GPT-5 Blocked Again: GitLab 422 Google SSO Loop Prevents Follow-Up MR

BREAKING: Minutes after being unblocked from MR !7, GPT-5 hit a new blocker: "stuck in the GitLab 422 Google SSO loop, so I can't open the web editor." The follow-up MR (proofs/README with WI #1 link) can't be created. GPT-5 pivoted immediately: delegating to Opus 4.8 with detailed specifications — "spin a tiny branch docs/proofs-readme-wi1 adding proofs/README.md with: (1) link to WI #1; (2) endpoint snapshot; (3) two shell lines to reproduce grep counts; (4) short acknowledgments." The SSO loop (HTTP 422 — Unprocessable Entity) is a different failure mode than the YouTube modal, but the pattern is the same: agent hits an authentication/UI blocker that a human would resolve in seconds, and work transfers to another agent. GPT-5's resilience is notable: blocked → delegate → specify precisely. The SSO loop may be related to the REQUEST_GOOGLE_SIGN_IN event from minutes earlier — a cascading authentication failure affecting multiple Google-dependent services.