persist-mobx

name	persist-mobx
description	Persist a MobX observable object with @stainless-code/persist (persistObservable). Use when wiring MobX state to localStorage/sessionStorage/IndexedDB under enforceActions.
license	MIT
metadata	{"type":"composition","library":"@stainless-code/persist","library_version":"0.4.1","framework":"mobx"}
sources	["stainless-code/persist:src/adapters/sources/mobx.ts","stainless-code/persist:docs/architecture.md"]

Persisting MobX

@stainless-code/persist/sources/mobx maps an observable object through toJS / runInAction+Object.assign / observe onto persistSource.

When to use this skill

• You have observable.object({…}) (or compatible object observable) and want reload survival.
• You use configure({ enforceActions: "always" }) — hydrate must run inside an action.

Install

bun add @stainless-code/persist mobx

mobx is an optional peer of /sources/mobx.

Minimal wiring

import { observable } from "mobx";
import { createJSONStorage } from "@stainless-code/persist";
import { persistObservable } from "@stainless-code/persist/sources/mobx";

const prefs = observable.object({ theme: "light" as const });
const persist = persistObservable(prefs, {
  name: "app:prefs:v1",
  storage: createJSONStorage(() => localStorage),
});

Hydrate semantics

Hydrate uses runInAction(() => Object.assign(observable, next)). Bare assign would throw under enforceActions: "always". Keys absent from next are not deleted (same as valtio).

Common mistakes

• Writing hydrate outside actions in custom persistSource ports — this adapter already wraps runInAction.
• Class instances / primitives as the persist root — target is an object observable.
• Expecting deep replace from Object.assign alone.

API surface

• persistObservable(observable, options) → PersistApi
• Options / PersistApi: same as persistSource

See also: persist-valtio — same object + assign hydrate pattern without MobX actions.