[[BUG] Magic-link and Google login redirect existing Pro subscriber to "Let's create your account" onboarding — all new logins locked out, existing iPhone app session still authenticated

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?

This issue is filed on the claude-code repo per the precedent in #36797, #39788, #57164, #58566, and #60022, where the same backend auth-routing failure required engineering escalation because Fin AI Support could not resolve it. This affects claude.ai web login; Claude Code fields below are N/A for that reason.

What's wrong

Account email: mikecrisfield@gmail.com (active Pro subscription, active billing)

Every new login attempt redirects to the "Let's create your account" onboarding page instead of authenticating my existing account. The onboarding page displays "Email verified as mikecrisfield@gmail.com" at the bottom — the email verifies successfully, then the callback falls through to new-user onboarding instead of routing to my existing account.

Key details

• My existing session in the Claude iOS app remains fully authenticated and functional — all conversations, settings, and Pro plan visible. The account exists and is active.
• The failure affects ALL new login attempts: multiple PCs, multiple browsers, and Safari on the same iPhone where the app session works.
• Both authentication methods fail identically: magic-link email login AND Continue with Google.
• Persisting for multiple days — not related to any transient status.claude.com incident.
• Already tried: clearing cache/cookies, incognito/private windows, multiple browsers (Chrome/others), multiple computers, cross-device verification codes, VPN off.
• No account was ever deleted with this email; no policy violations.
• I have NOT clicked "Create account," to avoid spawning a duplicate account under the same email (per the data-integrity failure documented in #51002 and #57164).

Steps to reproduce

1. Existing account with active Pro subscription, authenticated in the iOS app
2. On any other device/browser, go to claude.ai and sign in via magic link or Google with the same email
3. Email verifies successfully
4. Redirected to /onboarding "Let's create your account" instead of the account dashboard

Expected behavior

A verified email that maps to an existing billed account should authenticate into that account and route to the dashboard, regardless of device or browser. The callback handler should never silently fall through to new-user onboarding for an existing subscriber.

Support history

Spent 2+ hours with Fin AI Support (conversation ID 215475117037732). Fin confirmed the account exists and is active, exhausted all standard troubleshooting, acknowledged this is a backend account-state issue it cannot resolve, and stated human support routing is unavailable for individual Pro accounts.

Request

Please route this to a human who can inspect the server-side identity mapping for mikecrisfield@gmail.com and repair the routing to my existing account. Screenshots available: onboarding page showing "Email verified as mikecrisfield@gmail.com," iOS app showing active logged-in Pro account.

Environment

Claude Code version: N/A (claude.ai web auth issue)
Platform: claude.ai web — reproduced on Windows PCs (multiple browsers) and iOS Safari

What Should Happen?

I should be able to log into my account

Error Messages/Logs

Steps to Reproduce

Trying to log into Claude

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

N/A — claude.ai web authentication issue, not CLI. Claude Code not installed.

Platform

Other

Operating System

Other

Terminal/Shell

Windows Terminal

Additional Information

_No response_