[BUG] v2.1.121 OAuth authentication fails with 401 on Team subscription, v2.1.89 works fine

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 upgrading from v2.1.89 to v2.1.121, all messages fail with infinite retry. Eventually the request fails with:

API Error: 401 {"type":"error","error":{"type":"authentication_error","message":"OAuth authentication is currently not supported."},"request_id":"req_011CaW9rMUjK2DLHCWxxksLB"}

Downgrading to v2.1.89 immediately resolves the issue using the exact same credentials and config. Re-upgrading to v2.1.121 reproduces the bug consistently.

Things I tried that did NOT work:

• /logout and /login (login succeeds but messages still 401)
• Deleted keychain credentials via security delete-generic-password -s "Claude Code-credentials" and re-logged in
• Verified model config is valid (claude-opus-4-6)
• Confirmed network connectivity (curl to api.anthropic.com returns 405 as expected)

What worked:

• Downgrading to v2.1.89

What Should Happen?

Messages should be sent successfully without 401 errors, just like in v2.1.89 with the same credentials and configuration.

Error Messages/Logs

API Error: 401 {"type":"error","error":{"type":"authentication_error","message":"OAuth authentication is currently not supported."},"request_id":"req_011CaW9rMUjK2DLHCWxxksLB"}

Please run /login

Steps to Reproduce

1. Use Claude Code with a Team subscription, logged in via OAuth (claude.ai)
2. Install v2.1.121: npm install -g @anthropic-ai/claude-code@2.1.121
3. Run claude and send any message (e.g., "hello")
4. Observe infinite retry, then 401 OAuth authentication error
5. Downgrade to v2.1.89: npm install -g @anthropic-ai/claude-code@2.1.89
6. Same message works immediately with no other changes

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.1.89

Claude Code Version

2.1.121 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Subscription: Team
Organization: HappyFactory
Auth method: OAuth via claude.ai
Node version: v20.19.4 (managed by nvm)
Install path: /Users/[user]/.nvm/versions/node/v20.19.4

The 401 error persists across:

• Fresh OAuth login
• Cleared keychain credentials
• Different working directories (with/without project-level .claude/settings.json)

The same machine, same credentials, same project, and same global config work flawlessly on v2.1.89.