@mastra/core/dist/docs/references/reference-streaming-workflows-observeStream.md

Mastra is a framework for building AI-powered applications and agents with a modern TypeScript stack.

# Run.observeStream()

The `.observeStream()` method opens a new `ReadableStream` to a workflow run that's currently running, allowing you to observe the stream of events if the original stream is no longer available.

## Usage example

```typescript
const run = await workflow.createRun()

run.stream({
  inputData: {
    value: 'initial data',
  },
})

const stream = await run.observeStream()

for await (const chunk of stream) {
  console.log(chunk)
}
```

## Returns

`ReadableStream<ChunkType>`

## Stream events

The stream emits various event types during workflow execution. Each event has a `type` field and a `payload` containing relevant data:

- **`workflow-start`**: Workflow execution begins
- **`workflow-step-start`**: A step begins execution
- **`workflow-step-output`**: Custom output from a step
- **`workflow-step-result`**: A step completes with results
- **`workflow-finish`**: Workflow execution completes with usage statistics

## Related

- [Workflows overview](https://mastra.ai/docs/workflows/overview)
- [Workflow.createRun()](https://mastra.ai/reference/workflows/workflow-methods/create-run)
- [Run.stream()](https://mastra.ai/reference/streaming/workflows/stream)
- [Run.resumeStream()](https://mastra.ai/reference/streaming/workflows/resumeStream)