> ## Documentation Index
> Fetch the complete documentation index at: https://openrouter-d02e98a0-mintlify-5b6e02fd.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# ChatStreamDelta - Python SDK

> ChatStreamDelta method reference

<Warning>
  The Python SDK and docs are currently in beta.
  Report issues on [GitHub](https://github.com/OpenRouterTeam/python-sdk/issues).
</Warning>

Delta changes in streaming response

## Fields

| Field               | Type                                                                                                        | Required             | Description                                    | Example                                                                                                                                                                           |
| ------------------- | ----------------------------------------------------------------------------------------------------------- | -------------------- | ---------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `audio`             | [Optional\[components.ChatAudioOutput\]](../components/chataudiooutput.md)                                  | :heavy\_minus\_sign: | N/A                                            | `{"data": "UklGRnoGAABXQVZFZm10IBAAAAABAAEAQB8AAEAfAAABAAgAZGF0YQoGAACBhYqFbF1f","expires_at": 1677652400,"id": "audio_abc123","transcript": "Hello! How can I help you today?"}` |
| `content`           | *OptionalNullable\[str]*                                                                                    | :heavy\_minus\_sign: | Message content delta                          | Hello                                                                                                                                                                             |
| `reasoning`         | *OptionalNullable\[str]*                                                                                    | :heavy\_minus\_sign: | Reasoning content delta                        | I need to                                                                                                                                                                         |
| `reasoning_details` | List\[[components.ReasoningDetailUnion](/client-sdks/python/api-reference/components/reasoningdetailunion)] | :heavy\_minus\_sign: | Reasoning details for extended thinking models | \[<br />`{"text": "Let me think about this...","type": "text"}`<br />]                                                                                                            |
| `refusal`           | *OptionalNullable\[str]*                                                                                    | :heavy\_minus\_sign: | Refusal message delta                          | `<nil>`                                                                                                                                                                           |
| `role`              | [Optional\[components.ChatStreamDeltaRole\]](../components/chatstreamdeltarole.md)                          | :heavy\_minus\_sign: | The role of the message author                 | assistant                                                                                                                                                                         |
| `tool_calls`        | List\[[components.ChatStreamToolCall](/client-sdks/python/api-reference/components/chatstreamtoolcall)]     | :heavy\_minus\_sign: | Tool calls delta                               |                                                                                                                                                                                   |