[BUG] Plan mode state inconsistency when ExitPlanMode is interrupted by user

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Bug Description

When a user interrupts an ExitPlanMode tool call (e.g., to correct something mid-approval), plan mode remains active but in an inconsistent state:

System reminders continue enforcing "Plan mode still active — read-only except plan file"
However, Edit/Write tool calls may still succeed, creating contradictory behavior
There is no manual escape hatch (like /exit-plan command) to recover
The stale plan mode constraints persist for the rest of the conversation, degrading output quality

Impact

In our session, this caused degraded output across ~20 turns due to conflicting system instructions.

What Should Happen?

One of:

Interrupted ExitPlanMode should cleanly exit plan mode
OR provide a manual escape command (e.g., /exit-plan)
OR allow the agent to call ExitPlanMode again

Error Messages/Logs

Steps to Reproduce

Enter plan mode via EnterPlanMode
Write a plan, then call ExitPlanMode
User interrupts the ExitPlanMode call (rejects it to provide a correction)
Plan mode is now stuck — system reminders keep enforcing read-only constraints
Subsequent tool calls operate under conflicting instructions

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

v2.1.150

Platform

Other

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_