# Quick Start

This guide adds a chat that renders tokens while the model writes them. You add a server route, an API key, and a UI.

TanStack AI gives you each piece. `chat()` streams from your server route. A hook for your framework renders the tokens. This takes about 5 minutes.

Not on the web?

- **React Native or Expo:** go to [Quick Start: React Native](./quick-start-react-native).
- **No UI, only a backend:** go to [Quick Start: Server Only](./quick-start-server).

## 1. Install

```sh
npm i @tanstack/ai @tanstack/ai-vue @tanstack/ai-openai
```

Pick your framework at the top of the page. The install command and the UI code follow your pick.

> [!TIP]
> If you do not want a key for each provider, use [OpenRouter](../adapters/openrouter). It gives you 300+ models with one API key.

## 2. Stream from the server

Put your API key in the server environment, for example in `.env`:

```bash
OPENAI_API_KEY=your-openai-api-key
```

Create a route at `/api/chat`. In Next.js, that is `app/api/chat/route.ts`. Call `chat()`, then return the stream with `toServerSentEventsResponse`:

```typescript
import {
  chat,
  chatParamsFromRequest,
  toServerSentEventsResponse,
} from "@tanstack/ai";
import { openaiText } from "@tanstack/ai-openai";

export async function POST(request: Request) {
  const { messages, threadId, runId } = await chatParamsFromRequest(request);

  const stream = chat({
    adapter: openaiText("gpt-6.1-sol"),
    messages,
    threadId,
    runId,
  });

  return toServerSentEventsResponse(stream);
}
```

The adapter reads `OPENAI_API_KEY` at runtime. Do not send this key to the browser.

## 3. Render the chat

Call `useChat` from `@tanstack/ai-vue`. If you are in `<script setup>`, read refs with `.value`. The template unwraps them.

```vue
<script setup lang="ts">
import { ref } from 'vue'
import { useChat, fetchServerSentEvents } from '@tanstack/ai-vue'

const input = ref('')

const { messages, sendMessage, isLoading, stop } = useChat({
  connection: fetchServerSentEvents('/api/chat'),
  threadId: "support-chat",
})

function handleSubmit() {
  if (input.value.trim() && !isLoading.value) {
    sendMessage(input.value)
    input.value = ''
  }
}
</script>

<template>
  <div>
    <div v-for="message in messages" :key="message.id">
      <template v-for="(part, index) in message.parts" :key="index">
        <p v-if="part.type === 'text'">{{ part.content }}</p>
      </template>
    </div>
    <form @submit.prevent="handleSubmit">
      <input v-model="input" :disabled="isLoading" />
      <button v-if="isLoading" type="button" @click="stop">Stop</button>
      <button v-else type="submit" :disabled="!input.trim()">Send</button>
    </form>
  </div>
</template>
```

The composable stops in-flight requests when the component unmounts.

See the [Vue API](../api/ai-vue).

No framework? Use `ChatClient` from `@tanstack/ai-client`. See the [client API](../api/ai-client).

## 4. Try it

Start your app and send a message. The answer appears word by word while the model writes it. Click **Stop** to cancel a run.

You now have a streaming chat.

## How it works

1. `sendMessage` posts the messages to `/api/chat`.
2. `chatParamsFromRequest` reads the messages and the run ids from the request.
3. `chat()` calls the model through the adapter and returns a stream of events.
4. `toServerSentEventsResponse` sends those events back as Server-Sent Events.
5. `fetchServerSentEvents` reads the events, and the hook adds each chunk to `messages`.

Each message has `parts`. This page renders only the `text` parts. Tool calls and other content arrive as other part types.

## Next

Add one feature at a time:

- [Tools](../tools/tools): let the model call your functions.
- [Streaming](../chat/streaming): cancel, callbacks, and transports.
- [Adapters](../adapters/openai): switch to another provider.

Or build a full app in a tutorial, such as [Basic Chat](../tutorials/basic-chat) or [Generate Image](../tutorials/generate-image).

## Advanced

### Hosts

The server route returns a Web `Response`. It works with any host that can return one:

- TanStack Start
- Next.js
- SvelteKit
- Hono
- A Remix controller action

If your server uses Node streams (Express), see [Quick Start: Server Only](./quick-start-server).

### Bad request bodies

If the request body is not valid, `chatParamsFromRequest` throws a `Response` with status 400.

- TanStack Start, SolidStart, Remix, and React Router 7 return a thrown `Response` to the client for you.
- Next.js Route Handlers, SvelteKit, Hono, and raw Node do not. Wrap the call in `try`/`catch` and return the caught `Response`.

### Keys in the browser

If you do not want a key on the server, users can paste their own provider key. See [Bring Your Own Key](../advanced/byok).