assistant-stream

Framework-agnostic streaming primitives for AI assistant backends. Defines a chunked stream of typed events (text, tool calls, tool results, data parts, message metadata), encoders/decoders for several wire formats, and a server-side tool execution pipeline. Runs in any standard JavaScript runtime; no React or DOM dependencies.

Most apps reach assistant-stream indirectly through @assistant-ui/react-ai-sdk or @assistant-ui/react-data-stream, which handle the wire format for you. Install it directly when you are building a custom backend or a new integration package.

Installation

npm install assistant-stream

Usage

import { createAssistantStreamResponse } from "assistant-stream";

export async function POST(request: Request) {
  return createAssistantStreamResponse(async (controller) => {
    const text = controller.appendText();
    text.append("Hello, ");
    text.append("world!");
    text.close();
  });
}

For tool execution, pipe through ToolExecutionStream; for resumable streams (clients can reconnect and replay), import from the assistant-stream/resumable sub-path with a redis or ioredis adapter.

Sub-paths

., ./utils, ./resumable, ./resumable/redis, ./resumable/ioredis. The two Redis adapters are optional peer dependencies; install whichever client your stack already uses.

Full reference for encoders, tool execution, message conversion, and resumable streams at assistant-ui.com/docs/architecture.