[BUG] VSCode Diagnostics makes CC throw 400 errors

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?

Sometimes the VSCode Diagnostics tool corrupts the message history and makes Claude Code throw 400 error

What Should Happen?

VSCode Diagnostics should not malform requests to Anthropic

Error Messages/Logs

API Error: 400 due to tool use concurrency issues. Run /rewind to recover the conversation.

Steps to Reproduce

1. Trigger VSCode Diagnostics
2. See error API Error: 400 due to tool use concurrency issues. Run /rewind to recover the conversation.

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.0.13

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_