[BUG] API Error: 400 due to tool use concurrency issues.

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?

In Claude Code (VSCode extension) I'm getting repeated error messages after each prompt.

API Error: 400 due to tool use concurrency issues.

Tried logging out and back in, did not resolve. In troubleshooting, Claude's responses indicate the problem is at their end but am not able to resolve.

What Should Happen?

Claude Code should not throw the 400 error at each prompt!

Error Messages/Logs

API Error: 400 due to tool use concurrency issues.

Steps to Reproduce

Type a prompt that involves the access or edit of a file, and receive the prompt API Error: 400 due to tool use concurrency issues.

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.6 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_