[BUG] 400 Error - Duplicate `tool_use` IDs on Single File Read

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?

Summary

Claude Code consistently returns 400 errors with "tool_use" ids must be unique even on single file read operations, making the tool completely unusable.

Environment

• OS: macOS
• Node version: v22.20.0
• Claude Code version: 2.1.19 (Claude Code)
• Package manager: pnpm

Minimal reproduction:

> Read src/components/ForgotPasswordModal.test.tsx
API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.1.content.1: `tool_use` ids must be unique"},"request_id":"req_011CXWdJwusvyPauPWX3nGdg"}

What I've Tried (All Failed)

• [x] /clear command
• [x] New session
• [x] rm -rf ~/.claude-code (nuclear option)
• [x] Explicitly requesting single file reads with prompt: "Use tools one at a time to avoid 400 duplicate tool id issue"
• [x] Multiple restarts

Actual Behavior

Every file read operation fails with duplicate tool_use ID error, regardless of:

• Number of files being read
• Whether context is cleared
• Whether ~/.claude-code is deleted

Impact

Severity: P0/Blocker - Claude Code is completely unusable. Cannot perform any file operations.

Additional Context

The error message messages.1.content.1 suggests the ID collision is happening within the very first tool call of the first assistant message, indicating this is likely a bug in the tool call ID generation logic rather than accumulated state.

What Should Happen?

File read operations should succeed without tool ID collisions.

Error Messages/Logs

**First occurrence (multiple file reads):**

Read ForgotPasswordModal.test.tsx
Read Auth.test.tsx (lines 316-345)
API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.1.content.2: `tool_use` ids must be unique"},"request_id":"req_011CXWckbtxmi9WTHDDu55aL"}


**Second occurrence (single file read):**

Read ForgotPasswordModal.test.tsx
API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.1.content.1: `tool_use` ids must be unique"},"request_id":"req_011CXWdJwusvyPauPWX3nGdg"}

Steps to Reproduce

1. Start a fresh Claude Code session
2. Run /clear to ensure clean context
3. Paste TypeScript errors and ask Claude Code to read a single file
4. Observe 400 error

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Things were working the night before. Then started failing in the morning (not sure if there was auto-update). Then manual update still fails

Claude Code Version

2.1.19 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

VS Code integrated terminal

Additional Information

Potentially Related Issue

https://github.com/anthropics/claude-code/issues/20640