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Monitor every deployment and call.

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Deployment

Each deployment generates a unique ID. View logs in the console.
Sample Deployment Logs

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Call Logs

You can click into a call and view any logging statements generated by your reasoning code.

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Transcripts

Each call has a transcript with independently separated transcribed audio and text to be generated. When you export these transcripts with the API or CLI, these include more granular turn level timestamps.
Sample Call Transcripts

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Loggable Events

Record events without tying them to tool calls.

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SDK

In the SDK, yield LogMessage events from your agent or tools to record custom events: 
from line.events import LogMessage

@loopback_tool
async def process_order(ctx, order_id: Annotated[str, "Order ID"]):
    """Process a customer order."""
    result = await api.process_order(order_id)

    # Log a custom event
    yield LogMessage(
        name="order_processed",
        level="info",
        message=f"Processed order {order_id}",
        metadata={"status": result.status, "order_id": order_id}
    )

    return f"Order {order_id} processed: {result.status}"
Events are automatically sent to the platform when yielded.

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Websocket

If you’re not using the SDK and instead just relying on the bare websocket, logging events will look like this: 
{
  "type": "log_event",
  "event": "event_name",
  "metadata": {
    "key": "value"
  }
}

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Playground

You can view these events in the Playground under the Transcript tab of the call.

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Loggable Metrics

Record metrics at any point in your workflow.

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SDK

In the context of the SDK, we can log a metric by broadcasting the LogMetric event. Here’s a snippet from the form filling template that exhibits this: 
# Record the answer in form manager
success = self.form_manager.record_answer(answer)

if success:
  # Log metric for the answered question
  if current_question:
    metric_name = current_question["id"]
    yield LogMetric(name=metric_name, value=answer)
    logger.info(f"📊 Logged metric: {metric_name}={answer}")
The user bridge is subscribed to the LogMetric event by default, and it will log it over the websocket by default when it sees that LogMetric has been broadcast.

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Websocket

If you’re not using the SDK and instead just relying on the bare websocket, logging metrics will look like this: 
{
  "type": "log_metric",
  "name": "metric_name",
  "value": "metric_value"
}

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Playground

You can view these events in the Playground under the Transcript tab of the call.
Loggable Metrics in the Playground

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Call Recordings

Call recordings can be downloaded from the playground.
Sample Call Recordings

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Webhooks

A webhook can be sent to a configurable endpoint when a call starts, completes or fails. Each payload includes the full transcript of the conversation.
Sample Call Webhooks
In your webhook handler, be sure to verify that all incoming requests have an x-webhook-secret header set to this secret value, to verify that the requests are coming from Cartesia. A sample payload is listed below. 
{
  "type": "call_completed | call_failed | call_started",
  "request_id": "MZ4958bfe4940bf0ef6cc92f8c6cfa1a1f",
  "agent_id": "agent_demo",
  "webhook_id": "agent_webhook_P3MgdLf1cpaucZJ7xWehCC",
  "body": [
    {
      "end_timestamp": 10.387875000000001,
      "role": "assistant",
      "start_timestamp": 1.175,
      "text": "Hi there! I'm Savannah, a voice agent built on Cartesia's new Voice Agents platform. Who do I have the pleasure of speaking with today?",
      "tts_ttfb": 0.20372509956359863
    }
  ],
  "timestamp": "2025-06-24T23:36:40.360473878Z"
}