[BUG] > API Error: 400 | This credential is only authorized for use with Claude Code and cannot be used for other API requests.

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 got this error that seems like a bug with Claude. Here is the terminal interaction from the point when I set the model to Opus form the default of sonnet.
I have resoning/thinking set on and respnses take often a minute or so, therefore I wanted to see if Opus was faster (even though its marked -- for some reason -- in /config as Legacy .

> /config
  ⎿  Set model to opus (claude-opus-4-1-20250805)

> What model am I talking to?
  ⎿ API Error: 400
    {"type":"error","error":{"type":"invalid_request_error","message":"This
    credential is only authorized for use with Claude Code and cannot be used for
    other API requests."},"request_id":"req_011CVK61P2dpseRxf79PMu24"}

> /config
  ⎿  Set model to haiku (claude-haiku-4-5-20251001)

> /config
  ⎿  Config dialog dismissed

> What model am I talking to?

● You're talking to Claude Haiku (claude-haiku-4-5-20251001).

  Your last /config output shows "Set model to [haiku
  (claude-haiku-4-5-20251001)]".

> /config
  ⎿  Set model to Default (Sonnet 4.5 · Smartest model for daily use)

> What model am I talking to?

● You're talking to Claude Sonnet 4.5 (claude-sonnet-4-5-20250929).

  Your last /config output shows "Set model to Default (Sonnet 4.5 · Smartest
  model for daily use)".
<...> 

What Should Happen?

It should just work

PS. Thanks for Claude Code

Error Messages/Logs

Steps to Reproduce

/config
Change model to Opus

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.047

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

It also does not work in WezTerm FWIW.

Environment is WSL and tmux