> ## 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 - Go SDK

> ChatStreamDelta type definition

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

Delta changes in streaming response

## Fields

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