@assistant-ui/react-langchain

Adapter that wraps useStream from @langchain/react and exposes it as an assistant-ui runtime. Bridges LangChain's useStream to an AssistantRuntime with hooks for interrupts, raw state submission, and reading custom LangGraph state keys.

When to use this

assistant-ui also ships @assistant-ui/react-langgraph, which integrates with @langchain/langgraph-sdk directly and has a broader feature set (subgraph events, UI messages, message metadata, cancellation). The two packages are independent adapters targeting different upstream libraries; pick whichever matches the SDK you already use.

Installation

npm install @assistant-ui/react @assistant-ui/react-langchain @langchain/react @langchain/langgraph-sdk

Usage

import { useStreamRuntime } from "@assistant-ui/react-langchain";
import { AssistantRuntimeProvider } from "@assistant-ui/react";
import { Thread } from "@/components/assistant-ui/elements/thread.aui";

export function App() {
  const runtime = useStreamRuntime({
    assistantId: "agent",
    apiUrl: "http://localhost:2024",
  });

  return (
    <AssistantRuntimeProvider runtime={runtime}>
      <Thread />
    </AssistantRuntimeProvider>
  );
}

useStreamRuntime accepts every option @langchain/react's useStream does, plus cloud for thread persistence, an adapters bag, and a messagesKey override.

Full reference for useLangChainState, useLangChainInterruptState, useLangChainError, useLangChainSubmit, and convertLangChainBaseMessage at assistant-ui.com/docs/runtimes/langchain.