LangGraph Integration

CopilotKit supports LangGraph in three configurations: Python with self-hosted FastAPI, Python with LangGraph Platform, and JavaScript/TypeScript. All use the AG-UI protocol.

Python (Self-Hosted FastAPI)

This is the langgraph-fastapi example pattern. You run the LangGraph agent as a standalone FastAPI server and connect via LangGraphHttpAgent.

Prerequisites

Python 3.10+
Node.js 18+
OpenAI API key
poetry or uv for Python dependency management

Python Dependencies

toml

# pyproject.toml
[project]
dependencies = [
    "copilotkit==0.1.74",
    "langchain==1.0.1",
    "langchain-openai==1.0.1",
    "langgraph==1.0.1",
    "fastapi==0.115.12",
    "uvicorn>=0.38.0",
    "python-dotenv>=1.0.0",
    "ag-ui-langgraph==0.0.22",
    "pydantic>=2.0.0,<3.0.0",
]

Agent Definition (agent/src/agent.py)

The agent extends CopilotKitState for shared state and uses the standard ReAct pattern:

python

from copilotkit import CopilotKitState
from langchain.tools import tool
from langchain_core.messages import SystemMessage
from langchain_core.runnables import RunnableConfig
from langchain_openai import ChatOpenAI
from langgraph.checkpoint.memory import MemorySaver
from langgraph.graph import StateGraph
from langgraph.prebuilt import ToolNode
from langgraph.types import Command
from typing_extensions import Literal
from src.util import should_route_to_tool_node

class AgentState(CopilotKitState):
    proverbs: list[str]

@tool
def get_weather(location: str):
    """Get the weather for a given location."""
    return f"The weather for {location} is 70 degrees."

tools = [get_weather]

async def chat_node(
    state: AgentState, config: RunnableConfig
) -> Command[Literal["tool_node", "__end__"]]:
    model = ChatOpenAI(model="gpt-4o")
    # Bind both frontend (CopilotKit) actions and backend tools
    fe_tools = state.get("copilotkit", {}).get("actions", [])
    model_with_tools = model.bind_tools([*fe_tools, *tools])

    system_message = SystemMessage(
        content=f"You are a helpful assistant. The current proverbs are {state.get('proverbs', [])}."
    )
    response = await model_with_tools.ainvoke(
        [system_message, *state["messages"]], config,
    )

    tool_calls = response.tool_calls
    if tool_calls and should_route_to_tool_node(tool_calls, fe_tools):
        return Command(goto="tool_node", update={"messages": response})
    return Command(goto="__end__", update={"messages": response})

workflow = StateGraph(AgentState)
workflow.add_node("chat_node", chat_node)
workflow.add_node("tool_node", ToolNode(tools=tools))
workflow.add_edge("tool_node", "chat_node")
workflow.set_entry_point("chat_node")

graph = workflow.compile(checkpointer=MemorySaver())

Key pattern: CopilotKitState provides the copilotkit field containing actions (frontend tools). You must bind both frontend actions and backend tools to the model, then route frontend tool calls back to CopilotKit (not the ToolNode).

FastAPI Server (agent/main.py)

python

from fastapi import FastAPI
from copilotkit import LangGraphAGUIAgent
from ag_ui_langgraph import add_langgraph_fastapi_endpoint
from src.agent import graph

app = FastAPI()

add_langgraph_fastapi_endpoint(
    app=app,
    agent=LangGraphAGUIAgent(
        name="sample_agent",
        description="An example agent.",
        graph=graph,
    ),
    path="/",
)

Next.js Route (src/app/api/copilotkit/[[...slug]]/route.ts)

typescript

import {
  CopilotRuntime,
  createCopilotHonoHandler,
  InMemoryAgentRunner,
} from "@copilotkit/runtime/v2";
import { LangGraphHttpAgent } from "@copilotkit/runtime/langgraph";
import { handle } from "hono/vercel";

const runtime = new CopilotRuntime({
  agents: {
    default: new LangGraphHttpAgent({
      url: `${process.env.AGENT_URL || "http://localhost:8123"}/`,
    }),
  },
  runner: new InMemoryAgentRunner(),
});

const app = createCopilotHonoHandler({
  runtime,
  basePath: "/api/copilotkit",
});

export const GET = handle(app);
export const POST = handle(app);
export const PATCH = handle(app);
export const DELETE = handle(app);

Use LangGraphHttpAgent (from @copilotkit/runtime/langgraph) for self-hosted agents -- the FastAPI server runs under ag-ui-langgraph, which speaks AG-UI directly. The default port is 8123 (note the trailing slash on the URL).

Python (LangGraph Platform / Monorepo)

This is the langgraph-python example pattern. Uses LangGraphAgent which connects to a LangGraph deployment (local or cloud).

Next.js Route (src/app/api/copilotkit/[[...slug]]/route.ts)

typescript

import {
  CopilotRuntime,
  createCopilotHonoHandler,
  InMemoryAgentRunner,
} from "@copilotkit/runtime/v2";
import { LangGraphAgent } from "@copilotkit/runtime/langgraph";
import { handle } from "hono/vercel";

const defaultAgent = new LangGraphAgent({
  deploymentUrl:
    process.env.LANGGRAPH_DEPLOYMENT_URL || "http://localhost:8123",
  graphId: "sample_agent",
  langsmithApiKey: process.env.LANGSMITH_API_KEY || "",
});

const runtime = new CopilotRuntime({
  agents: { default: defaultAgent },
  runner: new InMemoryAgentRunner(),
});

const app = createCopilotHonoHandler({
  runtime,
  basePath: "/api/copilotkit",
});

export const GET = handle(app);
export const POST = handle(app);
export const PATCH = handle(app);
export const DELETE = handle(app);

Key difference from self-hosted: LangGraphAgent uses deploymentUrl and graphId (and optionally langsmithApiKey) to target the LangGraph Platform / langgraph-cli dev surface, while LangGraphHttpAgent uses a plain url for a self-hosted AG-UI server.

JavaScript / TypeScript

This is the langgraph-js example pattern. The agent is a TypeScript LangGraph graph running in a separate Node.js process.

Agent Definition (apps/agent/src/agent.ts)

typescript

import { z } from "zod";
import { tool } from "@langchain/core/tools";
import { ToolNode } from "@langchain/langgraph/prebuilt";
import { AIMessage, SystemMessage } from "@langchain/core/messages";
import { MemorySaver, START, StateGraph } from "@langchain/langgraph";
import { ChatOpenAI } from "@langchain/openai";
import {
  convertActionsToDynamicStructuredTools,
  CopilotKitStateAnnotation,
} from "@copilotkit/sdk-js/langgraph";
import { Annotation } from "@langchain/langgraph";

const AgentStateAnnotation = Annotation.Root({
  ...CopilotKitStateAnnotation.spec,
  proverbs: Annotation<string[]>,
});

export type AgentState = typeof AgentStateAnnotation.State;

const getWeather = tool(
  (args) => `The weather for ${args.location} is 70 degrees.`,
  {
    name: "getWeather",
    description: "Get the weather for a given location.",
    schema: z.object({ location: z.string() }),
  },
);

const tools = [getWeather];

async function chat_node(state: AgentState, config) {
  const model = new ChatOpenAI({ temperature: 0, model: "gpt-4o" });
  const modelWithTools = model.bindTools!([
    ...convertActionsToDynamicStructuredTools(state.copilotkit?.actions ?? []),
    ...tools,
  ]);

  const systemMessage = new SystemMessage({
    content: `You are a helpful assistant. The current proverbs are ${JSON.stringify(state.proverbs)}.`,
  });
  const response = await modelWithTools.invoke(
    [systemMessage, ...state.messages],
    config,
  );
  return { messages: response };
}

function shouldContinue({ messages, copilotkit }: AgentState) {
  const lastMessage = messages[messages.length - 1] as AIMessage;
  if (lastMessage.tool_calls?.length) {
    const actions = copilotkit?.actions;
    const toolCallName = lastMessage.tool_calls![0].name;
    if (!actions || actions.every((action) => action.name !== toolCallName)) {
      return "tool_node";
    }
  }
  return "__end__";
}

const workflow = new StateGraph(AgentStateAnnotation)
  .addNode("chat_node", chat_node)
  .addNode("tool_node", new ToolNode(tools))
  .addEdge(START, "chat_node")
  .addEdge("tool_node", "chat_node")
  .addConditionalEdges("chat_node", shouldContinue);

export const graph = workflow.compile({ checkpointer: new MemorySaver() });

Key JS-specific patterns:

Use CopilotKitStateAnnotation from @copilotkit/sdk-js/langgraph to include CopilotKit state
Use convertActionsToDynamicStructuredTools() to convert frontend actions to LangChain tools
Check copilotkit.actions to determine whether a tool call should route to tool_node (backend) or __end__ (frontend)

Serving the JS graph

LangGraphAgent with deploymentUrl/graphId targets the LangGraph server surface, not the bare compiled graph export. Serve the graph with the LangGraph JS CLI (@langchain/langgraph-cli) so that surface exists. Add a langgraph.json next to the agent:

json

{
  "node_version": "20",
  "dependencies": ["."],
  "graphs": {
    "sample_agent": "./src/agent.ts:graph"
  },
  "env": "../.env"
}

Run it with langgraphjs dev --port 8123 (the agent app's dev script). The graphId you pass to LangGraphAgent must match a key under graphs (here "sample_agent"), and deploymentUrl points at the CLI server (http://localhost:8123).

Next.js Route

The catch-all src/app/api/copilotkit/[[...slug]]/route.ts uses LangGraphAgent (from @copilotkit/runtime/langgraph) with deploymentUrl (the langgraphjs dev URL, e.g. http://localhost:8123) and graphId ("sample_agent"), mounted via createCopilotHonoHandler.

Monorepo Structure (JS)

The JS variant uses a Turborepo monorepo:

apps/
  web/          # Next.js frontend
  agent/        # LangGraph agent, served via `langgraphjs dev` (langgraph.json)
pnpm-workspace.yaml
turbo.json

Run pnpm dev to start both apps via Turborepo (the agent app runs langgraphjs dev --port 8123).