MCP Gmail auth hangs indefinitely after browser authentication

Description

The MCP Gmail authentication flow opens the browser and authentication completes, but the CLI hangs indefinitely waiting for the callback after pressing Enter.

Steps to reproduce

1. Run /mcp command
2. Browser opens and completes OAuth authentication
3. Return to Claude Code and press Enter
4. Process hangs forever, never completes the MCP connection

Expected behavior

After authenticating in the browser and pressing Enter, the MCP connection should complete and Gmail tools should become available.

Environment

• Platform: Linux 6.6.128-1-MANJARO (Manjaro)
• The auth callback URL: https://claude.ai/api/organizations/.../mcp/start-auth/...

Current workaround

None found. Process requires force-killing Claude Code.