---
title: "Reference: Run.observeStream() | Streaming"
description: Documentation for the `Run.observeStream()` method in workflows, which enables reopening the stream of an already active workflow run.
packages:
  - "@mastra/core"
---

# Run.observeStream()

The `.observeStream()` method opens a new `ReadableStream` to a workflow run that is 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](/docs/v1/workflows/overview#running-workflows)
- [Workflow.createRun()](/reference/v1/workflows/workflow-methods/create-run)
- [Run.stream()](./stream)
- [Run.resumeStream()](./resumeStream)
