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docs(query-core): document cache subscription events #11266

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docs(query-core): document cache subscription events
spaansba Aug 23, 2026
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revert console log
spaansba Aug 23, 2026
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Merge branch 'main' into docs/cache-subscription-events
spaansba Aug 23, 2026
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34 changes: 33 additions & 1 deletion docs/reference/MutationCache.md
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Original file line number Diff line number Diff line change
Expand Up @@ -79,9 +79,41 @@ const callback = (event) => {
const unsubscribe = mutationCache.subscribe(callback)
```

The callback receives a discriminated union. Check `event.type` to narrow the event and access its additional properties:

| `event.type` | When it is emitted | Properties |
| ------------------------ | --------------------------------------- | --------------------------------------------------- |
| `added` | A mutation is added to the cache | `mutation: Mutation` |
| `removed` | A mutation is removed from the cache | `mutation: Mutation` |
| `updated` | A mutation's state changes | `mutation: Mutation`, `action` |
| `observerAdded` | An observer starts observing a mutation | `mutation: Mutation`, `observer: MutationObserver` |
| `observerRemoved` | An observer stops observing a mutation | `mutation: Mutation`, `observer: MutationObserver` |
| `observerOptionsUpdated` | An observer's options change | `mutation?: Mutation`, `observer: MutationObserver` |

When `event.type` is `updated`, `event.action.type` describes the state change:

| `event.action.type` | State change | Additional properties |
| ------------------- | ------------------------------------------------ | -------------------------------------------------------------------------- |
| `pending` | A mutation starts or its pending context changes | `isPaused: boolean`, `variables?: TVariables`, `context?: TOnMutateResult` |
| `success` | A mutation succeeds | `data: TData` |
| `error` | A mutation finishes with an error | `error: TError` |
| `failed` | A mutation attempt fails and may be retried | `failureCount: number`, `error: TError \| null` |
| `pause` | A mutation is paused | |
| `continue` | A paused mutation resumes | |

For example, you can detect when a paused mutation resumes:

```tsx
const unsubscribe = mutationCache.subscribe((event) => {
if (event.type === 'updated' && event.action.type === 'continue') {
console.log('Mutation resumed', event.mutation.mutationId)
}
})
```

**Options**

- `callback: (mutation?: MutationCacheNotifyEvent) => void`
- `callback: (event: MutationCacheNotifyEvent) => void`
- This function will be called with the mutation cache any time it is updated.

**Returns**
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35 changes: 35 additions & 0 deletions docs/reference/QueryCache.md
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Original file line number Diff line number Diff line change
Expand Up @@ -96,6 +96,41 @@ const callback = (event) => {
const unsubscribe = queryCache.subscribe(callback)
```

The callback receives a discriminated union. Check `event.type` to narrow the event and access its additional properties:

| `event.type` | When it is emitted | Properties |
| ------------------------ | ------------------------------------ | ----------------------------------------- |
| `added` | A query is added to the cache | `query: Query` |
| `removed` | A query is removed from the cache | `query: Query` |
| `updated` | A query's state changes | `query: Query`, `action` |
| `observerAdded` | An observer starts observing a query | `query: Query`, `observer: QueryObserver` |
| `observerRemoved` | An observer stops observing a query | `query: Query`, `observer: QueryObserver` |
| `observerResultsUpdated` | An observer's current result changes | `query: Query` |
| `observerOptionsUpdated` | An observer's options change | `query: Query`, `observer: QueryObserver` |

When `event.type` is `updated`, `event.action.type` describes the state change:

| `event.action.type` | State change | Additional properties |
| ------------------- | ---------------------------------------------- | ------------------------------------------------------------------------ |
| `fetch` | A fetch starts | `meta?: FetchMeta` |
| `success` | Data is written after a fetch or manual update | `data: TData \| undefined`, `dataUpdatedAt?: number`, `manual?: boolean` |
| `error` | A fetch finishes with an error | `error: TError` |
| `failed` | A fetch attempt fails and may be retried | `failureCount: number`, `error: TError` |
| `pause` | A fetch is paused | |
| `continue` | A paused fetch resumes | |
| `invalidate` | The query is invalidated | |
| `setState` | The query state is updated directly | `state: Partial<QueryState<TData, TError>>` |

For example, you can detect when a paused query resumes:

```tsx
const unsubscribe = queryCache.subscribe((event) => {
if (event.type === 'updated' && event.action.type === 'continue') {
console.log('Query resumed', event.query.queryKey)
}
})
```

**Options**

- `callback: (event: QueryCacheNotifyEvent) => void`
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