xState v5 : subscribe to snapshot does not trigger when an invoked actor change state

[florian-mollin-wanteeed]

To persist an actor's snapshot, we use the following code from the doc:

const persistedState = JSON.parse(localStorage.getItem('some-persisted-state'));

const actor = createActor(someLogic, {
  snapshot: persistedState,
});

actor.subscribe(() => {
  localStorage.setItem(
    'some-persisted-state',
    JSON.stringify(actor.getPersistedSnapshot()),
  );
});

// Actor will start at persisted state
actor.start();

Our actor uses an invoked machine actor.
We need to persist the whole state (main + sub machines) whenever either machine changes states. However, with the current code, it only does so when the main machine changes state.
Is there a way to achieve our desired behaviour?

[davidkpiano]

Yes, use the inspect API:

actor.system.inspect(inspectionEvent => {
  // This is called whenever anything happens in any actor within the system
})

https://stately.ai/docs/inspection