XState Store

Targets @xstate/store v4 and @xstate/store-react v2 (TypeScript 5.4+). Read the reference matched by the API or behavior being changed. Load adjacent references only for concerns the change crosses; reuse relevant context already read.

Pick the primitive first

State	Primitive	Why
Domain state updated through named events	createStore({ context, on })	Typed trigger, can, emitted events, replayable transitions
Per-instance state built from input	createStoreLogic({ context: (input) => … })	One definition, many instances; selectors come along
A single value set directly	createAtom(value)	No event vocabulary to justify a store
A value computed from other atoms or selectors	createAtom(() => …)	Read-only, recomputes on dependency change
Modes, guards, delays, hierarchical or parallel states	xstate machine	A store models data, not lifecycle

Done when: the primitive is chosen from this table and its justification holds.

Branches

When you are…	Reference
Creating a store, writing transitions, using trigger/send/can, or Immer	references/store-core.md
Enqueuing effects, emitting events, or doing async work	references/effects-and-events.md
Declaring schemas or turning on runtime validation	references/schemas-and-validation.md
Reading state with store.select, atoms, derived/async/reducer atoms	references/selectors-and-atoms.md
Building reusable/per-instance stores with createStoreLogic, input, or selectors	references/store-logic-and-input.md
Adding persist, undoRedo, reset, or composing .with(...)	references/extensions.md
Wiring a store into React components	references/react.md
Testing transitions, inspecting a store, or interoperating with XState	references/testing-and-interop.md
Upgrading a v3 store to v4, or porting an existing Zustand store over	references/migration-v4.md

Apply the technical rules relevant to the changed behavior.

Tripwires

Transitions — return the complete next context (spread the old one); return undefined to mark an event disallowed, which is what store.can.*() reports.

Effects — call enqueue.effect, enqueue.emit.*, and enqueue.trigger.* synchronously inside the transition; async work goes inside enqueue.effect(async () => …) and reports back by triggering another event.

Imports — framework bindings come from @xstate/store-react (and siblings), never @xstate/store/react; extensions come from @xstate/store/persist, /undo, /reset, /validate.

Schemas — schemas types the store; only .with(validateSchemas()) validates at runtime.

Atoms — computed atoms read dependencies via .get(); their first parameter is the previous computed value, so annotate createAtom<T>(…) when using it.

React — module-scoped stores for app-wide state, useStore(logic, input) for component-scoped state; subscribe through useSelector/useAtom rather than getSnapshot().