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Documentation Index

Fetch the complete documentation index at: https://braintrust.dev/docs/llms.txt

Use this file to discover all available pages before exploring further.

LangGraph is a library for building stateful, multi-actor applications with LLMs. Braintrust traces LangGraph applications through the LangChain callback system, capturing graph execution, node transitions, and model calls.

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Setup

Install LangGraph alongside Braintrust and the LangChain packages you use: 
# pnpm
pnpm add braintrust @braintrust/langchain-js @langchain/core @langchain/langgraph @langchain/openai
# npm
npm install braintrust @braintrust/langchain-js @langchain/core @langchain/langgraph @langchain/openai

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Trace with LangGraph

Calling braintrust.auto_instrument() patches LangChain to register a global callback handler, which LangGraph also uses. See Trace LLM calls for details about auto-instrumentation.

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Python auto-instrumentation

trace-langgraph-auto.py
from typing import TypedDict

import braintrust

braintrust.auto_instrument()
braintrust.init_logger(project="My Project")

from langchain_openai import ChatOpenAI
from langgraph.graph import END, START, StateGraph


class GraphState(TypedDict, total=False):
    message: str


def main():
    model = ChatOpenAI(model="gpt-5-mini")

    def say_hello(state: GraphState):
        response = model.invoke("Say hello")
        return {"message": response.content}

    def say_bye(state: GraphState):
        return {"message": f"{state.get('message', '')} Bye."}

    workflow = (
        StateGraph(state_schema=GraphState)
        .add_node("sayHello", say_hello)
        .add_node("sayBye", say_bye)
        .add_edge(START, "sayHello")
        .add_edge("sayHello", "sayBye")
        .add_edge("sayBye", END)
    )

    graph = workflow.compile()
    result = graph.invoke({})
    print(result)


if __name__ == "__main__":
    main()

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Manual callback setup

If you want explicit control over the LangChain handler, configure it directly:
trace-langgraph.ts
import {
  BraintrustCallbackHandler,
  setGlobalHandler,
} from "@braintrust/langchain-js";
import { END, START, StateGraph, type StateGraphArgs } from "@langchain/langgraph";
import { ChatOpenAI } from "@langchain/openai";
import { initLogger } from "braintrust";

const logger = initLogger({
  projectName: "My Project",
  apiKey: process.env.BRAINTRUST_API_KEY,
});

const handler = new BraintrustCallbackHandler({ logger });
setGlobalHandler(handler);

type HelloWorldGraphState = Record<string, unknown>;

const graphStateChannels: StateGraphArgs<HelloWorldGraphState>["channels"] = {};

const model = new ChatOpenAI({
  model: "gpt-5-mini",
});

async function sayHello(_state: HelloWorldGraphState) {
  const res = await model.invoke("Say hello");
  return { message: res.content };
}

function sayBye(_state: HelloWorldGraphState) {
  console.log("From the 'sayBye' node: Bye world!");
  return {};
}

async function main() {
  const graphBuilder = new StateGraph({ channels: graphStateChannels })
    .addNode("sayHello", sayHello)
    .addNode("sayBye", sayBye)
    .addEdge(START, "sayHello")
    .addEdge("sayHello", "sayBye")
    .addEdge("sayBye", END);

  const helloWorldGraph = graphBuilder.compile();

  await helloWorldGraph.invoke({});
}

main();
LangGraph trace visualization in Braintrust showing the execution flow of nodes and their relationships

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Resources