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

# response.output_text.delta

Streams incremental assistant text output, including text associated with spoken RTC media. The first delta for an `item_id` and `output_index` implicitly introduces that streamed text item.

## Event fields

<ResponseField name="event_id" type="string" required>
  Unique id for this server event.
</ResponseField>

<ResponseField name="type" type="string" required>
  Event type. Must be `response.output_text.delta`.
</ResponseField>

<ResponseField name="response_id" type="string" required>
  The ID of the response.
</ResponseField>

<ResponseField name="item_id" type="string" required>
  The ID of the message item receiving text. If the client has not seen this item before, create it from this event and finalize it with `response.output_item.done`.
</ResponseField>

<ResponseField name="output_index" type="number" required>
  The index of the output item in the response.
</ResponseField>

<ResponseField name="delta" type="string" required>
  Incremental text.
</ResponseField>

<ResponseExample>
  ```json response.output_text.delta theme={null}
  {
    "event_id": "evt_text_delta_001",
    "type": "response.output_text.delta",
    "response_id": "resp_001",
    "item_id": "item_003",
    "output_index": 0,
    "delta": "This model"
  }
  ```
</ResponseExample>