What problem does it solve? Redux state must survive JSON serialization and structured cloning, but values like Date, Map, Set, Error, and class instances silently break persistence, time-travel debugging, and state hydration. This Skill provides an operational checklist for keeping reducer state JSON-shaped. ## Core Features & Use Cases - Serialization Rules: Enforces primitives, arrays, and plain objects in Redux state, with timestamps stored as numbers or ISO strings and errors stored as plain data. - Collection Guidance: Replaces Map and Set with Record<string, T>, string[], or Collection<T, K> helpers for normalized entity storage. - Reducer Purity Checks: Prevents Date.now(), Math.random(), and ID generators inside reducer handlers by moving value generation into action creators or sagas. - Use Case: When adding a new reducer field that tracks sync timestamps, store syncedAtMs as a number generated in the action creator and add a JSON round-trip regression test instead of storing a Date object. ## Quick Start Ask the AI to review your reducer state and action payloads for non-serializable values like Date, Map, Set, or Error and rewrite them as JSON-safe plain data.
