The destructured defineStore API, named hooks and getters, createPinia(), and existing function patches remain available. New applications can use PiniaProvider; ordinary React applications may keep their activePinia setup.
| Behavior | Previous runtime | Current runtime |
|---|---|---|
| Multiple synchronous assignments | Usually one action draft commit | One commit for each real assignment |
| Writes before and after await | Different draft lifetimes | One stable mutation proxy reading latest state |
| Nested actions | An outer draft could overwrite inner changes | Each action commits independently |
| Failed action | Synchronous draft changes could roll back | Already committed writes remain |
| Array mutators | Could expose draft lifecycle differences | One logical commit per method call |
| Subscriptions | Two state arguments | Optional third MutationEvent argument |
Use $patch(fn) to make several synchronous writes atomic, or $patch(object) for shallow top-level updates. A throwing patch recipe does not commit its own draft changes. Actions themselves provide no implicit transaction or asynchronous rollback; restore flags in finally or implement explicit business recovery.
Plugins and DevTools receive every real commit. Use optional actionId and parentActionId to correlate action events; do not rely on their string format. A patch inside an action still has type patch. Getter-only dependency invalidations do not call state subscriptions.
Plain objects and arrays are the supported reactive model. Special objects retain native reads for compatibility, but internal mutation is not tracked; replace whole values through Actions/patches or use plain data. SSR snapshots must be JSON-safe. See Next.js App Router for snapshots, root Provider lifetime and client-only getStore usage.
Existing parameterless accessors remain available for single-root clients. With multiple instances, retain the Pinia at the application boundary and use getStore(pinia) in services before and after await. A supplied PiniaProvider pinia={pinia} reuses that instance; do not also pass Provider plugins or snapshots. Plain accessors do not read React Context, and Actions do not propagate an async instance context automatically.
The current core provides optional context.onDispose for plugins. Older hosts and hand-written contexts can omit it. Check the capability before acquiring resources, or retain a separate cleanup owner. The final application owner unmounts consumers before disposePinia(pinia). Disposal is irreversible, does not delete persisted data, and is not automatic on Provider unmount. See instance lifetime and plugin cleanup.