[BUG] v2.1.12 requesting 100,001 output tokens (exceeds 64k limit)

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?

I'm getting this error with a clear context, only with 2.1.12.

⎿ API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"max_tokens:
100001 > 64000, which is the maximum allowed number of output tokens for
claude-sonnet-4-5-20250929"},"request_id":"req_011CXGbyuovVsxoyrwv35JtD"}

What Should Happen?

I shouldn't get an error.

Error Messages/Logs

Steps to Reproduce

Just typing anything in the context window.

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.12

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_