create-agent-chat-app/templates/research-agent/retrieval-graph/researcher-graph/graph.ts

Create a LangGraph chat app with one command

/**
 * Researcher graph used in the conversational retrieval system as a subgraph.
 * This module defines the core structure and functionality of the researcher graph,
 * which is responsible for generating search queries and retrieving relevant documents.
 */

import { StateGraph, END, START, Send } from "@langchain/langgraph";
import { z } from "zod";

import { RunnableConfig } from "@langchain/core/runnables";
import { ensureAgentConfiguration } from "../configuration.js";
import { QueryStateAnnotation, ResearcherStateAnnotation } from "./state.js";
import { makeRetriever } from "../../shared/retrieval.js";
import { loadChatModel } from "../../shared/utils.js";

async function generateQueries(
  state: typeof ResearcherStateAnnotation.State,
  config: RunnableConfig,
): Promise<typeof ResearcherStateAnnotation.Update> {
  const Response = z.object({
    queries: z.array(z.string()),
  });

  const configuration = ensureAgentConfiguration(config);
  const model = (
    await loadChatModel(configuration.queryModel)
  ).withStructuredOutput(Response);
  const messages: { role: string; content: string }[] = [
    { role: "system", content: configuration.generateQueriesSystemPrompt },
    { role: "human", content: state.question },
  ];
  const response = await model.invoke(messages);
  return { queries: response.queries };
}

async function retrieveDocuments(
  state: typeof QueryStateAnnotation.State,
  config: RunnableConfig,
): Promise<typeof ResearcherStateAnnotation.Update> {
  const retriever = await makeRetriever(config);
  const response = await retriever.invoke(state.query, config);
  return { documents: response };
}

function retrieveInParallel(
  state: typeof ResearcherStateAnnotation.State,
): Send[] {
  return state.queries.map(
    (query: string) => new Send("retrieveDocuments", { query }),
  );
}

// Define the graph
const builder = new StateGraph({
  stateSchema: ResearcherStateAnnotation,
})
  .addNode("generateQueries", generateQueries)
  .addNode("retrieveDocuments", retrieveDocuments)
  .addEdge(START, "generateQueries")
  .addConditionalEdges("generateQueries", retrieveInParallel, [
    "retrieveDocuments",
  ])
  .addEdge("retrieveDocuments", END);

// Compile into a graph object that you can invoke and deploy.
export const graph = builder
  .compile()
  .withConfig({ runName: "ResearcherGraph" });