What problem does it solve? When modifying auth, admin routes, sharing, playback, or the Redis/bunny.net data layer of the Marine Video Portal, developers risk breaking hidden invariants (normalized email identity, fail-closed approval, signed embed URLs, cache invalidation) that are not obvious from the code alone. This Skill provides the design-time mental model explaining why the system is shaped the way it is before any change is designed. ## Core Features & Use Cases - Numbered invariants: Each invariant states what must hold, why, where it is enforced (file and line references), and a grep/sed command to re-verify it against the current codebase. - Known weak points: Documents accepted risks and deliberate asymmetries (e.g., approval fails closed while rate limiting fails open) so they are not accidentally "fixed". - Skill routing table: A "when NOT to use this skill" section directs users to sibling skills like change-control, security-response, or debugging-playbook for other task types. - Use Case: Before adding a new bunny.net mutation, consult invariant (f) to learn that every mutation must call invalidateVideoListCache, then verify with grep that the call-site count matches expectations. ## Quick Start Load the architecture-contract skill before designing any change to auth, admin routes, sharing, video playback, or Redis keys in the Marine Video Portal.
