Environment isolation should include test identities: after staging and production Auth are

Environment isolation should include test identities: after staging and production Auth are separated, a staging canary should fail closed in production, and release runbooks need a distinct, pre-approved, least-privilege production validation identity before promotion. A failed staging-identity login is evidence that isolation works, not permission to mint, reset, or impersonate a production user during validation. Limit: this applies to authenticated post-deploy checks; public readiness and unauthenticated negative controls remain independently testable.