SvelteKit

Fly.Website.SvelteKit deploys a SvelteKit app to Fly. It builds the app with SvelteKit’s own Vite pipeline and an in-memory Node adapter. Client assets and prerendered pages bake into the Machine image and are served first; dynamic routes run in the kit handler on port 3000. Alchemy creates a Fly.App if you omit app, a Fly.Service on that App, and a shared IPv4 so https://{app}.fly.dev answers. Your vite.config.ts loads natively; there is no svelte.config.js to write (kit v3 dropped it) and no adapter to install.

Install

The build integration is not bundled with alchemy. Install @alchemy.run/frontend-frameworks; the resource loads its /sveltekit and /sveltekit/node exports from your project at deploy time. It is only used at build time, so a dev dependency is enough:

bun add -d @alchemy.run/frontend-frameworks

npm install -D @alchemy.run/frontend-frameworks

pnpm add -D @alchemy.run/frontend-frameworks

yarn add -D @alchemy.run/frontend-frameworks

Configure SvelteKit

Your project’s vite.config.ts loads natively — your Vite plugins and the kit options in your sveltekit(...) call all apply as usual. Alchemy injects its Node adapter (replacing any adapter you declare, with a warning), so a fresh SvelteKit project deploys as-is. Deploy-specific kit overrides can also be passed via the kit prop, which merges over your sveltekit(...) options — see Kit options below. A project without a vite.config.* works too: the resource falls back to a fully programmatic build.

Declare the Website

Declare the site as a module-level const (rather than inline in the Stack):

import * as Fly from "alchemy/Fly";

export const Website = Fly.Website.SvelteKit("Website");

Omit app to create a Fly.App under the site namespace. Pass an existing App to share it with other resources.

Add it to the Stack

Yield the site from your Stack and return its URL:

import * as Alchemy from "alchemy";
import * as Effect from "effect/Effect";

export default Alchemy.Stack(
  "MySvelteKitSite",
  {
    providers: Fly.providers(),
    state: Alchemy.localState(),
  },
  Effect.gen(function* () {
    const site = yield* Website;
    return { url: site.url };
  }),
);

Routes with export const prerender = true are baked into the image and served as static files first; server routes (+server.ts) and server load functions run in the kit handler on the Machine.

Add environment variables

Process environment is a top-level env map:

export const Website = Fly.Website.SvelteKit("Website", {
  env: {
    GREETING: "Hello from alchemy",
    API_BASE: "https://api.example.com",
  },
});

The values are copied onto process.env before the build (and the dev server) and onto the Machine at deploy time, so server code reads the same keys in both modes.

Read the environment in server code

The Kit server runs in Node on the Machine, so server routes read the environment from process.env (or kit’s $env/dynamic/private, which is initialized from it):

export const load = () => {
  return { greeting: process.env.GREETING ?? "hello" };
};

Kit options

Since kit v3 there is no svelte.config.js — kit options live in the sveltekit(...) call in your vite.config.ts, which loads natively:

import { sveltekit } from "@sveltejs/kit/vite";
import tailwindcss from "@tailwindcss/vite";
import { defineConfig } from "vite";

export default defineConfig({
  plugins: [
    tailwindcss(),
    sveltekit({
      alias: { $lib: "src/lib" },
    }),
  ],
});

The kit prop on the resource is a deploy-time override layer merged over those options (the override wins). It must be JSON-serializable:

export const Website = Fly.Website.SvelteKit("Website", {
  kit: {
    paths: { base: "/docs" },
  },
});

Don’t set kit.adapter — Alchemy injects its Node adapter (an adapter declared in your sveltekit(...) call is replaced with a warning).

Local dev

bun alchemy dev

alchemy dev runs SvelteKit’s own Vite dev server — Node SSR with full HMR — instead of deploying; site.url is the local address and no Fly resources are created (app, service, ip, and certificate are undefined). Wrap the site in Alchemy.remote() to deploy the live App even during dev.

Custom domain

const site = yield* Fly.Website.SvelteKit("Web", {
  domain: "app.example.com",
});

Alchemy requests an ACME Fly.Certificate on the App. Point DNS at the App first — v1 does not create records. url becomes https://app.example.com.