[BUG] OAuth login redirects existing Max subscriber to "Let's create your account" onboarding loop, browser + Mac desktop + Windows desktop all locked out, iPhone + Console + Claude Code 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?

Starting May 11, 2026, signing in to claude.ai in any browser (Chrome, Safari) on any device (MacBook Air, Windows Surface, Mac mini) AND in the Claude Desktop app on Mac results in the same broken flow:

1. Email / Google authentication completes successfully
2. Anthropic backend does not match my verified identity to my existing Max account
3. I am dropped on the onboarding page showing "Let's create your account — Email verified as fightorflight2525@gmail.com"
4. No error surfaced, silent auth-routing failure

My existing Max subscription is active and being billed:

• Plan: Claude Max (5x more usage than Pro)
• Auto-renew: Jun 4, 2026
• Recent invoices PAID: May 4, 2026 ($106.60), Apr 4, 2026 ($101.45), Apr 3, 2026 ($5.33)
• Payment: Visa ending 4910

I have deliberately NOT clicked "Create account" to avoid the duplicate-account disaster documented in #51002.

Working access points proving account integrity:

• Claude iOS app: still logged in, full Max access, settings shows fightorflight2525@gmail.com with Max plan — ONLY confirmed working surface
• Claude Console (platform.claude.com): logged in successfully (separate API-key auth, not OAuth subscription)

Confirmed BROKEN surfaces (all return 401 invalid_credentials or onboarding loop):

• claude.ai web in Chrome and Safari on MacBook Air, Windows Surface, Mac mini
• Claude Desktop app on macOS
• Claude Desktop app on Windows
• Claude Code CLI v2.1.116 on MacBook Air: "Failed to authenticate. API Error: 401 {"type":"error","error":{"type":"authentication_error","message":"Invalid authentication credentials"},"request_id":"req_011CayiHK1RZ7JFqZouKyPbW"}"
• Claude Code CLI v2.1.140 on Mac mini (via SSH): same 401 invalid_credentials error

Every OAuth-based authentication surface fails simultaneously. This matches the token-corruption pattern documented in #48079 and #44930.

This confirms the account exists, the subscription is active and paid, and only the browser plus Claude Desktop auth handoff is broken.

This matches the documented recurring pattern across at least 4 prior issues:

• #36797 (Mar 2026): identical "Let's create your account" redirect with "Not found" badge, unresolved
• #39788 (Mar 2026): OAuth login redirects to account creation instead of authenticating existing Max subscription, closed as duplicate with no resolution
• #51002 (Apr 2026): clicking "Create account" creates duplicate under same email with different auth provider, locks user out of original paid account — the disaster I am avoiding
• #57164 (May 8, 2026): nearly identical to my case, Google OAuth handoff failure for existing Max subscriber, browser and desktop locked out while iPhone and CLI still work

I am case 5 in this recurring pattern.

Support path attempted:

1. Fin AI Agent conversation 1 on May 12, 2026, Conversation ID 215474274769576. Fin recommended cache clear, app reinstall, and log out of all sessions, without engineering escalation.
2. Fin AI Agent / support email conversation 2 on May 12, 2026, Conversation ID 215474280845997. Auto-acknowledgment received, awaiting human Product Support response.

Impact: paying Max subscriber blocked on primary work devices, active business workflow blocked with team waiting on deliverables, skills and projects inaccessible from any UI that supports them properly. Direct productivity loss ongoing.

Request to engineering: route this to a human Product Support specialist who can inspect the server-side account record, verify my identity mapping to my existing Max account, and repair the mapping. Verification details available privately: card last 4, invoice PDFs, account creation timestamp, iPhone screenshots showing active Max plan, Console dashboard screenshot, screenshots of all three locked-out devices showing the onboarding loop.

What Should Happen?

Signing in with a verified email that maps to an existing Max account should route to the account dashboard, regardless of device or browser. The auth callback handler should never silently fall through to the new-user onboarding flow when the verified email maps to a billed existing account. At minimum, this state should surface an explicit error and route to support, not allow the user to click "Create account" and silently spawn a duplicate.

Error Messages/Logs

Steps to Reproduce

1. Have an existing Claude Max subscription with active billing
2. Sign out of claude.ai in browser, or let session expire naturally
3. Try to sign back in via email magic link OR Continue with Google in any browser (Chrome, Safari tested)
4. Observe: email is verified, but flow drops on "Let's create your account" onboarding page instead of routing to existing Max account dashboard
5. Repeat in Claude Desktop app on macOS: same behavior
6. Repeat in Claude Desktop app on Windows: same behavior
7. Confirm iOS Claude app still works normally with full Max access
8. Confirm Claude Console (platform.claude.com) still loads normally
9. Run claude --version && claude -p "ping" in Terminal on MacBook Air (Claude Code v2.1.116): receive API Error 401 invalid_credentials
10. SSH to Mac mini and run the same command (Claude Code v2.1.140): receive identical 401 invalid_credentials error

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Working until approximately May 11, 2026

Claude Code Version

Not applicable — issue is on claude.ai web and Claude Desktop, not Claude Code CLI. CLI remains authenticated.

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Cross-reference Conversation IDs:

• 215474274769576 (Fin conversation 1, May 12 09:16 PT)
• 215474280845997 (Fin / support email conversation 2, May 12 17:45 PT)

Screenshots available on request via official support channels: iPhone Settings panel showing active Max plan, Console dashboard showing intact account, three locked-out devices all showing the "Let's create your account" onboarding loop, billing page showing paid invoices.

Available to verify identity, payment, and account ownership via any official Anthropic channel.