[BUG] OAuth login loop — "Redirect URI not supported by client" error after authorizing

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 clearing credentials and running claude auth login, the OAuth flow completes in the browser but Claude Code never authenticates. In Safari, the page briefly flashes "Max or Pro account required" before redirecting to account selection panels. In Chrome incognito, authorizing returns the error: Redirect URI https:/platform.claude.com/oauth/code/callback is not supported by client. Chrome also displays an authentication code to paste, but the terminal never prompts for it.

<img width="615" height="379" alt="Image" src="https://github.com/user-attachments/assets/ba736774-1dda-4e26-951e-37983b6d3a25" />

What Should Happen?

After completing the OAuth flow in the browser, Claude Code should authenticate successfully, or the terminal should provide a way to manually paste the authorization code.

Error Messages/Logs

Redirect URI https:/platform.claude.com/oauth/code/callback is not supported by client

Steps to Reproduce

1. Clear credentials: rm -f ~/.claude.json && rm -rf ~/.claude/
2. Remove Keychain entries for Claude/Anthropic
3. Run claude auth login
4. Browser opens OAuth flow
5. Authorize the connection
6. Safari: flashes "Max or Pro account required," redirects to account panels, never completes auth
7. Chrome incognito: shows redirect URI error above

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.81

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Tried claude auth logout, full credential wipe, and full uninstall/reinstall via sudo npm install -g @anthropic-ai/claude-code@latest — same result each time.