[BUG] Claude Code 2.1.261 crashes

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?

Any message (including /status) in the message box cause a crash, not at the app level, but the message doesn't get processed.
I am using the desktop version of Claude on Enterprise Windows.

<img width="480" height="326" alt="Image" src="https://github.com/user-attachments/assets/9328af6f-c129-4c94-87d3-0a386c9dbd31" />

What Should Happen?

This should work normally.

Error Messages/Logs

Claude Code returned an error result: Sandbox required but unavailable: sandbox is enabled but the Windows sandbox is not active on this session (feature gate off). Set sandbox.failIfUnavailable=false to allow unsandboxed execution.

Error: sandbox required but unavailable: sandbox is enabled but the Windows sandbox is not active on this session (feature gate off)
  sandbox.failIfUnavailable is set — refusing to start without a working sandbox.

Steps to Reproduce

Just open a chat in claude code and type anything

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.1.261

Claude Code Version

2.1.261

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Other

Additional Information

_No response_