[BUG] Magic-link email login redirects to onboarding for existing Max subscriber — same backend auth-routing failure as #36797, #60022

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?

I'm an existing, actively-billed Claude Max subscriber and I'm locked out on web and desktop. When I request a login email and click the verification link, I'm redirected to claude.ai/onboarding ("Let's create your account") with my email shown as verified, instead of being authenticated into my existing account. No dashboard, no error message, and no path back to the existing account.

This is the same backend identity-mapping / auth-routing failure documented in #36797, #39788, #51002, #57164, #60022, and #58566. Mine is the magic-link variant, closest to #36797 and #60022.

I am filing on this repo per the precedent in #51002 and #57164, where backend auth/billing issues required engineering escalation because Fin AI Support could not resolve them.

What Should Happen?

A login with a verified email that maps to an existing paid account should resolve to that account's dashboard on all surfaces. The auth callback should never silently fall through to the new-user onboarding flow when the verified email maps to a billed existing account. At minimum it should surface an explicit error and route to support rather than let the user click "Create account" and silently spawn a duplicate.

Error Messages/Logs

None

Steps to Reproduce

1. Have an existing, active, paid Claude Max account.
2. Sign out of claude.ai in the browser, or let the session expire.
3. Request a login email and click the magic-link.
4. Observe: email is verified, but the flow lands on "Let's create your account" onboarding instead of the existing account dashboard.
5. Same behavior in Claude Desktop and Claude Code

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

N/A the issue is with login, including web

Platform

Other

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Important Context

• Account email: al4ikk@gmail.com
• Plan: Claude Max, active billing, paid invoices on file.
• The Claude mobile app remains fully authenticated with active access — this confirms the account and subscription are intact.
• I have NOT clicked "Create account," to avoid silently creating a duplicate account under this email.

Environment

• Claude Desktop + web + code (Chrome and one additional browser tested in different devices)
• Claude mobile app: still authenticated (unaffected)

Requested Resolution

1. Engineer-side fix of the auth-routing logic so magic-link logins for al4ikk@gmail.com resolve to the existing Max account on desktop and web.
2. Confirmation that no duplicate account has been silently created under this email.

Happy to verify identity, payment, and account ownership through any official Anthropic channel.