# Integrate Mastra in your SvelteKit project

In this guide, you'll build a tool-calling AI agent using Mastra, then connect it to SvelteKit by importing and calling the agent directly from your routes.

You'll use [AI SDK UI](https://ai-sdk.dev/docs/ai-sdk-ui/overview) to create a beautiful, interactive chat experience.

## Before you begin

- You'll need an API key from a supported [model provider](https://mastra.ai/models). If you don't have a preference, use [OpenAI](https://mastra.ai/models/providers/openai).
- Install Node.js `v22.13.0` or later

## Create a new SvelteKit app (optional)

If you already have a SvelteKit app using Tailwind, skip to the next step.

Run the following command to [create a new SvelteKit app](https://svelte.dev/docs/kit/creating-a-project):

**npm**:

```bash
npx sv create mastra-svelte --template minimal --types ts --add tailwindcss="plugins:forms" --install npm
```

**pnpm**:

```bash
pnpm dlx sv create mastra-svelte --template minimal --types ts --add tailwindcss="plugins:forms" --install npm
```

**Yarn**:

```bash
yarn dlx sv create mastra-svelte --template minimal --types ts --add tailwindcss="plugins:forms" --install npm
```

**Bun**:

```bash
bun x sv create mastra-svelte --template minimal --types ts --add tailwindcss="plugins:forms" --install npm
```

This creates a project called `mastra-svelte`, but you can replace it with any name you want. Tailwind was added for styling purposes later on.

## Initialize Mastra

Navigate to your SvelteKit project:

```bash
cd mastra-svelte
```

Run [`mastra init`](https://mastra.ai/reference/cli/mastra). When prompted, choose a provider (e.g. OpenAI) and enter your key:

**npm**:

```bash
npx mastra@latest init
```

**pnpm**:

```bash
pnpm dlx mastra@latest init
```

**Yarn**:

```bash
yarn dlx mastra@latest init
```

**Bun**:

```bash
bun x mastra@latest init
```

This creates a `src/mastra` folder with an example weather agent and the following files:

- `index.ts` - Mastra config, including memory
- `tools/weather-tool.ts` - a tool to fetch weather for a given location
- `agents/weather-agent.ts`- a weather agent with a prompt that uses the tool

You'll call `weather-agent.ts` from your SvelteKit routes in the next steps.

## Install AI SDK UI

Install AI SDK UI along with the Mastra adapter:

**npm**:

```bash
npm install @mastra/ai-sdk@latest @ai-sdk/svelte ai
```

**pnpm**:

```bash
pnpm add @mastra/ai-sdk@latest @ai-sdk/svelte ai
```

**Yarn**:

```bash
yarn add @mastra/ai-sdk@latest @ai-sdk/svelte ai
```

**Bun**:

```bash
bun add @mastra/ai-sdk@latest @ai-sdk/svelte ai
```

## Create a chat route

Create `src/routes/api/chat/+server.ts`:

```ts
import type { RequestHandler } from "./$types";
import { handleChatStream } from "@mastra/ai-sdk";
import { toAISdkV5Messages } from "@mastra/ai-sdk/ui";
import { createUIMessageStreamResponse } from "ai";
import { mastra } from "../../../mastra";

const THREAD_ID = "example-user-id";
const RESOURCE_ID = "weather-chat";

export const POST: RequestHandler = async ({ request }) => {
  const params = await request.json();
  const stream = await handleChatStream({
    mastra,
    agentId: "weather-agent",
    params: {
      ...params,
      memory: {
        ...params.memory,
        thread: THREAD_ID,
        resource: RESOURCE_ID,
      },
    },
  });

  return createUIMessageStreamResponse({ stream });
};

export const GET: RequestHandler = async () => {
  const memory = await mastra.getAgentById("weather-agent").getMemory();
  let response = null;

  try {
    response = await memory?.recall({
      threadId: THREAD_ID,
      resourceId: RESOURCE_ID,
    });
  } catch {
    console.log("No previous messages found.");
  }

  const uiMessages = toAISdkV5Messages(response?.messages || []);

  return Response.json(uiMessages);
};
```

The `POST` route accepts a prompt and streams the agent's response back in AI SDK format, while the `GET` route fetches message history from memory so the UI can be hydrated when the client reloads.

In order for the `GET` handler to be called, you need to create a `src/routes/+page.ts` file. Its `load()` function runs alongside `+page.svelte`.

```ts
import type { UIDataTypes, UIMessage, UITools } from "ai";
import type { PageLoad } from "./$types";

export const load: PageLoad = async ({ fetch }) => {
  const response = await fetch("/api/chat");
  const initialMessages = (await response.json()) as UIMessage<
    unknown,
    UIDataTypes,
    UITools
  >[];
  return { initialMessages };
};
```

## Add the chat UI

Replace `src/routes/+page.svelte` with the following.

```html
<script lang="ts">
  import { Chat } from '@ai-sdk/svelte';
  import { DefaultChatTransport, type ToolUIPart } from 'ai';

  let input = $state('');
  const { data } = $props();
  let messages = $derived(data.initialMessages)

  const chat = new Chat({
    transport: new DefaultChatTransport({
      api: '/api/chat'
    }),
    get messages() {
      return messages;
    }
  });

  function handleSubmit(event: SubmitEvent) {
    event.preventDefault();
    chat.sendMessage({ text: input });
    input = '';
  }

  const STATE_TO_LABEL_MAP: Record<ToolUIPart["state"], string> = {
    "input-streaming": "Pending",
    "input-available": "Running",
    // @ts-expect-error - Only available in AI SDK v6
    "approval-requested": "Awaiting Approval",
    "approval-responded": "Responded",
    "output-available": "Completed",
    "output-error": "Error",
    "output-denied": "Denied",
  };
</script>

<main class="max-w-3xl mx-auto p-6 size-full h-screen">
  <div class="flex flex-col h-full">
    <div class="flex-1 min-h-0 overflow-y-auto" data-name="conversation">
      <div data-name="conversation-content" class="flex flex-col gap-8">
        {#each chat.messages as message, messageIndex (messageIndex)}
          <div>
            {#each message.parts as part, partIndex (partIndex)}
              {#if part.type === 'text'}
                <div data-name="message" class={[message.role === 'user' && 'ml-auto justify-end', 'group flex w-full max-w-[95%] flex-col gap-2', message.role === 'user' ? 'is-user' : 'is-assistant']}>
                  <div data-name="message-content" class={["is-user:dark flex w-fit max-w-full min-w-0 flex-col gap-2 overflow-hidden text-sm",
      "group-[.is-user]:ml-auto group-[.is-user]:rounded-lg group-[.is-user]:bg-blue-100 group-[.is-user]:px-4 group-[.is-user]:py-3 group-[.is-user]:text-foreground",
      "group-[.is-assistant]:text-foreground"]}>
                    <div data-name="message-response" class="size-full [&>*:first-child]:mt-0 [&>*:last-child]:mb-0">
                      {part.text}
                    </div>
                  </div>
                </div>
              {:else if part.type.startsWith('tool-')}
                <div data-name="tool" class="not-prose mb-6 w-full rounded-lg border border-gray-300 shadow">
                  <details data-name="tool-header" class="w-full p-3 hover:cursor-pointer">
                    <summary class="font-medium text-sm">{(part as ToolUIPart).type.split("-").slice(1).join("-")} - {STATE_TO_LABEL_MAP[(part as ToolUIPart).state ?? 'output-available']}</summary>
                    <div data-name="tool-content" class="">
                      <div data-name="tool-input" class="space-y-2 overflow-hidden py-4">
                        <div class="font-medium text-muted-foreground text-xs uppercase tracking-wide">Parameters</div>
                        <pre class="w-full overflow-x-auto rounded-md border border-gray-300 bg-gray-50 p-3 text-sm"><code>{JSON.stringify((part as ToolUIPart).input, null, 2)}</code></pre>
                      </div>
                      <div data-name="tool-output" class="space-y-2 overflow-hidden py-4">
                        <div class="font-medium text-muted-foreground text-xs uppercase tracking-wide">{(part as ToolUIPart).errorText ? 'Error' : 'Result'}</div>
                        <pre class="w-full overflow-x-auto rounded-md border border-gray-300 bg-gray-50 p-3 text-sm"><code>{JSON.stringify((part as ToolUIPart).output, null, 2)}</code></pre>
                        {#if (part as ToolUIPart).errorText}
                          <div data-name="tool-error" class="text-red-600">
                            {(part as ToolUIPart).errorText}
                          </div>
                        {/if}
                      </div>
                    </div>
                  </details>
                </div>
              {/if}
            {/each}
          </div>
        {/each}
      </div>
    </div>
    <form class="w-full grid grid-cols-[1fr_auto] gap-6 shrink-0 pt-4" onsubmit={handleSubmit} data-name="prompt-input">
      <input name="chat-input" class="rounded-lg border border-gray-300 shadow h-10" placeholder="City name" bind:value={input} />
      <button class="bg-blue-600 text-white shadow-lg border border-blue-400 px-4 whitespace-nowrap rounded-lg text-sm font-medium transition-all disabled:pointer-events-none disabled:opacity-50 shrink-0 outline-none focus-visible:border-ring focus-visible:ring-ring/50 focus-visible:ring-[3px]" type="submit">Send</button>
    </form>
  </div>
</main>
```

This page connects [`Chat`](https://ai-sdk.dev/docs/reference/ai-sdk-ui/use-chat) to the `api/chat` endpoint, sending prompts there and streaming the response back in chunks.

It renders the response text using custom message and tool components.

## Test your agent

1. Run your SvelteKit app with `npm run dev`
2. Open the chat at <http://localhost:5173>
3. Try asking about the weather. If your API key is set up correctly, you'll get a response

## Next steps

Congratulations on building your Mastra agent with SvelteKit! 🎉

From here, you can extend the project with your own tools and logic:

- Learn more about [agents](https://mastra.ai/docs/agents/overview)
- Give your agent its own [tools](https://mastra.ai/docs/agents/using-tools)
- Add human-like [memory](https://mastra.ai/docs/agents/agent-memory) to your agent

When you're ready, read more about how Mastra integrates with AI SDK UI and SvelteKit, and how to deploy your agent anywhere:

- Integrate Mastra with [AI SDK UI](https://mastra.ai/guides/build-your-ui/ai-sdk-ui)
- Deploy your agent [anywhere](https://mastra.ai/docs/deployment/overview)
- Try the [unofficial Svelte AI Elements](https://svelte-ai-elements.vercel.app/)