Critical: After update, app refuses to start claiming another instance is running (none visible in processes)

Summary

After updating Claude Code to a new version, the application refuses to start with a message indicating another instance is already running. However, no Claude Code process is visible in Task Manager or process list.

Steps to reproduce

1. Have Claude Code running
2. Update arrives / gets installed
3. Close Claude Code
4. Try to relaunch Claude Code
5. App shows error that another instance is already running
6. Check Task Manager — no Claude Code process exists

Workaround

The only workaround found so far is to manually search for and kill any hidden lock files or restart the machine entirely.

Expected behavior

• After update, the application should start cleanly
• If a stale lock exists from a previous instance, it should be detected and released automatically
• The app should not rely on a lock mechanism that can become orphaned

Likely cause

A lock file or named pipe/mutex from the previous version persists after the process exits (possibly related to orphaned Node.js/bash child processes from #41742 that hold handles). The new version detects the stale lock and refuses to start, even though the original process is gone.

Environment

• OS: Windows 11
• Claude Code: occurs during version upgrades