[BUG] WebFetch tool returns 401 OAuth error after successful login

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?

• WebFetch tool consistently fails with: `API Error: 401 {"type":"error","error":{"type":"authentication_error","message":"OAuth authentication is

currently not supported."}`

• Error persists even after /login shows "Login successful"
• Issue prevents basic web fetching functionality

What Should Happen?

EXPECTED: WebFetch should work after successful authentication
ACTUAL: WebFetch fails with OAuth error despite successful login

Error Messages/Logs

API Error: 401 {"type":"error","error":{"type":"authentication_error","message":"OAuth authentication is currently not  supported."},"request_id":"req_011CUEhPdobFiywrLGdt15i2"} · Please run /login

Steps to Reproduce

1. Run /login (returns "Login successful")
2. Attempt to use WebFetch tool on any URL
3. Receive 401 OAuth authentication error

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.0.22

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Other

Additional Information

This is a critical bug that breaks core functionality.