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

# Streaming Events

> Reference for ChatStreamEvent, StreamMessageMetadata, ToolCallInfo, and related streaming types.

## ChatStreamEvent

`sealed interface ChatStreamEvent` — **Package:** `com.chatbase.sdk.streaming`

Events emitted by `sendMessageStream()` and `retryStream()`.

<Tabs>
  <Tab title="Text Events" icon="font">
    ### TextStart

    A new text block is starting.

    ```kotlin theme={null}
    data class TextStart(val id: String) : ChatStreamEvent
    ```

    ### TextDelta

    An incremental text chunk. Append to the current text.

    ```kotlin theme={null}
    data class TextDelta(val id: String, val delta: String) : ChatStreamEvent
    ```

    ### TextEnd

    The current text block is complete.

    ```kotlin theme={null}
    data class TextEnd(val id: String) : ChatStreamEvent
    ```
  </Tab>

  <Tab title="Tool Events" icon="bolt">
    ### ToolInputStart

    A tool call is starting — input will stream incrementally.

    ```kotlin theme={null}
    data class ToolInputStart(
        val toolCallId: String,
        val toolName: String
    ) : ChatStreamEvent
    ```

    ### ToolInputDelta

    Incremental tool input text.

    ```kotlin theme={null}
    data class ToolInputDelta(
        val toolCallId: String,
        val inputTextDelta: String
    ) : ChatStreamEvent
    ```

    ### ToolInputAvailable

    The tool call's full input is ready.

    ```kotlin theme={null}
    data class ToolInputAvailable(
        val toolCallId: String,
        val toolName: String,
        val input: JsonElement
    ) : ChatStreamEvent
    ```

    <Tip>Read the full `input` object directly from this event — no need to concatenate preceding deltas.</Tip>

    ### ToolOutputAvailable

    A tool's execution result is available.

    ```kotlin theme={null}
    data class ToolOutputAvailable(
        val toolCallId: String,
        val output: JsonElement
    ) : ChatStreamEvent
    ```
  </Tab>

  <Tab title="Step & Lifecycle" icon="flag-checkered">
    ### StepStart / StepFinish

    ```kotlin theme={null}
    object StepStart : ChatStreamEvent
    object StepFinish : ChatStreamEvent
    ```

    ### Start

    The message stream is starting.

    ```kotlin theme={null}
    data class Start(
        val messageId: String?,
        val messageMetadata: StreamMessageMetadata?
    ) : ChatStreamEvent
    ```

    ### Finish

    The stream is complete.

    ```kotlin theme={null}
    data class Finish(
        val finishReason: String,
        val messageMetadata: StreamMessageMetadata?
    ) : ChatStreamEvent
    ```

    `finishReason` is usually `"stop"`, `"error"`, or `"tool-calls"`. Other values (`"length"`, `"content-filter"`, `"other"`, `"unknown"`) are possible and map to `FinishReason.UNKNOWN` in the aggregated `ChatResponse`.

    ### MessageMetadataEvent

    Updated metadata arrived mid-stream.

    ```kotlin theme={null}
    data class MessageMetadataEvent(
        val messageMetadata: StreamMessageMetadata
    ) : ChatStreamEvent
    ```
  </Tab>

  <Tab title="Error" icon="triangle-exclamation">
    ### Error

    An error occurred during streaming.

    ```kotlin theme={null}
    data class Error(val exception: ChatbaseException) : ChatStreamEvent
    ```

    The `exception` may be an `ApiException` or `NetworkException`. See [Error Handling](/docs/android-sdk/error-handling).
  </Tab>
</Tabs>

## StreamMessageMetadata

`data class StreamMessageMetadata` — **Package:** `com.chatbase.sdk.streaming`

Accompanies `Start`, `Finish`, and `MessageMetadataEvent` events.

```kotlin theme={null}
data class StreamMessageMetadata(
    val messageId: String?,
    val userMessageId: String?,
    val conversationId: String?,
    val usage: StreamUsage?
)
```

### StreamUsage

```kotlin theme={null}
data class StreamUsage(val credits: Double = 0.0)
```

## ToolCallInfo

`data class ToolCallInfo` — **Package:** `com.chatbase.sdk`

Passed to the `onToolCall` callback before handler execution.

```kotlin theme={null}
data class ToolCallInfo(
    val toolCallId: String,
    val toolName: String,
    val input: JsonElement
)
```

```kotlin theme={null}
fun inputAsMap(): Map<String, Any?>
```

Parse the JSON input into a `Map<String, Any?>` for easy access.

## ToolResultInfo

`data class ToolResultInfo` — **Package:** `com.chatbase.sdk`

Passed to the `onToolResult` callback after handler execution.

```kotlin theme={null}
data class ToolResultInfo(
    val toolCallId: String,
    val toolName: String,
    val output: Any
)
```

```kotlin theme={null}
fun outputAsString(): String
```

Serialize the output to a JSON string.