[BUG] Thinking mode hit an infinite loop

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?

Thinking mode had the model repeating the same two sentences over and over infinitum.

sonnet4.6.oddness.txt

What Should Happen?

Not get stuck in an infinite loop.

Error Messages/Logs

Steps to Reproduce

I have no idea what caused this.

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

VS Code extension Identifier anthropic.claude-code Version 2.1.49 Last Updated 17 hours ago

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_