How to implement Generative User Interfaces with LangGraph¶
Prerequisites
Generative user interfaces (Generative UI) allows agents to go beyond text and generate rich user interfaces. This enables creating more interactive and context-aware applications where the UI adapts based on the conversation flow and AI responses.
LangGraph Platform supports colocating your React components with your graph code. This allows you to focus on building specific UI components for your graph while easily plugging into existing chat interfaces such as Agent Chat and loading the code only when actually needed.
Tutorial¶
1. Define and configure UI components¶
First, create your first UI component. For each component you need to provide an unique identifier that will be used to reference the component in your graph code.
const WeatherComponent = (props: { city: string }) => {
return <div>Weather for {props.city}</div>;
};
export default {
weather: WeatherComponent,
};
Next, define your UI components in your langgraph.json configuration:
{
"node_version": "20",
"graphs": {
"agent": "./src/agent/index.ts:graph"
},
"ui": {
"agent": "./src/agent/ui.tsx"
}
}
The ui section points to the UI components that will be used by graphs. By default, we recommend using the same key as the graph name, but you can split out the components however you like, see Customise the namespace of UI components for more details.
LangGraph Platform will automatically bundle your UI components code and styles and serve them as external assets that can be loaded by the LoadExternalComponent component. Some dependencies such as react and react-dom will be automatically excluded from the bundle.
CSS and Tailwind 4.x is also supported out of the box, so you can freely use Tailwind classes as well as shadcn/ui in your UI components.
2. Send the UI components in your graph¶
import uuid
from typing import Annotated, Sequence, TypedDict
from langchain_core.messages import AIMessage, BaseMessage
from langchain_openai import ChatOpenAI
from langgraph.graph import StateGraph
from langgraph.graph.message import add_messages
from langgraph.graph.ui import AnyUIMessage, ui_message_reducer, push_ui_message
class AgentState(TypedDict): # noqa: D101
messages: Annotated[Sequence[BaseMessage], add_messages]
ui: Annotated[Sequence[AnyUIMessage], ui_message_reducer]
async def weather(state: AgentState):
class WeatherOutput(TypedDict):
city: str
weather: WeatherOutput = (
await ChatOpenAI(model="gpt-4o-mini")
.with_structured_output(WeatherOutput)
.with_config({"tags": ["nostream"]})
.ainvoke(state["messages"])
)
message = AIMessage(
id=str(uuid.uuid4()),
content=f"Here's the weather for {weather['city']}",
)
# Emit UI elements associated with the message
push_ui_message("weather", weather, message=message)
return {"messages": [message]}
workflow = StateGraph(AgentState)
workflow.add_node(weather)
workflow.add_edge("__start__", "weather")
graph = workflow.compile()
Use the typedUi utility to emit UI elements from your agent nodes:
import {
typedUi,
uiMessageReducer,
} from "@langchain/langgraph-sdk/react-ui/server";
import { ChatOpenAI } from "@langchain/openai";
import { v4 as uuidv4 } from "uuid";
import { z } from "zod";
import type ComponentMap from "./ui.js";
import {
Annotation,
MessagesAnnotation,
StateGraph,
type LangGraphRunnableConfig,
} from "@langchain/langgraph";
const AgentState = Annotation.Root({
...MessagesAnnotation.spec,
ui: Annotation({ reducer: uiMessageReducer, default: () => [] }),
});
export const graph = new StateGraph(AgentState)
.addNode("weather", async (state, config) => {
// Provide the type of the component map to ensure
// type safety of `ui.push()` calls as well as
// pushing the messages to the `ui` and sending a custom event as well.
const ui = typedUi<typeof ComponentMap>(config);
const weather = await new ChatOpenAI({ model: "gpt-4o-mini" })
.withStructuredOutput(z.object({ city: z.string() }))
.withConfig({ tags: ["nostream"] })
.invoke(state.messages);
const response = {
id: uuidv4(),
type: "ai",
content: `Here's the weather for ${weather.city}`,
};
// Emit UI elements associated with the AI message
ui.push({ name: "weather", props: weather }, { message: response });
return { messages: [response] };
})
.addEdge("__start__", "weather")
.compile();
3. Handle UI elements in your React application¶
On the client side, you can use useStream() and LoadExternalComponent to display the UI elements.
"use client";
import { useStream } from "@langchain/langgraph-sdk/react";
import { LoadExternalComponent } from "@langchain/langgraph-sdk/react-ui";
export default function Page() {
const { thread, values } = useStream({
apiUrl: "http://localhost:2024",
assistantId: "agent",
});
return (
<div>
{thread.messages.map((message) => (
<div key={message.id}>
{message.content}
{values.ui
?.filter((ui) => ui.metadata?.message_id === message.id)
.map((ui) => (
<LoadExternalComponent key={ui.id} stream={thread} message={ui} />
))}
</div>
))}
</div>
);
}
Behind the scenes, LoadExternalComponent will fetch the JS and CSS for the UI components from LangGraph Platform and render them in a shadow DOM, thus ensuring style isolation from the rest of your application.
How-to guides¶
Show loading UI when components are loading¶
You can provide a fallback UI to be rendered when the components are loading.
Provide custom components on the client side¶
If you already have the components loaded in your client application, you can provide a map of such components to be rendered directly without fetching the UI code from LangGraph Platform.
const clientComponents = {
weather: WeatherComponent,
};
<LoadExternalComponent
stream={thread}
message={ui}
components={clientComponents}
/>;
Customise the namespace of UI components.¶
By default LoadExternalComponent will use the assistantId from useStream() hook to fetch the code for UI components. You can customise this by providing a namespace prop to the LoadExternalComponent component.
Access and interact with the thread state from the UI component¶
You can access the thread state inside the UI component by using the useStreamContext hook.
import { useStreamContext } from "@langchain/langgraph-sdk/react-ui";
const WeatherComponent = (props: { city: string }) => {
const { thread, submit } = useStreamContext();
return (
<>
<div>Weather for {props.city}</div>
<button
onClick={() => {
const newMessage = {
type: "human",
content: `What's the weather in ${props.city}?`,
};
submit({ messages: [newMessage] });
}}
>
Retry
</button>
</>
);
};
Pass additional context to the client components¶
You can pass additional context to the client components by providing a meta prop to the LoadExternalComponent component.
Then, you can access the meta prop in the UI component by using the useStreamContext hook.
import { useStreamContext } from "@langchain/langgraph-sdk/react-ui";
const WeatherComponent = (props: { city: string }) => {
const { meta } = useStreamContext<
{ city: string },
{ MetaType: { userId?: string } }
>();
return (
<div>
Weather for {props.city} (user: {meta?.userId})
</div>
);
};
Streaming UI updates before the node execution is finished¶
You can stream UI updates before the node execution is finished by using the onCustomEvent callback of the useStream() hook.
import { uiMessageReducer } from "@langchain/langgraph-sdk/react-ui";
const { thread, submit } = useStream({
apiUrl: "http://localhost:2024",
assistantId: "agent",
onCustomEvent: (event, options) => {
options.mutate((prev) => {
const ui = uiMessageReducer(prev.ui ?? [], event);
return { ...prev, ui };
});
},
});
Remove UI messages from state¶
Similar to how messages can be removed from the state by appending a RemoveMessage you can remove an UI message from the state by calling remove_ui_message / ui.delete with the ID of the UI message.