[BUG] Google OAuth login repeatedly fails on Windows - "ignoring repeat delivery of login callback"

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?

When attempting to log in with Google on the Claude Windows desktop app, the OAuth flow completes in the system browser, but the app ignores the callback with "ignoring repeat delivery of login callback" and immediately logs out. After multiple retry attempts, Cloudflare triggers a 403 block and Turnstile CAPTCHA, causing an endless login/logout loop.

Email/password login works correctly as a workaround.

What Should Happen?

After completing Google authentication in the system browser, the app should successfully receive the OAuth callback and complete the login process.

Error Messages/Logs

[Auth] Using system browser for: /login/app-google-auth
claudeURLHandler: ignoring repeat delivery of login callback
oauth failed: no active organization
[LocalSessionManager] Account logged out, marking for re-init on next login

[Auth] Using system browser for: /login/app-google-auth
claudeURLHandler: ignoring repeat delivery of login callback
Navigation to https://claude.ai/api/challenge_redirect?to=https://claude.ai/login failed with status code 403
Turnstile iframe detected. Removing error overlay.
[account] Identity changed (loggedOut: false → true), clearing oauth cache

Steps to Reproduce

1. Open Claude desktop app on Windows
2. Click "Continue with Google"
3. Complete Google authentication in the system browser
4. App returns to login screen automatically (logged out, no error shown to user)
5. Repeat steps 2–4
6. Cloudflare challenge_redirect returns 403 and Turnstile CAPTCHA is triggered
7. Loop continues indefinitely — only email/password login succeeds

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Claude Desktop App 1.9659.2.0 (auto-updated to 1.9659.4.0 during the affected session)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

• Workaround: email/password login works fine
• The app's claudeURLHandler deduplication logic appears to discard the OAuth callback even on the first delivery, suggesting the callback may be arriving before the handler is fully registered, or the browser is sending it twice
• Log file location: C:\Users\[username]\AppData\Local\Packages\Claude_pzs8sxrjxfjjc\LocalCache\Roaming\Claude\logs\main.log
• The app was undergoing an auto-update (1.9659.2.0 → 1.9659.4.0) around the time the issue occurred, which may or may not be related