pinia

Define a Pinia store with defineStore() using either the Option Store syntax (state, getters, actions objects) or the Setup Store syntax with ref, computed, and functions. Setup Stores are recommended for complex logic and composables.

Install the @pinia/nuxt module with nuxi module add pinia, then add it to nuxt.config modules. Stores in the stores directory are auto-imported, and SSR serialization plus XSS protection are handled automatically.

Destructuring state or getters directly from a store loses reactivity because they are plain values. Use storeToRefs() to extract state and getters as refs; actions can be destructured directly since they are bound to the store.

Install @pinia/testing and mount components with createTestingPinia() as a global plugin. Actions are stubbed by default, initial state can be injected, and getters can be overridden directly in tests.

Yes, Pinia supports SSR by calling stores inside setup or functions rather than module scope, and passing the pinia instance to useStore() in guards. Serialize state with devalue on the server and hydrate pinia.state.value on the client before any useStore call.