API Error: 400 due to tool use concurrency issues - persists in specific project

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?

Getting persistent "API Error: 400 due to tool use concurrency issues" in one specific project on Windows VSCode extension.

• Other projects work fine
• Error appears on first tool call (Bash, TodoWrite, etc.)
• Restarting VSCode doesn't help
• Starting new session doesn't help
• Returning to this project always triggers the error

Seems like some cached state is corrupted for this workspace.

Model: claude-opus-4-5-20251101
OS: Windows
Extension: VSCode

What Should Happen?

Claude should deploy to my Raspberry Pi

Error Messages/Logs

API Error: 400 due to tool use concurrency issues

Steps to Reproduce

1. Open a Flutter project in VSCode with Claude Code extension
2. Start a conversation and ask Claude to run a command (e.g. "/deploy" or any bash command)
3. First tool call triggers: "API Error: 400 due to tool use concurrency issues"
4. Close VSCode, reopen - same error
5. Start new chat session - same error
6. Open a different project - works fine
7. Return to original project - error returns

Note: The bug persists only in this specific workspace. Other projects work normally. No specific file content triggers it - it happens on any tool use.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

I'm not sure

Claude Code Version

2.1.19

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_