Migrating to 4.0

Native local applications using actions, selectors and getters generally keep the same APIs. Use React 18 or 19, and check imports wherever state crosses a JavaScript context. The repository migration guide contains the extended adapter and local graph contracts.

Select the owning entry

The old coaction/local and @coaction/react/local aliases are gone. Shared stores that previously used a default entry must switch to /shared:

-import { create } from '@coaction/react';
+import { create } from '@coaction/react/shared';

 const store = create(source, { worker });

The default entries reject non-null shared options such as worker, transport and clientTransport. An explicitly undefined option is accepted for feature detection and SSR. Local imports exclude the shared transport runtime from the bundle.

Check low-level writes and middleware

Both store.apply(nextState) and store.apply(base, patches) publish commits. With patches, the base must be current: omit it with apply(undefined, patches) or use getPureState(). A wrong base throws before changing state or publishing a commit.

-store.apply(otherState, patches);
+store.apply(store.getPureState(), patches);

Adapter authors must leave store.apply owned by Coaction and provide internal.externalApply for their runtime writer. Middleware should use StoreCommit hooks to observe all supported transitions, including writes that do not pass through apply.

Do not assume every patch pair contains leaf paths. Positional edits can fall back to replacement patches at changed top-level keys; local object graphs can need a root snapshot at path: []. Replay must preserve the committed values and reference topology. Local cycles are supported as complete values during initialization or replacement. Creating cycles from draft references and editing within cyclic drafts remain outside the recipe contract. These local guarantees do not extend the shared JSON contract.

Check React and computed assumptions

React 18 and 19 are supported and tested. React 17 is outside the peer range. Server-side selectors read current state, consistent with whole-state and observer readers. Use getInitialState() explicitly if initial state is what the application needs, and create request-scoped stores with matching server and client hydration data.

Native getters retain store/slice field dependencies. React selectors and observer use deep path tracking; derive(..., { deep: true }) opts a managed computed selector into deep tracking. See computed state for identity, lifecycle and invalidation boundaries.

Check remote synchronization

@coaction/sync requires durable storage and JSON state. Unsupported local writes are refused before committing. Checkpoints include formatVersion; unsupported versions and malformed checkpoints are rejected without overwriting them. Legacy checkpoints without a version are read as format 1.

Review the CRUD, Supabase and Firestore adapter READMEs when upgrading those integrations: the CRUD adapter retains the remote base, Supabase applies the configured schema to reads and writes, and Firestore separates its read source from its write address. See remote synchronization for configuration and failure handling.

Reactive tracking, shared authority and remote synchronization are separate capabilities. A local store can sync to a server without a Worker. Shared mirrors follow one authority; they do not independently diverge and merge like remote replicas.