VS Code extension v2.1.138 — random sign-out / 401 mid-call on macOS

Symptom

• Claude Code VS Code extension shows "Sign In" panel at random intervals (hours apart, no clear trigger)
• API requests fail mid-call with 401 Invalid authentication credentials
• Reproduced through Sub-Agent calls dying mid-execution with 401

Environment

• macOS Darwin 25.4.0
• VS Code Claude Code extension v2.1.138 (freshly reinstalled from Marketplace)

Steps tried (none helped)

1. Full VS Code Quit + restart → recurs
2. Extension uninstall + reinstall via \code --uninstall-extension\ / \--install-extension\ → recurs after Sign In
3. Keychain check: \security find-generic-password -s "claude-code"\ → "item not found" (token not stored under that service name)

Expected

Session persists across hours of continuous use; or graceful refresh without forced re-login.

Actual

Forced re-login at random intervals, blocking development work.