[BUG] VS Code Extension: "tool_use ids must be unique" API 400 error during multi-step operations
Status Closed — not planned
Reported on v2.1.19
Maintainer reply None cached
Activity 11 comments · opened Jan 24, 2026 · closed Feb 28, 2026
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?
Description
The VS Code extension returns API 400 errors with the message tool_use ids must be unique when Claude executes a series of tool calls or concurrent operations. This is a new issue - I have hundreds of hours of usage without ever seeing this before.
This does NOT occur in:
- Native terminal CLI (
claudecommand) - Claude Desktop app
The issue is isolated to the VS Code extension only.
Key Observations
- Terminal CLI: Works perfectly, no issues
- Claude Desktop: Works perfectly, no issues
- VS Code Extension: Consistent errors - duplicate tool_use IDs being sent
- First occurrence ever after hundreds of hours of use - likely a recent regression
- Error appears at message index 17, suggesting it happens after several successful tool calls in a conversation
What Should Happen?
Expected Behavior
Tool calls should have unique IDs and complete without API errors.
Actual Behavior
The extension appears to be generating duplicate tool_use IDs, causing the API to reject the request. Reinstalling the extension temporarily resolves the issue, but it recurs.
Error Messages/Logs
API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.17.content.1: tool_use ids must be unique"},"request_id":"req_011CXSWBurLBYkTPAkWiaGjx"}Steps to Reproduce
- Open Claude Code in VS Code extension
- Ask Claude to perform a task requiring multiple tool calls (e.g., "explore this codebase")
- API 400 errors occur consistently with "tool_use ids must be unique" message
- Also happens when asking Claude to run tools concurrently/in parallel
Claude Model
Opus
Is this a regression?
Yes, this worked in a previous version
Last Working Version
_No response_
Claude Code Version
2.1.19
Platform
Anthropic API
Operating System
macOS
Terminal/Shell
iTerm2
Additional Information
_No response_
11 Comments
Found 3 possible duplicate issues:
This issue will be automatically closed as a duplicate in 3 days.
🤖 Generated with Claude Code
This appears to be a widespread issue today. Related reports with the same
tool_use ids must be uniqueerror:All opened today (Jan 24, 2026), suggesting a recent regression in v2.1.19 or server-side change.
it seems like it might be but I have no way of knowing if the issue is, in fact, the same
So it’s a bug from Anthropic ? And not specific user setup
seems like it?
This might have happened before rarely but this is 100% and completely breaking. I've had to abandon using this completely because of this. Can't believe they released this. Back to crappy terminal version...
agreed, frustrating for sure, making it work with terminal open in VSC but not great
also happens to me, tried everything a human could possibly do including full deletion of all cached folders and files that claude can make.
nothing fixes it on a user side (this includes reinstalling it of course)
rolled back to 2.1.17 and it seems to relieve it until it's fixed.
Closing for now — inactive for too long. Please open a new issue if this is still relevant.
This issue has been automatically locked since it was closed and has not had any activity for 7 days. If you're experiencing a similar issue, please file a new issue and reference this one if it's relevant.