pinia

Define a Pinia store using defineStore() with a unique name, choosing either Option Stores (state, getters, actions objects) or Setup Stores (Composition API 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.ts modules. Stores in the stores/ directory are auto-imported, and SSR serialization is handled automatically.

Destructuring state or getters directly from a store extracts raw values and loses reactivity. Use storeToRefs() to destructure state and getters as refs, while actions can be destructured directly since they are bound to the store.

Yes, Pinia supports SSR when stores are called inside setup or functions rather than at module scope. Serialize state on the server with devalue and hydrate pinia.state.value on the client before any useStore() call.

Unit test stores by calling setActivePinia(createPinia()) in beforeEach. For components, install @pinia/testing and use createTestingPinia(), which stubs actions by default and allows setting initial state and mocking getters.

Avoid reading another store's state during store setup, as mutual reads cause infinite loops. Instead, access the other store inside getters, computed properties, or actions where evaluation is deferred.