Stream

The stream layer exposes provider.StreamPart events and helper readers.

Overview

Go AI SDK supports streaming of:

Text deltas
Tool calls
Tool results
Finish state and usage
Error events

StreamReader

Creating a Stream Reader

reader := stream.NewStreamReader(ctx)

Methods

Method	Description
`Part()`	Returns channel of stream parts
`Close()`	Closes the stream
`Err()`	Returns any error

StreamPart Types

type StreamPart struct {
    Type           string
    Text           string
    ToolCallID     string
    ToolName       string
    ToolInput      string
    ToolInputDelta string
    ToolResult     string
    FinishReason   string
    Usage          Usage
    Error          error
}

Part Types

Type	Description
`text-delta`	Text content chunk
`text-start`	Start of text block
`text-end`	End of text block
`tool-call`	Tool call request
`start`	Agent stream started
`step-start`	Agent loop step started
`tool-input-start`	Start of tool input
`tool-input-delta`	Tool input chunk
`tool-result`	Tool execution result
`finish`	Stream finished
`error`	Error occurred

Usage

Reading Stream

stream, err := agent.Stream(ctx, agent.AgentCallOptions{
    Prompt: "Your prompt here",
})

if err != nil {
    panic(err)
}

for part := range stream.Part() {
    switch part.Type {
    case "text-delta":
        fmt.Print(part.Text)
    case "tool-call":
        fmt.Printf("Tool: %s\n", part.ToolName)
    case "tool-result":
        fmt.Printf("Result: %s\n", part.ToolResult)
    case "finish":
        fmt.Printf("Done: %s\n", part.FinishReason)
    case "error":
        fmt.Printf("Error: %v\n", part.Error)
    }
}

Accumulated Values

stream, err := agent.Stream(ctx, agent.AgentCallOptions{
    Prompt: "Your prompt here",
})

// Wait for stream to complete or read in chunks
text := stream.Text()
toolCalls := stream.ToolCalls()
finishReason := stream.FinishReason()
usage := stream.Usage()

TextStreamWriter

For building custom streams:

writer := stream.NewTextStreamWriter()
writer.OnChunk(func(chunk string) {
    fmt.Print(chunk)
})
writer.OnFinish(func(text string) {
    fmt.Println("\nFinal:", text)
})

writer.WriteChunk("Hello ")
writer.WriteChunk("World")
writer.Close()

SSE Support

The stream module includes helpers for parsing JSON stream payloads:

parts, err := stream.ParseSSEStream(reader)
for _, part := range parts {
    fmt.Println(part.Type, part.Text)
}