ResponseReasoningSummaryPartAddedEvent

Emitted when a new reasoning summary part is added.

{
    "type": "response.reasoning_summary_part.added",
    "item_id": "string",
    "output_index": 0,
    "summary_index": 0,
    "part": {
        "type": "summary_text",
        "text": "string"
    }
}