[BUG] Persistent Authentication Loop on macOS (All Browsers + Desktop App)

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?

Environment

• macOS version: 26.5 (25F71)
• Claude Desktop version: 1.8555.2
• Browsers tested:
• Safari
• Chrome
• Firefox
• Comet

Authentication on desktop is broken across both the Claude desktop application and all web browsers on macOS.

Instead of successfully logging into my existing account, the authentication process fails and redirects me away from the expected login flow.

The behavior includes:

• Switching between “email link verification” and “enter code” screens
• Email verification link not completing login
• Redirection to account creation instead of existing account authentication
• No successful session established on desktop

This prevents access to my account on all desktop platforms.

Important Context

I am still authenticated on iPhone and iPad apps because those sessions were already active before the issue began.

I have not logged out from mobile devices to avoid losing the only working sessions.

Therefore, I cannot confirm whether a fresh mobile login would behave differently.

Account Authentication Context

The email associated with the account is a custom Gmail-hosted domain address.

However, the account was registered using standard email/password authentication and NOT via “Continue with Google” / Google OAuth.

Troubleshooting Already Attempted

• Clearing cookies/cache
• Incognito/private mode
• Reinstalling desktop app
• Logging out everywhere possible
• Different browsers
• Different networks
• DNS reset
• Restarting macOS
• Disabling extensions
• Fresh browser profiles

None of these resolved the issue.

Support Context

Support has reviewed the situation and indicated this is likely a platform-side authentication issue requiring engineering investigation.

I was advised to report the issue here via GitHub for further review.

Observations
• Desktop browsers all fail
• Desktop app also fails
• Mobile sessions still work
• Email link incorrectly redirects to account creation flow instead of existing account login

This strongly suggests an account-state or authentication-system bug affecting desktop login flows.

Additional Notes

This issue has persisted for several days and prevents normal use of the service on desktop platforms.

Any guidance, debugging steps, or escalation would be appreciated.

What Should Happen?

I should be able to log into my existing account on desktop (browser and desktop application) using the standard authentication flow.

After completing email verification (link or code), I should be:

• Authenticated successfully
• Redirected into my existing account dashboard/session
• Not prompted to create a new account

Error Messages/Logs

Steps to Reproduce

1 Enter account email and proceed with login
2 Receive email authentication prompt
3 UI switches between “click email link” and “enter code” states
4 Click the email verification link
5 Redirected to account creation page instead of login completion
6 Authentication does not succeed

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.145

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_