> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cyberwave.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Recorder node

> Start or stop audio/video recording on a twin via the media service from a workflow.

The **Recorder** (`recorder`) node publishes `start_recording` / `stop_recording` to a twin's `webrtc-command` MQTT topic so the media service persists the **already-running** WebRTC stream to its configured bucket. The node never carries the media itself — the camera or microphone must already be streaming.

<Note>
  **Palette category:** Actuation. **Edge-only.** Toggles persistence on the media service; it does not create the stream.
</Note>

<Tip>
  The Recorder node, the audio widget's **REC** button in the environment view, and the [microphone driver's fallback relay](/feature-reference/edge/drivers/native-microphone-driver) all publish the exact same payload on `cyberwave/twin/{uuid}/webrtc-command`. The three paths converge on the same media-service handler and the same `webrtc-command/status` ACK, so you can mix and match without changing the consumer.
</Tip>

## Inputs

| Field                | Type   | Required | Description                                                                                                                                        |
| -------------------- | ------ | -------- | -------------------------------------------------------------------------------------------------------------------------------------------------- |
| `twin_uuid`          | string | Yes      | Twin whose stream should be recorded. Defaults to the workflow's bound twin.                                                                       |
| `command`            | string | Yes      | `start_recording` or `stop_recording`. Wire from an upstream Conditional / Fuzzy Matcher to toggle dynamically, or pin a literal in the inspector. |
| `frontend_type`      | string | Yes      | `video` or `audio`. The media service treats this as `audio` when unset.                                                                           |
| `sensor`             | string | Yes      | Sensor identifier (e.g. `camera`, `mic`). Required by the media-service `start_recording` handler — commands without it are refused.               |
| `stream_source`      | string | No       | Optional producer hint (e.g. `camera`).                                                                                                            |
| `stream_instance_id` | string | No       | Optional disambiguator when a twin publishes multiple streams under the same sensor.                                                               |

## MQTT payload

Published to `{prefix}cyberwave/twin/{twin_uuid}/webrtc-command` with QoS 1:

```json theme={null}
{
  "command": "start_recording",
  "source_type": "edge",
  "sensor": "camera",
  "frontend_type": "video",
  "stream_source": "camera",
  "stream_instance_id": "primary"
}
```

To stop, send the same payload with `"command": "stop_recording"`. Status is published back by the media service on `{prefix}cyberwave/twin/{twin_uuid}/webrtc-command/status`.

## Outputs

| Field     | Type    | Description                                   |
| --------- | ------- | --------------------------------------------- |
| `command` | string  | Recording command that was published.         |
| `topic`   | string  | Full MQTT topic the command was published to. |
| `payload` | object  | Payload sent to the media service.            |
| `sent`    | boolean | Whether the broker accepted the publish.      |

## Execution targets

| Target    | Behavior                                                                                                        |
| --------- | --------------------------------------------------------------------------------------------------------------- |
| **Edge**  | Emitter renders a `client.mqtt.publish` against the twin-scoped `webrtc-command` topic in the generated worker. |
| **Cloud** | Not supported — the node raises at compile time for cloud workflows.                                            |

## Related

* [Audio in workflows](/feature-reference/workflows/audio-in-workflows)
* [Virtual Controller](/feature-reference/workflows/virtual-controller) — generic controller actuation publisher
* [Send MQTT](/feature-reference/workflows/edge-dependencies) — generic edge-side MQTT publish