = wrapper_deco_obj()
+    r2.__mypyc_env__ = r0; r3 = is_error
+    wrapper = r2
+    return wrapper
+
+[case testStarArgFastPathSequence]
+from typing import Any, Callable
+def deco(fn: Callable[[Any], Any]) -> Callable[[Any], Any]:
+    def wrapper(args: Any) -> Any:
+        return fn(*args)
+    return wrapper
+
+[out]
+def wrapper_deco_obj.__get__(__mypyc_self__, instance, owner):
+    __mypyc_self__, instance, owner, r0 :: object
+    r1 :: bit
+    r2 :: object
+L0:
+    r0 = load_address _Py_NoneStruct
+    r1 = instance == r0
+    if r1 goto L1 else goto L2 :: bool
+L1:
+    return __mypyc_self__
+L2:
+    r2 = PyMethod_New(__mypyc_self__, instance)
+    return r2
+def wrapper_deco_obj.__call__(__mypyc_self__, args):
+    __mypyc_self__ :: __main__.wrapper_deco_obj
+    args :: object
+    r0 :: __main__.deco_env
+    r1 :: object
+    r2 :: tuple
+    r3 :: object
+L0:
+    r0 = __mypyc_self__.__mypyc_env__
+    r1 = r0.fn
+    r2 = PySequence_Tuple(args)
+    r3 = PyObject_CallObject(r1, r2)
+    return r3
+def deco(fn):
+    fn :: object
+    r0 :: __main__.deco_env
+    r1 :: bool
+    r2 :: __main__.wrapper_deco_obj
+    r3 :: bool
+    wrapper :: object
+L0:
+    r0 = deco_env()
+    r0.fn = fn; r1 = is_error
+    r2 = wrapper_deco_obj()
+    r2.__mypyc_env__ = r0; r3 = is_error
+    wrapper = r2
+    return wrapper
+
+[case testStarArgFastPathSequenceWithKwargs]
+from typing import Any, Callable
+def deco(fn: Callable[[Any], Any]) -> Callable[[Any], Any]:
+    def wrapper(args: Any, **kwargs: Any) -> Any:
+        return fn(*args, **kwargs)
+    return wrapper
+
+[out]
+def wrapper_deco_obj.__get__(__mypyc_self__, instance, owner):
+    __mypyc_self__, instance, owner, r0 :: object
+    r1 :: bit
+    r2 :: object
+L0:
+    r0 = load_address _Py_NoneStruct
+    r1 = instance == r0
+    if r1 goto L1 else goto L2 :: bool
+L1:
+    return __mypyc_self__
+L2:
+    r2 = PyMethod_New(__mypyc_self__, instance)
+    return r2
+def wrapper_deco_obj.__call__(__mypyc_self__, args, kwargs):
+    __mypyc_self__ :: __main__.wrapper_deco_obj
+    args :: object
+    kwargs :: dict
+    r0 :: __main__.deco_env
+    r1 :: object
+    r2 :: tuple
+    r3 :: dict
+    r4 :: object
+L0:
+    r0 = __mypyc_self__.__mypyc_env__
+    r1 = r0.fn
+    r2 = PySequence_Tuple(args)
+    r3 = PyDict_Copy(kwargs)
+    r4 = PyObject_Call(r1, r2, r3)
+    return r4
+def deco(fn):
+    fn :: object
+    r0 :: __main__.deco_env
+    r1 :: bool
+    r2 :: __main__.wrapper_deco_obj
+    r3 :: bool
+    wrapper :: object
+L0:
+    r0 = deco_env()
+    r0.fn = fn; r1 = is_error
+    r2 = wrapper_deco_obj()
+    r2.__mypyc_env__ = r0; r3 = is_error
+    wrapper = r2
+    return wrapper
diff --git a/mypyc/test-data/irbuild-bool.test b/mypyc/test-data/irbuild-bool.test
index 128266e6b1d7..9810daf487fa 100644
--- a/mypyc/test-data/irbuild-bool.test
+++ b/mypyc/test-data/irbuild-bool.test
@@ -422,3 +422,54 @@ L0:
     r1 = extend r0: builtins.bool to builtins.int
     x = r1
     return x
+
+[case testBitToBoolPromotion]
+def bitand(x: float, y: float, z: float) -> bool:
+    b = (x == y) & (x == z)
+    return b
+def bitor(x: float, y: float, z: float) -> bool:
+    b = (x == y) | (x == z)
+    return b
+def bitxor(x: float, y: float, z: float) -> bool:
+    b = (x == y) ^ (x == z)
+    return b
+def invert(x: float, y: float) -> bool:
+    return not(x == y)
+[out]
+def bitand(x, y, z):
+    x, y, z :: float
+    r0, r1 :: bit
+    r2, b :: bool
+L0:
+    r0 = x == y
+    r1 = x == z
+    r2 = r0 & r1
+    b = r2
+    return b
+def bitor(x, y, z):
+    x, y, z :: float
+    r0, r1 :: bit
+    r2, b :: bool
+L0:
+    r0 = x == y
+    r1 = x == z
+    r2 = r0 | r1
+    b = r2
+    return b
+def bitxor(x, y, z):
+    x, y, z :: float
+    r0, r1 :: bit
+    r2, b :: bool
+L0:
+    r0 = x == y
+    r1 = x == z
+    r2 = r0 ^ r1
+    b = r2
+    return b
+def invert(x, y):
+    x, y :: float
+    r0, r1 :: bit
+L0:
+    r0 = x == y
+    r1 = r0 ^ 1
+    return r1
diff --git a/mypyc/test-data/irbuild-bytes.test b/mypyc/test-data/irbuild-bytes.test
index 476c5ac59f48..8cfefe03ae22 100644
--- a/mypyc/test-data/irbuild-bytes.test
+++ b/mypyc/test-data/irbuild-bytes.test
@@ -185,3 +185,35 @@ L0:
     r10 = CPyBytes_Build(2, var, r9)
     b4 = r10
     return 1
+
+[case testOptionalBytesEquality]
+from typing import Optional
+
+def non_opt_opt(x: bytes, y: Optional[bytes]) -> bool:
+    return x != y
+[out]
+def non_opt_opt(x, y):
+    x :: bytes
+    y :: union[bytes, None]
+    r0 :: object
+    r1 :: bit
+    r2 :: bool
+    r3 :: bytes
+    r4 :: i32
+    r5, r6 :: bit
+L0:
+    r0 = load_address _Py_NoneStruct
+    r1 = y == r0
+    if r1 goto L1 else goto L2 :: bool
+L1:
+    r2 = 1
+    goto L3
+L2:
+    r3 = unchecked borrow cast(bytes, y)
+    r4 = CPyBytes_Compare(r3, x)
+    r5 = r4 >= 0 :: signed
+    r6 = r4 != 1
+    r2 = r6
+L3:
+    keep_alive y
+    return r2
diff --git a/mypyc/test-data/irbuild-classes.test b/mypyc/test-data/irbuild-classes.test
index fa4708f02e0b..bb55958dc6dc 100644
--- a/mypyc/test-data/irbuild-classes.test
+++ b/mypyc/test-data/irbuild-classes.test
@@ -180,7 +180,7 @@ L0:
     o.x = r1; r2 = is_error
     return o
 
-[case testSubclass_toplevel]
+[case testSubclass_withgil_toplevel]
 from typing import TypeVar, Generic
 from mypy_extensions import trait
 T = TypeVar('T')
@@ -297,26 +297,26 @@ L2:
     r27 = CPyType_FromTemplate(r26, r24, r25)
     r28 = C_trait_vtable_setup()
     r29 = '__mypyc_attrs__'
-    r30 = PyTuple_Pack(0)
+    r30 = CPyTuple_LoadEmptyTupleConstant()
     r31 = PyObject_SetAttr(r27, r29, r30)
     r32 = r31 >= 0 :: signed
     __main__.C = r27 :: type
     r33 = __main__.globals :: static
     r34 = 'C'
-    r35 = CPyDict_SetItem(r33, r34, r27)
+    r35 = PyDict_SetItem(r33, r34, r27)
     r36 = r35 >= 0 :: signed
     r37 = <error> :: object
     r38 = '__main__'
     r39 = __main__.S_template :: type
     r40 = CPyType_FromTemplate(r39, r37, r38)
     r41 = '__mypyc_attrs__'
-    r42 = PyTuple_Pack(0)
+    r42 = CPyTuple_LoadEmptyTupleConstant()
     r43 = PyObject_SetAttr(r40, r41, r42)
     r44 = r43 >= 0 :: signed
     __main__.S = r40 :: type
     r45 = __main__.globals :: static
     r46 = 'S'
-    r47 = CPyDict_SetItem(r45, r46, r40)
+    r47 = PyDict_SetItem(r45, r46, r40)
     r48 = r47 >= 0 :: signed
     r49 = __main__.C :: type
     r50 = __main__.S :: type
@@ -340,7 +340,7 @@ L2:
     __main__.D = r61 :: type
     r68 = __main__.globals :: static
     r69 = 'D'
-    r70 = CPyDict_SetItem(r68, r69, r61)
+    r70 = PyDict_SetItem(r68, r69, r61)
     r71 = r70 >= 0 :: signed
     return 1
 
@@ -363,7 +363,7 @@ def f(x):
 L0:
     r0 = __main__.B :: type
     r1 = get_element_ptr x ob_type :: PyObject
-    r2 = load_mem r1 :: builtins.object*
+    r2 = borrow load_mem r1 :: builtins.object*
     keep_alive x
     r3 = r2 == r0
     if r3 goto L1 else goto L2 :: bool
@@ -402,7 +402,7 @@ def f(x):
 L0:
     r0 = __main__.A :: type
     r1 = get_element_ptr x ob_type :: PyObject
-    r2 = load_mem r1 :: builtins.object*
+    r2 = borrow load_mem r1 :: builtins.object*
     keep_alive x
     r3 = r2 == r0
     if r3 goto L1 else goto L2 :: bool
@@ -412,7 +412,7 @@ L1:
 L2:
     r5 = __main__.B :: type
     r6 = get_element_ptr x ob_type :: PyObject
-    r7 = load_mem r6 :: builtins.object*
+    r7 = borrow load_mem r6 :: builtins.object*
     keep_alive x
     r8 = r7 == r5
     r4 = r8
@@ -449,7 +449,7 @@ def f(x):
 L0:
     r0 = __main__.A :: type
     r1 = get_element_ptr x ob_type :: PyObject
-    r2 = load_mem r1 :: builtins.object*
+    r2 = borrow load_mem r1 :: builtins.object*
     keep_alive x
     r3 = r2 == r0
     if r3 goto L1 else goto L2 :: bool
@@ -459,7 +459,7 @@ L1:
 L2:
     r5 = __main__.R :: type
     r6 = get_element_ptr x ob_type :: PyObject
-    r7 = load_mem r6 :: builtins.object*
+    r7 = borrow load_mem r6 :: builtins.object*
     keep_alive x
     r8 = r7 == r5
     r4 = r8
@@ -500,7 +500,7 @@ def f(x):
 L0:
     r0 = __main__.A :: type
     r1 = get_element_ptr x ob_type :: PyObject
-    r2 = load_mem r1 :: builtins.object*
+    r2 = borrow load_mem r1 :: builtins.object*
     keep_alive x
     r3 = r2 == r0
     if r3 goto L1 else goto L2 :: bool
@@ -510,7 +510,7 @@ L1:
 L2:
     r5 = __main__.C :: type
     r6 = get_element_ptr x ob_type :: PyObject
-    r7 = load_mem r6 :: builtins.object*
+    r7 = borrow load_mem r6 :: builtins.object*
     keep_alive x
     r8 = r7 == r5
     r4 = r8
@@ -854,22 +854,42 @@ def Base.__ne__(__mypyc_self__, rhs):
     __mypyc_self__ :: __main__.Base
     rhs, r0, r1 :: object
     r2 :: bit
-    r3 :: i32
-    r4 :: bit
-    r5 :: bool
+    r3 :: object
+    r4, r5 :: bit
     r6 :: object
+    r7 :: bit
+    r8 :: i32
+    r9 :: bit
+    r10 :: bool
+    r11 :: object
 L0:
     r0 = __mypyc_self__.__eq__(rhs)
     r1 = load_address _Py_NotImplementedStruct
     r2 = r0 == r1
-    if r2 goto L2 else goto L1 :: bool
+    if r2 goto L7 else goto L1 :: bool
 L1:
-    r3 = PyObject_Not(r0)
-    r4 = r3 >= 0 :: signed
-    r5 = truncate r3: i32 to builtins.bool
-    r6 = box(bool, r5)
-    return r6
+    r3 = load_global Py_True :: static
+    r4 = r0 == r3
+    if r4 goto L2 else goto L3 :: bool
 L2:
+    r5 = 0
+    goto L6
+L3:
+    r6 = load_global Py_False :: static
+    r7 = r0 == r6
+    if r7 goto L4 else goto L5 :: bool
+L4:
+    r5 = 1
+    goto L6
+L5:
+    r8 = PyObject_Not(r0)
+    r9 = r8 >= 0 :: signed
+    r10 = truncate r8: i32 to builtins.bool
+    r5 = r10
+L6:
+    r11 = box(bit, r5)
+    return r11
+L7:
     return r1
 def Derived.__eq__(self, other):
     self :: __main__.Derived
@@ -979,22 +999,42 @@ def Derived.__ne__(__mypyc_self__, rhs):
     __mypyc_self__ :: __main__.Derived
     rhs, r0, r1 :: object
     r2 :: bit
-    r3 :: i32
-    r4 :: bit
-    r5 :: bool
+    r3 :: object
+    r4, r5 :: bit
     r6 :: object
+    r7 :: bit
+    r8 :: i32
+    r9 :: bit
+    r10 :: bool
+    r11 :: object
 L0:
     r0 = __mypyc_self__.__eq__(rhs)
     r1 = load_address _Py_NotImplementedStruct
     r2 = r0 == r1
-    if r2 goto L2 else goto L1 :: bool
+    if r2 goto L7 else goto L1 :: bool
 L1:
-    r3 = PyObject_Not(r0)
-    r4 = r3 >= 0 :: signed
-    r5 = truncate r3: i32 to builtins.bool
-    r6 = box(bool, r5)
-    return r6
+    r3 = load_global Py_True :: static
+    r4 = r0 == r3
+    if r4 goto L2 else goto L3 :: bool
 L2:
+    r5 = 0
+    goto L6
+L3:
+    r6 = load_global Py_False :: static
+    r7 = r0 == r6
+    if r7 goto L4 else goto L5 :: bool
+L4:
+    r5 = 1
+    goto L6
+L5:
+    r8 = PyObject_Not(r0)
+    r9 = r8 >= 0 :: signed
+    r10 = truncate r8: i32 to builtins.bool
+    r5 = r10
+L6:
+    r11 = box(bit, r5)
+    return r11
+L7:
     return r1
 
 [case testDefaultVars]
@@ -1383,3 +1423,314 @@ class M(type):  # E: Inheriting from most builtin types is unimplemented \
 @mypyc_attr(native_class=True)
 class A(metaclass=M):  # E: Class is marked as native_class=True but it can't be a native class. Classes with a metaclass other than ABCMeta, TypingMeta or GenericMeta can't be native classes.
     pass
+
+[case testReservedName]
+from typing import Any, overload
+
+def decorator(cls):
+    return cls
+
+class TestMethod:
+    def __mypyc_generator_helper__(self) -> None:  # E: Method name "__mypyc_generator_helper__" is reserved for mypyc internal use
+        pass
+
+class TestDecorator:
+    @decorator  # E: Method name "__mypyc_generator_helper__" is reserved for mypyc internal use
+    def __mypyc_generator_helper__(self) -> None:
+        pass
+
+class TestOverload:
+    @overload # E: Method name "__mypyc_generator_helper__" is reserved for mypyc internal use
+    def __mypyc_generator_helper__(self, x: int) -> int: ...
+
+    @overload
+    def __mypyc_generator_helper__(self, x: str) -> str: ...
+
+    def __mypyc_generator_helper__(self, x: Any) -> Any:
+        return x
+
+[case testNativeBufferFastPath]
+from typing import Final
+from mypy_extensions import u8
+from native_internal import (
+    Buffer, write_bool, read_bool, write_str, read_str, write_float, read_float,
+    write_int, read_int, write_tag, read_tag
+)
+
+Tag = u8
+TAG: Final[Tag] = 1
+
+def foo() -> None:
+    b = Buffer()
+    write_str(b, "foo")
+    write_bool(b, True)
+    write_float(b, 0.1)
+    write_int(b, 1)
+    write_tag(b, TAG)
+
+    b = Buffer(b.getvalue())
+    x = read_str(b)
+    y = read_bool(b)
+    z = read_float(b)
+    t = read_int(b)
+    u = read_tag(b)
+[out]
+def foo():
+    r0, b :: native_internal.Buffer
+    r1 :: str
+    r2, r3, r4, r5, r6 :: None
+    r7 :: bytes
+    r8 :: native_internal.Buffer
+    r9, x :: str
+    r10, y :: bool
+    r11, z :: float
+    r12, t :: int
+    r13, u :: u8
+L0:
+    r0 = Buffer_internal_empty()
+    b = r0
+    r1 = 'foo'
+    r2 = write_str_internal(b, r1)
+    r3 = write_bool_internal(b, 1)
+    r4 = write_float_internal(b, 0.1)
+    r5 = write_int_internal(b, 2)
+    r6 = write_tag_internal(b, 1)
+    r7 = Buffer_getvalue_internal(b)
+    r8 = Buffer_internal(r7)
+    b = r8
+    r9 = read_str_internal(b)
+    x = r9
+    r10 = read_bool_internal(b)
+    y = r10
+    r11 = read_float_internal(b)
+    z = r11
+    r12 = read_int_internal(b)
+    t = r12
+    r13 = read_tag_internal(b)
+    u = r13
+    return 1
+
+[case testEnumFastPath]
+from enum import Enum
+
+def test(e: E) -> bool:
+    return e.is_one()
+
+class E(Enum):
+    ONE = 1
+    TWO = 2
+
+    def is_one(self) -> bool:
+        return self == E.ONE
+[out]
+def test(e):
+    e :: __main__.E
+    r0 :: bool
+L0:
+    r0 = e.__mypyc_fast_is_one()
+    return r0
+def is_one_E_obj.__get__(__mypyc_self__, instance, owner):
+    __mypyc_self__, instance, owner, r0 :: object
+    r1 :: bit
+    r2 :: object
+L0:
+    r0 = load_address _Py_NoneStruct
+    r1 = instance == r0
+    if r1 goto L1 else goto L2 :: bool
+L1:
+    return __mypyc_self__
+L2:
+    r2 = PyMethod_New(__mypyc_self__, instance)
+    return r2
+def is_one_E_obj.__call__(__mypyc_self__, self):
+    __mypyc_self__ :: __main__.is_one_E_obj
+    self, r0 :: __main__.E
+    r1 :: bool
+    r2 :: bit
+L0:
+    r0 = __main__.E.ONE :: static
+    if is_error(r0) goto L1 else goto L2
+L1:
+    r1 = raise NameError('value for final name "ONE" was not set')
+    unreachable
+L2:
+    r2 = self == r0
+    return r2
+def E.__mypyc_fast_is_one(self):
+    self, r0 :: __main__.E
+    r1 :: bool
+    r2 :: bit
+L0:
+    r0 = __main__.E.ONE :: static
+    if is_error(r0) goto L1 else goto L2
+L1:
+    r1 = raise NameError('value for final name "ONE" was not set')
+    unreachable
+L2:
+    r2 = self == r0
+    return r2
+
+[case testTypeObjectName_python3_11]
+from typing import Any
+
+class C: pass
+class D(C): pass
+
+def n1(t: type[object]) -> str:
+    return t.__name__
+
+def n2(t: Any) -> str:
+    return t.__name__
+
+def n3() -> str:
+    return C.__name__
+
+def n4(t: type[C]) -> str:
+    return t.__name__
+[out]
+def n1(t):
+    t, r0 :: object
+    r1 :: str
+L0:
+    r0 = CPy_GetName(t)
+    r1 = cast(str, r0)
+    return r1
+def n2(t):
+    t, r0 :: object
+    r1 :: str
+L0:
+    r0 = CPy_GetName(t)
+    r1 = cast(str, r0)
+    return r1
+def n3():
+    r0, r1 :: object
+    r2 :: str
+L0:
+    r0 = __main__.C :: type
+    r1 = CPy_GetName(r0)
+    r2 = cast(str, r1)
+    return r2
+def n4(t):
+    t, r0 :: object
+    r1 :: str
+L0:
+    r0 = CPy_GetName(t)
+    r1 = cast(str, r0)
+    return r1
+
+[case testTypeOfObject]
+class C: pass
+class D(C): pass
+
+def generic_type(x: object) -> type[object]:
+    return type(x)
+
+def generic_class(x: object) -> type[object]:
+    return x.__class__
+
+def native_type(x: C) -> type[object]:
+    return type(x)
+
+def native_class(x: C) -> type[object]:
+    return x.__class__
+[out]
+def generic_type(x):
+    x, r0 :: object
+L0:
+    r0 = CPy_TYPE(x)
+    return r0
+def generic_class(x):
+    x :: object
+    r0 :: str
+    r1 :: object
+L0:
+    r0 = '__class__'
+    r1 = CPyObject_GetAttr(x, r0)
+    return r1
+def native_type(x):
+    x :: __main__.C
+    r0 :: object
+L0:
+    r0 = CPy_TYPE(x)
+    return r0
+def native_class(x):
+    x :: __main__.C
+    r0 :: object
+L0:
+    r0 = CPy_TYPE(x)
+    return r0
+
+[case testDunderNew]
+from __future__ import annotations
+
+class Test:
+    val: int
+
+    def __new__(cls, val: int) -> Test:
+        obj = super().__new__(cls)
+        obj.val = val
+        return obj
+
+def fn() -> Test:
+    return Test.__new__(Test, 42)
+
+class NewClassMethod:
+    val: int
+
+    @classmethod
+    def __new__(cls, val: int) -> NewClassMethod:
+        obj = super().__new__(cls)
+        obj.val = val
+        return obj
+
+def fn2() -> NewClassMethod:
+    return NewClassMethod.__new__(42)
+
+[out]
+def Test.__new__(cls, val):
+    cls :: object
+    val :: int
+    r0, obj :: __main__.Test
+    r1 :: bool
+L0:
+    r0 = __mypyc__Test_setup(cls)
+    obj = r0
+    obj.val = val; r1 = is_error
+    return obj
+def fn():
+    r0 :: object
+    r1 :: __main__.Test
+L0:
+    r0 = __main__.Test :: type
+    r1 = Test.__new__(r0, 84)
+    return r1
+def NewClassMethod.__new__(cls, val):
+    cls :: object
+    val :: int
+    r0, obj :: __main__.NewClassMethod
+    r1 :: bool
+L0:
+    r0 = __mypyc__NewClassMethod_setup(cls)
+    obj = r0
+    obj.val = val; r1 = is_error
+    return obj
+def fn2():
+    r0 :: object
+    r1 :: __main__.NewClassMethod
+L0:
+    r0 = __main__.NewClassMethod :: type
+    r1 = NewClassMethod.__new__(r0, 84)
+    return r1
+
+[case testUnsupportedDunderNew]
+from __future__ import annotations
+from mypy_extensions import mypyc_attr
+
+@mypyc_attr(native_class=False)
+class NonNative:
+    def __new__(cls) -> NonNative:
+        return super().__new__(cls)  # E: super().__new__() not supported for non-extension classes
+
+class InheritsPython(dict):
+    def __new__(cls) -> InheritsPython:
+        return super().__new__(cls)  # E: super().__new__() not supported for classes inheriting from non-native classes
diff --git a/mypyc/test-data/irbuild-dict.test b/mypyc/test-data/irbuild-dict.test
index a71f5aa2d8a2..e0c014f07813 100644
--- a/mypyc/test-data/irbuild-dict.test
+++ b/mypyc/test-data/irbuild-dict.test
@@ -152,41 +152,39 @@ def increment(d):
     d :: dict
     r0 :: short_int
     r1 :: native_int
-    r2 :: short_int
-    r3 :: object
-    r4 :: tuple[bool, short_int, object]
-    r5 :: short_int
-    r6 :: bool
-    r7 :: object
-    r8, k :: str
-    r9, r10, r11 :: object
-    r12 :: i32
-    r13, r14, r15 :: bit
+    r2 :: object
+    r3 :: tuple[bool, short_int, object]
+    r4 :: short_int
+    r5 :: bool
+    r6 :: object
+    r7, k :: str
+    r8, r9, r10 :: object
+    r11 :: i32
+    r12, r13, r14 :: bit
 L0:
     r0 = 0
     r1 = PyDict_Size(d)
-    r2 = r1 << 1
-    r3 = CPyDict_GetKeysIter(d)
+    r2 = CPyDict_GetKeysIter(d)
 L1:
-    r4 = CPyDict_NextKey(r3, r0)
-    r5 = r4[1]
-    r0 = r5
-    r6 = r4[0]
-    if r6 goto L2 else goto L4 :: bool
+    r3 = CPyDict_NextKey(r2, r0)
+    r4 = r3[1]
+    r0 = r4
+    r5 = r3[0]
+    if r5 goto L2 else goto L4 :: bool
 L2:
-    r7 = r4[2]
-    r8 = cast(str, r7)
-    k = r8
-    r9 = CPyDict_GetItem(d, k)
-    r10 = object 1
-    r11 = PyNumber_InPlaceAdd(r9, r10)
-    r12 = CPyDict_SetItem(d, k, r11)
-    r13 = r12 >= 0 :: signed
+    r6 = r3[2]
+    r7 = cast(str, r6)
+    k = r7
+    r8 = CPyDict_GetItem(d, k)
+    r9 = object 1
+    r10 = PyNumber_InPlaceAdd(r8, r9)
+    r11 = CPyDict_SetItem(d, k, r10)
+    r12 = r11 >= 0 :: signed
 L3:
-    r14 = CPyDict_CheckSize(d, r2)
+    r13 = CPyDict_CheckSize(d, r1)
     goto L1
 L4:
-    r15 = CPy_NoErrOccurred()
+    r14 = CPy_NoErrOccurred()
 L5:
     return d
 
@@ -244,206 +242,185 @@ def print_dict_methods(d1, d2):
     d1, d2 :: dict
     r0 :: short_int
     r1 :: native_int
-    r2 :: short_int
-    r3 :: object
-    r4 :: tuple[bool, short_int, object]
-    r5 :: short_int
-    r6 :: bool
-    r7 :: object
-    r8, v :: int
-    r9 :: object
-    r10 :: i32
-    r11 :: bit
-    r12 :: bool
-    r13, r14 :: bit
-    r15 :: short_int
-    r16 :: native_int
-    r17 :: short_int
-    r18 :: object
-    r19 :: tuple[bool, short_int, object, object]
-    r20 :: short_int
-    r21 :: bool
-    r22, r23 :: object
-    r24, r25, k :: int
-    r26, r27, r28, r29, r30 :: object
-    r31 :: i32
-    r32, r33, r34 :: bit
+    r2 :: object
+    r3 :: tuple[bool, short_int, object]
+    r4 :: short_int
+    r5 :: bool
+    r6 :: object
+    r7, v :: int
+    r8 :: object
+    r9 :: i32
+    r10 :: bit
+    r11 :: bool
+    r12, r13 :: bit
+    r14 :: short_int
+    r15 :: native_int
+    r16 :: object
+    r17 :: tuple[bool, short_int, object, object]
+    r18 :: short_int
+    r19 :: bool
+    r20, r21 :: object
+    r22, r23, k :: int
+    r24, r25, r26, r27, r28 :: object
+    r29 :: i32
+    r30, r31, r32 :: bit
 L0:
     r0 = 0
     r1 = PyDict_Size(d1)
-    r2 = r1 << 1
-    r3 = CPyDict_GetValuesIter(d1)
+    r2 = CPyDict_GetValuesIter(d1)
 L1:
-    r4 = CPyDict_NextValue(r3, r0)
-    r5 = r4[1]
-    r0 = r5
-    r6 = r4[0]
-    if r6 goto L2 else goto L6 :: bool
+    r3 = CPyDict_NextValue(r2, r0)
+    r4 = r3[1]
+    r0 = r4
+    r5 = r3[0]
+    if r5 goto L2 else goto L6 :: bool
 L2:
-    r7 = r4[2]
-    r8 = unbox(int, r7)
-    v = r8
-    r9 = box(int, v)
-    r10 = PyDict_Contains(d2, r9)
-    r11 = r10 >= 0 :: signed
-    r12 = truncate r10: i32 to builtins.bool
-    if r12 goto L3 else goto L4 :: bool
+    r6 = r3[2]
+    r7 = unbox(int, r6)
+    v = r7
+    r8 = box(int, v)
+    r9 = PyDict_Contains(d2, r8)
+    r10 = r9 >= 0 :: signed
+    r11 = truncate r9: i32 to builtins.bool
+    if r11 goto L3 else goto L4 :: bool
 L3:
     return 1
 L4:
 L5:
-    r13 = CPyDict_CheckSize(d1, r2)
+    r12 = CPyDict_CheckSize(d1, r1)
     goto L1
 L6:
-    r14 = CPy_NoErrOccurred()
+    r13 = CPy_NoErrOccurred()
 L7:
-    r15 = 0
-    r16 = PyDict_Size(d2)
-    r17 = r16 << 1
-    r18 = CPyDict_GetItemsIter(d2)
+    r14 = 0
+    r15 = PyDict_Size(d2)
+    r16 = CPyDict_GetItemsIter(d2)
 L8:
-    r19 = CPyDict_NextItem(r18, r15)
-    r20 = r19[1]
-    r15 = r20
-    r21 = r19[0]
-    if r21 goto L9 else goto L11 :: bool
+    r17 = CPyDict_NextItem(r16, r14)
+    r18 = r17[1]
+    r14 = r18
+    r19 = r17[0]
+    if r19 goto L9 else goto L11 :: bool
 L9:
-    r22 = r19[2]
-    r23 = r19[3]
-    r24 = unbox(int, r22)
-    r25 = unbox(int, r23)
-    k = r24
-    v = r25
-    r26 = box(int, k)
-    r27 = CPyDict_GetItem(d2, r26)
-    r28 = box(int, v)
-    r29 = PyNumber_InPlaceAdd(r27, r28)
-    r30 = box(int, k)
-    r31 = CPyDict_SetItem(d2, r30, r29)
-    r32 = r31 >= 0 :: signed
+    r20 = r17[2]
+    r21 = r17[3]
+    r22 = unbox(int, r20)
+    r23 = unbox(int, r21)
+    k = r22
+    v = r23
+    r24 = box(int, k)
+    r25 = CPyDict_GetItem(d2, r24)
+    r26 = box(int, v)
+    r27 = PyNumber_InPlaceAdd(r25, r26)
+    r28 = box(int, k)
+    r29 = CPyDict_SetItem(d2, r28, r27)
+    r30 = r29 >= 0 :: signed
 L10:
-    r33 = CPyDict_CheckSize(d2, r17)
+    r31 = CPyDict_CheckSize(d2, r15)
     goto L8
 L11:
-    r34 = CPy_NoErrOccurred()
+    r32 = CPy_NoErrOccurred()
 L12:
     return 1
 def union_of_dicts(d):
     d, r0, new :: dict
     r1 :: short_int
     r2 :: native_int
-    r3 :: short_int
-    r4 :: object
-    r5 :: tuple[bool, short_int, object, object]
-    r6 :: short_int
-    r7 :: bool
-    r8, r9 :: object
-    r10 :: str
-    r11 :: union[int, str]
+    r3 :: object
+    r4 :: tuple[bool, short_int, object, object]
+    r5 :: short_int
+    r6 :: bool
+    r7, r8 :: object
+    r9 :: str
+    r10 :: union[int, str]
     k :: str
     v :: union[int, str]
-    r12 :: object
-    r13 :: object[1]
-    r14 :: object_ptr
-    r15 :: object
-    r16 :: int
-    r17 :: object
-    r18 :: i32
-    r19, r20, r21 :: bit
+    r11 :: object
+    r12 :: object[1]
+    r13 :: object_ptr
+    r14 :: object
+    r15 :: int
+    r16 :: object
+    r17 :: i32
+    r18, r19, r20 :: bit
 L0:
     r0 = PyDict_New()
     new = r0
     r1 = 0
     r2 = PyDict_Size(d)
-    r3 = r2 << 1
-    r4 = CPyDict_GetItemsIter(d)
+    r3 = CPyDict_GetItemsIter(d)
 L1:
-    r5 = CPyDict_NextItem(r4, r1)
-    r6 = r5[1]
-    r1 = r6
-    r7 = r5[0]
-    if r7 goto L2 else goto L4 :: bool
+    r4 = CPyDict_NextItem(r3, r1)
+    r5 = r4[1]
+    r1 = r5
+    r6 = r4[0]
+    if r6 goto L2 else goto L4 :: bool
 L2:
-    r8 = r5[2]
-    r9 = r5[3]
-    r10 = cast(str, r8)
-    r11 = cast(union[int, str], r9)
-    k = r10
-    v = r11
-    r12 = load_address PyLong_Type
-    r13 = [v]
-    r14 = load_address r13
-    r15 = PyObject_Vectorcall(r12, r14, 1, 0)
+    r7 = r4[2]
+    r8 = r4[3]
+    r9 = cast(str, r7)
+    r10 = cast(union[int, str], r8)
+    k = r9
+    v = r10
+    r11 = load_address PyLong_Type
+    r12 = [v]
+    r13 = load_address r12
+    r14 = PyObject_Vectorcall(r11, r13, 1, 0)
     keep_alive v
-    r16 = unbox(int, r15)
-    r17 = box(int, r16)
-    r18 = CPyDict_SetItem(new, k, r17)
-    r19 = r18 >= 0 :: signed
+    r15 = unbox(int, r14)
+    r16 = box(int, r15)
+    r17 = CPyDict_SetItem(new, k, r16)
+    r18 = r17 >= 0 :: signed
 L3:
-    r20 = CPyDict_CheckSize(d, r3)
+    r19 = CPyDict_CheckSize(d, r2)
     goto L1
 L4:
-    r21 = CPy_NoErrOccurred()
+    r20 = CPy_NoErrOccurred()
 L5:
     return 1
 def typeddict(d):
     d :: dict
     r0 :: short_int
     r1 :: native_int
-    r2 :: short_int
-    r3 :: object
-    r4 :: tuple[bool, short_int, object, object]
-    r5 :: short_int
-    r6 :: bool
-    r7, r8 :: object
-    r9, k :: str
+    r2 :: object
+    r3 :: tuple[bool, short_int, object, object]
+    r4 :: short_int
+    r5 :: bool
+    r6, r7 :: object
+    r8, k :: str
     v :: object
-    r10 :: str
-    r11 :: i32
-    r12 :: bit
-    r13 :: object
-    r14, r15, r16 :: bit
+    r9 :: str
+    r10 :: bool
     name :: object
-    r17, r18 :: bit
+    r11, r12 :: bit
 L0:
     r0 = 0
     r1 = PyDict_Size(d)
-    r2 = r1 << 1
-    r3 = CPyDict_GetItemsIter(d)
+    r2 = CPyDict_GetItemsIter(d)
 L1:
-    r4 = CPyDict_NextItem(r3, r0)
-    r5 = r4[1]
-    r0 = r5
-    r6 = r4[0]
-    if r6 goto L2 else goto L9 :: bool
+    r3 = CPyDict_NextItem(r2, r0)
+    r4 = r3[1]
+    r0 = r4
+    r5 = r3[0]
+    if r5 goto L2 else goto L6 :: bool
 L2:
-    r7 = r4[2]
-    r8 = r4[3]
-    r9 = cast(str, r7)
-    k = r9
-    v = r8
-    r10 = 'name'
-    r11 = PyUnicode_Compare(k, r10)
-    r12 = r11 == -1
-    if r12 goto L3 else goto L5 :: bool
+    r6 = r3[2]
+    r7 = r3[3]
+    r8 = cast(str, r6)
+    k = r8
+    v = r7
+    r9 = 'name'
+    r10 = CPyStr_Equal(k, r9)
+    if r10 goto L3 else goto L4 :: bool
 L3:
-    r13 = PyErr_Occurred()
-    r14 = r13 != 0
-    if r14 goto L4 else goto L5 :: bool
+    name = v
 L4:
-    r15 = CPy_KeepPropagating()
 L5:
-    r16 = r11 == 0
-    if r16 goto L6 else goto L7 :: bool
+    r11 = CPyDict_CheckSize(d, r1)
+    goto L1
 L6:
-    name = v
+    r12 = CPy_NoErrOccurred()
 L7:
-L8:
-    r17 = CPyDict_CheckSize(d, r2)
-    goto L1
-L9:
-    r18 = CPy_NoErrOccurred()
-L10:
     return 1
 
 [case testDictLoadAddress]
diff --git a/mypyc/test-data/irbuild-generics.test b/mypyc/test-data/irbuild-generics.test
index feb7b9db20fb..96437a0079c9 100644
--- a/mypyc/test-data/irbuild-generics.test
+++ b/mypyc/test-data/irbuild-generics.test
@@ -166,25 +166,14 @@ execute(f, 1)
 def execute(func, args, kwargs):
     func :: object
     args :: tuple
-    kwargs :: dict
-    r0 :: list
+    kwargs, r0 :: dict
     r1 :: object
-    r2 :: dict
-    r3 :: i32
-    r4 :: bit
-    r5 :: tuple
-    r6 :: object
-    r7 :: int
+    r2 :: int
 L0:
-    r0 = PyList_New(0)
-    r1 = CPyList_Extend(r0, args)
-    r2 = PyDict_New()
-    r3 = CPyDict_UpdateInDisplay(r2, kwargs)
-    r4 = r3 >= 0 :: signed
-    r5 = PyList_AsTuple(r0)
-    r6 = PyObject_Call(func, r5, r2)
-    r7 = unbox(int, r6)
-    return r7
+    r0 = PyDict_Copy(kwargs)
+    r1 = PyObject_Call(func, args, r0)
+    r2 = unbox(int, r1)
+    return r2
 def f(x):
     x :: int
 L0:
@@ -226,153 +215,145 @@ def fn_mapping(m):
     r0 :: list
     r1 :: short_int
     r2 :: native_int
-    r3 :: short_int
-    r4 :: object
-    r5 :: tuple[bool, short_int, object]
-    r6 :: short_int
-    r7 :: bool
-    r8 :: object
-    r9, x :: str
-    r10 :: i32
-    r11, r12, r13 :: bit
-    r14 :: list
-    r15 :: short_int
-    r16 :: native_int
-    r17 :: short_int
-    r18 :: object
-    r19 :: tuple[bool, short_int, object]
-    r20 :: short_int
-    r21 :: bool
+    r3 :: object
+    r4 :: tuple[bool, short_int, object]
+    r5 :: short_int
+    r6 :: bool
+    r7 :: object
+    r8, x :: str
+    r9 :: i32
+    r10, r11, r12 :: bit
+    r13 :: list
+    r14 :: short_int
+    r15 :: native_int
+    r16 :: object
+    r17 :: tuple[bool, short_int, object]
+    r18 :: short_int
+    r19 :: bool
+    r20 :: object
+    r21, x_2 :: int
     r22 :: object
-    r23, x_2 :: int
-    r24 :: object
-    r25 :: i32
-    r26, r27, r28 :: bit
-    r29 :: set
-    r30 :: short_int
-    r31 :: native_int
+    r23 :: i32
+    r24, r25, r26 :: bit
+    r27 :: set
+    r28 :: short_int
+    r29 :: native_int
+    r30 :: object
+    r31 :: tuple[bool, short_int, object]
     r32 :: short_int
-    r33 :: object
-    r34 :: tuple[bool, short_int, object]
-    r35 :: short_int
-    r36 :: bool
-    r37 :: object
-    r38, x_3 :: str
-    r39 :: i32
-    r40, r41, r42 :: bit
-    r43 :: dict
-    r44 :: short_int
-    r45 :: native_int
-    r46 :: short_int
-    r47 :: object
-    r48 :: tuple[bool, short_int, object, object]
-    r49 :: short_int
-    r50 :: bool
-    r51, r52 :: object
-    r53 :: str
-    r54 :: int
+    r33 :: bool
+    r34 :: object
+    r35, x_3 :: str
+    r36 :: i32
+    r37, r38, r39 :: bit
+    r40 :: dict
+    r41 :: short_int
+    r42 :: native_int
+    r43 :: object
+    r44 :: tuple[bool, short_int, object, object]
+    r45 :: short_int
+    r46 :: bool
+    r47, r48 :: object
+    r49 :: str
+    r50 :: int
     k :: str
     v :: int
-    r55 :: object
-    r56 :: i32
-    r57, r58, r59 :: bit
+    r51 :: object
+    r52 :: i32
+    r53, r54, r55 :: bit
 L0:
     r0 = PyList_New(0)
     r1 = 0
     r2 = PyDict_Size(m)
-    r3 = r2 << 1
-    r4 = CPyDict_GetKeysIter(m)
+    r3 = CPyDict_GetKeysIter(m)
 L1:
-    r5 = CPyDict_NextKey(r4, r1)
-    r6 = r5[1]
-    r1 = r6
-    r7 = r5[0]
-    if r7 goto L2 else goto L4 :: bool
+    r4 = CPyDict_NextKey(r3, r1)
+    r5 = r4[1]
+    r1 = r5
+    r6 = r4[0]
+    if r6 goto L2 else goto L4 :: bool
 L2:
-    r8 = r5[2]
-    r9 = cast(str, r8)
-    x = r9
-    r10 = PyList_Append(r0, x)
-    r11 = r10 >= 0 :: signed
+    r7 = r4[2]
+    r8 = cast(str, r7)
+    x = r8
+    r9 = PyList_Append(r0, x)
+    r10 = r9 >= 0 :: signed
 L3:
-    r12 = CPyDict_CheckSize(m, r3)
+    r11 = CPyDict_CheckSize(m, r2)
     goto L1
 L4:
-    r13 = CPy_NoErrOccurred()
+    r12 = CPy_NoErrOccurred()
 L5:
-    r14 = PyList_New(0)
-    r15 = 0
-    r16 = PyDict_Size(m)
-    r17 = r16 << 1
-    r18 = CPyDict_GetValuesIter(m)
+    r13 = PyList_New(0)
+    r14 = 0
+    r15 = PyDict_Size(m)
+    r16 = CPyDict_GetValuesIter(m)
 L6:
-    r19 = CPyDict_NextValue(r18, r15)
-    r20 = r19[1]
-    r15 = r20
-    r21 = r19[0]
-    if r21 goto L7 else goto L9 :: bool
+    r17 = CPyDict_NextValue(r16, r14)
+    r18 = r17[1]
+    r14 = r18
+    r19 = r17[0]
+    if r19 goto L7 else goto L9 :: bool
 L7:
-    r22 = r19[2]
-    r23 = unbox(int, r22)
-    x_2 = r23
-    r24 = box(int, x_2)
-    r25 = PyList_Append(r14, r24)
-    r26 = r25 >= 0 :: signed
+    r20 = r17[2]
+    r21 = unbox(int, r20)
+    x_2 = r21
+    r22 = box(int, x_2)
+    r23 = PyList_Append(r13, r22)
+    r24 = r23 >= 0 :: signed
 L8:
-    r27 = CPyDict_CheckSize(m, r17)
+    r25 = CPyDict_CheckSize(m, r15)
     goto L6
 L9:
-    r28 = CPy_NoErrOccurred()
+    r26 = CPy_NoErrOccurred()
 L10:
-    r29 = PySet_New(0)
-    r30 = 0
-    r31 = PyDict_Size(m)
-    r32 = r31 << 1
-    r33 = CPyDict_GetKeysIter(m)
+    r27 = PySet_New(0)
+    r28 = 0
+    r29 = PyDict_Size(m)
+    r30 = CPyDict_GetKeysIter(m)
 L11:
-    r34 = CPyDict_NextKey(r33, r30)
-    r35 = r34[1]
-    r30 = r35
-    r36 = r34[0]
-    if r36 goto L12 else goto L14 :: bool
+    r31 = CPyDict_NextKey(r30, r28)
+    r32 = r31[1]
+    r28 = r32
+    r33 = r31[0]
+    if r33 goto L12 else goto L14 :: bool
 L12:
-    r37 = r34[2]
-    r38 = cast(str, r37)
-    x_3 = r38
-    r39 = PySet_Add(r29, x_3)
-    r40 = r39 >= 0 :: signed
+    r34 = r31[2]
+    r35 = cast(str, r34)
+    x_3 = r35
+    r36 = PySet_Add(r27, x_3)
+    r37 = r36 >= 0 :: signed
 L13:
-    r41 = CPyDict_CheckSize(m, r32)
+    r38 = CPyDict_CheckSize(m, r29)
     goto L11
 L14:
-    r42 = CPy_NoErrOccurred()
+    r39 = CPy_NoErrOccurred()
 L15:
-    r43 = PyDict_New()
-    r44 = 0
-    r45 = PyDict_Size(m)
-    r46 = r45 << 1
-    r47 = CPyDict_GetItemsIter(m)
+    r40 = PyDict_New()
+    r41 = 0
+    r42 = PyDict_Size(m)
+    r43 = CPyDict_GetItemsIter(m)
 L16:
-    r48 = CPyDict_NextItem(r47, r44)
-    r49 = r48[1]
-    r44 = r49
-    r50 = r48[0]
-    if r50 goto L17 else goto L19 :: bool
+    r44 = CPyDict_NextItem(r43, r41)
+    r45 = r44[1]
+    r41 = r45
+    r46 = r44[0]
+    if r46 goto L17 else goto L19 :: bool
 L17:
-    r51 = r48[2]
-    r52 = r48[3]
-    r53 = cast(str, r51)
-    r54 = unbox(int, r52)
-    k = r53
-    v = r54
-    r55 = box(int, v)
-    r56 = CPyDict_SetItem(r43, k, r55)
-    r57 = r56 >= 0 :: signed
+    r47 = r44[2]
+    r48 = r44[3]
+    r49 = cast(str, r47)
+    r50 = unbox(int, r48)
+    k = r49
+    v = r50
+    r51 = box(int, v)
+    r52 = PyDict_SetItem(r40, k, r51)
+    r53 = r52 >= 0 :: signed
 L18:
-    r58 = CPyDict_CheckSize(m, r46)
+    r54 = CPyDict_CheckSize(m, r42)
     goto L16
 L19:
-    r59 = CPy_NoErrOccurred()
+    r55 = CPy_NoErrOccurred()
 L20:
     return 1
 def fn_union(m):
@@ -380,149 +361,141 @@ def fn_union(m):
     r0 :: list
     r1 :: short_int
     r2 :: native_int
-    r3 :: short_int
-    r4 :: object
-    r5 :: tuple[bool, short_int, object]
-    r6 :: short_int
-    r7 :: bool
-    r8 :: object
-    r9, x :: str
-    r10 :: i32
-    r11, r12, r13 :: bit
-    r14 :: list
-    r15 :: short_int
-    r16 :: native_int
-    r17 :: short_int
-    r18 :: object
-    r19 :: tuple[bool, short_int, object]
-    r20 :: short_int
-    r21 :: bool
-    r22 :: object
-    r23, x_2 :: union[int, str]
-    r24 :: i32
-    r25, r26, r27 :: bit
-    r28 :: set
-    r29 :: short_int
-    r30 :: native_int
+    r3 :: object
+    r4 :: tuple[bool, short_int, object]
+    r5 :: short_int
+    r6 :: bool
+    r7 :: object
+    r8, x :: str
+    r9 :: i32
+    r10, r11, r12 :: bit
+    r13 :: list
+    r14 :: short_int
+    r15 :: native_int
+    r16 :: object
+    r17 :: tuple[bool, short_int, object]
+    r18 :: short_int
+    r19 :: bool
+    r20 :: object
+    r21, x_2 :: union[int, str]
+    r22 :: i32
+    r23, r24, r25 :: bit
+    r26 :: set
+    r27 :: short_int
+    r28 :: native_int
+    r29 :: object
+    r30 :: tuple[bool, short_int, object]
     r31 :: short_int
-    r32 :: object
-    r33 :: tuple[bool, short_int, object]
-    r34 :: short_int
-    r35 :: bool
-    r36 :: object
-    r37, x_3 :: str
-    r38 :: i32
-    r39, r40, r41 :: bit
-    r42 :: dict
-    r43 :: short_int
-    r44 :: native_int
-    r45 :: short_int
-    r46 :: object
-    r47 :: tuple[bool, short_int, object, object]
-    r48 :: short_int
-    r49 :: bool
-    r50, r51 :: object
-    r52 :: str
-    r53 :: union[int, str]
+    r32 :: bool
+    r33 :: object
+    r34, x_3 :: str
+    r35 :: i32
+    r36, r37, r38 :: bit
+    r39 :: dict
+    r40 :: short_int
+    r41 :: native_int
+    r42 :: object
+    r43 :: tuple[bool, short_int, object, object]
+    r44 :: short_int
+    r45 :: bool
+    r46, r47 :: object
+    r48 :: str
+    r49 :: union[int, str]
     k :: str
     v :: union[int, str]
-    r54 :: i32
-    r55, r56, r57 :: bit
+    r50 :: i32
+    r51, r52, r53 :: bit
 L0:
     r0 = PyList_New(0)
     r1 = 0
     r2 = PyDict_Size(m)
-    r3 = r2 << 1
-    r4 = CPyDict_GetKeysIter(m)
+    r3 = CPyDict_GetKeysIter(m)
 L1:
-    r5 = CPyDict_NextKey(r4, r1)
-    r6 = r5[1]
-    r1 = r6
-    r7 = r5[0]
-    if r7 goto L2 else goto L4 :: bool
+    r4 = CPyDict_NextKey(r3, r1)
+    r5 = r4[1]
+    r1 = r5
+    r6 = r4[0]
+    if r6 goto L2 else goto L4 :: bool
 L2:
-    r8 = r5[2]
-    r9 = cast(str, r8)
-    x = r9
-    r10 = PyList_Append(r0, x)
-    r11 = r10 >= 0 :: signed
+    r7 = r4[2]
+    r8 = cast(str, r7)
+    x = r8
+    r9 = PyList_Append(r0, x)
+    r10 = r9 >= 0 :: signed
 L3:
-    r12 = CPyDict_CheckSize(m, r3)
+    r11 = CPyDict_CheckSize(m, r2)
     goto L1
 L4:
-    r13 = CPy_NoErrOccurred()
+    r12 = CPy_NoErrOccurred()
 L5:
-    r14 = PyList_New(0)
-    r15 = 0
-    r16 = PyDict_Size(m)
-    r17 = r16 << 1
-    r18 = CPyDict_GetValuesIter(m)
+    r13 = PyList_New(0)
+    r14 = 0
+    r15 = PyDict_Size(m)
+    r16 = CPyDict_GetValuesIter(m)
 L6:
-    r19 = CPyDict_NextValue(r18, r15)
-    r20 = r19[1]
-    r15 = r20
-    r21 = r19[0]
-    if r21 goto L7 else goto L9 :: bool
+    r17 = CPyDict_NextValue(r16, r14)
+    r18 = r17[1]
+    r14 = r18
+    r19 = r17[0]
+    if r19 goto L7 else goto L9 :: bool
 L7:
-    r22 = r19[2]
-    r23 = cast(union[int, str], r22)
-    x_2 = r23
-    r24 = PyList_Append(r14, x_2)
-    r25 = r24 >= 0 :: signed
+    r20 = r17[2]
+    r21 = cast(union[int, str], r20)
+    x_2 = r21
+    r22 = PyList_Append(r13, x_2)
+    r23 = r22 >= 0 :: signed
 L8:
-    r26 = CPyDict_CheckSize(m, r17)
+    r24 = CPyDict_CheckSize(m, r15)
     goto L6
 L9:
-    r27 = CPy_NoErrOccurred()
+    r25 = CPy_NoErrOccurred()
 L10:
-    r28 = PySet_New(0)
-    r29 = 0
-    r30 = PyDict_Size(m)
-    r31 = r30 << 1
-    r32 = CPyDict_GetKeysIter(m)
+    r26 = PySet_New(0)
+    r27 = 0
+    r28 = PyDict_Size(m)
+    r29 = CPyDict_GetKeysIter(m)
 L11:
-    r33 = CPyDict_NextKey(r32, r29)
-    r34 = r33[1]
-    r29 = r34
-    r35 = r33[0]
-    if r35 goto L12 else goto L14 :: bool
+    r30 = CPyDict_NextKey(r29, r27)
+    r31 = r30[1]
+    r27 = r31
+    r32 = r30[0]
+    if r32 goto L12 else goto L14 :: bool
 L12:
-    r36 = r33[2]
-    r37 = cast(str, r36)
-    x_3 = r37
-    r38 = PySet_Add(r28, x_3)
-    r39 = r38 >= 0 :: signed
+    r33 = r30[2]
+    r34 = cast(str, r33)
+    x_3 = r34
+    r35 = PySet_Add(r26, x_3)
+    r36 = r35 >= 0 :: signed
 L13:
-    r40 = CPyDict_CheckSize(m, r31)
+    r37 = CPyDict_CheckSize(m, r28)
     goto L11
 L14:
-    r41 = CPy_NoErrOccurred()
+    r38 = CPy_NoErrOccurred()
 L15:
-    r42 = PyDict_New()
-    r43 = 0
-    r44 = PyDict_Size(m)
-    r45 = r44 << 1
-    r46 = CPyDict_GetItemsIter(m)
+    r39 = PyDict_New()
+    r40 = 0
+    r41 = PyDict_Size(m)
+    r42 = CPyDict_GetItemsIter(m)
 L16:
-    r47 = CPyDict_NextItem(r46, r43)
-    r48 = r47[1]
-    r43 = r48
-    r49 = r47[0]
-    if r49 goto L17 else goto L19 :: bool
+    r43 = CPyDict_NextItem(r42, r40)
+    r44 = r43[1]
+    r40 = r44
+    r45 = r43[0]
+    if r45 goto L17 else goto L19 :: bool
 L17:
-    r50 = r47[2]
-    r51 = r47[3]
-    r52 = cast(str, r50)
-    r53 = cast(union[int, str], r51)
-    k = r52
-    v = r53
-    r54 = CPyDict_SetItem(r42, k, v)
-    r55 = r54 >= 0 :: signed
+    r46 = r43[2]
+    r47 = r43[3]
+    r48 = cast(str, r46)
+    r49 = cast(union[int, str], r47)
+    k = r48
+    v = r49
+    r50 = PyDict_SetItem(r39, k, v)
+    r51 = r50 >= 0 :: signed
 L18:
-    r56 = CPyDict_CheckSize(m, r45)
+    r52 = CPyDict_CheckSize(m, r41)
     goto L16
 L19:
-    r57 = CPy_NoErrOccurred()
+    r53 = CPy_NoErrOccurred()
 L20:
     return 1
 def fn_typeddict(t):
@@ -530,144 +503,136 @@ def fn_typeddict(t):
     r0 :: list
     r1 :: short_int
     r2 :: native_int
-    r3 :: short_int
-    r4 :: object
-    r5 :: tuple[bool, short_int, object]
-    r6 :: short_int
-    r7 :: bool
-    r8 :: object
-    r9, x :: str
-    r10 :: i32
-    r11, r12, r13 :: bit
-    r14 :: list
-    r15 :: short_int
-    r16 :: native_int
-    r17 :: short_int
-    r18 :: object
-    r19 :: tuple[bool, short_int, object]
-    r20 :: short_int
-    r21 :: bool
-    r22, x_2 :: object
-    r23 :: i32
-    r24, r25, r26 :: bit
-    r27 :: set
-    r28 :: short_int
-    r29 :: native_int
+    r3 :: object
+    r4 :: tuple[bool, short_int, object]
+    r5 :: short_int
+    r6 :: bool
+    r7 :: object
+    r8, x :: str
+    r9 :: i32
+    r10, r11, r12 :: bit
+    r13 :: list
+    r14 :: short_int
+    r15 :: native_int
+    r16 :: object
+    r17 :: tuple[bool, short_int, object]
+    r18 :: short_int
+    r19 :: bool
+    r20, x_2 :: object
+    r21 :: i32
+    r22, r23, r24 :: bit
+    r25 :: set
+    r26 :: short_int
+    r27 :: native_int
+    r28 :: object
+    r29 :: tuple[bool, short_int, object]
     r30 :: short_int
-    r31 :: object
-    r32 :: tuple[bool, short_int, object]
-    r33 :: short_int
-    r34 :: bool
-    r35 :: object
-    r36, x_3 :: str
-    r37 :: i32
-    r38, r39, r40 :: bit
-    r41 :: dict
-    r42 :: short_int
-    r43 :: native_int
-    r44 :: short_int
-    r45 :: object
-    r46 :: tuple[bool, short_int, object, object]
-    r47 :: short_int
-    r48 :: bool
-    r49, r50 :: object
-    r51, k :: str
+    r31 :: bool
+    r32 :: object
+    r33, x_3 :: str
+    r34 :: i32
+    r35, r36, r37 :: bit
+    r38 :: dict
+    r39 :: short_int
+    r40 :: native_int
+    r41 :: object
+    r42 :: tuple[bool, short_int, object, object]
+    r43 :: short_int
+    r44 :: bool
+    r45, r46 :: object
+    r47, k :: str
     v :: object
-    r52 :: i32
-    r53, r54, r55 :: bit
+    r48 :: i32
+    r49, r50, r51 :: bit
 L0:
     r0 = PyList_New(0)
     r1 = 0
     r2 = PyDict_Size(t)
-    r3 = r2 << 1
-    r4 = CPyDict_GetKeysIter(t)
+    r3 = CPyDict_GetKeysIter(t)
 L1:
-    r5 = CPyDict_NextKey(r4, r1)
-    r6 = r5[1]
-    r1 = r6
-    r7 = r5[0]
-    if r7 goto L2 else goto L4 :: bool
+    r4 = CPyDict_NextKey(r3, r1)
+    r5 = r4[1]
+    r1 = r5
+    r6 = r4[0]
+    if r6 goto L2 else goto L4 :: bool
 L2:
-    r8 = r5[2]
-    r9 = cast(str, r8)
-    x = r9
-    r10 = PyList_Append(r0, x)
-    r11 = r10 >= 0 :: signed
+    r7 = r4[2]
+    r8 = cast(str, r7)
+    x = r8
+    r9 = PyList_Append(r0, x)
+    r10 = r9 >= 0 :: signed
 L3:
-    r12 = CPyDict_CheckSize(t, r3)
+    r11 = CPyDict_CheckSize(t, r2)
     goto L1
 L4:
-    r13 = CPy_NoErrOccurred()
+    r12 = CPy_NoErrOccurred()
 L5:
-    r14 = PyList_New(0)
-    r15 = 0
-    r16 = PyDict_Size(t)
-    r17 = r16 << 1
-    r18 = CPyDict_GetValuesIter(t)
+    r13 = PyList_New(0)
+    r14 = 0
+    r15 = PyDict_Size(t)
+    r16 = CPyDict_GetValuesIter(t)
 L6:
-    r19 = CPyDict_NextValue(r18, r15)
-    r20 = r19[1]
-    r15 = r20
-    r21 = r19[0]
-    if r21 goto L7 else goto L9 :: bool
+    r17 = CPyDict_NextValue(r16, r14)
+    r18 = r17[1]
+    r14 = r18
+    r19 = r17[0]
+    if r19 goto L7 else goto L9 :: bool
 L7:
-    r22 = r19[2]
-    x_2 = r22
-    r23 = PyList_Append(r14, x_2)
-    r24 = r23 >= 0 :: signed
+    r20 = r17[2]
+    x_2 = r20
+    r21 = PyList_Append(r13, x_2)
+    r22 = r21 >= 0 :: signed
 L8:
-    r25 = CPyDict_CheckSize(t, r17)
+    r23 = CPyDict_CheckSize(t, r15)
     goto L6
 L9:
-    r26 = CPy_NoErrOccurred()
+    r24 = CPy_NoErrOccurred()
 L10:
-    r27 = PySet_New(0)
-    r28 = 0
-    r29 = PyDict_Size(t)
-    r30 = r29 << 1
-    r31 = CPyDict_GetKeysIter(t)
+    r25 = PySet_New(0)
+    r26 = 0
+    r27 = PyDict_Size(t)
+    r28 = CPyDict_GetKeysIter(t)
 L11:
-    r32 = CPyDict_NextKey(r31, r28)
-    r33 = r32[1]
-    r28 = r33
-    r34 = r32[0]
-    if r34 goto L12 else goto L14 :: bool
+    r29 = CPyDict_NextKey(r28, r26)
+    r30 = r29[1]
+    r26 = r30
+    r31 = r29[0]
+    if r31 goto L12 else goto L14 :: bool
 L12:
-    r35 = r32[2]
-    r36 = cast(str, r35)
-    x_3 = r36
-    r37 = PySet_Add(r27, x_3)
-    r38 = r37 >= 0 :: signed
+    r32 = r29[2]
+    r33 = cast(str, r32)
+    x_3 = r33
+    r34 = PySet_Add(r25, x_3)
+    r35 = r34 >= 0 :: signed
 L13:
-    r39 = CPyDict_CheckSize(t, r30)
+    r36 = CPyDict_CheckSize(t, r27)
     goto L11
 L14:
-    r40 = CPy_NoErrOccurred()
+    r37 = CPy_NoErrOccurred()
 L15:
-    r41 = PyDict_New()
-    r42 = 0
-    r43 = PyDict_Size(t)
-    r44 = r43 << 1
-    r45 = CPyDict_GetItemsIter(t)
+    r38 = PyDict_New()
+    r39 = 0
+    r40 = PyDict_Size(t)
+    r41 = CPyDict_GetItemsIter(t)
 L16:
-    r46 = CPyDict_NextItem(r45, r42)
-    r47 = r46[1]
-    r42 = r47
-    r48 = r46[0]
-    if r48 goto L17 else goto L19 :: bool
+    r42 = CPyDict_NextItem(r41, r39)
+    r43 = r42[1]
+    r39 = r43
+    r44 = r42[0]
+    if r44 goto L17 else goto L19 :: bool
 L17:
-    r49 = r46[2]
-    r50 = r46[3]
-    r51 = cast(str, r49)
-    k = r51
-    v = r50
-    r52 = CPyDict_SetItem(r41, k, v)
-    r53 = r52 >= 0 :: signed
+    r45 = r42[2]
+    r46 = r42[3]
+    r47 = cast(str, r45)
+    k = r47
+    v = r46
+    r48 = PyDict_SetItem(r38, k, v)
+    r49 = r48 >= 0 :: signed
 L18:
-    r54 = CPyDict_CheckSize(t, r44)
+    r50 = CPyDict_CheckSize(t, r40)
     goto L16
 L19:
-    r55 = CPy_NoErrOccurred()
+    r51 = CPy_NoErrOccurred()
 L20:
     return 1
 
@@ -713,100 +678,84 @@ def inner_deco_obj.__call__(__mypyc_self__, args, kwargs):
     r0 :: __main__.deco_env
     r1 :: native_int
     r2 :: list
-    r3 :: short_int
-    r4 :: native_int
-    r5 :: short_int
-    r6 :: bit
-    r7, x :: object
-    r8 :: bit
-    r9 :: short_int
+    r3, r4 :: native_int
+    r5 :: bit
+    r6, x :: object
+    r7 :: native_int
     can_listcomp :: list
-    r10 :: dict
-    r11 :: short_int
-    r12 :: native_int
+    r8 :: dict
+    r9 :: short_int
+    r10 :: native_int
+    r11 :: object
+    r12 :: tuple[bool, short_int, object, object]
     r13 :: short_int
-    r14 :: object
-    r15 :: tuple[bool, short_int, object, object]
-    r16 :: short_int
-    r17 :: bool
-    r18, r19 :: object
-    r20, k :: str
+    r14 :: bool
+    r15, r16 :: object
+    r17, k :: str
     v :: object
-    r21 :: i32
-    r22, r23, r24 :: bit
+    r18 :: i32
+    r19, r20, r21 :: bit
     can_dictcomp :: dict
-    r25, can_iter, r26, can_use_keys, r27, can_use_values :: list
-    r28 :: object
-    r29 :: list
-    r30 :: object
-    r31 :: dict
-    r32 :: i32
-    r33 :: bit
-    r34 :: tuple
-    r35 :: object
-    r36 :: int
+    r22, can_iter, r23, can_use_keys, r24, can_use_values :: list
+    r25 :: object
+    r26 :: dict
+    r27 :: object
+    r28 :: int
 L0:
     r0 = __mypyc_self__.__mypyc_env__
     r1 = var_object_size args
     r2 = PyList_New(r1)
-    r3 = 0
+    r3 = var_object_size args
+    r4 = 0
 L1:
-    r4 = var_object_size args
-    r5 = r4 << 1
-    r6 = int_lt r3, r5
-    if r6 goto L2 else goto L4 :: bool
+    r5 = r4 < r3 :: signed
+    if r5 goto L2 else goto L4 :: bool
 L2:
-    r7 = CPySequenceTuple_GetItem(args, r3)
-    x = r7
-    r8 = CPyList_SetItemUnsafe(r2, r3, x)
+    r6 = CPySequenceTuple_GetItemUnsafe(args, r4)
+    x = r6
+    CPyList_SetItemUnsafe(r2, r4, x)
 L3:
-    r9 = r3 + 2
-    r3 = r9
+    r7 = r4 + 1
+    r4 = r7
     goto L1
 L4:
     can_listcomp = r2
-    r10 = PyDict_New()
-    r11 = 0
-    r12 = PyDict_Size(kwargs)
-    r13 = r12 << 1
-    r14 = CPyDict_GetItemsIter(kwargs)
+    r8 = PyDict_New()
+    r9 = 0
+    r10 = PyDict_Size(kwargs)
+    r11 = CPyDict_GetItemsIter(kwargs)
 L5:
-    r15 = CPyDict_NextItem(r14, r11)
-    r16 = r15[1]
-    r11 = r16
-    r17 = r15[0]
-    if r17 goto L6 else goto L8 :: bool
+    r12 = CPyDict_NextItem(r11, r9)
+    r13 = r12[1]
+    r9 = r13
+    r14 = r12[0]
+    if r14 goto L6 else goto L8 :: bool
 L6:
-    r18 = r15[2]
-    r19 = r15[3]
-    r20 = cast(str, r18)
-    k = r20
-    v = r19
-    r21 = CPyDict_SetItem(r10, k, v)
-    r22 = r21 >= 0 :: signed
+    r15 = r12[2]
+    r16 = r12[3]
+    r17 = cast(str, r15)
+    k = r17
+    v = r16
+    r18 = PyDict_SetItem(r8, k, v)
+    r19 = r18 >= 0 :: signed
 L7:
-    r23 = CPyDict_CheckSize(kwargs, r13)
+    r20 = CPyDict_CheckSize(kwargs, r10)
     goto L5
 L8:
-    r24 = CPy_NoErrOccurred()
+    r21 = CPy_NoErrOccurred()
 L9:
-    can_dictcomp = r10
-    r25 = PySequence_List(kwargs)
-    can_iter = r25
-    r26 = CPyDict_Keys(kwargs)
-    can_use_keys = r26
-    r27 = CPyDict_Values(kwargs)
-    can_use_values = r27
-    r28 = r0.func
-    r29 = PyList_New(0)
-    r30 = CPyList_Extend(r29, args)
-    r31 = PyDict_New()
-    r32 = CPyDict_UpdateInDisplay(r31, kwargs)
-    r33 = r32 >= 0 :: signed
-    r34 = PyList_AsTuple(r29)
-    r35 = PyObject_Call(r28, r34, r31)
-    r36 = unbox(int, r35)
-    return r36
+    can_dictcomp = r8
+    r22 = PySequence_List(kwargs)
+    can_iter = r22
+    r23 = CPyDict_Keys(kwargs)
+    can_use_keys = r23
+    r24 = CPyDict_Values(kwargs)
+    can_use_values = r24
+    r25 = r0.func
+    r26 = PyDict_Copy(kwargs)
+    r27 = PyObject_Call(r25, args, r26)
+    r28 = unbox(int, r27)
+    return r28
 def deco(func):
     func :: object
     r0 :: __main__.deco_env
diff --git a/mypyc/test-data/irbuild-i64.test b/mypyc/test-data/irbuild-i64.test
index c59e306b09df..e55c3bfe2acc 100644
--- a/mypyc/test-data/irbuild-i64.test
+++ b/mypyc/test-data/irbuild-i64.test
@@ -2046,27 +2046,21 @@ L2:
     return r6
 def narrow2(x):
     x :: union[__main__.C, i64]
-    r0 :: object
-    r1 :: i32
-    r2 :: bit
-    r3 :: bool
-    r4 :: i64
-    r5 :: __main__.C
-    r6 :: i64
+    r0 :: bit
+    r1 :: i64
+    r2 :: __main__.C
+    r3 :: i64
 L0:
-    r0 = load_address PyLong_Type
-    r1 = PyObject_IsInstance(x, r0)
-    r2 = r1 >= 0 :: signed
-    r3 = truncate r1: i32 to builtins.bool
-    if r3 goto L1 else goto L2 :: bool
+    r0 = PyLong_Check(x)
+    if r0 goto L1 else goto L2 :: bool
 L1:
-    r4 = unbox(i64, x)
-    return r4
+    r1 = unbox(i64, x)
+    return r1
 L2:
-    r5 = borrow cast(__main__.C, x)
-    r6 = r5.a
+    r2 = borrow cast(__main__.C, x)
+    r3 = r2.a
     keep_alive x
-    return r6
+    return r3
 
 [case testI64ConvertBetweenTuples_64bit]
 from __future__ import annotations
diff --git a/mypyc/test-data/irbuild-isinstance.test b/mypyc/test-data/irbuild-isinstance.test
index 78da2e9c1e19..0df9448b819f 100644
--- a/mypyc/test-data/irbuild-isinstance.test
+++ b/mypyc/test-data/irbuild-isinstance.test
@@ -4,16 +4,11 @@ def is_int(value: object) -> bool:
 
 [out]
 def is_int(value):
-    value, r0 :: object
-    r1 :: i32
-    r2 :: bit
-    r3 :: bool
+    value :: object
+    r0 :: bit
 L0:
-    r0 = load_address PyLong_Type
-    r1 = PyObject_IsInstance(value, r0)
-    r2 = r1 >= 0 :: signed
-    r3 = truncate r1: i32 to builtins.bool
-    return r3
+    r0 = PyLong_Check(value)
+    return r0
 
 [case testIsinstanceNotBool1]
 def is_not_bool(value: object) -> bool:
@@ -21,17 +16,12 @@ def is_not_bool(value: object) -> bool:
 
 [out]
 def is_not_bool(value):
-    value, r0 :: object
-    r1 :: i32
-    r2 :: bit
-    r3, r4 :: bool
+    value :: object
+    r0, r1 :: bit
 L0:
-    r0 = load_address PyBool_Type
-    r1 = PyObject_IsInstance(value, r0)
-    r2 = r1 >= 0 :: signed
-    r3 = truncate r1: i32 to builtins.bool
-    r4 = r3 ^ 1
-    return r4
+    r0 = PyBool_Check(value)
+    r1 = r0 ^ 1
+    return r1
 
 [case testIsinstanceIntAndNotBool]
 # This test is to ensure that 'value' doesn't get coerced to int when we are
@@ -41,32 +31,22 @@ def is_not_bool_and_is_int(value: object) -> bool:
 
 [out]
 def is_not_bool_and_is_int(value):
-    value, r0 :: object
-    r1 :: i32
-    r2 :: bit
-    r3, r4 :: bool
-    r5 :: object
-    r6 :: i32
-    r7 :: bit
-    r8, r9 :: bool
+    value :: object
+    r0 :: bit
+    r1 :: bool
+    r2, r3 :: bit
 L0:
-    r0 = load_address PyLong_Type
-    r1 = PyObject_IsInstance(value, r0)
-    r2 = r1 >= 0 :: signed
-    r3 = truncate r1: i32 to builtins.bool
-    if r3 goto L2 else goto L1 :: bool
+    r0 = PyLong_Check(value)
+    if r0 goto L2 else goto L1 :: bool
 L1:
-    r4 = r3
+    r1 = r0
     goto L3
 L2:
-    r5 = load_address PyBool_Type
-    r6 = PyObject_IsInstance(value, r5)
-    r7 = r6 >= 0 :: signed
-    r8 = truncate r6: i32 to builtins.bool
-    r9 = r8 ^ 1
-    r4 = r9
+    r2 = PyBool_Check(value)
+    r3 = r2 ^ 1
+    r1 = r3
 L3:
-    return r4
+    return r1
 
 [case testBorrowSpecialCaseWithIsinstance]
 class C:
@@ -97,7 +77,7 @@ L0:
     x = r0
     r1 = __main__.C :: type
     r2 = get_element_ptr x ob_type :: PyObject
-    r3 = load_mem r2 :: builtins.object*
+    r3 = borrow load_mem r2 :: builtins.object*
     keep_alive x
     r4 = r3 == r1
     if r4 goto L1 else goto L2 :: bool
@@ -107,3 +87,105 @@ L1:
     keep_alive x
 L2:
     return 1
+
+[case testBytes]
+from typing import Any
+
+def is_bytes(x: Any) -> bool:
+    return isinstance(x, bytes)
+
+def is_bytearray(x: Any) -> bool:
+    return isinstance(x, bytearray)
+
+[out]
+def is_bytes(x):
+    x :: object
+    r0 :: bit
+L0:
+    r0 = PyBytes_Check(x)
+    return r0
+def is_bytearray(x):
+    x :: object
+    r0 :: bit
+L0:
+    r0 = PyByteArray_Check(x)
+    return r0
+
+[case testDict]
+from typing import Any
+
+def is_dict(x: Any) -> bool:
+    return isinstance(x, dict)
+
+[out]
+def is_dict(x):
+    x :: object
+    r0 :: bit
+L0:
+    r0 = PyDict_Check(x)
+    return r0
+
+[case testFloat]
+from typing import Any
+
+def is_float(x: Any) -> bool:
+    return isinstance(x, float)
+
+[out]
+def is_float(x):
+    x :: object
+    r0 :: bit
+L0:
+    r0 = PyFloat_Check(x)
+    return r0
+
+[case testSet]
+from typing import Any
+
+def is_set(x: Any) -> bool:
+    return isinstance(x, set)
+
+def is_frozenset(x: Any) -> bool:
+    return isinstance(x, frozenset)
+
+[out]
+def is_set(x):
+    x :: object
+    r0 :: bit
+L0:
+    r0 = PySet_Check(x)
+    return r0
+def is_frozenset(x):
+    x :: object
+    r0 :: bit
+L0:
+    r0 = PyFrozenSet_Check(x)
+    return r0
+
+[case testStr]
+from typing import Any
+
+def is_str(x: Any) -> bool:
+    return isinstance(x, str)
+
+[out]
+def is_str(x):
+    x :: object
+    r0 :: bit
+L0:
+    r0 = PyUnicode_Check(x)
+    return r0
+
+[case testTuple]
+from typing import Any
+
+def is_tuple(x: Any) -> bool:
+    return isinstance(x, tuple)
+
+[out]
+def is_tuple(x):
+    x :: object
+    r0 :: bit
+L0:
+    r0 = PyTuple_Check(x)
+    return r0
diff --git a/mypyc/test-data/irbuild-lists.test b/mypyc/test-data/irbuild-lists.test
index 2435b5aee350..d83fb88390db 100644
--- a/mypyc/test-data/irbuild-lists.test
+++ b/mypyc/test-data/irbuild-lists.test
@@ -220,6 +220,18 @@ L0:
     r1 = r0 << 1
     return r1
 
+[case testListClear]
+from typing import List
+def f(l: List[int]) -> None:
+    return l.clear()
+[out]
+def f(l):
+    l :: list
+    r0 :: bit
+L0:
+    r0 = CPyList_Clear(l)
+    return 1
+
 [case testListCopy]
 from typing import List
 from typing import Any
@@ -359,27 +371,21 @@ def f(source):
     source :: list
     r0 :: native_int
     r1 :: list
-    r2 :: short_int
-    r3 :: native_int
-    r4 :: short_int
-    r5 :: bit
-    r6 :: object
-    r7, x, r8 :: int
-    r9 :: object
-    r10 :: bit
-    r11 :: short_int
+    r2, r3 :: native_int
+    r4 :: bit
+    r5 :: object
+    r6, x, r7 :: int
+    r8 :: object
+    r9 :: native_int
     a :: list
-    r12 :: native_int
-    r13 :: list
-    r14 :: short_int
-    r15 :: native_int
-    r16 :: short_int
-    r17 :: bit
+    r10 :: native_int
+    r11 :: list
+    r12, r13 :: native_int
+    r14 :: bit
+    r15 :: object
+    r16, x_2, r17 :: int
     r18 :: object
-    r19, x_2, r20 :: int
-    r21 :: object
-    r22 :: bit
-    r23 :: short_int
+    r19 :: native_int
     b :: list
 L0:
     r0 = var_object_size source
@@ -387,43 +393,41 @@ L0:
     r2 = 0
 L1:
     r3 = var_object_size source
-    r4 = r3 << 1
-    r5 = int_lt r2, r4
-    if r5 goto L2 else goto L4 :: bool
+    r4 = r2 < r3 :: signed
+    if r4 goto L2 else goto L4 :: bool
 L2:
-    r6 = list_get_item_unsafe source, r2
-    r7 = unbox(int, r6)
-    x = r7
-    r8 = CPyTagged_Add(x, 2)
-    r9 = box(int, r8)
-    r10 = CPyList_SetItemUnsafe(r1, r2, r9)
+    r5 = list_get_item_unsafe source, r2
+    r6 = unbox(int, r5)
+    x = r6
+    r7 = CPyTagged_Add(x, 2)
+    r8 = box(int, r7)
+    CPyList_SetItemUnsafe(r1, r2, r8)
 L3:
-    r11 = r2 + 2
-    r2 = r11
+    r9 = r2 + 1
+    r2 = r9
     goto L1
 L4:
     a = r1
-    r12 = var_object_size source
-    r13 = PyList_New(r12)
-    r14 = 0
+    r10 = var_object_size source
+    r11 = PyList_New(r10)
+    r12 = 0
 L5:
-    r15 = var_object_size source
-    r16 = r15 << 1
-    r17 = int_lt r14, r16
-    if r17 goto L6 else goto L8 :: bool
+    r13 = var_object_size source
+    r14 = r12 < r13 :: signed
+    if r14 goto L6 else goto L8 :: bool
 L6:
-    r18 = list_get_item_unsafe source, r14
-    r19 = unbox(int, r18)
-    x_2 = r19
-    r20 = CPyTagged_Add(x_2, 2)
-    r21 = box(int, r20)
-    r22 = CPyList_SetItemUnsafe(r13, r14, r21)
+    r15 = list_get_item_unsafe source, r12
+    r16 = unbox(int, r15)
+    x_2 = r16
+    r17 = CPyTagged_Add(x_2, 2)
+    r18 = box(int, r17)
+    CPyList_SetItemUnsafe(r11, r12, r18)
 L7:
-    r23 = r14 + 2
-    r14 = r23
+    r19 = r12 + 1
+    r12 = r19
     goto L5
 L8:
-    b = r13
+    b = r11
     return 1
 
 [case testGeneratorNext]
@@ -434,40 +438,37 @@ def test(x: List[int]) -> None:
 [out]
 def test(x):
     x :: list
-    r0 :: short_int
-    r1 :: native_int
-    r2 :: short_int
-    r3 :: bit
-    r4 :: object
-    r5, i :: int
-    r6 :: object
-    r7 :: union[int, None]
-    r8 :: short_int
-    r9 :: object
+    r0, r1 :: native_int
+    r2 :: bit
+    r3 :: object
+    r4, i :: int
+    r5 :: object
+    r6 :: union[int, None]
+    r7 :: native_int
+    r8 :: object
     res :: union[int, None]
 L0:
     r0 = 0
 L1:
     r1 = var_object_size x
-    r2 = r1 << 1
-    r3 = int_lt r0, r2
-    if r3 goto L2 else goto L4 :: bool
+    r2 = r0 < r1 :: signed
+    if r2 goto L2 else goto L4 :: bool
 L2:
-    r4 = list_get_item_unsafe x, r0
-    r5 = unbox(int, r4)
-    i = r5
-    r6 = box(int, i)
-    r7 = r6
+    r3 = list_get_item_unsafe x, r0
+    r4 = unbox(int, r3)
+    i = r4
+    r5 = box(int, i)
+    r6 = r5
     goto L5
 L3:
-    r8 = r0 + 2
-    r0 = r8
+    r7 = r0 + 1
+    r0 = r7
     goto L1
 L4:
-    r9 = box(None, 1)
-    r7 = r9
+    r8 = box(None, 1)
+    r6 = r8
 L5:
-    res = r7
+    res = r6
     return 1
 
 [case testSimplifyListUnion]
@@ -486,78 +487,66 @@ def nested_union(a: Union[List[str], List[Optional[str]]]) -> None:
 [out]
 def narrow(a):
     a :: union[list, int]
-    r0 :: object
-    r1 :: i32
-    r2 :: bit
-    r3 :: bool
-    r4 :: list
-    r5 :: native_int
-    r6 :: short_int
-    r7 :: int
+    r0 :: bit
+    r1 :: list
+    r2 :: native_int
+    r3 :: short_int
+    r4 :: int
 L0:
-    r0 = load_address PyList_Type
-    r1 = PyObject_IsInstance(a, r0)
-    r2 = r1 >= 0 :: signed
-    r3 = truncate r1: i32 to builtins.bool
-    if r3 goto L1 else goto L2 :: bool
+    r0 = PyList_Check(a)
+    if r0 goto L1 else goto L2 :: bool
 L1:
-    r4 = borrow cast(list, a)
-    r5 = var_object_size r4
-    r6 = r5 << 1
+    r1 = borrow cast(list, a)
+    r2 = var_object_size r1
+    r3 = r2 << 1
     keep_alive a
-    return r6
+    return r3
 L2:
-    r7 = unbox(int, a)
-    return r7
+    r4 = unbox(int, a)
+    return r4
 def loop(a):
     a :: list
-    r0 :: short_int
-    r1 :: native_int
-    r2 :: short_int
-    r3 :: bit
-    r4 :: object
-    r5, x :: union[str, bytes]
-    r6 :: short_int
+    r0, r1 :: native_int
+    r2 :: bit
+    r3 :: object
+    r4, x :: union[str, bytes]
+    r5 :: native_int
 L0:
     r0 = 0
 L1:
     r1 = var_object_size a
-    r2 = r1 << 1
-    r3 = int_lt r0, r2
-    if r3 goto L2 else goto L4 :: bool
+    r2 = r0 < r1 :: signed
+    if r2 goto L2 else goto L4 :: bool
 L2:
-    r4 = list_get_item_unsafe a, r0
-    r5 = cast(union[str, bytes], r4)
-    x = r5
+    r3 = list_get_item_unsafe a, r0
+    r4 = cast(union[str, bytes], r3)
+    x = r4
 L3:
-    r6 = r0 + 2
-    r0 = r6
+    r5 = r0 + 1
+    r0 = r5
     goto L1
 L4:
     return 1
 def nested_union(a):
     a :: list
-    r0 :: short_int
-    r1 :: native_int
-    r2 :: short_int
-    r3 :: bit
-    r4 :: object
-    r5, x :: union[str, None]
-    r6 :: short_int
+    r0, r1 :: native_int
+    r2 :: bit
+    r3 :: object
+    r4, x :: union[str, None]
+    r5 :: native_int
 L0:
     r0 = 0
 L1:
     r1 = var_object_size a
-    r2 = r1 << 1
-    r3 = int_lt r0, r2
-    if r3 goto L2 else goto L4 :: bool
+    r2 = r0 < r1 :: signed
+    if r2 goto L2 else goto L4 :: bool
 L2:
-    r4 = list_get_item_unsafe a, r0
-    r5 = cast(union[str, None], r4)
-    x = r5
+    r3 = list_get_item_unsafe a, r0
+    r4 = cast(union[str, None], r3)
+    x = r4
 L3:
-    r6 = r0 + 2
-    r0 = r6
+    r5 = r0 + 1
+    r0 = r5
     goto L1
 L4:
     return 1
@@ -583,3 +572,357 @@ def sort_iterable(a):
 L0:
     r0 = CPySequence_Sort(a)
     return 1
+
+[case testListBuiltFromStr]
+def f2(val: str) -> str:
+    return val + "f2"
+
+def test() -> None:
+    source = "abc"
+    a = [f2(x) for x in source]
+[out]
+def f2(val):
+    val, r0, r1 :: str
+L0:
+    r0 = 'f2'
+    r1 = PyUnicode_Concat(val, r0)
+    return r1
+def test():
+    r0, source :: str
+    r1 :: native_int
+    r2 :: bit
+    r3 :: list
+    r4 :: native_int
+    r5 :: bit
+    r6 :: native_int
+    r7 :: bit
+    r8, x, r9 :: str
+    r10 :: native_int
+    a :: list
+L0:
+    r0 = 'abc'
+    source = r0
+    r1 = CPyStr_Size_size_t(source)
+    r2 = r1 >= 0 :: signed
+    r3 = PyList_New(r1)
+    r4 = CPyStr_Size_size_t(source)
+    r5 = r4 >= 0 :: signed
+    r6 = 0
+L1:
+    r7 = r6 < r4 :: signed
+    if r7 goto L2 else goto L4 :: bool
+L2:
+    r8 = CPyStr_GetItemUnsafe(source, r6)
+    x = r8
+    r9 = f2(x)
+    CPyList_SetItemUnsafe(r3, r6, r9)
+L3:
+    r10 = r6 + 1
+    r6 = r10
+    goto L1
+L4:
+    a = r3
+    return 1
+
+[case testListBuiltFromStrExpr]
+def f2(val: str) -> str:
+    return val + "f2"
+
+def test() -> None:
+    a = [f2(x) for x in "abc"]
+[out]
+def f2(val):
+    val, r0, r1 :: str
+L0:
+    r0 = 'f2'
+    r1 = PyUnicode_Concat(val, r0)
+    return r1
+def test():
+    r0 :: str
+    r1 :: native_int
+    r2 :: bit
+    r3 :: list
+    r4 :: native_int
+    r5 :: bit
+    r6 :: native_int
+    r7 :: bit
+    r8, x, r9 :: str
+    r10 :: native_int
+    a :: list
+L0:
+    r0 = 'abc'
+    r1 = CPyStr_Size_size_t(r0)
+    r2 = r1 >= 0 :: signed
+    r3 = PyList_New(r1)
+    r4 = CPyStr_Size_size_t(r0)
+    r5 = r4 >= 0 :: signed
+    r6 = 0
+L1:
+    r7 = r6 < r4 :: signed
+    if r7 goto L2 else goto L4 :: bool
+L2:
+    r8 = CPyStr_GetItemUnsafe(r0, r6)
+    x = r8
+    r9 = f2(x)
+    CPyList_SetItemUnsafe(r3, r6, r9)
+L3:
+    r10 = r6 + 1
+    r6 = r10
+    goto L1
+L4:
+    a = r3
+    return 1
+
+[case testListBuiltFromFinalStr]
+from typing import Final
+
+source: Final = "abc"
+
+def f2(val: str) -> str:
+    return val + "f2"
+
+def test() -> None:
+    a = [f2(x) for x in source]
+[out]
+def f2(val):
+    val, r0, r1 :: str
+L0:
+    r0 = 'f2'
+    r1 = PyUnicode_Concat(val, r0)
+    return r1
+def test():
+    r0 :: str
+    r1 :: native_int
+    r2 :: bit
+    r3 :: list
+    r4 :: native_int
+    r5 :: bit
+    r6 :: native_int
+    r7 :: bit
+    r8, x, r9 :: str
+    r10 :: native_int
+    a :: list
+L0:
+    r0 = 'abc'
+    r1 = CPyStr_Size_size_t(r0)
+    r2 = r1 >= 0 :: signed
+    r3 = PyList_New(r1)
+    r4 = CPyStr_Size_size_t(r0)
+    r5 = r4 >= 0 :: signed
+    r6 = 0
+L1:
+    r7 = r6 < r4 :: signed
+    if r7 goto L2 else goto L4 :: bool
+L2:
+    r8 = CPyStr_GetItemUnsafe(r0, r6)
+    x = r8
+    r9 = f2(x)
+    CPyList_SetItemUnsafe(r3, r6, r9)
+L3:
+    r10 = r6 + 1
+    r6 = r10
+    goto L1
+L4:
+    a = r3
+    return 1
+
+[case testListBuiltFromBytes_64bit]
+def f2(val: int) -> int:
+    return val + 2
+
+def test() -> None:
+    source = b"abc"
+    a = [f2(x) for x in source]
+
+[out]
+def f2(val):
+    val, r0 :: int
+L0:
+    r0 = CPyTagged_Add(val, 4)
+    return r0
+def test():
+    r0, source :: bytes
+    r1 :: native_int
+    r2 :: list
+    r3, r4 :: native_int
+    r5, r6, r7 :: bit
+    r8, r9, r10, r11 :: int
+    r12 :: object
+    r13, x, r14 :: int
+    r15 :: object
+    r16 :: native_int
+    a :: list
+L0:
+    r0 = b'abc'
+    source = r0
+    r1 = var_object_size source
+    r2 = PyList_New(r1)
+    r3 = var_object_size source
+    r4 = 0
+L1:
+    r5 = r4 < r3 :: signed
+    if r5 goto L2 else goto L8 :: bool
+L2:
+    r6 = r4 <= 4611686018427387903 :: signed
+    if r6 goto L3 else goto L4 :: bool
+L3:
+    r7 = r4 >= -4611686018427387904 :: signed
+    if r7 goto L5 else goto L4 :: bool
+L4:
+    r8 = CPyTagged_FromInt64(r4)
+    r9 = r8
+    goto L6
+L5:
+    r10 = r4 << 1
+    r9 = r10
+L6:
+    r11 = CPyBytes_GetItem(source, r9)
+    r12 = box(int, r11)
+    r13 = unbox(int, r12)
+    x = r13
+    r14 = f2(x)
+    r15 = box(int, r14)
+    CPyList_SetItemUnsafe(r2, r4, r15)
+L7:
+    r16 = r4 + 1
+    r4 = r16
+    goto L1
+L8:
+    a = r2
+    return 1
+
+[case testListBuiltFromBytesExpr_64bit]
+def f2(val: int) -> int:
+    return val + 2
+
+def test() -> None:
+    a = [f2(x) for x in b"abc"]
+
+[out]
+def f2(val):
+    val, r0 :: int
+L0:
+    r0 = CPyTagged_Add(val, 4)
+    return r0
+def test():
+    r0 :: bytes
+    r1 :: native_int
+    r2 :: list
+    r3, r4 :: native_int
+    r5, r6, r7 :: bit
+    r8, r9, r10, r11 :: int
+    r12 :: object
+    r13, x, r14 :: int
+    r15 :: object
+    r16 :: native_int
+    a :: list
+L0:
+    r0 = b'abc'
+    r1 = var_object_size r0
+    r2 = PyList_New(r1)
+    r3 = var_object_size r0
+    r4 = 0
+L1:
+    r5 = r4 < r3 :: signed
+    if r5 goto L2 else goto L8 :: bool
+L2:
+    r6 = r4 <= 4611686018427387903 :: signed
+    if r6 goto L3 else goto L4 :: bool
+L3:
+    r7 = r4 >= -4611686018427387904 :: signed
+    if r7 goto L5 else goto L4 :: bool
+L4:
+    r8 = CPyTagged_FromInt64(r4)
+    r9 = r8
+    goto L6
+L5:
+    r10 = r4 << 1
+    r9 = r10
+L6:
+    r11 = CPyBytes_GetItem(r0, r9)
+    r12 = box(int, r11)
+    r13 = unbox(int, r12)
+    x = r13
+    r14 = f2(x)
+    r15 = box(int, r14)
+    CPyList_SetItemUnsafe(r2, r4, r15)
+L7:
+    r16 = r4 + 1
+    r4 = r16
+    goto L1
+L8:
+    a = r2
+    return 1
+
+[case testListBuiltFromFinalBytes_64bit]
+from typing import Final
+
+source: Final = b"abc"
+
+def f2(val: int) -> int:
+    return val + 2
+
+def test() -> None:
+    a = [f2(x) for x in source]
+
+[out]
+def f2(val):
+    val, r0 :: int
+L0:
+    r0 = CPyTagged_Add(val, 4)
+    return r0
+def test():
+    r0 :: bytes
+    r1 :: bool
+    r2 :: native_int
+    r3 :: list
+    r4, r5 :: native_int
+    r6, r7, r8 :: bit
+    r9, r10, r11, r12 :: int
+    r13 :: object
+    r14, x, r15 :: int
+    r16 :: object
+    r17 :: native_int
+    a :: list
+L0:
+    r0 = __main__.source :: static
+    if is_error(r0) goto L1 else goto L2
+L1:
+    r1 = raise NameError('value for final name "source" was not set')
+    unreachable
+L2:
+    r2 = var_object_size r0
+    r3 = PyList_New(r2)
+    r4 = var_object_size r0
+    r5 = 0
+L3:
+    r6 = r5 < r4 :: signed
+    if r6 goto L4 else goto L10 :: bool
+L4:
+    r7 = r5 <= 4611686018427387903 :: signed
+    if r7 goto L5 else goto L6 :: bool
+L5:
+    r8 = r5 >= -4611686018427387904 :: signed
+    if r8 goto L7 else goto L6 :: bool
+L6:
+    r9 = CPyTagged_FromInt64(r5)
+    r10 = r9
+    goto L8
+L7:
+    r11 = r5 << 1
+    r10 = r11
+L8:
+    r12 = CPyBytes_GetItem(r0, r10)
+    r13 = box(int, r12)
+    r14 = unbox(int, r13)
+    x = r14
+    r15 = f2(x)
+    r16 = box(int, r15)
+    CPyList_SetItemUnsafe(r3, r5, r16)
+L9:
+    r17 = r5 + 1
+    r5 = r17
+    goto L3
+L10:
+    a = r3
+    return 1
diff --git a/mypyc/test-data/irbuild-optional.test b/mypyc/test-data/irbuild-optional.test
index 75c008586999..fbf7cb148b08 100644
--- a/mypyc/test-data/irbuild-optional.test
+++ b/mypyc/test-data/irbuild-optional.test
@@ -251,28 +251,22 @@ def f(x: Union[int, A]) -> int:
 [out]
 def f(x):
     x :: union[int, __main__.A]
-    r0 :: object
-    r1 :: i32
-    r2 :: bit
-    r3 :: bool
-    r4, r5 :: int
-    r6 :: __main__.A
-    r7 :: int
+    r0 :: bit
+    r1, r2 :: int
+    r3 :: __main__.A
+    r4 :: int
 L0:
-    r0 = load_address PyLong_Type
-    r1 = PyObject_IsInstance(x, r0)
-    r2 = r1 >= 0 :: signed
-    r3 = truncate r1: i32 to builtins.bool
-    if r3 goto L1 else goto L2 :: bool
+    r0 = PyLong_Check(x)
+    if r0 goto L1 else goto L2 :: bool
 L1:
-    r4 = unbox(int, x)
-    r5 = CPyTagged_Add(r4, 2)
-    return r5
+    r1 = unbox(int, x)
+    r2 = CPyTagged_Add(r1, 2)
+    return r2
 L2:
-    r6 = borrow cast(__main__.A, x)
-    r7 = r6.a
+    r3 = borrow cast(__main__.A, x)
+    r4 = r3.a
     keep_alive x
-    return r7
+    return r4
 L3:
     unreachable
 
@@ -317,7 +311,7 @@ def get(o):
 L0:
     r0 = __main__.A :: type
     r1 = get_element_ptr o ob_type :: PyObject
-    r2 = load_mem r1 :: builtins.object*
+    r2 = borrow load_mem r1 :: builtins.object*
     keep_alive o
     r3 = r2 == r0
     if r3 goto L1 else goto L2 :: bool
@@ -396,7 +390,7 @@ def g(o):
 L0:
     r0 = __main__.A :: type
     r1 = get_element_ptr o ob_type :: PyObject
-    r2 = load_mem r1 :: builtins.object*
+    r2 = borrow load_mem r1 :: builtins.object*
     keep_alive o
     r3 = r2 == r0
     if r3 goto L1 else goto L2 :: bool
@@ -409,7 +403,7 @@ L1:
 L2:
     r8 = __main__.B :: type
     r9 = get_element_ptr o ob_type :: PyObject
-    r10 = load_mem r9 :: builtins.object*
+    r10 = borrow load_mem r9 :: builtins.object*
     keep_alive o
     r11 = r10 == r8
     if r11 goto L3 else goto L4 :: bool
@@ -462,7 +456,7 @@ def f(o):
 L0:
     r0 = __main__.A :: type
     r1 = get_element_ptr o ob_type :: PyObject
-    r2 = load_mem r1 :: builtins.object*
+    r2 = borrow load_mem r1 :: builtins.object*
     keep_alive o
     r3 = r2 == r0
     if r3 goto L1 else goto L2 :: bool
@@ -494,7 +488,7 @@ def g(o):
 L0:
     r0 = __main__.A :: type
     r1 = get_element_ptr o ob_type :: PyObject
-    r2 = load_mem r1 :: builtins.object*
+    r2 = borrow load_mem r1 :: builtins.object*
     keep_alive o
     r3 = r2 == r0
     if r3 goto L1 else goto L2 :: bool
diff --git a/mypyc/test-data/irbuild-set.test b/mypyc/test-data/irbuild-set.test
index c42a1fa74a75..5586a2bf4cfb 100644
--- a/mypyc/test-data/irbuild-set.test
+++ b/mypyc/test-data/irbuild-set.test
@@ -85,16 +85,14 @@ def test1():
     r4 :: ptr
     tmp_list :: list
     r5 :: set
-    r6 :: short_int
-    r7 :: native_int
-    r8 :: short_int
-    r9 :: bit
-    r10 :: object
-    r11, x, r12 :: int
-    r13 :: object
-    r14 :: i32
-    r15 :: bit
-    r16 :: short_int
+    r6, r7 :: native_int
+    r8 :: bit
+    r9 :: object
+    r10, x, r11 :: int
+    r12 :: object
+    r13 :: i32
+    r14 :: bit
+    r15 :: native_int
     a :: set
 L0:
     r0 = PyList_New(3)
@@ -111,20 +109,19 @@ L0:
     r6 = 0
 L1:
     r7 = var_object_size tmp_list
-    r8 = r7 << 1
-    r9 = int_lt r6, r8
-    if r9 goto L2 else goto L4 :: bool
+    r8 = r6 < r7 :: signed
+    if r8 goto L2 else goto L4 :: bool
 L2:
-    r10 = list_get_item_unsafe tmp_list, r6
-    r11 = unbox(int, r10)
-    x = r11
-    r12 = f(x)
-    r13 = box(int, r12)
-    r14 = PySet_Add(r5, r13)
-    r15 = r14 >= 0 :: signed
+    r9 = list_get_item_unsafe tmp_list, r6
+    r10 = unbox(int, r9)
+    x = r10
+    r11 = f(x)
+    r12 = box(int, r11)
+    r13 = PySet_Add(r5, r12)
+    r14 = r13 >= 0 :: signed
 L3:
-    r16 = r6 + 2
-    r6 = r16
+    r15 = r6 + 1
+    r6 = r15
     goto L1
 L4:
     a = r5
@@ -168,16 +165,15 @@ def test3():
     r7 :: set
     r8 :: short_int
     r9 :: native_int
-    r10 :: short_int
-    r11 :: object
-    r12 :: tuple[bool, short_int, object]
-    r13 :: short_int
-    r14 :: bool
-    r15 :: object
-    r16, x, r17 :: int
-    r18 :: object
-    r19 :: i32
-    r20, r21, r22 :: bit
+    r10 :: object
+    r11 :: tuple[bool, short_int, object]
+    r12 :: short_int
+    r13 :: bool
+    r14 :: object
+    r15, x, r16 :: int
+    r17 :: object
+    r18 :: i32
+    r19, r20, r21 :: bit
     c :: set
 L0:
     r0 = '1'
@@ -191,27 +187,26 @@ L0:
     r7 = PySet_New(0)
     r8 = 0
     r9 = PyDict_Size(tmp_dict)
-    r10 = r9 << 1
-    r11 = CPyDict_GetKeysIter(tmp_dict)
+    r10 = CPyDict_GetKeysIter(tmp_dict)
 L1:
-    r12 = CPyDict_NextKey(r11, r8)
-    r13 = r12[1]
-    r8 = r13
-    r14 = r12[0]
-    if r14 goto L2 else goto L4 :: bool
+    r11 = CPyDict_NextKey(r10, r8)
+    r12 = r11[1]
+    r8 = r12
+    r13 = r11[0]
+    if r13 goto L2 else goto L4 :: bool
 L2:
-    r15 = r12[2]
-    r16 = unbox(int, r15)
-    x = r16
-    r17 = f(x)
-    r18 = box(int, r17)
-    r19 = PySet_Add(r7, r18)
-    r20 = r19 >= 0 :: signed
+    r14 = r11[2]
+    r15 = unbox(int, r14)
+    x = r15
+    r16 = f(x)
+    r17 = box(int, r16)
+    r18 = PySet_Add(r7, r17)
+    r19 = r18 >= 0 :: signed
 L3:
-    r21 = CPyDict_CheckSize(tmp_dict, r10)
+    r20 = CPyDict_CheckSize(tmp_dict, r9)
     goto L1
 L4:
-    r22 = CPy_NoErrOccurred()
+    r21 = CPy_NoErrOccurred()
 L5:
     c = r7
     return 1
@@ -313,28 +308,26 @@ def test():
     tmp_list :: list
     r7 :: set
     r8, r9 :: list
-    r10 :: short_int
-    r11 :: native_int
-    r12 :: short_int
-    r13 :: bit
-    r14 :: object
-    r15, z :: int
-    r16 :: bit
-    r17 :: int
-    r18 :: object
-    r19 :: i32
-    r20 :: bit
-    r21 :: short_int
-    r22, r23, r24 :: object
-    r25, y, r26 :: int
-    r27 :: object
-    r28 :: i32
-    r29, r30 :: bit
-    r31, r32, r33 :: object
-    r34, x, r35 :: int
-    r36 :: object
-    r37 :: i32
-    r38, r39 :: bit
+    r10, r11 :: native_int
+    r12 :: bit
+    r13 :: object
+    r14, z :: int
+    r15 :: bit
+    r16 :: int
+    r17 :: object
+    r18 :: i32
+    r19 :: bit
+    r20 :: native_int
+    r21, r22, r23 :: object
+    r24, y, r25 :: int
+    r26 :: object
+    r27 :: i32
+    r28, r29 :: bit
+    r30, r31, r32 :: object
+    r33, x, r34 :: int
+    r35 :: object
+    r36 :: i32
+    r37, r38 :: bit
     a :: set
 L0:
     r0 = PyList_New(5)
@@ -357,60 +350,59 @@ L0:
     r10 = 0
 L1:
     r11 = var_object_size tmp_list
-    r12 = r11 << 1
-    r13 = int_lt r10, r12
-    if r13 goto L2 else goto L6 :: bool
+    r12 = r10 < r11 :: signed
+    if r12 goto L2 else goto L6 :: bool
 L2:
-    r14 = list_get_item_unsafe tmp_list, r10
-    r15 = unbox(int, r14)
-    z = r15
-    r16 = int_lt z, 8
-    if r16 goto L4 else goto L3 :: bool
+    r13 = list_get_item_unsafe tmp_list, r10
+    r14 = unbox(int, r13)
+    z = r14
+    r15 = int_lt z, 8
+    if r15 goto L4 else goto L3 :: bool
 L3:
     goto L5
 L4:
-    r17 = f1(z)
-    r18 = box(int, r17)
-    r19 = PyList_Append(r9, r18)
-    r20 = r19 >= 0 :: signed
+    r16 = f1(z)
+    r17 = box(int, r16)
+    r18 = PyList_Append(r9, r17)
+    r19 = r18 >= 0 :: signed
 L5:
-    r21 = r10 + 2
-    r10 = r21
+    r20 = r10 + 1
+    r10 = r20
     goto L1
 L6:
-    r22 = PyObject_GetIter(r9)
-    r23 = PyObject_GetIter(r22)
+    r21 = PyObject_GetIter(r9)
+    r22 = PyObject_GetIter(r21)
 L7:
-    r24 = PyIter_Next(r23)
-    if is_error(r24) goto L10 else goto L8
+    r23 = PyIter_Next(r22)
+    if is_error(r23) goto L10 else goto L8
 L8:
-    r25 = unbox(int, r24)
-    y = r25
-    r26 = f2(y)
-    r27 = box(int, r26)
-    r28 = PyList_Append(r8, r27)
-    r29 = r28 >= 0 :: signed
+    r24 = unbox(int, r23)
+    y = r24
+    r25 = f2(y)
+    r26 = box(int, r25)
+    r27 = PyList_Append(r8, r26)
+    r28 = r27 >= 0 :: signed
 L9:
     goto L7
 L10:
-    r30 = CPy_NoErrOccurred()
+    r29 = CPy_NoErrOccurred()
 L11:
-    r31 = PyObject_GetIter(r8)
-    r32 = PyObject_GetIter(r31)
+    r30 = PyObject_GetIter(r8)
+    r31 = PyObject_GetIter(r30)
 L12:
-    r33 = PyIter_Next(r32)
-    if is_error(r33) goto L15 else goto L13
+    r32 = PyIter_Next(r31)
+    if is_error(r32) goto L15 else goto L13
 L13:
-    r34 = unbox(int, r33)
-    x = r34
-    r35 = f3(x)
-    r36 = box(int, r35)
-    r37 = PySet_Add(r7, r36)
-    r38 = r37 >= 0 :: signed
+    r33 = unbox(int, r32)
+    x = r33
+    r34 = f3(x)
+    r35 = box(int, r34)
+    r36 = PySet_Add(r7, r35)
+    r37 = r36 >= 0 :: signed
 L14:
     goto L12
 L15:
-    r39 = CPy_NoErrOccurred()
+    r38 = CPy_NoErrOccurred()
 L16:
     a = r7
     return 1
diff --git a/mypyc/test-data/irbuild-singledispatch.test b/mypyc/test-data/irbuild-singledispatch.test
index c95e832cc5df..1060ee63c57d 100644
--- a/mypyc/test-data/irbuild-singledispatch.test
+++ b/mypyc/test-data/irbuild-singledispatch.test
@@ -57,7 +57,7 @@ def f_obj.__call__(__mypyc_self__, arg):
     r27 :: bool
 L0:
     r0 = get_element_ptr arg ob_type :: PyObject
-    r1 = load_mem r0 :: builtins.object*
+    r1 = borrow load_mem r0 :: builtins.object*
     keep_alive arg
     r2 = __mypyc_self__.dispatch_cache
     r3 = CPyDict_GetWithNone(r2, r1)
@@ -76,13 +76,13 @@ L2:
     r12 = load_address r11
     r13 = PyObject_Vectorcall(r9, r12, 2, 0)
     keep_alive r1, r10
-    r14 = CPyDict_SetItem(r2, r1, r13)
+    r14 = PyDict_SetItem(r2, r1, r13)
     r15 = r14 >= 0 :: signed
     r6 = r13
 L3:
     r16 = load_address PyLong_Type
     r17 = get_element_ptr r6 ob_type :: PyObject
-    r18 = load_mem r17 :: builtins.object*
+    r18 = borrow load_mem r17 :: builtins.object*
     keep_alive r6
     r19 = r18 == r16
     if r19 goto L4 else goto L7 :: bool
@@ -195,7 +195,7 @@ def f_obj.__call__(__mypyc_self__, x):
     r24 :: None
 L0:
     r0 = get_element_ptr x ob_type :: PyObject
-    r1 = load_mem r0 :: builtins.object*
+    r1 = borrow load_mem r0 :: builtins.object*
     keep_alive x
     r2 = __mypyc_self__.dispatch_cache
     r3 = CPyDict_GetWithNone(r2, r1)
@@ -214,13 +214,13 @@ L2:
     r12 = load_address r11
     r13 = PyObject_Vectorcall(r9, r12, 2, 0)
     keep_alive r1, r10
-    r14 = CPyDict_SetItem(r2, r1, r13)
+    r14 = PyDict_SetItem(r2, r1, r13)
     r15 = r14 >= 0 :: signed
     r6 = r13
 L3:
     r16 = load_address PyLong_Type
     r17 = get_element_ptr r6 ob_type :: PyObject
-    r18 = load_mem r17 :: builtins.object*
+    r18 = borrow load_mem r17 :: builtins.object*
     keep_alive r6
     r19 = r18 == r16
     if r19 goto L4 else goto L5 :: bool
@@ -274,3 +274,58 @@ L0:
     r1 = f(r0)
     r2 = box(None, 1)
     return r2
+
+[case registerNestedFunctionError]
+from functools import singledispatch
+from typing import Any, overload
+
+def dec(x: Any) -> Any:
+    return x
+
+def f() -> None:
+    @singledispatch  # E: Nested singledispatch functions not supported
+    def singledispatch_in_func(x: Any) -> None:
+        pass
+
+@dec
+def g() -> None:
+    @singledispatch  # E: Nested singledispatch functions not supported
+    def singledispatch_in_decorated(x: Any) -> None:
+        pass
+
+@overload
+def h(x: int) -> None:
+    pass
+@overload
+def h(x: str) -> None:
+    pass
+def h(x: Any) -> None:
+    @singledispatch  # E: Nested singledispatch functions not supported
+    def singledispatch_in_overload(x: Any) -> None:
+        pass
+
+@singledispatch
+def outside(x: Any) -> None:
+    pass
+
+def i() -> None:
+    @outside.register  # E: Registering nested functions not supported
+    def register_in_func(x: int) -> None:
+        pass
+
+@dec
+def j() -> None:
+    @outside.register  # E: Registering nested functions not supported
+    def register_in_decorated(x: int) -> None:
+        pass
+
+@overload
+def k(x: int) -> None:
+    pass
+@overload
+def k(x: str) -> None:
+    pass
+def k(x: Any) -> None:
+    @outside.register  # E: Registering nested functions not supported
+    def register_in_overload(x: int) -> None:
+        pass
diff --git a/mypyc/test-data/irbuild-statements.test b/mypyc/test-data/irbuild-statements.test
index 1f9336d32140..48b8e0e318b8 100644
--- a/mypyc/test-data/irbuild-statements.test
+++ b/mypyc/test-data/irbuild-statements.test
@@ -230,30 +230,27 @@ def f(ls: List[int]) -> int:
 def f(ls):
     ls :: list
     y :: int
-    r0 :: short_int
-    r1 :: native_int
-    r2 :: short_int
-    r3 :: bit
-    r4 :: object
-    r5, x, r6 :: int
-    r7 :: short_int
+    r0, r1 :: native_int
+    r2 :: bit
+    r3 :: object
+    r4, x, r5 :: int
+    r6 :: native_int
 L0:
     y = 0
     r0 = 0
 L1:
     r1 = var_object_size ls
-    r2 = r1 << 1
-    r3 = int_lt r0, r2
-    if r3 goto L2 else goto L4 :: bool
+    r2 = r0 < r1 :: signed
+    if r2 goto L2 else goto L4 :: bool
 L2:
-    r4 = list_get_item_unsafe ls, r0
-    r5 = unbox(int, r4)
-    x = r5
-    r6 = CPyTagged_Add(y, x)
-    y = r6
+    r3 = list_get_item_unsafe ls, r0
+    r4 = unbox(int, r3)
+    x = r4
+    r5 = CPyTagged_Add(y, x)
+    y = r5
 L3:
-    r7 = r0 + 2
-    r0 = r7
+    r6 = r0 + 1
+    r0 = r6
     goto L1
 L4:
     return y
@@ -269,39 +266,37 @@ def f(d):
     d :: dict
     r0 :: short_int
     r1 :: native_int
-    r2 :: short_int
-    r3 :: object
-    r4 :: tuple[bool, short_int, object]
-    r5 :: short_int
-    r6 :: bool
-    r7 :: object
-    r8, key :: int
-    r9, r10 :: object
-    r11 :: int
-    r12, r13 :: bit
+    r2 :: object
+    r3 :: tuple[bool, short_int, object]
+    r4 :: short_int
+    r5 :: bool
+    r6 :: object
+    r7, key :: int
+    r8, r9 :: object
+    r10 :: int
+    r11, r12 :: bit
 L0:
     r0 = 0
     r1 = PyDict_Size(d)
-    r2 = r1 << 1
-    r3 = CPyDict_GetKeysIter(d)
+    r2 = CPyDict_GetKeysIter(d)
 L1:
-    r4 = CPyDict_NextKey(r3, r0)
-    r5 = r4[1]
-    r0 = r5
-    r6 = r4[0]
-    if r6 goto L2 else goto L4 :: bool
+    r3 = CPyDict_NextKey(r2, r0)
+    r4 = r3[1]
+    r0 = r4
+    r5 = r3[0]
+    if r5 goto L2 else goto L4 :: bool
 L2:
-    r7 = r4[2]
-    r8 = unbox(int, r7)
-    key = r8
-    r9 = box(int, key)
-    r10 = CPyDict_GetItem(d, r9)
-    r11 = unbox(int, r10)
+    r6 = r3[2]
+    r7 = unbox(int, r6)
+    key = r7
+    r8 = box(int, key)
+    r9 = CPyDict_GetItem(d, r8)
+    r10 = unbox(int, r9)
 L3:
-    r12 = CPyDict_CheckSize(d, r2)
+    r11 = CPyDict_CheckSize(d, r1)
     goto L1
 L4:
-    r13 = CPy_NoErrOccurred()
+    r12 = CPy_NoErrOccurred()
 L5:
     return 1
 
@@ -321,54 +316,52 @@ def sum_over_even_values(d):
     s :: int
     r0 :: short_int
     r1 :: native_int
-    r2 :: short_int
-    r3 :: object
-    r4 :: tuple[bool, short_int, object]
-    r5 :: short_int
-    r6 :: bool
-    r7 :: object
-    r8, key :: int
-    r9, r10 :: object
-    r11, r12 :: int
-    r13 :: bit
-    r14, r15 :: object
-    r16, r17 :: int
-    r18, r19 :: bit
+    r2 :: object
+    r3 :: tuple[bool, short_int, object]
+    r4 :: short_int
+    r5 :: bool
+    r6 :: object
+    r7, key :: int
+    r8, r9 :: object
+    r10, r11 :: int
+    r12 :: bit
+    r13, r14 :: object
+    r15, r16 :: int
+    r17, r18 :: bit
 L0:
     s = 0
     r0 = 0
     r1 = PyDict_Size(d)
-    r2 = r1 << 1
-    r3 = CPyDict_GetKeysIter(d)
+    r2 = CPyDict_GetKeysIter(d)
 L1:
-    r4 = CPyDict_NextKey(r3, r0)
-    r5 = r4[1]
-    r0 = r5
-    r6 = r4[0]
-    if r6 goto L2 else goto L6 :: bool
+    r3 = CPyDict_NextKey(r2, r0)
+    r4 = r3[1]
+    r0 = r4
+    r5 = r3[0]
+    if r5 goto L2 else goto L6 :: bool
 L2:
-    r7 = r4[2]
-    r8 = unbox(int, r7)
-    key = r8
-    r9 = box(int, key)
-    r10 = CPyDict_GetItem(d, r9)
-    r11 = unbox(int, r10)
-    r12 = CPyTagged_Remainder(r11, 4)
-    r13 = r12 != 0
-    if r13 goto L3 else goto L4 :: bool
+    r6 = r3[2]
+    r7 = unbox(int, r6)
+    key = r7
+    r8 = box(int, key)
+    r9 = CPyDict_GetItem(d, r8)
+    r10 = unbox(int, r9)
+    r11 = CPyTagged_Remainder(r10, 4)
+    r12 = r11 != 0
+    if r12 goto L3 else goto L4 :: bool
 L3:
     goto L5
 L4:
-    r14 = box(int, key)
-    r15 = CPyDict_GetItem(d, r14)
-    r16 = unbox(int, r15)
-    r17 = CPyTagged_Add(s, r16)
-    s = r17
+    r13 = box(int, key)
+    r14 = CPyDict_GetItem(d, r13)
+    r15 = unbox(int, r14)
+    r16 = CPyTagged_Add(s, r15)
+    s = r16
 L5:
-    r18 = CPyDict_CheckSize(d, r2)
+    r17 = CPyDict_CheckSize(d, r1)
     goto L1
 L6:
-    r19 = CPy_NoErrOccurred()
+    r18 = CPy_NoErrOccurred()
 L7:
     return s
 
@@ -597,16 +590,16 @@ L0:
     r0 = CPySequence_CheckUnpackCount(l, 2)
     r1 = r0 >= 0 :: signed
     r2 = list_get_item_unsafe l, 0
-    r3 = list_get_item_unsafe l, 2
+    r3 = list_get_item_unsafe l, 1
     x = r2
     r4 = unbox(int, r3)
     y = r4
     r5 = CPySequence_CheckUnpackCount(t, 2)
     r6 = r5 >= 0 :: signed
-    r7 = CPySequenceTuple_GetItem(t, 0)
-    r8 = CPySequenceTuple_GetItem(t, 2)
-    r9 = unbox(int, r8)
+    r7 = CPySequenceTuple_GetItemUnsafe(t, 0)
+    r8 = CPySequenceTuple_GetItemUnsafe(t, 1)
     x = r7
+    r9 = unbox(int, r8)
     y = r9
     return 1
 
@@ -872,33 +865,32 @@ def g(x: Iterable[int]) -> None:
 [out]
 def f(a):
     a :: list
-    r0, r1 :: short_int
-    r2 :: native_int
-    r3 :: short_int
-    r4 :: bit
+    r0 :: short_int
+    r1, r2 :: native_int
+    r3 :: bit
     i :: int
-    r5 :: object
-    r6, x, r7 :: int
-    r8, r9 :: short_int
+    r4 :: object
+    r5, x, r6 :: int
+    r7 :: short_int
+    r8 :: native_int
 L0:
     r0 = 0
     r1 = 0
 L1:
     r2 = var_object_size a
-    r3 = r2 << 1
-    r4 = int_lt r1, r3
-    if r4 goto L2 else goto L4 :: bool
+    r3 = r1 < r2 :: signed
+    if r3 goto L2 else goto L4 :: bool
 L2:
     i = r0
-    r5 = list_get_item_unsafe a, r1
-    r6 = unbox(int, r5)
-    x = r6
-    r7 = CPyTagged_Add(i, x)
+    r4 = list_get_item_unsafe a, r1
+    r5 = unbox(int, r4)
+    x = r5
+    r6 = CPyTagged_Add(i, x)
 L3:
-    r8 = r0 + 2
-    r0 = r8
-    r9 = r1 + 2
-    r1 = r9
+    r7 = r0 + 2
+    r0 = r7
+    r8 = r1 + 1
+    r1 = r8
     goto L1
 L4:
 L5:
@@ -944,66 +936,65 @@ def g(a: Iterable[bool], b: List[int]) -> None:
 def f(a, b):
     a :: list
     b :: object
-    r0 :: short_int
+    r0 :: native_int
     r1 :: object
     r2 :: native_int
-    r3 :: short_int
-    r4 :: bit
-    r5, r6 :: object
-    r7, x :: int
-    r8, y :: bool
-    r9 :: i32
-    r10 :: bit
-    r11 :: bool
-    r12 :: short_int
-    r13 :: bit
+    r3 :: bit
+    r4, r5 :: object
+    r6, x :: int
+    r7, y :: bool
+    r8 :: i32
+    r9 :: bit
+    r10 :: bool
+    r11 :: native_int
+    r12 :: bit
 L0:
     r0 = 0
     r1 = PyObject_GetIter(b)
 L1:
     r2 = var_object_size a
-    r3 = r2 << 1
-    r4 = int_lt r0, r3
-    if r4 goto L2 else goto L7 :: bool
+    r3 = r0 < r2 :: signed
+    if r3 goto L2 else goto L7 :: bool
 L2:
-    r5 = PyIter_Next(r1)
-    if is_error(r5) goto L7 else goto L3
+    r4 = PyIter_Next(r1)
+    if is_error(r4) goto L7 else goto L3
 L3:
-    r6 = list_get_item_unsafe a, r0
-    r7 = unbox(int, r6)
-    x = r7
-    r8 = unbox(bool, r5)
-    y = r8
-    r9 = PyObject_IsTrue(b)
-    r10 = r9 >= 0 :: signed
-    r11 = truncate r9: i32 to builtins.bool
-    if r11 goto L4 else goto L5 :: bool
+    r5 = list_get_item_unsafe a, r0
+    r6 = unbox(int, r5)
+    x = r6
+    r7 = unbox(bool, r4)
+    y = r7
+    r8 = PyObject_IsTrue(b)
+    r9 = r8 >= 0 :: signed
+    r10 = truncate r8: i32 to builtins.bool
+    if r10 goto L4 else goto L5 :: bool
 L4:
     x = 2
 L5:
 L6:
-    r12 = r0 + 2
-    r0 = r12
+    r11 = r0 + 1
+    r0 = r11
     goto L1
 L7:
-    r13 = CPy_NoErrOccurred()
+    r12 = CPy_NoErrOccurred()
 L8:
     return 1
 def g(a, b):
     a :: object
     b :: list
     r0 :: object
-    r1, r2 :: short_int
+    r1 :: native_int
+    r2 :: short_int
     z :: int
     r3 :: object
     r4 :: native_int
-    r5 :: short_int
-    r6, r7 :: bit
-    r8, x :: bool
-    r9 :: object
-    r10, y :: int
-    r11, r12 :: short_int
-    r13 :: bit
+    r5, r6 :: bit
+    r7, x :: bool
+    r8 :: object
+    r9, y :: int
+    r10 :: native_int
+    r11 :: short_int
+    r12 :: bit
 L0:
     r0 = PyObject_GetIter(a)
     r1 = 0
@@ -1014,28 +1005,27 @@ L1:
     if is_error(r3) goto L6 else goto L2
 L2:
     r4 = var_object_size b
-    r5 = r4 << 1
-    r6 = int_lt r1, r5
-    if r6 goto L3 else goto L6 :: bool
+    r5 = r1 < r4 :: signed
+    if r5 goto L3 else goto L6 :: bool
 L3:
-    r7 = int_lt r2, 10
-    if r7 goto L4 else goto L6 :: bool
+    r6 = int_lt r2, 10
+    if r6 goto L4 else goto L6 :: bool
 L4:
-    r8 = unbox(bool, r3)
-    x = r8
-    r9 = list_get_item_unsafe b, r1
-    r10 = unbox(int, r9)
-    y = r10
+    r7 = unbox(bool, r3)
+    x = r7
+    r8 = list_get_item_unsafe b, r1
+    r9 = unbox(int, r8)
+    y = r9
     x = 0
 L5:
-    r11 = r1 + 2
-    r1 = r11
-    r12 = r2 + 2
-    r2 = r12
-    z = r12
+    r10 = r1 + 1
+    r1 = r10
+    r11 = r2 + 2
+    r2 = r11
+    z = r11
     goto L1
 L6:
-    r13 = CPy_NoErrOccurred()
+    r12 = CPy_NoErrOccurred()
 L7:
     return 1
 
diff --git a/mypyc/test-data/irbuild-str.test b/mypyc/test-data/irbuild-str.test
index ad495dddcb15..3fa39819498d 100644
--- a/mypyc/test-data/irbuild-str.test
+++ b/mypyc/test-data/irbuild-str.test
@@ -1,13 +1,15 @@
 [case testStrSplit]
-from typing import Optional, List
+from typing import NewType, Optional, List, Union
+NewStr = NewType("NewStr", str)
 
-def do_split(s: str, sep: Optional[str] = None, max_split: Optional[int] = None) -> List[str]:
+def do_split(s: Union[str, NewStr], sep: Optional[str] = None, max_split: Optional[int] = None) -> List[str]:
     if sep is not None:
         if max_split is not None:
             return s.split(sep, max_split)
         else:
             return s.split(sep)
     return s.split()
+[typing fixtures/typing-full.pyi]
 [out]
 def do_split(s, sep, max_split):
     s :: str
@@ -56,60 +58,40 @@ L9:
 
 
 [case testStrEquality]
+from typing import NewType, Union
+NewStr = NewType("NewStr", str)
 def eq(x: str, y: str) -> bool:
     return x == y
 
-def neq(x: str, y: str) -> bool:
+def neq(x: str, y: Union[str, NewStr]) -> bool:
     return x != y
 
+[typing fixtures/typing-full.pyi]
 [out]
 def eq(x, y):
     x, y :: str
-    r0 :: i32
-    r1 :: bit
-    r2 :: object
-    r3, r4, r5 :: bit
+    r0 :: bool
 L0:
-    r0 = PyUnicode_Compare(x, y)
-    r1 = r0 == -1
-    if r1 goto L1 else goto L3 :: bool
-L1:
-    r2 = PyErr_Occurred()
-    r3 = r2 != 0
-    if r3 goto L2 else goto L3 :: bool
-L2:
-    r4 = CPy_KeepPropagating()
-L3:
-    r5 = r0 == 0
-    return r5
+    r0 = CPyStr_Equal(x, y)
+    return r0
 def neq(x, y):
     x, y :: str
-    r0 :: i32
+    r0 :: bool
     r1 :: bit
-    r2 :: object
-    r3, r4, r5 :: bit
 L0:
-    r0 = PyUnicode_Compare(x, y)
-    r1 = r0 == -1
-    if r1 goto L1 else goto L3 :: bool
-L1:
-    r2 = PyErr_Occurred()
-    r3 = r2 != 0
-    if r3 goto L2 else goto L3 :: bool
-L2:
-    r4 = CPy_KeepPropagating()
-L3:
-    r5 = r0 != 0
-    return r5
+    r0 = CPyStr_Equal(x, y)
+    r1 = r0 == 0
+    return r1
 
 [case testStrReplace]
-from typing import Optional
-
-def do_replace(s: str, old_substr: str, new_substr: str, max_count: Optional[int] = None) -> str:
+from typing import NewType, Optional, Union
+NewStr = NewType("NewStr", str)
+def do_replace(s: Union[str, NewStr], old_substr: str, new_substr: str, max_count: Optional[int] = None) -> str:
     if max_count is not None:
         return s.replace(old_substr, new_substr, max_count)
     else:
         return s.replace(old_substr, new_substr)
+[typing fixtures/typing-full.pyi]
 [out]
 def do_replace(s, old_substr, new_substr, max_count):
     s, old_substr, new_substr :: str
@@ -138,17 +120,19 @@ L5:
     unreachable
 
 [case testStrStartswithEndswithTuple]
-from typing import Tuple
+from typing import NewType, Tuple, Union
+NewStr = NewType("NewStr", str)
 
-def do_startswith(s1: str, s2: Tuple[str, ...]) -> bool:
+def do_startswith(s1: Union[str, NewStr], s2: Tuple[str, ...]) -> bool:
     return s1.startswith(s2)
 
-def do_endswith(s1: str, s2: Tuple[str, ...]) -> bool:
+def do_endswith(s1: Union[str, NewStr], s2: Tuple[str, ...]) -> bool:
     return s1.endswith(s2)
 
-def do_tuple_literal_args(s1: str) -> None:
+def do_tuple_literal_args(s1: Union[str, NewStr]) -> None:
     x = s1.startswith(("a", "b"))
     y = s1.endswith(("a", "b"))
+[typing fixtures/typing-full.pyi]
 [out]
 def do_startswith(s1, s2):
     s1 :: str
@@ -189,11 +173,14 @@ L0:
     return 1
 
 [case testStrToBool]
-def is_true(x: str) -> bool:
+from typing import NewType, Union
+NewStr = NewType("NewStr", str)
+def is_true(x: Union[str, NewStr]) -> bool:
     if x:
         return True
     else:
         return False
+[typing fixtures/typing-full.pyi]
 [out]
 def is_true(x):
     x :: str
@@ -209,11 +196,14 @@ L3:
     unreachable
 
 [case testStringFormatMethod]
-def f(s: str, num: int) -> None:
+from typing import NewType, Union
+NewStr = NewType("NewStr", str)
+def f(s: Union[str, NewStr], num: int) -> None:
     s1 = "Hi! I'm {}, and I'm {} years old.".format(s, num)
     s2 = ''.format()
     s3 = 'abc'.format()
     s4 = '}}{}{{{}}}{{{}'.format(num, num, num)
+[typing fixtures/typing-full.pyi]
 [out]
 def f(s, num):
     s :: str
@@ -241,11 +231,14 @@ L0:
     return 1
 
 [case testFStrings_64bit]
-def f(var: str, num: int) -> None:
+from typing import NewType, Union
+NewStr = NewType("NewStr", str)
+def f(var: Union[str, NewStr], num: int) -> None:
     s1 = f"Hi! I'm {var}. I am {num} years old."
     s2 = f'Hello {var:>{num}}'
     s3 = f''
     s4 = f'abc'
+[typing fixtures/typing-full.pyi]
 [out]
 def f(var, num):
     var :: str
@@ -291,7 +284,9 @@ L0:
     return 1
 
 [case testStringFormattingCStyle]
-def f(var: str, num: int) -> None:
+from typing import NewType, Union
+NewStr = NewType("NewStr", str)
+def f(var: Union[str, NewStr], num: int) -> None:
     s1 = "Hi! I'm %s." % var
     s2 = "I am %d years old." % num
     s3 = "Hi! I'm %s. I am %d years old." % (var, num)
@@ -330,23 +325,49 @@ L0:
 [case testDecode]
 def f(b: bytes) -> None:
     b.decode()
+    b.decode('Utf_8')
     b.decode('utf-8')
+    b.decode('UTF8')
+    b.decode('latin1')
+    b.decode('Latin-1')
+    b.decode('ascii')
+    encoding = 'utf-8'
+    b.decode(encoding)
     b.decode('utf-8', 'backslashreplace')
+def variants(b: bytes) -> None:
+    b.decode(encoding="UTF_8")
+    b.decode("ascii", errors="strict")
 [out]
 def f(b):
     b :: bytes
-    r0, r1, r2, r3, r4, r5 :: str
+    r0, r1, r2, r3, r4, r5, r6, r7, encoding, r8, r9, r10, r11 :: str
 L0:
-    r0 = CPy_Decode(b, 0, 0)
-    r1 = 'utf-8'
-    r2 = CPy_Decode(b, r1, 0)
-    r3 = 'utf-8'
-    r4 = 'backslashreplace'
-    r5 = CPy_Decode(b, r3, r4)
+    r0 = CPy_DecodeUTF8(b)
+    r1 = CPy_DecodeUTF8(b)
+    r2 = CPy_DecodeUTF8(b)
+    r3 = CPy_DecodeUTF8(b)
+    r4 = CPy_DecodeLatin1(b)
+    r5 = CPy_DecodeLatin1(b)
+    r6 = CPy_DecodeASCII(b)
+    r7 = 'utf-8'
+    encoding = r7
+    r8 = CPy_Decode(b, encoding, 0)
+    r9 = 'utf-8'
+    r10 = 'backslashreplace'
+    r11 = CPy_Decode(b, r9, r10)
+    return 1
+def variants(b):
+    b :: bytes
+    r0, r1 :: str
+L0:
+    r0 = CPy_DecodeUTF8(b)
+    r1 = CPy_DecodeASCII(b)
     return 1
 
 [case testEncode_64bit]
-def f(s: str) -> None:
+from typing import NewType, Union
+NewStr = NewType("NewStr", str)
+def f(s: Union[str, NewStr]) -> None:
     s.encode()
     s.encode('utf-8')
     s.encode('utf8', 'strict')
@@ -364,6 +385,7 @@ def f(s: str) -> None:
     s.encode(encoding=encoding, errors=errors)
     s.encode('latin2')
 
+[typing fixtures/typing-full.pyi]
 [out]
 def f(s):
     s :: str
@@ -434,7 +456,9 @@ L0:
     return 1
 
 [case testOrd]
-def str_ord(x: str) -> int:
+from typing import NewType, Union
+NewStr = NewType("NewStr", str)
+def str_ord(x: Union[str, NewStr]) -> int:
     return ord(x)
 def str_ord_literal() -> int:
     return ord("a")
@@ -444,6 +468,7 @@ def bytes_ord_literal() -> int:
     return ord(b"a")
 def any_ord(x) -> int:
     return ord(x)
+[typing fixtures/typing-full.pyi]
 [out]
 def str_ord(x):
     x :: str
@@ -483,13 +508,16 @@ L0:
     return r6
 
 [case testStrip]
-def do_strip(s: str) -> None:
+from typing import NewType, Union
+NewStr = NewType("NewStr", str)
+def do_strip(s: Union[str, NewStr]) -> None:
     s.lstrip("x")
     s.strip("y")
     s.rstrip("z")
     s.lstrip()
     s.strip()
     s.rstrip()
+[typing fixtures/typing-full.pyi]
 [out]
 def do_strip(s):
     s, r0, r1, r2, r3, r4, r5, r6, r7, r8 :: str
@@ -504,3 +532,211 @@ L0:
     r7 = CPyStr_Strip(s, 0)
     r8 = CPyStr_RStrip(s, 0)
     return 1
+
+[case testCountAll_64bit]
+from typing import NewType, Union
+NewStr = NewType("NewStr", str)
+def do_count(s: str) -> int:
+    return s.count("x")
+[typing fixtures/typing-full.pyi]
+[out]
+def do_count(s):
+    s, r0 :: str
+    r1 :: native_int
+    r2, r3, r4 :: bit
+    r5, r6, r7 :: int
+L0:
+    r0 = 'x'
+    r1 = CPyStr_Count(s, r0, 0)
+    r2 = r1 >= 0 :: signed
+    r3 = r1 <= 4611686018427387903 :: signed
+    if r3 goto L1 else goto L2 :: bool
+L1:
+    r4 = r1 >= -4611686018427387904 :: signed
+    if r4 goto L3 else goto L2 :: bool
+L2:
+    r5 = CPyTagged_FromInt64(r1)
+    r6 = r5
+    goto L4
+L3:
+    r7 = r1 << 1
+    r6 = r7
+L4:
+    return r6
+
+[case testCountStart_64bit]
+from typing import NewType, Union
+NewStr = NewType("NewStr", str)
+def do_count(s: str, start: int) -> int:
+    return s.count("x", start)
+[typing fixtures/typing-full.pyi]
+[out]
+def do_count(s, start):
+    s :: str
+    start :: int
+    r0 :: str
+    r1 :: native_int
+    r2, r3, r4 :: bit
+    r5, r6, r7 :: int
+L0:
+    r0 = 'x'
+    r1 = CPyStr_Count(s, r0, start)
+    r2 = r1 >= 0 :: signed
+    r3 = r1 <= 4611686018427387903 :: signed
+    if r3 goto L1 else goto L2 :: bool
+L1:
+    r4 = r1 >= -4611686018427387904 :: signed
+    if r4 goto L3 else goto L2 :: bool
+L2:
+    r5 = CPyTagged_FromInt64(r1)
+    r6 = r5
+    goto L4
+L3:
+    r7 = r1 << 1
+    r6 = r7
+L4:
+    return r6
+
+[case testCountStartEnd_64bit]
+from typing import NewType, Union
+NewStr = NewType("NewStr", str)
+def do_count(s: str, start: int, end: int) -> int:
+    return s.count("x", start, end)
+[typing fixtures/typing-full.pyi]
+[out]
+def do_count(s, start, end):
+    s :: str
+    start, end :: int
+    r0 :: str
+    r1 :: native_int
+    r2, r3, r4 :: bit
+    r5, r6, r7 :: int
+L0:
+    r0 = 'x'
+    r1 = CPyStr_CountFull(s, r0, start, end)
+    r2 = r1 >= 0 :: signed
+    r3 = r1 <= 4611686018427387903 :: signed
+    if r3 goto L1 else goto L2 :: bool
+L1:
+    r4 = r1 >= -4611686018427387904 :: signed
+    if r4 goto L3 else goto L2 :: bool
+L2:
+    r5 = CPyTagged_FromInt64(r1)
+    r6 = r5
+    goto L4
+L3:
+    r7 = r1 << 1
+    r6 = r7
+L4:
+    return r6
+
+[case testFStringFromConstants]
+from typing import Final
+string: Final = "abc"
+integer: Final = 123
+floating: Final = 3.14
+boolean: Final = True
+
+def test(x: str) -> str:
+    return f"{string}{integer}{floating}{boolean}{x}{boolean}{floating}{integer}{string}{x}{string}{integer}{floating}{boolean}"
+def test2(x: str) -> str:
+    return f"{string}{integer}{floating}{boolean}{x}{boolean}{floating}{integer}{string}{x}{string}{integer}{floating}{boolean}{x}"
+def test3(x: str) -> str:
+    return f"{x}{string}{integer}{floating}{boolean}{x}{boolean}{floating}{integer}{string}{x}{string}{integer}{floating}{boolean}{x}"
+
+[out]
+def test(x):
+    x, r0, r1, r2, r3 :: str
+L0:
+    r0 = 'abc1233.14True'
+    r1 = 'True3.14123abc'
+    r2 = 'abc1233.14True'
+    r3 = CPyStr_Build(5, r0, x, r1, x, r2)
+    return r3
+def test2(x):
+    x, r0, r1, r2, r3 :: str
+L0:
+    r0 = 'abc1233.14True'
+    r1 = 'True3.14123abc'
+    r2 = 'abc1233.14True'
+    r3 = CPyStr_Build(6, r0, x, r1, x, r2, x)
+    return r3
+def test3(x):
+    x, r0, r1, r2, r3 :: str
+L0:
+    r0 = 'abc1233.14True'
+    r1 = 'True3.14123abc'
+    r2 = 'abc1233.14True'
+    r3 = CPyStr_Build(7, x, r0, x, r1, x, r2, x)
+    return r3
+
+[case testOptionalStrEquality1]
+from typing import Optional
+
+def opt_opt(x: Optional[str], y: Optional[str]) -> bool:
+    return x == y
+[out]
+def opt_opt(x, y):
+    x, y :: union[str, None]
+    r0 :: object
+    r1 :: bit
+    r2 :: object
+    r3 :: bit
+    r4 :: bool
+    r5 :: object
+    r6 :: bit
+    r7, r8 :: str
+    r9 :: bool
+L0:
+    r0 = load_address _Py_NoneStruct
+    r1 = x == r0
+    if r1 goto L1 else goto L2 :: bool
+L1:
+    r2 = load_address _Py_NoneStruct
+    r3 = y == r2
+    r4 = r3
+    goto L5
+L2:
+    r5 = load_address _Py_NoneStruct
+    r6 = y == r5
+    if r6 goto L3 else goto L4 :: bool
+L3:
+    r4 = 0
+    goto L5
+L4:
+    r7 = unchecked borrow cast(str, x)
+    r8 = unchecked borrow cast(str, y)
+    r9 = CPyStr_Equal(r7, r8)
+    r4 = r9
+L5:
+    keep_alive x, y
+    return r4
+
+[case testOptionalStrEquality2]
+from typing import Optional
+
+def opt_non_opt(x: Optional[str], y: str) -> bool:
+    return x == y
+[out]
+def opt_non_opt(x, y):
+    x :: union[str, None]
+    y :: str
+    r0 :: object
+    r1 :: bit
+    r2 :: bool
+    r3 :: str
+    r4 :: bool
+L0:
+    r0 = load_address _Py_NoneStruct
+    r1 = x == r0
+    if r1 goto L1 else goto L2 :: bool
+L1:
+    r2 = 0
+    goto L3
+L2:
+    r3 = unchecked borrow cast(str, x)
+    r4 = CPyStr_Equal(r3, y)
+    r2 = r4
+L3:
+    keep_alive x
+    return r2
diff --git a/mypyc/test-data/irbuild-try.test b/mypyc/test-data/irbuild-try.test
index ad1aa78c0554..ec470eae1e88 100644
--- a/mypyc/test-data/irbuild-try.test
+++ b/mypyc/test-data/irbuild-try.test
@@ -412,7 +412,7 @@ def foo(x):
     r36 :: bit
 L0:
     r0 = PyObject_Vectorcall(x, 0, 0, 0)
-    r1 = PyObject_Type(r0)
+    r1 = CPy_TYPE(r0)
     r2 = '__exit__'
     r3 = CPyObject_GetAttr(r1, r2)
     r4 = '__enter__'
diff --git a/mypyc/test-data/irbuild-tuple.test b/mypyc/test-data/irbuild-tuple.test
index 582391ff6f98..00ea7f074a5d 100644
--- a/mypyc/test-data/irbuild-tuple.test
+++ b/mypyc/test-data/irbuild-tuple.test
@@ -127,27 +127,24 @@ def f(xs: Tuple[str, ...]) -> None:
 [out]
 def f(xs):
     xs :: tuple
-    r0 :: short_int
-    r1 :: native_int
-    r2 :: short_int
-    r3 :: bit
-    r4 :: object
-    r5, x :: str
-    r6 :: short_int
+    r0, r1 :: native_int
+    r2 :: bit
+    r3 :: object
+    r4, x :: str
+    r5 :: native_int
 L0:
-    r0 = 0
+    r0 = var_object_size xs
+    r1 = 0
 L1:
-    r1 = var_object_size xs
-    r2 = r1 << 1
-    r3 = int_lt r0, r2
-    if r3 goto L2 else goto L4 :: bool
+    r2 = r1 < r0 :: signed
+    if r2 goto L2 else goto L4 :: bool
 L2:
-    r4 = CPySequenceTuple_GetItem(xs, r0)
-    r5 = cast(str, r4)
-    x = r5
+    r3 = CPySequenceTuple_GetItemUnsafe(xs, r1)
+    r4 = cast(str, r3)
+    x = r4
 L3:
-    r6 = r0 + 2
-    r0 = r6
+    r5 = r1 + 1
+    r1 = r5
     goto L1
 L4:
     return 1
@@ -187,30 +184,102 @@ def f(i: int) -> bool:
 [out]
 def f(i):
     i :: int
-    r0 :: bit
-    r1 :: bool
-    r2 :: bit
+    r0, r1, r2 :: bit
     r3 :: bool
-    r4 :: bit
 L0:
     r0 = int_eq i, 2
-    if r0 goto L1 else goto L2 :: bool
+    if r0 goto L4 else goto L1 :: bool
 L1:
-    r1 = r0
-    goto L3
+    r1 = int_eq i, 4
+    if r1 goto L4 else goto L2 :: bool
+L2:
+    r2 = int_eq i, 6
+    if r2 goto L4 else goto L3 :: bool
+L3:
+    r3 = 0
+    goto L5
+L4:
+    r3 = 1
+L5:
+    return r3
+
+[case testTupleOperatorNotIn]
+def x() -> int:
+    return 1
+def y() -> int:
+    return 2
+def z() -> int:
+    return 3
+
+def f() -> bool:
+    return z() not in (x(), y())
+[out]
+def x():
+L0:
+    return 2
+def y():
+L0:
+    return 4
+def z():
+L0:
+    return 6
+def f():
+    r0, r1, r2 :: int
+    r3, r4 :: bit
+    r5 :: bool
+L0:
+    r0 = z()
+    r1 = x()
+    r2 = y()
+    r3 = int_ne r0, r1
+    if r3 goto L1 else goto L3 :: bool
+L1:
+    r4 = int_ne r0, r2
+    if r4 goto L2 else goto L3 :: bool
+L2:
+    r5 = 1
+    goto L4
+L3:
+    r5 = 0
+L4:
+    return r5
+
+[case testTupleOperatorInFinalTuple]
+from typing import Final
+
+tt: Final = (1, 2)
+
+def f(x: int) -> bool:
+    return x in tt
+[out]
+def f(x):
+    x :: int
+    r0 :: tuple[int, int]
+    r1 :: bool
+    r2, r3 :: int
+    r4, r5 :: bit
+    r6 :: bool
+L0:
+    r0 = __main__.tt :: static
+    if is_error(r0) goto L1 else goto L2
+L1:
+    r1 = raise NameError('value for final name "tt" was not set')
+    unreachable
 L2:
-    r2 = int_eq i, 4
-    r1 = r2
+    r2 = r0[0]
+    r3 = r0[1]
+    r4 = int_eq x, r2
+    if r4 goto L5 else goto L3 :: bool
 L3:
-    if r1 goto L4 else goto L5 :: bool
+    r5 = int_eq x, r3
+    if r5 goto L5 else goto L4 :: bool
 L4:
-    r3 = r1
+    r6 = 0
     goto L6
 L5:
-    r4 = int_eq i, 6
-    r3 = r4
+    r6 = 1
 L6:
-    return r3
+    return r6
 
 [case testTupleBuiltFromList]
 def f(val: int) -> bool:
@@ -234,16 +303,13 @@ def test():
     source :: list
     r5 :: native_int
     r6 :: tuple
-    r7 :: short_int
-    r8 :: native_int
-    r9 :: short_int
-    r10 :: bit
-    r11 :: object
-    r12, x :: int
-    r13 :: bool
-    r14 :: object
-    r15 :: bit
-    r16 :: short_int
+    r7, r8 :: native_int
+    r9 :: bit
+    r10 :: object
+    r11, x :: int
+    r12 :: bool
+    r13 :: object
+    r14 :: native_int
     a :: tuple
 L0:
     r0 = PyList_New(3)
@@ -261,19 +327,18 @@ L0:
     r7 = 0
 L1:
     r8 = var_object_size source
-    r9 = r8 << 1
-    r10 = int_lt r7, r9
-    if r10 goto L2 else goto L4 :: bool
+    r9 = r7 < r8 :: signed
+    if r9 goto L2 else goto L4 :: bool
 L2:
-    r11 = list_get_item_unsafe source, r7
-    r12 = unbox(int, r11)
-    x = r12
-    r13 = f(x)
-    r14 = box(bool, r13)
-    r15 = CPySequenceTuple_SetItemUnsafe(r6, r7, r14)
+    r10 = list_get_item_unsafe source, r7
+    r11 = unbox(int, r10)
+    x = r11
+    r12 = f(x)
+    r13 = box(bool, r12)
+    CPySequenceTuple_SetItemUnsafe(r6, r7, r13)
 L3:
-    r16 = r7 + 2
-    r7 = r16
+    r14 = r7 + 1
+    r7 = r14
     goto L1
 L4:
     a = r6
@@ -298,14 +363,12 @@ def test():
     r1 :: native_int
     r2 :: bit
     r3 :: tuple
-    r4 :: short_int
-    r5 :: native_int
-    r6 :: bit
-    r7 :: short_int
-    r8 :: bit
-    r9, x, r10 :: str
-    r11 :: bit
-    r12 :: short_int
+    r4 :: native_int
+    r5 :: bit
+    r6 :: native_int
+    r7 :: bit
+    r8, x, r9 :: str
+    r10 :: native_int
     a :: tuple
 L0:
     r0 = 'abc'
@@ -313,26 +376,437 @@ L0:
     r1 = CPyStr_Size_size_t(source)
     r2 = r1 >= 0 :: signed
     r3 = PyTuple_New(r1)
+    r4 = CPyStr_Size_size_t(source)
+    r5 = r4 >= 0 :: signed
+    r6 = 0
+L1:
+    r7 = r6 < r4 :: signed
+    if r7 goto L2 else goto L4 :: bool
+L2:
+    r8 = CPyStr_GetItemUnsafe(source, r6)
+    x = r8
+    r9 = f2(x)
+    CPySequenceTuple_SetItemUnsafe(r3, r6, r9)
+L3:
+    r10 = r6 + 1
+    r6 = r10
+    goto L1
+L4:
+    a = r3
+    return 1
+
+[case testTupleBuiltFromStrExpr]
+def f2(val: str) -> str:
+    return val + "f2"
+
+def test() -> None:
+    a = tuple(f2(x) for x in "abc")
+
+[out]
+def f2(val):
+    val, r0, r1 :: str
+L0:
+    r0 = 'f2'
+    r1 = PyUnicode_Concat(val, r0)
+    return r1
+def test():
+    r0 :: str
+    r1 :: native_int
+    r2 :: bit
+    r3 :: tuple
+    r4 :: native_int
+    r5 :: bit
+    r6 :: native_int
+    r7 :: bit
+    r8, x, r9 :: str
+    r10 :: native_int
+    a :: tuple
+L0:
+    r0 = 'abc'
+    r1 = CPyStr_Size_size_t(r0)
+    r2 = r1 >= 0 :: signed
+    r3 = PyTuple_New(r1)
+    r4 = CPyStr_Size_size_t(r0)
+    r5 = r4 >= 0 :: signed
+    r6 = 0
+L1:
+    r7 = r6 < r4 :: signed
+    if r7 goto L2 else goto L4 :: bool
+L2:
+    r8 = CPyStr_GetItemUnsafe(r0, r6)
+    x = r8
+    r9 = f2(x)
+    CPySequenceTuple_SetItemUnsafe(r3, r6, r9)
+L3:
+    r10 = r6 + 1
+    r6 = r10
+    goto L1
+L4:
+    a = r3
+    return 1
+
+[case testTupleBuiltFromFinalStr]
+from typing import Final
+
+source: Final = "abc"
+
+def f2(val: str) -> str:
+    return val + "f2"
+
+def test() -> None:
+    a = tuple(f2(x) for x in source)
+[out]
+def f2(val):
+    val, r0, r1 :: str
+L0:
+    r0 = 'f2'
+    r1 = PyUnicode_Concat(val, r0)
+    return r1
+def test():
+    r0 :: str
+    r1 :: native_int
+    r2 :: bit
+    r3 :: tuple
+    r4 :: native_int
+    r5 :: bit
+    r6 :: native_int
+    r7 :: bit
+    r8, x, r9 :: str
+    r10 :: native_int
+    a :: tuple
+L0:
+    r0 = 'abc'
+    r1 = CPyStr_Size_size_t(r0)
+    r2 = r1 >= 0 :: signed
+    r3 = PyTuple_New(r1)
+    r4 = CPyStr_Size_size_t(r0)
+    r5 = r4 >= 0 :: signed
+    r6 = 0
+L1:
+    r7 = r6 < r4 :: signed
+    if r7 goto L2 else goto L4 :: bool
+L2:
+    r8 = CPyStr_GetItemUnsafe(r0, r6)
+    x = r8
+    r9 = f2(x)
+    CPySequenceTuple_SetItemUnsafe(r3, r6, r9)
+L3:
+    r10 = r6 + 1
+    r6 = r10
+    goto L1
+L4:
+    a = r3
+    return 1
+
+[case testTupleBuiltFromBytes_64bit]
+def f2(val: int) -> int:
+    return val + 2
+
+def test() -> None:
+    source = b"abc"
+    a = tuple(f2(x) for x in source)
+
+[out]
+def f2(val):
+    val, r0 :: int
+L0:
+    r0 = CPyTagged_Add(val, 4)
+    return r0
+def test():
+    r0, source :: bytes
+    r1 :: native_int
+    r2 :: tuple
+    r3, r4 :: native_int
+    r5, r6, r7 :: bit
+    r8, r9, r10, r11 :: int
+    r12 :: object
+    r13, x, r14 :: int
+    r15 :: object
+    r16 :: native_int
+    a :: tuple
+L0:
+    r0 = b'abc'
+    source = r0
+    r1 = var_object_size source
+    r2 = PyTuple_New(r1)
+    r3 = var_object_size source
     r4 = 0
 L1:
-    r5 = CPyStr_Size_size_t(source)
-    r6 = r5 >= 0 :: signed
-    r7 = r5 << 1
-    r8 = int_lt r4, r7
-    if r8 goto L2 else goto L4 :: bool
+    r5 = r4 < r3 :: signed
+    if r5 goto L2 else goto L8 :: bool
 L2:
-    r9 = CPyStr_GetItem(source, r4)
-    x = r9
-    r10 = f2(x)
-    r11 = CPySequenceTuple_SetItemUnsafe(r3, r4, r10)
+    r6 = r4 <= 4611686018427387903 :: signed
+    if r6 goto L3 else goto L4 :: bool
 L3:
-    r12 = r4 + 2
-    r4 = r12
+    r7 = r4 >= -4611686018427387904 :: signed
+    if r7 goto L5 else goto L4 :: bool
+L4:
+    r8 = CPyTagged_FromInt64(r4)
+    r9 = r8
+    goto L6
+L5:
+    r10 = r4 << 1
+    r9 = r10
+L6:
+    r11 = CPyBytes_GetItem(source, r9)
+    r12 = box(int, r11)
+    r13 = unbox(int, r12)
+    x = r13
+    r14 = f2(x)
+    r15 = box(int, r14)
+    CPySequenceTuple_SetItemUnsafe(r2, r4, r15)
+L7:
+    r16 = r4 + 1
+    r4 = r16
+    goto L1
+L8:
+    a = r2
+    return 1
+
+[case testTupleBuiltFromBytesExpr_64bit]
+def f2(val: int) -> int:
+    return val + 2
+
+def test() -> None:
+    a = tuple(f2(x) for x in b"abc")
+
+[out]
+def f2(val):
+    val, r0 :: int
+L0:
+    r0 = CPyTagged_Add(val, 4)
+    return r0
+def test():
+    r0 :: bytes
+    r1 :: native_int
+    r2 :: tuple
+    r3, r4 :: native_int
+    r5, r6, r7 :: bit
+    r8, r9, r10, r11 :: int
+    r12 :: object
+    r13, x, r14 :: int
+    r15 :: object
+    r16 :: native_int
+    a :: tuple
+L0:
+    r0 = b'abc'
+    r1 = var_object_size r0
+    r2 = PyTuple_New(r1)
+    r3 = var_object_size r0
+    r4 = 0
+L1:
+    r5 = r4 < r3 :: signed
+    if r5 goto L2 else goto L8 :: bool
+L2:
+    r6 = r4 <= 4611686018427387903 :: signed
+    if r6 goto L3 else goto L4 :: bool
+L3:
+    r7 = r4 >= -4611686018427387904 :: signed
+    if r7 goto L5 else goto L4 :: bool
+L4:
+    r8 = CPyTagged_FromInt64(r4)
+    r9 = r8
+    goto L6
+L5:
+    r10 = r4 << 1
+    r9 = r10
+L6:
+    r11 = CPyBytes_GetItem(r0, r9)
+    r12 = box(int, r11)
+    r13 = unbox(int, r12)
+    x = r13
+    r14 = f2(x)
+    r15 = box(int, r14)
+    CPySequenceTuple_SetItemUnsafe(r2, r4, r15)
+L7:
+    r16 = r4 + 1
+    r4 = r16
     goto L1
+L8:
+    a = r2
+    return 1
+
+[case testTupleBuiltFromFinalBytes_64bit]
+from typing import Final
+
+source: Final = b"abc"
+
+def f2(val: int) -> int:
+    return val + 2
+
+def test() -> None:
+    a = tuple(f2(x) for x in source)
+
+[out]
+def f2(val):
+    val, r0 :: int
+L0:
+    r0 = CPyTagged_Add(val, 4)
+    return r0
+def test():
+    r0 :: bytes
+    r1 :: bool
+    r2 :: native_int
+    r3 :: tuple
+    r4, r5 :: native_int
+    r6, r7, r8 :: bit
+    r9, r10, r11, r12 :: int
+    r13 :: object
+    r14, x, r15 :: int
+    r16 :: object
+    r17 :: native_int
+    a :: tuple
+L0:
+    r0 = __main__.source :: static
+    if is_error(r0) goto L1 else goto L2
+L1:
+    r1 = raise NameError('value for final name "source" was not set')
+    unreachable
+L2:
+    r2 = var_object_size r0
+    r3 = PyTuple_New(r2)
+    r4 = var_object_size r0
+    r5 = 0
+L3:
+    r6 = r5 < r4 :: signed
+    if r6 goto L4 else goto L10 :: bool
 L4:
+    r7 = r5 <= 4611686018427387903 :: signed
+    if r7 goto L5 else goto L6 :: bool
+L5:
+    r8 = r5 >= -4611686018427387904 :: signed
+    if r8 goto L7 else goto L6 :: bool
+L6:
+    r9 = CPyTagged_FromInt64(r5)
+    r10 = r9
+    goto L8
+L7:
+    r11 = r5 << 1
+    r10 = r11
+L8:
+    r12 = CPyBytes_GetItem(r0, r10)
+    r13 = box(int, r12)
+    r14 = unbox(int, r13)
+    x = r14
+    r15 = f2(x)
+    r16 = box(int, r15)
+    CPySequenceTuple_SetItemUnsafe(r3, r5, r16)
+L9:
+    r17 = r5 + 1
+    r5 = r17
+    goto L3
+L10:
     a = r3
     return 1
 
+[case testTupleBuiltFromFixedLengthTuple]
+def f(val: int) -> bool:
+    return val % 2 == 0
+
+def test() -> None:
+    source = (1, 2, 3)
+    a = tuple(f(x) for x in source)
+[out]
+def f(val):
+    val, r0 :: int
+    r1 :: bit
+L0:
+    r0 = CPyTagged_Remainder(val, 4)
+    r1 = int_eq r0, 0
+    return r1
+def test():
+    r0, source :: tuple[int, int, int]
+    r1 :: list
+    r2, r3, r4 :: object
+    r5, x :: int
+    r6 :: bool
+    r7 :: object
+    r8 :: i32
+    r9, r10 :: bit
+    r11, a :: tuple
+L0:
+    r0 = (2, 4, 6)
+    source = r0
+    r1 = PyList_New(0)
+    r2 = box(tuple[int, int, int], source)
+    r3 = PyObject_GetIter(r2)
+L1:
+    r4 = PyIter_Next(r3)
+    if is_error(r4) goto L4 else goto L2
+L2:
+    r5 = unbox(int, r4)
+    x = r5
+    r6 = f(x)
+    r7 = box(bool, r6)
+    r8 = PyList_Append(r1, r7)
+    r9 = r8 >= 0 :: signed
+L3:
+    goto L1
+L4:
+    r10 = CPy_NoErrOccurred()
+L5:
+    r11 = PyList_AsTuple(r1)
+    a = r11
+    return 1
+
+[case testTupleBuiltFromFinalFixedLengthTuple]
+from typing import Final
+
+source: Final = (1, 2, 3)
+
+def f(val: int) -> bool:
+    return val % 2 == 0
+
+def test() -> None:
+    a = tuple(f(x) for x in source)
+[out]
+def f(val):
+    val, r0 :: int
+    r1 :: bit
+L0:
+    r0 = CPyTagged_Remainder(val, 4)
+    r1 = int_eq r0, 0
+    return r1
+def test():
+    r0 :: list
+    r1 :: tuple[int, int, int]
+    r2 :: bool
+    r3, r4, r5 :: object
+    r6, x :: int
+    r7 :: bool
+    r8 :: object
+    r9 :: i32
+    r10, r11 :: bit
+    r12, a :: tuple
+L0:
+    r0 = PyList_New(0)
+    r1 = __main__.source :: static
+    if is_error(r1) goto L1 else goto L2
+L1:
+    r2 = raise NameError('value for final name "source" was not set')
+    unreachable
+L2:
+    r3 = box(tuple[int, int, int], r1)
+    r4 = PyObject_GetIter(r3)
+L3:
+    r5 = PyIter_Next(r4)
+    if is_error(r5) goto L6 else goto L4
+L4:
+    r6 = unbox(int, r5)
+    x = r6
+    r7 = f(x)
+    r8 = box(bool, r7)
+    r9 = PyList_Append(r0, r8)
+    r10 = r9 >= 0 :: signed
+L5:
+    goto L3
+L6:
+    r11 = CPy_NoErrOccurred()
+L7:
+    r12 = PyList_AsTuple(r0)
+    a = r12
+    return 1
+
 [case testTupleBuiltFromVariableLengthTuple]
 from typing import Tuple
 
@@ -351,35 +825,31 @@ def test(source):
     source :: tuple
     r0 :: native_int
     r1 :: tuple
-    r2 :: short_int
-    r3 :: native_int
-    r4 :: short_int
-    r5 :: bit
-    r6 :: object
-    r7, x, r8 :: bool
-    r9 :: object
-    r10 :: bit
-    r11 :: short_int
+    r2, r3 :: native_int
+    r4 :: bit
+    r5 :: object
+    r6, x, r7 :: bool
+    r8 :: object
+    r9 :: native_int
     a :: tuple
 L0:
     r0 = var_object_size source
     r1 = PyTuple_New(r0)
-    r2 = 0
+    r2 = var_object_size source
+    r3 = 0
 L1:
-    r3 = var_object_size source
-    r4 = r3 << 1
-    r5 = int_lt r2, r4
-    if r5 goto L2 else goto L4 :: bool
+    r4 = r3 < r2 :: signed
+    if r4 goto L2 else goto L4 :: bool
 L2:
-    r6 = CPySequenceTuple_GetItem(source, r2)
-    r7 = unbox(bool, r6)
-    x = r7
-    r8 = f(x)
-    r9 = box(bool, r8)
-    r10 = CPySequenceTuple_SetItemUnsafe(r1, r2, r9)
+    r5 = CPySequenceTuple_GetItemUnsafe(source, r3)
+    r6 = unbox(bool, r5)
+    x = r6
+    r7 = f(x)
+    r8 = box(bool, r7)
+    CPySequenceTuple_SetItemUnsafe(r1, r3, r8)
 L3:
-    r11 = r2 + 2
-    r2 = r11
+    r9 = r3 + 1
+    r3 = r9
     goto L1
 L4:
     a = r1
@@ -453,3 +923,26 @@ L0:
     r0 = CPySequence_Multiply(a, 4)
     b = r0
     return 1
+
+[case testTupleFloatElementComparison]
+def f(x: tuple[float], y: tuple[float]) -> bool:
+    return x == y
+
+[out]
+def f(x, y):
+    x, y :: tuple[float]
+    r0, r1 :: float
+    r2 :: bit
+    r3 :: bool
+L0:
+    r0 = x[0]
+    r1 = y[0]
+    r2 = r0 == r1
+    if not r2 goto L1 else goto L2 :: bool
+L1:
+    r3 = 0
+    goto L3
+L2:
+    r3 = 1
+L3:
+    return r3
diff --git a/mypyc/test-data/irbuild-unreachable.test b/mypyc/test-data/irbuild-unreachable.test
index 7209c00ce75d..a4f1ef8c7dba 100644
--- a/mypyc/test-data/irbuild-unreachable.test
+++ b/mypyc/test-data/irbuild-unreachable.test
@@ -11,50 +11,27 @@ def f():
     r1 :: str
     r2 :: object
     r3, r4 :: str
-    r5 :: i32
-    r6 :: bit
-    r7 :: object
-    r8, r9, r10 :: bit
-    r11, r12 :: bool
-    r13 :: object
-    r14 :: str
-    r15 :: object
-    r16 :: tuple[int, int]
-    r17, r18 :: object
-    r19, y :: bool
+    r5, r6, r7 :: bool
+    r8 :: object
+    r9, y :: bool
 L0:
     r0 = sys :: module
     r1 = 'platform'
     r2 = CPyObject_GetAttr(r0, r1)
     r3 = cast(str, r2)
     r4 = 'x'
-    r5 = PyUnicode_Compare(r3, r4)
-    r6 = r5 == -1
-    if r6 goto L1 else goto L3 :: bool
+    r5 = CPyStr_Equal(r3, r4)
+    if r5 goto L2 else goto L1 :: bool
 L1:
-    r7 = PyErr_Occurred()
-    r8 = r7 != 0
-    if r8 goto L2 else goto L3 :: bool
+    r6 = r5
+    goto L3
 L2:
-    r9 = CPy_KeepPropagating()
+    r7 = raise RuntimeError('mypyc internal error: should be unreachable')
+    r8 = box(None, 1)
+    r9 = unbox(bool, r8)
+    r6 = r9
 L3:
-    r10 = r5 == 0
-    if r10 goto L5 else goto L4 :: bool
-L4:
-    r11 = r10
-    goto L6
-L5:
-    r12 = raise RuntimeError('mypyc internal error: should be unreachable')
-    r13 = box(None, 1)
-    r14 = 'version_info'
-    r15 = CPyObject_GetAttr(r13, r14)
-    r16 = (6, 10)
-    r17 = box(tuple[int, int], r16)
-    r18 = PyObject_RichCompare(r15, r17, 4)
-    r19 = unbox(bool, r18)
-    r11 = r19
-L6:
-    y = r11
+    y = r6
     return 1
 
 [case testUnreachableNameExpr]
@@ -68,41 +45,27 @@ def f():
     r1 :: str
     r2 :: object
     r3, r4 :: str
-    r5 :: i32
-    r6 :: bit
-    r7 :: object
-    r8, r9, r10 :: bit
-    r11, r12 :: bool
-    r13 :: object
-    r14, y :: bool
+    r5, r6, r7 :: bool
+    r8 :: object
+    r9, y :: bool
 L0:
     r0 = sys :: module
     r1 = 'platform'
     r2 = CPyObject_GetAttr(r0, r1)
     r3 = cast(str, r2)
     r4 = 'x'
-    r5 = PyUnicode_Compare(r3, r4)
-    r6 = r5 == -1
-    if r6 goto L1 else goto L3 :: bool
+    r5 = CPyStr_Equal(r3, r4)
+    if r5 goto L2 else goto L1 :: bool
 L1:
-    r7 = PyErr_Occurred()
-    r8 = r7 != 0
-    if r8 goto L2 else goto L3 :: bool
+    r6 = r5
+    goto L3
 L2:
-    r9 = CPy_KeepPropagating()
+    r7 = raise RuntimeError('mypyc internal error: should be unreachable')
+    r8 = box(None, 1)
+    r9 = unbox(bool, r8)
+    r6 = r9
 L3:
-    r10 = r5 == 0
-    if r10 goto L5 else goto L4 :: bool
-L4:
-    r11 = r10
-    goto L6
-L5:
-    r12 = raise RuntimeError('mypyc internal error: should be unreachable')
-    r13 = box(None, 1)
-    r14 = unbox(bool, r13)
-    r11 = r14
-L6:
-    y = r11
+    y = r6
     return 1
 
 [case testUnreachableStatementAfterReturn]
diff --git a/mypyc/test-data/irbuild-weakref.test b/mypyc/test-data/irbuild-weakref.test
new file mode 100644
index 000000000000..2180b1e747aa
--- /dev/null
+++ b/mypyc/test-data/irbuild-weakref.test
@@ -0,0 +1,103 @@
+[case testWeakrefRef]
+import weakref
+from typing import Any, Callable
+def f(x: object) -> object:
+    return weakref.ref(x)
+
+[out]
+def f(x):
+    x, r0 :: object
+L0:
+    r0 = PyWeakref_NewRef(x, 0)
+    return r0
+
+[case testWeakrefRefCallback]
+import weakref
+from typing import Any, Callable
+def f(x: object, cb: Callable[[object], Any]) -> object:
+    return weakref.ref(x, cb)
+
+[out]
+def f(x, cb):
+    x, cb, r0 :: object
+L0:
+    r0 = PyWeakref_NewRef(x, cb)
+    return r0
+
+[case testFromWeakrefRef]
+from typing import Any, Callable
+from weakref import ref
+def f(x: object) -> object:
+    return ref(x)
+
+[out]
+def f(x):
+    x, r0 :: object
+L0:
+    r0 = PyWeakref_NewRef(x, 0)
+    return r0
+
+[case testFromWeakrefRefCallback]
+from typing import Any, Callable
+from weakref import ref
+def f(x: object, cb: Callable[[object], Any]) -> object:
+    return ref(x, cb)
+
+[out]
+def f(x, cb):
+    x, cb, r0 :: object
+L0:
+    r0 = PyWeakref_NewRef(x, cb)
+    return r0
+
+[case testWeakrefProxy]
+import weakref
+from typing import Any, Callable
+def f(x: object) -> object:
+    return weakref.proxy(x)
+
+[out]
+def f(x):
+    x, r0 :: object
+L0:
+    r0 = PyWeakref_NewProxy(x, 0)
+    return r0
+
+[case testWeakrefProxyCallback]
+import weakref
+from typing import Any, Callable
+def f(x: object, cb: Callable[[object], Any]) -> object:
+    return weakref.proxy(x, cb)
+
+[out]
+def f(x, cb):
+    x, cb, r0 :: object
+L0:
+    r0 = PyWeakref_NewProxy(x, cb)
+    return r0
+
+[case testFromWeakrefProxy]
+from typing import Any, Callable
+from weakref import proxy
+def f(x: object) -> object:
+    return proxy(x)
+
+[out]
+def f(x):
+    x, r0 :: object
+L0:
+    r0 = PyWeakref_NewProxy(x, 0)
+    return r0
+
+[case testFromWeakrefProxyCallback]
+from typing import Any, Callable
+from weakref import proxy
+def f(x: object, cb: Callable[[object], Any]) -> object:
+    return proxy(x, cb)
+
+[out]
+def f(x, cb):
+    x, cb, r0 :: object
+L0:
+    r0 = PyWeakref_NewProxy(x, cb)
+    return r0
diff --git a/mypyc/test-data/lowering-int.test b/mypyc/test-data/lowering-int.test
index ad561c561872..c2bcba54e444 100644
--- a/mypyc/test-data/lowering-int.test
+++ b/mypyc/test-data/lowering-int.test
@@ -341,47 +341,42 @@ def f(l: list[int]) -> None:
 [out]
 def f(l):
     l :: list
-    r0 :: short_int
+    r0 :: native_int
     r1 :: ptr
     r2 :: native_int
-    r3 :: short_int
-    r4 :: bit
-    r5 :: native_int
-    r6, r7 :: ptr
-    r8 :: native_int
-    r9 :: ptr
-    r10 :: object
-    r11, x :: int
-    r12 :: short_int
-    r13 :: None
+    r3 :: bit
+    r4, r5 :: ptr
+    r6 :: native_int
+    r7 :: ptr
+    r8 :: object
+    r9, x :: int
+    r10 :: native_int
+    r11 :: None
 L0:
     r0 = 0
 L1:
     r1 = get_element_ptr l ob_size :: PyVarObject
     r2 = load_mem r1 :: native_int*
-    r3 = r2 << 1
-    r4 = r0 < r3 :: signed
-    if r4 goto L2 else goto L5 :: bool
+    r3 = r0 < r2 :: signed
+    if r3 goto L2 else goto L5 :: bool
 L2:
-    r5 = r0 >> 1
-    r6 = get_element_ptr l ob_item :: PyListObject
-    r7 = load_mem r6 :: ptr*
-    r8 = r5 * 8
-    r9 = r7 + r8
-    r10 = load_mem r9 :: builtins.object*
-    inc_ref r10
-    r11 = unbox(int, r10)
-    dec_ref r10
-    if is_error(r11) goto L6 (error at f:4) else goto L3
+    r4 = get_element_ptr l ob_item :: PyListObject
+    r5 = load_mem r4 :: ptr*
+    r6 = r0 * 8
+    r7 = r5 + r6
+    r8 = load_mem r7 :: builtins.object*
+    r9 = unbox(int, r8)
+    dec_ref r8
+    if is_error(r9) goto L6 (error at f:4) else goto L3
 L3:
-    x = r11
+    x = r9
     dec_ref x :: int
 L4:
-    r12 = r0 + 2
-    r0 = r12
+    r10 = r0 + 1
+    r0 = r10
     goto L1
 L5:
     return 1
 L6:
-    r13 = <error> :: None
-    return r13
+    r11 = <error> :: None
+    return r11
diff --git a/mypyc/test-data/refcount.test b/mypyc/test-data/refcount.test
index 22153cff5a91..a71c53041cf7 100644
--- a/mypyc/test-data/refcount.test
+++ b/mypyc/test-data/refcount.test
@@ -730,49 +730,47 @@ def f(d):
     d :: dict
     r0 :: short_int
     r1 :: native_int
-    r2 :: short_int
-    r3 :: object
-    r4 :: tuple[bool, short_int, object]
-    r5 :: short_int
-    r6 :: bool
-    r7 :: object
-    r8, key :: int
-    r9, r10 :: object
-    r11 :: int
-    r12, r13 :: bit
+    r2 :: object
+    r3 :: tuple[bool, short_int, object]
+    r4 :: short_int
+    r5 :: bool
+    r6 :: object
+    r7, key :: int
+    r8, r9 :: object
+    r10 :: int
+    r11, r12 :: bit
 L0:
     r0 = 0
     r1 = PyDict_Size(d)
-    r2 = r1 << 1
-    r3 = CPyDict_GetKeysIter(d)
+    r2 = CPyDict_GetKeysIter(d)
 L1:
-    r4 = CPyDict_NextKey(r3, r0)
-    r5 = r4[1]
-    r0 = r5
-    r6 = r4[0]
-    if r6 goto L2 else goto L6 :: bool
+    r3 = CPyDict_NextKey(r2, r0)
+    r4 = r3[1]
+    r0 = r4
+    r5 = r3[0]
+    if r5 goto L2 else goto L6 :: bool
 L2:
-    r7 = r4[2]
-    dec_ref r4
-    r8 = unbox(int, r7)
-    dec_ref r7
-    key = r8
-    r9 = box(int, key)
-    r10 = CPyDict_GetItem(d, r9)
+    r6 = r3[2]
+    dec_ref r3
+    r7 = unbox(int, r6)
+    dec_ref r6
+    key = r7
+    r8 = box(int, key)
+    r9 = CPyDict_GetItem(d, r8)
+    dec_ref r8
+    r10 = unbox(int, r9)
     dec_ref r9
-    r11 = unbox(int, r10)
-    dec_ref r10
-    dec_ref r11 :: int
+    dec_ref r10 :: int
 L3:
-    r12 = CPyDict_CheckSize(d, r2)
+    r11 = CPyDict_CheckSize(d, r1)
     goto L1
 L4:
-    r13 = CPy_NoErrOccurred()
+    r12 = CPy_NoErrOccurred()
 L5:
     return 1
 L6:
+    dec_ref r2
     dec_ref r3
-    dec_ref r4
     goto L4
 
 [case testBorrowRefs]
@@ -1119,7 +1117,7 @@ L0:
     r0 = borrow x.a
     r1 = __main__.D :: type
     r2 = get_element_ptr r0 ob_type :: PyObject
-    r3 = load_mem r2 :: builtins.object*
+    r3 = borrow load_mem r2 :: builtins.object*
     r4 = r3 == r1
     if r4 goto L1 else goto L2 :: bool
 L1:
diff --git a/mypyc/test-data/run-async.test b/mypyc/test-data/run-async.test
index 11ce67077270..55cde4ab44f1 100644
--- a/mypyc/test-data/run-async.test
+++ b/mypyc/test-data/run-async.test
@@ -2,6 +2,7 @@
 
 [case testRunAsyncBasics]
 import asyncio
+from typing import Callable, Awaitable
 
 from testutil import assertRaises
 
@@ -21,12 +22,12 @@ async def f2() -> int:
         x += i + await f() + await g()
     return x
 
-def test_simple_call() -> None:
-    result = asyncio.run(f())
+async def test_simple_call() -> None:
+    result = await f()
     assert result == 3
 
-def test_multiple_awaits_in_expression() -> None:
-    result = asyncio.run(f2())
+async def test_multiple_awaits_in_expression() -> None:
+    result = await f2()
     assert result == 9
 
 class MyError(Exception):
@@ -60,22 +61,77 @@ async def exc6() -> int:
         return 3
     return 4
 
-def test_exception() -> None:
+async def test_exception() -> None:
     with assertRaises(MyError):
-        asyncio.run(exc1())
+        await exc1()
+    with assertRaises(MyError):
+        await exc2()
+    with assertRaises(MyError):
+        await exc3()
+    with assertRaises(MyError):
+        await exc4()
+    assert await exc5() == 3
+    assert await exc6() == 3
+
+async def indirect_call(x: int, c: Callable[[int], Awaitable[int]]) -> int:
+    return await c(x)
+
+async def indirect_call_2(a: Awaitable[None]) -> None:
+    await a
+
+async def indirect_call_3(a: Awaitable[float]) -> float:
+    return (await a) + 1.0
+
+async def inc(x: int) -> int:
+    await asyncio.sleep(0)
+    return x + 1
+
+async def ident(x: float, err: bool = False) -> float:
+    await asyncio.sleep(0.0)
+    if err:
+        raise MyError()
+    return x + float("0.0")
+
+async def test_indirect_call() -> None:
+    assert await indirect_call(3, inc) == 4
+
     with assertRaises(MyError):
-        asyncio.run(exc2())
+        await indirect_call_2(exc1())
+
+    assert await indirect_call_3(ident(2.0)) == 3.0
+    assert await indirect_call_3(ident(-113.0)) == -112.0
+    assert await indirect_call_3(ident(-114.0)) == -113.0
+
     with assertRaises(MyError):
-        asyncio.run(exc3())
+        await indirect_call_3(ident(1.0, True))
+    with assertRaises(MyError):
+        await indirect_call_3(ident(-113.0, True))
+
+class C:
+    def __init__(self, n: int) -> None:
+        self.n = n
+
+    async def add(self, x: int, err: bool = False) -> int:
+        await asyncio.sleep(0)
+        if err:
+            raise MyError()
+        return x + self.n
+
+async def method_call(x: int) -> int:
+    c = C(5)
+    return await c.add(x)
+
+async def method_call_exception() -> int:
+    c = C(5)
+    return await c.add(3, err=True)
+
+async def test_async_method_call() -> None:
+    assert await method_call(3) == 8
     with assertRaises(MyError):
-        asyncio.run(exc4())
-    assert asyncio.run(exc5()) == 3
-    assert asyncio.run(exc6()) == 3
+        await method_call_exception()
 
 [file asyncio/__init__.pyi]
 async def sleep(t: float) -> None: ...
-# eh, we could use the real type but it doesn't seem important
-def run(x: object) -> object: ...
 
 [typing fixtures/typing-full.pyi]
 
@@ -101,16 +157,16 @@ async def branch_await_not() -> int:
         return 3
     return 2
 
-def test_branch() -> None:
-    assert asyncio.run(branch_await()) == 3
-    assert asyncio.run(branch_await_not()) == 2
+async def test_branch() -> None:
+    assert await branch_await() == 3
+    assert await branch_await_not() == 2
 
 async def assign_multi() -> int:
     _, x = int(), await one()
     return x + 1
 
-def test_assign_multi() -> None:
-    assert asyncio.run(assign_multi()) == 2
+async def test_assign_multi() -> None:
+    assert await assign_multi() == 2
 
 class C:
     def __init__(self, s: str) -> None:
@@ -130,8 +186,8 @@ async def concat(s: str, t: str) -> str:
 async def set_attr(s: str) -> None:
     (await make_c("xyz")).s = await concat(s, "!")
 
-def test_set_attr() -> None:
-    asyncio.run(set_attr("foo"))  # Just check that it compiles and runs
+async def test_set_attr() -> None:
+    await set_attr("foo")  # Just check that it compiles and runs
 
 def concat2(x: str, y: str) -> str:
     return x + y
@@ -142,15 +198,15 @@ async def call1(s: str) -> str:
 async def call2(s: str) -> str:
     return await concat(str(int()), await concat(s, "b"))
 
-def test_call() -> None:
-    assert asyncio.run(call1("foo")) == "0fooa"
-    assert asyncio.run(call2("foo")) == "0foob"
+async def test_call() -> None:
+    assert await call1("foo") == "0fooa"
+    assert await call2("foo") == "0foob"
 
 async def method_call(s: str) -> str:
     return C("<").concat(await concat(s, ">"))
 
-def test_method_call() -> None:
-    assert asyncio.run(method_call("foo")) == "<foo>"
+async def test_method_call() -> None:
+    assert await method_call("foo") == "<foo>"
 
 class D:
     def __init__(self, a: str, b: str) -> None:
@@ -161,13 +217,11 @@ async def construct(s: str) -> str:
     c = D(await concat(s, "!"), await concat(s, "?"))
     return c.a + c.b
 
-def test_construct() -> None:
-    assert asyncio.run(construct("foo")) == "foo!foo?"
+async def test_construct() -> None:
+    assert await construct("foo") == "foo!foo?"
 
 [file asyncio/__init__.pyi]
 async def sleep(t: float) -> None: ...
-# eh, we could use the real type but it doesn't seem important
-def run(x: object) -> object: ...
 
 [typing fixtures/typing-full.pyi]
 
@@ -303,7 +357,7 @@ class ConManB:
     async def __aexit__(self, *exc: object):
         pass
 
-async def x() -> None:
+async def test_x() -> None:
     value = 2
     async with ConMan() as f:
         value += f
@@ -312,12 +366,6 @@ async def x() -> None:
         value += f
     assert value == 5, value
 
-[typing fixtures/typing-full.pyi]
-[file driver.py]
-import asyncio
-import native
-asyncio.run(native.x())
-
 [case testRunAsyncSpecialCases]
 import asyncio
 
@@ -327,8 +375,8 @@ async def t() -> tuple[int, str, str]:
 async def f() -> tuple[int, str, str]:
     return await t()
 
-def test_tuple_return() -> None:
-    result = asyncio.run(f())
+async def test_tuple_return() -> None:
+    result = await f()
     assert result == (1, "x", "y")
 
 async def e() -> ValueError:
@@ -337,14 +385,12 @@ async def e() -> ValueError:
 async def g() -> ValueError:
     return await e()
 
-def test_exception_return() -> None:
-    result = asyncio.run(g())
+async def test_exception_return() -> None:
+    result = await g()
     assert isinstance(result, ValueError)
 
 [file asyncio/__init__.pyi]
 async def sleep(t: float) -> None: ...
-# eh, we could use the real type but it doesn't seem important
-def run(x: object) -> object: ...
 
 [typing fixtures/typing-full.pyi]
 
@@ -352,15 +398,15 @@ def run(x: object) -> object: ...
 import asyncio
 import gc
 
-def assert_no_leaks(fn, max_new):
+async def assert_no_leaks(fn, max_new):
     # Warm-up, in case asyncio allocates something on first use
-    asyncio.run(fn())
+    await fn()
 
     gc.collect()
     old_objs = gc.get_objects()
 
     for i in range(10):
-        asyncio.run(fn())
+        await fn()
 
     gc.collect()
     new_objs = gc.get_objects()
@@ -380,8 +426,8 @@ async def foo(n: int) -> str:
         s = await concat_one(s)
     return s
 
-def test_trivial() -> None:
-    assert_no_leaks(lambda: foo(1000), 5)
+async def test_trivial() -> None:
+    await assert_no_leaks(lambda: foo(1000), 5)
 
 async def make_list(a: list[int]) -> list[int]:
     await concat_one("foobar")
@@ -398,8 +444,8 @@ async def bar(n: int) -> None:
     for i in range(n):
         await spill()
 
-def test_spilled() -> None:
-    assert_no_leaks(lambda: bar(40), 2)
+async def test_spilled() -> None:
+    await assert_no_leaks(lambda: bar(80), 2)
 
 async def raise_deep(n: int) -> str:
     if n == 0:
@@ -426,8 +472,8 @@ async def exc(n: int) -> list[str]:
             a.append(str(int() + 5))
     return a
 
-def test_exception() -> None:
-    assert_no_leaks(lambda: exc(50), 2)
+async def test_exception() -> None:
+    await assert_no_leaks(lambda: exc(50), 2)
 
 class C:
     def __init__(self, s: str) -> None:
@@ -449,11 +495,10 @@ async def stolen(n: int) -> int:
         assert s == str(i + 2) + "1"
     return n
 
-def test_stolen() -> None:
-    assert_no_leaks(lambda: stolen(100), 2)
+async def test_stolen() -> None:
+    await assert_no_leaks(lambda: stolen(200), 2)
 
 [file asyncio/__init__.pyi]
-def run(x: object) -> object: ...
 async def sleep(t: float) -> None: ...
 
 [case testRunAsyncMiscTypesInEnvironment]
@@ -501,8 +546,8 @@ async def float_ops(x: float) -> float:
     n = float("0.5") + await inc_float(n)
     return n
 
-def test_float() -> None:
-    assert asyncio.run(float_ops(2.5)) == 5.0
+async def test_float() -> None:
+    assert await float_ops(2.5) == 5.0
 
 async def i64_ops(x: i64) -> i64:
     n = x
@@ -510,8 +555,8 @@ async def i64_ops(x: i64) -> i64:
     n = i64("1") + await inc_i64(n)
     return n
 
-def test_i64() -> None:
-    assert asyncio.run(i64_ops(2)) == 5
+async def test_i64() -> None:
+    assert await i64_ops(2) == 5
 
 async def i32_ops(x: i32) -> i32:
     n = x
@@ -519,8 +564,8 @@ async def i32_ops(x: i32) -> i32:
     n = i32("1") + await inc_i32(n)
     return n
 
-def test_i32() -> None:
-    assert asyncio.run(i32_ops(3)) == 6
+async def test_i32() -> None:
+    assert await i32_ops(3) == 6
 
 async def i16_ops(x: i16) -> i16:
     n = x
@@ -528,8 +573,8 @@ async def i16_ops(x: i16) -> i16:
     n = i16("1") + await inc_i16(n)
     return n
 
-def test_i16() -> None:
-    assert asyncio.run(i16_ops(4)) == 7
+async def test_i16() -> None:
+    assert await i16_ops(4) == 7
 
 async def u8_ops(x: u8) -> u8:
     n = x
@@ -537,8 +582,8 @@ async def u8_ops(x: u8) -> u8:
     n = u8("1") + await inc_u8(n)
     return n
 
-def test_u8() -> None:
-    assert asyncio.run(u8_ops(5)) == 8
+async def test_u8() -> None:
+    assert await u8_ops(5) == 8
 
 async def tuple_ops(x: tuple[i64, float]) -> tuple[i64, float]:
     n = x
@@ -546,8 +591,8 @@ async def tuple_ops(x: tuple[i64, float]) -> tuple[i64, float]:
     m = ((i64("1"), float("0.5")), await inc_tuple(n))
     return m[1]
 
-def test_tuple() -> None:
-    assert asyncio.run(tuple_ops((1, 2.5))) == (3, 5.5)
+async def test_tuple() -> None:
+    assert await tuple_ops((1, 2.5)) == (3, 5.5)
 
 async def bool_ops(x: bool) -> bool:
     n = x
@@ -555,16 +600,18 @@ async def bool_ops(x: bool) -> bool:
     m = (bool("1"), await neg_bool(n))
     return m[0] and m[1]
 
-def test_bool() -> None:
-    assert asyncio.run(bool_ops(True)) is True
-    assert asyncio.run(bool_ops(False)) is False
+async def test_bool() -> None:
+    assert await bool_ops(True) is True
+    assert await bool_ops(False) is False
 
 [file asyncio/__init__.pyi]
 def run(x: object) -> object: ...
 
 [case testRunAsyncNestedFunctions]
+from __future__ import annotations
+
 import asyncio
-from typing import cast, Iterator
+from typing import cast, Iterator, overload, Awaitable, Any, TypeVar
 
 from testutil import assertRaises
 
@@ -588,8 +635,8 @@ async def async_def_contains_normal(x: int) -> int:
     a += nested((await inc(3)), (await inc(4)))
     return a
 
-def test_async_def_contains_normal() -> None:
-    assert normal_contains_async_def(2) == (2 + 2 + 4 + 5)
+async def test_async_def_contains_normal() -> None:
+    assert await async_def_contains_normal(2) == (2 + 2 + 4 + 5)
 
 async def async_def_contains_async_def(x: int) -> int:
     async def f(y: int) -> int:
@@ -597,8 +644,8 @@ async def async_def_contains_async_def(x: int) -> int:
 
     return (await f(1)) + (await f(2))
 
-def test_async_def_contains_async_def() -> None:
-    assert asyncio.run(async_def_contains_async_def(3)) == (3 + 1 + 1 + 1) + (3 + 1 + 2 + 1)
+async def test_async_def_contains_async_def() -> None:
+    assert await async_def_contains_async_def(3) == (3 + 1 + 1 + 1) + (3 + 1 + 2 + 1)
 
 async def async_def_contains_generator(x: int) -> tuple[int, int, int]:
     def gen(y: int) -> Iterator[int]:
@@ -613,8 +660,8 @@ async def async_def_contains_generator(x: int) -> tuple[int, int, int]:
 
     return res
 
-def test_async_def_contains_generator() -> None:
-    assert asyncio.run(async_def_contains_generator(3)) == (13, 4, 7)
+async def test_async_def_contains_generator() -> None:
+    assert await async_def_contains_generator(3) == (13, 4, 7)
 
 def generator_contains_async_def(x: int) -> Iterator[int]:
     async def f(y: int) -> int:
@@ -636,10 +683,554 @@ async def async_def_contains_two_nested_functions(x: int, y: int) -> tuple[int,
 
     return (await inc(f(3))), (await inc(g(4, 10)))
 
-def test_async_def_contains_two_nested_functions() -> None:
-    assert asyncio.run(async_def_contains_two_nested_functions(5, 7)) == (
+async def test_async_def_contains_two_nested_functions() -> None:
+    assert await async_def_contains_two_nested_functions(5, 7) == (
         (5 + 3 + 1), (7 + 4 + 10 + 1)
     )
 
+async def async_def_contains_overloaded_async_def(n: int) -> int:
+    @overload
+    async def f(x: int) -> int: ...
+
+    @overload
+    async def f(x: str) -> str: ...
+
+    async def f(x: int | str) -> Any:
+        return x
+
+    return (await f(n)) + 1
+
+
+async def test_async_def_contains_overloaded_async_def() -> None:
+    assert await async_def_contains_overloaded_async_def(5) == 6
+
+T = TypeVar("T")
+
+def deco(f: T) -> T:
+    return f
+
+async def async_def_contains_decorated_async_def(n: int) -> int:
+    @deco
+    async def f(x: int) -> int:
+        return x + 2
+
+    return (await f(n)) + 1
+
+
+async def test_async_def_contains_decorated_async_def() -> None:
+    assert await async_def_contains_decorated_async_def(7) == 10
+
+[file asyncio/__init__.pyi]
+def run(x: object) -> object: ...
+
+[case testAsyncTryFinallyMixedReturn]
+# This used to raise an AttributeError, when:
+# - the try block contains multiple paths
+# - at least one of those explicitly returns
+# - at least one of those does not explicitly return
+# - the non-returning path is taken at runtime
+
+async def mixed_return(b: bool) -> bool:
+  try:
+      if b:
+          return b
+  finally:
+      pass
+  return b
+
+
+async def test_async_try_finally_mixed_return() -> None:
+  # Test return path
+  result1 = await mixed_return(True)
+  assert result1 == True
+
+  # Test non-return path
+  result2 = await mixed_return(False)
+  assert result2 == False
+
+[case testAsyncWithMixedReturn]
+# This used to raise an AttributeError, related to
+# testAsyncTryFinallyMixedReturn, this is essentially
+# a far more extensive version of that test surfacing
+# more edge cases
+
+from typing import Optional, Type, Literal
+
+
+class AsyncContextManager:
+    async def __aenter__(self) -> "AsyncContextManager":
+        return self
+
+    async def __aexit__(
+        self,
+        t: Optional[Type[BaseException]],
+        v: Optional[BaseException],
+        tb: object,
+    ) -> Literal[False]:
+        return False
+
+
+# Simple async functions (generator class)
+async def gen_1(b: bool) -> bool:
+    async with AsyncContextManager():
+        if b:
+            return b
+    return b
+
+
+async def gen_2(b: bool) -> bool:
+    async with AsyncContextManager():
+        if b:
+            return b
+        else:
+            return b
+
+
+async def gen_3(b: bool) -> bool:
+    async with AsyncContextManager():
+        if b:
+            return b
+        else:
+            pass
+    return b
+
+
+async def gen_4(b: bool) -> bool:
+    ret: bool
+    async with AsyncContextManager():
+        if b:
+            ret = b
+        else:
+            ret = b
+    return ret
+
+
+async def gen_5(i: int) -> int:
+    async with AsyncContextManager():
+        if i == 1:
+            return i
+        elif i == 2:
+            pass
+        elif i == 3:
+            return i
+    return i
+
+
+async def gen_6(i: int) -> int:
+    async with AsyncContextManager():
+        if i == 1:
+            return i
+        elif i == 2:
+            return i
+        elif i == 3:
+            return i
+    return i
+
+
+async def gen_7(i: int) -> int:
+    async with AsyncContextManager():
+        if i == 1:
+            return i
+        elif i == 2:
+            return i
+        elif i == 3:
+            return i
+        else:
+            return i
+
+
+# Async functions with nested functions (environment class)
+async def env_1(b: bool) -> bool:
+    def helper() -> bool:
+        return True
+
+    async with AsyncContextManager():
+        if b:
+            return helper()
+    return b
+
+
+async def env_2(b: bool) -> bool:
+    def helper() -> bool:
+        return True
+
+    async with AsyncContextManager():
+        if b:
+            return helper()
+        else:
+            return b
+
+
+async def env_3(b: bool) -> bool:
+    def helper() -> bool:
+        return True
+
+    async with AsyncContextManager():
+        if b:
+            return helper()
+        else:
+            pass
+    return b
+
+
+async def env_4(b: bool) -> bool:
+    def helper() -> bool:
+        return True
+
+    ret: bool
+    async with AsyncContextManager():
+        if b:
+            ret = helper()
+        else:
+            ret = b
+    return ret
+
+
+async def env_5(i: int) -> int:
+    def helper() -> int:
+        return 1
+
+    async with AsyncContextManager():
+        if i == 1:
+            return helper()
+        elif i == 2:
+            pass
+        elif i == 3:
+            return i
+    return i
+
+
+async def env_6(i: int) -> int:
+    def helper() -> int:
+        return 1
+
+    async with AsyncContextManager():
+        if i == 1:
+            return helper()
+        elif i == 2:
+            return i
+        elif i == 3:
+            return i
+    return i
+
+
+async def env_7(i: int) -> int:
+    def helper() -> int:
+        return 1
+
+    async with AsyncContextManager():
+        if i == 1:
+            return helper()
+        elif i == 2:
+            return i
+        elif i == 3:
+            return i
+        else:
+            return i
+
+
+async def test_async_with_mixed_return() -> None:
+    # Test simple async functions (generator class)
+    # env_1: mixed return/no-return
+    assert await gen_1(True) is True
+    assert await gen_1(False) is False
+
+    # gen_2: all branches return
+    assert await gen_2(True) is True
+    assert await gen_2(False) is False
+
+    # gen_3: mixed return/pass
+    assert await gen_3(True) is True
+    assert await gen_3(False) is False
+
+    # gen_4: no returns in async with
+    assert await gen_4(True) is True
+    assert await gen_4(False) is False
+
+    # gen_5: multiple branches, some return
+    assert await gen_5(0) == 0
+    assert await gen_5(1) == 1
+    assert await gen_5(2) == 2
+    assert await gen_5(3) == 3
+
+    # gen_6: all explicit branches return, implicit fallthrough
+    assert await gen_6(0) == 0
+    assert await gen_6(1) == 1
+    assert await gen_6(2) == 2
+    assert await gen_6(3) == 3
+
+    # gen_7: all branches return including else
+    assert await gen_7(0) == 0
+    assert await gen_7(1) == 1
+    assert await gen_7(2) == 2
+    assert await gen_7(3) == 3
+
+    # Test async functions with nested functions (environment class)
+    # env_1: mixed return/no-return
+    assert await env_1(True) is True
+    assert await env_1(False) is False
+
+    # env_2: all branches return
+    assert await env_2(True) is True
+    assert await env_2(False) is False
+
+    # env_3: mixed return/pass
+    assert await env_3(True) is True
+    assert await env_3(False) is False
+
+    # env_4: no returns in async with
+    assert await env_4(True) is True
+    assert await env_4(False) is False
+
+    # env_5: multiple branches, some return
+    assert await env_5(0) == 0
+    assert await env_5(1) == 1
+    assert await env_5(2) == 2
+    assert await env_5(3) == 3
+
+    # env_6: all explicit branches return, implicit fallthrough
+    assert await env_6(0) == 0
+    assert await env_6(1) == 1
+    assert await env_6(2) == 2
+    assert await env_6(3) == 3
+
+    # env_7: all branches return including else
+    assert await env_7(0) == 0
+    assert await env_7(1) == 1
+    assert await env_7(2) == 2
+    assert await env_7(3) == 3
+
+[case testAsyncTryExceptFinallyAwait]
+import asyncio
+from testutil import assertRaises
+
+class TestError(Exception):
+    pass
+
+# Test 0: Simplest case - just try/finally with raise and await
+async def simple_try_finally_await() -> None:
+    try:
+        raise ValueError("simple error")
+    finally:
+        await asyncio.sleep(0)
+
+# Test 1: Raise inside try, catch in except, don't re-raise
+async def async_try_except_no_reraise() -> int:
+    try:
+        raise ValueError("test error")
+        return 1  # Never reached
+    except ValueError:
+        return 2  # Should return this
+    finally:
+        await asyncio.sleep(0)
+    return 3  # Should not reach this
+
+# Test 2: Raise inside try, catch in except, re-raise
+async def async_try_except_reraise() -> int:
+    try:
+        raise ValueError("test error")
+        return 1  # Never reached
+    except ValueError:
+        raise  # Re-raise the exception
+    finally:
+        await asyncio.sleep(0)
+    return 2  # Should not reach this
+
+# Test 3: Raise inside try, catch in except, raise different error
+async def async_try_except_raise_different() -> int:
+    try:
+        raise ValueError("original error")
+        return 1  # Never reached
+    except ValueError:
+        raise RuntimeError("different error")
+    finally:
+        await asyncio.sleep(0)
+    return 2  # Should not reach this
+
+# Test 4: Another try/except block inside finally
+async def async_try_except_inside_finally() -> int:
+    try:
+        raise ValueError("outer error")
+        return 1  # Never reached
+    finally:
+        await asyncio.sleep(0)
+        try:
+            raise RuntimeError("inner error")
+        except RuntimeError:
+            pass  # Catch inner error
+    return 2  # What happens after finally with inner exception handled?
+
+# Test 5: Another try/finally block inside finally
+async def async_try_finally_inside_finally() -> int:
+    try:
+        raise ValueError("outer error")
+        return 1  # Never reached
+    finally:
+        await asyncio.sleep(0)
+        try:
+            raise RuntimeError("inner error")
+        finally:
+            await asyncio.sleep(0)
+    return 2  # Should not reach this
+
+# Control case: No await in finally - should work correctly
+async def async_exception_no_await_in_finally() -> None:
+    """Control case: This works correctly - exception propagates"""
+    try:
+        raise TestError("This exception will propagate!")
+    finally:
+        pass  # No await here
+
+# Test function with no exception to check normal flow
+async def async_no_exception_with_await_in_finally() -> int:
+    try:
+        return 1  # Normal return
+    finally:
+        await asyncio.sleep(0)
+    return 2  # Should not reach this
+
+async def test_async_try_except_finally_await() -> None:
+    # Test 0: Simplest case - just try/finally with exception
+    # Expected: ValueError propagates
+    with assertRaises(ValueError):
+        await simple_try_finally_await()
+
+    # Test 1: Exception caught, not re-raised
+    # Expected: return 2 (from except block)
+    result = await async_try_except_no_reraise()
+    assert result == 2, f"Expected 2, got {result}"
+
+    # Test 2: Exception caught and re-raised
+    # Expected: ValueError propagates
+    with assertRaises(ValueError):
+        await async_try_except_reraise()
+
+    # Test 3: Exception caught, different exception raised
+    # Expected: RuntimeError propagates
+    with assertRaises(RuntimeError):
+        await async_try_except_raise_different()
+
+    # Test 4: Try/except inside finally
+    # Expected: ValueError propagates (outer exception)
+    with assertRaises(ValueError):
+        await async_try_except_inside_finally()
+
+    # Test 5: Try/finally inside finally
+    # Expected: RuntimeError propagates (inner error)
+    with assertRaises(RuntimeError):
+        await async_try_finally_inside_finally()
+
+    # Control case: No await in finally (should work correctly)
+    with assertRaises(TestError):
+        await async_exception_no_await_in_finally()
+
+    # Test normal flow (no exception)
+    # Expected: return 1
+    result = await async_no_exception_with_await_in_finally()
+    assert result == 1, f"Expected 1, got {result}"
+
+[file asyncio/__init__.pyi]
+async def sleep(t: float) -> None: ...
+
+[case testAsyncContextManagerExceptionHandling]
+import asyncio
+from typing import Optional, Type
+from testutil import assertRaises
+
+# Test 1: Basic async context manager that doesn't suppress exceptions
+class AsyncContextManager:
+    async def __aenter__(self) -> 'AsyncContextManager':
+        return self
+
+    async def __aexit__(self, exc_type: Optional[Type[BaseException]],
+                       exc_val: Optional[BaseException],
+                       exc_tb: object) -> None:
+        # This await in __aexit__ is like await in finally
+        await asyncio.sleep(0)
+        # Don't suppress the exception (return None/False)
+
+async def func_with_async_context_manager() -> str:
+    async with AsyncContextManager():
+        raise ValueError("Exception inside async with")
+        return "should not reach"  # Never reached
+    return "should not reach either"  # Never reached
+
+async def test_basic_exception() -> str:
+    try:
+        await func_with_async_context_manager()
+        return "func_a returned normally - bug!"
+    except ValueError:
+        return "caught ValueError - correct!"
+    except Exception as e:
+        return f"caught different exception: {type(e).__name__}"
+
+# Test 2: Async context manager that raises a different exception in __aexit__
+class AsyncContextManagerRaisesInExit:
+    async def __aenter__(self) -> 'AsyncContextManagerRaisesInExit':
+        return self
+
+    async def __aexit__(self, exc_type: Optional[Type[BaseException]],
+                       exc_val: Optional[BaseException],
+                       exc_tb: object) -> None:
+        # This await in __aexit__ is like await in finally
+        await asyncio.sleep(0)
+        # Raise a different exception - this should replace the original exception
+        raise RuntimeError("Exception in __aexit__")
+
+async def func_with_raising_context_manager() -> str:
+    async with AsyncContextManagerRaisesInExit():
+        raise ValueError("Original exception")
+        return "should not reach"  # Never reached
+    return "should not reach either"  # Never reached
+
+async def test_exception_in_aexit() -> str:
+    try:
+        await func_with_raising_context_manager()
+        return "func returned normally - unexpected!"
+    except RuntimeError:
+        return "caught RuntimeError - correct!"
+    except ValueError:
+        return "caught ValueError - original exception not replaced!"
+    except Exception as e:
+        return f"caught different exception: {type(e).__name__}"
+
+async def test_async_context_manager_exception_handling() -> None:
+    # Test 1: Basic exception propagation
+    result = await test_basic_exception()
+    # Expected: "caught ValueError - correct!"
+    assert result == "caught ValueError - correct!", f"Expected exception to propagate, got: {result}"
+
+    # Test 2: Exception raised in __aexit__ replaces original exception
+    result = await test_exception_in_aexit()
+    # Expected: "caught RuntimeError - correct!"
+    # (The RuntimeError from __aexit__ should replace the ValueError)
+    assert result == "caught RuntimeError - correct!", f"Expected RuntimeError from __aexit__, got: {result}"
+
+[file asyncio/__init__.pyi]
+async def sleep(t: float) -> None: ...
+
+[case testCallableArgWithSameNameAsHelperMethod]
+import asyncio
+from typing import Awaitable, Callable
+
+
+MyCallable = Callable[[int, int], Awaitable[int]]
+
+async def add(a: int, b: int) -> int:
+    return a + b
+
+async def await_send(send: MyCallable) -> int:
+    return await send(1, 2)
+
+async def await_throw(throw: MyCallable) -> int:
+    return await throw(3, 4)
+
+async def tests() -> None:
+    assert await await_send(add) == 3
+    assert await await_throw(add) == 7
+
+def test_callable_arg_same_name_as_helper() -> None:
+    asyncio.run(tests())
+
 [file asyncio/__init__.pyi]
 def run(x: object) -> object: ...
diff --git a/mypyc/test-data/run-bools.test b/mypyc/test-data/run-bools.test
index a0b8ea31ebc0..b34fedebaa9f 100644
--- a/mypyc/test-data/run-bools.test
+++ b/mypyc/test-data/run-bools.test
@@ -223,7 +223,34 @@ def test_mixed_comparisons_i64() -> None:
             assert gt_mixed_i64(n, x) == (n > int(x))
 
 [case testBoolMixInt]
-y = False
-print((y or 0) and True)
+def test_mix() -> None:
+    y = False
+    print((y or 0) and True)
 [out]
 0
+
+[case testIsInstance]
+from typing import Any
+def test_built_in() -> None:
+    true: Any = True
+    false: Any = False
+    assert isinstance(true, bool)
+    assert isinstance(false, bool)
+
+    assert not isinstance(set(), bool)
+    assert not isinstance((), bool)
+    assert not isinstance((True, False), bool)
+    assert not isinstance({False, True}, bool)
+    assert not isinstance(int() + 1, bool)
+    assert not isinstance(str() + 'False', bool)
+
+def test_user_defined() -> None:
+    from userdefinedbool import bool
+
+    b: Any = True
+    assert isinstance(bool(), bool)
+    assert not isinstance(b, bool)
+
+[file userdefinedbool.py]
+class bool:
+    pass
diff --git a/mypyc/test-data/run-bytes.test b/mypyc/test-data/run-bytes.test
index fa63c46a6798..df5cb209b902 100644
--- a/mypyc/test-data/run-bytes.test
+++ b/mypyc/test-data/run-bytes.test
@@ -277,7 +277,6 @@ class bytes_subclass(bytes):
         return b'spook'
 
 [case testBytesFormatting]
-[typing fixtures/typing-full.pyi]
 from testutil import assertRaises
 
 # https://www.python.org/dev/peps/pep-0461/
@@ -314,6 +313,7 @@ def test_bytes_formatting_2() -> None:
     aa = b'\xe4\xbd\xa0\xe5\xa5\xbd%b' % b'\xe4\xbd\xa0\xe5\xa5\xbd'
     assert aa == b'\xe4\xbd\xa0\xe5\xa5\xbd\xe4\xbd\xa0\xe5\xa5\xbd'
     assert aa.decode() == '你好你好'
+[typing fixtures/typing-full.pyi]
 
 
 class A:
@@ -323,3 +323,81 @@ class A:
 def test_bytes_dunder() -> None:
     assert b'%b' % A() == b'aaa'
     assert b'%s' % A() == b'aaa'
+
+[case testIsInstance]
+from copysubclass import subbytes, subbytearray
+from typing import Any
+def test_bytes() -> None:
+    b: Any = b''
+    assert isinstance(b, bytes)
+    assert isinstance(b + b'123', bytes)
+    assert isinstance(b + b'\xff', bytes)
+    assert isinstance(subbytes(), bytes)
+    assert isinstance(subbytes(b + b'123'), bytes)
+    assert isinstance(subbytes(b + b'\xff'), bytes)
+
+    assert not isinstance(set(), bytes)
+    assert not isinstance((), bytes)
+    assert not isinstance((b'1',b'2',b'3'), bytes)
+    assert not isinstance({b'a',b'b'}, bytes)
+    assert not isinstance(int() + 1, bytes)
+    assert not isinstance(str() + 'a', bytes)
+
+def test_user_defined_bytes() -> None:
+    from userdefinedbytes import bytes
+
+    assert isinstance(bytes(), bytes)
+    assert not isinstance(b'\x7f', bytes)
+
+def test_bytearray() -> None:
+    assert isinstance(bytearray(), bytearray)
+    assert isinstance(bytearray(b'123'), bytearray)
+    assert isinstance(bytearray(b'\xff'), bytearray)
+    assert isinstance(subbytearray(), bytearray)
+    assert isinstance(subbytearray(bytearray(b'123')), bytearray)
+    assert isinstance(subbytearray(bytearray(b'\xff')), bytearray)
+
+    assert not isinstance(set(), bytearray)
+    assert not isinstance((), bytearray)
+    assert not isinstance((bytearray(b'1'),bytearray(b'2'),bytearray(b'3')), bytearray)
+    assert not isinstance([bytearray(b'a'),bytearray(b'b')], bytearray)
+    assert not isinstance(int() + 1, bytearray)
+    assert not isinstance(str() + 'a', bytearray)
+
+[file copysubclass.py]
+class subbytes(bytes):
+    pass
+
+class subbytearray(bytearray):
+    pass
+
+[file userdefinedbytes.py]
+class bytes:
+    pass
+
+[case testBytesOptionalEquality]
+from __future__ import annotations
+
+def eq_b_opt_b(x: bytes | None, y: bytes) -> bool:
+    return x == y
+
+def ne_b_b_opt(x: bytes, y: bytes | None) -> bool:
+    return x != y
+
+def test_optional_eq() -> None:
+    b = b'x'
+    assert eq_b_opt_b(b, b)
+    assert eq_b_opt_b(b + bytes([int()]), b + bytes([int()]))
+
+    assert not eq_b_opt_b(b'x', b'y')
+    assert not eq_b_opt_b(b'y', b'x')
+    assert not eq_b_opt_b(None, b'x')
+
+def test_optional_ne() -> None:
+    b = b'x'
+    assert not ne_b_b_opt(b, b)
+    assert not ne_b_b_opt(b + b'y', b + bytes() + b'y')
+
+    assert ne_b_b_opt(b'x', b'y')
+    assert ne_b_b_opt(b'y', b'x')
+    assert ne_b_b_opt(b'x', None)
diff --git a/mypyc/test-data/run-classes.test b/mypyc/test-data/run-classes.test
index fd486980ef16..b25dc9458fd1 100644
--- a/mypyc/test-data/run-classes.test
+++ b/mypyc/test-data/run-classes.test
@@ -1278,9 +1278,10 @@ class Bar(Foo):
     def f(self, *args: int, **kwargs: int) -> None:
         print("stuff", args, kwargs)
 
-z: Foo = Bar()
-z.f(1, z=50)
-z.f()
+def test_override() -> None:
+    z: Foo = Bar()
+    z.f(1, z=50)
+    z.f()
 
 [out]
 stuff (1,) {'z': 50}
@@ -1300,18 +1301,19 @@ class Foo:
 def baz_f(self: Any, *args: int, **kwargs: int) -> None:
     print("Baz", args, kwargs)
 
-# Make an "interpreted" subtype of Foo
-type2: Any = type
-Bar = type2('Bar', (Foo,), {})
-Baz = type2('Baz', (Foo,), {'f': baz_f})
+def test_override() -> None:
+    # Make an "interpreted" subtype of Foo
+    type2: Any = type
+    Bar = type2('Bar', (Foo,), {})
+    Baz = type2('Baz', (Foo,), {'f': baz_f})
 
-y: Foo = Bar()
-y.f(1, z=2)
-y.f()
+    y: Foo = Bar()
+    y.f(1, z=2)
+    y.f()
 
-z: Foo = Baz()
-z.f(1, z=2)
-z.f()
+    z: Foo = Baz()
+    z.f(1, z=2)
+    z.f()
 
 [out]
 Foo 1 2
@@ -1330,9 +1332,10 @@ class Bar(Foo):
     def f(self, x: Optional[int]=None) -> None:
         print(x)
 
-z: Foo = Bar()
-z.f(1)
-z.f()
+def test_override() -> None:
+    z: Foo = Bar()
+    z.f(1)
+    z.f()
 
 [out]
 1
@@ -1349,10 +1352,11 @@ class Bar(Foo):
     def f(self, *args: int, **kwargs: int) -> None:
         print("Bar", args, kwargs)
 
-z: Foo = Bar()
-z.f(1, z=2)
-z.f(1, 2, 3)
-# z.f(x=5)  # Not tested because we (knowingly) do the wrong thing and pass it as positional
+def test_override() -> None:
+    z: Foo = Bar()
+    z.f(1, z=2)
+    z.f(1, 2, 3)
+    # z.f(x=5)  # Not tested because we (knowingly) do the wrong thing and pass it as positional
 
 [out]
 Bar (1,) {'z': 2}
@@ -1370,10 +1374,11 @@ class Bar(Foo):
     def f(self, x: int = 10, *args: int, **kwargs: int) -> None:
         print("Bar", x, args, kwargs)
 
-z: Foo = Bar()
-z.f(1, z=2)
-z.f(1, 2, 3)
-z.f()
+def test_override() -> None:
+    z: Foo = Bar()
+    z.f(1, z=2)
+    z.f(1, 2, 3)
+    z.f()
 
 [out]
 Bar 1 () {'z': 2}
@@ -1397,18 +1402,19 @@ class Foo:
 def baz_f(self, a: int=30, y: int=50) -> None:
     print("Baz", a, y)
 
-# Make an "interpreted" subtype of Foo
-type2: Any = type
-Baz = type2('Baz', (Foo,), {'f': baz_f})
+def test_override() -> None:
+    # Make an "interpreted" subtype of Foo
+    type2: Any = type
+    Baz = type2('Baz', (Foo,), {'f': baz_f})
 
-z: Foo = Baz()
-z.f()
-z.f(y=1)
-z.f(1, 2)
-# Not tested because we don't (and probably won't) match cpython here
-# from testutil import assertRaises
-# with assertRaises(TypeError):
-#     z.f(x=7)
+    z: Foo = Baz()
+    z.f()
+    z.f(y=1)
+    z.f(1, 2)
+    # Not tested because we don't (and probably won't) match cpython here
+    # from testutil import assertRaises
+    # with assertRaises(TypeError):
+    #     z.f(x=7)
 
 [out]
 Baz 30 50
@@ -2591,7 +2597,8 @@ class Base:
 class Derived(Base):
     pass
 
-assert Derived()() == 1
+def test_inherited() -> None:
+    assert Derived()() == 1
 
 [case testClassWithFinalAttribute]
 from typing import Final
@@ -2703,6 +2710,212 @@ from native import Player
 [out]
 Player.MIN = <Player.MIN: 1>
 
+[case testBufferRoundTrip_native_libs]
+from typing import Final
+from mypy_extensions import u8
+from native_internal import (
+    Buffer, write_bool, read_bool, write_str, read_str, write_float, read_float,
+    write_int, read_int, write_tag, read_tag
+)
+
+Tag = u8
+TAG_A: Final[Tag] = 33
+TAG_B: Final[Tag] = 255
+TAG_SPECIAL: Final[Tag] = 239
+
+def test_buffer_basic() -> None:
+    b = Buffer(b"foo")
+    assert b.getvalue() == b"foo"
+
+def test_buffer_roundtrip() -> None:
+    b = Buffer()
+    write_str(b, "foo")
+    write_bool(b, True)
+    write_str(b, "bar" * 1000)
+    write_bool(b, False)
+    write_float(b, 0.1)
+    write_int(b, 0)
+    write_int(b, 1)
+    write_tag(b, TAG_A)
+    write_tag(b, TAG_SPECIAL)
+    write_tag(b, TAG_B)
+    write_int(b, 2)
+    write_int(b, 2 ** 85)
+    write_int(b, 255)
+    write_int(b, -1)
+    write_int(b, -255)
+    write_int(b, 1234512344)
+    write_int(b, 1234512345)
+
+    b = Buffer(b.getvalue())
+    assert read_str(b) == "foo"
+    assert read_bool(b) is True
+    assert read_str(b) == "bar" * 1000
+    assert read_bool(b) is False
+    assert read_float(b) == 0.1
+    assert read_int(b) == 0
+    assert read_int(b) == 1
+    assert read_tag(b) == TAG_A
+    assert read_tag(b) == TAG_SPECIAL
+    assert read_tag(b) == TAG_B
+    assert read_int(b) == 2
+    assert read_int(b) == 2 ** 85
+    assert read_int(b) == 255
+    assert read_int(b) == -1
+    assert read_int(b) == -255
+    assert read_int(b) == 1234512344
+    assert read_int(b) == 1234512345
+
+def test_buffer_int_size() -> None:
+    for i in (-10, -9, 0, 116, 117):
+        b = Buffer()
+        write_int(b, i)
+        assert len(b.getvalue()) == 1
+        b = Buffer(b.getvalue())
+        assert read_int(b) == i
+    for i in (-12345, -12344, -11, 118, 12344, 12345):
+        b = Buffer()
+        write_int(b, i)
+        assert len(b.getvalue()) <= 9  # sizeof(size_t) + 1
+        b = Buffer(b.getvalue())
+        assert read_int(b) == i
+
+def test_buffer_str_size() -> None:
+    for s in ("", "a", "a" * 127):
+        b = Buffer()
+        write_str(b, s)
+        assert len(b.getvalue()) == len(s) + 1
+        b = Buffer(b.getvalue())
+        assert read_str(b) == s
+
+[file driver.py]
+from native import *
+
+test_buffer_basic()
+test_buffer_roundtrip()
+test_buffer_int_size()
+test_buffer_str_size()
+
+def test_buffer_basic_interpreted() -> None:
+    b = Buffer(b"foo")
+    assert b.getvalue() == b"foo"
+
+def test_buffer_roundtrip_interpreted() -> None:
+    b = Buffer()
+    write_str(b, "foo")
+    write_bool(b, True)
+    write_str(b, "bar" * 1000)
+    write_bool(b, False)
+    write_float(b, 0.1)
+    write_int(b, 0)
+    write_int(b, 1)
+    write_tag(b, 33)
+    write_tag(b, 239)
+    write_tag(b, 255)
+    write_int(b, 2)
+    write_int(b, 2 ** 85)
+    write_int(b, 255)
+    write_int(b, -1)
+    write_int(b, -255)
+    write_int(b, 1234512344)
+    write_int(b, 1234512345)
+
+    b = Buffer(b.getvalue())
+    assert read_str(b) == "foo"
+    assert read_bool(b) is True
+    assert read_str(b) == "bar" * 1000
+    assert read_bool(b) is False
+    assert read_float(b) == 0.1
+    assert read_int(b) == 0
+    assert read_int(b) == 1
+    assert read_tag(b) == 33
+    assert read_tag(b) == 239
+    assert read_tag(b) == 255
+    assert read_int(b) == 2
+    assert read_int(b) == 2 ** 85
+    assert read_int(b) == 255
+    assert read_int(b) == -1
+    assert read_int(b) == -255
+    assert read_int(b) == 1234512344
+    assert read_int(b) == 1234512345
+
+def test_buffer_int_size_interpreted() -> None:
+    for i in (-10, -9, 0, 116, 117):
+        b = Buffer()
+        write_int(b, i)
+        assert len(b.getvalue()) == 1
+        b = Buffer(b.getvalue())
+        assert read_int(b) == i
+    for i in (-12345, -12344, -11, 118, 12344, 12345):
+        b = Buffer()
+        write_int(b, i)
+        assert len(b.getvalue()) <= 9  # sizeof(size_t) + 1
+        b = Buffer(b.getvalue())
+        assert read_int(b) == i
+
+def test_buffer_str_size_interpreted() -> None:
+    for s in ("", "a", "a" * 127):
+        b = Buffer()
+        write_str(b, s)
+        assert len(b.getvalue()) == len(s) + 1
+        b = Buffer(b.getvalue())
+        assert read_str(b) == s
+
+test_buffer_basic_interpreted()
+test_buffer_roundtrip_interpreted()
+test_buffer_int_size_interpreted()
+test_buffer_str_size_interpreted()
+
+[case testEnumMethodCalls]
+from enum import Enum
+from typing import overload, Optional, Union
+
+class C:
+    def foo(self, x: Test) -> bool:
+        assert Test.ONE.is_one()
+        assert x.next(2) == Test.THREE
+        assert x.prev(2) == Test.ONE
+        assert x.enigma(22)
+        assert x.enigma("22") == 22
+        return x.is_one(inverse=True)
+
+class Test(Enum):
+    ONE = 1
+    TWO = 2
+    THREE = 3
+
+    def is_one(self, *, inverse: bool = False) -> bool:
+        if inverse:
+            return self != Test.ONE
+        return self == Test.ONE
+
+    @classmethod
+    def next(cls, val: int) -> Test:
+        return cls(val + 1)
+
+    @staticmethod
+    def prev(val: int) -> Test:
+        return Test(val - 1)
+
+    @overload
+    def enigma(self, val: int) -> bool: ...
+    @overload
+    def enigma(self, val: Optional[str] = None) -> int: ...
+    def enigma(self, val: Union[int, str, None] = None) -> Union[int, bool]:
+        if isinstance(val, int):
+            return self.is_one()
+        return 22
+[file driver.py]
+from native import Test, C
+
+assert Test.ONE.is_one()
+assert Test.TWO.is_one(inverse=True)
+assert not C().foo(Test.ONE)
+assert Test.next(2) == Test.THREE
+assert Test.prev(2) == Test.ONE
+assert Test.ONE.enigma(22)
+assert Test.ONE.enigma("22") == 22
+
 [case testStaticCallsWithUnpackingArgs]
 from typing import Tuple
 
@@ -3058,3 +3271,526 @@ f(C(1, "yes"))
 [out]
 B 1
 C yes
+
+[case testTypeObjectName]
+from typing import Any
+import re
+
+from dynamic import E, foo, Thing
+
+class C: pass
+class D(C): pass
+
+def type_name(t: type[object]) -> str:
+    return t.__name__
+
+def any_name(x: Any) -> str:
+    return x.__name__
+
+def assert_type_name(x: Any) -> None:
+    assert type_name(x) == getattr(x, "__name__")
+    assert any_name(x) == getattr(x, "__name__")
+
+def assert_any_name(x: Any) -> None:
+    assert any_name(x) == getattr(x, "__name__")
+
+def test_type_name() -> None:
+    assert_type_name(C)
+    assert_type_name(D)
+    assert_type_name(int)
+    assert_type_name(E)
+    assert_type_name(re.Pattern)
+
+def test_module_name() -> None:
+    assert_any_name(re)
+
+def test_function_name() -> None:
+    assert_any_name(any_name)
+    assert_any_name(foo)
+
+def test_obj_name() -> None:
+    assert_any_name(Thing())
+
+[file dynamic.py]
+class E: pass
+
+def foo(): pass
+
+class Thing:
+    def __init__(self):
+        self.__name__ = "xyz"
+
+[case testTypeOfObject]
+from typing import Any
+
+from dynamic import Dyn
+
+class Foo: pass
+class Bar(Foo): pass
+
+def generic_type(x) -> type[object]:
+    return x.__class__
+
+def test_built_in_type() -> None:
+    i: Any = int
+    l: Any = list
+    assert type(i()) is i().__class__
+    assert type(i()) is int
+    assert type(l()) is list
+    n = 5
+    assert n.__class__ is i
+
+def test_native_class() -> None:
+    f_any: Any = Foo()
+    b_any: Any = Bar()
+    f: Foo = f_any
+    b: Foo = b_any
+    if int("1"):  # use int("1") to avoid constant folding
+        assert type(f) is Foo
+        assert type(b) is Bar
+    if int("2"):
+        assert f.__class__ is Foo
+        assert b.__class__ is Bar
+    if int("3"):
+        assert f_any.__class__ is Foo
+        assert b_any.__class__ is Bar
+    if int("4"):
+        assert type(f_any) is Foo
+        assert type(b_any) is Bar
+
+def test_python_class() -> None:
+    d = Dyn()
+    assert type(d) is Dyn
+    assert d.__class__ is Dyn
+
+[file dynamic.py]
+class Dyn: pass
+
+[case testDunderNew]
+from __future__ import annotations
+from typing import Any, Union
+
+from testutil import assertRaises
+
+class Add:
+    l: IntLike
+    r: IntLike
+
+    def __new__(cls, l: IntLike, r: IntLike) -> Any:
+        return (
+            l if r == 0 else
+            r if l == 0 else
+            super().__new__(cls)
+        )
+
+    def __init__(self, l: IntLike, r: IntLike):
+        self.l = l
+        self.r = r
+
+IntLike = Union[int, Add]
+
+class RaisesException:
+    def __new__(cls, val: int) -> RaisesException:
+        if val == 0:
+            raise RuntimeError("Invalid value!")
+        return super().__new__(cls)
+
+    def __init__(self, val: int) -> None:
+        self.val = val
+
+class ClsArgNotPassed:
+    def __new__(cls) -> Any:
+        return super().__new__(str)
+
+def test_dunder_new() -> None:
+    add_instance: Any = Add(1, 5)
+    assert type(add_instance) == Add
+    assert add_instance.l == 1
+    assert add_instance.r == 5
+
+    # TODO: explicit types should not be needed but mypy does not use
+    # the return type of __new__ which makes mypyc add casts to Add.
+    right_int: Any = Add(0, 5)
+    assert type(right_int) == int
+    assert right_int == 5
+
+    left_int: Any = Add(1, 0)
+    assert type(left_int) == int
+    assert left_int == 1
+
+    with assertRaises(RuntimeError, "Invalid value!"):
+        raised = RaisesException(0)
+
+    not_raised = RaisesException(1)
+    assert not_raised.val == 1
+
+    with assertRaises(TypeError, "object.__new__(str) is not safe, use str.__new__()"):
+        str_as_cls = ClsArgNotPassed()
+
+
+[case testDunderNewInInterpreted]
+from __future__ import annotations
+from typing import Any, Union
+
+class Add:
+    l: IntLike
+    r: IntLike
+
+    def __new__(cls, l: IntLike, r: IntLike) -> Any:
+        print(f'running __new__ with {l} and {r}')
+
+        return (
+            l if r == 0 else
+            r if l == 0 else
+            super().__new__(cls)
+        )
+
+    def __init__(self, l: IntLike, r: IntLike):
+        self.l = l
+        self.r = r
+
+    def __repr__(self) -> str:
+        return f'({self.l} + {self.r})'
+
+IntLike = Union[int, Add]
+
+class RaisesException:
+    def __new__(cls, val: int) -> RaisesException:
+        if val == 0:
+            raise RuntimeError("Invalid value!")
+        return super().__new__(cls)
+
+    def __init__(self, val: int) -> None:
+        self.val = val
+
+class ClsArgNotPassed:
+    def __new__(cls) -> Any:
+        return super().__new__(str)
+
+[file driver.py]
+from native import Add, ClsArgNotPassed, RaisesException
+
+from testutil import assertRaises
+
+print(f'{Add(1, 5)=}')
+print(f'{Add(0, 5)=}')
+print(f'{Add(1, 0)=}')
+
+with assertRaises(RuntimeError, "Invalid value!"):
+    raised = RaisesException(0)
+
+not_raised = RaisesException(1)
+assert not_raised.val == 1
+
+with assertRaises(TypeError, "object.__new__(str) is not safe, use str.__new__()"):
+    str_as_cls = ClsArgNotPassed()
+
+[out]
+running __new__ with 1 and 5
+Add(1, 5)=(1 + 5)
+running __new__ with 0 and 5
+Add(0, 5)=5
+running __new__ with 1 and 0
+Add(1, 0)=1
+
+[case testInheritedDunderNew]
+from __future__ import annotations
+from mypy_extensions import mypyc_attr
+from typing_extensions import Self
+
+from m import interpreted_subclass
+
+@mypyc_attr(allow_interpreted_subclasses=True)
+class Base:
+    val: int
+
+    def __new__(cls, val: int) -> Self:
+        obj = super().__new__(cls)
+        obj.val = val + 1
+        return obj
+
+    def __init__(self, val: int) -> None:
+        self.init_val = val
+
+class Sub(Base):
+    def __new__(cls, val: int) -> Self:
+        return super().__new__(cls, val + 1)
+
+    def __init__(self, val: int) -> None:
+        super().__init__(val)
+        self.init_val = self.init_val * 2
+
+class SubWithoutNew(Base):
+    def __init__(self, val: int) -> None:
+        super().__init__(val)
+        self.init_val = self.init_val * 2
+
+class BaseWithoutInterpretedSubclasses:
+    val: int
+
+    def __new__(cls, val: int) -> Self:
+        obj = super().__new__(cls)
+        obj.val = val + 1
+        return obj
+
+    def __init__(self, val: int) -> None:
+        self.init_val = val
+
+class SubNoInterpreted(BaseWithoutInterpretedSubclasses):
+    def __new__(cls, val: int) -> Self:
+        return super().__new__(cls, val + 1)
+
+    def __init__(self, val: int) -> None:
+        super().__init__(val)
+        self.init_val = self.init_val * 2
+
+class SubNoInterpretedWithoutNew(BaseWithoutInterpretedSubclasses):
+    def __init__(self, val: int) -> None:
+        super().__init__(val)
+        self.init_val = self.init_val * 2
+
+def test_inherited_dunder_new() -> None:
+    b = Base(42)
+    assert type(b) == Base
+    assert b.val == 43
+    assert b.init_val == 42
+
+    s = Sub(42)
+    assert type(s) == Sub
+    assert s.val == 44
+    assert s.init_val == 84
+
+    s2 = SubWithoutNew(42)
+    assert type(s2) == SubWithoutNew
+    assert s2.val == 43
+    assert s2.init_val == 84
+
+def test_inherited_dunder_new_without_interpreted_subclasses() -> None:
+    b = BaseWithoutInterpretedSubclasses(42)
+    assert type(b) == BaseWithoutInterpretedSubclasses
+    assert b.val == 43
+    assert b.init_val == 42
+
+    s = SubNoInterpreted(42)
+    assert type(s) == SubNoInterpreted
+    assert s.val == 44
+    assert s.init_val == 84
+
+    s2 = SubNoInterpretedWithoutNew(42)
+    assert type(s2) == SubNoInterpretedWithoutNew
+    assert s2.val == 43
+    assert s2.init_val == 84
+
+def test_interpreted_subclass() -> None:
+    interpreted_subclass(Base)
+
+[file m.py]
+from __future__ import annotations
+from typing_extensions import Self
+
+def interpreted_subclass(base) -> None:
+    b = base(42)
+    assert type(b) == base
+    assert b.val == 43
+    assert b.init_val == 42
+
+    class InterpretedSub(base):
+        def __new__(cls, val: int) -> Self:
+            return super().__new__(cls, val + 1)
+
+        def __init__(self, val: int) -> None:
+            super().__init__(val)
+            self.init_val : int = self.init_val * 2
+
+    s = InterpretedSub(42)
+    assert type(s) == InterpretedSub
+    assert s.val == 44
+    assert s.init_val == 84
+
+    class InterpretedSubWithoutNew(base):
+        def __init__(self, val: int) -> None:
+            super().__init__(val)
+            self.init_val : int = self.init_val * 2
+
+    s2 = InterpretedSubWithoutNew(42)
+    assert type(s2) == InterpretedSubWithoutNew
+    assert s2.val == 43
+    assert s2.init_val == 84
+
+[typing fixtures/typing-full.pyi]
+
+[case testDunderNewInitArgMismatch]
+from __future__ import annotations
+from testutil import assertRaises
+
+class Test0:
+    @classmethod
+    def __new__(cls, val: int = 42) -> Test0:
+        obj = super().__new__(cls)
+        obj.val = val
+        return obj
+
+    def __init__(self) -> None:
+        self.val = 0
+
+class Test1:
+    def __new__(cls, val: int) -> Test1:
+        obj = super().__new__(cls)
+        obj.val = val
+        return obj
+
+    def __init__(self) -> None:
+        self.val = 0
+
+class Test2:
+    def __new__(cls) -> Test2:
+        obj = super().__new__(cls)
+        return obj
+
+    def __init__(self, val: int) -> None:
+        self.val = val
+
+def test_arg_mismatch() -> None:
+    t0 = Test0()
+    assert t0.val == 0
+    t0 = Test0.__new__(1)
+    assert t0.val == 1
+    with assertRaises(TypeError, "__new__() missing required argument 'val'"):
+        t1 = Test1()
+    t1 = Test1.__new__(Test1, 2)
+    assert t1.val == 2
+    with assertRaises(TypeError, "__new__() takes at most 0 arguments"):
+        t2 = Test2(42)
+    t2 = Test2.__new__(Test2)
+    with assertRaises(AttributeError, "attribute 'val' of 'Test2' undefined"):
+        print(t2.val)
+
+[case testDunderNewInitArgMismatchInInterpreted]
+from __future__ import annotations
+
+class Test0:
+    # TODO: It should be possible to annotate '@classmethod' here
+    # but when it's added calling __new__ in interpreted code
+    # without the explicit type param results in a TypeError.
+    def __new__(cls, val: int = 42) -> Test0:
+        obj = super().__new__(cls)
+        obj.val = val
+        return obj
+
+    def __init__(self) -> None:
+        self.val = 0
+
+class Test1:
+    def __new__(cls, val: int) -> Test1:
+        obj = super().__new__(cls)
+        obj.val = val
+        return obj
+
+    def __init__(self) -> None:
+        self.val = 0
+
+class Test2:
+    def __new__(cls) -> Test2:
+        obj = super().__new__(cls)
+        return obj
+
+    def __init__(self, val: int) -> None:
+        self.val = val
+
+[file driver.py]
+from native import Test0, Test1, Test2
+from testutil import assertRaises
+
+t0 = Test0()
+assert t0.val == 0
+t0 = Test0.__new__(Test0, 1)
+assert t0.val == 1
+with assertRaises(TypeError, "__new__() missing required argument 'val'"):
+    t1 = Test1()
+t1 = Test1.__new__(Test1, 2)
+assert t1.val == 2
+with assertRaises(TypeError, "__new__() takes at most 0 arguments"):
+    t2 = Test2(42)
+t2 = Test2.__new__(Test2)
+with assertRaises(AttributeError, "attribute 'val' of 'Test2' undefined"):
+    print(t2.val)
+
+[case testDunderNewAttributeAccess]
+from __future__ import annotations
+
+from mypy_extensions import u8
+from testutil import assertRaises
+
+class Test:
+    native: int
+    generic: object
+    bitfield: u8
+    default: int = 5
+
+    def __new__(cls, native: int, generic: object, bitfield: u8) -> Test:
+        obj = super().__new__(cls)
+
+        with assertRaises(AttributeError, "attribute 'native' of 'Test' undefined"):
+            print(obj.native)
+        with assertRaises(AttributeError, "attribute 'generic' of 'Test' undefined"):
+            print(obj.generic)
+        with assertRaises(AttributeError, "attribute 'bitfield' of 'Test' undefined"):
+            print(obj.bitfield)
+
+        obj.native = native
+        obj.generic = generic
+        obj.bitfield = bitfield
+
+        obj.native = obj.native + 1
+        obj.generic = obj.generic.__str__()
+        obj.bitfield = obj.bitfield & 0x0F
+        obj.default = obj.default * 2
+        return obj
+
+def test_attribute_access() -> None:
+    t = Test(42, {}, 0xCC)
+    assert t.native == 43
+    assert t.generic == "{}"
+    assert t.bitfield == 0x0C
+    assert t.default == 10
+
+[case testDunderNewAttributeAccessInInterpreted]
+from __future__ import annotations
+
+from mypy_extensions import u8
+from testutil import assertRaises
+
+class Test:
+    native: int
+    generic: object
+    bitfield: u8
+    default: int = 5
+
+    def __new__(cls, native: int, generic: object, bitfield: u8) -> Test:
+        obj = super().__new__(cls)
+
+        with assertRaises(AttributeError, "attribute 'native' of 'Test' undefined"):
+            print(obj.native)
+        with assertRaises(AttributeError, "attribute 'generic' of 'Test' undefined"):
+            print(obj.generic)
+        with assertRaises(AttributeError, "attribute 'bitfield' of 'Test' undefined"):
+            print(obj.bitfield)
+
+        obj.native = native
+        obj.generic = generic
+        obj.bitfield = bitfield
+
+        obj.native = obj.native + 1
+        obj.generic = obj.generic.__str__()
+        obj.bitfield = obj.bitfield & 0x0F
+        obj.default = obj.default * 2
+        return obj
+
+[file driver.py]
+from native import Test
+
+t = Test(42, {}, 0xCC)
+assert t.native == 43
+assert t.generic == "{}"
+assert t.bitfield == 0x0C
+assert t.default == 10
diff --git a/mypyc/test-data/run-dicts.test b/mypyc/test-data/run-dicts.test
index 2a3be188ad00..2b75b32c906e 100644
--- a/mypyc/test-data/run-dicts.test
+++ b/mypyc/test-data/run-dicts.test
@@ -336,3 +336,35 @@ def test_dict_to_bool() -> None:
     for x in tmp_list:
         assert is_true(x)
         assert not is_false(x)
+
+[case testIsInstance]
+from copysubclass import subc
+def test_built_in() -> None:
+    assert isinstance({}, dict)
+    assert isinstance({'one': 1, 'two': 2}, dict)
+    assert isinstance({1: 1, 'two': 2}, dict)
+    assert isinstance(subc(), dict)
+    assert isinstance(subc({'a': 1, 'b': 2}), dict)
+    assert isinstance(subc({1: 'a', 2: 'b'}), dict)
+
+    assert not isinstance(set(), dict)
+    assert not isinstance((), dict)
+    assert not isinstance((1,2,3), dict)
+    assert not isinstance({'a','b'}, dict)
+    assert not isinstance(int() + 1, dict)
+    assert not isinstance(str() + 'a', dict)
+
+def test_user_defined() -> None:
+    from userdefineddict import dict
+
+    assert isinstance(dict(), dict)
+    assert not isinstance({1: dict()}, dict)
+
+[file copysubclass.py]
+from typing import Any
+class subc(dict[Any, Any]):
+    pass
+
+[file userdefineddict.py]
+class dict:
+    pass
diff --git a/mypyc/test-data/run-dunders-special.test b/mypyc/test-data/run-dunders-special.test
index 30c618374f88..4817435b1e7c 100644
--- a/mypyc/test-data/run-dunders-special.test
+++ b/mypyc/test-data/run-dunders-special.test
@@ -6,4 +6,7 @@ class UsesNotImplemented:
     def __eq__(self, b: object) -> bool:
         return NotImplemented
 
-assert UsesNotImplemented() != object()
+def test_not_implemented() -> None:
+    assert UsesNotImplemented() != object()
+    x = UsesNotImplemented() == object()
+    assert not x
diff --git a/mypyc/test-data/run-dunders.test b/mypyc/test-data/run-dunders.test
index b8fb13c9dcec..ec992afbfbd1 100644
--- a/mypyc/test-data/run-dunders.test
+++ b/mypyc/test-data/run-dunders.test
@@ -965,3 +965,25 @@ def test_final() -> None:
     assert b + 3 == 9
     assert (a < A(5)) is False
     assert (b < A(5)) is True
+
+[case testDundersEq]
+class Eq:
+    def __init__(self, x: int) -> None:
+        self.x = x
+
+    def __eq__(self, other: object) -> bool:
+        if not isinstance(other, Eq):
+            return NotImplemented
+        return self.x == other.x
+
+def eq(x: Eq, y: Eq) -> bool:
+    return x == y
+
+def ne(x: Eq, y: Eq) -> bool:
+    return x != y
+
+def test_equality_with_implicit_ne() -> None:
+    assert eq(Eq(1), Eq(1))
+    assert not eq(Eq(1), Eq(2))
+    assert ne(Eq(1), Eq(2))
+    assert not ne(Eq(1), Eq(1))
diff --git a/mypyc/test-data/run-floats.test b/mypyc/test-data/run-floats.test
index 49620f6448c7..424d52cdb0d5 100644
--- a/mypyc/test-data/run-floats.test
+++ b/mypyc/test-data/run-floats.test
@@ -512,3 +512,34 @@ def test_implement_trait_attribute() -> None:
     a.y = 8.0
     assert a.x == 7
     assert a.y == 8
+
+[case testIsInstance]
+from copysubclass import subc
+from testutil import float_vals
+from typing import Any
+def test_built_in() -> None:
+    for f in float_vals:
+        assert isinstance(float(0) + f, float)
+        assert isinstance(subc(f), float)
+
+    assert not isinstance(set(), float)
+    assert not isinstance((), float)
+    assert not isinstance((1.0, 2.0), float)
+    assert not isinstance({3.14}, float)
+    assert not isinstance(int() + 1, float)
+    assert not isinstance(str() + '4.2', float)
+
+def test_user_defined() -> None:
+    from userdefinedfloat import float
+
+    f: Any = 3.14
+    assert isinstance(float(), float)
+    assert not isinstance(f, float)
+
+[file copysubclass.py]
+class subc(float):
+    pass
+
+[file userdefinedfloat.py]
+class float:
+    pass
diff --git a/mypyc/test-data/run-functions.test b/mypyc/test-data/run-functions.test
index 46f343fa3798..9bc5bb05c8d6 100644
--- a/mypyc/test-data/run-functions.test
+++ b/mypyc/test-data/run-functions.test
@@ -1235,13 +1235,11 @@ from contextlib import contextmanager
 def f() -> Iterator[None]:
     yield
 
-def g() -> None:
+def test_special_case() -> None:
     a = ['']
     with f():
         a.pop()
 
-g()
-
 [case testUnpackKwargsCompiled]
 from typing import TypedDict
 from typing_extensions import Unpack
@@ -1253,8 +1251,9 @@ class Person(TypedDict):
 def foo(**kwargs: Unpack[Person]) -> None:
     print(kwargs["name"])
 
-# This is not really supported yet, just test that we behave reasonably.
-foo(name='Jennifer', age=38)
+def test_unpack() -> None:
+    # This is not really supported yet, just test that we behave reasonably.
+    foo(name='Jennifer', age=38)
 [typing fixtures/typing-full.pyi]
 [out]
 Jennifer
@@ -1269,8 +1268,9 @@ def foo() -> None:
     print(inner.__dict__)  # type: ignore[attr-defined]
     print(inner.x)  # type: ignore[attr-defined]
 
-if sys.version_info >= (3, 12):  # type: ignore
-    foo()
+def test_nested() -> None:
+    if sys.version_info >= (3, 12):  # type: ignore
+        foo()
 [out]
 [out version>=3.12]
 {}
@@ -1285,7 +1285,8 @@ def bar() -> None:
     functools.update_wrapper(inner, bar)  # type: ignore
     print(inner.__dict__)  # type: ignore
 
-bar()
+def test_update() -> None:
+    bar()
 [typing fixtures/typing-full.pyi]
 [out]
 {'__module__': 'native', '__name__': 'bar', '__qualname__': 'bar', '__doc__': None, '__wrapped__': <built-in function bar>}
@@ -1311,3 +1312,29 @@ from native import f
 print(f(1))
 [out]
 2
+
+[case testStarArgFastPaths]
+from typing import Any, Mapping
+def fn(x: str, y: int) -> str:
+    return x * y
+def star_tuple(*args: Any) -> str:
+    return fn(*args)
+def star_list(args: list[Any]) -> str:
+    return fn(*args)
+def star_generic(args: dict[Any, Any]) -> str:
+    return fn(*args)
+def star2(**kwargs: Any) -> str:
+    return fn(**kwargs)
+def star2_generic(kwargs: Mapping[Any, Any]) -> str:
+    return fn(**kwargs)
+
+def test_star_fastpath_tuple() -> None:
+    assert star_tuple("a", 3) == "aaa"
+def test_star_fastpath_list() -> None:
+    assert star_list(["a", 3]) == "aaa"
+def test_star_fastpath_generic() -> None:
+    assert star_generic({"a": None, 3: None}) == "aaa"
+def test_star2_fastpath() -> None:
+    assert star2(x="a", y=3) == "aaa"
+def test_star2_fastpath_generic() -> None:
+    assert star2_generic({"x": "a", "y": 3}) == "aaa"
diff --git a/mypyc/test-data/run-generators.test b/mypyc/test-data/run-generators.test
index 2e55ded76f74..bfbd5b83696b 100644
--- a/mypyc/test-data/run-generators.test
+++ b/mypyc/test-data/run-generators.test
@@ -190,7 +190,9 @@ exit! a exception!
 ((1,), 'exception!')
 
 [case testYieldNested]
-from typing import Callable, Generator
+from typing import Callable, Generator, Iterator, TypeVar, overload
+
+from testutil import run_generator
 
 def normal(a: int, b: float) -> Callable:
     def generator(x: int, y: str) -> Generator:
@@ -235,15 +237,52 @@ def outer() -> Generator:
             yield i
     return recursive(10)
 
-[file driver.py]
-from native import normal, generator, triple, another_triple, outer
-from testutil import run_generator
+def test_return_nested_generator() -> None:
+    assert run_generator(normal(1, 2.0)(3, '4.00')) == ((1, 2.0, 3, '4.00'), None)
+    assert run_generator(generator(1)) == ((1, 2, 3), None)
+    assert run_generator(triple()()) == ((1, 2, 3), None)
+    assert run_generator(another_triple()()) == ((1,), None)
+    assert run_generator(outer()) == ((0, 1, 2, 3, 4), None)
+
+def call_nested(x: int) -> list[int]:
+    def generator() -> Iterator[int]:
+        n = int() + 2
+        yield x
+        yield n * x
+
+    a = []
+    for x in generator():
+        a.append(x)
+    return a
+
+T = TypeVar("T")
+
+def deco(f: T) -> T:
+    return f
+
+def call_nested_decorated(x: int) -> list[int]:
+    @deco
+    def generator() -> Iterator[int]:
+        n = int() + 3
+        yield x
+        yield n * x
+
+    a = []
+    for x in generator():
+        a.append(x)
+    return a
+
+def call_nested_recursive(x: int) -> Iterator:
+    def recursive(x: int) -> Iterator:
+        if x > 0:
+            yield from recursive(x - 1)
+        yield x
+
+    yield from recursive(x)
 
-assert run_generator(normal(1, 2.0)(3, '4.00')) == ((1, 2.0, 3, '4.00'), None)
-assert run_generator(generator(1)) == ((1, 2, 3), None)
-assert run_generator(triple()()) == ((1, 2, 3), None)
-assert run_generator(another_triple()()) == ((1,), None)
-assert run_generator(outer()) == ((0, 1, 2, 3, 4), None)
+def test_call_nested_generator_in_function() -> None:
+    assert call_nested_decorated(5) == [5, 15]
+    assert list(call_nested_recursive(5)) == [0, 1, 2, 3, 4, 5]
 
 [case testYieldThrow]
 from typing import Generator, Iterable, Any, Union
@@ -587,16 +626,22 @@ else:
 from typing import Iterator
 
 class Foo:
-    flag: bool
+    flag = False
 
 class C:
-    foo: Foo
+    foo = Foo()
 
     def genf(self) -> Iterator[None]:
         self.foo.flag = True
         yield
         self.foo.flag = False
 
+def test_near_yield() -> None:
+    c = C()
+    for x in c.genf():
+        pass
+    assert c.foo.flag == False
+
 [case testGeneratorEarlyReturnWithBorrows]
 from typing import Iterator
 class Bar:
@@ -609,6 +654,12 @@ class Foo:
             return
         yield 0
 
+def test_early_return() -> None:
+    foo = Foo()
+    for x in foo.f():
+        pass
+    assert foo.bar.bar == 1
+
 [case testBorrowingInGeneratorInTupleAssignment]
 from typing import Iterator
 
@@ -681,7 +732,6 @@ def test_basic() -> None:
         assert context.x == 1
     assert context.x == 0
 
-
 [case testYieldSpill]
 from typing import Generator
 from testutil import run_generator
@@ -697,3 +747,163 @@ def test_basic() -> None:
     yields, val = x
     assert yields == ('foo',)
     assert val == 3, val
+
+[case testGeneratorReuse]
+from typing import Iterator, Any
+
+def gen(x: list[int]) -> Iterator[list[int]]:
+    y = [9]
+    for z in x:
+        yield y + [z]
+    yield y
+
+def gen_range(n: int) -> Iterator[int]:
+    for x in range(n):
+        yield x
+
+def test_use_generator_multiple_times_one_at_a_time() -> None:
+    for i in range(100):
+        a = []
+        for x in gen([2, i]):
+            a.append(x)
+        assert a == [[9, 2], [9, i], [9]]
+
+def test_use_multiple_generator_instances_at_same_time() -> None:
+    a = []
+    for x in gen([2]):
+        a.append(x)
+        for y in gen([3, 4]):
+            a.append(y)
+    assert a == [[9, 2], [9, 3], [9, 4], [9], [9], [9, 3], [9, 4], [9]]
+
+def test_use_multiple_generator_instances_at_same_time_2() -> None:
+    a = []
+    for x in gen_range(2):
+        a.append(x)
+        b = []
+        for y in gen_range(3):
+            b.append(y)
+            c = []
+            for z in gen_range(4):
+                c.append(z)
+            assert c == [0, 1, 2, 3]
+        assert b == [0, 1, 2]
+    assert a == [0, 1]
+    assert list(gen_range(5)) == list(range(5))
+
+def gen_a(x: int) -> Iterator[int]:
+    yield x + 1
+
+def gen_b(x: int) -> Iterator[int]:
+    yield x + 2
+
+def test_generator_identities() -> None:
+    # Sanity check: two distinct live objects can't reuse the same memory location
+    g1 = gen_a(1)
+    g2 = gen_a(1)
+    assert g1 is not g2
+
+    # If two generators have non-overlapping lifetimes, they should reuse a memory location
+    g3 = gen_b(1)
+    id1 = id(g3)
+    g3 = gen_b(1)
+    assert id(g3) == id1
+
+    # More complex case of reuse: allocate other objects in between
+    g4: Any = gen_a(1)
+    id2 = id(g4)
+    g4 = gen_b(1)
+    g4 = [gen_b(n) for n in range(100)]
+    g4 = gen_a(1)
+    assert id(g4) == id2
+
+[case testGeneratorReuseWithGilDisabled]
+import sys
+import threading
+from typing import Iterator
+
+def gen() -> Iterator[int]:
+    yield 1
+
+def is_gil_disabled() -> bool:
+    return hasattr(sys, "_is_gil_enabled") and not sys._is_gil_enabled()
+
+def test_each_thread_gets_separate_instance() -> None:
+    if not is_gil_disabled():
+        # This only makes sense if GIL is disabled
+        return
+
+    g = gen()
+    id1 = id(g)
+
+    id2 = 0
+
+    def run() -> None:
+        nonlocal id2
+        g = gen()
+        id2 = id(g)
+
+    t = threading.Thread(target=run)
+    t.start()
+    t.join()
+
+    # Each thread should get a separate reused instance
+    assert id1 != id2
+
+[case testGeneratorWithUndefinedLocalInEnvironment]
+from typing import Iterator
+
+from testutil import assertRaises
+
+def gen(set: bool) -> Iterator[float]:
+    if set:
+        y = float("-113.0")
+    yield 1.0
+    yield y
+
+def test_bitmap_is_cleared_when_object_is_reused() -> None:
+    # This updates the bitmap of the shared instance.
+    list(gen(True))
+
+    # Ensure bitmap has been cleared.
+    with assertRaises(AttributeError):  # TODO: Should be UnboundLocalError
+      list(gen(False))
+
+def gen2(set: bool) -> Iterator[int]:
+    if set:
+        y = int("5")
+    yield 1
+    yield y
+
+def test_undefined_int_in_environment() -> None:
+    list(gen2(True))
+
+    with assertRaises(AttributeError):  # TODO: Should be UnboundLocalError
+      list(gen2(False))
+
+[case testVariableWithSameNameAsHelperMethod]
+from testutil import assertRaises
+from typing import Iterator
+
+def gen_send() -> Iterator[int]:
+    send = 1
+    yield send + 1
+
+def gen_throw() -> Iterator[int]:
+    throw = 42
+    yield throw * 2
+
+def undefined() -> Iterator[int]:
+    if int():
+        send = 1
+    yield send + 1
+
+def test_same_names() -> None:
+    assert list(gen_send()) == [2]
+    assert list(gen_throw()) == [84]
+
+    with assertRaises(AttributeError, "attribute 'send' of 'undefined_gen' undefined"):
+        # TODO: Should be UnboundLocalError, this test verifies that the attribute name
+        # matches the variable name in the input code, since internally it's generated
+        # with a prefix.
+        list(undefined())
diff --git a/mypyc/test-data/run-generics.test b/mypyc/test-data/run-generics.test
index bc78a3b8ab86..55e5adbbb4f9 100644
--- a/mypyc/test-data/run-generics.test
+++ b/mypyc/test-data/run-generics.test
@@ -27,22 +27,23 @@ def fn_typeddict(t: T) -> None:
     print([x for x in t.keys()])
     print({k: v for k, v in t.items()})
 
-fn_mapping({})
-print("=====")
-fn_mapping({"a": 1, "b": 2})
-print("=====")
+def test_mapping() -> None:
+    fn_mapping({})
+    print("=====")
+    fn_mapping({"a": 1, "b": 2})
+    print("=====")
 
-fn_union({"a": 1, "b": 2})
-print("=====")
-fn_union({"a": "1", "b": "2"})
-print("=====")
+    fn_union({"a": 1, "b": 2})
+    print("=====")
+    fn_union({"a": "1", "b": "2"})
+    print("=====")
 
-orig: Union[Dict[str, int], Dict[str, str]] = {"a": 1, "b": 2}
-fn_union(orig)
-print("=====")
+    orig: Union[Dict[str, int], Dict[str, str]] = {"a": 1, "b": 2}
+    fn_union(orig)
+    print("=====")
 
-td: TD = {"foo": 1}
-fn_typeddict(td)
+    td: TD = {"foo": 1}
+    fn_typeddict(td)
 [typing fixtures/typing-full.pyi]
 [out]
 \[]
@@ -96,8 +97,9 @@ def deco(func: Callable[P, int]) -> Callable[P, int]:
 def f(x: int, y: str) -> int:
     return x
 
-assert f(1, 'a') == 1
-assert f(2, y='b') == 2
+def test_usable() -> None:
+    assert f(1, 'a') == 1
+    assert f(2, y='b') == 2
 [out]
 \[1, 'a']
 {}
diff --git a/mypyc/test-data/run-imports.test b/mypyc/test-data/run-imports.test
index c5839d57820e..ce83a882e2de 100644
--- a/mypyc/test-data/run-imports.test
+++ b/mypyc/test-data/run-imports.test
@@ -212,9 +212,10 @@ import shared
 def do_import() -> None:
     import a
 
-assert shared.counter == 0
-do_import()
-assert shared.counter == 1
+def test_lazy() -> None:
+    assert shared.counter == 0
+    do_import()
+    assert shared.counter == 1
 
 [file a.py]
 import shared
@@ -224,9 +225,10 @@ shared.counter += 1
 counter = 0
 
 [case testDelayedImport]
-import a
-print("inbetween")
-import b
+def test_delayed() -> None:
+    import a
+    print("inbetween")
+    import b
 
 [file a.py]
 print("first")
@@ -240,19 +242,21 @@ inbetween
 last
 
 [case testImportErrorLineNumber]
-try:
-    import enum
-    import dataclasses, missing  # type: ignore[import]
-except ImportError as e:
-    line = e.__traceback__.tb_lineno # type: ignore[attr-defined]
-    assert line == 3, f"traceback's line number is {line}, expected 3"
+def test_error() -> None:
+    try:
+        import enum
+        import dataclasses, missing  # type: ignore[import]
+    except ImportError as e:
+        line = e.__traceback__.tb_lineno # type: ignore[attr-defined]
+        assert line == 4, f"traceback's line number is {line}, expected 4"
 
 [case testImportGroupIsolation]
 def func() -> None:
     import second
 
-import first
-func()
+def test_isolation() -> None:
+    import first
+    func()
 
 [file first.py]
 print("first")
diff --git a/mypyc/test-data/run-integers.test b/mypyc/test-data/run-integers.test
index d575e141b567..1163c9d942f7 100644
--- a/mypyc/test-data/run-integers.test
+++ b/mypyc/test-data/run-integers.test
@@ -538,3 +538,37 @@ def test_int_bool_min_max() -> None:
     assert min(u, z) == -10
     assert max(u, y) == False
     assert max(u, z) == True
+
+[case testIsInstance]
+from copysubclass import subc
+from typing import Any
+def test_built_in() -> None:
+    i: Any = 0
+    assert isinstance(i + 0, int)
+    assert isinstance(i + 9223372036854775808, int)
+    assert isinstance(i + -9223372036854775808, int)
+    assert isinstance(subc(), int)
+    assert isinstance(subc(9223372036854775808), int)
+    assert isinstance(subc(-9223372036854775808), int)
+
+    assert not isinstance(set(), int)
+    assert not isinstance((), int)
+    assert not isinstance((1,2,3), int)
+    assert not isinstance({1,2}, int)
+    assert not isinstance(float(0) + 1.0, int)
+    assert not isinstance(str() + '1', int)
+
+def test_user_defined() -> None:
+    from userdefinedint import int
+
+    i: Any = 42
+    assert isinstance(int(), int)
+    assert not isinstance(i, int)
+
+[file copysubclass.py]
+class subc(int):
+    pass
+
+[file userdefinedint.py]
+class int:
+    pass
diff --git a/mypyc/test-data/run-lists.test b/mypyc/test-data/run-lists.test
index 07c6d7735f10..1569579c1156 100644
--- a/mypyc/test-data/run-lists.test
+++ b/mypyc/test-data/run-lists.test
@@ -51,6 +51,32 @@ print(2, a)
 1 [-1, 5]
 2 [340282366920938463463374607431768211461, -170141183460469231731687303715884105736]
 
+[case testListClear]
+from typing import List, Any
+from copysubclass import subc
+
+def test_list_clear() -> None:
+    l1 = [1, 2, 3, -4, 5]
+    l1.clear()
+    assert l1 == []
+    l1.clear()
+    assert l1 == []
+    l2: List[Any] = []
+    l2.clear()
+    assert l2 == []
+    l3 = [1, 2, 3, "abcdef"]
+    l3.clear()
+    assert l3 == []
+    # subclass testing
+    l4: subc = subc([1, 2, 3])
+    l4.clear()
+    assert l4 == []
+
+[file copysubclass.py]
+from typing import Any
+class subc(list[Any]):
+    pass
+
 [case testListCopy]
 from typing import List
 from copysubclass import subc
@@ -124,7 +150,9 @@ print(primes(13))
 \[0, 0, 1, 1]
 \[0, 0, 1, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1]
 
-[case testListBuild]
+[case testListPrimitives]
+from testutil import assertRaises
+
 def test_list_build() -> None:
     # Currently LIST_BUILDING_EXPANSION_THRESHOLD equals to 10
     # long list built by list_build_op
@@ -143,9 +171,6 @@ def test_list_build() -> None:
     l3.append('a')
     assert l3 == ['a']
 
-[case testListPrims]
-from typing import List
-
 def test_append() -> None:
     l = [1, 2]
     l.append(10)
@@ -163,10 +188,28 @@ def test_pop_last() -> None:
 
 def test_pop_index() -> None:
     l = [1, 2, 10, 3]
-    l.pop(2)
+    assert l.pop(2) == 10
     assert l == [1, 2, 3]
-    l.pop(-2)
+    assert l.pop(-2) == 2
     assert l == [1, 3]
+    assert l.pop(-2) == 1
+    assert l.pop(0) == 3
+    assert l == []
+    l = [int() + 1000, int() + 1001, int() + 1002]
+    assert l.pop(0) == 1000
+    assert l.pop(-1) == 1002
+    assert l == [1001]
+
+def test_pop_index_errors() -> None:
+    l = [int() + 1000]
+    with assertRaises(IndexError):
+        l.pop(1)
+    with assertRaises(IndexError):
+        l.pop(-2)
+    with assertRaises(OverflowError):
+        l.pop(1 << 100)
+    with assertRaises(OverflowError):
+        l.pop(-(1 << 100))
 
 def test_count() -> None:
     l = [1, 3]
@@ -321,7 +364,6 @@ def test_multiply() -> None:
     assert l1 == [1, 1, 1]
 
 [case testOperatorInExpression]
-
 def tuple_in_int0(i: int) -> bool:
     return i in []
 
@@ -373,74 +415,71 @@ def list_not_in_str(s: "str") -> bool:
 def list_in_mixed(i: object):
     return i in [[], (), "", 0, 0.0, False, 0j, {}, set(), type]
 
-[file driver.py]
-
-from native import *
-
-assert not tuple_in_int0(0)
-assert not tuple_in_int1(0)
-assert tuple_in_int1(1)
-assert not tuple_in_int3(0)
-assert tuple_in_int3(1)
-assert tuple_in_int3(2)
-assert tuple_in_int3(3)
-assert not tuple_in_int3(4)
-
-assert tuple_not_in_int0(0)
-assert tuple_not_in_int1(0)
-assert not tuple_not_in_int1(1)
-assert tuple_not_in_int3(0)
-assert not tuple_not_in_int3(1)
-assert not tuple_not_in_int3(2)
-assert not tuple_not_in_int3(3)
-assert tuple_not_in_int3(4)
-
-assert tuple_in_str("foo")
-assert tuple_in_str("bar")
-assert tuple_in_str("baz")
-assert not tuple_in_str("apple")
-assert not tuple_in_str("pie")
-assert not tuple_in_str("\0")
-assert not tuple_in_str("")
-
-assert not list_in_int0(0)
-assert not list_in_int1(0)
-assert list_in_int1(1)
-assert not list_in_int3(0)
-assert list_in_int3(1)
-assert list_in_int3(2)
-assert list_in_int3(3)
-assert not list_in_int3(4)
-
-assert list_not_in_int0(0)
-assert list_not_in_int1(0)
-assert not list_not_in_int1(1)
-assert list_not_in_int3(0)
-assert not list_not_in_int3(1)
-assert not list_not_in_int3(2)
-assert not list_not_in_int3(3)
-assert list_not_in_int3(4)
-
-assert list_in_str("foo")
-assert list_in_str("bar")
-assert list_in_str("baz")
-assert not list_in_str("apple")
-assert not list_in_str("pie")
-assert not list_in_str("\0")
-assert not list_in_str("")
-
-assert list_in_mixed(0)
-assert list_in_mixed([])
-assert list_in_mixed({})
-assert list_in_mixed(())
-assert list_in_mixed(False)
-assert list_in_mixed(0.0)
-assert not list_in_mixed([1])
-assert not list_in_mixed(object)
-assert list_in_mixed(type)
+def test_in_operator_various_cases() -> None:
+    assert not tuple_in_int0(0)
+    assert not tuple_in_int1(0)
+    assert tuple_in_int1(1)
+    assert not tuple_in_int3(0)
+    assert tuple_in_int3(1)
+    assert tuple_in_int3(2)
+    assert tuple_in_int3(3)
+    assert not tuple_in_int3(4)
+
+    assert tuple_not_in_int0(0)
+    assert tuple_not_in_int1(0)
+    assert not tuple_not_in_int1(1)
+    assert tuple_not_in_int3(0)
+    assert not tuple_not_in_int3(1)
+    assert not tuple_not_in_int3(2)
+    assert not tuple_not_in_int3(3)
+    assert tuple_not_in_int3(4)
+
+    assert tuple_in_str("foo")
+    assert tuple_in_str("bar")
+    assert tuple_in_str("baz")
+    assert not tuple_in_str("apple")
+    assert not tuple_in_str("pie")
+    assert not tuple_in_str("\0")
+    assert not tuple_in_str("")
+
+    assert not list_in_int0(0)
+    assert not list_in_int1(0)
+    assert list_in_int1(1)
+    assert not list_in_int3(0)
+    assert list_in_int3(1)
+    assert list_in_int3(2)
+    assert list_in_int3(3)
+    assert not list_in_int3(4)
+
+    assert list_not_in_int0(0)
+    assert list_not_in_int1(0)
+    assert not list_not_in_int1(1)
+    assert list_not_in_int3(0)
+    assert not list_not_in_int3(1)
+    assert not list_not_in_int3(2)
+    assert not list_not_in_int3(3)
+    assert list_not_in_int3(4)
+
+    assert list_in_str("foo")
+    assert list_in_str("bar")
+    assert list_in_str("baz")
+    assert not list_in_str("apple")
+    assert not list_in_str("pie")
+    assert not list_in_str("\0")
+    assert not list_in_str("")
+
+    assert list_in_mixed(0)
+    assert list_in_mixed([])
+    assert list_in_mixed({})
+    assert list_in_mixed(())
+    assert list_in_mixed(False)
+    assert list_in_mixed(0.0)
+    assert not list_in_mixed([1])
+    assert not list_in_mixed(object)
+    assert list_in_mixed(type)
 
 [case testListBuiltFromGenerator]
-def test() -> None:
+def test_from_gen() -> None:
     source_a = ["a", "b", "c"]
     a = list(x + "f2" for x in source_a)
     assert a == ["af2", "bf2", "cf2"]
@@ -460,11 +499,16 @@ def test() -> None:
     f = list("str:" + x for x in source_str)
     assert f == ["str:a", "str:b", "str:c", "str:d"]
 
-[case testNextBug]
-from typing import List, Optional
+[case testNext]
+from typing import List
 
-def test(x: List[int]) -> None:
-    res = next((i for i in x), None)
+def get_next(x: List[int]) -> int:
+    return next((i for i in x), -1)
+
+def test_next() -> None:
+    assert get_next([]) == -1
+    assert get_next([1]) == 1
+    assert get_next([3,2,1]) == 3
 
 [case testListGetItemWithBorrow]
 from typing import List
@@ -511,3 +555,35 @@ def test_sorted() -> None:
     assert sorted((2, 1, 3)) == res
     assert sorted({2, 1, 3}) == res
     assert sorted({2: "", 1: "", 3: ""}) == res
+
+[case testIsInstance]
+from copysubclass import subc
+def test_built_in() -> None:
+    assert isinstance([], list)
+    assert isinstance([1,2,3], list)
+    assert isinstance(['a','b'], list)
+    assert isinstance(subc(), list)
+    assert isinstance(subc([1,2,3]), list)
+    assert isinstance(subc(['a','b']), list)
+
+    assert not isinstance({}, list)
+    assert not isinstance((), list)
+    assert not isinstance((1,2,3), list)
+    assert not isinstance(('a','b'), list)
+    assert not isinstance(1, list)
+    assert not isinstance('a', list)
+
+def test_user_defined() -> None:
+    from userdefinedlist import list
+
+    assert isinstance(list(), list)
+    assert not isinstance([list()], list)
+
+[file copysubclass.py]
+from typing import Any
+class subc(list[Any]):
+    pass
+
+[file userdefinedlist.py]
+class list:
+    pass
diff --git a/mypyc/test-data/run-misc.test b/mypyc/test-data/run-misc.test
index f6a1c744cade..129946a4c330 100644
--- a/mypyc/test-data/run-misc.test
+++ b/mypyc/test-data/run-misc.test
@@ -109,10 +109,11 @@ def gen(b: bool) -> Generator[Any, None, None]:
         y = None
     yield y
 
-assert f(False) == ((1, None), (None, 1))
-assert f(True) == ((None, 1), (1, None))
-assert next(gen(False)) is None
-assert next(gen(True)) == 1
+def test_inferred() -> None:
+    assert f(False) == ((1, None), (None, 1))
+    assert f(True) == ((None, 1), (1, None))
+    assert next(gen(False)) is None
+    assert next(gen(True)) == 1
 
 [case testWith]
 from typing import Any
@@ -829,23 +830,23 @@ assert call_any_nested([[1, 1, 1], [1, 1], []]) == 1
 assert call_any_nested([[1, 1, 1], [0, 1], []]) == 0
 
 [case testSum]
-[typing fixtures/typing-full.pyi]
-from typing import Any, List
+from typing import List
 
+empty: List[int] = []
 def test_sum_of_numbers() -> None:
     assert sum(x for x in [1, 2, 3]) == 6
-    assert sum(x for x in [0.0, 1.2, 2]) == 6.2
+    assert sum(x for x in [0.0, 1.2, 2]) == 3.2
     assert sum(x for x in [1, 1j]) == 1 + 1j
 
 def test_sum_callables() -> None:
-    assert sum((lambda x: x == 0)(x) for x in []) == 0
+    assert sum((lambda x: x == 0)(x) for x in empty) == 0
     assert sum((lambda x: x == 0)(x) for x in [0]) == 1
     assert sum((lambda x: x == 0)(x) for x in [0, 0, 0]) == 3
     assert sum((lambda x: x == 0)(x) for x in [0, 1, 0]) == 2
     assert sum((lambda x: x % 2 == 0)(x) for x in range(2**10)) == 2**9
 
 def test_sum_comparisons() -> None:
-    assert sum(x == 0 for x in []) == 0
+    assert sum(x == 0 for x in empty) == 0
     assert sum(x == 0 for x in [0]) == 1
     assert sum(x == 0 for x in [0, 0, 0]) == 3
     assert sum(x == 0 for x in [0, 1, 0]) == 2
@@ -865,13 +866,14 @@ def test_sum_misc() -> None:
 def test_sum_start_given() -> None:
     a = 1
     assert sum((x == 0 for x in [0, 1]), a) == 2
-    assert sum(((lambda x: x == 0)(x) for x in []), 1) == 1
+    assert sum(((lambda x: x == 0)(x) for x in empty), 1) == 1
     assert sum(((lambda x: x == 0)(x) for x in [0]), 1) == 2
     assert sum(((lambda x: x == 0)(x) for x in [0, 0, 0]), 1) == 4
     assert sum(((lambda x: x == 0)(x) for x in [0, 1, 0]), 1) == 3
     assert sum(((lambda x: x % 2 == 0)(x) for x in range(2**10)), 1) == 2**9 + 1
     assert sum((x for x in [1, 1j]), 2j) == 1 + 3j
     assert sum((c == 'd' for c in 'abcdd'), 1) == 3
+[typing fixtures/typing-full.pyi]
 
 [case testNoneStuff]
 from typing import Optional
@@ -1090,19 +1092,20 @@ def test_complex() -> None:
 from typing import cast
 import sys
 
-A = sys.platform == 'x' and foobar
-B = sys.platform == 'x' and sys.foobar
-C = sys.platform == 'x' and f(a, -b, 'y') > [c + e, g(y=2)]
-C = sys.platform == 'x' and cast(a, b[c])
-C = sys.platform == 'x' and (lambda x: y + x)
-C = sys.platform == 'x' and (x for y in z)
-C = sys.platform == 'x' and [x for y in z]
-C = sys.platform == 'x' and {x: x for y in z}
-C = sys.platform == 'x' and {x for y in z}
-
-assert not A
-assert not B
-assert not C
+def test_unreachable() -> None:
+    A = sys.platform == 'x' and foobar
+    B = sys.platform == 'x' and sys.foobar
+    C = sys.platform == 'x' and f(a, -b, 'y') > [c + e, g(y=2)]
+    C = sys.platform == 'x' and cast(a, b[c])
+    C = sys.platform == 'x' and (lambda x: y + x)
+    C = sys.platform == 'x' and (x for y in z)
+    C = sys.platform == 'x' and [x for y in z]
+    C = sys.platform == 'x' and {x: x for y in z}
+    C = sys.platform == 'x' and {x for y in z}
+
+    assert not A
+    assert not B
+    assert not C
 
 [case testDoesntSegfaultWhenTopLevelFails]
 # make the initial import fail
@@ -1126,6 +1129,10 @@ class B(A):
     def _(arg): pass
     def _(arg): pass
 
+def test_underscore() -> None:
+    A()
+    B()
+
 [case testGlobalRedefinition_toplevel]
 # mypy: allow-redefinition
 i = 0
diff --git a/mypyc/test-data/run-python38.test b/mypyc/test-data/run-python38.test
index 7de43907cb86..cf7c7d7dea52 100644
--- a/mypyc/test-data/run-python38.test
+++ b/mypyc/test-data/run-python38.test
@@ -75,11 +75,12 @@ class Bar(Foo):
     def f(self, *args: int, **kwargs: int) -> None:
         print("stuff", args, kwargs)
 
-z: Foo = Bar()
-z.f(1, z=50)
-z.f()
-z.f(1)
-z.f(z=50)
+def test_pos_only() -> None:
+    z: Foo = Bar()
+    z.f(1, z=50)
+    z.f()
+    z.f(1)
+    z.f(z=50)
 
 [out]
 stuff (1,) {'z': 50}
diff --git a/mypyc/test-data/run-sets.test b/mypyc/test-data/run-sets.test
index 68edd1e6b77d..2668d63bcdac 100644
--- a/mypyc/test-data/run-sets.test
+++ b/mypyc/test-data/run-sets.test
@@ -265,3 +265,55 @@ def test_in_set() -> None:
 
 def test_for_set() -> None:
     assert not s ^ {None, False, 1, 2.0, "3", b"4", 5j, (6,), CONST}, s
+
+[case testIsInstance]
+from copysubclass import subset, subfrozenset
+def test_built_in_set() -> None:
+    assert isinstance(set(), set)
+    assert isinstance({'one', 'two'}, set)
+    assert isinstance({'a', 1}, set)
+    assert isinstance(subset(), set)
+    assert isinstance(subset({'one', 'two'}), set)
+    assert isinstance(subset({'a', 1}), set)
+
+    assert not isinstance(frozenset(), set)
+    assert not isinstance({}, set)
+    assert not isinstance([], set)
+    assert not isinstance((1,2,3), set)
+    assert not isinstance({1:'a', 2:'b'}, set)
+    assert not isinstance(int() + 1, set)
+    assert not isinstance(str() + 'a', set)
+
+def test_user_defined_set() -> None:
+    from userdefinedset import set
+
+    assert isinstance(set(), set)
+    assert not isinstance({set()}, set)
+
+def test_built_in_frozenset() -> None:
+    assert isinstance(frozenset(), frozenset)
+    assert isinstance(frozenset({'one', 'two'}), frozenset)
+    assert isinstance(frozenset({'a', 1}), frozenset)
+    assert isinstance(subfrozenset(), frozenset)
+    assert isinstance(subfrozenset({'one', 'two'}), frozenset)
+    assert isinstance(subfrozenset({'a', 1}), frozenset)
+
+    assert not isinstance(set(), frozenset)
+    assert not isinstance({}, frozenset)
+    assert not isinstance([], frozenset)
+    assert not isinstance((1,2,3), frozenset)
+    assert not isinstance({1:'a', 2:'b'}, frozenset)
+    assert not isinstance(int() + 1, frozenset)
+    assert not isinstance(str() + 'a', frozenset)
+
+[file copysubclass.py]
+from typing import Any
+class subset(set[Any]):
+    pass
+
+class subfrozenset(frozenset[Any]):
+    pass
+
+[file userdefinedset.py]
+class set:
+    pass
diff --git a/mypyc/test-data/run-signatures.test b/mypyc/test-data/run-signatures.test
new file mode 100644
index 000000000000..0a9ea32f5357
--- /dev/null
+++ b/mypyc/test-data/run-signatures.test
@@ -0,0 +1,223 @@
+[case testSignaturesBasic]
+def f1(): pass
+def f2(x): pass
+def f3(x, /): pass
+def f4(*, x): pass
+def f5(*x): pass
+def f6(**x): pass
+def f7(x=None): pass
+def f8(x=None, /): pass
+def f9(*, x=None): pass
+def f10(a, /, b, c=None, *args, d=None, **h): pass
+
+[file driver.py]
+import inspect
+from native import *
+
+assert str(inspect.signature(f1)) == "()"
+assert str(inspect.signature(f2)) == "(x)"
+assert str(inspect.signature(f3)) == "(x, /)"
+assert str(inspect.signature(f4)) == "(*, x)"
+assert str(inspect.signature(f5)) == "(*x)"
+assert str(inspect.signature(f6)) == "(**x)"
+assert str(inspect.signature(f7)) == "(x=None)"
+assert str(inspect.signature(f8)) == "(x=None, /)"
+assert str(inspect.signature(f9)) == "(*, x=None)"
+assert str(inspect.signature(f10)) == "(a, /, b, c=None, *args, d=None, **h)"
+
+for fn in [f1, f2, f3, f4, f5, f6, f7, f8, f9, f10]:
+    assert getattr(fn, "__doc__") is None
+
+[case testSignaturesValidDefaults]
+from typing import Final
+A: Final = 1
+
+def default_int(x=1): pass
+def default_str(x="a"): pass
+def default_float(x=1.0): pass
+def default_true(x=True): pass
+def default_false(x=False): pass
+def default_none(x=None): pass
+def default_tuple_empty(x=()): pass
+def default_tuple_literals(x=(1, "a", 1.0, False, True, None, (), (1,2,(3,4)))): pass
+def default_tuple_singleton(x=(1,)): pass
+def default_named_constant(x=A): pass
+
+[file driver.py]
+import inspect
+from native import *
+
+assert str(inspect.signature(default_int)) == "(x=1)"
+assert str(inspect.signature(default_str)) == "(x='a')"
+assert str(inspect.signature(default_float)) == "(x=1.0)"
+assert str(inspect.signature(default_true)) == "(x=True)"
+assert str(inspect.signature(default_false)) == "(x=False)"
+assert str(inspect.signature(default_none)) == "(x=None)"
+assert str(inspect.signature(default_tuple_empty)) == "(x=())"
+assert str(inspect.signature(default_tuple_literals)) == "(x=(1, 'a', 1.0, False, True, None, (), (1, 2, (3, 4))))"
+assert str(inspect.signature(default_named_constant)) == "(x=1)"
+
+# Check __text_signature__ directly since inspect.signature produces
+# an incorrect signature for 1-tuple default arguments prior to
+# Python 3.12 (cpython#102379).
+# assert str(inspect.signature(default_tuple_singleton)) == "(x=(1,))"
+assert getattr(default_tuple_singleton, "__text_signature__") == "(x=(1,))"
+
+[case testSignaturesStringDefaults]
+def f1(x="'foo"): pass
+def f2(x='"foo'): pass
+def f3(x=""""Isn\'t," they said."""): pass
+def f4(x="\\ \a \b \f \n \r \t \v \x00"): pass
+def f5(x="\N{BANANA}sv"): pass
+
+[file driver.py]
+import inspect
+from native import *
+
+assert str(inspect.signature(f1)) == """(x="'foo")"""
+assert str(inspect.signature(f2)) == """(x='"foo')"""
+assert str(inspect.signature(f3)) == r"""(x='"Isn\'t," they said.')"""
+assert str(inspect.signature(f4)) == r"""(x='\\ \x07 \x08 \x0c \n \r \t \x0b \x00')"""
+assert str(inspect.signature(f5)) == """(x='\N{BANANA}sv')"""
+
+[case testSignaturesIrrepresentableDefaults]
+import enum
+class Color(enum.Enum):
+    RED = 1
+misc = object()
+
+# Default arguments that cannot be represented in a __text_signature__
+def bad_object(x=misc): pass
+def bad_list_nonliteral(x=[misc]): pass
+def bad_dict_nonliteral(x={'a': misc}): pass
+def bad_set_nonliteral(x={misc}): pass
+def bad_set_empty(x=set()): pass  # supported by ast.literal_eval, but not by inspect._signature_fromstr
+def bad_nan(x=float("nan")): pass
+def bad_enum(x=Color.RED): pass
+
+# TODO: Default arguments that could potentially be represented in a
+# __text_signature__, but which are not currently supported.
+# See 'inspect._signature_fromstr' for what default values are supported at runtime.
+def bad_complex(x=1+2j): pass
+def bad_list_empty(x=[]): pass
+def bad_list_literals(x=[1, 2, 3]): pass
+def bad_dict_empty(x={}): pass
+def bad_dict_literals(x={'a': 1}): pass
+def bad_set_literals(x={1, 2, 3}): pass
+def bad_tuple_literals(x=([1, 2, 3], {'a': 1}, {1, 2, 3})): pass
+def bad_ellipsis(x=...): pass
+def bad_literal_fold(x=1+2): pass
+
+[file driver.py]
+import inspect
+from testutil import assertRaises
+import native
+
+all_bad = [fn for name, fn in vars(native).items() if name.startswith("bad_")]
+assert all_bad
+
+for bad in all_bad:
+    assert bad.__text_signature__ is None, f"{bad.__name__} has unexpected __text_signature__"
+    with assertRaises(ValueError, "no signature found for builtin"):
+        inspect.signature(bad)
+
+[case testSignaturesMethods]
+class Foo:
+    def f1(self, x): pass
+    @classmethod
+    def f2(cls, x): pass
+    @staticmethod
+    def f3(x): pass
+    def __eq__(self, x: object): pass
+
+[file driver.py]
+import inspect
+from native import *
+
+assert str(inspect.signature(Foo.f1)) == "(self, /, x)"
+assert str(inspect.signature(Foo().f1)) == "(x)"
+
+assert str(inspect.signature(Foo.f2)) == "(x)"
+assert str(inspect.signature(Foo().f2)) == "(x)"
+
+assert str(inspect.signature(Foo.f3)) == "(x)"
+assert str(inspect.signature(Foo().f3)) == "(x)"
+
+assert str(inspect.signature(Foo.__eq__)) == "(self, value, /)"
+assert str(inspect.signature(Foo().__eq__)) == "(value, /)"
+
+[case testSignaturesConstructors]
+class Empty: pass
+
+class HasInit:
+    def __init__(self, x) -> None: pass
+
+class InheritedInit(HasInit): pass
+
+class HasInitBad:
+    def __init__(self, x=[]) -> None: pass
+
+[file driver.py]
+import inspect
+from testutil import assertRaises
+from native import *
+
+assert str(inspect.signature(Empty)) == "()"
+assert str(inspect.signature(Empty.__init__)) == "(self, /, *args, **kwargs)"
+
+assert str(inspect.signature(HasInit)) == "(x)"
+assert str(inspect.signature(HasInit.__init__)) == "(self, /, *args, **kwargs)"
+
+assert str(inspect.signature(InheritedInit)) == "(x)"
+assert str(inspect.signature(InheritedInit.__init__)) == "(self, /, *args, **kwargs)"
+
+assert getattr(HasInitBad, "__text_signature__") is None
+with assertRaises(ValueError, "no signature found for builtin"):
+    inspect.signature(HasInitBad)
+
+# CPython detail note: type objects whose tp_doc contains only a text signature behave
+# differently from method objects whose ml_doc contains only a test signature: type
+# objects will have __doc__="" whereas method objects will have __doc__=None. This
+# difference stems from the former using _PyType_GetDocFromInternalDoc(...) and the
+# latter using PyUnicode_FromString(_PyType_DocWithoutSignature(...)).
+for cls in [Empty, HasInit, InheritedInit]:
+    assert getattr(cls, "__doc__") == ""
+assert getattr(HasInitBad, "__doc__") is None
+
+[case testSignaturesConstructorsNonExt]
+from mypy_extensions import mypyc_attr
+
+@mypyc_attr(native_class=False)
+class NonExt:
+    def __init__(self, x) -> None: pass
+
+[file driver.py]
+import inspect
+from testutil import assertRaises
+from native import *
+
+# TODO: support constructor signatures for non-extension classes
+with assertRaises(ValueError, "no signature found for builtin"):
+    inspect.signature(NonExt)
+
+[case testSignaturesHistoricalPositionalOnly]
+import inspect
+
+def f1(__x): pass
+def f2(__x, y): pass
+def f3(*, __y): pass
+def f4(x, *, __y): pass
+def f5(__x, *, __y): pass
+
+class A:
+    def func(self, __x): pass
+
+def test_historical_positional_only() -> None:
+    assert str(inspect.signature(f1)) == "(__x, /)"
+    assert str(inspect.signature(f2)) == "(__x, /, y)"
+    assert str(inspect.signature(f3)) == "(*, __y)"
+    assert str(inspect.signature(f4)) == "(x, *, __y)"
+    assert str(inspect.signature(f5)) == "(__x, /, *, __y)"
+
+    assert str(inspect.signature(A.func)) == "(self, __x, /)"
+    assert str(inspect.signature(A().func)) == "(__x, /)"
diff --git a/mypyc/test-data/run-singledispatch.test b/mypyc/test-data/run-singledispatch.test
index 61e4897c96d6..a119c325984a 100644
--- a/mypyc/test-data/run-singledispatch.test
+++ b/mypyc/test-data/run-singledispatch.test
@@ -152,12 +152,14 @@ from functools import singledispatch
 def fun(arg) -> bool:
     return False
 
-try:
-    @fun.register
-    def fun_specialized(arg: None) -> bool:
-        return True
-except TypeError:
-    pass
+def test_argument() -> None:
+    try:
+        @fun.register
+        def fun_specialized(arg: None) -> bool:
+            return True
+        assert False, "expected to raise an exception"
+    except TypeError:
+        pass
 
 [case testRegisteringTheSameFunctionSeveralTimes]
 from functools import singledispatch
@@ -598,9 +600,11 @@ assert f(1) == 'default'
 def _(arg: B) -> str:
     return 'b'
 
-assert f(A()) == 'a'
-assert f(B()) == 'b'
-assert f(1) == 'default'
+# TODO: Move whole testcase to a function when mypyc#1118 is fixed.
+def test_final() -> None:
+    assert f(A()) == 'a'
+    assert f(B()) == 'b'
+    assert f(1) == 'default'
 
 
 [case testDynamicallyRegisteringFunctionFromInterpretedCode]
diff --git a/mypyc/test-data/run-strings.test b/mypyc/test-data/run-strings.test
index 9183b45b036a..6a62db6ee3ee 100644
--- a/mypyc/test-data/run-strings.test
+++ b/mypyc/test-data/run-strings.test
@@ -92,6 +92,64 @@ assert remove_prefix_suffix('', '') == ('', '')
 assert remove_prefix_suffix('abc', 'a') == ('bc', 'abc')
 assert remove_prefix_suffix('abc', 'c') == ('abc', 'ab')
 
+[case testStringEquality]
+def eq(a: str, b: str) -> bool:
+    return a == b
+def ne(a: str, b: str) -> bool:
+    return a != b
+
+def test_basic() -> None:
+    xy = "xy"
+    xy2 = str().join(["x", "y"])
+    xx = "xx"
+    yy = "yy"
+    xxx = "xxx"
+
+    assert eq("", str())
+    assert not ne("", str())
+
+    assert eq("x", "x" + str())
+    assert ne("x", "y")
+
+    assert eq(xy, xy)
+    assert eq(xy, xy2)
+    assert not eq(xy, yy)
+    assert ne(xy, xx)
+    assert not ne(xy, xy)
+    assert not ne(xy, xy2)
+
+    assert ne(xx, xxx)
+    assert ne(xxx, xx)
+    assert ne("x", "")
+    assert ne("", "x")
+
+    assert ne("XX", xx)
+    assert ne(yy, xy)
+
+def test_unicode() -> None:
+    assert eq(chr(200), chr(200) + str())
+    assert ne(chr(200), chr(201))
+
+    assert eq(chr(1234), chr(1234) + str())
+    assert ne(chr(1234), chr(1235))
+
+    assert eq("\U0001f4a9", "\U0001f4a9" + str())
+    assert eq("\U0001f4a9", "\U0001F4A9" + str())
+    assert ne("\U0001f4a9", "\U0002f4a9" + str())
+    assert ne("\U0001f4a9", "\U0001f5a9" + str())
+    assert ne("\U0001f4a9", "\U0001f4a8" + str())
+
+    assert eq("foobar\u1234", "foobar\u1234" + str())
+    assert eq("\u1234foobar", "\u1234foobar" + str())
+    assert ne("foobar\uf234", "foobar\uf235")
+    assert ne("foobar\uf234", "foobar\uf334")
+    assert ne("foobar\u1234", "Foobar\u1234" + str())
+
+    assert eq("foo\U0001f4a9", "foo\U0001f4a9" + str())
+    assert eq("\U0001f4a9foo", "\U0001f4a9foo" + str())
+    assert ne("foo\U0001f4a9", "foo\U0001f4a8" + str())
+    assert ne("\U0001f4a9foo", "\U0001f4a8foo" + str())
+
 [case testStringOps]
 from typing import List, Optional, Tuple
 from testutil import assertRaises
@@ -305,7 +363,6 @@ def test_str_min_max() -> None:
     assert max(x, z) == 'aaa'
 
 [case testStringFormattingCStyle]
-[typing fixtures/typing-full.pyi]
 from typing import Tuple
 
 var = 'mypyc'
@@ -350,13 +407,21 @@ def test_basics() -> None:
     inf_num = float('inf')
     assert '%s, %s' % (nan_num, inf_num) == 'nan, inf'
     assert '%f, %f' % (nan_num, inf_num) == 'nan, inf'
+[typing fixtures/typing-full.pyi]
 
 [case testFStrings]
 import decimal
 from datetime import datetime
+from typing import Final
 
 var = 'mypyc'
 num = 20
+final_known_at_compile_time: Final = 'hello'
+
+def final_value_setter() -> str:
+    return 'goodbye'
+
+final_unknown_at_compile_time: Final = final_value_setter()
 
 def test_fstring_basics() -> None:
     assert f'Hello {var}, this is a test' == "Hello mypyc, this is a test"
@@ -393,6 +458,8 @@ def test_fstring_basics() -> None:
     inf_num = float('inf')
     assert f'{nan_num}, {inf_num}' == 'nan, inf'
 
+    assert f'{final_known_at_compile_time} {final_unknown_at_compile_time}' == 'hello goodbye'
+
 # F-strings would be translated into ''.join[string literals, format method call, ...] in mypy AST.
 # Currently we are using a str.join specializer for f-string speed up. We might not cover all cases
 # and the rest ones should fall back to a normal str.join method call.
@@ -734,14 +801,23 @@ def test_ord() -> None:
         ord('')
 
 [case testDecode]
+from testutil import assertRaises
+
 def test_decode() -> None:
     assert "\N{GREEK CAPITAL LETTER DELTA}" == '\u0394'
     assert "\u0394" == "\u0394"
     assert "\U00000394" == '\u0394'
     assert b'\x80abc'.decode('utf-8', 'replace') == '\ufffdabc'
     assert b'\x80abc'.decode('utf-8', 'backslashreplace') == '\\x80abc'
+    assert b''.decode() == ''
+    assert b'a'.decode() == 'a'
     assert b'abc'.decode() == 'abc'
     assert b'abc'.decode('utf-8') == 'abc'
+    assert b'abc'.decode('utf-8' + str()) == 'abc'
+    assert b'abc\x00\xce'.decode('latin-1') == 'abc\x00\xce'
+    assert b'abc\x00\xce'.decode('latin-1' + str()) == 'abc\x00\xce'
+    assert b'abc\x00\x7f'.decode('ascii') == 'abc\x00\x7f'
+    assert b'abc\x00\x7f'.decode('ascii' + str()) == 'abc\x00\x7f'
     assert b'\x80abc'.decode('utf-8', 'ignore') == 'abc'
     assert b'\x80abc'.decode('UTF-8', 'ignore') == 'abc'
     assert b'\x80abc'.decode('Utf-8', 'ignore') == 'abc'
@@ -750,16 +826,71 @@ def test_decode() -> None:
     assert b'\xd2\xbb\xb6\xfe\xc8\xfd'.decode('gbk', 'ignore') == '一二三'
     assert b'\xd2\xbb\xb6\xfe\xc8\xfd'.decode('latin1', 'ignore') == 'Ò»¶þÈý'
     assert b'Z\xc3\xbcrich'.decode("utf-8") == 'Zürich'
-    try:
-        b'Z\xc3\xbcrich'.decode('ascii')
-        assert False
-    except UnicodeDecodeError:
-        pass
+    assert b'Z\xc3\xbcrich'.decode("utf-8" + str()) == 'Zürich'
+
     assert bytearray(range(5)).decode() == '\x00\x01\x02\x03\x04'
     b = bytearray(b'\xe4\xbd\xa0\xe5\xa5\xbd')
     assert b.decode() == '你好'
     assert b.decode('gbk') == '浣犲ソ'
     assert b.decode('latin1') == 'ä½\xa0好'
+    assert b.decode('latin1' + str()) == 'ä½\xa0好'
+
+def test_decode_error() -> None:
+    try:
+        b'Z\xc3\xbcrich'.decode('ascii')
+        assert False
+    except UnicodeDecodeError:
+        pass
+    try:
+        b'Z\xc3\xbcrich'.decode('ascii' + str())
+        assert False
+    except UnicodeDecodeError:
+        pass
+    try:
+        b'Z\xc3y'.decode('utf8')
+        assert False
+    except UnicodeDecodeError:
+        pass
+    try:
+        b'Z\xc3y'.decode('utf8' + str())
+        assert False
+    except UnicodeDecodeError:
+        pass
+
+def test_decode_bytearray() -> None:
+    b: bytes = bytearray(b'foo\x00bar')
+    assert b.decode() == 'foo\x00bar'
+    assert b.decode('utf-8') == 'foo\x00bar'
+    assert b.decode('latin-1') == 'foo\x00bar'
+    assert b.decode('ascii') == 'foo\x00bar'
+    assert b.decode('utf-8' + str()) == 'foo\x00bar'
+    assert b.decode('latin-1' + str()) == 'foo\x00bar'
+    assert b.decode('ascii' + str()) == 'foo\x00bar'
+    b2: bytes = bytearray(b'foo\x00bar\xbe')
+    assert b2.decode('latin-1') == 'foo\x00bar\xbe'
+    with assertRaises(UnicodeDecodeError):
+        b2.decode('ascii')
+    with assertRaises(UnicodeDecodeError):
+        b2.decode('ascii' + str())
+    with assertRaises(UnicodeDecodeError):
+        b2.decode('utf-8')
+    with assertRaises(UnicodeDecodeError):
+        b2.decode('utf-8' + str())
+    b3: bytes = bytearray(b'Z\xc3\xbcrich')
+    assert b3.decode("utf-8") == 'Zürich'
+
+def test_invalid_encoding() -> None:
+    try:
+        b"foo".decode("ut-f-8")
+        assert False
+    except Exception as e:
+        assert repr(e).startswith("LookupError")
+    try:
+        encoding = "ut-f-8"
+        b"foo".decode(encoding)
+        assert False
+    except Exception as e:
+        assert repr(e).startswith("LookupError")
 
 [case testEncode]
 from testutil import assertRaises
@@ -815,3 +946,160 @@ def test_unicode_range() -> None:
     assert "\u2029 \U0010AAAA\U00104444B\u205F ".strip() == "\U0010AAAA\U00104444B"
     assert " \u3000\u205F ".strip() == ""
     assert "\u2029 \U00102865\u205F ".rstrip() == "\u2029 \U00102865"
+
+[case testCount]
+# mypy: disable-error-code="attr-defined"
+def test_count() -> None:
+    string = "abcbcb"
+    assert string.count("a") == 1
+    assert string.count("b") == 3
+    assert string.count("c") == 2
+def test_count_start() -> None:
+    string = "abcbcb"
+    assert string.count("a", 2) == string.count("a", -4) == 0, (string.count("a", 2), string.count("a", -4))
+    assert string.count("b", 2) == string.count("b", -4) == 2, (string.count("b", 2), string.count("b", -4))
+    assert string.count("c", 2) == string.count("c", -4) == 2, (string.count("c", 2), string.count("c", -4))
+    # out of bounds
+    assert string.count("a", 8) == 0
+    assert string.count("a", -8) == 1
+    assert string.count("b", 8) == 0
+    assert string.count("b", -8) == 3
+    assert string.count("c", 8) == 0
+    assert string.count("c", -8) == 2
+def test_count_start_end() -> None:
+    string = "abcbcb"
+    assert string.count("a", 0, 4) == 1, string.count("a", 0, 4)
+    assert string.count("b", 0, 4) == 2, string.count("b", 0, 4)
+    assert string.count("c", 0, 4) == 1, string.count("c", 0, 4)
+def test_count_multi() -> None:
+    string = "aaabbbcccbbbcccbbb"
+    assert string.count("aaa") == 1, string.count("aaa")
+    assert string.count("bbb") == 3, string.count("bbb")
+    assert string.count("ccc") == 2, string.count("ccc")
+def test_count_multi_start() -> None:
+    string = "aaabbbcccbbbcccbbb"
+    assert string.count("aaa", 6) == string.count("aaa", -12) == 0, (string.count("aaa", 6), string.count("aaa", -12))
+    assert string.count("bbb", 6) == string.count("bbb", -12) == 2, (string.count("bbb", 6), string.count("bbb", -12))
+    assert string.count("ccc", 6) == string.count("ccc", -12) == 2, (string.count("ccc", 6), string.count("ccc", -12))
+    # out of bounds
+    assert string.count("aaa", 20) == 0
+    assert string.count("aaa", -20) == 1
+    assert string.count("bbb", 20) == 0
+    assert string.count("bbb", -20) == 3
+    assert string.count("ccc", 20) == 0
+    assert string.count("ccc", -20) == 2
+def test_count_multi_start_end() -> None:
+    string = "aaabbbcccbbbcccbbb"
+    assert string.count("aaa", 0, 12) == 1, string.count("aaa", 0, 12)
+    assert string.count("bbb", 0, 12) == 2, string.count("bbb", 0, 12)
+    assert string.count("ccc", 0, 12) == 1, string.count("ccc", 0, 12)
+def test_count_emoji() -> None:
+    string = "😴🚀ñ🚀ñ🚀"
+    assert string.count("😴") == 1, string.count("😴")
+    assert string.count("🚀") == 3, string.count("🚀")
+    assert string.count("ñ") == 2, string.count("ñ")
+def test_count_start_emoji() -> None:
+    string = "😴🚀ñ🚀ñ🚀"
+    assert string.count("😴", 2) == string.count("😴", -4) == 0, (string.count("😴", 2), string.count("😴", -4))
+    assert string.count("🚀", 2) == string.count("🚀", -4) == 2, (string.count("🚀", 2), string.count("🚀", -4))
+    assert string.count("ñ", 2) == string.count("ñ", -4) == 2, (string.count("ñ", 2), string.count("ñ", -4))
+    # Out of bounds
+    assert string.count("😴", 8) == 0, string.count("😴", 8)
+    assert string.count("😴", -8) == 1, string.count("😴", -8)
+    assert string.count("🚀", 8) == 0, string.count("🚀", 8)
+    assert string.count("🚀", -8) == 3, string.count("🚀", -8)
+    assert string.count("ñ", 8) == 0, string.count("ñ", 8)
+    assert string.count("ñ", -8) == 2, string.count("ñ", -8)
+def test_count_start_end_emoji() -> None:
+    string = "😴🚀ñ🚀ñ🚀"
+    assert string.count("😴", 0, 4) == 1, string.count("😴", 0, 4)
+    assert string.count("🚀", 0, 4) == 2, string.count("🚀", 0, 4)
+    assert string.count("ñ", 0, 4) == 1, string.count("ñ", 0, 4)
+def test_count_multi_emoji() -> None:
+    string = "😴😴😴🚀🚀🚀ñññ🚀🚀🚀ñññ🚀🚀🚀"
+    assert string.count("😴😴😴") == 1, string.count("😴😴😴")
+    assert string.count("🚀🚀🚀") == 3, string.count("🚀🚀🚀")
+    assert string.count("ñññ") == 2, string.count("ñññ")
+def test_count_multi_start_emoji() -> None:
+    string = "😴😴😴🚀🚀🚀ñññ🚀🚀🚀ñññ🚀🚀🚀"
+    assert string.count("😴😴😴", 6) == string.count("😴😴😴", -12) == 0, (string.count("😴😴😴", 6), string.count("😴😴😴", -12))
+    assert string.count("🚀🚀🚀", 6) == string.count("🚀🚀🚀", -12) == 2, (string.count("🚀🚀🚀", 6), string.count("🚀🚀🚀", -12))
+    assert string.count("ñññ", 6) == string.count("ñññ", -12) == 2, (string.count("ñññ", 6), string.count("ñññ", -12))
+    # Out of bounds
+    assert string.count("😴😴😴", 20) == 0, string.count("😴😴😴", 20)
+    assert string.count("😴😴😴", -20) == 1, string.count("😴😴😴", -20)
+    assert string.count("🚀🚀🚀", 20) == 0, string.count("🚀🚀🚀", 20)
+    assert string.count("🚀🚀🚀", -20) == 3, string.count("🚀🚀🚀", -20)
+    assert string.count("ñññ", 20) == 0, string.count("ñññ", 20)
+    assert string.count("ñññ", -20) == 2, string.count("ñññ", -20)
+def test_count_multi_start_end_emoji() -> None:
+    string = "😴😴😴🚀🚀🚀ñññ🚀🚀🚀ñññ🚀🚀🚀"
+    assert string.count("😴😴😴", 0, 12) == 1, string.count("😴😴😴", 0, 12)
+    assert string.count("🚀🚀🚀", 0, 12) == 2, string.count("🚀🚀🚀", 0, 12)
+    assert string.count("ñññ", 0, 12) == 1, string.count("ñññ", 0, 12)
+
+[case testIsInstance]
+from copysubclass import subc
+from typing import Any
+def test_built_in() -> None:
+    s: Any = str()
+    assert isinstance(s, str)
+    assert isinstance(s + "test", str)
+    assert isinstance(s + "ñññ", str)
+    assert isinstance(subc(), str)
+    assert isinstance(subc("test"), str)
+    assert isinstance(subc("ñññ"), str)
+
+    assert not isinstance(set(), str)
+    assert not isinstance((), str)
+    assert not isinstance(('a','b'), str)
+    assert not isinstance({'a','b'}, str)
+    assert not isinstance(int() + 1, str)
+    assert not isinstance(['a','b'], str)
+
+def test_user_defined() -> None:
+    from userdefinedstr import str
+
+    s: Any = "str"
+    assert isinstance(str(), str)
+    assert not isinstance(s, str)
+
+[file copysubclass.py]
+from typing import Any
+class subc(str):
+    pass
+
+[file userdefinedstr.py]
+class str:
+    pass
+
+[case testStrOptionalEquality]
+from __future__ import annotations
+
+def eq_s_opt_s_opt(x: str | None, y: str | None) -> bool:
+    return x == y
+
+def ne_s_opt_s_opt(x: str | None, y: str | None) -> bool:
+    return x != y
+
+def test_optional_eq() -> None:
+    s = 'x'
+    assert eq_s_opt_s_opt(s, s)
+    assert eq_s_opt_s_opt(s + str(int()), s + str(int()))
+    assert eq_s_opt_s_opt(None, None)
+
+    assert not eq_s_opt_s_opt('x', 'y')
+    assert not eq_s_opt_s_opt('y', 'x')
+    assert not eq_s_opt_s_opt(None, 'x')
+    assert not eq_s_opt_s_opt('x', None)
+
+def test_optional_ne() -> None:
+    s = 'x'
+    assert not ne_s_opt_s_opt(s, s)
+    assert not ne_s_opt_s_opt(s + str(int()), s+ str(int()))
+    assert not ne_s_opt_s_opt(None, None)
+
+    assert ne_s_opt_s_opt('x', 'y')
+    assert ne_s_opt_s_opt('y', 'x')
+    assert ne_s_opt_s_opt(None, 'x')
+    assert ne_s_opt_s_opt('x', None)
diff --git a/mypyc/test-data/run-tuples.test b/mypyc/test-data/run-tuples.test
index 1437eaef2aa5..f5e1733d429b 100644
--- a/mypyc/test-data/run-tuples.test
+++ b/mypyc/test-data/run-tuples.test
@@ -131,10 +131,23 @@ import sys
 from typing import Optional
 from native import ClassIR, FuncIR, Record
 
+HAVE_TEST = False
 if sys.version_info >= (3, 14):
-    from test.support import EqualToForwardRef
-    type_forward_ref = EqualToForwardRef
-else:
+    try:
+        from test.support import EqualToForwardRef
+        type_forward_ref = EqualToForwardRef
+        HAVE_TEST = True
+    except ImportError as e:
+        # catch the case of a pymanager installed Python
+        # without the test module. It is excluded by default
+        # on Windows.
+        msg = 'Missing "test" module.'
+        if sys.platform == "win32":
+            msg += (' Please install a version of Python with the test module.'
+                   ' If you are using pymanager, try running pymanager install --force PythonTest\\<version>')
+        raise ImportError(msg) from e
+
+if not HAVE_TEST:
     from typing import ForwardRef
     type_forward_ref = ForwardRef
 
@@ -203,6 +216,22 @@ def f7(x: List[Tuple[int, int]]) -> int:
 def test_unbox_tuple() -> None:
     assert f7([(5, 6)]) == 11
 
+def test_comparison() -> None:
+    assert ('x','y') == ('x','y')
+    assert not(('x','y') != ('x','y'))
+
+    assert ('x','y') != ('x','y',1)
+    assert not(('x','y') == ('x','y',1))
+
+    assert ('x','y',1) != ('x','y')
+    assert not(('x','y',1) == ('x','y'))
+
+    assert ('x','y') != ()
+    assert not(('x','y') == ())
+
+    assert () != ('x','y')
+    assert not(() == ('x','y'))
+
 # Test that order is irrelevant to unions. Really I only care that this builds.
 
 class A:
@@ -263,6 +292,89 @@ TUPLE: Final[Tuple[str, ...]] = ('x', 'y')
 def test_final_boxed_tuple() -> None:
     t = TUPLE
     assert t == ('x', 'y')
+    assert 'x' in TUPLE
+    assert 'y' in TUPLE
+    b: object = 'z' in TUPLE
+    assert not b
+    assert 'z' not in TUPLE
+    b2: object = 'x' not in TUPLE
+    assert not b2
+    b3: object = 'y' not in TUPLE
+    assert not b3
+
+TUP2: Final = ('x', 'y')
+TUP1: Final = ('x',)
+TUP0: Final = ()
+
+def test_final_tuple_in() -> None:
+    assert 'x' + str() in TUP2
+    assert 'y' + str() in TUP2
+    b: object = 'z' + str() in TUP2
+    assert not b
+
+    assert 'x' + str() in TUP1
+    b2: object = 'y' in TUP1
+    assert not b2
+
+    b3: object = 'x' in TUP0
+    assert not b3
+
+def test_final_tuple_not_in() -> None:
+    assert 'z' + str() not in TUP2
+    b: object = 'x' + str() not in TUP2
+    assert not b
+    b2: object = 'y' + str() not in TUP2
+    assert not b2
+
+    assert 'y' + str() not in TUP1
+    b3: object = 'x' not in TUP1
+    assert not b2
+
+    assert 'x' not in TUP0
+
+log = []
+
+def f_a() -> str:
+    log.append('f_a')
+    return 'a'
+
+def f_a2() -> str:
+    log.append('f_a2')
+    return 'a'
+
+def f_b() -> str:
+    log.append('f_b')
+    return 'b'
+
+def f_c() -> str:
+    log.append('f_c')
+    return 'c'
+
+def test_tuple_in_order_of_evaluation() -> None:
+    log.clear()
+    assert f_a() in (f_b(), f_a2())
+    assert log ==["f_a", "f_b", "f_a2"]
+
+    log.clear()
+    assert f_a() not in (f_b(), f_c())
+    assert log ==["f_a", "f_b", "f_c"]
+
+    log.clear()
+    assert f_a() in (f_b(), f_a2(), f_c())
+    assert log ==["f_a", "f_b", "f_a2", "f_c"]
+
+def f_t() -> tuple[str, ...]:
+    log.append('f_t')
+    return ('x', 'a')
+
+def test_tuple_in_non_specialized() -> None:
+    log.clear()
+    assert f_a() in f_t()
+    assert log == ["f_a", "f_t"]
+
+    log.clear()
+    assert f_b() not in f_t()
+    assert log == ["f_b", "f_t"]
 
 def test_add() -> None:
     res = (1, 2, 3, 4)
@@ -278,3 +390,35 @@ def test_multiply() -> None:
     assert (1,) * 3 == res
     assert 3 * (1,) == res
     assert multiply((1,), 3) == res
+
+[case testIsInstance]
+from copysubclass import subc
+def test_built_in() -> None:
+    assert isinstance((), tuple)
+    assert isinstance((1, 2), tuple)
+    assert isinstance(('a', 'b', 'c'), tuple)
+    assert isinstance(subc(()), tuple)
+    assert isinstance(subc((1, 2)), tuple)
+    assert isinstance(subc(('a', 'b', 'c')), tuple)
+
+    assert not isinstance(set(), tuple)
+    assert not isinstance({}, tuple)
+    assert not isinstance([1,2,3], tuple)
+    assert not isinstance({'a','b'}, tuple)
+    assert not isinstance(int() + 1, tuple)
+    assert not isinstance(str() + 'a', tuple)
+
+def test_user_defined() -> None:
+    from userdefinedtuple import tuple
+
+    assert isinstance(tuple(), tuple)
+    assert not isinstance((1, tuple()), tuple)
+
+[file copysubclass.py]
+from typing import Any
+class subc(tuple[Any]):
+    pass
+
+[file userdefinedtuple.py]
+class tuple:
+    pass
diff --git a/mypyc/test-data/run-weakref.test b/mypyc/test-data/run-weakref.test
new file mode 100644
index 000000000000..0a0e180d635d
--- /dev/null
+++ b/mypyc/test-data/run-weakref.test
@@ -0,0 +1,52 @@
+# Test cases for weakrefs (compile and run)
+
+[case testWeakrefRef]
+# mypy: disable-error-code="union-attr"
+from weakref import proxy, ref
+from mypy_extensions import mypyc_attr
+from testutil import assertRaises
+from typing import Optional
+
+@mypyc_attr(native_class=False)
+class Object:
+    """some random weakreffable object"""
+    def some_meth(self) -> int:
+        return 1
+
+_callback_called_cache = {"ref": False, "proxy": False}
+
+def test_weakref_ref() -> None:
+    obj: Optional[Object] = Object()
+    r = ref(obj)
+    assert r() is obj
+    obj = None
+    assert r() is None, r()
+
+def test_weakref_ref_with_callback() -> None:
+    obj: Optional[Object] = Object()
+    r = ref(obj, lambda x: _callback_called_cache.__setitem__("ref", True))
+    assert r() is obj
+    obj = None
+    assert r() is None, r()
+    assert _callback_called_cache["ref"] is True
+
+def test_weakref_proxy() -> None:
+    obj: Optional[Object] = Object()
+    p = proxy(obj)
+    assert obj.some_meth() == 1
+    assert p.some_meth() == 1
+    obj.some_meth()
+    obj = None
+    with assertRaises(ReferenceError):
+        p.some_meth()
+
+def test_weakref_proxy_with_callback() -> None:
+    obj: Optional[Object] = Object()
+    p = proxy(obj, lambda x: _callback_called_cache.__setitem__("proxy", True))
+    assert obj.some_meth() == 1
+    assert p.some_meth() == 1
+    obj.some_meth()
+    obj = None
+    with assertRaises(ReferenceError):
+        p.some_meth()
+    assert _callback_called_cache["proxy"] is True
diff --git a/mypyc/test/test_cheader.py b/mypyc/test/test_cheader.py
index 7ab055c735ad..ec9e2c4cf450 100644
--- a/mypyc/test/test_cheader.py
+++ b/mypyc/test/test_cheader.py
@@ -7,7 +7,6 @@
 import re
 import unittest
 
-from mypyc.ir.ops import PrimitiveDescription
 from mypyc.primitives import registry
 
 
@@ -32,8 +31,6 @@ def check_name(name: str) -> None:
             registry.function_ops.values(),
         ]:
             for ops in values:
-                if isinstance(ops, PrimitiveDescription):
-                    ops = [ops]
                 for op in ops:
                     if op.c_function_name is not None:
                         check_name(op.c_function_name)
diff --git a/mypyc/test/test_emitfunc.py b/mypyc/test/test_emitfunc.py
index 275e8c383a4b..6382271cfe94 100644
--- a/mypyc/test/test_emitfunc.py
+++ b/mypyc/test/test_emitfunc.py
@@ -19,6 +19,7 @@
     CallC,
     Cast,
     ComparisonOp,
+    CString,
     DecRef,
     Extend,
     GetAttr,
@@ -34,9 +35,11 @@
     Register,
     Return,
     SetAttr,
+    SetElement,
     SetMem,
     TupleGet,
     Unbox,
+    Undef,
     Unreachable,
     Value,
 )
@@ -49,6 +52,7 @@
     RType,
     bool_rprimitive,
     c_int_rprimitive,
+    cstring_rprimitive,
     dict_rprimitive,
     int32_rprimitive,
     int64_rprimitive,
@@ -111,6 +115,7 @@ def add_local(name: str, rtype: RType) -> Register:
             "y": int_rprimitive,
             "i1": int64_rprimitive,
             "i2": int32_rprimitive,
+            "t": RTuple([object_rprimitive, object_rprimitive]),
         }
         ir.bitmap_attrs = ["i1", "i2"]
         compute_vtable(ir)
@@ -118,6 +123,11 @@ def add_local(name: str, rtype: RType) -> Register:
         self.r = add_local("r", RInstance(ir))
         self.none = add_local("none", none_rprimitive)
 
+        self.struct_type = RStruct(
+            "Foo", ["b", "x", "y"], [bool_rprimitive, int32_rprimitive, int64_rprimitive]
+        )
+        self.st = add_local("st", self.struct_type)
+
         self.context = EmitterContext(NameGenerator([["mod"]]))
 
     def test_goto(self) -> None:
@@ -418,6 +428,17 @@ def test_get_attr_with_bitmap(self) -> None:
             """,
         )
 
+    def test_get_attr_nullable_with_tuple(self) -> None:
+        self.assert_emit(
+            GetAttr(self.r, "t", 1, allow_error_value=True),
+            """cpy_r_r0 = ((mod___AObject *)cpy_r_r)->_t;
+               if (cpy_r_r0.f0 != NULL) {
+                   CPy_INCREF(cpy_r_r0.f0);
+                   CPy_INCREF(cpy_r_r0.f1);
+               }
+            """,
+        )
+
     def test_set_attr(self) -> None:
         self.assert_emit(
             SetAttr(self.r, "y", self.m, 1),
@@ -660,6 +681,17 @@ def test_get_element_ptr(self) -> None:
             GetElementPtr(self.o, r, "i64"), """cpy_r_r0 = (CPyPtr)&((Foo *)cpy_r_o)->i64;"""
         )
 
+    def test_set_element(self) -> None:
+        # Use compact syntax when setting the initial element of an undefined value
+        self.assert_emit(
+            SetElement(Undef(self.struct_type), "b", self.b), """cpy_r_r0.b = cpy_r_b;"""
+        )
+        # We propagate the unchanged values in subsequent assignments
+        self.assert_emit(
+            SetElement(self.st, "x", self.i32),
+            """cpy_r_r0 = (Foo) { cpy_r_st.b, cpy_r_i32, cpy_r_st.y };""",
+        )
+
     def test_load_address(self) -> None:
         self.assert_emit(
             LoadAddress(object_rprimitive, "PyDict_Type"),
@@ -824,6 +856,30 @@ def test_inc_ref_int_literal(self) -> None:
             b = LoadLiteral(x, object_rprimitive)
             self.assert_emit([b, IncRef(b)], "CPy_INCREF(cpy_r_r0);")
 
+    def test_c_string(self) -> None:
+        s = Register(cstring_rprimitive, "s")
+        self.assert_emit(Assign(s, CString(b"foo")), """cpy_r_s = "foo";""")
+        self.assert_emit(Assign(s, CString(b'foo "o')), r"""cpy_r_s = "foo \"o";""")
+        self.assert_emit(Assign(s, CString(b"\x00")), r"""cpy_r_s = "\x00";""")
+        self.assert_emit(Assign(s, CString(b"\\")), r"""cpy_r_s = "\\";""")
+        for i in range(256):
+            b = bytes([i])
+            if b == b"\n":
+                target = "\\n"
+            elif b == b"\r":
+                target = "\\r"
+            elif b == b"\t":
+                target = "\\t"
+            elif b == b'"':
+                target = '\\"'
+            elif b == b"\\":
+                target = "\\\\"
+            elif i < 32 or i >= 127:
+                target = "\\x%.2x" % i
+            else:
+                target = b.decode("ascii")
+            self.assert_emit(Assign(s, CString(b)), f'cpy_r_s = "{target}";')
+
     def assert_emit(
         self,
         op: Op | list[Op],
diff --git a/mypyc/test/test_external.py b/mypyc/test/test_external.py
index 010c74dee42e..a416cf2ee130 100644
--- a/mypyc/test/test_external.py
+++ b/mypyc/test/test_external.py
@@ -34,6 +34,7 @@ def test_c_unit_test(self) -> None:
                     "build_ext",
                     f"--build-lib={tmpdir}",
                     f"--build-temp={tmpdir}",
+                    "--run-capi-tests",
                 ],
                 env=env,
                 cwd=os.path.join(base_dir, "mypyc", "lib-rt"),
diff --git a/mypyc/test/test_irbuild.py b/mypyc/test/test_irbuild.py
index 9c0ad06416a7..e79cbec392f4 100644
--- a/mypyc/test/test_irbuild.py
+++ b/mypyc/test/test_irbuild.py
@@ -8,7 +8,7 @@
 from mypy.errors import CompileError
 from mypy.test.config import test_temp_dir
 from mypy.test.data import DataDrivenTestCase
-from mypyc.common import TOP_LEVEL_NAME
+from mypyc.common import IS_FREE_THREADED, TOP_LEVEL_NAME
 from mypyc.ir.pprint import format_func
 from mypyc.test.testutil import (
     ICODE_GEN_BUILTINS,
@@ -53,6 +53,7 @@
     "irbuild-constant-fold.test",
     "irbuild-glue-methods.test",
     "irbuild-math.test",
+    "irbuild-weakref.test",
 ]
 
 if sys.version_info >= (3, 10):
@@ -70,6 +71,9 @@ def run_case(self, testcase: DataDrivenTestCase) -> None:
         if options is None:
             # Skipped test case
             return
+        if "_withgil" in testcase.name and IS_FREE_THREADED:
+            # Test case should only run on a non-free-threaded build.
+            return
         with use_custom_builtins(os.path.join(self.data_prefix, ICODE_GEN_BUILTINS), testcase):
             expected_output = remove_comment_lines(testcase.output)
             expected_output = replace_word_size(expected_output)
diff --git a/mypyc/test/test_run.py b/mypyc/test/test_run.py
index b96c4241f30d..172a1016dd91 100644
--- a/mypyc/test/test_run.py
+++ b/mypyc/test/test_run.py
@@ -69,6 +69,8 @@
     "run-dunders-special.test",
     "run-singledispatch.test",
     "run-attrs.test",
+    "run-signatures.test",
+    "run-weakref.test",
     "run-python37.test",
     "run-python38.test",
 ]
@@ -84,7 +86,7 @@
 
 setup(name='test_run_output',
       ext_modules=mypycify({}, separate={}, skip_cgen_input={!r}, strip_asserts=False,
-                           multi_file={}, opt_level='{}'),
+                           multi_file={}, opt_level='{}', install_native_libs={}),
 )
 """
 
@@ -237,11 +239,13 @@ def run_case_step(self, testcase: DataDrivenTestCase, incremental_step: int) ->
 
         groups = construct_groups(sources, separate, len(module_names) > 1, None)
 
+        native_libs = "_native_libs" in testcase.name
         try:
             compiler_options = CompilerOptions(
                 multi_file=self.multi_file,
                 separate=self.separate,
                 strict_dunder_typing=self.strict_dunder_typing,
+                depends_on_native_internal=native_libs,
             )
             result = emitmodule.parse_and_typecheck(
                 sources=sources,
@@ -268,14 +272,13 @@ def run_case_step(self, testcase: DataDrivenTestCase, incremental_step: int) ->
             check_serialization_roundtrip(ir)
 
         opt_level = int(os.environ.get("MYPYC_OPT_LEVEL", 0))
-        debug_level = int(os.environ.get("MYPYC_DEBUG_LEVEL", 0))
 
         setup_file = os.path.abspath(os.path.join(WORKDIR, "setup.py"))
         # We pass the C file information to the build script via setup.py unfortunately
         with open(setup_file, "w", encoding="utf-8") as f:
             f.write(
                 setup_format.format(
-                    module_paths, separate, cfiles, self.multi_file, opt_level, debug_level
+                    module_paths, separate, cfiles, self.multi_file, opt_level, native_libs
                 )
             )
 
diff --git a/mypyc/transform/ir_transform.py b/mypyc/transform/ir_transform.py
index 326a5baca1e7..bcb6db9b0daf 100644
--- a/mypyc/transform/ir_transform.py
+++ b/mypyc/transform/ir_transform.py
@@ -39,6 +39,7 @@
     RaiseStandardError,
     Return,
     SetAttr,
+    SetElement,
     SetMem,
     Truncate,
     TupleGet,
@@ -214,6 +215,9 @@ def visit_set_mem(self, op: SetMem) -> Value | None:
     def visit_get_element_ptr(self, op: GetElementPtr) -> Value | None:
         return self.add(op)
 
+    def visit_set_element(self, op: SetElement) -> Value | None:
+        return self.add(op)
+
     def visit_load_address(self, op: LoadAddress) -> Value | None:
         return self.add(op)
 
@@ -354,10 +358,13 @@ def visit_set_mem(self, op: SetMem) -> None:
     def visit_get_element_ptr(self, op: GetElementPtr) -> None:
         op.src = self.fix_op(op.src)
 
+    def visit_set_element(self, op: SetElement) -> None:
+        op.src = self.fix_op(op.src)
+
     def visit_load_address(self, op: LoadAddress) -> None:
         if isinstance(op.src, LoadStatic):
             new = self.fix_op(op.src)
-            assert isinstance(new, LoadStatic)
+            assert isinstance(new, LoadStatic), new
             op.src = new
 
     def visit_keep_alive(self, op: KeepAlive) -> None:
diff --git a/mypyc/transform/log_trace.py b/mypyc/transform/log_trace.py
new file mode 100644
index 000000000000..cec76b9b4f88
--- /dev/null
+++ b/mypyc/transform/log_trace.py
@@ -0,0 +1,158 @@
+"""This optional pass adds logging of various executed operations.
+
+Some subset of the executed operations are logged to the mypyc_trace.txt file.
+
+This is useful for performance analysis. For example, it's possible
+to identify how frequently various primitive functions are called,
+and in which code locations they are called.
+"""
+
+from __future__ import annotations
+
+from typing import Final
+
+from mypyc.ir.func_ir import FuncIR
+from mypyc.ir.ops import (
+    Box,
+    Call,
+    CallC,
+    Cast,
+    CString,
+    DecRef,
+    GetAttr,
+    IncRef,
+    LoadLiteral,
+    LoadStatic,
+    Op,
+    PrimitiveOp,
+    SetAttr,
+    Unbox,
+    Value,
+)
+from mypyc.ir.rtypes import none_rprimitive
+from mypyc.irbuild.ll_builder import LowLevelIRBuilder
+from mypyc.options import CompilerOptions
+from mypyc.primitives.misc_ops import log_trace_event
+from mypyc.transform.ir_transform import IRTransform
+
+
+def insert_event_trace_logging(fn: FuncIR, options: CompilerOptions) -> None:
+    builder = LowLevelIRBuilder(None, options)
+    transform = LogTraceEventTransform(builder, fn.decl.fullname)
+    transform.transform_blocks(fn.blocks)
+    fn.blocks = builder.blocks
+
+
+def get_load_global_name(op: CallC) -> str | None:
+    name = op.function_name
+    if name == "CPyDict_GetItem":
+        arg = op.args[0]
+        if (
+            isinstance(arg, LoadStatic)
+            and arg.namespace == "static"
+            and arg.identifier == "globals"
+            and isinstance(op.args[1], LoadLiteral)
+        ):
+            return str(op.args[1].value)
+    return None
+
+
+# These primitives perform an implicit IncRef for the return value. Only some of the most common ones
+# are included, and mostly ops that could be switched to use borrowing in some contexts.
+primitives_that_inc_ref: Final = {
+    "list_get_item_unsafe",
+    "CPyList_GetItemShort",
+    "CPyDict_GetWithNone",
+    "CPyList_GetItem",
+    "CPyDict_GetItem",
+    "CPyList_PopLast",
+}
+
+
+class LogTraceEventTransform(IRTransform):
+    def __init__(self, builder: LowLevelIRBuilder, fullname: str) -> None:
+        super().__init__(builder)
+        self.fullname = fullname.encode("utf-8")
+
+    def visit_call(self, op: Call) -> Value:
+        # TODO: Use different op name when constructing an instance
+        return self.log(op, "call", op.fn.fullname)
+
+    def visit_primitive_op(self, op: PrimitiveOp) -> Value:
+        value = self.log(op, "primitive_op", op.desc.name)
+        if op.desc.name in primitives_that_inc_ref:
+            self.log_inc_ref(value)
+        return value
+
+    def visit_call_c(self, op: CallC) -> Value:
+        if global_name := get_load_global_name(op):
+            return self.log(op, "globals_dict_get_item", global_name)
+
+        func_name = op.function_name
+        if func_name == "PyObject_Vectorcall" and isinstance(op.args[0], CallC):
+            if global_name := get_load_global_name(op.args[0]):
+                return self.log(op, "python_call_global", global_name)
+        elif func_name == "CPyObject_GetAttr" and isinstance(op.args[1], LoadLiteral):
+            return self.log(op, "python_get_attr", str(op.args[1].value))
+        elif func_name == "PyObject_VectorcallMethod" and isinstance(op.args[0], LoadLiteral):
+            return self.log(op, "python_call_method", str(op.args[0].value))
+
+        value = self.log(op, "call_c", func_name)
+        if func_name in primitives_that_inc_ref:
+            self.log_inc_ref(value)
+        return value
+
+    def visit_get_attr(self, op: GetAttr) -> Value:
+        value = self.log(op, "get_attr", f"{op.class_type.name}.{op.attr}")
+        if not op.is_borrowed and op.type.is_refcounted:
+            self.log_inc_ref(op)
+        return value
+
+    def visit_set_attr(self, op: SetAttr) -> Value:
+        name = "set_attr" if not op.is_init else "set_attr_init"
+        return self.log(op, name, f"{op.class_type.name}.{op.attr}")
+
+    def visit_box(self, op: Box) -> Value:
+        if op.src.type is none_rprimitive:
+            # Boxing 'None' is a very quick operation, so we don't log it.
+            return self.add(op)
+        else:
+            return self.log(op, "box", str(op.src.type))
+
+    def visit_unbox(self, op: Unbox) -> Value:
+        return self.log(op, "unbox", str(op.type))
+
+    def visit_cast(self, op: Cast) -> Value | None:
+        value = self.log(op, "cast", str(op.type))
+        if not op.is_borrowed:
+            self.log_inc_ref(value)
+        return value
+
+    def visit_inc_ref(self, op: IncRef) -> Value:
+        return self.log(op, "inc_ref", str(op.src.type))
+
+    def visit_dec_ref(self, op: DecRef) -> Value:
+        return self.log(op, "dec_ref", str(op.src.type))
+
+    def log_inc_ref(self, value: Value) -> None:
+        self.log_event("inc_ref", str(value.type), value.line)
+
+    def log(self, op: Op, name: str, details: str) -> Value:
+        self.log_event(name, details, op.line)
+        return self.add(op)
+
+    def log_event(self, name: str, details: str, line: int) -> None:
+        if line >= 0:
+            line_str = str(line)
+        else:
+            line_str = ""
+        self.builder.primitive_op(
+            log_trace_event,
+            [
+                CString(self.fullname),
+                CString(line_str.encode("ascii")),
+                CString(name.encode("utf-8")),
+                CString(details.encode("utf-8")),
+            ],
+            line,
+        )
diff --git a/mypyc/transform/refcount.py b/mypyc/transform/refcount.py
index b2ca03d44630..60daebc415fd 100644
--- a/mypyc/transform/refcount.py
+++ b/mypyc/transform/refcount.py
@@ -43,6 +43,7 @@
     Op,
     Register,
     RegisterOp,
+    Undef,
     Value,
 )
 
@@ -94,7 +95,7 @@ def is_maybe_undefined(post_must_defined: set[Value], src: Value) -> bool:
 def maybe_append_dec_ref(
     ops: list[Op], dest: Value, defined: AnalysisDict[Value], key: tuple[BasicBlock, int]
 ) -> None:
-    if dest.type.is_refcounted and not isinstance(dest, Integer):
+    if dest.type.is_refcounted and not isinstance(dest, (Integer, Undef)):
         ops.append(DecRef(dest, is_xdec=is_maybe_undefined(defined[key], dest)))
 
 
@@ -127,7 +128,7 @@ def transform_block(
                 # For assignments to registers that were already live,
                 # decref the old value.
                 if dest not in pre_borrow[key] and dest in pre_live[key]:
-                    assert isinstance(op, Assign)
+                    assert isinstance(op, Assign), op
                     maybe_append_dec_ref(ops, dest, post_must_defined, key)
 
         # Strip KeepAlive. Its only purpose is to help with this transform.
diff --git a/pyproject.toml b/pyproject.toml
index 1870e0931407..032bfcb609e7 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -222,6 +222,14 @@ addopts = "-nauto --strict-markers --strict-config"
 # treat xpasses as test failures so they get converted to regular tests as soon as possible
 xfail_strict = true
 
+# Force warnings as errors
+filterwarnings = [
+  "error",
+  # Some testcases may contain code that emits SyntaxWarnings, and they are not yet
+  # handled consistently in 3.14 (PEP 765)
+  "default::SyntaxWarning",
+]
+
 [tool.coverage.run]
 branch = true
 source = ["mypy"]
diff --git a/setup.py b/setup.py
index 12cc1aad4d72..798ff4f6c710 100644
--- a/setup.py
+++ b/setup.py
@@ -145,6 +145,7 @@ def run(self) -> None:
     opt_level = os.getenv("MYPYC_OPT_LEVEL", "3")
     debug_level = os.getenv("MYPYC_DEBUG_LEVEL", "1")
     force_multifile = os.getenv("MYPYC_MULTI_FILE", "") == "1"
+    log_trace = bool(int(os.getenv("MYPYC_LOG_TRACE", "0")))
     ext_modules = mypycify(
         mypyc_targets + ["--config-file=mypy_bootstrap.ini"],
         opt_level=opt_level,
@@ -152,6 +153,11 @@ def run(self) -> None:
         # Use multi-file compilation mode on windows because without it
         # our Appveyor builds run out of memory sometimes.
         multi_file=sys.platform == "win32" or force_multifile,
+        log_trace=log_trace,
+        # Mypy itself is allowed to use native_internal extension.
+        depends_on_native_internal=True,
+        # TODO: temporary, remove this after we publish mypy-native on PyPI.
+        install_native_libs=True,
     )
 
 else:
diff --git a/test-data/unit/check-abstract.test b/test-data/unit/check-abstract.test
index 2fed3425c8d4..7507a31d115a 100644
--- a/test-data/unit/check-abstract.test
+++ b/test-data/unit/check-abstract.test
@@ -571,8 +571,12 @@ from abc import abstractmethod, ABCMeta
 import typing
 
 class A(metaclass=ABCMeta): pass
-class B(object, A): pass \
-      # E: Cannot determine consistent method resolution order (MRO) for "B"
+class B(object, A, metaclass=ABCMeta): # E: Cannot determine consistent method resolution order (MRO) for "B"
+    pass
+
+class C(object, A):  # E: Cannot determine consistent method resolution order (MRO) for "C" \
+                     # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases
+    pass
 
 [case testOverloadedAbstractMethod]
 from foo import *
diff --git a/test-data/unit/check-callable.test b/test-data/unit/check-callable.test
index 39e6c4fa3ff1..23db0bf50a4e 100644
--- a/test-data/unit/check-callable.test
+++ b/test-data/unit/check-callable.test
@@ -587,6 +587,54 @@ class C(B):
 class B: ...
 [builtins fixtures/classmethod.pyi]
 
+[case testClassMethodAliasInClass]
+from typing import overload
+
+class C:
+    @classmethod
+    def foo(cls) -> int: ...
+
+    bar = foo
+
+    @overload
+    @classmethod
+    def foo2(cls, x: int) -> int: ...
+    @overload
+    @classmethod
+    def foo2(cls, x: str) -> str: ...
+    @classmethod
+    def foo2(cls, x):
+        ...
+
+    bar2 = foo2
+
+reveal_type(C.bar)  # N: Revealed type is "def () -> builtins.int"
+reveal_type(C().bar)  # N: Revealed type is "def () -> builtins.int"
+reveal_type(C.bar2)  # N: Revealed type is "Overload(def (x: builtins.int) -> builtins.int, def (x: builtins.str) -> builtins.str)"
+reveal_type(C().bar2)  # N: Revealed type is "Overload(def (x: builtins.int) -> builtins.int, def (x: builtins.str) -> builtins.str)"
+[builtins fixtures/classmethod.pyi]
+
+[case testPropertyAliasInClassBody]
+class A:
+    @property
+    def f(self) -> int: ...
+
+    g = f
+
+    @property
+    def f2(self) -> int: ...
+    @f2.setter
+    def f2(self, val: int) -> None: ...
+
+    g2 = f2
+
+reveal_type(A().g)  # N: Revealed type is "builtins.int"
+reveal_type(A().g2)  # N: Revealed type is "builtins.int"
+A().g = 1  # E: Property "g" defined in "A" is read-only
+A().g2 = 1
+A().g2 = "no"  # E: Incompatible types in assignment (expression has type "str", variable has type "int")
+[builtins fixtures/property.pyi]
+
 [case testCallableUnionCallback]
 from typing import Union, Callable, TypeVar
 
diff --git a/test-data/unit/check-classes.test b/test-data/unit/check-classes.test
index f4bbaf41dc47..498a2c12b6e8 100644
--- a/test-data/unit/check-classes.test
+++ b/test-data/unit/check-classes.test
@@ -772,7 +772,7 @@ class A:
 class B(A):
     @property
     def f(self) -> Callable[[object], None]: pass
-    @func.setter
+    @f.setter
     def f(self, x: object) -> None: pass
 [builtins fixtures/property.pyi]
 
@@ -786,7 +786,7 @@ class A:
 class B(A):
     @property
     def f(self) -> Callable[[object], None]: pass
-    @func.setter
+    @f.setter
     def f(self, x: object) -> None: pass
 [builtins fixtures/property.pyi]
 
@@ -1622,7 +1622,81 @@ class A:
         self.x = '' # E: Incompatible types in assignment (expression has type "str", variable has type "int")
         return ''
 [builtins fixtures/property.pyi]
+
+[case testPropertyNameIsChecked]
+class A:
+    @property
+    def f(self) -> str: ...
+    @not_f.setter  # E: Only supported top decorators are "@f.setter" and "@f.deleter"
+    def f(self, val: str) -> None: ...
+
+a = A()
+reveal_type(a.f)  # N: Revealed type is "builtins.str"
+a.f = ''  # E: Property "f" defined in "A" is read-only
+
+class B:
+    @property
+    def f(self) -> str: ...
+    @not_f.deleter  # E: Only supported top decorators are "@f.setter" and "@f.deleter"
+    def f(self) -> None: ...
+
+class C:
+    @property
+    def f(self) -> str: ...
+    @not_f.setter  # E: Only supported top decorators are "@f.setter" and "@f.deleter"
+    def f(self, val: str) -> None: ...
+    @not_f.deleter  # E: Only supported top decorators are "@f.setter" and "@f.deleter"
+    def f(self) -> None: ...
+[builtins fixtures/property.pyi]
+
+[case testPropertyAttributeIsChecked]
+class A:
+    @property
+    def f(self) -> str: ...
+    @f.unknown  # E: Only supported top decorators are "@f.setter" and "@f.deleter"
+    def f(self, val: str) -> None: ...
+    @f.bad.setter  # E: Only supported top decorators are "@f.setter" and "@f.deleter"
+    def f(self, val: str) -> None: ...
+    @f  # E: Only supported top decorators are "@f.setter" and "@f.deleter"
+    def f(self, val: str) -> None: ...
+    @int  # E: Only supported top decorators are "@f.setter" and "@f.deleter"
+    def f(self, val: str) -> None: ...
+[builtins fixtures/property.pyi]
+
+[case testPropertyNameAndAttributeIsCheckedPretty]
+# flags: --pretty
+class A:
+    @property
+    def f(self) -> str: ...
+    @not_f.setter
+    def f(self, val: str) -> None: ...
+    @not_f.deleter
+    def f(self) -> None: ...
+
+class B:
+    @property
+    def f(self) -> str: ...
+    @f.unknown
+    def f(self, val: str) -> None: ...
+[builtins fixtures/property.pyi]
 [out]
+main:5: error: Only supported top decorators are "@f.setter" and "@f.deleter"
+        @not_f.setter
+         ^~~~~~~~~~~~
+main:7: error: Only supported top decorators are "@f.setter" and "@f.deleter"
+        @not_f.deleter
+         ^~~~~~~~~~~~~
+main:13: error: Only supported top decorators are "@f.setter" and "@f.deleter"
+        @f.unknown
+         ^~~~~~~~~
+
+[case testPropertyGetterDecoratorIsRejected]
+class A:
+    @property
+    def f(self) -> str: ...
+    @f.getter  # E: Only supported top decorators are "@f.setter" and "@f.deleter"
+    def f(self, val: str) -> None: ...
+[builtins fixtures/property.pyi]
 
 [case testDynamicallyTypedProperty]
 import typing
@@ -2487,6 +2561,60 @@ reveal_type(Num3() + Num1())  # N: Revealed type is "__main__.Num3"
 reveal_type(Num2() + Num3())  # N: Revealed type is "__main__.Num2"
 reveal_type(Num3() + Num2())  # N: Revealed type is "__main__.Num3"
 
+[case testReverseOperatorWithOverloads3]
+from typing import Union, overload
+
+class A:
+    def __mul__(self, value: A, /) -> A: ...
+    def __rmul__(self, value: A, /) -> A: ...
+
+class B:
+    @overload
+    def __mul__(self, other: B, /) -> B: ...
+    @overload
+    def __mul__(self, other: A, /) -> str: ...
+    def __mul__(self, other: Union[B, A], /) -> Union[B, str]: pass
+
+    @overload
+    def __rmul__(self, other: B, /) -> B: ...
+    @overload
+    def __rmul__(self, other: A, /) -> str: ...
+    def __rmul__(self, other: Union[B, A], /) -> Union[B, str]: pass
+
+[case testReverseOperatorWithOverloadsNested]
+from typing import Union, overload
+
+class A:
+    def __mul__(self, value: A, /) -> A: ...
+    def __rmul__(self, value: A, /) -> A: ...
+
+class B:
+    @overload
+    def __mul__(self, other: B, /) -> B: ...
+    @overload
+    def __mul__(self, other: A, /) -> str: ...
+    def __mul__(self, other: Union[B, A], /) -> Union[B, str]: pass
+
+    @overload
+    def __rmul__(self, other: B, /) -> B: ...
+    @overload
+    def __rmul__(self, other: A, /) -> str: ...
+    def __rmul__(self, other: Union[B, A], /) -> Union[B, str]:
+        class A1:
+            def __add__(self, other: C1) -> int: ...
+
+        class B1:
+            def __add__(self, other: C1) -> int: ...
+
+        class C1:
+            @overload
+            def __radd__(self, other: A1) -> str: ...   # E: Signatures of "__radd__" of "C1" and "__add__" of "A1" are unsafely overlapping
+            @overload
+            def __radd__(self, other: B1) -> str: ...   # E: Signatures of "__radd__" of "C1" and "__add__" of "B1" are unsafely overlapping
+            def __radd__(self, other): pass
+
+        return ""
+
 [case testDivReverseOperator]
 # No error: __div__ has no special meaning in Python 3
 class A1:
@@ -3133,7 +3261,10 @@ b.bad = 'a'  # E: Incompatible types in assignment (expression has type "str", v
 from typing import Any
 
 class Test:
-    def __setattr__() -> None: ...  # E: Method must have at least one argument. Did you forget the "self" argument? # E: Invalid signature "Callable[[], None]" for "__setattr__"
+    def __setattr__() -> None: ... \
+        # E: Invalid signature "Callable[[], None]" for "__setattr__" \
+        # E: Method must have at least one argument. Did you forget the "self" argument?
+
 t = Test()
 t.crash = 'test'  # E: Attribute function "__setattr__" with type "Callable[[], None]" does not accept self argument \
                   # E: "Test" has no attribute "crash"
@@ -4588,6 +4719,23 @@ reveal_type(a.a)  # N: Revealed type is "def (a: builtins.int)"
 reveal_type(a.c)  # N: Revealed type is "def (a: builtins.int)"
 [builtins fixtures/staticmethod.pyi]
 
+[case testClassStaticMethodIndirectOverloaded]
+from typing import overload
+class A:
+    @overload
+    @staticmethod
+    def a(x: int) -> int: ...
+    @overload
+    @staticmethod
+    def a(x: str) -> str: ...
+    @staticmethod
+    def a(x):
+        ...
+    c = a
+reveal_type(A.c)  # N: Revealed type is "Overload(def (x: builtins.int) -> builtins.int, def (x: builtins.str) -> builtins.str)"
+reveal_type(A().c)  # N: Revealed type is "Overload(def (x: builtins.int) -> builtins.int, def (x: builtins.str) -> builtins.str)"
+[builtins fixtures/staticmethod.pyi]
+
 [case testClassStaticMethodSubclassing]
 class A:
     @staticmethod
@@ -4686,8 +4834,8 @@ class C(B):
 class X(type): pass
 class Y(type): pass
 class A(metaclass=X): pass
-class B(A, metaclass=Y): pass  # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases
-
+class B(A, metaclass=Y): pass  # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases \
+                               # N: "__main__.Y" (metaclass of "__main__.B") conflicts with "__main__.X" (metaclass of "__main__.A")
 [case testMetaclassNoTypeReveal]
 class M:
     x = 0  # type: int
@@ -5666,8 +5814,8 @@ def f() -> type: return M
 class C1(six.with_metaclass(M), object): pass  # E: Unsupported dynamic base class "six.with_metaclass"
 class C2(C1, six.with_metaclass(M)): pass  # E: Unsupported dynamic base class "six.with_metaclass"
 class C3(six.with_metaclass(A)): pass  # E: Metaclasses not inheriting from "type" are not supported
-@six.add_metaclass(A)  # E: Metaclasses not inheriting from "type" are not supported  \
-    # E: Argument 1 to "add_metaclass" has incompatible type "type[A]"; expected "type[type]"
+@six.add_metaclass(A)  # E: Metaclasses not inheriting from "type" are not supported \
+                       # E: Argument 1 to "add_metaclass" has incompatible type "type[A]"; expected "type[type]"
 
 class D3(A): pass
 class C4(six.with_metaclass(M), metaclass=M): pass  # E: Multiple metaclass definitions
@@ -5683,8 +5831,10 @@ class CD(six.with_metaclass(M)): pass  # E: Multiple metaclass definitions
 class M1(type): pass
 class Q1(metaclass=M1): pass
 @six.add_metaclass(M)
-class CQA(Q1): pass  # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases
-class CQW(six.with_metaclass(M, Q1)): pass  # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases
+class CQA(Q1): pass  # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases \
+                     # N: "__main__.M" (metaclass of "__main__.CQA") conflicts with "__main__.M1" (metaclass of "__main__.Q1")
+class CQW(six.with_metaclass(M, Q1)): pass  # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases \
+                                            # N: "__main__.M" (metaclass of "__main__.CQW") conflicts with "__main__.M1" (metaclass of "__main__.Q1")
 [builtins fixtures/tuple.pyi]
 
 [case testSixMetaclassAny]
@@ -5802,7 +5952,8 @@ class C5(future.utils.with_metaclass(f())): pass  # E: Dynamic metaclass not sup
 
 class M1(type): pass
 class Q1(metaclass=M1): pass
-class CQW(future.utils.with_metaclass(M, Q1)): pass  # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases
+class CQW(future.utils.with_metaclass(M, Q1)): pass  # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases \
+                                                     # N: "__main__.M" (metaclass of "__main__.CQW") conflicts with "__main__.M1" (metaclass of "__main__.Q1")
 [builtins fixtures/tuple.pyi]
 
 [case testFutureMetaclassAny]
@@ -5933,7 +6084,7 @@ class B(A):
     __slots__ = ('a', 'b')
 class C:
     __slots__ = ('x',)
-class D(B, C):
+class D(B, C):  # E: Class "D" has incompatible disjoint bases
     __slots__ = ('aa', 'bb', 'cc')
 [builtins fixtures/tuple.pyi]
 
@@ -7271,19 +7422,57 @@ class ChildOfCorrectSubclass1(CorrectSubclass1): ...
 class CorrectWithType1(C, A1): ...
 class CorrectWithType2(B, C): ...
 
-class Conflict1(A1, B, E): ...  # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases
-class Conflict2(A, B): ...  # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases
-class Conflict3(B, A): ...  # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases
+class Conflict1(A1, B, E): ...  # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases \
+                                # N: "__main__.MyMeta1" (metaclass of "__main__.A") conflicts with "__main__.MyMeta2" (metaclass of "__main__.B")
+class Conflict2(A, B): ...  # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases \
+                            # N: "__main__.MyMeta1" (metaclass of "__main__.A") conflicts with "__main__.MyMeta2" (metaclass of "__main__.B")
+class Conflict3(B, A): ...  # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases \
+                            # N: "__main__.MyMeta2" (metaclass of "__main__.B") conflicts with "__main__.MyMeta1" (metaclass of "__main__.A")
 
-class ChildOfConflict1(Conflict3): ...  # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases
+class ChildOfConflict1(Conflict3): ...
 class ChildOfConflict2(Conflict3, metaclass=CorrectMeta): ...
 
 class ConflictingMeta(MyMeta1, MyMeta3): ...
-class Conflict4(A1, B, E, metaclass=ConflictingMeta): ...  # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases
+class Conflict4(A1, B, E, metaclass=ConflictingMeta): ...  # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases \
+                                                           # N: "__main__.ConflictingMeta" (metaclass of "__main__.Conflict4") conflicts with "__main__.MyMeta2" (metaclass of "__main__.B")
 
-class ChildOfCorrectButWrongMeta(CorrectSubclass1, metaclass=ConflictingMeta):  # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases
+class ChildOfCorrectButWrongMeta(CorrectSubclass1, metaclass=ConflictingMeta):  # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases \
+                                                                                # N: "__main__.ConflictingMeta" (metaclass of "__main__.ChildOfCorrectButWrongMeta") conflicts with "__main__.CorrectMeta" (metaclass of "__main__.CorrectSubclass1")
     ...
 
+[case testMetaClassConflictIssue14033]
+class M1(type): pass
+class M2(type): pass
+class Mx(M1, M2): pass
+
+class A1(metaclass=M1): pass
+class A2(A1): pass
+
+class B1(metaclass=M2): pass
+
+class C1(metaclass=Mx): pass
+
+class TestABC(A2, B1, C1): pass  # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases \
+                                 # N: "__main__.M1" (metaclass of "__main__.A1") conflicts with "__main__.M2" (metaclass of "__main__.B1")
+class TestBAC(B1, A2, C1): pass  # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases \
+                                 # N: "__main__.M2" (metaclass of "__main__.B1") conflicts with "__main__.M1" (metaclass of "__main__.A1")
+
+# should not warn again for children
+class ChildOfTestABC(TestABC): pass
+
+# no metaclass is assumed if super class has a metaclass conflict
+class ChildOfTestABCMetaMx(TestABC, metaclass=Mx): pass
+class ChildOfTestABCMetaM1(TestABC, metaclass=M1): pass
+
+class TestABCMx(A2, B1, C1, metaclass=Mx): pass
+class TestBACMx(B1, A2, C1, metaclass=Mx): pass
+
+class TestACB(A2, C1, B1): pass
+class TestBCA(B1, C1, A2): pass
+
+class TestCAB(C1, A2, B1): pass
+class TestCBA(C1, B1, A2): pass
+
 [case testGenericOverride]
 from typing import Generic, TypeVar, Any
 
@@ -7556,6 +7745,231 @@ class Foo:
     def bad():  # E: Method must have at least one argument. Did you forget the "self" argument?
         self.x = 0  # E: Name "self" is not defined
 
+[case testMethodSelfArgumentChecks]
+from typing import Callable, ParamSpec, TypeVar
+
+T = TypeVar("T")
+P = ParamSpec("P")
+
+def to_number_1(fn: Callable[[], int]) -> int:
+    return 0
+
+def to_number_2(fn: Callable[[int], int]) -> int:
+    return 0
+
+def to_same_callable(fn: Callable[P, T]) -> Callable[P, T]:
+    return fn
+
+class A:
+    def undecorated() -> None: ...  # E: Method must have at least one argument. Did you forget the "self" argument?
+
+    def undecorated_not_self(x: int) -> None: ...  # E: Self argument missing for a non-static method (or an invalid type for self)
+
+    def undecorated_not_self_2(self: int) -> None: ...  # E: The erased type of self "builtins.int" is not a supertype of its class "__main__.A"
+
+    @to_number_1
+    def fn1() -> int:
+        return 0
+
+    @to_number_1  # E: Argument 1 to "to_number_1" has incompatible type "Callable[[int], int]"; expected "Callable[[], int]"
+    def fn2(_x: int) -> int:
+        return 0
+
+    @to_number_2  # E: Argument 1 to "to_number_2" has incompatible type "Callable[[], int]"; expected "Callable[[int], int]"
+    def fn3() -> int:
+        return 0
+
+    @to_number_2
+    def fn4(_x: int) -> int:
+        return 0
+
+    @to_number_2  # E: Argument 1 to "to_number_2" has incompatible type "Callable[[str], int]"; expected "Callable[[int], int]"
+    def fn5(_x: str) -> int:
+        return 0
+
+    @to_same_callable
+    def g1() -> None: ...  # E: Method must have at least one argument. Did you forget the "self" argument?
+
+    @to_same_callable
+    def g2(x: int) -> None: ...  # E: Self argument missing for a non-static method (or an invalid type for self)
+
+    @to_same_callable
+    def g3(self: int) -> None: ...  # E: The erased type of self "builtins.int" is not a supertype of its class "__main__.A"
+
+reveal_type(A().fn1)  # N: Revealed type is "builtins.int"
+reveal_type(A().fn2)  # N: Revealed type is "builtins.int"
+reveal_type(A().fn3)  # N: Revealed type is "builtins.int"
+reveal_type(A().fn4)  # N: Revealed type is "builtins.int"
+reveal_type(A().fn5)  # N: Revealed type is "builtins.int"
+
+reveal_type(A().g1)  # E: Attribute function "g1" with type "Callable[[], None]" does not accept self argument \
+                     # N: Revealed type is "def ()"
+reveal_type(A().g2)  # E: Invalid self argument "A" to attribute function "g2" with type "Callable[[int], None]" \
+                     # N: Revealed type is "def ()"
+reveal_type(A().g3)  # E: Invalid self argument "A" to attribute function "g3" with type "Callable[[int], None]" \
+                     # N: Revealed type is "def ()"
+[builtins fixtures/tuple.pyi]
+
+[case testMethodSelfArgumentChecksConcatenate]
+from typing import Callable, ParamSpec, TypeVar
+from typing_extensions import Concatenate
+
+T = TypeVar("T")
+P = ParamSpec("P")
+R = TypeVar("R")
+
+def to_same_callable(fn: Callable[Concatenate[T, P], R]) -> Callable[Concatenate[T, P], R]:
+    return fn
+
+def remove_first(fn: Callable[Concatenate[T, P], R]) -> Callable[P, R]:
+    ...
+
+def add_correct_first(fn: Callable[P, R]) -> Callable[Concatenate["C", P], R]:
+    ...
+
+def add_wrong_first(fn: Callable[P, R]) -> Callable[Concatenate[int, P], R]:
+    ...
+
+class A:
+    @to_same_callable  # E: Argument 1 to "to_same_callable" has incompatible type "Callable[[], int]"; expected "Callable[[T], int]"
+    def fn1() -> int:
+        return 0
+
+    @to_same_callable
+    def fn2(_x: int) -> int:  # E: Self argument missing for a non-static method (or an invalid type for self)
+        return 0
+
+    @to_same_callable
+    def fn3(self, _x: int) -> int:
+        return 0
+
+reveal_type(A().fn1)  # N: Revealed type is "def () -> builtins.int"
+reveal_type(A().fn2)  # E: Invalid self argument "A" to attribute function "fn2" with type "Callable[[int], int]" \
+                      # N: Revealed type is "def () -> builtins.int"
+reveal_type(A().fn3)  # N: Revealed type is "def (_x: builtins.int) -> builtins.int"
+
+class B:
+    @remove_first  # E: Argument 1 to "remove_first" has incompatible type "Callable[[], int]"; expected "Callable[[T], int]"
+    def fn1() -> int:  # E: Method must have at least one argument. Did you forget the "self" argument?
+        return 0
+
+    @remove_first
+    def fn2(_x: int) -> int:  # E: Method must have at least one argument. Did you forget the "self" argument?
+        return 0
+
+    @remove_first
+    def fn3(self, _x: int) -> int:  # E: Self argument missing for a non-static method (or an invalid type for self)
+        return 0
+
+    @remove_first
+    def fn4(self, new_self: 'B') -> int:
+        return 0
+
+reveal_type(B().fn1)  # E: Attribute function "fn1" with type "Callable[[], int]" does not accept self argument \
+                      # N: Revealed type is "def () -> builtins.int"
+reveal_type(B().fn2)  # E: Attribute function "fn2" with type "Callable[[], int]" does not accept self argument \
+                      # N: Revealed type is "def () -> builtins.int"
+reveal_type(B().fn3)  # E: Invalid self argument "B" to attribute function "fn3" with type "Callable[[int], int]" \
+                      # N: Revealed type is "def () -> builtins.int"
+reveal_type(B().fn4)  # N: Revealed type is "def () -> builtins.int"
+
+class C:
+    @add_correct_first
+    def fn1() -> int:
+        return 0
+
+    @add_correct_first
+    def fn2(_x: int) -> int:
+        return 0
+
+    @add_correct_first
+    def fn3(self, _x: int) -> int:
+        return 0
+
+reveal_type(C().fn1)  # N: Revealed type is "def () -> builtins.int"
+reveal_type(C().fn2)  # N: Revealed type is "def (_x: builtins.int) -> builtins.int"
+reveal_type(C().fn3)  # N: Revealed type is "def (self: __main__.C, _x: builtins.int) -> builtins.int"
+
+class D:
+    @add_wrong_first
+    def fn1() -> int:  # E: Self argument missing for a non-static method (or an invalid type for self)
+        return 0
+
+    @add_wrong_first
+    def fn2(_x: int) -> int:  # E: Self argument missing for a non-static method (or an invalid type for self)
+        return 0
+
+    @add_wrong_first
+    def fn3(self, _x: int) -> int:  # E: Self argument missing for a non-static method (or an invalid type for self)
+        return 0
+
+reveal_type(D().fn1)  # E: Invalid self argument "D" to attribute function "fn1" with type "Callable[[int], int]" \
+                      # N: Revealed type is "def () -> builtins.int"
+reveal_type(D().fn2)  # E: Invalid self argument "D" to attribute function "fn2" with type "Callable[[int, int], int]" \
+                      # N: Revealed type is "def (_x: builtins.int) -> builtins.int"
+reveal_type(D().fn3)  # E: Invalid self argument "D" to attribute function "fn3" with type "Callable[[int, D, int], int]" \
+                      # N: Revealed type is "def (self: __main__.D, _x: builtins.int) -> builtins.int"
+[builtins fixtures/tuple.pyi]
+
+[case testMethodSelfArgumentChecksInUntyped]
+from typing import Callable, ParamSpec, TypeVar
+
+T = TypeVar("T")
+P = ParamSpec("P")
+
+def to_same_callable(fn: Callable[P, T]) -> Callable[P, T]:
+    return fn
+
+def unchecked():
+    class Bad:
+        def fn() -> None: ...  # E: Method must have at least one argument. Did you forget the "self" argument?
+        def fn2(x: int) -> None: ...  # E: Self argument missing for a non-static method (or an invalid type for self)
+
+        # TODO: would be nice to make this error, but now we see the func
+        # being decorated as Any, not as a callable
+        @to_same_callable
+        def gaaa() -> None: ...
+        @to_same_callable
+        def gaaa2(x: int) -> None: ...
+
+    class Ok:
+        def fn(): ...
+        def fn2(x): ...
+
+        @to_same_callable
+        def g(): ...
+        @to_same_callable
+        def g2(x): ...
+
+def checked() -> None:
+    class Bad:
+        def fn() -> None: ...  # E: Method must have at least one argument. Did you forget the "self" argument?
+        def fn2(x: int) -> None: ...  # E: Self argument missing for a non-static method (or an invalid type for self)
+
+        @to_same_callable
+        def g() -> None: ...  # E: Method must have at least one argument. Did you forget the "self" argument?
+        @to_same_callable
+        def g2(x: int) -> None: ...  # E: Self argument missing for a non-static method (or an invalid type for self)
+
+    class AlsoBad:
+        def fn(): ...  # E: Method must have at least one argument. Did you forget the "self" argument?
+        def fn2(x): ...
+
+        @to_same_callable
+        def g(): ...  # E: Method must have at least one argument. Did you forget the "self" argument?
+        @to_same_callable
+        def g2(x): ...
+
+class Ok:
+    def fn(): ...  # E: Method must have at least one argument. Did you forget the "self" argument?
+    def fn2(x): ...
+
+    @to_same_callable
+    def g(): ...  # E: Method must have at least one argument. Did you forget the "self" argument?
+    @to_same_callable
+    def g2(x): ...
+[builtins fixtures/tuple.pyi]
+
 [case testTypeAfterAttributeAccessWithDisallowAnyExpr]
 # flags: --disallow-any-expr
 
@@ -7627,7 +8041,7 @@ class A:
     def y(self) -> int: ...
     @y.setter
     def y(self, value: int) -> None: ...
-    @dec  # E: Only supported top decorator is @y.setter
+    @dec  # E: Only supported top decorators are "@y.setter" and "@y.deleter"
     def y(self) -> None: ...
 
 reveal_type(A().y)  # N: Revealed type is "builtins.int"
@@ -8779,3 +9193,99 @@ class C:
 C().foo = "no"  # E: Incompatible types in assignment (expression has type "str", variable has type "int")
 C().bar = "fine"
 [builtins fixtures/property.pyi]
+
+[case testCorrectConstructorTypeWithAnyFallback]
+from typing import Generic, TypeVar
+
+class B(Unknown):  # type: ignore
+    def __init__(self) -> None: ...
+class C(B): ...
+
+reveal_type(C)  # N: Revealed type is "def () -> __main__.C"
+
+T = TypeVar("T")
+class BG(Generic[T], Unknown):  # type: ignore
+    def __init__(self) -> None: ...
+class CGI(BG[int]): ...
+class CGT(BG[T]): ...
+
+reveal_type(CGI)  # N: Revealed type is "def () -> __main__.CGI"
+reveal_type(CGT)  # N: Revealed type is "def [T] () -> __main__.CGT[T`1]"
+
+[case testSettablePropertyAlias]
+from typing import Any, TypeVar
+
+class A:
+    @property
+    def prop(self: Any) -> str: ...
+    @prop.setter
+    def prop(self, val: str) -> None: ...
+
+T = TypeVar("T")
+class AT:
+    @property
+    def prop(self: T) -> T: ...
+    @prop.setter
+    def prop(self: T, val: list[T]) -> None: ...
+
+class B:
+    prop: str
+    prop_t: str
+
+class C(B):
+    prop = A.prop
+    prop_t = AT.prop  # E: Incompatible types in assignment (expression has type "C", base class "B" defined the type as "str")
+
+reveal_type(C().prop)  # N: Revealed type is "builtins.str"
+C().prop = "no"  # E: Invalid self argument "C" to attribute function "prop" with type "Callable[[A, str], None]"
+reveal_type(C().prop_t)  # N: Revealed type is "__main__.C"
+C().prop_t = 1  # E: Incompatible types in assignment (expression has type "int", variable has type "list[C]")
+[builtins fixtures/property.pyi]
+
+[case testClassEqDecoratedAbstractNote]
+from abc import abstractmethod
+
+class C:
+    @abstractmethod
+    def __eq__(self, other: C) -> bool: ...
+[builtins fixtures/plugin_attrs.pyi]
+[out]
+main:5: error: Argument 1 of "__eq__" is incompatible with supertype "builtins.object"; supertype defines the argument type as "object"
+main:5: note: This violates the Liskov substitution principle
+main:5: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#incompatible-overrides
+main:5: note: It is recommended for "__eq__" to work with arbitrary objects, for example:
+main:5: note:     def __eq__(self, other: object) -> bool:
+main:5: note:         if not isinstance(other, C):
+main:5: note:             return NotImplemented
+main:5: note:         return <logic to compare two C instances>
+
+[case testLambdaInAttributeCallValue]
+# https://github.com/python/mypy/issues/19632
+import foo
+
+def nop(fn: object) -> foo.Bar:
+    return foo.Bar()
+
+class Bar:
+    foo: foo.Bar = nop(
+        lambda: 0
+    )
+[file foo.py]
+class Bar:
+    ...
+
+[case testConstructorWithoutStrictOptionalNoCache]
+import mod
+a = mod.NT(x=None)  # OK
+
+[file typ.py]
+from typing import NamedTuple, Optional
+NT = NamedTuple("NT", [("x", Optional[str])])
+
+[file mod.py]
+# mypy: no-strict-optional
+from typ import NT
+
+def f() -> NT:
+    return NT(x='')
+[builtins fixtures/tuple.pyi]
diff --git a/test-data/unit/check-classvar.test b/test-data/unit/check-classvar.test
index 63bbd7471bc8..7918ccded2fe 100644
--- a/test-data/unit/check-classvar.test
+++ b/test-data/unit/check-classvar.test
@@ -285,7 +285,7 @@ main:3: error: Cannot assign to class variable "x" via instance
 from typing import ClassVar, Generic, TypeVar
 T = TypeVar('T')
 class A(Generic[T]):
-    x: ClassVar[T]  # E: ClassVar cannot contain type variables
+    x: ClassVar[T]  # Error reported at access site
     @classmethod
     def foo(cls) -> T:
         return cls.x  # OK
@@ -308,7 +308,7 @@ from typing import ClassVar, Generic, Tuple, TypeVar, Union, Type
 T = TypeVar('T')
 U = TypeVar('U')
 class A(Generic[T, U]):
-    x: ClassVar[Union[T, Tuple[U, Type[U]]]]  # E: ClassVar cannot contain type variables
+    x: ClassVar[Union[T, Tuple[U, Type[U]]]]  # Error reported at access site
     @classmethod
     def foo(cls) -> Union[T, Tuple[U, Type[U]]]:
         return cls.x  # OK
@@ -319,7 +319,9 @@ A[int, str].x  # E: Access to generic class variables is ambiguous
 
 class Bad(A[int, str]):
     pass
-Bad.x  # E: Access to generic class variables is ambiguous
+reveal_type(Bad.x)  # E: Access to generic class variables is ambiguous \
+                    # N: Revealed type is "Union[builtins.int, tuple[builtins.str, type[builtins.str]]]"
+reveal_type(Bad().x)  # N: Revealed type is "Union[builtins.int, tuple[builtins.str, type[builtins.str]]]"
 
 class Good(A[int, str]):
     x = 42
@@ -343,3 +345,38 @@ class C:
     g: ClassVar[Union[Callable[[C], int], int]] = f
 
 reveal_type(C().g)  # N: Revealed type is "Union[def () -> builtins.int, builtins.int]"
+
+[case testGenericSubclassAccessNoLeak]
+from typing import ClassVar, Generic, TypeVar
+
+T = TypeVar("T")
+class B(Generic[T]):
+    x: T
+    y: ClassVar[T]
+
+class C(B[T]): ...
+
+reveal_type(C.x)  # E: Access to generic instance variables via class is ambiguous \
+                  # N: Revealed type is "Any"
+reveal_type(C.y)  # E: Access to generic class variables is ambiguous \
+                  # N: Revealed type is "Any"
+
+[case testClassVarBareAnnotation]
+from typing import ClassVar
+
+class C:
+    x: ClassVar = 1
+    y: ClassVar
+
+reveal_type(C.x)  # N: Revealed type is "builtins.int"
+reveal_type(C().x)  # N: Revealed type is "builtins.int"
+reveal_type(C.y)  # N: Revealed type is "Any"
+reveal_type(C().y)  # N: Revealed type is "Any"
+
+[case testClassVarBareAnnotationDisabled]
+# flags: --disallow-any-generics
+from typing import ClassVar
+
+class C:
+    x: ClassVar = 1
+    y: ClassVar  # E: ClassVar without type argument becomes Any
diff --git a/test-data/unit/check-dataclasses.test b/test-data/unit/check-dataclasses.test
index 30d8497c9cd2..f43c49c200c8 100644
--- a/test-data/unit/check-dataclasses.test
+++ b/test-data/unit/check-dataclasses.test
@@ -705,7 +705,7 @@ class A(Generic[T]):
     return self.z  # E: Incompatible return value type (got "list[T]", expected "T")
 
 reveal_type(A)  # N: Revealed type is "def [T] (x: T`1, y: T`1, z: builtins.list[T`1]) -> __main__.A[T`1]"
-A(1, 2, ["a", "b"])  # E: Cannot infer type argument 1 of "A"
+A(1, 2, ["a", "b"])  # E: Cannot infer value of type parameter "T" of "A"
 a = A(1, 2, [1, 2])
 reveal_type(a)  # N: Revealed type is "__main__.A[builtins.int]"
 reveal_type(a.x)  # N: Revealed type is "builtins.int"
@@ -2055,7 +2055,7 @@ from dataclasses import dataclass, replace, InitVar
 from typing import ClassVar
 
 @dataclass
-class A:
+class A:  # N: "replace" of "A" defined here
     x: int
     q: InitVar[int]
     q2: InitVar[int] = 0
@@ -2666,3 +2666,19 @@ class PersonBad(TypedDict):
 class JobBad:
     person: PersonBad = field(default_factory=PersonBad)  # E: Argument "default_factory" to "field" has incompatible type "type[PersonBad]"; expected "Callable[[], PersonBad]"
 [builtins fixtures/dict.pyi]
+
+[case testDataclassInitVarRedefinitionNoCrash]
+# https://github.com/python/mypy/issues/19443
+from dataclasses import InitVar, dataclass
+
+class ClassA:
+    def value(self) -> int:
+        return 0
+
+@dataclass
+class ClassB(ClassA):
+    value: InitVar[int]
+
+    def value(self) -> int:  # E: Name "value" already defined on line 10
+        return 0
+[builtins fixtures/dict.pyi]
diff --git a/test-data/unit/check-deprecated.test b/test-data/unit/check-deprecated.test
index e1173ac425ba..607e9d767956 100644
--- a/test-data/unit/check-deprecated.test
+++ b/test-data/unit/check-deprecated.test
@@ -671,9 +671,11 @@ C().g = "x"  # E: function __main__.C.g is deprecated: use g2 instead \
 [case testDeprecatedDescriptor]
 # flags: --enable-error-code=deprecated
 
-from typing import Any, Optional, Union, overload
+from typing import Any, Generic, Optional, overload, TypeVar, Union
 from typing_extensions import deprecated
 
+T = TypeVar("T")
+
 @deprecated("use E1 instead")
 class D1:
     def __get__(self, obj: Optional[C], objtype: Any) -> Union[D1, int]: ...
@@ -701,10 +703,19 @@ class D3:
     def __set__(self, obj: C, value: str) -> None: ...
     def __set__(self, obj: C, value: Union[int, str]) -> None: ...
 
+class D4(Generic[T]):
+    @overload
+    def __get__(self, obj: None, objtype: Any) -> T: ...
+    @overload
+    @deprecated("deprecated instance access")
+    def __get__(self, obj: C, objtype: Any) -> T: ...
+    def __get__(self, obj: Optional[C], objtype: Any) -> T: ...
+
 class C:
     d1 = D1()  # E: class __main__.D1 is deprecated: use E1 instead
     d2 = D2()
     d3 = D3()
+    d4 = D4[int]()
 
 c: C
 C.d1
@@ -719,15 +730,21 @@ C.d3  # E: overload def (self: __main__.D3, obj: None, objtype: Any) -> __main__
 c.d3  # E: overload def (self: __main__.D3, obj: __main__.C, objtype: Any) -> builtins.int of function __main__.D3.__get__ is deprecated: use E3.__get__ instead
 c.d3 = 1
 c.d3 = "x"  # E: overload def (self: __main__.D3, obj: __main__.C, value: builtins.str) of function __main__.D3.__set__ is deprecated: use E3.__set__ instead
+
+C.d4
+c.d4  # E: overload def (self: __main__.D4[T`1], obj: __main__.C, objtype: Any) -> T`1 of function __main__.D4.__get__ is deprecated: deprecated instance access
 [builtins fixtures/property.pyi]
 
 
 [case testDeprecatedOverloadedFunction]
 # flags: --enable-error-code=deprecated
 
-from typing import Union, overload
+from typing import Any, overload, Union
 from typing_extensions import deprecated
 
+int_or_str: Union[int, str]
+any: Any
+
 @overload
 def f(x: int) -> int: ...
 @overload
@@ -738,6 +755,8 @@ def f(x: Union[int, str]) -> Union[int, str]: ...
 f  # E: function __main__.f is deprecated: use f2 instead
 f(1)  # E: function __main__.f is deprecated: use f2 instead
 f("x")  # E: function __main__.f is deprecated: use f2 instead
+f(int_or_str)  # E: function __main__.f is deprecated: use f2 instead
+f(any)  # E: function __main__.f is deprecated: use f2 instead
 f(1.0)  # E: function __main__.f is deprecated: use f2 instead \
         # E: No overload variant of "f" matches argument type "float" \
         # N: Possible overload variants: \
@@ -754,6 +773,8 @@ def g(x: Union[int, str]) -> Union[int, str]: ...
 g
 g(1)  # E: overload def (x: builtins.int) -> builtins.int of function __main__.g is deprecated: work with str instead
 g("x")
+g(int_or_str)  # E: overload def (x: builtins.int) -> builtins.int of function __main__.g is deprecated: work with str instead
+g(any)
 g(1.0)  # E: No overload variant of "g" matches argument type "float" \
         # N: Possible overload variants: \
         # N:     def g(x: int) -> int \
@@ -769,13 +790,62 @@ def h(x: Union[int, str]) -> Union[int, str]: ...
 h
 h(1)
 h("x")  # E: overload def (x: builtins.str) -> builtins.str of function __main__.h is deprecated: work with int instead
+h(int_or_str)  # E: overload def (x: builtins.str) -> builtins.str of function __main__.h is deprecated: work with int instead
+h(any)
 h(1.0)  # E: No overload variant of "h" matches argument type "float" \
         # N: Possible overload variants: \
         # N:     def h(x: int) -> int \
         # N:     def h(x: str) -> str
 
-[builtins fixtures/tuple.pyi]
+@overload
+def i(x: int) -> int: ...
+@overload
+@deprecated("work with int instead")
+def i(x: str) -> str: ...
+@overload
+def i(x: Any) -> Any: ...
+def i(x: Union[int, str]) -> Union[int, str]: ...
 
+i
+i(1)
+i("x")  # E: overload def (x: builtins.str) -> builtins.str of function __main__.i is deprecated: work with int instead
+i(int_or_str)  # E: overload def (x: builtins.str) -> builtins.str of function __main__.i is deprecated: work with int instead
+i(any)
+i(1.0)
+
+@overload
+def j(x: int) -> int: ...
+@overload
+def j(x: str) -> str: ...
+@overload
+@deprecated("work with int or str instead")
+def j(x: Any) -> Any: ...
+def j(x: Union[int, str]) -> Union[int, str]: ...
+
+j
+j(1)
+j("x")
+j(int_or_str)
+j(any)
+j(1.0)  # E: overload def (x: Any) -> Any of function __main__.j is deprecated: work with int or str instead
+
+@overload
+@deprecated("work with str instead")
+def k(x: int) -> int: ...
+@overload
+def k(x: str) -> str: ...
+@overload
+@deprecated("work with str instead")
+def k(x: object) -> Any: ...
+def k(x: object) -> Union[int, str]: ...
+
+k
+k(1)  # E: overload def (x: builtins.int) -> builtins.int of function __main__.k is deprecated: work with str instead
+k("x")
+k(int_or_str)  # E: overload def (x: builtins.int) -> builtins.int of function __main__.k is deprecated: work with str instead
+k(any)
+k(1.0)  # E: overload def (x: builtins.object) -> Any of function __main__.k is deprecated: work with str instead
+[builtins fixtures/tuple.pyi]
 
 [case testDeprecatedImportedOverloadedFunction]
 # flags: --enable-error-code=deprecated
diff --git a/test-data/unit/check-enum.test b/test-data/unit/check-enum.test
index 1ab8109eda75..3bcf9745a801 100644
--- a/test-data/unit/check-enum.test
+++ b/test-data/unit/check-enum.test
@@ -618,9 +618,8 @@ reveal_type(B.a)        # N: Revealed type is "Literal[__main__.B.a]?"
 reveal_type(A.x.name)   # N: Revealed type is "Literal['x']?"
 reveal_type(B.a.name)   # N: Revealed type is "Literal['a']?"
 
-# TODO: The revealed type should be 'int' here
-reveal_type(A.x.value)  # N: Revealed type is "Any"
-reveal_type(B.a.value)  # N: Revealed type is "Any"
+reveal_type(A.x.value)  # N: Revealed type is "builtins.int"
+reveal_type(B.a.value)  # N: Revealed type is "builtins.int"
 [builtins fixtures/enum.pyi]
 
 [case testAnonymousFunctionalEnum]
@@ -755,12 +754,10 @@ class B2(IntEnum):
 class B3(IntEnum):
     x = 1
 
-# TODO: getting B1.x._value_ and B2.x._value_ to have type 'int' requires a typeshed change
-
 is_x(reveal_type(B1.x.name))    # N: Revealed type is "Literal['x']"
 is_x(reveal_type(B1.x._name_))  # N: Revealed type is "Literal['x']"
 reveal_type(B1.x.value)         # N: Revealed type is "builtins.int"
-reveal_type(B1.x._value_)       # N: Revealed type is "Any"
+reveal_type(B1.x._value_)       # N: Revealed type is "builtins.int"
 is_x(reveal_type(B2.x.name))    # N: Revealed type is "Literal['x']"
 is_x(reveal_type(B2.x._name_))  # N: Revealed type is "Literal['x']"
 reveal_type(B2.x.value)         # N: Revealed type is "builtins.int"
@@ -770,9 +767,6 @@ is_x(reveal_type(B3.x._name_))  # N: Revealed type is "Literal['x']"
 reveal_type(B3.x.value)         # N: Revealed type is "Literal[1]?"
 reveal_type(B3.x._value_)       # N: Revealed type is "Literal[1]?"
 
-# TODO: C1.x.value and C2.x.value should also be of type 'int'
-# This requires either a typeshed change or a plugin refinement
-
 C1 = IntFlag('C1', 'x')
 class C2(IntFlag):
     x = auto()
@@ -781,8 +775,8 @@ class C3(IntFlag):
 
 is_x(reveal_type(C1.x.name))    # N: Revealed type is "Literal['x']"
 is_x(reveal_type(C1.x._name_))  # N: Revealed type is "Literal['x']"
-reveal_type(C1.x.value)         # N: Revealed type is "Any"
-reveal_type(C1.x._value_)       # N: Revealed type is "Any"
+reveal_type(C1.x.value)         # N: Revealed type is "builtins.int"
+reveal_type(C1.x._value_)       # N: Revealed type is "builtins.int"
 is_x(reveal_type(C2.x.name))    # N: Revealed type is "Literal['x']"
 is_x(reveal_type(C2.x._name_))  # N: Revealed type is "Literal['x']"
 reveal_type(C2.x.value)         # N: Revealed type is "builtins.int"
@@ -800,8 +794,8 @@ class D3(Flag):
 
 is_x(reveal_type(D1.x.name))    # N: Revealed type is "Literal['x']"
 is_x(reveal_type(D1.x._name_))  # N: Revealed type is "Literal['x']"
-reveal_type(D1.x.value)         # N: Revealed type is "Any"
-reveal_type(D1.x._value_)       # N: Revealed type is "Any"
+reveal_type(D1.x.value)         # N: Revealed type is "builtins.int"
+reveal_type(D1.x._value_)       # N: Revealed type is "builtins.int"
 is_x(reveal_type(D2.x.name))    # N: Revealed type is "Literal['x']"
 is_x(reveal_type(D2.x._name_))  # N: Revealed type is "Literal['x']"
 reveal_type(D2.x.value)         # N: Revealed type is "builtins.int"
@@ -1959,7 +1953,8 @@ class A(Enum):
     x: int
     def method(self) -> int: pass
 class B(A):
-    x = 1  # E: Cannot override writable attribute "x" with a final one
+    x = 1  # E: Cannot override writable attribute "x" with a final one \
+           # E: Incompatible types in assignment (expression has type "B", base class "A" defined the type as "int")
 
 class A1(Enum):
     x: int = 1  # E: Enum members must be left unannotated \
@@ -1977,8 +1972,8 @@ class B2(A2):  # E: Cannot extend enum with existing members: "A2"
 class A3(Enum):
     x: Final[int]  # type: ignore
 class B3(A3):
-    x = 1  # E: Cannot override final attribute "x" (previously declared in base class "A3")
-
+    x = 1  # E: Cannot override final attribute "x" (previously declared in base class "A3") \
+           # E: Incompatible types in assignment (expression has type "B3", base class "A3" defined the type as "int")
 [builtins fixtures/bool.pyi]
 
 [case testEnumNotFinalWithMethodsAndUninitializedValuesStub]
@@ -1990,14 +1985,16 @@ class A(Enum):  # E: Detected enum "lib.A" in a type stub with zero members. The
                 # N: See https://typing.readthedocs.io/en/latest/spec/enums.html#defining-members
     x: int
 class B(A):
-    x = 1    # E: Cannot override writable attribute "x" with a final one
+    x = 1    # E: Cannot override writable attribute "x" with a final one \
+             # E: Incompatible types in assignment (expression has type "B", base class "A" defined the type as "int")
 
 class C(Enum):
     x = 1
 class D(C):  # E: Cannot extend enum with existing members: "C" \
              # E: Detected enum "lib.D" in a type stub with zero members. There is a chance this is due to a recent change in the semantics of enum membership. If so, use `member = value` to mark an enum member, instead of `member: type` \
              # N: See https://typing.readthedocs.io/en/latest/spec/enums.html#defining-members
-    x: int   # E: Cannot assign to final name "x"
+    x: int   # E: Incompatible types in assignment (expression has type "int", base class "C" defined the type as "C") \
+             # E: Cannot assign to final name "x"
 [builtins fixtures/bool.pyi]
 
 [case testEnumNotFinalWithMethodsAndUninitializedValuesStubMember]
@@ -2425,6 +2422,49 @@ def some_a(a: A):
         reveal_type(a)  # N: Revealed type is "Literal[__main__.A.x]"
 [builtins fixtures/dict.pyi]
 
+[case testEnumAccessFromInstance]
+# flags: --python-version 3.11 --warn-unreachable
+# This was added in 3.11
+from enum import Enum, member, nonmember
+
+class A(Enum):
+    x = 1
+    y = member(2)
+    z = nonmember(3)
+
+reveal_type(A.x)  # N: Revealed type is "Literal[__main__.A.x]?"
+reveal_type(A.y)  # N: Revealed type is "Literal[__main__.A.y]?"
+reveal_type(A.z)  # N: Revealed type is "builtins.int"
+
+reveal_type(A.x.x)  # N: Revealed type is "Literal[__main__.A.x]?"
+reveal_type(A.x.x.x)  # N: Revealed type is "Literal[__main__.A.x]?"
+reveal_type(A.x.y)  # N: Revealed type is "Literal[__main__.A.y]?"
+reveal_type(A.x.y.y)  # N: Revealed type is "Literal[__main__.A.y]?"
+reveal_type(A.x.z)  # N: Revealed type is "builtins.int"
+
+reveal_type(A.y.x)  # N: Revealed type is "Literal[__main__.A.x]?"
+reveal_type(A.y.y)  # N: Revealed type is "Literal[__main__.A.y]?"
+reveal_type(A.y.z)  # N: Revealed type is "builtins.int"
+
+A.z.x  # E: "int" has no attribute "x"
+
+class B(Enum):
+    x = 1
+    value = 2
+
+reveal_type(B.x)  # N: Revealed type is "Literal[__main__.B.x]?"
+reveal_type(B.x.value)  # N: Revealed type is "Literal[2]?"
+reveal_type(B.x.x.value)  # N: Revealed type is "Literal[2]?"
+B.x.value.value  # E: "int" has no attribute "value"
+B.x.value.value.value  # E: "int" has no attribute "value"
+reveal_type(B.value)  # N: Revealed type is "Literal[__main__.B.value]?"
+reveal_type(B.value.x)  # N: Revealed type is "Literal[__main__.B.x]?"
+reveal_type(B.value.x.x)  # N: Revealed type is "Literal[__main__.B.x]?"
+reveal_type(B.value.x.value)  # N: Revealed type is "Literal[2]?"
+B.value.x.value.value  # E: "int" has no attribute "value"
+B.value.value.value  # E: "int" has no attribute "value"
+[builtins fixtures/dict.pyi]
+
 
 [case testErrorOnAnnotatedMember]
 from enum import Enum
@@ -2539,3 +2579,105 @@ def check(thing: Things) -> None:
         return None
     return None  # E: Statement is unreachable
 [builtins fixtures/enum.pyi]
+
+[case testSunderValueTypeEllipsis]
+from foo.bar import (
+    Basic, FromStub, InheritedInt, InheritedStr, InheritedFlag,
+    InheritedIntFlag, Wrapper
+)
+
+reveal_type(Basic.FOO)  # N: Revealed type is "Literal[foo.bar.Basic.FOO]?"
+reveal_type(Basic.FOO.value)  # N: Revealed type is "Literal[1]?"
+reveal_type(Basic.FOO._value_)  # N: Revealed type is "builtins.int"
+
+reveal_type(FromStub.FOO)  # N: Revealed type is "Literal[foo.bar.FromStub.FOO]?"
+reveal_type(FromStub.FOO.value)  # N: Revealed type is "builtins.int"
+reveal_type(FromStub.FOO._value_)  # N: Revealed type is "builtins.int"
+
+reveal_type(Wrapper.Nested.FOO)  # N: Revealed type is "Literal[foo.bar.Wrapper.Nested.FOO]?"
+reveal_type(Wrapper.Nested.FOO.value)  # N: Revealed type is "builtins.int"
+reveal_type(Wrapper.Nested.FOO._value_)  # N: Revealed type is "builtins.int"
+
+reveal_type(InheritedInt.FOO)  # N: Revealed type is "Literal[foo.bar.InheritedInt.FOO]?"
+reveal_type(InheritedInt.FOO.value)  # N: Revealed type is "builtins.int"
+reveal_type(InheritedInt.FOO._value_)  # N: Revealed type is "builtins.int"
+
+reveal_type(InheritedStr.FOO)  # N: Revealed type is "Literal[foo.bar.InheritedStr.FOO]?"
+reveal_type(InheritedStr.FOO.value)  # N: Revealed type is "builtins.str"
+reveal_type(InheritedStr.FOO._value_)  # N: Revealed type is "builtins.str"
+
+reveal_type(InheritedFlag.FOO)  # N: Revealed type is "Literal[foo.bar.InheritedFlag.FOO]?"
+reveal_type(InheritedFlag.FOO.value)  # N: Revealed type is "builtins.int"
+reveal_type(InheritedFlag.FOO._value_)  # N: Revealed type is "builtins.int"
+
+reveal_type(InheritedIntFlag.FOO)  # N: Revealed type is "Literal[foo.bar.InheritedIntFlag.FOO]?"
+reveal_type(InheritedIntFlag.FOO.value)  # N: Revealed type is "builtins.int"
+reveal_type(InheritedIntFlag.FOO._value_)  # N: Revealed type is "builtins.int"
+
+[file foo/__init__.pyi]
+[file foo/bar/__init__.pyi]
+from enum import Enum, IntEnum, StrEnum, Flag, IntFlag
+
+class Basic(Enum):
+    _value_: int
+    FOO = 1
+
+class FromStub(Enum):
+    _value_: int
+    FOO = ...
+
+class Wrapper:
+    class Nested(Enum):
+        _value_: int
+        FOO = ...
+
+class InheritedInt(IntEnum):
+    FOO = ...
+
+class InheritedStr(StrEnum):
+    FOO = ...
+
+class InheritedFlag(Flag):
+    FOO = ...
+
+class InheritedIntFlag(IntFlag):
+    FOO = ...
+[builtins fixtures/enum.pyi]
+
+[case testSunderValueTypeEllipsisNonStub]
+from enum import Enum, StrEnum
+
+class Basic(Enum):
+    _value_: int
+    FOO = 1
+
+reveal_type(Basic.FOO)  # N: Revealed type is "Literal[__main__.Basic.FOO]?"
+reveal_type(Basic.FOO.value)  # N: Revealed type is "Literal[1]?"
+reveal_type(Basic.FOO._value_)  # N: Revealed type is "builtins.int"
+
+# TODO: this and below should produce diagnostics, Ellipsis is not assignable to int
+# Now we do not check members against _value_ at all.
+
+class FromStub(Enum):
+    _value_: int
+    FOO = ...
+
+reveal_type(FromStub.FOO)  # N: Revealed type is "Literal[__main__.FromStub.FOO]?"
+reveal_type(FromStub.FOO.value)  # N: Revealed type is "builtins.ellipsis"
+reveal_type(FromStub.FOO._value_)  # N: Revealed type is "builtins.int"
+
+class InheritedStr(StrEnum):
+    FOO = ...
+
+reveal_type(InheritedStr.FOO)  # N: Revealed type is "Literal[__main__.InheritedStr.FOO]?"
+reveal_type(InheritedStr.FOO.value)  # N: Revealed type is "builtins.ellipsis"
+reveal_type(InheritedStr.FOO._value_)  # N: Revealed type is "builtins.ellipsis"
+
+class Wrapper:
+    class Nested(StrEnum):
+        FOO = ...
+
+reveal_type(Wrapper.Nested.FOO)  # N: Revealed type is "Literal[__main__.Wrapper.Nested.FOO]?"
+reveal_type(Wrapper.Nested.FOO.value)  # N: Revealed type is "builtins.ellipsis"
+reveal_type(Wrapper.Nested.FOO._value_)  # N: Revealed type is "builtins.ellipsis"
+[builtins fixtures/enum.pyi]
diff --git a/test-data/unit/check-errorcodes.test b/test-data/unit/check-errorcodes.test
index d6e3366401dd..bb5f658ebb50 100644
--- a/test-data/unit/check-errorcodes.test
+++ b/test-data/unit/check-errorcodes.test
@@ -1239,6 +1239,47 @@ def f(x: str) -> TypeIs[int]:  # E: Narrowed type "int" is not a subtype of inpu
 
 [builtins fixtures/tuple.pyi]
 
+[case testDynamicMetaclass]
+class A(metaclass=type(tuple)): pass  # E: Dynamic metaclass not supported for "A"  [metaclass]
+[builtins fixtures/tuple.pyi]
+
+[case testMetaclassOfTypeAny]
+# mypy: disallow-subclassing-any=True
+from typing import Any
+foo: Any = ...
+class A(metaclass=foo): pass  # E: Class cannot use "foo" as a metaclass (has type "Any")  [metaclass]
+
+[case testMetaclassOfWrongType]
+class Foo:
+    bar = 1
+class A2(metaclass=Foo.bar): pass  # E: Invalid metaclass "Foo.bar"  [metaclass]
+
+[case testMetaclassNotTypeSubclass]
+class M: pass
+class A(metaclass=M): pass  # E: Metaclasses not inheriting from "type" are not supported  [metaclass]
+
+[case testMultipleMetaclasses]
+import six
+class M1(type): pass
+
+@six.add_metaclass(M1)
+class A1(metaclass=M1): pass  # E: Multiple metaclass definitions  [metaclass]
+
+class A2(six.with_metaclass(M1), metaclass=M1): pass  # E: Multiple metaclass definitions  [metaclass]
+
+@six.add_metaclass(M1)
+class A3(six.with_metaclass(M1)): pass  # E: Multiple metaclass definitions  [metaclass]
+[builtins fixtures/tuple.pyi]
+
+[case testInvalidMetaclassStructure]
+class X(type): pass
+class Y(type): pass
+class A(metaclass=X): pass
+class B(A, metaclass=Y): pass  # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases  [metaclass] \
+                               # N: "__main__.Y" (metaclass of "__main__.B") conflicts with "__main__.X" (metaclass of "__main__.A")
+
+
+
 
 [case testOverloadedFunctionSignature]
 from typing import overload, Union
diff --git a/test-data/unit/check-expressions.test b/test-data/unit/check-expressions.test
index f3c00627892e..ea6eac9a39b3 100644
--- a/test-data/unit/check-expressions.test
+++ b/test-data/unit/check-expressions.test
@@ -1878,7 +1878,7 @@ a = {'a': 1}
 b = {'z': 26, **a}
 c = {**b}
 d = {**a, **b, 'c': 3}
-e = {1: 'a', **a}  # E: Cannot infer type argument 1 of <dict> \
+e = {1: 'a', **a}  # E: Cannot infer value of type parameter "KT" of <dict> \
                    # N: Try assigning the literal to a variable annotated as dict[<key>, <val>]
 f = {**b}  # type: Dict[int, int]  # E: Unpacked dict entry 0 has incompatible type "dict[str, int]"; expected "SupportsKeysAndGetItem[int, int]"
 g = {**Thing()}
@@ -1893,7 +1893,7 @@ i = {**Thing()}  # type: Dict[int, int]  # E: Unpacked dict entry 0 has incompat
                  # N:         def keys(self) -> Iterable[int] \
                  # N:     Got: \
                  # N:         def keys(self) -> Iterable[str]
-j = {1: 'a', **Thing()}  # E: Cannot infer type argument 1 of <dict> \
+j = {1: 'a', **Thing()}  # E: Cannot infer value of type parameter "KT" of <dict> \
                          # N: Try assigning the literal to a variable annotated as dict[<key>, <val>]
 [builtins fixtures/dict.pyi]
 [typing fixtures/typing-medium.pyi]
@@ -2419,6 +2419,35 @@ assert a == c
 [builtins fixtures/list.pyi]
 [typing fixtures/typing-full.pyi]
 
+[case testStrictEqualityForNone]
+# flags: --strict-equality --strict-equality-for-none
+
+class A: ...
+
+def a1(x: A) -> None:
+    assert x is None  # E: Non-overlapping identity check (left operand type: "A", right operand type: "None")
+def a2(x: A) -> None:
+    x is not None  # E: Non-overlapping identity check (left operand type: "A", right operand type: "None")
+def a3(x: A) -> None:
+    None == x  # E: Non-overlapping equality check (left operand type: "None", right operand type: "A")
+def a4(x: list[A]) -> None:
+    None in x  # E: Non-overlapping container check (element type: "None", container item type: "A")
+
+class B:
+    def __eq__(self, x: object) -> bool: ...
+
+def b1(x: B) -> None:
+    assert x is None  # E: Non-overlapping identity check (left operand type: "B", right operand type: "None")
+def b2(x: B) -> None:
+    x is not None  # E: Non-overlapping identity check (left operand type: "B", right operand type: "None")
+def b3(x: B) -> None:
+    x == None
+def b4(x: list[B]) -> None:
+    None in x
+
+[builtins fixtures/list.pyi]
+[typing fixtures/typing-full.pyi]
+
 [case testUnimportedHintAny]
 def f(x: Any) -> None:  # E: Name "Any" is not defined \
                         # N: Did you forget to import it from "typing"? (Suggestion: "from typing import Any")
diff --git a/test-data/unit/check-final.test b/test-data/unit/check-final.test
index d23199dc8b33..e3fc4614fc06 100644
--- a/test-data/unit/check-final.test
+++ b/test-data/unit/check-final.test
@@ -1272,3 +1272,67 @@ if FOO is not None:
 
     def func() -> int:
         return FOO
+
+[case testDisjointBase]
+from typing_extensions import disjoint_base
+
+@disjoint_base
+class Disjoint1: pass
+
+@disjoint_base
+class Disjoint2: pass
+
+@disjoint_base
+class DisjointChild(Disjoint1): pass
+
+class C1: pass
+class C2(Disjoint1, C1): pass
+class C3(DisjointChild, Disjoint1): pass
+
+class C4(Disjoint1, Disjoint2):  # E: Class "C4" has incompatible disjoint bases
+    pass
+
+class C5(Disjoint2, Disjoint1):  # E: Class "C5" has incompatible disjoint bases
+    pass
+
+class C6(Disjoint2, DisjointChild):  # E: Class "C6" has incompatible disjoint bases
+    pass
+
+class C7(DisjointChild, Disjoint2):  # E: Class "C7" has incompatible disjoint bases
+    pass
+
+class C8(DisjointChild, Disjoint1, Disjoint2):  # E: Class "C8" has incompatible disjoint bases
+    pass
+
+class C9(C2, Disjoint2):  # E: Class "C9" has incompatible disjoint bases
+    pass
+
+class C10(C3, Disjoint2):  # E: Class "C10" has incompatible disjoint bases
+    pass
+
+[builtins fixtures/tuple.pyi]
+[case testDisjointBaseSlots]
+class S1:
+    __slots__ = ("a",)
+
+class S2:
+    __slots__ = ("b",)
+
+class S3:
+    __slots__ = ()
+
+class S4(S1):
+    __slots__ = ("c",)
+
+class S5(S1, S2):  # E: Class "S5" has incompatible disjoint bases
+    pass
+
+class S6(S1, S3): pass  # OK
+class S7(S3, S1): pass  # OK
+
+class S8(S4, S1): pass  # OK
+
+class S9(S2, S4):  # E: Class "S9" has incompatible disjoint bases
+    pass
+
+[builtins fixtures/tuple.pyi]
diff --git a/test-data/unit/check-flags.test b/test-data/unit/check-flags.test
index bb64bb44d282..8eec979029d0 100644
--- a/test-data/unit/check-flags.test
+++ b/test-data/unit/check-flags.test
@@ -1116,6 +1116,39 @@ def f(x: Any) -> Any:  # E: Function is untyped after decorator transformation
 def h(x):  # E: Function is untyped after decorator transformation
     pass
 [builtins fixtures/list.pyi]
+
+[case testDisallowAnyDecoratedUnannotatedDecoratorDeferred1]
+# flags: --disallow-any-decorated
+from typing import Callable
+
+def d(f: Callable[[int], None]) -> Callable[[int], None]:
+    return f
+
+def wrapper() -> None:
+    if c:
+        @d
+        def h(x):
+            pass
+
+c = [1]
+[builtins fixtures/list.pyi]
+
+[case testDisallowAnyDecoratedUnannotatedDecoratorDeferred2]
+# flags: --disallow-any-decorated
+from typing import Callable
+
+def d(f: Callable[[int], None]) -> Callable[[int], None]:
+    return f
+
+c = 1  # no deferral - check that the previous testcase is valid
+
+def wrapper() -> None:
+    if c:
+        @d
+        def h(x):
+            pass
+[builtins fixtures/list.pyi]
+
 [case testDisallowAnyDecoratedErrorIsReportedOnlyOnce]
 # flags: --disallow-any-decorated
 
diff --git a/test-data/unit/check-functions.test b/test-data/unit/check-functions.test
index ceb7af433dce..7fa34a398ea0 100644
--- a/test-data/unit/check-functions.test
+++ b/test-data/unit/check-functions.test
@@ -2752,7 +2752,7 @@ class B:
     @property
     @dec
     def f(self) -> int: pass
-    @dec # E: Only supported top decorator is @f.setter
+    @dec # E: Only supported top decorators are "@f.setter" and "@f.deleter"
     @f.setter
     def f(self, v: int) -> None: pass
 
@@ -2764,7 +2764,6 @@ class C:
     @dec
     def f(self, v: int) -> None: pass
 [builtins fixtures/property.pyi]
-[out]
 
 [case testInvalidArgCountForProperty]
 from typing import Callable, TypeVar
@@ -2783,7 +2782,6 @@ class A:
     @property
     def h(self, *args, **kwargs) -> int: pass   # OK
 [builtins fixtures/property.pyi]
-[out]
 
 [case testSubtypingUnionGenericBounds]
 from typing import Callable, TypeVar, Union, Sequence
@@ -3694,3 +3692,19 @@ def defer() -> int: ...
 [out]
 main: note: In function "a":
 main:6: error: Unsupported operand types for + ("int" and "str")
+
+[case testNoExtraNoteForUnpacking]
+from typing import Protocol
+
+class P(Protocol):
+    arg: int
+    # Something that list and dict also have
+    def __contains__(self, item: object) -> bool: ...
+
+def foo(x: P, y: P) -> None: ...
+
+args: list[object]
+foo(*args)  # E: Argument 1 to "foo" has incompatible type "*list[object]"; expected "P"
+kwargs: dict[str, object]
+foo(**kwargs)  # E: Argument 1 to "foo" has incompatible type "**dict[str, object]"; expected "P"
+[builtins fixtures/dict.pyi]
diff --git a/test-data/unit/check-generic-subtyping.test b/test-data/unit/check-generic-subtyping.test
index f65ef3975852..ee5bcccf8ace 100644
--- a/test-data/unit/check-generic-subtyping.test
+++ b/test-data/unit/check-generic-subtyping.test
@@ -753,6 +753,20 @@ s, s = Nums() # E: Incompatible types in assignment (expression has type "int",
 [builtins fixtures/for.pyi]
 [out]
 
+[case testUninhabitedCacheChecksAmbiguous]
+# https://github.com/python/mypy/issues/19641
+from typing import Mapping, Never, TypeVar
+
+M = TypeVar("M", bound=Mapping[str,object])
+
+def get(arg: M, /) -> M:
+    return arg
+
+get({})
+
+def upcast(d: dict[Never, Never]) -> Mapping[str, object]:
+    return d  # E: Incompatible return value type (got "dict[Never, Never]", expected "Mapping[str, object]")
+[builtins fixtures/dict.pyi]
 
 -- Variance
 -- --------
diff --git a/test-data/unit/check-generics.test b/test-data/unit/check-generics.test
index 809c3c4eca48..3b535ab4a1c0 100644
--- a/test-data/unit/check-generics.test
+++ b/test-data/unit/check-generics.test
@@ -584,7 +584,7 @@ def func2(x: SameNode[T]) -> SameNode[T]:
     return x
 reveal_type(func2) # N: Revealed type is "def [T] (x: __main__.Node[T`-1, T`-1]) -> __main__.Node[T`-1, T`-1]"
 
-func2(Node(1, 'x')) # E: Cannot infer type argument 1 of "func2"
+func2(Node(1, 'x')) # E: Cannot infer value of type parameter "T" of "func2"
 y = func2(Node('x', 'x'))
 reveal_type(y) # N: Revealed type is "__main__.Node[builtins.str, builtins.str]"
 
@@ -888,7 +888,7 @@ def fun2(v: Vec[T], scale: T) -> Vec[T]:
 
 reveal_type(fun1([(1, 1)])) # N: Revealed type is "builtins.int"
 fun1(1) # E: Argument 1 to "fun1" has incompatible type "int"; expected "list[tuple[bool, bool]]"
-fun1([(1, 'x')]) # E: Cannot infer type argument 1 of "fun1"
+fun1([(1, 'x')]) # E: Cannot infer value of type parameter "T" of "fun1"
 
 reveal_type(fun2([(1, 1)], 1)) # N: Revealed type is "builtins.list[tuple[builtins.int, builtins.int]]"
 fun2([('x', 'x')], 'x') # E: Value of type variable "T" of "fun2" cannot be "str"
@@ -909,7 +909,7 @@ def f(x: Node[T, T]) -> TupledNode[T]:
     return Node(x.x, (x.x, x.x))
 
 f(1) # E: Argument 1 to "f" has incompatible type "int"; expected "Node[Never, Never]"
-f(Node(1, 'x')) # E: Cannot infer type argument 1 of "f"
+f(Node(1, 'x')) # E: Cannot infer value of type parameter "T" of "f"
 reveal_type(Node('x', 'x')) # N: Revealed type is "a.Node[builtins.str, builtins.str]"
 
 [file a.py]
@@ -2750,7 +2750,6 @@ reveal_type(func(1))  # N: Revealed type is "builtins.int"
 [builtins fixtures/tuple.pyi]
 
 [case testGenericLambdaGenericMethodNoCrash]
-# flags: --new-type-inference
 from typing import TypeVar, Union, Callable, Generic
 
 S = TypeVar("S")
@@ -2789,7 +2788,6 @@ reveal_type(dict2)  # N: Revealed type is "builtins.dict[Any, __main__.B]"
 -- ------------------------------------------------------------------
 
 [case testInferenceAgainstGenericCallable]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, List
 
 X = TypeVar('X')
@@ -2807,7 +2805,6 @@ reveal_type(bar(id))  # N: Revealed type is "builtins.list[builtins.int]"
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericCallableNoLeak]
-# flags: --new-type-inference
 from typing import TypeVar, Callable
 
 T = TypeVar('T')
@@ -2823,7 +2820,6 @@ reveal_type(f(tpl))  # N: Revealed type is "Any"
 [out]
 
 [case testInferenceAgainstGenericCallableChain]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, List
 
 X = TypeVar('X')
@@ -2836,7 +2832,6 @@ reveal_type(chain(id, id))  # N: Revealed type is "def (builtins.int) -> builtin
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericCallableGeneric]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, List
 
 S = TypeVar('S')
@@ -2857,7 +2852,6 @@ reveal_type(same(42))  # N: Revealed type is "builtins.list[builtins.int]"
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericCallableGenericReverse]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, List
 
 S = TypeVar('S')
@@ -2878,7 +2872,6 @@ reveal_type(same([42]))  # N: Revealed type is "builtins.int"
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericCallableGenericArg]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, List
 
 S = TypeVar('S')
@@ -2899,7 +2892,6 @@ reveal_type(single(42))  # N: Revealed type is "builtins.list[builtins.int]"
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericCallableGenericChain]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, List
 
 S = TypeVar('S')
@@ -2913,7 +2905,6 @@ reveal_type(comb(id, id))  # N: Revealed type is "def [T] (T`1) -> T`1"
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericCallableGenericNonLinear]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, List
 
 S = TypeVar('S')
@@ -2929,12 +2920,11 @@ def mix(fs: List[Callable[[S], T]]) -> Callable[[S], List[T]]:
 def id(__x: U) -> U:
     ...
 fs = [id, id, id]
-reveal_type(mix(fs))  # N: Revealed type is "def [S] (S`11) -> builtins.list[S`11]"
-reveal_type(mix([id, id, id]))  # N: Revealed type is "def [S] (S`13) -> builtins.list[S`13]"
+reveal_type(mix(fs))  # N: Revealed type is "def [S] (S`2) -> builtins.list[S`2]"
+reveal_type(mix([id, id, id]))  # N: Revealed type is "def [S] (S`4) -> builtins.list[S`4]"
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericCurry]
-# flags: --new-type-inference
 from typing import Callable, List, TypeVar
 
 S = TypeVar("S")
@@ -2953,7 +2943,6 @@ reveal_type(dec2(test2))  # N: Revealed type is "def [T] (T`3) -> def (T`3) -> T
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericCallableNewVariable]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, List
 
 S = TypeVar('S')
@@ -2968,7 +2957,6 @@ reveal_type(dec(test))  # N: Revealed type is "def [U] (builtins.list[U`-1]) ->
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericCallableGenericAlias]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, List
 
 S = TypeVar('S')
@@ -2986,7 +2974,6 @@ reveal_type(dec(id))  # N: Revealed type is "def [S] (S`1) -> builtins.list[S`1]
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericCallableGenericProtocol]
-# flags: --new-type-inference
 from typing import TypeVar, Protocol, Generic, Optional
 
 T = TypeVar('T')
@@ -3002,7 +2989,6 @@ reveal_type(lift(g))  # N: Revealed type is "def [T] (Union[T`1, None]) -> Union
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericSplitOrder]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, List
 
 S = TypeVar('S')
@@ -3017,7 +3003,6 @@ reveal_type(dec(id, id))  # N: Revealed type is "def (builtins.int) -> builtins.
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericSplitOrderGeneric]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, Tuple
 
 S = TypeVar('S')
@@ -3048,7 +3033,6 @@ reveal_type(id)  # N: Revealed type is "def (builtins.int) -> builtins.int"
 [builtins fixtures/tuple.pyi]
 
 [case testInferenceAgainstGenericEllipsisSelfSpecialCase]
-# flags: --new-type-inference
 from typing import Self, Callable, TypeVar
 
 T = TypeVar("T")
@@ -3062,7 +3046,6 @@ c: C
 reveal_type(c.test())  # N: Revealed type is "__main__.C"
 
 [case testInferenceAgainstGenericBoundsAndValues]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, List
 
 class B: ...
@@ -3090,7 +3073,6 @@ reveal_type(dec2(id2))  # N: Revealed type is "def (Never) -> builtins.list[Neve
                         # E: Argument 1 to "dec2" has incompatible type "Callable[[V], V]"; expected "Callable[[Never], Never]"
 
 [case testInferenceAgainstGenericLambdas]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, List
 
 S = TypeVar('S')
@@ -3118,16 +3100,15 @@ def dec4_bound(f: Callable[[I], List[T]]) -> Callable[[I], T]:
 reveal_type(dec1(lambda x: x))  # N: Revealed type is "def [T] (T`3) -> builtins.list[T`3]"
 reveal_type(dec2(lambda x: x))  # N: Revealed type is "def [S] (S`5) -> builtins.list[S`5]"
 reveal_type(dec3(lambda x: x[0]))  # N: Revealed type is "def [S] (S`8) -> S`8"
-reveal_type(dec4(lambda x: [x]))  # N: Revealed type is "def [S] (S`12) -> S`12"
+reveal_type(dec4(lambda x: [x]))  # N: Revealed type is "def [S] (S`11) -> S`11"
 reveal_type(dec1(lambda x: 1))  # N: Revealed type is "def (builtins.int) -> builtins.list[builtins.int]"
 reveal_type(dec5(lambda x: x))  # N: Revealed type is "def (builtins.int) -> builtins.list[builtins.int]"
-reveal_type(dec3(lambda x: x))  # N: Revealed type is "def [S] (S`20) -> builtins.list[S`20]"
-reveal_type(dec4(lambda x: x))  # N: Revealed type is "def [T] (builtins.list[T`24]) -> T`24"
+reveal_type(dec3(lambda x: x))  # N: Revealed type is "def [S] (S`19) -> builtins.list[S`19]"
+reveal_type(dec4(lambda x: x))  # N: Revealed type is "def [T] (builtins.list[T`23]) -> T`23"
 dec4_bound(lambda x: x)  # E: Value of type variable "I" of "dec4_bound" cannot be "list[T]"
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericParamSpecBasicInList]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, List, Tuple
 from typing_extensions import ParamSpec
 
@@ -3146,7 +3127,6 @@ reveal_type(dec(pair))  # N: Revealed type is "def [U, V] (x: U`-1, y: V`-2) ->
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericParamSpecBasicDeList]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, List, Tuple
 from typing_extensions import ParamSpec
 
@@ -3163,7 +3143,6 @@ reveal_type(dec(either))  # N: Revealed type is "def [T] (x: builtins.list[T`5],
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericParamSpecPopOff]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, List, Tuple
 from typing_extensions import ParamSpec, Concatenate
 
@@ -3184,7 +3163,6 @@ reveal_type(dec(dec))  # N: Revealed type is "def () -> def [T, P, S] (def (T`-1
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericParamSpecPopOn]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, List, Tuple
 from typing_extensions import ParamSpec, Concatenate
 
@@ -3206,7 +3184,6 @@ reveal_type(dec(dec))  # N: Revealed type is "def [T, S] (T`13, f: def () -> def
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericParamSpecVsParamSpec]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, List, Tuple, Generic
 from typing_extensions import ParamSpec, Concatenate
 
@@ -3227,7 +3204,6 @@ reveal_type(dec(h))  # N: Revealed type is "def [T, Q] (T`-1, *Q.args, **Q.kwarg
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericParamSpecVsParamSpecConcatenate]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, List, Tuple, Generic
 from typing_extensions import ParamSpec, Concatenate
 
@@ -3245,7 +3221,6 @@ reveal_type(dec(h))  # N: Revealed type is "def [T, Q] (T`-1, *Q.args, **Q.kwarg
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericParamSpecSecondary]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, List, Tuple, Generic
 from typing_extensions import ParamSpec, Concatenate
 
@@ -3263,7 +3238,6 @@ reveal_type(dec(g))  # N: Revealed type is "def (builtins.int) -> __main__.Foo[[
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericParamSpecSecondOrder]
-# flags: --new-type-inference
 from typing import TypeVar, Callable
 from typing_extensions import ParamSpec, Concatenate
 
@@ -3285,7 +3259,6 @@ reveal_type(transform(dec2))  # N: Revealed type is "def [W, T] (def (builtins.i
 [builtins fixtures/tuple.pyi]
 
 [case testNoAccidentalVariableClashInNestedGeneric]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, Generic, Tuple
 
 T = TypeVar('T')
@@ -3302,7 +3275,6 @@ def apply(a: S, b: T) -> None:
 [builtins fixtures/tuple.pyi]
 
 [case testInferenceAgainstGenericParamSpecSpuriousBoundsNotUsed]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, Generic
 from typing_extensions import ParamSpec, Concatenate
 
@@ -3321,7 +3293,6 @@ reveal_type(test)  # N: Revealed type is "def () -> def [Q] (__main__.Foo[Q`-1])
 [builtins fixtures/tuple.pyi]
 
 [case testInferenceAgainstGenericVariadicBasicInList]
-# flags: --new-type-inference
 from typing import Tuple, TypeVar, List, Callable
 from typing_extensions import Unpack, TypeVarTuple
 
@@ -3341,7 +3312,6 @@ reveal_type(dec(pair))  # N: Revealed type is "def [U, V] (U`-1, V`-2) -> builti
 [builtins fixtures/tuple.pyi]
 
 [case testInferenceAgainstGenericVariadicBasicDeList]
-# flags: --new-type-inference
 from typing import Tuple, TypeVar, List, Callable
 from typing_extensions import Unpack, TypeVarTuple
 
@@ -3359,7 +3329,6 @@ reveal_type(dec(either))  # N: Revealed type is "def [T] (builtins.list[T`5], bu
 [builtins fixtures/tuple.pyi]
 
 [case testInferenceAgainstGenericVariadicPopOff]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, List, Tuple
 from typing_extensions import Unpack, TypeVarTuple
 
@@ -3381,7 +3350,6 @@ reveal_type(dec(dec))  # N: Revealed type is "def () -> def [T, Ts, S] (def (T`-
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericVariadicPopOn]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, List, Tuple
 from typing_extensions import Unpack, TypeVarTuple
 
@@ -3404,7 +3372,6 @@ reveal_type(dec(dec))  # N: Revealed type is "def [T, S] (T`13, def () -> def (T
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericVariadicVsVariadic]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, List, Generic
 from typing_extensions import Unpack, TypeVarTuple
 
@@ -3424,7 +3391,6 @@ reveal_type(dec(g))  # N: Revealed type is "def [Ts] (*Unpack[Ts`4]) -> builtins
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericVariadicVsVariadicConcatenate]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, Generic
 from typing_extensions import Unpack, TypeVarTuple
 
@@ -3443,7 +3409,6 @@ reveal_type(dec(h))  # N: Revealed type is "def [T, Us] (T`-1, *Unpack[Us`-2]) -
 [builtins fixtures/list.pyi]
 
 [case testInferenceAgainstGenericVariadicSecondary]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, Generic
 from typing_extensions import Unpack, TypeVarTuple
 
@@ -3628,3 +3593,32 @@ def draw_none(
         takes_int_str_none(c2)
         takes_int_str_none(c3)
 [builtins fixtures/tuple.pyi]
+
+[case testPropertyWithGenericSetter]
+from typing import TypeVar
+
+class B: ...
+class C(B): ...
+T = TypeVar("T", bound=B)
+
+class Test:
+    @property
+    def foo(self) -> list[C]: ...
+    @foo.setter
+    def foo(self, val: list[T]) -> None: ...
+
+t1: Test
+t2: Test
+
+lb: list[B]
+lc: list[C]
+li: list[int]
+
+t1.foo = lb
+t1.foo = lc
+t1.foo = li  # E: Value of type variable "T" of "foo" of "Test" cannot be "int"
+
+t2.foo = [B()]
+t2.foo = [C()]
+t2.foo = [1]  # E: Value of type variable "T" of "foo" of "Test" cannot be "int"
+[builtins fixtures/property.pyi]
diff --git a/test-data/unit/check-incremental.test b/test-data/unit/check-incremental.test
index 4c170ec4753f..1658e56f582b 100644
--- a/test-data/unit/check-incremental.test
+++ b/test-data/unit/check-incremental.test
@@ -2051,7 +2051,7 @@ warn_no_return = True
 [case testIncrementalClassVar]
 from typing import ClassVar
 class A:
-    x = None  # type: ClassVar
+    x: ClassVar
 A().x = 0
 [out1]
 main:4: error: Cannot assign to class variable "x" via instance
@@ -2577,6 +2577,13 @@ C(1)[0]
 [builtins fixtures/list.pyi]
 [out]
 
+[case testSerializeRecursiveAlias]
+from typing import Callable, Union
+
+Node = Union[str, int, Callable[[], "Node"]]
+n: Node
+[out]
+
 [case testSerializeRecursiveAliases1]
 
 from typing import Type, Callable, Union
@@ -3170,13 +3177,13 @@ C(5, 'foo', True)
 
 [file a.py]
 import attrs
-@attrs.define
+@attrs.define(slots=False)
 class A:
     a: int
 
 [file b.py]
 import attrs
-@attrs.define
+@attrs.define(slots=False)
 class B:
     b: str
 
@@ -3184,7 +3191,7 @@ class B:
 from a import A
 from b import B
 import attrs
-@attrs.define
+@attrs.define(slots=False)
 class C(A, B):
     c: bool
 
@@ -5675,10 +5682,12 @@ class FinalEnum(Enum):
 [builtins fixtures/isinstance.pyi]
 [out]
 main:3: error: Cannot override writable attribute "x" with a final one
+main:3: error: Incompatible types in assignment (expression has type "Ok", base class "RegularEnum" defined the type as "int")
 main:4: error: Cannot extend enum with existing members: "FinalEnum"
 main:5: error: Cannot override final attribute "x" (previously declared in base class "FinalEnum")
 [out2]
 main:3: error: Cannot override writable attribute "x" with a final one
+main:3: error: Incompatible types in assignment (expression has type "Ok", base class "RegularEnum" defined the type as "int")
 main:4: error: Cannot extend enum with existing members: "FinalEnum"
 main:5: error: Cannot override final attribute "x" (previously declared in base class "FinalEnum")
 
@@ -6886,3 +6895,12 @@ class A:
 [out]
 [out2]
 main:3: error: Too few arguments
+
+[case testUnreachableAfterToplevelAssertImportThirdParty]
+# flags: --platform unknown
+import sys
+assert sys.platform == 'linux'
+import does_not_exist
+[builtins fixtures/ops.pyi]
+[out]
+[out2]
diff --git a/test-data/unit/check-inference-context.test b/test-data/unit/check-inference-context.test
index 0aa67b2bf7f3..7dbbd68c4215 100644
--- a/test-data/unit/check-inference-context.test
+++ b/test-data/unit/check-inference-context.test
@@ -693,7 +693,6 @@ f(lambda: None)
 g(lambda: None)
 
 [case testIsinstanceInInferredLambda]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, Optional
 T = TypeVar('T')
 S = TypeVar('S')
@@ -1009,7 +1008,7 @@ class D(C): ...
 
 def f(x: List[T], y: List[T]) -> List[T]: ...
 
-f([C()], [D()]) # E: Cannot infer type argument 1 of "f"
+f([C()], [D()]) # E: Cannot infer value of type parameter "T" of "f"
 [builtins fixtures/list.pyi]
 
 [case testInferTypeVariableFromTwoGenericTypes3]
@@ -1510,3 +1509,76 @@ def mymin(
 def check(paths: Iterable[str], key: Callable[[str], int]) -> Union[str, None]:
     return mymin(paths, key=key, default=None)
 [builtins fixtures/tuple.pyi]
+
+[case testBinaryOpInferenceContext]
+from typing import Literal, TypeVar
+
+T = TypeVar("T")
+
+def identity(x: T) -> T:
+    return x
+
+def check1(use: bool, val: str) -> "str | Literal[True]":
+    return use or identity(val)
+
+def check2(use: bool, val: str) -> "str | bool":
+    return use or identity(val)
+
+def check3(use: bool, val: str) -> "str | Literal[False]":
+    return use and identity(val)
+
+def check4(use: bool, val: str) -> "str | bool":
+    return use and identity(val)
+[builtins fixtures/tuple.pyi]
+
+[case testDictAnyOrLiteralInContext]
+from typing import Union, Optional, Any
+
+def f(x: dict[str, Union[str, None, int]]) -> None:
+    pass
+
+def g(x: Optional[dict[str, Any]], s: Optional[str]) -> None:
+    f(x or {'x': s})
+[builtins fixtures/dict.pyi]
+
+[case testReturnFallbackInferenceTuple]
+from typing import TypeVar, Union
+
+T = TypeVar("T")
+def foo(x: list[T]) -> tuple[T, ...]: ...
+
+def bar(x: list[int]) -> tuple[Union[str, int], ...]:
+    return foo(x)
+
+def bar2(x: list[int]) -> tuple[Union[str, int], ...]:
+    y = foo(x)
+    return y
+[builtins fixtures/tuple.pyi]
+
+[case testReturnFallbackInferenceUnion]
+from typing import Generic, TypeVar, Union
+
+T = TypeVar("T")
+
+class Cls(Generic[T]):
+    pass
+
+def inner(c: Cls[T]) -> Union[T, int]:
+    return 1
+
+def outer(c: Cls[T]) -> Union[T, int]:
+    return inner(c)
+
+[case testReturnFallbackInferenceAsync]
+from typing import Generic, TypeVar, Optional
+
+T = TypeVar("T")
+
+class Cls(Generic[T]):
+    pass
+
+async def inner(c: Cls[T]) -> Optional[T]:
+    return None
+
+async def outer(c: Cls[T]) -> Optional[T]:
+    return await inner(c)
diff --git a/test-data/unit/check-inference.test b/test-data/unit/check-inference.test
index 856d430a544c..63278d6c4547 100644
--- a/test-data/unit/check-inference.test
+++ b/test-data/unit/check-inference.test
@@ -343,7 +343,7 @@ for var2 in [g, h, i, j, k, l]:
     reveal_type(var2)  # N: Revealed type is "Union[builtins.int, builtins.str]"
 
 for var3 in [m, n, o, p, q, r]:
-    reveal_type(var3)  # N: Revealed type is "Union[Any, builtins.int]"
+    reveal_type(var3)  # N: Revealed type is "Union[builtins.int, Any]"
 
 T = TypeVar("T", bound=Type[Foo])
 
@@ -693,8 +693,8 @@ class A(Generic[T]): pass
 class B: pass
 
 
-f(ao, ab) # E: Cannot infer type argument 1 of "f"
-f(ab, ao) # E: Cannot infer type argument 1 of "f"
+f(ao, ab) # E: Cannot infer value of type parameter "T" of "f"
+f(ab, ao) # E: Cannot infer value of type parameter "T" of "f"
 f(ao, ao)
 f(ab, ab)
 
@@ -1247,7 +1247,7 @@ class X(TypedDict):
 
 x: X
 for a in ("hourly", "daily"):
-    reveal_type(a)  # N: Revealed type is "Union[Literal['daily']?, Literal['hourly']?]"
+    reveal_type(a)  # N: Revealed type is "Union[Literal['hourly']?, Literal['daily']?]"
     reveal_type(x[a])  # N: Revealed type is "builtins.int"
     reveal_type(a.upper())  # N: Revealed type is "builtins.str"
     c = a
@@ -1405,14 +1405,12 @@ class B: pass
 [builtins fixtures/list.pyi]
 
 [case testUninferableLambda]
-# flags: --new-type-inference
 from typing import TypeVar, Callable
 X = TypeVar('X')
 def f(x: Callable[[X], X]) -> X: pass
 y = f(lambda x: x)  # E: Need type annotation for "y"
 
 [case testUninferableLambdaWithTypeError]
-# flags: --new-type-inference
 from typing import TypeVar, Callable
 X = TypeVar('X')
 def f(x: Callable[[X], X], y: str) -> X: pass
@@ -3774,8 +3772,8 @@ reveal_type(f(x, []))  # N: Revealed type is "builtins.str"
 reveal_type(f(["yes"], []))  # N: Revealed type is "builtins.str"
 
 empty: List[NoReturn]
-f(x, empty)  # E: Cannot infer type argument 1 of "f"
-f(["no"], empty)  # E: Cannot infer type argument 1 of "f"
+f(x, empty)  # E: Cannot infer value of type parameter "T" of "f"
+f(["no"], empty)  # E: Cannot infer value of type parameter "T" of "f"
 [builtins fixtures/list.pyi]
 
 [case testInferenceWorksWithEmptyCollectionsUnion]
@@ -3783,10 +3781,18 @@ from typing import Any, Dict, NoReturn, NoReturn, Union
 
 def foo() -> Union[Dict[str, Any], Dict[int, Any]]:
     return {}
+[builtins fixtures/dict.pyi]
+
+[case testExistingEmptyCollectionDoesNotUpcast]
+from typing import Any, Dict, NoReturn, NoReturn, Union
 
 empty: Dict[NoReturn, NoReturn]
+
+def foo() -> Dict[str, Any]:
+    return empty  # E: Incompatible return value type (got "dict[Never, Never]", expected "dict[str, Any]")
+
 def bar() -> Union[Dict[str, Any], Dict[int, Any]]:
-    return empty
+    return empty  # E: Incompatible return value type (got "dict[Never, Never]", expected "Union[dict[str, Any], dict[int, Any]]")
 [builtins fixtures/dict.pyi]
 
 [case testUpperBoundInferenceFallbackNotOverused]
@@ -4149,3 +4155,19 @@ class Foo:
         else:
             self.qux = {}  # E: Need type annotation for "qux" (hint: "qux: dict[<type>, <type>] = ...")
 [builtins fixtures/dict.pyi]
+
+[case testConstraintSolvingFailureShowsCorrectArgument]
+from typing import Callable, TypeVar
+
+T1 = TypeVar('T1')
+T2 = TypeVar('T2')
+def foo(
+    a: T1,
+    b: T2,
+    c: Callable[[T2], T2],
+) -> tuple[T1, T2]: ...
+
+def bar(y: float) -> float: ...
+
+foo(1, None, bar)  # E: Cannot infer value of type parameter "T2" of "foo"
+[builtins fixtures/tuple.pyi]
diff --git a/test-data/unit/check-inline-config.test b/test-data/unit/check-inline-config.test
index 8a306b1dfac0..37d59a84c873 100644
--- a/test-data/unit/check-inline-config.test
+++ b/test-data/unit/check-inline-config.test
@@ -211,6 +211,99 @@ enable_error_code = ignore-without-code, truthy-bool
 \[mypy-tests.*]
 disable_error_code = ignore-without-code
 
+[case testInlineErrorCodesOverrideConfigSmall]
+# flags: --config-file tmp/mypy.ini
+import tests.baz
+[file tests/__init__.py]
+[file tests/baz.py]
+42 + "no"  # type: ignore
+
+[file mypy.ini]
+\[mypy]
+enable_error_code = ignore-without-code, truthy-bool
+
+\[mypy-tests.*]
+disable_error_code = ignore-without-code
+
+[case testInlineErrorCodesOverrideConfigSmall2]
+# flags: --config-file tmp/mypy.ini
+import tests.bar
+import tests.baz
+[file tests/__init__.py]
+[file tests/baz.py]
+42 + "no"  # type: ignore
+[file tests/bar.py]
+# mypy: enable-error-code="ignore-without-code"
+
+def foo() -> int: ...
+if foo: ...  # E: Function "foo" could always be true in boolean context
+42 + "no"  # type: ignore  # E: "type: ignore" comment without error code (consider "type: ignore[operator]" instead)
+
+[file mypy.ini]
+\[mypy]
+enable_error_code = ignore-without-code, truthy-bool
+
+\[mypy-tests.*]
+disable_error_code = ignore-without-code
+
+
+[case testInlineErrorCodesOverrideConfigSmallBackward]
+# flags: --config-file tmp/mypy.ini
+import tests.bar
+import tests.baz
+[file tests/__init__.py]
+[file tests/baz.py]
+42 + "no"  # type: ignore # E: "type: ignore" comment without error code (consider "type: ignore[operator]" instead)
+[file tests/bar.py]
+# mypy: disable-error-code="ignore-without-code"
+42 + "no"  # type: ignore
+
+[file mypy.ini]
+\[mypy]
+enable_error_code = ignore-without-code, truthy-bool
+
+\[mypy-tests.*]
+enable_error_code = ignore-without-code
+
+[case testInlineOverrideConfig]
+# flags: --config-file tmp/mypy.ini
+import foo
+import tests.bar
+import tests.baz
+[file foo.py]
+# mypy: disable-error-code="truthy-bool"
+class Foo:
+    pass
+
+foo = Foo()
+if foo: ...
+42 # type: ignore  # E: Unused "type: ignore" comment
+
+[file tests/__init__.py]
+[file tests/bar.py]
+# mypy: warn_unused_ignores
+
+def foo() -> int: ...
+if foo: ...  # E: Function "foo" could always be true in boolean context
+42 # type: ignore  # E: Unused "type: ignore" comment
+
+[file tests/baz.py]
+# mypy: disable-error-code="truthy-bool"
+class Foo:
+    pass
+
+foo = Foo()
+if foo: ...
+42 # type: ignore
+
+[file mypy.ini]
+\[mypy]
+warn_unused_ignores = True
+
+\[mypy-tests.*]
+warn_unused_ignores = False
+
+
 [case testIgnoreErrorsSimple]
 # mypy: ignore-errors=True
 
@@ -324,6 +417,61 @@ foo = Foo()
 if foo: ...
 42 + "no"  # type: ignore
 
-
 [case testInlinePythonVersion]
 # mypy: python-version=3.10  # E: python_version not supported in inline configuration
+
+[case testInlineErrorCodesArentRuinedByOthersBaseCase]
+# mypy: disable-error-code=name-defined
+a
+
+[case testInlineErrorCodesArentRuinedByOthersInvalid]
+# mypy: disable-error-code=name-defined
+# mypy: AMONGUS
+a
+[out]
+main:2: error: Unrecognized option: amongus = True
+
+[case testInlineErrorCodesArentRuinedByOthersInvalidBefore]
+# mypy: AMONGUS
+# mypy: disable-error-code=name-defined
+a
+[out]
+main:1: error: Unrecognized option: amongus = True
+
+[case testInlineErrorCodesArentRuinedByOthersSe]
+# mypy: disable-error-code=name-defined
+# mypy: strict-equality
+def is_magic(x: bytes) -> bool:
+    y
+    return x == 'magic' # E: Unsupported left operand type for == ("bytes")
+
+[case testInlineConfigErrorCodesOffAndOn]
+# mypy: disable-error-code=name-defined
+# mypy: enable-error-code=name-defined
+a # E: Name "a" is not defined
+
+[case testInlineConfigErrorCodesOnAndOff]
+# mypy: enable-error-code=name-defined
+# mypy: disable-error-code=name-defined
+a # E: Name "a" is not defined
+
+[case testConfigFileErrorCodesOnAndOff]
+# flags: --config-file tmp/mypy.ini
+import foo
+[file foo.py]
+42 + "no"  # type: ignore  # E: "type: ignore" comment without error code (consider "type: ignore[operator]" instead)
+[file mypy.ini]
+\[mypy]
+enable_error_code = ignore-without-code
+disable_error_code = ignore-without-code
+
+[case testInlineConfigBaseCaseWui]
+# mypy: warn_unused_ignores
+x = 1 # type: ignore # E: Unused "type: ignore" comment
+
+[case testInlineConfigIsntRuinedByOthersInvalidWui]
+# mypy: warn_unused_ignores
+# mypy: AMONGUS
+x = 1 # type: ignore # E: Unused "type: ignore" comment
+[out]
+main:2: error: Unrecognized option: amongus = True
diff --git a/test-data/unit/check-isinstance.test b/test-data/unit/check-isinstance.test
index 640fc10915d1..5043d5422108 100644
--- a/test-data/unit/check-isinstance.test
+++ b/test-data/unit/check-isinstance.test
@@ -2551,6 +2551,33 @@ def f2(x: T2) -> T2:
         return C()
 [builtins fixtures/isinstance.pyi]
 
+[case testIsInstanceDisjointBase]
+# flags: --warn-unreachable
+from typing_extensions import disjoint_base
+
+@disjoint_base
+class Disjoint1: pass
+@disjoint_base
+class Disjoint2: pass
+@disjoint_base
+class Disjoint3(Disjoint1): pass
+class Child(Disjoint1): pass
+class Unrelated: pass
+
+def f(d1: Disjoint1, u: Unrelated, c: Child) -> object:
+    if isinstance(d1, Disjoint2): # E: Subclass of "Disjoint1" and "Disjoint2" cannot exist: have distinct disjoint bases
+        return u  # E: Statement is unreachable
+    if isinstance(u, Disjoint1):  # OK
+        return d1
+    if isinstance(c, Disjoint3):  # OK
+        return c
+    if isinstance(c, Disjoint2):  # E: Subclass of "Child" and "Disjoint2" cannot exist: have distinct disjoint bases
+        return c  # E: Statement is unreachable
+    return d1
+
+[builtins fixtures/isinstance.pyi]
+
+
 [case testIsInstanceAdHocIntersectionUsage]
 # flags: --warn-unreachable
 class A: pass
diff --git a/test-data/unit/check-literal.test b/test-data/unit/check-literal.test
index d91b257b0096..3c9290b8dbbb 100644
--- a/test-data/unit/check-literal.test
+++ b/test-data/unit/check-literal.test
@@ -2976,3 +2976,22 @@ x: Type[Literal[1]]  # E: Type[...] can't contain "Literal[...]"
 y: Type[Union[Literal[1], Literal[2]]]  # E: Type[...] can't contain "Union[Literal[...], Literal[...]]"
 z: Type[Literal[1, 2]]  # E: Type[...] can't contain "Union[Literal[...], Literal[...]]"
 [builtins fixtures/tuple.pyi]
+
+[case testJoinLiteralAndInstance]
+from typing import Generic, TypeVar, Literal
+
+T = TypeVar("T")
+
+class A(Generic[T]): ...
+
+def f(a: A[T], t: T) -> T: ...
+def g(a: T, t: A[T]) -> T: ...
+
+def check(obj: A[Literal[1]]) -> None:
+    reveal_type(f(obj, 1))  # N: Revealed type is "Literal[1]"
+    reveal_type(f(obj, ''))  # E: Cannot infer value of type parameter "T" of "f" \
+                             # N: Revealed type is "Any"
+    reveal_type(g(1, obj))  # N: Revealed type is "Literal[1]"
+    reveal_type(g('', obj))  # E: Cannot infer value of type parameter "T" of "g" \
+                             # N: Revealed type is "Any"
+[builtins fixtures/tuple.pyi]
diff --git a/test-data/unit/check-modules.test b/test-data/unit/check-modules.test
index 858024e7daf2..862cd8ea3905 100644
--- a/test-data/unit/check-modules.test
+++ b/test-data/unit/check-modules.test
@@ -423,7 +423,35 @@ import typing
 __all__ = [1, 2, 3]
 [builtins fixtures/module_all.pyi]
 [out]
-main:2: error: Type of __all__ must be "Sequence[str]", not "list[int]"
+main:2: error: List item 0 has incompatible type "int"; expected "str"
+main:2: error: List item 1 has incompatible type "int"; expected "str"
+main:2: error: List item 2 has incompatible type "int"; expected "str"
+
+[case testAllMustBeSequenceStr2]
+import typing
+__all__ = 1  # E: Type of __all__ must be "Sequence[str]", not "int"
+reveal_type(__all__)  # N: Revealed type is "builtins.int"
+[builtins fixtures/module_all.pyi]
+
+[case testAllMustBeSequenceStr3]
+import typing
+__all__ = set()  # E: Need type annotation for "__all__" (hint: "__all__: set[<type>] = ...") \
+                 # E: Type of __all__ must be "Sequence[str]", not "set[Any]"
+reveal_type(__all__)  # N: Revealed type is "builtins.set[Any]"
+[builtins fixtures/set.pyi]
+
+[case testModuleAllEmptyList]
+__all__ = []
+reveal_type(__all__)  # N: Revealed type is "builtins.list[builtins.str]"
+[builtins fixtures/module_all.pyi]
+
+[case testDunderAllNotGlobal]
+class A:
+    __all__ = 1
+
+def foo() -> None:
+    __all__ = 1
+[builtins fixtures/module_all.pyi]
 
 [case testUnderscoreExportedValuesInImportAll]
 import typing
diff --git a/test-data/unit/check-narrowing.test b/test-data/unit/check-narrowing.test
index 3778c5276576..7fffd3ce94e5 100644
--- a/test-data/unit/check-narrowing.test
+++ b/test-data/unit/check-narrowing.test
@@ -2346,7 +2346,7 @@ def f() -> bool: ...
 
 y = None
 while f():
-    reveal_type(y)  # N: Revealed type is "Union[builtins.int, None]"
+    reveal_type(y)  # N: Revealed type is "Union[None, builtins.int]"
     y = 1
 reveal_type(y)  # N: Revealed type is "Union[builtins.int, None]"
 
@@ -2446,6 +2446,58 @@ while x is not None and b():
     x = f()
 [builtins fixtures/primitives.pyi]
 
+[case testNarrowPromotionsInsideUnions1]
+
+from typing import Union
+
+x: Union[str, float, None]
+y: Union[int, str]
+x = y
+reveal_type(x)  # N: Revealed type is "Union[builtins.str, builtins.int]"
+z: Union[complex, str]
+z = x
+reveal_type(z)  # N: Revealed type is "Union[builtins.int, builtins.str]"
+
+[builtins fixtures/primitives.pyi]
+
+[case testNarrowPromotionsInsideUnions2]
+# flags: --warn-unreachable
+
+from typing import Optional
+
+def b() -> bool: ...
+def i() -> int: ...
+x: Optional[float]
+
+while b():
+    x = None
+    while b():
+        reveal_type(x)  # N: Revealed type is "Union[None, builtins.int]"
+        if x is None or b():
+            x = i()
+            reveal_type(x)  # N: Revealed type is "builtins.int"
+
+[builtins fixtures/bool.pyi]
+
+[case testAvoidFalseUnreachableInFinally]
+# flags: --allow-redefinition-new --local-partial-types --warn-unreachable
+def f() -> None:
+    try:
+        x = 1
+        if int():
+            x = ""
+            return
+        if int():
+            x = None
+            return
+    finally:
+        reveal_type(x)  # N: Revealed type is "Union[builtins.int, builtins.str, None]"
+        if isinstance(x, str):
+            reveal_type(x)  # N: Revealed type is "builtins.str"
+        reveal_type(x) # N: Revealed type is "Union[builtins.int, builtins.str, None]"
+
+[builtins fixtures/isinstancelist.pyi]
+
 [case testNarrowingTypeVarMultiple]
 from typing import TypeVar
 
@@ -2593,3 +2645,22 @@ def baz(item: Base) -> None:
         reveal_type(item)  # N: Revealed type is "__main__.<subclass of "__main__.Base" and "__main__.BarMixin">"
         item.bar()
 [builtins fixtures/isinstance.pyi]
+
+[case testCustomSetterNarrowingReWidened]
+class B: ...
+class C(B): ...
+class C1(B): ...
+class D(C): ...
+
+class Test:
+    @property
+    def foo(self) -> C: ...
+    @foo.setter
+    def foo(self, val: B) -> None: ...
+
+t: Test
+t.foo = D()
+reveal_type(t.foo)  # N: Revealed type is "__main__.D"
+t.foo = C1()
+reveal_type(t.foo)  # N: Revealed type is "__main__.C"
+[builtins fixtures/property.pyi]
diff --git a/test-data/unit/check-overloading.test b/test-data/unit/check-overloading.test
index 0ccc8a2a353c..be55a182b87b 100644
--- a/test-data/unit/check-overloading.test
+++ b/test-data/unit/check-overloading.test
@@ -231,9 +231,38 @@ def f(x: 'A') -> Any: # E: Overloaded function implementation does not accept al
 
 reveal_type(f(A())) # N: Revealed type is "__main__.B"
 reveal_type(f(B())) # N: Revealed type is "__main__.A"
-
 [builtins fixtures/isinstance.pyi]
 
+[case testTypeCheckOverloadImplOverlapVarArgsAndKwargs]
+from __future__ import annotations
+from typing import overload
+
+@overload
+def foo(x: int) -> None: ...
+@overload
+def foo(a: str, /) -> None: ...
+
+def foo(*args: int | str, **kw: int) -> None:
+    pass
+[builtins fixtures/tuple.pyi]
+
+[case testTypeCheckOverloadImplOverlapVarArgsAndKwargsUnion]
+from __future__ import annotations
+from typing import overload
+
+class Foo: ...
+
+@overload
+def foo(x: int) -> None: ...
+@overload
+def foo(*, x: Foo) -> None: ...
+@overload
+def foo(a: str, /) -> None: ...
+
+def foo(*args: int | str, **kw: int | Foo) -> None:
+    pass
+[builtins fixtures/tuple.pyi]
+
 [case testTypeCheckOverloadWithImplTooSpecificRetType]
 from typing import overload, Any
 
@@ -3370,10 +3399,10 @@ def wrapper() -> None:
     obj2: Union[W1[A], W2[B]]
 
     reveal_type(foo(obj2))  # N: Revealed type is "Union[__main__.A, __main__.B]"
-    bar(obj2)  # E: Cannot infer type argument 1 of "bar"
+    bar(obj2)  # E: Cannot infer value of type parameter "T" of "bar"
 
     b1_overload: A = foo(obj2)  # E: Incompatible types in assignment (expression has type "Union[A, B]", variable has type "A")
-    b1_union: A    = bar(obj2)  # E: Cannot infer type argument 1 of "bar"
+    b1_union: A    = bar(obj2)  # E: Cannot infer value of type parameter "T" of "bar"
 
 [case testOverloadingInferUnionReturnWithObjectTypevarReturn]
 from typing import overload, Union, TypeVar, Generic
@@ -3496,7 +3525,7 @@ def t_is_same_bound(arg1: T1, arg2: S) -> Tuple[T1, S]:
     # The arguments in the tuple are swapped
     x3: Union[List[S], List[Tuple[S, T1]]]
     y3: S
-    Dummy[T1]().foo(x3, y3)  # E: Cannot infer type argument 1 of "foo" of "Dummy" \
+    Dummy[T1]().foo(x3, y3)  # E: Cannot infer value of type parameter "S" of "foo" of "Dummy" \
                              # E: Argument 1 to "foo" of "Dummy" has incompatible type "Union[list[S], list[tuple[S, T1]]]"; expected "list[tuple[T1, Any]]"
 
     x4: Union[List[int], List[Tuple[C, int]]]
@@ -6310,6 +6339,40 @@ reveal_type(f12(A()))  # N: Revealed type is "__main__.A"
 
 [typing fixtures/typing-medium.pyi]
 
+[case testAdjacentConditionalOverloads]
+# flags: --always-true true_alias
+from typing import overload
+
+true_alias = True
+
+if true_alias:
+    @overload
+    def ham(v: str) -> list[str]: ...
+
+    @overload
+    def ham(v: int) -> list[int]: ...
+
+def ham(v: "int | str") -> "list[str] | list[int]":
+    return []
+
+if true_alias:
+    @overload
+    def spam(v: str) -> str: ...
+
+    @overload
+    def spam(v: int) -> int: ...
+
+def spam(v: "int | str") -> "str | int":
+    return ""
+
+reveal_type(ham)  # N: Revealed type is "Overload(def (v: builtins.str) -> builtins.list[builtins.str], def (v: builtins.int) -> builtins.list[builtins.int])"
+reveal_type(spam)  # N: Revealed type is "Overload(def (v: builtins.str) -> builtins.str, def (v: builtins.int) -> builtins.int)"
+
+reveal_type(ham(""))  # N: Revealed type is "builtins.list[builtins.str]"
+reveal_type(ham(0))  # N: Revealed type is "builtins.list[builtins.int]"
+reveal_type(spam(""))  # N: Revealed type is "builtins.str"
+reveal_type(spam(0))  # N: Revealed type is "builtins.int"
+
 [case testOverloadIfUnconditionalFuncDef]
 # flags: --always-true True --always-false False
 from typing import overload
@@ -6603,7 +6666,6 @@ reveal_type(Snafu.snafu('123'))  # N: Revealed type is "builtins.str"
 [builtins fixtures/staticmethod.pyi]
 
 [case testOverloadedWithInternalTypeVars]
-# flags: --new-type-inference
 import m
 
 [file m.pyi]
@@ -6767,3 +6829,26 @@ class D(Generic[T]):
 a: D[str]  # E: Type argument "str" of "D" must be a subtype of "C"
 reveal_type(a.f(1))  # N: Revealed type is "builtins.int"
 reveal_type(a.f("x"))  # N: Revealed type is "builtins.str"
+
+[case testMultiAssignFromUnionInOverloadCached]
+from typing import Iterable, overload, Union, Optional
+
+@overload
+def always_bytes(str_or_bytes: None) -> None: ...
+@overload
+def always_bytes(str_or_bytes: Union[str, bytes]) -> bytes: ...
+def always_bytes(str_or_bytes: Union[None, str, bytes]) -> Optional[bytes]:
+    pass
+
+class Headers:
+    def __init__(self, iter: Iterable[tuple[bytes, bytes]]) -> None: ...
+
+headers: Union[Headers, dict[Union[str, bytes], Union[str, bytes]], Iterable[tuple[bytes, bytes]]]
+
+if isinstance(headers, dict):
+    headers = Headers(
+        (always_bytes(k), always_bytes(v)) for k, v in headers.items()
+    )
+
+reveal_type(headers)  # N: Revealed type is "Union[__main__.Headers, typing.Iterable[tuple[builtins.bytes, builtins.bytes]]]"
+[builtins fixtures/isinstancelist.pyi]
diff --git a/test-data/unit/check-parameter-specification.test b/test-data/unit/check-parameter-specification.test
index 085f6fe59809..2b4f92c7c819 100644
--- a/test-data/unit/check-parameter-specification.test
+++ b/test-data/unit/check-parameter-specification.test
@@ -921,8 +921,8 @@ class A:
     def func(self, action: Callable[_P, _R], *args: _P.args, **kwargs: _P.kwargs) -> _R:
         ...
 
-reveal_type(A.func)  # N: Revealed type is "def [_P, _R] (self: __main__.A, action: def (*_P.args, **_P.kwargs) -> _R`6, *_P.args, **_P.kwargs) -> _R`6"
-reveal_type(A().func)  # N: Revealed type is "def [_P, _R] (action: def (*_P.args, **_P.kwargs) -> _R`10, *_P.args, **_P.kwargs) -> _R`10"
+reveal_type(A.func)  # N: Revealed type is "def [_P, _R] (self: __main__.A, action: def (*_P.args, **_P.kwargs) -> _R`4, *_P.args, **_P.kwargs) -> _R`4"
+reveal_type(A().func)  # N: Revealed type is "def [_P, _R] (action: def (*_P.args, **_P.kwargs) -> _R`8, *_P.args, **_P.kwargs) -> _R`8"
 
 def f(x: int) -> int:
     ...
@@ -953,8 +953,8 @@ class A:
     def func(self, action: Job[_P, None]) -> Job[_P, None]:
         ...
 
-reveal_type(A.func)  # N: Revealed type is "def [_P] (self: __main__.A, action: __main__.Job[_P`4, None]) -> __main__.Job[_P`4, None]"
-reveal_type(A().func)  # N: Revealed type is "def [_P] (action: __main__.Job[_P`6, None]) -> __main__.Job[_P`6, None]"
+reveal_type(A.func)  # N: Revealed type is "def [_P] (self: __main__.A, action: __main__.Job[_P`3, None]) -> __main__.Job[_P`3, None]"
+reveal_type(A().func)  # N: Revealed type is "def [_P] (action: __main__.Job[_P`5, None]) -> __main__.Job[_P`5, None]"
 reveal_type(A().func(Job(lambda x: x)))  # N: Revealed type is "__main__.Job[[x: Any], None]"
 
 def f(x: int, y: int) -> None: ...
@@ -1121,7 +1121,6 @@ reveal_type(jf(1))  # N: Revealed type is "None"
 [builtins fixtures/paramspec.pyi]
 
 [case testGenericsInInferredParamspecReturn]
-# flags: --new-type-inference
 from typing import Callable, TypeVar, Generic
 from typing_extensions import ParamSpec
 
@@ -1646,7 +1645,6 @@ def f(f: Callable[P, None], *args: P.args, **kwargs: P.kwargs) -> None: ...
 [builtins fixtures/paramspec.pyi]
 
 [case testParamSpecDecoratorAppliedToGeneric]
-# flags: --new-type-inference
 from typing import Callable, List, TypeVar
 from typing_extensions import ParamSpec
 
@@ -1684,7 +1682,6 @@ reveal_type(test(*ints))  # N: Revealed type is "__main__.Foo[[*builtins.int]]"
 [builtins fixtures/paramspec.pyi]
 
 [case testParamSpecArgumentParamInferenceGeneric]
-# flags: --new-type-inference
 from typing import Callable, TypeVar
 from typing_extensions import ParamSpec
 
@@ -1702,7 +1699,6 @@ y: int = call(identity, 2)
 [builtins fixtures/paramspec.pyi]
 
 [case testParamSpecNestedApplyNoCrash]
-# flags: --new-type-inference
 from typing import Callable, TypeVar
 from typing_extensions import ParamSpec
 
@@ -2135,7 +2131,7 @@ def d(f: Callable[P, None], fn: Callable[Concatenate[Callable[P, None], P], None
 
 reveal_type(d(a, f1))  # N: Revealed type is "def (i: builtins.int)"
 reveal_type(d(a, f2))  # N: Revealed type is "def (i: builtins.int)"
-reveal_type(d(b, f1))  # E: Cannot infer type argument 1 of "d" \
+reveal_type(d(b, f1))  # E: Cannot infer value of type parameter "P" of "d" \
                        # N: Revealed type is "def (*Any, **Any)"
 reveal_type(d(b, f2))  # N: Revealed type is "def (builtins.int)"
 [builtins fixtures/paramspec.pyi]
diff --git a/test-data/unit/check-plugin-attrs.test b/test-data/unit/check-plugin-attrs.test
index 6415b5104296..42f21e945ef0 100644
--- a/test-data/unit/check-plugin-attrs.test
+++ b/test-data/unit/check-plugin-attrs.test
@@ -470,8 +470,8 @@ reveal_type(a)  # N: Revealed type is "__main__.A[builtins.int]"
 reveal_type(a.x)  # N: Revealed type is "builtins.list[builtins.int]"
 reveal_type(a.y)  # N: Revealed type is "builtins.int"
 
-A(['str'], 7)  # E: Cannot infer type argument 1 of "A"
-A([1], '2')  # E: Cannot infer type argument 1 of "A"
+A(['str'], 7)  # E: Cannot infer value of type parameter "T" of "A"
+A([1], '2')  # E: Cannot infer value of type parameter "T" of "A"
 
 [builtins fixtures/list.pyi]
 
@@ -1201,7 +1201,6 @@ class A:
 [builtins fixtures/bool.pyi]
 
 [case testAttrsFactoryBadReturn]
-# flags: --new-type-inference
 import attr
 def my_factory() -> int:
     return 7
diff --git a/test-data/unit/check-protocols.test b/test-data/unit/check-protocols.test
index f330aa4ecc02..0f19b404082e 100644
--- a/test-data/unit/check-protocols.test
+++ b/test-data/unit/check-protocols.test
@@ -4217,10 +4217,10 @@ def g2(a: Input[bytes], b: Output[bytes]) -> None:
     f(a, b)
 
 def g3(a: Input[str], b: Output[bytes]) -> None:
-    f(a, b)  # E: Cannot infer type argument 1 of "f"
+    f(a, b)  # E: Cannot infer value of type parameter "AnyStr" of "f"
 
 def g4(a: Input[bytes], b: Output[str]) -> None:
-    f(a, b)  # E: Cannot infer type argument 1 of "f"
+    f(a, b)  # E: Cannot infer value of type parameter "AnyStr" of "f"
 
 [builtins fixtures/tuple.pyi]
 
@@ -4602,3 +4602,61 @@ def deco(fn: Callable[[], T]) -> Callable[[], list[T]]: ...
 @deco
 def defer() -> int: ...
 [builtins fixtures/list.pyi]
+
+[case testProtocolClassValDescriptor]
+from typing import Any, Protocol, overload, ClassVar, Type
+
+class Desc:
+    @overload
+    def __get__(self, instance: None, owner: object) -> Desc: ...
+    @overload
+    def __get__(self, instance: object, owner: object) -> int: ...
+    def __get__(self, instance, owner):
+        pass
+
+class P(Protocol):
+    x: ClassVar[Desc]
+
+class C:
+    x = Desc()
+
+t: P = C()
+reveal_type(t.x)  # N: Revealed type is "builtins.int"
+tt: Type[P] = C
+reveal_type(tt.x)  # N: Revealed type is "__main__.Desc"
+
+bad: P = C  # E: Incompatible types in assignment (expression has type "type[C]", variable has type "P") \
+            # N: Following member(s) of "C" have conflicts: \
+            # N:     x: expected "int", got "Desc"
+
+[case testProtocolClassValCallable]
+from typing import Any, Protocol, overload, ClassVar, Type, Callable
+
+class P(Protocol):
+    foo: Callable[[object], int]
+    bar: ClassVar[Callable[[object], int]]
+
+class C:
+    foo: Callable[[object], int]
+    bar: ClassVar[Callable[[object], int]]
+
+t: P = C()
+reveal_type(t.foo)  # N: Revealed type is "def (builtins.object) -> builtins.int"
+reveal_type(t.bar)  # N: Revealed type is "def () -> builtins.int"
+tt: Type[P] = C
+reveal_type(tt.foo)  # N: Revealed type is "def (builtins.object) -> builtins.int"
+reveal_type(tt.bar)  # N: Revealed type is "def (builtins.object) -> builtins.int"
+
+[case testProtocolDecoratedSelfBound]
+from abc import abstractmethod
+from typing import Protocol, Self
+
+class Proto(Protocol):
+    @abstractmethod
+    def foo(self, x: Self) -> None: ...
+
+class Impl:
+    def foo(self, x: Self) -> None:
+        pass
+
+x: Proto = Impl()
diff --git a/test-data/unit/check-python310.test b/test-data/unit/check-python310.test
index 0695bd0380cb..5c495d2ed863 100644
--- a/test-data/unit/check-python310.test
+++ b/test-data/unit/check-python310.test
@@ -721,13 +721,14 @@ m: object
 match m:
     case xyz(y):  # E: Name "xyz" is not defined
         reveal_type(m)  # N: Revealed type is "Any"
-        reveal_type(y)  # E: Cannot determine type of "y" \
-                        # N: Revealed type is "Any"
+        reveal_type(y)  # N: Revealed type is "Any"
 
 match m:
     case xyz(z=x):  # E: Name "xyz" is not defined
-        reveal_type(x)  # E: Cannot determine type of "x" \
-                        # N: Revealed type is "Any"
+        reveal_type(x)  # N: Revealed type is "Any"
+    case (xyz1() as n) | (xyz2(attr=n)):  # E: Name "xyz1" is not defined \
+                                          # E: Name "xyz2" is not defined
+        reveal_type(n)  # N: Revealed type is "Any"
 
 [case testMatchClassPatternCaptureDataclass]
 from dataclasses import dataclass
@@ -1002,15 +1003,24 @@ match m:
 [builtins fixtures/tuple.pyi]
 
 [case testMatchClassPatternNonexistentKeyword]
+from typing import Any
 class A: ...
 
 m: object
+n: Any
 
 match m:
     case A(a=j):  # E: Class "__main__.A" has no attribute "a"
         reveal_type(m)  # N: Revealed type is "__main__.A"
         reveal_type(j)  # N: Revealed type is "Any"
 
+match n:
+    # Matching against object should not emit an error for non-existing keys
+    case object(a=k):
+        reveal_type(n)  # N: Revealed type is "builtins.object"
+        reveal_type(n.a)  # N: Revealed type is "Any"
+        reveal_type(k)  # N: Revealed type is "Any"
+
 [case testMatchClassPatternDuplicateKeyword]
 class A:
     a: str
@@ -1204,13 +1214,13 @@ match m:
     case 1 | "foo":
         reveal_type(m)  # N: Revealed type is "Union[Literal[1], Literal['foo']]"
 
-[case testMatchOrPatterCapturesMissing]
+[case testMatchOrPatternCapturesMissing]
 from typing import List
 m: List[int]
 
 match m:
     case [x, y] | list(x):  # E: Alternative patterns bind different names
-        reveal_type(x)  # N: Revealed type is "builtins.object"
+        reveal_type(x)  # N: Revealed type is "Union[builtins.int, builtins.list[builtins.int]]"
         reveal_type(y)  # N: Revealed type is "builtins.int"
 [builtins fixtures/list.pyi]
 
@@ -1219,7 +1229,7 @@ m: object
 
 match m:
     case list(x) | dict(x):
-        reveal_type(x)  # N: Revealed type is "typing.Iterable[Any]"
+        reveal_type(x)  # N: Revealed type is "Union[builtins.list[Any], builtins.dict[Any, Any]]"
 [builtins fixtures/dict.pyi]
 
 -- Interactions --
@@ -1302,7 +1312,7 @@ def main() -> None:
         case a:
             reveal_type(a)  # N: Revealed type is "builtins.int"
 
-[case testMatchCapturePatternFromAsyncFunctionReturningUnion-xfail]
+[case testMatchCapturePatternFromAsyncFunctionReturningUnion]
 async def func1(arg: bool) -> str | int: ...
 async def func2(arg: bool) -> bytes | int: ...
 
@@ -1383,6 +1393,16 @@ match m:
         reveal_type(a)
 [builtins fixtures/isinstancelist.pyi]
 
+[case testMatchSubjectAssignExprWithGuard]
+from typing import Optional
+def func() -> Optional[str]: ...
+
+match m := func():
+    case _ if not m:
+        reveal_type(m)  # N: Revealed type is "Union[Literal[''], None]"
+    case _:
+        reveal_type(m)  # N: Revealed type is "builtins.str"
+
 -- Exhaustiveness --
 
 [case testMatchUnionNegativeNarrowing]
@@ -1405,7 +1425,7 @@ m: Union[str, bytes, int]
 
 match m:
     case str(a) | bytes(a):
-        reveal_type(a)  # N: Revealed type is "builtins.object"
+        reveal_type(a)  # N: Revealed type is "Union[builtins.str, builtins.bytes]"
         reveal_type(m)  # N: Revealed type is "Union[builtins.str, builtins.bytes]"
     case b:
         reveal_type(b)  # N: Revealed type is "builtins.int"
@@ -2179,9 +2199,11 @@ def f() -> None:
     match x := returns_a_or_none():
         case A():
             reveal_type(x.a)  # N: Revealed type is "builtins.int"
+    reveal_type(x)  # N: Revealed type is "Union[__main__.A, None]"
     match x := returns_a():
         case A():
             reveal_type(x.a)  # N: Revealed type is "builtins.int"
+    reveal_type(x)  # N: Revealed type is "__main__.A"
     y = returns_a_or_none()
     match y:
         case A():
@@ -2586,6 +2608,110 @@ def fn2(x: Some | int | str) -> None:
             pass
 [builtins fixtures/dict.pyi]
 
+[case testMatchFunctionCall]
+# flags: --warn-unreachable
+
+def fn() -> int | str: ...
+
+match fn():
+    case str(s):
+        reveal_type(s)  # N: Revealed type is "builtins.str"
+    case int(i):
+        reveal_type(i)  # N: Revealed type is "builtins.int"
+    case other:
+        other  # E: Statement is unreachable
+
+[case testMatchAttribute]
+# flags: --warn-unreachable
+
+class A:
+    foo: int | str
+
+match A().foo:
+    case str(s):
+        reveal_type(s)  # N: Revealed type is "builtins.str"
+    case int(i):
+        reveal_type(i)  # N: Revealed type is "builtins.int"
+    case other:
+        other  # E: Statement is unreachable
+
+[case testMatchLiteral]
+# flags: --warn-unreachable
+
+def int_literal() -> None:
+    match 12:
+        case 1 as s:
+            reveal_type(s)  # N: Revealed type is "Literal[1]"
+        case int(i):
+            reveal_type(i)  # N: Revealed type is "Literal[12]?"
+        case other:
+            other  # E: Statement is unreachable
+
+def str_literal() -> None:
+    match 'foo':
+        case 'a' as s:
+            reveal_type(s)  # N: Revealed type is "Literal['a']"
+        case str(i):
+            reveal_type(i)  # N: Revealed type is "Literal['foo']?"
+        case other:
+            other  # E: Statement is unreachable
+
+[case testMatchOperations]
+# flags: --warn-unreachable
+
+x: int
+match -x:
+    case -1 as s:
+        reveal_type(s)  # N: Revealed type is "Literal[-1]"
+    case int(s):
+        reveal_type(s)  # N: Revealed type is "builtins.int"
+    case other:
+        other  # E: Statement is unreachable
+
+match 1 + 2:
+    case 3 as s:
+        reveal_type(s)  # N: Revealed type is "Literal[3]"
+    case int(s):
+        reveal_type(s)  # N: Revealed type is "builtins.int"
+    case other:
+        other  # E: Statement is unreachable
+
+match 1 > 2:
+    case True as s:
+        reveal_type(s)  # N: Revealed type is "Literal[True]"
+    case False as s:
+        reveal_type(s)  # N: Revealed type is "Literal[False]"
+    case other:
+        other  # E: Statement is unreachable
+[builtins fixtures/ops.pyi]
+
+[case testMatchDictItem]
+# flags: --warn-unreachable
+
+m: dict[str, int | str]
+k: str
+
+match m[k]:
+    case str(s):
+        reveal_type(s)  # N: Revealed type is "builtins.str"
+    case int(i):
+        reveal_type(i)  # N: Revealed type is "builtins.int"
+    case other:
+        other  # E: Statement is unreachable
+
+[builtins fixtures/dict.pyi]
+
+[case testMatchLiteralValuePathological]
+# flags: --warn-unreachable
+
+match 0:
+    case 0 as i:
+        reveal_type(i)  # N: Revealed type is "Literal[0]?"
+    case int(i):
+        i  # E: Statement is unreachable
+    case other:
+        other  # E: Statement is unreachable
+
 [case testMatchNamedTupleSequence]
 from typing import Any, NamedTuple
 
@@ -2601,6 +2727,28 @@ def f(t: T) -> None:
             reveal_type(k)  # N: Revealed type is "tuple[builtins.int, fallback=__main__.K]"
 [builtins fixtures/tuple.pyi]
 
+[case testMatchTypeObjectTypeVar]
+# flags: --warn-unreachable
+from typing import TypeVar
+import b
+
+T_Choice = TypeVar("T_Choice", bound=b.One | b.Two)
+
+def switch(choice: type[T_Choice]) -> None:
+    match choice:
+        case b.One:
+            reveal_type(choice)  # N: Revealed type is "def () -> b.One"
+        case b.Two:
+            reveal_type(choice)  # N: Revealed type is "def () -> b.Two"
+        case _:
+            reveal_type(choice)  # N: Revealed type is "type[T_Choice`-1]"
+
+[file b.py]
+class One: ...
+class Two: ...
+
+[builtins fixtures/tuple.pyi]
+
 [case testNewRedefineMatchBasics]
 # flags: --allow-redefinition-new --local-partial-types
 
@@ -2817,3 +2965,13 @@ match value_type:
     case _:
         assert_never(value_type)
 [builtins fixtures/tuple.pyi]
+
+[case testAssignmentToFinalInMatchCaseNotAllowed]
+from typing import Final
+
+FOO: Final[int] = 10
+
+val: int = 8
+match val:
+    case FOO:  # E: Cannot assign to final name "FOO"
+        pass
diff --git a/test-data/unit/check-python312.test b/test-data/unit/check-python312.test
index bfd6334b5077..382822ced861 100644
--- a/test-data/unit/check-python312.test
+++ b/test-data/unit/check-python312.test
@@ -2038,12 +2038,13 @@ class Z: ...  # E: Name "Z" already defined on line 2
 # https://github.com/python/mypy/issues/18856
 class A[*Ts]: ...
 
-A[*tuple[int, ...], *tuple[int, ...]]  # E: More than one Unpack in a type is not allowed
-a: A[*tuple[int, ...], *tuple[int, ...]]  # E: More than one Unpack in a type is not allowed
-def foo(a: A[*tuple[int, ...], *tuple[int, ...]]): ...  # E: More than one Unpack in a type is not allowed
+A[*tuple[int, ...], *tuple[int, ...]]  # E: More than one variadic Unpack in a type is not allowed
+A[*tuple[*tuple[int, ...]], *tuple[*tuple[int, ...]]]  # E: More than one variadic Unpack in a type is not allowed
+a: A[*tuple[int, ...], *tuple[int, ...]]  # E: More than one variadic Unpack in a type is not allowed
+def foo(a: A[*tuple[int, ...], *tuple[int, ...]]): ...  # E: More than one variadic Unpack in a type is not allowed
 
-tuple[*tuple[int, ...], *tuple[int, ...]]  # E: More than one Unpack in a type is not allowed
-b: tuple[*tuple[int, ...], *tuple[int, ...]]  # E: More than one Unpack in a type is not allowed
+tuple[*tuple[int, ...], *tuple[int, ...]]  # E: More than one variadic Unpack in a type is not allowed
+b: tuple[*tuple[int, ...], *tuple[int, ...]]  # E: More than one variadic Unpack in a type is not allowed
 [builtins fixtures/tuple.pyi]
 [typing fixtures/typing-full.pyi]
 
@@ -2084,3 +2085,39 @@ reveal_type(A1().x)  # N: Revealed type is "builtins.int"
 reveal_type(A2().x)  # N: Revealed type is "builtins.int"
 reveal_type(A3().x)  # N: Revealed type is "builtins.list[builtins.int]"
 [builtins fixtures/tuple.pyi]
+
+[case testDataclassWithTypeVarTuple]
+# flags: --python-version 3.13
+# https://github.com/python/mypy/issues/19559
+from typing import Callable
+from dataclasses import dataclass
+
+@dataclass
+class Test[*Ts, R]:
+    a: Callable[[*Ts], R]
+[builtins fixtures/dict.pyi]
+
+[case testPEP695AliasDoesNotReferToFullname]
+# https://github.com/python/mypy/issues/19698
+from typing import TypeAliasType
+type D = dict
+type T = type
+type TA = TypeAliasType
+
+D()          # E: "TypeAliasType" not callable
+X = TA("Y")  # E: "TypeAliasType" not callable
+
+x: object
+if T(x) is str:     # E: "TypeAliasType" not callable
+    reveal_type(x)  # N: Revealed type is "builtins.object"
+[builtins fixtures/tuple.pyi]
+[typing fixtures/typing-full.pyi]
+
+[case testPEP695TypeAliasForwardReferenceInUnusedTypeVar]
+# https://discuss.python.org/t/103305
+type Alias1[T: "A"] = int
+type Alias2[T: ("A", int)] = int
+class A: ...
+
+x1: Alias1[A]  # ok
+x2: Alias2[A]  # ok
diff --git a/test-data/unit/check-python314.test b/test-data/unit/check-python314.test
new file mode 100644
index 000000000000..f1043aab860a
--- /dev/null
+++ b/test-data/unit/check-python314.test
@@ -0,0 +1,3 @@
+[case testTemplateString]
+reveal_type(t"mypy")  # E: PEP 750 template strings are not yet supported \
+                      # N: Revealed type is "Any"
diff --git a/test-data/unit/check-recursive-types.test b/test-data/unit/check-recursive-types.test
index 7ed5ea53c27e..86e9f02b5263 100644
--- a/test-data/unit/check-recursive-types.test
+++ b/test-data/unit/check-recursive-types.test
@@ -54,7 +54,7 @@ reveal_type(flatten([1, [2, [3]]]))  # N: Revealed type is "builtins.list[builti
 
 class Bad: ...
 x: Nested[int] = [1, [2, [3]]]
-x = [1, [Bad()]]  # E: List item 1 has incompatible type "list[Bad]"; expected "Union[int, Nested[int]]"
+x = [1, [Bad()]]  # E: List item 0 has incompatible type "Bad"; expected "Union[int, Nested[int]]"
 [builtins fixtures/isinstancelist.pyi]
 
 [case testRecursiveAliasGenericInferenceNested]
@@ -605,7 +605,7 @@ class NT(NamedTuple, Generic[T]):
 class A: ...
 class B(A): ...
 
-nti: NT[int] = NT(key=0, value=NT(key=1, value=A()))  # E: Argument "value" to "NT" has incompatible type "NT[A]"; expected "Union[int, NT[int]]"
+nti: NT[int] = NT(key=0, value=NT(key=1, value=A()))  # E: Argument "value" to "NT" has incompatible type "A"; expected "Union[int, NT[int]]"
 reveal_type(nti)  # N: Revealed type is "tuple[builtins.int, Union[builtins.int, ...], fallback=__main__.NT[builtins.int]]"
 
 nta: NT[A]
diff --git a/test-data/unit/check-redefine2.test b/test-data/unit/check-redefine2.test
index 1062be6976c0..1abe957240b5 100644
--- a/test-data/unit/check-redefine2.test
+++ b/test-data/unit/check-redefine2.test
@@ -628,7 +628,7 @@ def f1() -> None:
 def f2() -> None:
     x = None
     while int():
-        reveal_type(x) # N: Revealed type is "Union[builtins.str, None]"
+        reveal_type(x) # N: Revealed type is "Union[None, builtins.str]"
         if int():
             x = ""
     reveal_type(x) # N: Revealed type is "Union[None, builtins.str]"
@@ -791,8 +791,7 @@ def f3() -> None:
             x = ""
             return
     finally:
-        reveal_type(x) # N: Revealed type is "Union[builtins.int, builtins.str]" \
-            # N: Revealed type is "builtins.int"
+        reveal_type(x) # N: Revealed type is "Union[builtins.int, builtins.str]"
     reveal_type(x) # N: Revealed type is "builtins.int"
 
 def f4() -> None:
@@ -924,7 +923,7 @@ class X(TypedDict):
 
 x: X
 for a in ("hourly", "daily"):
-    reveal_type(a)  # N: Revealed type is "Union[Literal['daily']?, Literal['hourly']?]"
+    reveal_type(a)  # N: Revealed type is "Union[Literal['hourly']?, Literal['daily']?]"
     reveal_type(x[a])  # N: Revealed type is "builtins.int"
     reveal_type(a.upper())  # N: Revealed type is "builtins.str"
     c = a
@@ -1074,7 +1073,7 @@ def f() -> None:
         while int():
             x = [x]
 
-    reveal_type(x) # N: Revealed type is "Union[Any, builtins.list[Any], builtins.list[Union[Any, builtins.list[Any]]], builtins.list[Union[Any, builtins.list[Any], builtins.list[Union[Any, builtins.list[Any]]]]], builtins.list[Union[Any, builtins.list[Any], builtins.list[Union[Any, builtins.list[Any]]], builtins.list[Union[Any, builtins.list[Any], builtins.list[Union[Any, builtins.list[Any]]]]]]]]"
+    reveal_type(x) # N: Revealed type is "Union[Any, builtins.list[Any]]"
 
 [case testNewRedefinePartialNoneEmptyList]
 # flags: --allow-redefinition-new --local-partial-types
diff --git a/test-data/unit/check-selftype.test b/test-data/unit/check-selftype.test
index cb7e5a9fac71..6481a1766944 100644
--- a/test-data/unit/check-selftype.test
+++ b/test-data/unit/check-selftype.test
@@ -2018,7 +2018,7 @@ class Ben(Object):
     }
     @classmethod
     def doit(cls) -> Foo:
-        reveal_type(cls.MY_MAP)  # N: Revealed type is "builtins.dict[builtins.str, def [Self <: __main__.Foo] (self: Self`4) -> Self`4]"
+        reveal_type(cls.MY_MAP)  # N: Revealed type is "builtins.dict[builtins.str, def [Self <: __main__.Foo] (self: Self`1) -> Self`1]"
         foo_method = cls.MY_MAP["foo"]
         return foo_method(Foo())
 [builtins fixtures/isinstancelist.pyi]
@@ -2219,3 +2219,130 @@ class B:
 class C(A, B):  # OK: both methods take Self
     pass
 [builtins fixtures/tuple.pyi]
+
+[case testSelfTypeClassMethodNotSilentlyErased]
+from typing import Self, Optional
+
+class X:
+    _inst: Optional[Self] = None
+    @classmethod
+    def default(cls) -> Self:
+        reveal_type(cls._inst)  # N: Revealed type is "Union[Self`0, None]"
+        if cls._inst is None:
+            cls._inst = cls()
+        return cls._inst
+
+reveal_type(X._inst)  # E: Access to generic instance variables via class is ambiguous \
+                      # N: Revealed type is "Union[__main__.X, None]"
+reveal_type(X()._inst)  # N: Revealed type is "Union[__main__.X, None]"
+
+class Y(X): ...
+reveal_type(Y._inst)  # E: Access to generic instance variables via class is ambiguous \
+                      # N: Revealed type is "Union[__main__.Y, None]"
+reveal_type(Y()._inst)  # N: Revealed type is "Union[__main__.Y, None]"
+[builtins fixtures/tuple.pyi]
+
+[case testSelfInFuncDecoratedClassmethod]
+from collections.abc import Callable
+from typing import Self, TypeVar
+
+T = TypeVar("T")
+
+def debug(make: Callable[[type[T]], T]) -> Callable[[type[T]], T]:
+    return make
+
+class Foo:
+    @classmethod
+    @debug
+    def make(cls) -> Self:
+        return cls()
+
+class Bar(Foo): ...
+
+reveal_type(Foo.make())  # N: Revealed type is "__main__.Foo"
+reveal_type(Foo().make())  # N: Revealed type is "__main__.Foo"
+reveal_type(Bar.make())  # N: Revealed type is "__main__.Bar"
+reveal_type(Bar().make())  # N: Revealed type is "__main__.Bar"
+[builtins fixtures/tuple.pyi]
+
+[case testSelfInClassDecoratedClassmethod]
+from typing import Callable, Generic, TypeVar, Self
+
+T = TypeVar("T")
+
+class W(Generic[T]):
+    def __init__(self, fn: Callable[..., T]) -> None: ...
+    def __call__(self) -> T: ...
+
+class Check:
+    @W
+    def foo(self) -> Self:
+        ...
+
+reveal_type(Check.foo())  # N: Revealed type is "def () -> __main__.Check"
+reveal_type(Check().foo())  # N: Revealed type is "__main__.Check"
+[builtins fixtures/tuple.pyi]
+
+[case testSelfInClassmethodWithOtherSelfMethod]
+from typing import Any, Callable, Self, TypeVar
+
+_C = TypeVar("_C", bound=Callable[..., Any])
+
+def identity(func: _C, /) -> _C:
+    return func
+
+class A:
+    def meth(self) -> Self: ...
+
+    @classmethod
+    def other_meth(cls) -> Self:
+        reveal_type(cls.meth)  # N: Revealed type is "def [Self <: __main__.A] (self: Self`1) -> Self`1"
+        reveal_type(A.meth)  # N: Revealed type is "def [Self <: __main__.A] (self: Self`2) -> Self`2"
+        return cls().meth()
+
+class B:
+    @identity
+    def meth(self) -> Self: ...
+
+    @classmethod
+    def other_meth(cls) -> Self:
+        reveal_type(cls.meth)  # N: Revealed type is "def [Self <: __main__.B] (self: Self`5) -> Self`5"
+        reveal_type(B.meth)  # N: Revealed type is "def [Self <: __main__.B] (self: Self`6) -> Self`6"
+        return cls().meth()
+
+class C:
+    @classmethod
+    def other_meth(cls) -> Self: ...
+
+    def meth(self) -> Self:
+        reveal_type(self.other_meth)  # N: Revealed type is "def () -> Self`0"
+        reveal_type(type(self).other_meth)  # N: Revealed type is "def () -> Self`0"
+        return self.other_meth()
+[builtins fixtures/tuple.pyi]
+
+[case testSelfTypeUpperBoundFiler]
+from typing import Generic, TypeVar, overload, Sequence
+
+class B: ...
+class C(B): ...
+
+TB = TypeVar("TB", bound=B)
+TC = TypeVar("TC", bound=C)
+
+class G(Generic[TB]):
+    @overload
+    def test(self: G[TC]) -> list[TC]: ...
+    @overload
+    def test(self: G[TB]) -> Sequence[TB]: ...
+    def test(self):
+        ...
+
+class D1(B): ...
+class D2(C): ...
+
+gb: G[D1]
+gc: G[D2]
+
+reveal_type(gb.test())  # N: Revealed type is "typing.Sequence[__main__.D1]"
+reveal_type(gc.test())  # N: Revealed type is "builtins.list[__main__.D2]"
+[builtins fixtures/list.pyi]
diff --git a/test-data/unit/check-serialize.test b/test-data/unit/check-serialize.test
index 63d9ccfc80cb..03c185a5694b 100644
--- a/test-data/unit/check-serialize.test
+++ b/test-data/unit/check-serialize.test
@@ -158,6 +158,7 @@ def f(__x: int) -> None: pass
 [out2]
 tmp/a.py:3: error: Argument 1 to "f" has incompatible type "str"; expected "int"
 tmp/a.py:4: error: Unexpected keyword argument "__x" for "f"
+tmp/b.py: note: "f" defined here
 
 [case testSerializeArgumentKindsErrors]
 import a
@@ -223,6 +224,7 @@ def f(x: int) -> int: pass
 [out2]
 tmp/a.py:2: note: Revealed type is "builtins.str"
 tmp/a.py:3: error: Unexpected keyword argument "x" for "f"
+tmp/b.py: note: "f" defined here
 
 [case testSerializeTypeGuardFunction]
 import a
diff --git a/test-data/unit/check-slots.test b/test-data/unit/check-slots.test
index b7ce5e596101..25dd630e1cbe 100644
--- a/test-data/unit/check-slots.test
+++ b/test-data/unit/check-slots.test
@@ -180,6 +180,7 @@ b.m = 2
 b.b = 2
 b._two = 2
 [out]
+main:5: error: Class "B" has incompatible disjoint bases
 main:11: error: Trying to assign name "_one" that is not in "__slots__" of type "__main__.B"
 main:16: error: "B" has no attribute "b"
 main:17: error: "B" has no attribute "_two"
@@ -496,6 +497,29 @@ class A:
         self.missing = 3
 [builtins fixtures/dict.pyi]
 
+[case testSlotsNotInClass]
+# Shouldn't be triggered
+__slots__ = [1, 2]
+reveal_type(__slots__)  # N: Revealed type is "builtins.list[builtins.int]"
+
+def foo() -> None:
+    __slots__ = 1
+    reveal_type(__slots__)  # N: Revealed type is "builtins.int"
+
+[case testSlotsEmptyList]
+class A:
+    __slots__ = []
+    reveal_type(__slots__)  # N: Revealed type is "builtins.list[builtins.str]"
+
+reveal_type(A.__slots__)  # N: Revealed type is "builtins.list[builtins.str]"
+
+[case testSlotsEmptySet]
+class A:
+    __slots__ = set()
+    reveal_type(__slots__)  # N: Revealed type is "builtins.set[builtins.str]"
+
+reveal_type(A.__slots__)  # N: Revealed type is "builtins.set[builtins.str]"
+[builtins fixtures/set.pyi]
 
 [case testSlotsWithAny]
 from typing import Any
@@ -521,3 +545,19 @@ x = X()
 X.a  # E: "a" in __slots__ conflicts with class variable access
 x.a
 [builtins fixtures/tuple.pyi]
+
+[case testSlotsOnSelfType]
+from typing_extensions import Self
+
+class X:
+    __slots__ = ("foo",)
+    foo: int
+
+    def method1(self: Self) -> Self:
+        self.bar = 0  # E: Trying to assign name "bar" that is not in "__slots__" of type "__main__.X"
+        return self
+
+    def method2(self) -> Self:
+        self.bar = 0  # E: Trying to assign name "bar" that is not in "__slots__" of type "__main__.X"
+        return self
+[builtins fixtures/tuple.pyi]
diff --git a/test-data/unit/check-tuples.test b/test-data/unit/check-tuples.test
index 615ba129dad5..cfdd2aacc4d2 100644
--- a/test-data/unit/check-tuples.test
+++ b/test-data/unit/check-tuples.test
@@ -1612,7 +1612,7 @@ t4: Tuple[int, int, int, int, int, int, int, int, int, int, int, int] = (1, 2, 3
 t5: Tuple[int, int] = (1, 2, "s", 4)  # E: Incompatible types in assignment (expression has type "tuple[int, int, str, int]", variable has type "tuple[int, int]")
 
 # long initializer assignment with mismatched pairs
-t6: Tuple[int, int, int, int, int, int, int, int, int, int, int, int] = (1, 2, 3, 4, 5, 6, 7, 8, "str", "str", "str", "str", 1, 1, 1, 1, 1) # E: Incompatible types in assignment (expression has type tuple[int, int, ... <15 more items>], variable has type tuple[int, int, ... <10 more items>])
+t6: Tuple[int, int, int, int, int, int, int, int, int, int, int, int] = (1, 2, 3, 4, 5, 6, 7, 8, "str", "str", "str", "str", 1, 1, 1, 1, 1) # E: Incompatible types in assignment (expression has type "tuple[int, int, ... <15 more items>]", variable has type "tuple[int, int, ... <10 more items>]")
 
 [builtins fixtures/tuple.pyi]
 
diff --git a/test-data/unit/check-typeddict.test b/test-data/unit/check-typeddict.test
index a068a63274ca..34cae74d795b 100644
--- a/test-data/unit/check-typeddict.test
+++ b/test-data/unit/check-typeddict.test
@@ -4271,3 +4271,39 @@ reveal_type(dicts.TF)  # N: Revealed type is "def (*, user_id: builtins.int =) -
 reveal_type(dicts.TotalFalse)  # N: Revealed type is "def (*, user_id: builtins.int =) -> TypedDict('__main__.Dicts.TF', {'user_id'?: builtins.int})"
 [builtins fixtures/dict.pyi]
 [typing fixtures/typing-typeddict.pyi]
+
+[case testRecursiveNestedTypedDictInference]
+from typing import TypedDict, Sequence
+from typing_extensions import NotRequired
+
+class Component(TypedDict):
+    type: str
+    components: NotRequired[Sequence['Component']]
+
+inputs: Sequence[Component] = [{
+    'type': 'tuple',
+    'components': [
+        {'type': 'uint256'},
+        {'type': 'address'},
+    ]
+}]
+[builtins fixtures/dict.pyi]
+[typing fixtures/typing-typeddict.pyi]
+
+[case testTypedDictAssignableToWiderContext]
+from typing import TypedDict, Union
+
+class TD(TypedDict):
+    x: int
+
+x: Union[TD, dict[str, str]] = {"x": "foo"}
+y: Union[TD, dict[str, int]] = {"x": "foo"}  # E: Dict entry 0 has incompatible type "str": "str"; expected "str": "int"
+
+def ok(d: Union[TD, dict[str, str]]) -> None: ...
+ok({"x": "foo"})
+
+def bad(d: Union[TD, dict[str, int]]) -> None: ...
+bad({"x": "foo"})  # E: Dict entry 0 has incompatible type "str": "str"; expected "str": "int"
+
+[builtins fixtures/dict.pyi]
+[typing fixtures/typing-typeddict.pyi]
diff --git a/test-data/unit/check-typeguard.test b/test-data/unit/check-typeguard.test
index c43eead67876..93e665e4548c 100644
--- a/test-data/unit/check-typeguard.test
+++ b/test-data/unit/check-typeguard.test
@@ -731,6 +731,53 @@ assert a(x=x)
 reveal_type(x)  # N: Revealed type is "builtins.int"
 [builtins fixtures/tuple.pyi]
 
+# https://github.com/python/mypy/issues/19575
+[case testNoCrashOnDunderCallTypeGuardTemporaryObject]
+from typing_extensions import TypeGuard
+class E:
+    def __init__(self) -> None: ...
+    def __call__(self, o: object) -> TypeGuard[int]:
+        return True
+x = object()
+if E()(x):
+    reveal_type(x)  # N: Revealed type is "builtins.int"
+[builtins fixtures/tuple.pyi]
+
+[case testNoCrashOnDunderCallTypeIsTemporaryObject]
+from typing_extensions import TypeIs
+class E:
+    def __init__(self) -> None: ...
+    def __call__(self, o: object) -> TypeIs[int]:
+        return True
+x = object()
+if E()(x):
+    reveal_type(x)  # N: Revealed type is "builtins.int"
+[builtins fixtures/tuple.pyi]
+
+[case testNoCrashOnDunderCallTypeIsTemporaryObjectGeneric]
+from typing import Generic, TypeVar
+from typing_extensions import TypeIs
+T = TypeVar("T")
+class E(Generic[T]):
+    def __init__(self) -> None: ...
+    def __call__(self, o: object) -> TypeIs[T]:
+        return True
+x = object()
+if E[int]()(x):
+    reveal_type(x)  # N: Revealed type is "builtins.int"
+[builtins fixtures/tuple.pyi]
+
+[case testTypeGuardTemporaryObjectWithKeywordArg]
+from typing_extensions import TypeGuard
+class E:
+    def __init__(self) -> None: ...
+    def __call__(self, o: object) -> TypeGuard[int]:
+        return True
+x = object()
+if E()(o=x):
+    reveal_type(x)  # N: Revealed type is "builtins.int"
+[builtins fixtures/tuple.pyi]
+
 [case testTypeGuardRestrictAwaySingleInvariant]
 from typing import List
 from typing_extensions import TypeGuard
@@ -813,3 +860,20 @@ raw_target: object
 if isinstance(raw_target, type) and is_xlike(raw_target):
     reveal_type(raw_target)  # N: Revealed type is "type[__main__.X]"
 [builtins fixtures/tuple.pyi]
+
+[case testTypeGuardWithDefer]
+from typing import Union
+from typing_extensions import TypeGuard
+
+class A: ...
+class B: ...
+
+def is_a(x: object) -> TypeGuard[A]:
+    return defer_not_defined()  # E: Name "defer_not_defined" is not defined
+
+def main(x: Union[A, B]) -> None:
+    if is_a(x):
+        reveal_type(x)  # N: Revealed type is "__main__.A"
+    else:
+        reveal_type(x)  # N: Revealed type is "Union[__main__.A, __main__.B]"
+[builtins fixtures/tuple.pyi]
diff --git a/test-data/unit/check-typeis.test b/test-data/unit/check-typeis.test
index bb8beac72c3a..2f54ac5bf5db 100644
--- a/test-data/unit/check-typeis.test
+++ b/test-data/unit/check-typeis.test
@@ -134,6 +134,91 @@ def main(a: object) -> None:
         reveal_type(a)  # N: Revealed type is "Union[builtins.int, builtins.str]"
 [builtins fixtures/tuple.pyi]
 
+[case testTypeIsUnionWithGeneric]
+from typing import Any, List, Sequence, Union
+from typing_extensions import TypeIs
+
+def is_int_list(a: object) -> TypeIs[List[int]]: pass
+def is_int_seq(a: object) -> TypeIs[Sequence[int]]: pass
+def is_seq(a: object) -> TypeIs[Sequence[Any]]: pass
+
+def f1(a: Union[List[int], List[str]]) -> None:
+    if is_int_list(a):
+        reveal_type(a)  # N: Revealed type is "builtins.list[builtins.int]"
+    else:
+        reveal_type(a)  # N: Revealed type is "builtins.list[builtins.str]"
+    reveal_type(a)  # N: Revealed type is "Union[builtins.list[builtins.int], builtins.list[builtins.str]]"
+
+def f2(a: Union[List[int], int]) -> None:
+    if is_int_list(a):
+        reveal_type(a)  # N: Revealed type is "builtins.list[builtins.int]"
+    else:
+        reveal_type(a)  # N: Revealed type is "builtins.int"
+    reveal_type(a)  # N: Revealed type is "Union[builtins.list[builtins.int], builtins.int]"
+
+def f3(a: Union[List[bool], List[str]]) -> None:
+    if is_int_seq(a):
+        reveal_type(a)  # N: Revealed type is "builtins.list[builtins.bool]"
+    else:
+        reveal_type(a)  # N: Revealed type is "builtins.list[builtins.str]"
+    reveal_type(a)  # N: Revealed type is "Union[builtins.list[builtins.bool], builtins.list[builtins.str]]"
+
+def f4(a: Union[List[int], int]) -> None:
+    if is_seq(a):
+        reveal_type(a)  # N: Revealed type is "builtins.list[builtins.int]"
+    else:
+        reveal_type(a)  # N: Revealed type is "builtins.int"
+    reveal_type(a)  # N: Revealed type is "Union[builtins.list[builtins.int], builtins.int]"
+[builtins fixtures/tuple.pyi]
+
+[case testTypeIsTupleGeneric]
+# flags: --warn-unreachable
+from __future__ import annotations
+from typing_extensions import TypeIs, Unpack
+
+class A: ...
+class B: ...
+
+def is_tuple_of_B(v: tuple[A | B, ...]) -> TypeIs[tuple[B, ...]]: ...
+
+def test1(t: tuple[A]) -> None:
+    if is_tuple_of_B(t):
+        reveal_type(t)  # E: Statement is unreachable
+    else:
+        reveal_type(t)  # N: Revealed type is "tuple[__main__.A]"
+
+def test2(t: tuple[B, A]) -> None:
+    if is_tuple_of_B(t):
+        reveal_type(t)  # E: Statement is unreachable
+    else:
+        reveal_type(t)  # N: Revealed type is "tuple[__main__.B, __main__.A]"
+
+def test3(t: tuple[A | B]) -> None:
+    if is_tuple_of_B(t):
+        reveal_type(t)  # N: Revealed type is "tuple[__main__.B]"
+    else:
+        reveal_type(t)  # N: Revealed type is "tuple[Union[__main__.A, __main__.B]]"
+
+def test4(t: tuple[A | B, A | B]) -> None:
+    if is_tuple_of_B(t):
+        reveal_type(t)  # N: Revealed type is "tuple[__main__.B, __main__.B]"
+    else:
+        reveal_type(t)  # N: Revealed type is "tuple[Union[__main__.A, __main__.B], Union[__main__.A, __main__.B]]"
+
+def test5(t: tuple[A | B, ...]) -> None:
+    if is_tuple_of_B(t):
+        reveal_type(t)  # N: Revealed type is "builtins.tuple[__main__.B, ...]"
+    else:
+        reveal_type(t)  # N: Revealed type is "builtins.tuple[Union[__main__.A, __main__.B], ...]"
+
+def test6(t: tuple[B, Unpack[tuple[A | B, ...]], B]) -> None:
+    if is_tuple_of_B(t):
+        # Should this be tuple[B, *tuple[B, ...], B]
+        reveal_type(t)  # N: Revealed type is "tuple[__main__.B, Never, __main__.B]"
+    else:
+        reveal_type(t)  # N: Revealed type is "tuple[__main__.B, Unpack[builtins.tuple[Union[__main__.A, __main__.B], ...]], __main__.B]"
+[builtins fixtures/tuple.pyi]
+
 [case testTypeIsNonzeroFloat]
 from typing_extensions import TypeIs
 def is_nonzero(a: object) -> TypeIs[float]: pass
@@ -834,3 +919,34 @@ def handle(model: Model) -> None:
     if is_model_a(model):
         reveal_type(model)  # N: Revealed type is "Literal[__main__.Model.A]"
 [builtins fixtures/tuple.pyi]
+
+[case testTypeIsAwaitableAny]
+from __future__ import annotations
+from typing import Any, Awaitable, Callable
+from typing_extensions import TypeIs
+
+def is_async_callable(obj: Any) -> TypeIs[Callable[..., Awaitable[Any]]]: ...
+
+def main(f: Callable[[], int | Awaitable[int]]) -> None:
+    if is_async_callable(f):
+        reveal_type(f)  # N: Revealed type is "def (*Any, **Any) -> typing.Awaitable[Any]"
+    else:
+        reveal_type(f)  # N: Revealed type is "def () -> Union[builtins.int, typing.Awaitable[builtins.int]]"
+[builtins fixtures/tuple.pyi]
+
+[case testTypeIsWithDefer]
+from typing import Union
+from typing_extensions import TypeIs
+
+class A: ...
+class B: ...
+
+def is_a(x: object) -> TypeIs[A]:
+    return defer_not_defined()  # E: Name "defer_not_defined" is not defined
+
+def main(x: Union[A, B]) -> None:
+    if is_a(x):
+        reveal_type(x)  # N: Revealed type is "__main__.A"
+    else:
+        reveal_type(x)  # N: Revealed type is "__main__.B"
+[builtins fixtures/tuple.pyi]
diff --git a/test-data/unit/check-typevar-tuple.test b/test-data/unit/check-typevar-tuple.test
index 0f69d0a56f47..c668f14eaa50 100644
--- a/test-data/unit/check-typevar-tuple.test
+++ b/test-data/unit/check-typevar-tuple.test
@@ -123,7 +123,7 @@ reveal_type(empty)  # N: Revealed type is "__main__.Variadic[()]"
 omitted: Variadic
 reveal_type(omitted)  # N: Revealed type is "__main__.Variadic[Unpack[builtins.tuple[Any, ...]]]"
 
-bad: Variadic[Unpack[Tuple[int, ...]], str, Unpack[Tuple[bool, ...]]]  # E: More than one Unpack in a type is not allowed
+bad: Variadic[Unpack[Tuple[int, ...]], str, Unpack[Tuple[bool, ...]]]  # E: More than one variadic Unpack in a type is not allowed
 reveal_type(bad)  # N: Revealed type is "__main__.Variadic[Unpack[builtins.tuple[builtins.int, ...]], builtins.str]"
 
 bad2: Unpack[Tuple[int, ...]]  # E: Unpack is only valid in a variadic position
@@ -353,12 +353,12 @@ expect_variadic_array_2(u)
 Ts = TypeVarTuple("Ts")
 Ts2 = TypeVarTuple("Ts2")
 
-def bad(x: Tuple[int, Unpack[Ts], str, Unpack[Ts2]]) -> None: # E: More than one Unpack in a type is not allowed
+def bad(x: Tuple[int, Unpack[Ts], str, Unpack[Ts2]]) -> None: # E: More than one variadic Unpack in a type is not allowed
 
     ...
 reveal_type(bad)  # N: Revealed type is "def [Ts, Ts2] (x: tuple[builtins.int, Unpack[Ts`-1], builtins.str])"
 
-def bad2(x: Tuple[int, Unpack[Tuple[int, ...]], str, Unpack[Tuple[str, ...]]]) -> None:  # E: More than one Unpack in a type is not allowed
+def bad2(x: Tuple[int, Unpack[Tuple[int, ...]], str, Unpack[Tuple[str, ...]]]) -> None:  # E: More than one variadic Unpack in a type is not allowed
     ...
 reveal_type(bad2)  # N: Revealed type is "def (x: tuple[builtins.int, Unpack[builtins.tuple[builtins.int, ...]], builtins.str])"
 [builtins fixtures/tuple.pyi]
@@ -571,7 +571,7 @@ from typing_extensions import Unpack, TypeVarTuple
 
 Ts = TypeVarTuple("Ts")
 Us = TypeVarTuple("Us")
-a: Callable[[Unpack[Ts], Unpack[Us]], int]  # E: More than one Unpack in a type is not allowed
+a: Callable[[Unpack[Ts], Unpack[Us]], int]  # E: More than one variadic Unpack in a type is not allowed
 reveal_type(a)  # N: Revealed type is "def [Ts, Us] (*Unpack[Ts`-1]) -> builtins.int"
 b: Callable[[Unpack], int]  # E: Unpack[...] requires exactly one type argument
 reveal_type(b)  # N: Revealed type is "def (*Any) -> builtins.int"
@@ -725,15 +725,15 @@ Ts = TypeVarTuple("Ts")
 Us = TypeVarTuple("Us")
 class G(Generic[Unpack[Ts]]): ...
 
-A = Tuple[Unpack[Ts], Unpack[Us]]  # E: More than one Unpack in a type is not allowed
+A = Tuple[Unpack[Ts], Unpack[Us]]  # E: More than one variadic Unpack in a type is not allowed
 x: A[int, str]
 reveal_type(x)  # N: Revealed type is "tuple[builtins.int, builtins.str]"
 
-B = Callable[[Unpack[Ts], Unpack[Us]], int]  # E: More than one Unpack in a type is not allowed
+B = Callable[[Unpack[Ts], Unpack[Us]], int]  # E: More than one variadic Unpack in a type is not allowed
 y: B[int, str]
 reveal_type(y)  # N: Revealed type is "def (builtins.int, builtins.str) -> builtins.int"
 
-C = G[Unpack[Ts], Unpack[Us]]  # E: More than one Unpack in a type is not allowed
+C = G[Unpack[Ts], Unpack[Us]]  # E: More than one variadic Unpack in a type is not allowed
 z: C[int, str]
 reveal_type(z)  # N: Revealed type is "__main__.G[builtins.int, builtins.str]"
 [builtins fixtures/tuple.pyi]
@@ -886,7 +886,6 @@ reveal_type(z)  # N: Revealed type is "tuple[builtins.int, Unpack[builtins.tuple
 [builtins fixtures/tuple.pyi]
 
 [case testInferenceAgainstGenericVariadicWithBadType]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, Generic
 from typing_extensions import Unpack, TypeVarTuple
 
@@ -989,7 +988,7 @@ from typing_extensions import Unpack
 
 def pipeline(*xs: Unpack[Tuple[int, Unpack[Tuple[float, ...]], bool]]) -> None:
     for x in xs:
-        reveal_type(x)  # N: Revealed type is "Union[builtins.float, builtins.int]"
+        reveal_type(x)  # N: Revealed type is "Union[builtins.int, builtins.float]"
 [builtins fixtures/tuple.pyi]
 
 [case testFixedUnpackItemInInstanceArguments]
@@ -2224,12 +2223,12 @@ cb2(1, 2, 3, a="a", b="b")
 cb2(1, a="a", b="b")  # E: Too few arguments
 cb2(1, 2, 3, a="a")  # E: Missing named argument "b"
 
-bad1: Callable[[Unpack[Ints], Unpack[Ints]], None]  # E: More than one Unpack in a type is not allowed
+bad1: Callable[[Unpack[Ints], Unpack[Ints]], None]  # E: More than one variadic Unpack in a type is not allowed
 reveal_type(bad1)  # N: Revealed type is "def (*builtins.int)"
 bad2: Callable[[Unpack[Keywords], Unpack[Keywords]], None]  # E: "Keywords" cannot be unpacked (must be tuple or TypeVarTuple)
 reveal_type(bad2)  # N: Revealed type is "def (*Any, **Unpack[TypedDict('__main__.Keywords', {'a': builtins.str, 'b': builtins.str})])"
 bad3: Callable[[Unpack[Keywords], Unpack[Ints]], None]  # E: "Keywords" cannot be unpacked (must be tuple or TypeVarTuple) \
-                                                        # E: More than one Unpack in a type is not allowed
+                                                        # E: More than one variadic Unpack in a type is not allowed
 reveal_type(bad3)  # N: Revealed type is "def (*Any)"
 [builtins fixtures/dict.pyi]
 [typing fixtures/typing-typeddict.pyi]
@@ -2372,9 +2371,9 @@ def pointwise_multiply(x: Array[Unpack[Ts]], y: Array[Unpack[Ts]]) -> Array[Unpa
 
 def a1(x: Array[int], y: Array[str], z: Array[int, str]) -> None:
     reveal_type(pointwise_multiply(x, x))  # N: Revealed type is "__main__.Array[builtins.int]"
-    reveal_type(pointwise_multiply(x, y))  # E: Cannot infer type argument 1 of "pointwise_multiply" \
+    reveal_type(pointwise_multiply(x, y))  # E: Cannot infer value of type parameter "Ts" of "pointwise_multiply" \
                                            # N: Revealed type is "__main__.Array[Unpack[builtins.tuple[Any, ...]]]"
-    reveal_type(pointwise_multiply(x, z))  # E: Cannot infer type argument 1 of "pointwise_multiply" \
+    reveal_type(pointwise_multiply(x, z))  # E: Cannot infer value of type parameter "Ts" of "pointwise_multiply" \
                                            # N: Revealed type is "__main__.Array[Unpack[builtins.tuple[Any, ...]]]"
 
 def func(x: Array[Unpack[Ts]], *args: Unpack[Ts]) -> Tuple[Unpack[Ts]]:
@@ -2382,9 +2381,9 @@ def func(x: Array[Unpack[Ts]], *args: Unpack[Ts]) -> Tuple[Unpack[Ts]]:
 
 def a2(x: Array[int, str]) -> None:
     reveal_type(func(x, 2, "Hello"))  # N: Revealed type is "tuple[builtins.int, builtins.str]"
-    reveal_type(func(x, 2))           # E: Cannot infer type argument 1 of "func" \
+    reveal_type(func(x, 2))           # E: Cannot infer value of type parameter "Ts" of "func" \
                                       # N: Revealed type is "builtins.tuple[Any, ...]"
-    reveal_type(func(x, 2, "Hello", True))   # E: Cannot infer type argument 1 of "func" \
+    reveal_type(func(x, 2, "Hello", True))   # E: Cannot infer value of type parameter "Ts" of "func" \
                                              # N: Revealed type is "builtins.tuple[Any, ...]"
 [builtins fixtures/tuple.pyi]
 
@@ -2628,3 +2627,68 @@ def fn(f: Callable[[*tuple[T]], int]) -> Callable[[*tuple[T]], int]: ...
 def test(*args: Unpack[tuple[T]]) -> int: ...
 reveal_type(fn(test))  # N: Revealed type is "def [T] (T`1) -> builtins.int"
 [builtins fixtures/tuple.pyi]
+
+[case testNoGenericTypeVarTupleClassVarAccess]
+from typing import Generic, Tuple, TypeVarTuple, Unpack
+
+Ts = TypeVarTuple("Ts")
+class C(Generic[Unpack[Ts]]):
+    x: Tuple[Unpack[Ts]]
+
+reveal_type(C.x)  # E: Access to generic instance variables via class is ambiguous \
+                  # N: Revealed type is "builtins.tuple[Any, ...]"
+
+class Bad(C[int, int]):
+    pass
+reveal_type(Bad.x)  # E: Access to generic instance variables via class is ambiguous \
+                    # N: Revealed type is "tuple[builtins.int, builtins.int]"
+reveal_type(Bad().x)  # N: Revealed type is "tuple[builtins.int, builtins.int]"
+
+class Good(C[int, int]):
+    x = (1, 1)
+reveal_type(Good.x)  # N: Revealed type is "tuple[builtins.int, builtins.int]"
+reveal_type(Good().x)  # N: Revealed type is "tuple[builtins.int, builtins.int]"
+[builtins fixtures/tuple.pyi]
+
+[case testConstraintsIncludeTupleFallback]
+from typing import Generic, TypeVar
+from typing_extensions import TypeVarTuple, Unpack
+
+T = TypeVar("T")
+Ts = TypeVarTuple("Ts")
+_FT = TypeVar("_FT", bound=type)
+
+def identity(smth: _FT) -> _FT:
+    return smth
+
+@identity
+class S(tuple[Unpack[Ts]], Generic[T, Unpack[Ts]]):
+    def f(self, x: T, /) -> T: ...
+[builtins fixtures/tuple.pyi]
+
+[case testNoCrashSubclassingTupleWithTrivialUnpack]
+# https://github.com/python/mypy/issues/19105
+from typing import Unpack
+
+class A(tuple[Unpack[tuple[int]]]): ...
+class B(tuple[Unpack[tuple[()]]]): ...
+
+a: A
+reveal_type(tuple(a))  # N: Revealed type is "builtins.tuple[builtins.int, ...]"
+(x,) = a
+
+b: B
+(_,) = b  # E: Need more than 0 values to unpack (1 expected)
+[builtins fixtures/tuple.pyi]
+
+[case testNoCrashSubclassingTupleWithVariadicUnpack]
+# https://github.com/python/mypy/issues/19105
+from typing import Unpack
+
+class A(tuple[Unpack[tuple[int, ...]]]): ...
+
+a: A
+tuple(a)
+(x,) = a
+(_,) = a
+[builtins fixtures/tuple.pyi]
diff --git a/test-data/unit/check-union-error-syntax.test b/test-data/unit/check-union-error-syntax.test
index 3c541173a891..e938598aaefe 100644
--- a/test-data/unit/check-union-error-syntax.test
+++ b/test-data/unit/check-union-error-syntax.test
@@ -55,3 +55,25 @@ from typing import Literal, Union
 x : Union[Literal[1], None]
 x = 3 # E: Incompatible types in assignment (expression has type "Literal[3]", variable has type "Optional[Literal[1]]")
 [builtins fixtures/tuple.pyi]
+
+[case testUnionSyntaxRecombined]
+# flags: --python-version 3.10 --force-union-syntax --allow-redefinition-new --local-partial-types
+# The following revealed type is recombined because the finally body is visited twice.
+try:
+    x = 1
+    x = ""
+    x = {1: ""}
+finally:
+    reveal_type(x)  # N: Revealed type is "Union[builtins.int, builtins.str, builtins.dict[builtins.int, builtins.str]]"
+[builtins fixtures/isinstancelist.pyi]
+
+[case testOrSyntaxRecombined]
+# flags: --python-version 3.10 --no-force-union-syntax --allow-redefinition-new --local-partial-types
+# The following revealed type is recombined because the finally body is visited twice.
+try:
+    x = 1
+    x = ""
+    x = {1: ""}
+finally:
+    reveal_type(x)  # N: Revealed type is "builtins.int | builtins.str | builtins.dict[builtins.int, builtins.str]"
+[builtins fixtures/isinstancelist.pyi]
diff --git a/test-data/unit/check-unions.test b/test-data/unit/check-unions.test
index f8c894a7957b..398b007ce57d 100644
--- a/test-data/unit/check-unions.test
+++ b/test-data/unit/check-unions.test
@@ -1345,3 +1345,30 @@ x: Union[C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11]
 y: Union[C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, None]
 x = y  # E: Incompatible types in assignment (expression has type "Union[C1, C2, C3, C4, C5, <6 more items>, None]", variable has type "Union[C1, C2, C3, C4, C5, <6 more items>]") \
        # N: Item in the first union not in the second: "None"
+
+[case testTypeAliasWithOldUnionIsInstance]
+# flags: --python-version 3.10
+from typing import Union
+SimpleAlias = Union[int, str]
+
+def foo(x: Union[int, str, tuple]):
+    # TODO: fix the typeshed stub for isinstance
+    if isinstance(x, SimpleAlias):  # E: Argument 2 to "isinstance" has incompatible type "<typing special form>"; expected "type"
+        reveal_type(x)  # N: Revealed type is "Union[builtins.int, builtins.str, builtins.tuple[Any, ...]]"
+    else:
+        reveal_type(x)  # N: Revealed type is "Union[builtins.int, builtins.str, builtins.tuple[Any, ...]]"
+[builtins fixtures/tuple.pyi]
+
+
+[case testTypeAliasWithOldUnionIsInstancePython39]
+# flags: --python-version 3.9
+from typing import Union
+SimpleAlias = Union[int, str]
+
+def foo(x: Union[int, str, tuple]):
+    if isinstance(x, SimpleAlias):  # E: Parameterized generics cannot be used with class or instance checks \
+                                    # E: Argument 2 to "isinstance" has incompatible type "<typing special form>"; expected "type"
+        reveal_type(x)  # N: Revealed type is "Union[builtins.int, builtins.str, builtins.tuple[Any, ...]]"
+    else:
+        reveal_type(x)  # N: Revealed type is "Union[builtins.int, builtins.str, builtins.tuple[Any, ...]]"
+[builtins fixtures/tuple.pyi]
diff --git a/test-data/unit/check-unreachable-code.test b/test-data/unit/check-unreachable-code.test
index 368431127b76..645f81e89ca1 100644
--- a/test-data/unit/check-unreachable-code.test
+++ b/test-data/unit/check-unreachable-code.test
@@ -778,6 +778,22 @@ assert sys.platform == 'lol'
 def bar() -> None: pass
 [builtins fixtures/ops.pyi]
 
+[case testUnreachableAfterToplevelAssertImportThirdParty]
+# flags: --platform unknown
+import sys
+assert sys.platform == 'linux'
+import does_not_exist
+[builtins fixtures/ops.pyi]
+
+[case testUnreachableAfterToplevelAssertImportThirdParty2]
+# flags: --platform unknown
+import sys
+import bad; assert sys.platform == 'linux'; import does_not_exist
+[builtins fixtures/ops.pyi]
+[out]
+main:3: error: Cannot find implementation or library stub for module named "bad"
+main:3: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
+
 [case testUnreachableAfterToplevelAssertNotInsideIf]
 import sys
 if sys.version_info[0] >= 2:
@@ -1587,3 +1603,19 @@ x = 0  # not unreachable
 
 f2: Callable[[], NoReturn] = lambda: foo()
 x = 0  # not unreachable
+
+[case testAttributeNoReturn]
+# flags: --warn-unreachable
+from typing import Optional, NoReturn, TypeVar
+
+def foo() -> NoReturn:
+    raise
+
+T = TypeVar("T")
+def bar(x: Optional[list[T]] = None) -> T:
+    ...
+
+reveal_type(bar().attr)  # N: Revealed type is "Never"
+1  # not unreachable
+reveal_type(foo().attr)  # N: Revealed type is "Never"
+1  # E: Statement is unreachable
diff --git a/test-data/unit/cmdline.pyproject.test b/test-data/unit/cmdline.pyproject.test
index f9691ba245f9..68dfacb372fb 100644
--- a/test-data/unit/cmdline.pyproject.test
+++ b/test-data/unit/cmdline.pyproject.test
@@ -226,3 +226,14 @@ y: int = 'y'  # E: Incompatible types in assignment (expression has type "str",
 # This should not trigger any errors, because it is not included:
 z: int = 'z'
 [out]
+
+[case testPyprojectTOMLSettingOfWrongType]
+# cmd: mypy a.py
+[file pyproject.toml]
+\[tool.mypy]
+enable_error_code = true
+[file a.py]
+x: int = 1
+[out]
+pyproject.toml: [mypy]: enable_error_code: Expected a list or a stringified version thereof, but got: 'True', of type bool.
+== Return code: 0
diff --git a/test-data/unit/cmdline.test b/test-data/unit/cmdline.test
index aa0c8916ba0f..ff60c24b72a5 100644
--- a/test-data/unit/cmdline.test
+++ b/test-data/unit/cmdline.test
@@ -1249,14 +1249,6 @@ note: A user-defined top-level module with name "typing" is not supported
 Failed to find builtin module mypy_extensions, perhaps typeshed is broken?
 == Return code: 2
 
-[case testNewTypeInferenceFlagDeprecated]
-# cmd: mypy --new-type-inference a.py
-[file a.py]
-pass
-[out]
-Warning: --new-type-inference flag is deprecated; new type inference algorithm is already enabled by default
-== Return code: 0
-
 [case testCustomTypeshedDirFilePassedExplicitly]
 # cmd: mypy --custom-typeshed-dir dir m.py dir/stdlib/foo.pyi
 [file m.py]
diff --git a/test-data/unit/daemon.test b/test-data/unit/daemon.test
index ad3b51b27dfb..295eb4000d81 100644
--- a/test-data/unit/daemon.test
+++ b/test-data/unit/daemon.test
@@ -648,6 +648,143 @@ from demo.test import a
 [file demo/test.py]
 a: int
 
+[case testUnusedTypeIgnorePreservedOnRerun]
+-- Regression test for https://github.com/python/mypy/issues/9655
+$ dmypy start -- --warn-unused-ignores --no-error-summary --hide-error-codes
+Daemon started
+$ dmypy check -- bar.py
+bar.py:2: error: Unused "type: ignore" comment
+== Return code: 1
+$ dmypy check -- bar.py
+bar.py:2: error: Unused "type: ignore" comment
+== Return code: 1
+
+[file foo/__init__.py]
+[file foo/empty.py]
+[file bar.py]
+from foo.empty import *
+a = 1  # type: ignore
+
+[case testTypeIgnoreWithoutCodePreservedOnRerun]
+-- Regression test for https://github.com/python/mypy/issues/9655
+$ dmypy start -- --enable-error-code ignore-without-code --no-error-summary
+Daemon started
+$ dmypy check -- bar.py
+bar.py:2: error: "type: ignore" comment without error code  [ignore-without-code]
+== Return code: 1
+$ dmypy check -- bar.py
+bar.py:2: error: "type: ignore" comment without error code  [ignore-without-code]
+== Return code: 1
+
+[file foo/__init__.py]
+[file foo/empty.py]
+[file bar.py]
+from foo.empty import *
+a = 1  # type: ignore
+
+[case testPossiblyUndefinedVarsPreservedAfterRerun]
+-- Regression test for https://github.com/python/mypy/issues/9655
+$ dmypy start -- --enable-error-code possibly-undefined --no-error-summary
+Daemon started
+$ dmypy check -- bar.py
+bar.py:4: error: Name "a" may be undefined  [possibly-undefined]
+== Return code: 1
+$ dmypy check -- bar.py
+bar.py:4: error: Name "a" may be undefined  [possibly-undefined]
+== Return code: 1
+
+[file foo/__init__.py]
+[file foo/empty.py]
+[file bar.py]
+from foo.empty import *
+if False:
+    a = 1
+a
+
+[case testUnusedTypeIgnorePreservedOnRerunWithIgnoredMissingImports]
+$ dmypy start -- --no-error-summary --ignore-missing-imports --warn-unused-ignores
+Daemon started
+$ dmypy check foo
+foo/main.py:3: error: Unused "type: ignore" comment  [unused-ignore]
+== Return code: 1
+$ dmypy check foo
+foo/main.py:3: error: Unused "type: ignore" comment  [unused-ignore]
+== Return code: 1
+
+[file unused/__init__.py]
+[file unused/submodule.py]
+[file foo/empty.py]
+[file foo/__init__.py]
+from foo.main import *
+from unused.submodule import *
+[file foo/main.py]
+from foo import empty
+from foo.does_not_exist import *
+a = 1  # type: ignore
+
+[case testModuleDoesNotExistPreservedOnRerun]
+$ dmypy start -- --no-error-summary --ignore-missing-imports
+Daemon started
+$ dmypy check foo
+foo/main.py:1: error: Module "foo" has no attribute "does_not_exist"  [attr-defined]
+== Return code: 1
+$ dmypy check foo
+foo/main.py:1: error: Module "foo" has no attribute "does_not_exist"  [attr-defined]
+== Return code: 1
+
+[file unused/__init__.py]
+[file unused/submodule.py]
+[file foo/__init__.py]
+from foo.main import *
+[file foo/main.py]
+from foo import does_not_exist
+from unused.submodule import *
+
+[case testReturnTypeIgnoreAfterUnknownImport]
+-- Return type ignores after unknown imports and unused modules are respected on the second pass.
+$ dmypy start -- --warn-unused-ignores --no-error-summary
+Daemon started
+$ dmypy check -- foo.py
+foo.py:2: error: Cannot find implementation or library stub for module named "a_module_which_does_not_exist"  [import-not-found]
+foo.py:2: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
+== Return code: 1
+$ dmypy check -- foo.py
+foo.py:2: error: Cannot find implementation or library stub for module named "a_module_which_does_not_exist"  [import-not-found]
+foo.py:2: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
+== Return code: 1
+
+[file unused/__init__.py]
+[file unused/empty.py]
+[file foo.py]
+from unused.empty import *
+import a_module_which_does_not_exist
+def is_foo() -> str:
+    return True  # type: ignore
+
+[case testAttrsTypeIgnoreAfterUnknownImport]
+$ dmypy start -- --warn-unused-ignores --no-error-summary
+Daemon started
+$ dmypy check -- foo.py
+foo.py:3: error: Cannot find implementation or library stub for module named "a_module_which_does_not_exist"  [import-not-found]
+foo.py:3: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
+== Return code: 1
+$ dmypy check -- foo.py
+foo.py:3: error: Cannot find implementation or library stub for module named "a_module_which_does_not_exist"  [import-not-found]
+foo.py:3: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
+== Return code: 1
+
+[file unused/__init__.py]
+[file unused/empty.py]
+[file foo.py]
+import attr
+from unused.empty import *
+import a_module_which_does_not_exist
+
+@attr.frozen
+class A:
+    def __init__(self) -> None:
+        self.__attrs_init__()  # type: ignore[attr-defined]
+
 [case testDaemonImportAncestors]
 $ dmypy run test.py
 Daemon started
diff --git a/test-data/unit/fine-grained-suggest.test b/test-data/unit/fine-grained-suggest.test
index 7034b5e48943..c2e544baf38b 100644
--- a/test-data/unit/fine-grained-suggest.test
+++ b/test-data/unit/fine-grained-suggest.test
@@ -207,6 +207,36 @@ foo(B())
 (baz.B) -> Tuple[foo.A, foo:A.C]
 ==
 
+[case testSuggestReexportNamingNameMatchesModule1]
+# suggest: foo.foo
+[file foo.py]
+import bar
+def foo():
+    return bar.bar()
+
+[file bar.py]
+class bar: ...  # name matches module name
+
+[out]
+() -> bar.bar
+==
+
+[case testSuggestReexportNamingNameMatchesModule2]
+# suggest: foo.foo
+[file foo.py]
+import bar
+import qux
+def foo():
+    return qux.bar()
+
+[file bar.py]
+[file qux.py]
+class bar: ...  # name matches another module name
+
+[out]
+() -> qux.bar
+==
+
 [case testSuggestInferInit]
 # suggest: foo.Foo.__init__
 [file foo.py]
@@ -651,6 +681,38 @@ foo3('hello hello')
 (str) -> str
 ==
 
+[case testSuggestInferFuncDecorator6]
+# suggest: foo.f
+[file foo.py]
+from __future__ import annotations
+
+from typing import Callable, Protocol, TypeVar
+from typing_extensions import ParamSpec
+
+P = ParamSpec('P')
+R = TypeVar('R')
+R_co = TypeVar('R_co', covariant=True)
+
+class Proto(Protocol[P, R_co]):
+    def __call__(self, *args: P.args, **kwargs: P.kwargs) -> R_co: ...
+
+def dec1(f: Callable[P, R]) -> Callable[P, R]: ...
+def dec2(f: Callable[..., R]) -> Callable[..., R]: ...
+def dec3(f: Proto[P, R_co]) -> Proto[P, R_co]: ...
+
+@dec1
+@dec2
+@dec3
+def f(x):
+    return x
+
+f('hi')
+
+[builtins fixtures/isinstancelist.pyi]
+[out]
+(str) -> str
+==
+
 [case testSuggestFlexAny1]
 # suggest: --flex-any=0.4 m.foo
 # suggest: --flex-any=0.7 m.foo
@@ -763,6 +825,26 @@ def bar(iany) -> None:
 (int) -> None
 ==
 
+[case testSuggestNewInit]
+# suggest: foo.F.__init__
+# suggest: foo.F.__new__
+[file foo.py]
+class F:
+    def __new__(cls, t):
+        return super().__new__(cls)
+
+    def __init__(self, t):
+        self.t = t
+
+[file bar.py]
+from foo import F
+def bar(iany) -> None:
+    F(0)
+[out]
+(int) -> None
+(int) -> Any
+==
+
 [case testSuggestColonBasic]
 # suggest: tmp/foo.py:1
 # suggest: tmp/bar/baz.py:2
diff --git a/test-data/unit/fine-grained.test b/test-data/unit/fine-grained.test
index 7e34a2352dd6..888b7bc7e97f 100644
--- a/test-data/unit/fine-grained.test
+++ b/test-data/unit/fine-grained.test
@@ -1720,7 +1720,7 @@ from typing import Iterator, Callable, List, Optional
 from a import f
 import a
 
-def dec(f: Callable[['A'], Optional[Iterator[int]]]) -> Callable[[int], int]: pass
+def dec(f: Callable[['A'], Optional[Iterator[int]]]) -> Callable[['A', int], int]: pass
 
 class A:
     @dec
@@ -2936,10 +2936,12 @@ a.py:6: error: Argument 1 to "f" has incompatible type "type[B]"; expected "M"
 
 [case testFineMetaclassRecalculation]
 import a
+
 [file a.py]
 from b import B
 class M2(type): pass
 class D(B, metaclass=M2): pass
+
 [file b.py]
 import c
 class B: pass
@@ -2949,27 +2951,31 @@ import c
 class B(metaclass=c.M): pass
 
 [file c.py]
-class M(type):
-    pass
+class M(type): pass
 [out]
 ==
 a.py:3: error: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases
+a.py:3: note: "a.M2" (metaclass of "a.D") conflicts with "c.M" (metaclass of "b.B")
 
 [case testFineMetaclassDeclaredUpdate]
 import a
+
 [file a.py]
 import b
 class B(metaclass=b.M): pass
 class D(B, metaclass=b.M2): pass
+
 [file b.py]
 class M(type): pass
 class M2(M): pass
+
 [file b.py.2]
 class M(type): pass
 class M2(type): pass
 [out]
 ==
 a.py:3: error: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases
+a.py:3: note: "b.M2" (metaclass of "a.D") conflicts with "b.M" (metaclass of "a.B")
 
 [case testFineMetaclassRemoveFromClass]
 import a
@@ -7306,9 +7312,7 @@ class C:
 ==
 mod.py:9: error: Incompatible types in assignment (expression has type "int", variable has type "str")
 
-[case testOverloadedMethodSupertype-only_when_cache]
--- Different cache/no-cache tests because
--- CallableType.def_extras.first_arg differs ("self"/None)
+[case testOverloadedMethodSupertype]
 from typing import overload, Any
 import b
 class Child(b.Parent):
@@ -7349,49 +7353,6 @@ main:4: note:          def f(self, arg: int) -> int
 main:4: note:          @overload
 main:4: note:          def f(self, arg: str) -> str
 
-[case testOverloadedMethodSupertype2-only_when_nocache]
--- Different cache/no-cache tests because
--- CallableType.def_extras.first_arg differs ("self"/None)
-from typing import overload, Any
-import b
-class Child(b.Parent):
-    @overload                           # Fail
-    def f(self, arg: int) -> int: ...
-    @overload
-    def f(self, arg: str) -> str: ...
-    def f(self, arg: Any) -> Any: ...
-[file b.py]
-from typing import overload, Any
-class C: pass
-class Parent:
-    @overload
-    def f(self, arg: int) -> int: ...
-    @overload
-    def f(self, arg: str) -> str: ...
-    def f(self, arg: Any) -> Any: ...
-[file b.py.2]
-from typing import overload, Any
-class C: pass
-class Parent:
-    @overload
-    def f(self, arg: int) -> int: ...
-    @overload
-    def f(self, arg: str) -> C: ...
-    def f(self, arg: Any) -> Any: ...
-[out]
-==
-main:4: error: Signature of "f" incompatible with supertype "b.Parent"
-main:4: note:      Superclass:
-main:4: note:          @overload
-main:4: note:          def f(self, arg: int) -> int
-main:4: note:          @overload
-main:4: note:          def f(self, arg: str) -> C
-main:4: note:      Subclass:
-main:4: note:          @overload
-main:4: note:          def f(arg: int) -> int
-main:4: note:          @overload
-main:4: note:          def f(arg: str) -> str
-
 [case testOverloadedInitSupertype]
 import a
 [file a.py]
@@ -8480,9 +8441,7 @@ class D:
 ==
 a.py:3: error: Cannot override final attribute "meth" (previously declared in base class "C")
 
-[case testFinalBodyReprocessedAndStillFinalOverloaded-only_when_cache]
--- Different cache/no-cache tests because
--- CallableType.def_extras.first_arg differs ("self"/None)
+[case testFinalBodyReprocessedAndStillFinalOverloaded]
 import a
 [file a.py]
 from c import C
@@ -8527,53 +8486,6 @@ a.py:3: note:          def meth(self, x: str) -> str
 a.py:3: note:      Subclass:
 a.py:3: note:          def meth(self) -> None
 
-[case testFinalBodyReprocessedAndStillFinalOverloaded2-only_when_nocache]
--- Different cache/no-cache tests because
--- CallableType.def_extras.first_arg differs ("self"/None)
-import a
-[file a.py]
-from c import C
-class A:
-    def meth(self) -> None: ...
-
-[file a.py.3]
-from c import C
-class A(C):
-    def meth(self) -> None: ...
-
-[file c.py]
-from typing import final, overload, Union
-from d import D
-
-class C:
-    @overload
-    def meth(self, x: int) -> int: ...
-    @overload
-    def meth(self, x: str) -> str: ...
-    @final
-    def meth(self, x: Union[int, str]) -> Union[int, str]:
-        D(int())
-        return x
-[file d.py]
-class D:
-    def __init__(self, x: int) -> None: ...
-[file d.py.2]
-from typing import Optional
-class D:
-    def __init__(self, x: Optional[int]) -> None: ...
-[out]
-==
-==
-a.py:3: error: Cannot override final attribute "meth" (previously declared in base class "C")
-a.py:3: error: Signature of "meth" incompatible with supertype "c.C"
-a.py:3: note:      Superclass:
-a.py:3: note:          @overload
-a.py:3: note:          def meth(x: int) -> int
-a.py:3: note:          @overload
-a.py:3: note:          def meth(x: str) -> str
-a.py:3: note:      Subclass:
-a.py:3: note:          def meth(self) -> None
-
 [case testIfMypyUnreachableClass]
 from a import x
 
@@ -10540,6 +10452,30 @@ from pkg.sub import modb
 [out]
 ==
 
+[case testUnusedTypeIgnorePreservedAfterChange]
+# flags: --warn-unused-ignores --no-error-summary
+[file main.py]
+a = 1  # type: ignore
+[file main.py.2]
+a = 1  # type: ignore
+# Comment to trigger reload.
+[out]
+main.py:1: error: Unused "type: ignore" comment
+==
+main.py:1: error: Unused "type: ignore" comment
+
+[case testTypeIgnoreWithoutCodePreservedAfterChange]
+# flags: --enable-error-code ignore-without-code --no-error-summary
+[file main.py]
+a = 1  # type: ignore
+[file main.py.2]
+a = 1  # type: ignore
+# Comment to trigger reload.
+[out]
+main.py:1: error: "type: ignore" comment without error code
+==
+main.py:1: error: "type: ignore" comment without error code
+
 [case testFineGrainedFunctoolsPartial]
 import m
 
@@ -11003,6 +10939,314 @@ b.py:1: error: class a.C is deprecated: use C2 instead
 b.py:2: error: class a.D is deprecated: use D2 instead
 
 
+[case testDeprecatedAddKeepChangeAndRemoveOverloadedFunctionDeprecation]
+# flags: --enable-error-code=deprecated
+
+from a import f
+f(1)
+f("y")
+import a
+a.f(1)
+a.f("y")
+
+[file a.py]
+from typing import overload, Union
+@overload
+def f(x: int) -> int: ...
+@overload
+def f(x: str) -> str: ...
+def f(x: Union[int, str]) -> Union[int, str]: ...
+
+[file a.py.2]
+from typing import overload, Union
+from typing_extensions import deprecated
+@overload
+def f(x: int) -> int: ...
+@overload
+@deprecated("pass int")
+def f(x: str) -> str: ...
+def f(x: Union[int, str]) -> Union[int, str]: ...
+
+[file a.py.3]
+from typing import overload, Union
+from typing_extensions import deprecated
+@overload
+def f(x: int) -> int: ...
+@overload
+@deprecated("pass int")
+def f(x: str) -> str: ...
+def f(x: Union[int, str]) -> Union[int, str]: ...
+
+[file a.py.4]
+from typing import overload, Union
+from typing_extensions import deprecated
+@overload
+def f(x: int) -> int: ...
+@overload
+@deprecated("pass int, please")
+def f(x: str) -> str: ...
+def f(x: Union[int, str]) -> Union[int, str]: ...
+
+[file a.py.5]
+from typing import overload, Union
+@overload
+def f(x: int) -> int: ...
+@overload
+def f(x: str) -> str: ...
+def f(x: Union[int, str]) -> Union[int, str]: ...
+
+[builtins fixtures/tuple.pyi]
+[out]
+==
+main:5: error: overload def (x: builtins.str) -> builtins.str of function a.f is deprecated: pass int
+main:8: error: overload def (x: builtins.str) -> builtins.str of function a.f is deprecated: pass int
+==
+main:5: error: overload def (x: builtins.str) -> builtins.str of function a.f is deprecated: pass int
+main:8: error: overload def (x: builtins.str) -> builtins.str of function a.f is deprecated: pass int
+==
+main:5: error: overload def (x: builtins.str) -> builtins.str of function a.f is deprecated: pass int, please
+main:8: error: overload def (x: builtins.str) -> builtins.str of function a.f is deprecated: pass int, please
+==
+
+
+[case testDeprecatedRemoveOverloadedFunctionDeprecation]
+# flags: --enable-error-code=deprecated
+
+from a import f
+f(1)
+f("y")
+import a
+a.f(1)
+a.f("y")
+
+[file a.py]
+from typing import overload, Union
+from typing_extensions import deprecated
+@overload
+def f(x: int) -> int: ...
+@overload
+@deprecated("pass int")
+def f(x: str) -> str: ...
+def f(x: Union[int, str]) -> Union[int, str]: ...
+
+[file a.py.2]
+from typing import overload, Union
+@overload
+def f(x: int) -> int: ...
+@overload
+def f(x: str) -> str: ...
+def f(x: Union[int, str]) -> Union[int, str]: ...
+
+[builtins fixtures/tuple.pyi]
+[out]
+main:5: error: overload def (x: builtins.str) -> builtins.str of function a.f is deprecated: pass int
+main:8: error: overload def (x: builtins.str) -> builtins.str of function a.f is deprecated: pass int
+==
+
+
+[case testDeprecatedKeepOverloadedFunctionDeprecation]
+# flags: --enable-error-code=deprecated
+
+from a import f
+f(1)
+f("y")
+import a
+a.f(1)
+a.f("y")
+
+[file a.py]
+from typing import overload, Union
+from typing_extensions import deprecated
+@overload
+def f(x: int) -> int: ...
+@overload
+@deprecated("pass int")
+def f(x: str) -> str: ...
+def f(x: Union[int, str]) -> Union[int, str]: ...
+
+[file a.py.2]
+from typing import overload, Union
+from typing_extensions import deprecated
+@overload
+def f(x: int) -> int: ...
+@overload
+@deprecated("pass int")
+def f(x: str) -> str: ...
+def f(x: Union[int, str]) -> Union[int, str]: ...
+
+[builtins fixtures/tuple.pyi]
+[out]
+main:5: error: overload def (x: builtins.str) -> builtins.str of function a.f is deprecated: pass int
+main:8: error: overload def (x: builtins.str) -> builtins.str of function a.f is deprecated: pass int
+==
+main:5: error: overload def (x: builtins.str) -> builtins.str of function a.f is deprecated: pass int
+main:8: error: overload def (x: builtins.str) -> builtins.str of function a.f is deprecated: pass int
+
+
+[case testDeprecatedAddOverloadedFunctionDeprecationIndirectImport]
+# flags: --enable-error-code=deprecated
+
+from b import f
+f(1)
+f("y")
+import b
+b.f(1)
+b.f("y")
+
+[file b.py]
+from a import f
+
+[file a.py]
+from typing import overload, Union
+@overload
+def f(x: int) -> int: ...
+@overload
+def f(x: str) -> str: ...
+def f(x: Union[int, str]) -> Union[int, str]: ...
+
+[file a.py.2]
+from typing import overload, Union
+from typing_extensions import deprecated
+@overload
+def f(x: int) -> int: ...
+@overload
+@deprecated("pass int")
+def f(x: str) -> str: ...
+def f(x: Union[int, str]) -> Union[int, str]: ...
+
+[builtins fixtures/tuple.pyi]
+[out]
+==
+main:5: error: overload def (x: builtins.str) -> builtins.str of function a.f is deprecated: pass int
+main:8: error: overload def (x: builtins.str) -> builtins.str of function a.f is deprecated: pass int
+
+
+[case testDeprecatedChangeOverloadedFunctionDeprecationIndirectImport]
+# flags: --enable-error-code=deprecated
+
+from b import f
+f(1)
+f("y")
+import b
+b.f(1)
+b.f("y")
+
+[file b.py]
+from a import f
+
+[file a.py]
+from typing import overload, Union
+from typing_extensions import deprecated
+@overload
+def f(x: int) -> int: ...
+@overload
+@deprecated("pass int")
+def f(x: str) -> str: ...
+def f(x: Union[int, str]) -> Union[int, str]: ...
+
+[file a.py.2]
+from typing import overload, Union
+from typing_extensions import deprecated
+@overload
+def f(x: int) -> int: ...
+@overload
+@deprecated("pass int, please")
+def f(x: str) -> str: ...
+def f(x: Union[int, str]) -> Union[int, str]: ...
+
+[builtins fixtures/tuple.pyi]
+[out]
+main:5: error: overload def (x: builtins.str) -> builtins.str of function a.f is deprecated: pass int
+main:8: error: overload def (x: builtins.str) -> builtins.str of function a.f is deprecated: pass int
+==
+main:5: error: overload def (x: builtins.str) -> builtins.str of function a.f is deprecated: pass int, please
+main:8: error: overload def (x: builtins.str) -> builtins.str of function a.f is deprecated: pass int, please
+
+
+[case testDeprecatedRemoveOverloadedFunctionDeprecationIndirectImport]
+# flags: --enable-error-code=deprecated
+
+from b import f
+f(1)
+f("y")
+import b
+b.f(1)
+b.f("y")
+
+[file b.py]
+from a import f
+
+[file a.py]
+from typing import overload, Union
+from typing_extensions import deprecated
+@overload
+def f(x: int) -> int: ...
+@overload
+@deprecated("pass int")
+def f(x: str) -> str: ...
+def f(x: Union[int, str]) -> Union[int, str]: ...
+
+[file a.py.2]
+from typing import overload, Union
+@overload
+def f(x: int) -> int: ...
+@overload
+def f(x: str) -> str: ...
+def f(x: Union[int, str]) -> Union[int, str]: ...
+
+[builtins fixtures/tuple.pyi]
+[out]
+main:5: error: overload def (x: builtins.str) -> builtins.str of function a.f is deprecated: pass int
+main:8: error: overload def (x: builtins.str) -> builtins.str of function a.f is deprecated: pass int
+==
+
+
+[case testDeprecatedOverloadedFunctionAlreadyDecorated]
+# flags: --enable-error-code=deprecated
+
+from b import f
+f(1)
+f("y")
+import b
+b.f(1)
+b.f("y")
+
+[file b.py]
+from a import f
+
+[file a.py]
+from typing import Callable, overload, Union
+
+def d(t: Callable[[str], str]) -> Callable[[str], str]: ...
+
+@overload
+def f(x: int) -> int: ...
+@overload
+@d
+def f(x: str) -> str: ...
+def f(x: Union[int, str]) -> Union[int, str]: ...
+
+[file a.py.2]
+from typing import Callable, overload, Union
+from typing_extensions import deprecated
+
+def d(t: Callable[[str], str]) -> Callable[[str], str]: ...
+
+@overload
+def f(x: int) -> int: ...
+@overload
+@deprecated("deprecated decorated overload")
+@d
+def f(x: str) -> str: ...
+def f(x: Union[int, str]) -> Union[int, str]: ...
+
+[builtins fixtures/tuple.pyi]
+[out]
+==
+main:5: error: overload def (x: builtins.str) -> builtins.str of function a.f is deprecated: deprecated decorated overload
+main:8: error: overload def (x: builtins.str) -> builtins.str of function a.f is deprecated: deprecated decorated overload
+
+
 [case testDeprecatedChangeClassDeprecationIndirectImport]
 # flags: --enable-error-code=deprecated
 from b import C
diff --git a/test-data/unit/fixtures/isinstancelist.pyi b/test-data/unit/fixtures/isinstancelist.pyi
index 0ee5258ff74b..2a43606f361a 100644
--- a/test-data/unit/fixtures/isinstancelist.pyi
+++ b/test-data/unit/fixtures/isinstancelist.pyi
@@ -26,6 +26,7 @@ class bool(int): pass
 class str:
     def __add__(self, x: str) -> str: pass
     def __getitem__(self, x: int) -> str: pass
+class bytes: pass
 
 T = TypeVar('T')
 KT = TypeVar('KT')
@@ -52,6 +53,7 @@ class dict(Mapping[KT, VT]):
     def __setitem__(self, k: KT, v: VT) -> None: pass
     def __iter__(self) -> Iterator[KT]: pass
     def update(self, a: Mapping[KT, VT]) -> None: pass
+    def items(self) -> Iterable[Tuple[KT, VT]]: pass
 
 class set(Generic[T]):
     def __iter__(self) -> Iterator[T]: pass
diff --git a/test-data/unit/lib-stub/_weakref.pyi b/test-data/unit/lib-stub/_weakref.pyi
new file mode 100644
index 000000000000..50c59b65e267
--- /dev/null
+++ b/test-data/unit/lib-stub/_weakref.pyi
@@ -0,0 +1,11 @@
+from typing import Any, Callable, TypeVar, overload
+from weakref import CallableProxyType, ProxyType
+
+_C = TypeVar("_C", bound=Callable[..., Any])
+_T = TypeVar("_T")
+
+# Return CallableProxyType if object is callable, ProxyType otherwise
+@overload
+def proxy(object: _C, callback: Callable[[CallableProxyType[_C]], Any] | None = None, /) -> CallableProxyType[_C]: ...
+@overload
+def proxy(object: _T, callback: Callable[[ProxyType[_T]], Any] | None = None, /) -> ProxyType[_T]: ...
diff --git a/test-data/unit/lib-stub/enum.pyi b/test-data/unit/lib-stub/enum.pyi
index ccb3818b9d25..5047f7083804 100644
--- a/test-data/unit/lib-stub/enum.pyi
+++ b/test-data/unit/lib-stub/enum.pyi
@@ -29,6 +29,7 @@ class Enum(metaclass=EnumMeta):
 
 class IntEnum(int, Enum):
     value: int
+    _value_: int
     def __new__(cls: Type[_T], value: Union[int, _T]) -> _T: ...
 
 def unique(enumeration: _T) -> _T: pass
@@ -36,6 +37,8 @@ def unique(enumeration: _T) -> _T: pass
 # In reality Flag and IntFlag are 3.6 only
 
 class Flag(Enum):
+    value: int
+    _value_: int
     def __or__(self: _T, other: Union[int, _T]) -> _T: pass
 
 
@@ -49,6 +52,8 @@ class auto(IntFlag):
 
 # It is python-3.11+ only:
 class StrEnum(str, Enum):
+    _value_: str
+    value: str
     def __new__(cls: Type[_T], value: str | _T) -> _T: ...
 
 # It is python-3.11+ only:
diff --git a/test-data/unit/lib-stub/native_internal.pyi b/test-data/unit/lib-stub/native_internal.pyi
new file mode 100644
index 000000000000..a47a4849fe20
--- /dev/null
+++ b/test-data/unit/lib-stub/native_internal.pyi
@@ -0,0 +1,16 @@
+from mypy_extensions import u8
+
+class Buffer:
+    def __init__(self, source: bytes = ...) -> None: ...
+    def getvalue(self) -> bytes: ...
+
+def write_bool(data: Buffer, value: bool) -> None: ...
+def read_bool(data: Buffer) -> bool: ...
+def write_str(data: Buffer, value: str) -> None: ...
+def read_str(data: Buffer) -> str: ...
+def write_float(data: Buffer, value: float) -> None: ...
+def read_float(data: Buffer) -> float: ...
+def write_int(data: Buffer, value: int) -> None: ...
+def read_int(data: Buffer) -> int: ...
+def write_tag(data: Buffer, value: u8) -> None: ...
+def read_tag(data: Buffer) -> u8: ...
diff --git a/test-data/unit/lib-stub/typing_extensions.pyi b/test-data/unit/lib-stub/typing_extensions.pyi
index cb054b0e6b4f..6158a0c9ebbc 100644
--- a/test-data/unit/lib-stub/typing_extensions.pyi
+++ b/test-data/unit/lib-stub/typing_extensions.pyi
@@ -93,5 +93,6 @@ def dataclass_transform(
 
 def override(__arg: _T) -> _T: ...
 def deprecated(__msg: str) -> Callable[[_T], _T]: ...
+def disjoint_base(__arg: _T) -> _T: ...
 
 _FutureFeatureFixture = 0
diff --git a/test-data/unit/lib-stub/weakref.pyi b/test-data/unit/lib-stub/weakref.pyi
new file mode 100644
index 000000000000..7d11b65d4548
--- /dev/null
+++ b/test-data/unit/lib-stub/weakref.pyi
@@ -0,0 +1,23 @@
+from _weakref import proxy
+from collections.abc import Callable
+from typing import Any, ClassVar, Generic, TypeVar, final
+from typing_extensions import Self
+
+_C = TypeVar("_C", bound=Callable[..., Any])
+_T = TypeVar("_T")
+
+class ReferenceType(Generic[_T]):  # "weakref"
+    __callback__: Callable[[Self], Any]
+    def __new__(cls, o: _T, callback: Callable[[Self], Any] | None = ..., /) -> Self: ...
+    def __call__(self) -> _T | None: ...
+
+ref = ReferenceType
+
+@final
+class CallableProxyType(Generic[_C]):  # "weakcallableproxy"
+    def __eq__(self, value: object, /) -> bool: ...
+    def __getattr__(self, attr: str) -> Any: ...
+    __call__: _C
+    __hash__: ClassVar[None]  # type: ignore[assignment]
+
+__all__ = ["proxy"]
diff --git a/test-data/unit/parse-python314.test b/test-data/unit/parse-python314.test
new file mode 100644
index 000000000000..34fe753084f6
--- /dev/null
+++ b/test-data/unit/parse-python314.test
@@ -0,0 +1,5 @@
+[case testTemplateString]
+x = 'mypy'
+t'Hello {x}'
+[out]
+main:2: error: PEP 750 template strings are not yet supported
diff --git a/test-data/unit/pythoneval.test b/test-data/unit/pythoneval.test
index 3cd509d44290..93b67bfa813a 100644
--- a/test-data/unit/pythoneval.test
+++ b/test-data/unit/pythoneval.test
@@ -797,7 +797,6 @@ _program.py:3: error: Dict entry 1 has incompatible type "str": "str"; expected
 _program.py:5: error: "dict[str, int]" has no attribute "xyz"
 
 [case testDefaultDict]
-# flags: --new-type-inference
 import typing as t
 from collections import defaultdict
 
@@ -823,11 +822,11 @@ class MyDDict(t.DefaultDict[int,T], t.Generic[T]):
 MyDDict(dict)['0']
 MyDDict(dict)[0]
 [out]
-_program.py:7: error: Argument 1 to "defaultdict" has incompatible type "type[list[_T]]"; expected "Optional[Callable[[], str]]"
-_program.py:10: error: Invalid index type "str" for "defaultdict[int, str]"; expected type "int"
-_program.py:10: error: Incompatible types in assignment (expression has type "int", target has type "str")
-_program.py:20: error: Argument 1 to "tst" has incompatible type "defaultdict[str, list[Never]]"; expected "defaultdict[int, list[Never]]"
-_program.py:24: error: Invalid index type "str" for "MyDDict[dict[Never, Never]]"; expected type "int"
+_program.py:6: error: Argument 1 to "defaultdict" has incompatible type "type[list[_T]]"; expected "Optional[Callable[[], str]]"
+_program.py:9: error: Invalid index type "str" for "defaultdict[int, str]"; expected type "int"
+_program.py:9: error: Incompatible types in assignment (expression has type "int", target has type "str")
+_program.py:19: error: Argument 1 to "tst" has incompatible type "defaultdict[str, list[Never]]"; expected "defaultdict[int, list[Never]]"
+_program.py:23: error: Invalid index type "str" for "MyDDict[dict[Never, Never]]"; expected type "int"
 
 [case testCollectionsAliases]
 import typing as t
@@ -1050,7 +1049,8 @@ _testTypedDictGet.py:8: note: Revealed type is "builtins.object"
 _testTypedDictGet.py:9: error: All overload variants of "get" of "Mapping" require at least one argument
 _testTypedDictGet.py:9: note: Possible overload variants:
 _testTypedDictGet.py:9: note:     def get(self, str, /) -> object
-_testTypedDictGet.py:9: note:     def [_T] get(self, str, /, default: object) -> object
+_testTypedDictGet.py:9: note:     def get(self, str, /, default: object) -> object
+_testTypedDictGet.py:9: note:     def [_T] get(self, str, /, default: _T) -> object
 _testTypedDictGet.py:11: note: Revealed type is "builtins.object"
 
 [case testTypedDictMappingMethods]
@@ -1479,9 +1479,9 @@ y: str
 if isinstance(x, int):
     reveal_type(x)
 [out]
-_testIsInstanceAdHocIntersectionWithStrAndBytes.py:3: error: Subclass of "str" and "bytes" cannot exist: would have incompatible method signatures
+_testIsInstanceAdHocIntersectionWithStrAndBytes.py:3: error: Subclass of "str" and "bytes" cannot exist: have distinct disjoint bases
 _testIsInstanceAdHocIntersectionWithStrAndBytes.py:4: error: Statement is unreachable
-_testIsInstanceAdHocIntersectionWithStrAndBytes.py:6: error: Subclass of "str" and "int" cannot exist: would have incompatible method signatures
+_testIsInstanceAdHocIntersectionWithStrAndBytes.py:6: error: Subclass of "str" and "int" cannot exist: have distinct disjoint bases
 _testIsInstanceAdHocIntersectionWithStrAndBytes.py:7: error: Statement is unreachable
 
 [case testAsyncioFutureWait]
@@ -1970,13 +1970,13 @@ a2 = replace()
 a2 = replace(a, x='spam')
 a2 = replace(a, x=42, q=42)
 [out]
+_testDataclassReplace.py:4: note: "replace" of "A" defined here
 _testDataclassReplace.py:9: note: Revealed type is "_testDataclassReplace.A"
 _testDataclassReplace.py:10: error: Too few arguments for "replace"
 _testDataclassReplace.py:11: error: Argument "x" to "replace" of "A" has incompatible type "str"; expected "int"
 _testDataclassReplace.py:12: error: Unexpected keyword argument "q" for "replace" of "A"
 
 [case testGenericInferenceWithTuple]
-# flags: --new-type-inference
 from typing import TypeVar, Callable, Tuple
 
 T = TypeVar("T")
@@ -1988,7 +1988,6 @@ x: Tuple[str, ...] = f(tuple)
 [out]
 
 [case testGenericInferenceWithDataclass]
-# flags: --new-type-inference
 from typing import Any, Collection, List
 from dataclasses import dataclass, field
 
@@ -2001,7 +2000,6 @@ class A:
 [out]
 
 [case testGenericInferenceWithItertools]
-# flags: --new-type-inference
 from typing import TypeVar, Tuple
 from itertools import groupby
 K = TypeVar("K")
@@ -2190,3 +2188,19 @@ reveal_type([*map(str, x)])
 [out]
 _testUnpackIteratorBuiltins.py:4: note: Revealed type is "builtins.list[builtins.int]"
 _testUnpackIteratorBuiltins.py:5: note: Revealed type is "builtins.list[builtins.str]"
+
+[case testReturnFallbackInferenceDict]
+# Requires full dict stubs.
+from typing import Dict, Mapping, TypeVar, Union
+
+K = TypeVar("K")
+V = TypeVar("V")
+K2 = TypeVar("K2")
+V2 = TypeVar("V2")
+
+def func(one: Dict[K, V], two: Mapping[K2, V2]) -> Dict[Union[K, K2], Union[V, V2]]:
+    ...
+
+def caller(arg1: Mapping[K, V], arg2: Mapping[K2, V2]) -> Dict[Union[K, K2], Union[V, V2]]:
+    _arg1 = arg1 if isinstance(arg1, dict) else dict(arg1)
+    return func(_arg1, arg2)
diff --git a/test-data/unit/semanal-classvar.test b/test-data/unit/semanal-classvar.test
index a7bcec0324dc..62151666c011 100644
--- a/test-data/unit/semanal-classvar.test
+++ b/test-data/unit/semanal-classvar.test
@@ -52,7 +52,7 @@ MypyFile:1(
     AssignmentStmt:3(
       NameExpr(x [m])
       IntExpr(1)
-      Any)))
+      builtins.int)))
 
 [case testClassVarWithTypeVar]
 
@@ -207,14 +207,3 @@ class B:
         pass
 [out]
 main:4: error: ClassVar can only be used for assignments in class body
-
-[case testClassVarWithTypeVariable]
-from typing import ClassVar, TypeVar, Generic, List
-
-T = TypeVar('T')
-
-class Some(Generic[T]):
-    error: ClassVar[T]  # E: ClassVar cannot contain type variables
-    nested: ClassVar[List[List[T]]]  # E: ClassVar cannot contain type variables
-    ok: ClassVar[int]
-[out]
diff --git a/test-data/unit/semanal-errors.test b/test-data/unit/semanal-errors.test
index fa5cec795931..8053b33b94fd 100644
--- a/test-data/unit/semanal-errors.test
+++ b/test-data/unit/semanal-errors.test
@@ -537,13 +537,6 @@ def f(y: t): x = t
 main:4: error: "t" is a type variable and only valid in type context
 main:5: error: "t" is a type variable and only valid in type context
 
-[case testMissingSelf]
-import typing
-class A:
-  def f(): pass
-[out]
-main:3: error: Method must have at least one argument. Did you forget the "self" argument?
-
 [case testInvalidBaseClass]
 import typing
 class A(B): pass
@@ -558,15 +551,6 @@ def f() -> None: super().y
 main:2: error: "super" used outside class
 main:3: error: "super" used outside class
 
-[case testMissingSelfInMethod]
-import typing
-class A:
-  def f() -> None: pass
-  def g(): pass
-[out]
-main:3: error: Method must have at least one argument. Did you forget the "self" argument?
-main:4: error: Method must have at least one argument. Did you forget the "self" argument?
-
 [case testMultipleMethodDefinition]
 import typing
 class A:
@@ -1015,6 +999,12 @@ class A(Generic[T]):
           # E: Free type variable expected in Generic[...]
 [out]
 
+[case testRedeclaredTypeVarWithinNestedGenericClass]
+from typing import Generic, Iterable, TypeVar
+T = TypeVar('T')
+class A(Generic[T]):
+    class B(Iterable[T]): pass  # E: Type variable "T" is bound by an outer class
+
 [case testIncludingGenericTwiceInBaseClassList]
 from typing import Generic, TypeVar
 T = TypeVar('T')
@@ -1230,7 +1220,7 @@ class A:
     @overload  # E: Decorators on top of @property are not supported
     @property
     def f(self) -> int: pass
-    @property  # E: Only supported top decorator is @f.setter
+    @property  # E: Only supported top decorators are "@f.setter" and "@f.deleter"
     @overload
     def f(self) -> int: pass
 [builtins fixtures/property.pyi]
diff --git a/test-requirements.in b/test-requirements.in
index 666dd9fc082c..df074965a1e8 100644
--- a/test-requirements.in
+++ b/test-requirements.in
@@ -5,7 +5,7 @@
 -r build-requirements.txt
 attrs>=18.0
 filelock>=3.3.0
-lxml>=5.3.0; python_version<'3.14'
+lxml>=5.3.0; python_version<'3.15'
 psutil>=4.0
 pytest>=8.1.0
 pytest-xdist>=1.34.0
diff --git a/test-requirements.txt b/test-requirements.txt
index bcdf02319306..521208c5aa27 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -1,5 +1,5 @@
 #
-# This file is autogenerated by pip-compile with Python 3.12
+# This file is autogenerated by pip-compile with Python 3.13
 # by the following command:
 #
 #    pip-compile --allow-unsafe --output-file=test-requirements.txt --strip-extras test-requirements.in
@@ -8,21 +8,21 @@ attrs==25.3.0
     # via -r test-requirements.in
 cfgv==3.4.0
     # via pre-commit
-coverage==7.8.2
+coverage==7.10.5
     # via pytest-cov
-distlib==0.3.9
+distlib==0.4.0
     # via virtualenv
 execnet==2.1.1
     # via pytest-xdist
-filelock==3.18.0
+filelock==3.19.1
     # via
     #   -r test-requirements.in
     #   virtualenv
-identify==2.6.12
+identify==2.6.13
     # via pre-commit
 iniconfig==2.1.0
     # via pytest
-lxml==5.4.0 ; python_version < "3.14"
+lxml==6.0.1 ; python_version < "3.15"
     # via -r test-requirements.in
 mypy-extensions==1.1.0
     # via -r mypy-requirements.txt
@@ -35,31 +35,35 @@ pathspec==0.12.1
 platformdirs==4.3.8
     # via virtualenv
 pluggy==1.6.0
-    # via pytest
-pre-commit==4.2.0
+    # via
+    #   pytest
+    #   pytest-cov
+pre-commit==4.3.0
     # via -r test-requirements.in
 psutil==7.0.0
     # via -r test-requirements.in
-pytest==8.3.5
+pygments==2.19.2
+    # via pytest
+pytest==8.4.1
     # via
     #   -r test-requirements.in
     #   pytest-cov
     #   pytest-xdist
-pytest-cov==6.1.1
+pytest-cov==6.2.1
     # via -r test-requirements.in
-pytest-xdist==3.7.0
+pytest-xdist==3.8.0
     # via -r test-requirements.in
 pyyaml==6.0.2
     # via pre-commit
 tomli==2.2.1
     # via -r test-requirements.in
-types-psutil==7.0.0.20250516
+types-psutil==7.0.0.20250822
     # via -r build-requirements.txt
-types-setuptools==80.8.0.20250521
+types-setuptools==80.9.0.20250822
     # via -r build-requirements.txt
-typing-extensions==4.13.2
+typing-extensions==4.14.1
     # via -r mypy-requirements.txt
-virtualenv==20.31.2
+virtualenv==20.34.0
     # via pre-commit
 
 # The following packages are considered to be unsafe in a requirements file: