# Background task streaming

**Added in:** `@mastra/core@1.29.0`

`mastra.backgroundTaskManager.stream()` returns a `ReadableStream` of [background task](https://mastra.ai/docs/agents/background-tasks) lifecycle events. Use it to monitor running tasks across the system, for example to drive a status dashboard, surface progress in your own UI, or pipe events into an SSE response.

The stream emits the same chunk types that appear inside `Agent.streamUntilIdle()` (`background-task-running`, `background-task-output`, `background-task-completed`, `background-task-failed`, `background-task-cancelled`). See [background task chunks](https://mastra.ai/reference/streaming/ChunkType) for the full payload shapes.

> **Note:** Background tasks must be [enabled on the Mastra instance](https://mastra.ai/reference/configuration) before `backgroundTaskManager` is available. When disabled, `mastra.backgroundTaskManager` is `undefined`.

## Subscribe to all task events

Calling `stream()` with no filter returns a stream of every task event in the system. On connection, the stream emits a snapshot of all currently running tasks, then forwards live events as they happen.

```typescript
const bgManager = mastra.backgroundTaskManager
if (!bgManager) throw new Error('Background tasks are not enabled')

const controller = new AbortController()
const stream = bgManager.stream({ abortSignal: controller.signal })

for await (const chunk of stream) {
  switch (chunk.type) {
    case 'background-task-running':
      console.log('started', chunk.payload.taskId, chunk.payload.toolName)
      break
    case 'background-task-completed':
      console.log('done', chunk.payload.taskId, chunk.payload.result)
      break
    case 'background-task-failed':
      console.error('failed', chunk.payload.taskId, chunk.payload.error)
      break
  }
}
```

The stream stays open until the caller's `AbortSignal` fires. Always pass an `abortSignal` so you can disconnect cleanly.

## Filter the stream

Pass any combination of filter options to narrow the events you receive. Filters apply to both the initial snapshot and the live event subscription.

```typescript
const stream = bgManager.stream({
  agentId: 'researcher',
  threadId: 't1',
  resourceId: 'u1',
  abortSignal: controller.signal,
})
```

| Filter        | Description                                         |
| ------------- | --------------------------------------------------- |
| `agentId`     | Only events from tasks dispatched by this agent     |
| `runId`       | Only events from this specific agent run            |
| `threadId`    | Only events from tasks scoped to this memory thread |
| `resourceId`  | Only events from tasks scoped to this resource      |
| `taskId`      | Only events for a single task                       |
| `abortSignal` | Closes the stream when the signal aborts            |

## Look up task state directly

For one-off lookups instead of a live stream, use `getTask` and `listTasks`:

```typescript
const task = await mastra.backgroundTaskManager?.getTask(taskId)
const { tasks, total } = await mastra.backgroundTaskManager?.listTasks({
  status: 'running',
  agentId: 'researcher',
})
```

These read from storage rather than the pubsub stream, so they're suitable for paginated lists and detail views.

## Related

- [Background tasks](https://mastra.ai/docs/agents/background-tasks)
- [`Agent.streamUntilIdle()` reference](https://mastra.ai/reference/streaming/agents/streamUntilIdle)
- [Background task chunks](https://mastra.ai/reference/streaming/ChunkType)
- [backgroundTasks configuration reference](https://mastra.ai/reference/configuration)