workflow/docs/getting-started/sveltekit.mdx

Workflow SDK - Build durable, resilient, and observable workflows

---
title: SvelteKit
description: Set up your first durable workflow in a SvelteKit app.
type: guide
summary: Set up Workflow SDK in a SvelteKit app.
prerequisites:
  - /docs/getting-started
related:
  - /docs/foundations/workflows-and-steps
---

<CopyPrompt
  text="In this SvelteKit app, run `npm i workflow`. In `vite.config.ts`, import `workflowPlugin` from `workflow/sveltekit` and add it to `plugins` with `sveltekit()`. Add the TypeScript plugin `{ &quot;name&quot;: &quot;workflow&quot; }` to `tsconfig.json` if TypeScript is used. Create `workflows/user-signup.ts` exporting `handleUserSignup(email)` with `&quot;use workflow&quot;`, `sleep` from `workflow`, and `&quot;use step&quot;` helpers that create a user and send emails. Add `src/routes/api/signup/+server.ts` with a POST `RequestHandler` that reads `{ email }`, calls `start(handleUserSignup, [email])` from `workflow/api`, and returns `json({ message: &quot;User signup workflow started&quot; })`. Run `npm run dev`, call `curl -X POST --json '{&quot;email&quot;:&quot;hello@example.com&quot;}' http://localhost:5173/api/signup`, then inspect with `npx workflow web` or `npx workflow inspect runs`."
/>

<Steps>

<Step>
## Create your SvelteKit project

Create a minimal SvelteKit project in a new directory named `my-workflow-app`:

```bash
npx sv create my-workflow-app --template=minimal --types=ts --no-add-ons
```

Enter the newly made directory:

```bash
cd my-workflow-app
```

### Install `workflow`

```package-install
npm i workflow
```

### Configure Vite

Add `workflowPlugin()` to your Vite config. This enables usage of the `"use workflow"` and `"use step"` directives.

```typescript title="vite.config.ts" lineNumbers
import { sveltekit } from "@sveltejs/kit/vite";
import { defineConfig } from "vite";
import { workflowPlugin } from "workflow/sveltekit"; // [!code highlight]

export default defineConfig({
  plugins: [sveltekit(), workflowPlugin()], // [!code highlight]
});
```

`workflowPlugin()` accepts an options object:

| Option | Type | Default | Description |
| --- | --- | --- | --- |
| `sourcemap` | `boolean \| 'inline' \| 'linked' \| 'external' \| 'both'` | `'inline'` (dev) / `false` (prod) | Controls source maps on generated workflow bundles. Accepts the same values as esbuild's `sourcemap` option. Defaults to `'inline'` in development and `false` in production (smaller function bundles, which helps stay under the Vercel 250 MB function size limit). Set it explicitly, or use the `WORKFLOW_SOURCEMAP` environment variable, to override in either environment. |

<Details>
<Summary className="[&_h3]:my-0">

### Set up IntelliSense for TypeScript (optional)

</Summary>

To enable helpful hints in your IDE, set up the workflow plugin in `tsconfig.json`:

```json title="tsconfig.json" lineNumbers
{
  "compilerOptions": {
    // ... rest of your TypeScript config
    "plugins": [
      {
        "name": "workflow" // [!code highlight]
      }
    ]
  }
}
```

</Details>

</Step>

<Step>

## Create your first workflow

Create a new file for our first workflow:

```typescript title="workflows/user-signup.ts" lineNumbers
import { sleep } from "workflow";

export async function handleUserSignup(email: string) {
  "use workflow"; // [!code highlight]

  const user = await createUser(email);
  await sendWelcomeEmail(user);

  await sleep("5s"); // Pause for 5s - doesn't consume any resources
  await sendOnboardingEmail(user);

  console.log("Workflow is complete! Run 'npx workflow web' to inspect your run")

  return { userId: user.id, status: "onboarded" };
}

```

We'll fill in those functions next, but first review this code:

* We define a **workflow** function with the directive `"use workflow"`. Think of the workflow function as the _orchestrator_ of individual **steps**.
* The Workflow SDK's `sleep` function allows us to suspend execution of the workflow without using up any resources. A sleep can be a few seconds, hours, days, or even months long.

## Create your workflow steps

Define the missing functions.

```typescript title="workflows/user-signup.ts" lineNumbers
import { FatalError } from "workflow"

// Our workflow function defined earlier

async function createUser(email: string) {
  "use step"; // [!code highlight]

  console.log(`Creating user with email: ${email}`);

  // Full Node.js access - database calls, APIs, etc.
  return { id: crypto.randomUUID(), email };
}

async function sendWelcomeEmail(user: { id: string; email: string; }) {
  "use step"; // [!code highlight]

  console.log(`Sending welcome email to user: ${user.id}`);

  if (Math.random() < 0.3) {
  // By default, steps will be retried for unhandled errors
   throw new Error("Retryable!");
  }
}

async function sendOnboardingEmail(user: { id: string; email: string}) {
  "use step"; // [!code highlight]

  if (!user.email.includes("@")) {
    // To skip retrying, throw a FatalError instead
    throw new FatalError("Invalid Email");
  }

  console.log(`Sending onboarding email to user: ${user.id}`);
}
```

Taking a look at this code:

* Business logic lives inside **steps**. When a workflow invokes a step, the workflow suspends while the step runs with full Node.js access. The combined handler may execute it inline; queued retries and continuations return through the same flow route.
* If a step throws an error, like in `sendWelcomeEmail`, the step will automatically be retried until it succeeds (or hits the step's max retry count).
* Steps can throw a `FatalError` if an error is intentional and should not be retried.

<Callout>
We'll dive deeper into workflows, steps, and other ways to suspend or handle events in [Foundations](/docs/foundations).
</Callout>

</Step>

<Step>

## Create your route handler

To invoke your new workflow, we'll have to add your workflow to a `POST` API route handler, `src/routes/api/signup/+server.ts` with the following code:

```typescript title="src/routes/api/signup/+server.ts"
import { start } from "workflow/api";
import { handleUserSignup } from "../../../../workflows/user-signup";
import { json, type RequestHandler } from "@sveltejs/kit";

export const POST: RequestHandler = async ({
  request,
}: {
  request: Request;
}) => {
  const { email } = await request.json();

  // Executes asynchronously and doesn't block your app
  await start(handleUserSignup, [email]);

  return json({ message: "User signup workflow started" });
};

```

This route handler creates a `POST` request endpoint at `/api/signup` that will trigger your workflow.

<Callout>
Workflows can be triggered from API routes or any server-side code.
</Callout>

</Step>

</Steps>

## Run in development

To start your development server, run the following command in your terminal in the SvelteKit root directory:

```bash
npm run dev
```

Once your development server is running, you can trigger your workflow by running this command in the terminal:

```bash
curl -X POST --json '{"email":"hello@example.com"}' http://localhost:5173/api/signup
```

Check the SvelteKit development server logs to see your workflow execute as well as the steps that are being processed.

Additionally, you can use the [Workflow SDK CLI or Web UI](/docs/observability) to inspect your workflow runs and steps in detail.

```bash
# Open the observability Web UI
npx workflow web
# or if you prefer a terminal interface, use the CLI inspect command
npx workflow inspect runs
```

![Workflow SDK Web UI](/o11y-ui.png)

## Deploying to production

Workflow SDK apps currently work best when deployed to [Vercel](https://vercel.com/home) and need no special configuration.

<FluidComputeCallout />

Check the [Deploying](/docs/deploying) section to learn how your workflows can be deployed elsewhere.

## Troubleshooting

### `start()` says it received an invalid workflow function

If you see this error:

```text
'start' received an invalid workflow function. Ensure the Workflow SDK is configured correctly and the function includes a 'use workflow' directive.
```

Check both of these first:

1. The workflow function includes `"use workflow"`.
2. Your `vite.config.ts` includes the `workflow/sveltekit` plugin.

See [start-invalid-workflow-function](/docs/errors/start-invalid-workflow-function) for full examples and fixes.

## Next steps

* Learn more about the [Foundations](/docs/foundations).
* Check [Errors](/docs/errors) if you encounter issues.
* Explore the [API Reference](/docs/api-reference).