Plan mode breaks CLI session — messages stop reaching model

Description

Entering plan mode causes the Claude Code CLI session to become unresponsive. The user can still type, but messages no longer reach the model, effectively killing the session. This happens consistently — every time plan mode is entered.

Steps to Reproduce

1. Start a Claude Code CLI session
2. Enter plan mode (via /plan or shift+tab)
3. Try to interact normally
4. Messages appear to send but never reach the model — session is dead

Additional Context

• The /feedback slash command also gets stuck, preventing the user from reporting the issue through the built-in channel
• Platform: macOS (Darwin 25.1.0, arm64)
• Model: claude-opus-4-6
• The session doesn't crash — the UI remains responsive for typing, but no messages are processed

Expected Behavior

Plan mode should allow normal back-and-forth interaction, with the model able to explore the codebase and write a plan before requesting user approval via ExitPlanMode.

Actual Behavior

The session becomes a dead end — typing works but nothing reaches the model. The only recovery is to kill and restart the CLI.