## What changed
- Prefer stored enterprise credentials when available; otherwise use a validated Codex account OAuth grant whose issuer matches the enterprise MCP configuration.
- Pin each connection to its credential source and OAuth client, reject stale account grants, and hold the account refresh lease only during the IdP exchange.
- Report actionable sign-in and issuer configuration errors, and classify token failures by credential source.
GitOrigin-RevId: 26673f276a31e4ca5290f6b120f0ac44c77d7239