[BUG] OAuth Authorize button returns 500 Internal Server Error — cannot login to Claude Code in VSCode

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?

OAuth token expired in Claude Code (VSCode extension). When clicking the Authorize button on the OAuth page, the server returns a 500 Internal Server Error. Authentication never completes and Claude Code remains unusable.

The page briefly flashes "Build something great. You're all set up for Claude Code." before showing "Authorization failed — Internal server error", suggesting the flow partially completes on the browser side but fails on Anthropic's backend.

What Should Happen?

Clicking "Authorize" should complete the OAuth flow, return a token to Claude Code, and allow normal usage to resume.

Error Messages/Logs

Terminal:

API Error: 401 {"type":"error","error":{"type":"authentication_error","message":"OAuth token has expired. Please obtain a new token or refresh your existing token."}}
Please run /login

OAuth error: timeout of 15000ms exceeded


Browser console (all browsers: Chrome, Edge):

POST https://claude.ai/v1/oauth/eb81b55e-f1e4-4a57-bad1-92e8b1dd60bd/authorize 500 (Internal Server Error)

Failed to load resource: the server responded with a status of 405 ()

[REACT_QUERY_CLIENT] QueryClient error: a: Internal server error
    at n (5741-e0df12e868d24a1c.js:1:95179)
    at 5741-e0df12e868d24a1c.js:1:100054
    at async Object.mutationFn (5741-e0df12e868d24a1c.js:1:100872)

Steps to Reproduce

1. Use Claude Code in VSCode until OAuth token expires (~4 days)
2. Claude Code prompts to re-authenticate with 401 error
3. Run /login or claude auth login in terminal
4. Browser opens the OAuth authorize page at https://claude.ai/oauth/authorize?code=true&client_id=9d1c250a-e61b-44d9-88ed-5944d1962f5e&...
5. Click the Authorize button
6. Page shows "Authorization failed — Internal server error"
7. Terminal shows OAuth error: timeout of 15000ms exceeded

Workarounds attempted (all failed):

• Tried on Chrome, Edge (different browsers)
• Tried in Incognito mode
• Deleted ~/.claude.json and ~/.claude/ then retried
• Logged out of claude.ai on browser then re-logged in before authorizing
• status.anthropic.com shows no incidents

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Unknown — worked before token expiry (5 hours ago)

Claude Code Version

v2.1.76

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

The OAuth endpoint POST /v1/oauth/{session-id}/authorize is returning 500 on Anthropic's server side. This is not reproducible to a specific browser or local config — the error originates from Anthropic's backend. The issue blocks all Claude Code usage until re-authentication is possible.