[BUG] Non-plan-file edits occur while plan mode is active

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?

A file other than the designated plan file was edited while plan mode was active.

What Should Happen?

While plan mode is active, no file other than the designated plan file should be editable.

Error Messages/Logs

Steps to Reproduce

1. Enter plan mode.
2. A file other than the designated plan file is edited while plan mode is still active.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.116 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_