[BUG]

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?

API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.52.content.0: unexpected tool_use_id found in tool_result blocks: toolu_01TpBqJnBCv5MC5LbVDUx8v1. Each tool_result block must have a corresponding tool_use block in the previous message."},"request_id":"req_011CW3hzCNFwRpiALfbnrCJ5"}

What Should Happen?

the prompt should run

Error Messages/Logs

API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.52.content.0: unexpected tool_use_id found in tool_result blocks: toolu_01TpBqJnBCv5MC5LbVDUx8v1. Each tool_result block must have a corresponding tool_use block in the previous message."},"request_id":"req_011CW3hzCNFwRpiALfbnrCJ5"}

Steps to Reproduce

API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.52.content.0: unexpected tool_use_id found in tool_result blocks: toolu_01TpBqJnBCv5MC5LbVDUx8v1. Each tool_result block must have a corresponding tool_use block in the previous message."},"request_id":"req_011CW3hzCNFwRpiALfbnrCJ5"}

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

4.5

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

my first bug report