[BUG] API Error 400: tool_use ids must be unique - persists after full reinstall

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?

Title: API Error 400: tool_use ids must be unique - persists after full reinstall

Environment:

• OS: Windows 10/11
• VS Code version:Version: 1.108.2 (user setup)

Commit: c9d77990917f3102ada88be140d28b038d1dd7c7
Date: 2026-01-21T13:52:09.270Z
Electron: 39.2.7
ElectronBuildId: 12953945
Chromium: 142.0.7444.235
Node.js: 22.21.1
V8: 14.2.231.21-electron.0
OS: Windows_NT x64 10.0.26200

• Claude Code extension version: dentifier

anthropic.claude-code
Version
2.1.19

Request IDs:

• req_011CXSMxny3aAMaFaEw3uDV4
• req_011CXSPQ9DX8PeiDy6L9aCXV

Attempted fixes (none worked):

• /clear command
• Restart VS Code
• Remove local .claude/sessions, cache, state.json
• Remove global cache ($USERPROFILE\.claude)
• Remove extension globalStorage
• Full uninstall/reinstall of extension

Additional context:
Error persists across fresh sessions. Started around Jan 22-24, 2026.

What Should Happen?

Claude Code should execute tool calls (like reading files) without API errors. Each tool_use ID should be unique and properly generated by the extension.

Error Messages/Logs

**Error:**
API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.1.content.1: `tool_use` ids must be unique"}}

Steps to Reproduce

1. Open project with .claude folder containing custom instructions
2. Start Claude Code
3. Ask Claude to read a file
4. Error appears immediately

Claude Model

None

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

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

Error persists across fresh sessions. Started around Jan 22-24, 2026.