[BUG] Pro account switching to sonnet[1m] started throwing API 400 error

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?

After a longish session with claude code I got the context running out warning. I switched to /model sonnet[1m] (like I've done before on multiple occasions) this time after I switch any prompts I send to Claude give me errors.

What Should Happen?

Claude should successfully switch to the sonnet[1m] model and I continue to work.

Error Messages/Logs

⎿  API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"This authentication style is incompatible with the long context beta header."},"request_id":"req_011CUHdBF4KdEJTcErrq6KiU"}

Steps to Reproduce

1. Run claude
2. Successfully work with claude until you a context running out warning (5% is the one I got)
3. /model sonnet[1m]
4. any prompt after that returns the above error for me.

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.0.22

Claude Code Version

2.0.22

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

I'm assuming this is an unreproducible 1 off error that will right itself after my daily account resets or something when I get up in the morning. But I wanted to document it here just in case.