[Bug] OAuth login redirects to account creation instead of authenticating existing Max subscription

Bug Description
Title: Claude Max subscriber redirected to "Create account" instead of logging in via OAuth

Description:
Running claude auth login --claudeai --email mattinaviation@gmail.com opens the browser, verifies the email
successfully, but then shows "Let's create your account" instead of authenticating the existing account.

The Max subscription (£90/month) is active and being charged. No account record appears to exist in Anthropic's
backend linked to this email, despite the subscription existing. This has been broken for 15+ days.

Steps to reproduce:

1. Run claude auth login --claudeai
2. Email is verified as mattinaviation@gmail.com
3. Browser shows "Let's create your account" with a "Create account" button
4. No way to log in — only option is to create a duplicate account

Expected: OAuth completes and Claude Code authenticates against existing Max subscription

Actual: Redirected to account creation flow

Claude Code version: 2.1.85

Platform: macOS

Environment Info

• Platform: darwin
• Terminal: Apple_Terminal
• Version: 2.1.84
• Feedback ID: 19bf740f-dee2-405b-959b-0f343fbfed7b

Errors

[{"error":"Error: File does not exist. Note: your current working directory is /Users/msdeyncourtharvey.\n    at call (/$bunfs/root/src/entrypoints/cli.js:4493:6118)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-03-26T09:10:02.601Z"},{"error":"AxiosError: Request failed with status code 404\n    at yp (/$bunfs/root/src/entrypoints/cli.js:123:1194)\n    at <anonymous> (/$bunfs/root/src/entrypoints/cli.js:128:12755)\n    at emit (node:events:92:22)\n    at endReadableNT (internal:streams/readable:861:50)\n    at processTicksAndRejections (native:7:39)\n    at request (/$bunfs/root/src/entrypoints/cli.js:130:2467)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-03-26T13:57:36.051Z"},{"error":"AxiosError: Request failed with status code 404\n    at yp (/$bunfs/root/src/entrypoints/cli.js:123:1194)\n    at <anonymous> (/$bunfs/root/src/entrypoints/cli.js:128:12755)\n    at emit (node:events:92:22)\n    at endReadableNT (internal:streams/readable:861:50)\n    at processTicksAndRejections (native:7:39)\n    at request (/$bunfs/root/src/entrypoints/cli.js:130:2467)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-03-26T13:57:40.010Z"},{"error":"Error: File does not exist. Note: your current working directory is /Users/msdeyncourtharvey.\n    at call (/$bunfs/root/src/entrypoints/cli.js:4493:6118)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-03-26T14:35:30.658Z"},{"error":"Error: Fil…

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