{"record":{"id":"c86c42578d1ace6f","repo":"chenhg5/cc-connect","slug":"taskkill-failed-w-s-process-kill-fallback-fai-c86c42","errorCode":null,"errorMessage":"taskkill failed: %w: %s; process kill fallback failed: %w","messagePattern":"taskkill failed: %w: (.+?); process kill fallback failed: %w","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"agent/copilot/proc_windows.go","lineNumber":51,"sourceCode":"func forceKillCmd(cmd *exec.Cmd) error {\n\tif cmd == nil || cmd.Process == nil {\n\t\treturn nil\n\t}\n\tkillCmd := exec.Command(\"taskkill\", \"/T\", \"/F\", \"/PID\", strconv.Itoa(cmd.Process.Pid))\n\toutput, err := killCmd.CombinedOutput()\n\tif err == nil {\n\t\treturn nil\n\t}\n\tif bytes.Contains(bytes.ToLower(output), []byte(\"there is no running instance\")) {\n\t\treturn nil\n\t}\n\tif bytes.Contains(bytes.ToLower(output), []byte(\"not found\")) {\n\t\treturn nil\n\t}\n\tif killErr := cmd.Process.Kill(); killErr == nil || errors.Is(killErr, os.ErrProcessDone) {\n\t\treturn nil\n\t} else {\n\t\treturn fmt.Errorf(\"taskkill failed: %w: %s; process kill fallback failed: %w\", err, processKillOutput(output), killErr)\n\t}\n}\n\nfunc processKillOutput(output []byte) string {\n\ttrimmed := strings.TrimSpace(string(output))\n\tif trimmed == \"\" {\n\t\treturn \"(empty output)\"\n\t}\n\treturn trimmed\n}\n","sourceCodeStart":33,"sourceCodeEnd":62,"githubUrl":"https://github.com/chenhg5/cc-connect/blob/4000b2338aa6e850c99df54f8b0ed6ed7460b401/agent/copilot/proc_windows.go#L33-L62","documentation":"On Windows, forceKillCmd first tries `taskkill /F /T` to terminate the copilot process tree, then falls back to Go's cmd.Process.Kill(). Only if BOTH mechanisms fail does it return \"taskkill failed: %w: %s; process kill fallback failed: %w\", wrapping the taskkill error, its captured output, and the Process.Kill error.","triggerScenarios":"Calling forceKillCmd on a Windows system where taskkill returns a non-\"not found\" error (bad flags, access denied, process already re-parented) and the subsequent Process.Kill also fails (process already exited, ErrPermission, handle invalid).","commonSituations":"Insufficient privileges to force-kill a process owned by another user; antivirus blocking taskkill; the process exited between detection and kill so the PID is stale; taskkill.exe missing from PATH while the direct kill also fails.","solutions":["Check the embedded taskkill output string (via %s) for the root cause — access denied is the most common","Run cc-connect with sufficient privileges, or verify the process belongs to the same user","Treat the session as already dead if the process had exited — restart the session rather than retrying the kill","On non-Windows CI ensure this code path (proc_windows.go) is not being executed unintentionally"],"exampleFix":"// before: blindly retrying the same kill\nreturn forceKillCmd(cmd)\n// after: accept ErrProcessDone / already-exited as success, else restart session\nif errors.Is(killErr, os.ErrProcessDone) { return nil }\nslog.Warn(\"copilot: force kill failed\", \"err\", err); return startNewSession(ctx)","handlingStrategy":"fallback","validationCode":"// pre-check on Windows before relying on taskkill\nif _, err := exec.LookPath(\"taskkill\"); err != nil {\n    slog.Warn(\"taskkill unavailable, will rely on Process.Kill fallback\")\n}","typeGuard":null,"tryCatchPattern":"err := forceKillCmd(cmd)\nif err != nil {\n    slog.Warn(\"copilot: force kill failed\", \"err\", err)\n    // treat the session as dead and rebuild it\n    return startNewSession(ctx)\n}","preventionTips":["Run the daemon under a user that owns the copilot child processes","Accept os.ErrProcessDone as a successful kill","Check the taskkill output embedded in the error for 'Access is denied'","Test the kill path on a real Windows machine, not only in CI on Linux"],"tags":["windows","process","kill","taskkill"],"backgroundTag":"process-kill-failed","analyzedSha":"4000b2338aa6e850c99df54f8b0ed6ed7460b401","analyzedAt":"2026-09-06T11:45:09.575Z","contentChangedAt":"2026-09-06T11:45:09.575Z","schemaVersion":2},"datasetVersion":"2026-09-14T05:17:10.506Z"}