diff --git a/Sources/Testing/Support/Additions/CommandLineAdditions.swift b/Sources/Testing/Support/Additions/CommandLineAdditions.swift
index 57d9851a8..99f4a1f0f 100644
--- a/Sources/Testing/Support/Additions/CommandLineAdditions.swift
+++ b/Sources/Testing/Support/Additions/CommandLineAdditions.swift
@@ -56,13 +56,10 @@ extension CommandLine {
         }
       }
 #elseif os(OpenBSD)
-      // OpenBSD does not have API to get a path to the running executable. Use
-      // arguments[0]. We do a basic sniff test for a path-like string, but
-      // otherwise return argv[0] verbatim.
-      guard let argv0 = arguments.first, argv0.contains("/") else {
+      guard let executablePath = swt_getExecutablePath().flatMap(String.init(validatingCString:)) else {
         throw CError(rawValue: ENOEXEC)
       }
-      return argv0
+      return executablePath
 #elseif os(Windows)
       var result: String?
 #if DEBUG
diff --git a/Sources/_TestingInternals/CMakeLists.txt b/Sources/_TestingInternals/CMakeLists.txt
index a951c7d4b..6dcd5622d 100644
--- a/Sources/_TestingInternals/CMakeLists.txt
+++ b/Sources/_TestingInternals/CMakeLists.txt
@@ -12,6 +12,7 @@ include(GitCommit)
 include(TargetTriple)
 add_library(_TestingInternals STATIC
   Discovery.cpp
+  Stubs.cpp
   Versions.cpp
   WillThrow.cpp)
 target_include_directories(_TestingInternals PUBLIC
diff --git a/Sources/_TestingInternals/Stubs.cpp b/Sources/_TestingInternals/Stubs.cpp
new file mode 100644
index 000000000..3dea9c109
--- /dev/null
+++ b/Sources/_TestingInternals/Stubs.cpp
@@ -0,0 +1,54 @@
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2023–2025 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for Swift project authors
+//
+
+#include "Stubs.h"
+
+#if defined(__OpenBSD__)
+#include <atomic>
+
+#include <sys/types.h>
+#include <sys/sysctl.h>
+
+// This function has the `__constructor__` attribute so that it runs as early as
+// possible, thus limiting the risk of some other code changing the current
+// working directory before we've had a chance to call realpath().
+__attribute__((__constructor__(101)))
+static void tryResolvingExecutablePath(void) {
+  // Call sysctl() to get the argument vector to the process.
+  int mib[2] = {CTL_VM, VM_PSSTRINGS};
+  struct _ps_strings _ps;
+  size_t len = sizeof(_ps);
+  if (sysctl(mib, 2, &_ps, &len, NULL, 0) == -1) {
+    return nullptr;
+  }
+
+  // Extract the first argument from the argument vector.
+  struct ps_strings *ps = static_cast<struct ps_strings *>(_ps.val);
+  if (ps->ps_nargvstr < 1) {
+    return nullptr;
+  }
+  const char *executablePath = ps->ps_argvstr[0];
+
+  // If the first argument looks path-like (because it contains a '/' character)
+  // then try to resolve it to an absolute path. Otherwise, return it verbatim.
+  // NOTE: we do not attempt to resolve $PATH-relative paths here because we
+  // don't expect test executables to be installed into e.g. /usr/local/bin.
+  if (strchr(executablePath, '/')) {
+    executablePath = realpath(executablePath, nullptr);
+  } else {
+    executablePath = strdup(executablePath);
+  }
+  executablePath.store(executablePath);
+}
+
+const char *swt_getExecutablePath(void) {
+  return executablePath.load();
+}
+#endif
diff --git a/Sources/_TestingInternals/include/Stubs.h b/Sources/_TestingInternals/include/Stubs.h
index 636ea9aff..e20cc38c9 100644
--- a/Sources/_TestingInternals/include/Stubs.h
+++ b/Sources/_TestingInternals/include/Stubs.h
@@ -126,6 +126,15 @@ static char *_Nullable *_Null_unspecified swt_environ(void) {
 }
 #endif
 
+#if defined(__OpenBSD__)
+/// Get the executable path.
+///
+/// This function is provided on OpenBSD because the platform does not provide
+/// an interface for getting the executable path, so we must simulate it in a
+/// way that is not supported in Swift.
+SWT_EXTERN const char *_Nullable swt_getExecutablePath(void);
+#endif
+
 #if !defined(__ANDROID__)
 #if __has_include(<signal.h>) && defined(si_pid)
 /// Get the value of the `si_pid` field of a `siginfo_t` structure.