Stop seeding stale Codex OAuth model metadata so connected accounts use the upstream /models response instead of the retired gpt-5.2-codex default.
Use gpt-5.5 as the Codex proxy fallback model, omit the fake legacy client version when Codex CLI is unavailable, and remove the stale Copilot fallback entry.
Add focused OAuth regressions for the current default model, upstream model-list behavior, and Copilot fallback ordering.