assistant-ui--assistant-ui/templates/langchain/backend/agent.ts

import { ChatAnthropic } from "@langchain/anthropic";
import { MessagesAnnotation, StateGraph } from "@langchain/langgraph";

const model = new ChatAnthropic({
  model: process.env.ANTHROPIC_MODEL ?? "claude-sonnet-4-6",
  streaming: true,
});

const callModel = async (state: typeof MessagesAnnotation.State) => {
  const response = await model.invoke(state.messages);
  return { messages: [response] };
};

export const graph = new StateGraph(MessagesAnnotation)
  .addNode("agent", callModel)
  .addEdge("__start__", "agent")
  .addEdge("agent", "__end__")
  .compile();