MCP: tool call errors with bash on Claude

[bpmct]

Try asking it to do stuff for you on Claude. It ultimately works, but shows a ton of errors

[ThomasK33]

The nil pointer one was fixed by: coder/coder#18978
The unmarshal one I still need to investigate, haven't encountered it yet.

[bpmct]

Another one: I find that Claude always tries to report a task, which fails because we're not inside a workspace

[ThomasK33]

Another one: I find that Claude always tries to report a task, which fails because we're not inside a workspace

Can you copy & paste me the stack trace?

[bpmct]

@ThomasK33 - This happens practically every time you use claude.ai with Coder's MCP. Here was the stack trace in my experience:

Failed to call tool coder_report_task: McpError: MCP error -32603: tool handler panic: runtime error: invalid memory address or nil pointer dereference
stack trace:
goroutine 50381219 [running]:
runtime/debug.Stack()
	/opt/hostedtoolcache/go/1.24.4/x64/src/runtime/debug/stack.go:26 +0x5e
github.com/coder/coder/v2/codersdk/toolsdk.WithRecover.func1.1()
	/home/runner/work/coder/coder/codersdk/toolsdk/toolsdk.go:129 +0x52
panic({0x3988aa0?, 0xf9babb0?})
	/opt/hostedtoolcache/go/1.24.4/x64/src/runtime/panic.go:792 +0x132
github.com/coder/coder/v2/codersdk/toolsdk.init.func2({0x0?, 0xc005106be0?}, {0xc007ae9450?, 0x0?}, {{0xc001c1d998, 0x11}, {0xc0075fccf0, 0x7}, {0xc006f74740, 0x3e}})
	/home/runner/work/coder/coder/codersdk/toolsdk/toolsdk.go:256 +0x51
github.com/coder/coder/v2/codersdk/toolsdk.Tool[...].Generic.func1({0xc007ae9450, 0x0}, {0xc003e4db80?, 0x7c?, 0x80})
	/home/runner/work/coder/coder/codersdk/toolsdk/toolsdk.go:93 +0x169
github.com/coder/coder/v2/codersdk/toolsdk.WithCleanContext.func1({0xd372370, 0xc00fbd7c20}, {0xc007ae9450?, 0x0?}, {0xc003e4db80, 0x7c, 0x80})
	/home/runner/work/coder/coder/codersdk/toolsdk/toolsdk.go:165 +0x1fe
github.com/coder/coder/v2/codersdk/toolsdk.WithRecover.func1({0xd372370?, 0xc00fbd7c20?}, {0xc007ae9450?, 0x0?}, {0xc003e4db80?, 0x0?, 0x0?})
	/home/runner/work/coder/coder/codersdk/toolsdk/toolsdk.go:137 +0x8f
github.com/coder/coder/v2/coderd/mcp.(*Server).RegisterTools.mcpFromSDK.func1({0xd372370, 0xc00fbd7c20}, {{{0xc0075fcc20, 0xa}, {0x0}}, {{0xc001c1d968, 0x11}, {0x3a66ac0, 0xc00fbd7cb0}, 0x0}})
	/home/runner/work/coder/coder/coderd/mcp/mcp.go:111 +0x115
github.com/mark3labs/mcp-go/server.(*MCPServer).handleToolCall(0xc00211e000, {0xd372370, 0xc00fbd7c20}, {0x379d100, 0xc0075fcc00}, {{{0xc0075fcc20, 0xa}, {0x0}}, {{0xc001c1d968, 0x11}, ...}})
	/home/runner/go/pkg/mod/github.com/mark3labs/mcp-go@v0.34.0/server/server.go:1033 +0x3e2
github.com/mark3labs/mcp-go/server.(*MCPServer).HandleMessage(0xc00211e000, {0xd372370?, 0xc00fbd7bf0?}, {0xc00294b600, 0xeb, 0x200})
	/home/runner/go/pkg/mod/github.com/mark3labs/mcp-go@v0.34.0/server/request_handler.go:305 +0xc5f
github.com/mark3labs/mcp-go/server.(*StreamableHTTPServer).handlePost(0xc00a32f8c0, {0xd366c40, 0xc0049bf450}, 0xc0096f23c0)
	/home/runner/go/pkg/mod/github.com/mark3labs/mcp-go@v0.34.0/server/streamable_http.go:318 +0x534
github.com/mark3labs/mcp-go/server.(*StreamableHTTPServer).ServeHTTP(0x0?, {0xd366c40?, 0xc0049bf450?}, 0xc00a7a4460?)
	/home/runner/go/pkg/mod/github.com/mark3labs/mcp-go@v0.34.0/server/streamable_http.go:158 +0x54
github.com/coder/coder/v2/coderd/mcp.(*Server).ServeHTTP(0xc005e07650?, {0xd366c40?, 0xc0049bf450?}, 0x0?)
	/home/runner/work/coder/coder/coderd/mcp/mcp.go:67 +0x25
github.com/coder/coder/v2/coderd.New.func11.2.(*API).mcpHTTPHandler.2({0xd366c40, 0xc0049bf450}, 0xc0096f23c0)
	/home/runner/work/coder/coder/coderd/mcp_http.go:37 +0x2aa
net/http.HandlerFunc.ServeHTTP(0xc004fb7500?, {0xd366c40?, 0xc0049bf450?}, 0x5?)
	/opt/hostedtoolcache/go/1.24.4/x64/src/net/http/server.go:2294 +0x29
github.com/go-chi/chi/v5.(*Mux).Mount.func1({0xd366c40, 0xc0049bf450}, 0xc0096f23c0)
	/home/runner/go/pkg/mod/github.com/go-chi/chi/v5@v5.2.2/mux.go:325 +0x1bb
net/http.HandlerFunc.ServeHTTP(0xc00a7650e0?, {0xd366c40?, 0xc0049bf450?}, 0xc0075fcb68?)
	/opt/hostedtoolcache/go/1.24.4/x64/src/net/http/server.go:2294 +0x29
github.com/go-chi/chi/v5.(*Mux).routeHTTP(0xc0019b46c0, {0xd366c40, 0xc0049bf450}, 0xc0096f23c0)
	/home/runner/go/pkg/mod/github.com/go-chi/chi/v5@v5.2.2/mux.go:478 +0x2e2
net/http.HandlerFunc.ServeHTTP(0xc01e478320?, {0xd366c40?, 0xc0049bf450?}, 0x46025e?)
	/opt/hostedtoolcache/go/1.24.4/x64/src/net/http/server.go:2294 +0x29
github.com/coder/coder/v2/coderd.New.func11.2.RequireExperimentWithDevBypass.1.1({0xd366c40, 0xc0049bf450}, 0xc0096f23c0)
	/home/runner/work/coder/coder/coderd/httpmw/experiments.go:54 +0xa3
net/http.HandlerFunc.ServeHTTP(0xc005108058?, {0xd366c40?, 0xc0049bf450?}, 0xc005108038?)
	/opt/hostedtoolcache/go/1.24.4/x64/src/net/http/server.go:2294 +0x29
github.com/go-chi/chi/v5.(*Mux).ServeHTTP(0xc0019b46c0, {0xd366c40, 0xc0049bf450}, 0xc0096f23c0)
	/home/runner/go/pkg/mod/github.com/go-chi/chi/v5@v5.2.2/mux.go:73 +0x32f
github.com/go-chi/chi/v5.(*Mux).Mount.func1({0xd366c40, 0xc0049bf450}, 0xc0096f23c0)
	/home/runner/go/pkg/mod/github.com/go-chi/chi/v5@v5.2.2/mux.go:325 +0x1bb
net/http.HandlerFunc.ServeHTTP(0xc00a7650e0?, {0xd366c40?, 0xc0049bf450?}, 0xc011eb5c10?)
	/opt/hostedtoolcache/go/1.24.4/x64/src/net/http/server.go:2294 +0x29
github.com/go-chi/chi/v5.(*Mux).routeHTTP(0xc0019b4600, {0xd366c40, 0xc0049bf450}, 0xc0096f23c0)
	/home/runner/go/pkg/mod/github.com/go-chi/chi/v5@v5.2.2/mux.go:478 +0x2e2
net/http.HandlerFunc.ServeHTTP(0xc009129540?, {0xd366c40?, 0xc0049bf450?}, 0xc?)
	/opt/hostedtoolcache/go/1.24.4/x64/src/net/http/server.go:2294 +0x29
github.com/coder/coder/v2/coderd.New.ExtractAPIKeyMW.func18.1({0xd366c40, 0xc0049bf450}, 0xc009129540)
	/home/runner/work/coder/coder/coderd/httpmw/apikey.go:147 +0x1d7
net/http.HandlerFunc.ServeHTTP(0xc0082c24c8?, {0xd366c40?, 0xc0049bf450?}, 0xc0082c24a8?)
	/opt/hostedtoolcache/go/1.24.4/x64/src/net/http/server.go:2294 +0x29
github.com/go-chi/chi/v5.(*Mux).ServeHTTP(0xc0019b4600, {0xd366c40, 0xc0049bf450}, 0xc009129540)
	/home/runner/go/pkg/mod/github.com/go-chi/chi/v5@v5.2.2/mux.go:73 +0x32f
github.com/go-chi/chi/v5.(*Mux).Mount.func1({0xd366c40, 0xc0049bf450}, 0xc009129540)
	/home/runner/go/pkg/mod/github.com/go-chi/chi/v5@v5.2.2/mux.go:325 +0x1bb
net/http.HandlerFunc.ServeHTTP(0xc00a7650e0?, {0xd366c40?, 0xc0049bf450?}, 0xc020abc0a0?)
	/opt/hostedtoolcache/go/1.24.4/x64/src/net/http/server.go:2294 +0x29
github.com/go-chi/chi/v5.(*Mux).routeHTTP(0xc0017d0840, {0xd366c40, 0xc0049bf450}, 0xc009129540)
	/home/runner/go/pkg/mod/github.com/go-chi/chi/v5@v5.2.2/mux.go:478 +0x2e2
net/http.HandlerFunc.ServeHTTP(0xc01cfaf180?, {0xd366c40?, 0xc0049bf450?}, 0x21?)
	/opt/hostedtoolcache/go/1.24.4/x64/src/net/http/server.go:2294 +0x29
github.com/justinas/nosurf.(*CSRFHandler).handleSuccess(...)
	/home/runner/go/pkg/mod/github.com/justinas/nosurf@v1.2.0/handler.go:178
github.com/justinas/nosurf.(*CSRFHandler).ServeHTTP(0xc01cfaf180, {0xd366c40, 0xc0049bf450}, 0x16?)
	/home/runner/go/pkg/mod/github.com/justinas/nosurf@v1.2.0/handler.go:151 +0x490
github.com/coder/coder/v2/coderd.New.func5.1({0xd366c40, 0xc0049bf450}, 0xc0091292c0)
	/home/runner/work/coder/coder/coderd/coderd.go:884 +0x122
net/http.HandlerFunc.ServeHTTP(0xc000d89680?, {0xd366c40?, 0xc0049bf450?}, 0xc0091292c0?)
	/opt/hostedtoolcache/go/1.24.4/x64/src/net/http/server.go:2294 +0x29
github.com/go-chi/cors.(*Cors).Handler-fm.(*Cors).Handler.func1({0xd366c40, 0xc0049bf450}, 0xc0091292c0)
	/home/runner/go/pkg/mod/github.com/go-chi/cors@v1.2.1/cors.go:228 +0x17e
net/http.HandlerFunc.ServeHTTP(0xd32a460?, {0xd366c40?, 0xc0049bf450?}, 0xd?)
	/opt/hostedtoolcache/go/1.24.4/x64/src/net/http/server.go:2294 +0x29
github.com/coder/coder/v2/coderd/httpmw.Cors.func1.1({0xd366c40, 0xc0049bf450}, 0xc0091292c0)
	/home/runner/work/coder/coder/coderd/httpmw/cors.go:84 +0x143
net/http.HandlerFunc.ServeHTTP(0xc0000842e9?, {0xd366c40?, 0xc0049bf450?}, 0xd?)
	/opt/hostedtoolcache/go/1.24.4/x64/src/net/http/server.go:2294 +0x29
github.com/coder/coder/v2/coderd/workspaceapps.(*Server).parseHostname(0xc0006f8000, {0xd366c40, 0xc0049bf450}, 0xc0091292c0, {0xd32a460, 0xc001b29020}, {0xc011eb5a80, 0xd})
	/home/runner/work/coder/coder/coderd/workspaceapps/proxy.go:443 +0x10c
github.com/coder/coder/v2/coderd.New.(*Server).HandleSubdomain.func25.1({0xd366c40, 0xc0049bf450}, 0xc0091292c0)
	/home/runner/work/coder/coder/coderd/workspaceapps/proxy.go:392 +0x24e
net/http.HandlerFunc.ServeHTTP(0x0?, {0xd366c40?, 0xc0049bf450?}, 0x15?)
	/opt/hostedtoolcache/go/1.24.4/x64/src/net/http/server.go:2294 +0x29
github.com/coder/coder/v2/coderd.New.func4.1({0xd366c40, 0xc0049bf450}, 0xc0091292c0)
	/home/runner/work/coder/coder/coderd/coderd.go:867 +0x145
net/http.HandlerFunc.ServeHTTP(0xc0091292c0?, {0xd366c40?, 0xc0049bf450?}, 0xc0057a0030?)
	/opt/hostedtoolcache/go/1.24.4/x64/src/net/http/server.go:2294 +0x29
github.com/coder/coder/v2/coderd/httpmw.Prometheus.func1.1({0xd366c40, 0xc0049bf450}, 0xc0091292c0)
	/home/runner/work/coder/coder/coderd/httpmw/prometheus.go:92 +0x363
net/http.HandlerFunc.ServeHTTP(0xd372370?, {0xd366c40?, 0xc0049bf450?}, 0xfadb2a0?)
	/opt/hostedtoolcache/go/1.24.4/x64/src/net/http/server.go:2294 +0x29
github.com/coder/coder/v2/coderd/rbac/rolestore.CustomRoleMW.func1({0xd366c40, 0xc0049bf450}, 0xc009129180)
	/home/runner/work/coder/coder/coderd/rbac/rolestore/rolestore.go:22 +0x157
net/http.HandlerFunc.ServeHTTP(0xc00054d400?, {0xd366c40?, 0xc0049bf450?}, 0xd308040?)
	/opt/hostedtoolcache/go/1.24.4/x64/src/net/http/server.go:2294 +0x29
github.com/coder/coder/v2/coderd.singleSlashMW.func1({0xd366c40, 0xc0049bf450}, 0xc009129180)
	/home/runner/work/coder/coder/coderd/coderd.go:1982 +0x13f
net/http.HandlerFunc.ServeHTTP(0xc009129040?, {0xd366c40?, 0xc0049bf450?}, 0xc002c18dc0?)
	/opt/hostedtoolcache/go/1.24.4/x64/src/net/http/server.go:2294 +0x29
github.com/coder/coder/v2/coderd.New.Logger.func24.1({0xd366c40, 0xc0049bf450}, 0xc009129040)
	/home/runner/work/coder/coder/coderd/httpmw/loggermw/logger.go:46 +0x4e3
net/http.HandlerFunc.ServeHTTP(0xc011eb5ba0?, {0xd366c40?, 0xc0049bf450?}, 0xfadb2a0?)
	/opt/hostedtoolcache/go/1.24.4/x64/src/net/http/server.go:2294 +0x29
github.com/coder/coder/v2/coderd.New.ExtractRealIP.func23.1({0xd366c40, 0xc0049bf450}, 0xc009128f00)
	/home/runner/work/coder/coder/coderd/httpmw/realip.go:50 +0x158
net/http.HandlerFunc.ServeHTTP(0x3e12560?, {0xd366c40?, 0xc0049bf450?}, 0x12?)
	/opt/hostedtoolcache/go/1.24.4/x64/src/net/http/server.go:2294 +0x29
github.com/coder/coder/v2/coderd/httpmw.AttachRequestID.func1({0xd366c40, 0xc0049bf450}, 0xc009128dc0)
	/home/runner/work/coder/coder/coderd/httpmw/requestid.go:38 +0x57a
net/http.HandlerFunc.ServeHTTP(0x3e12560?, {0xd366c40?,…

[ThomasK33]

coder/coder#19045