sveltekit-remote-functions

SvelteKit Remote Functions

Current Status

Remote functions are experimental in SvelteKit 2.58. Prefer enabling them in vite.config.ts via the SvelteKit Vite plugin:

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

export default defineConfig({
	plugins: [
		sveltekit({
			experimental: { remoteFunctions: true },
			compilerOptions: { experimental: { async: true } } // only for await in components
		})
	]
});

Quick Start

File naming: export remote functions from *.remote.ts or *.remote.js. Remote files can live anywhere under src except src/lib/server.

Which function?

• Dynamic reads → query()
• Realtime server streams → query.live()
• Progressive forms → form()
• Event-handler mutations → command()
• Build-time/static reads → prerender()

Example

// posts.remote.ts
import { command, query, requested } from "$app/server";
import * as v from "valibot";

export const getPosts = query(
	v.object({ tag: v.optional(v.string()) }),
	async (filter) => {
		return db.posts.find(filter);
	},
);

export const createPost = command(
	v.object({ title: v.string() }),
	async (data) => {
		await db.posts.create(data);

		for (const { query } of requested(getPosts, 5)) {
			void query.refresh();
		}
	},
);

Client:

<script lang="ts">
	import { createPost, getPosts } from './posts.remote';

	const posts = $derived(await getPosts({ tag: 'svelte' }));
</script>

<button onclick={() => createPost({ title: 'New' }).updates(getPosts)}>
	Create
</button>

Current Rules

• svelte.config.js still works in Kit 2, but Kit 3 will read Kit config from the Vite plugin instead.
• Remote functions always run on the server, even when called from the browser.
• Args/returns use devalue; avoid functions, class instances, symbols, circular refs, and RegExp.
• Validate exposed inputs with Standard Schema (valibot, zod, arktype, etc.) or use .unchecked/'unchecked' deliberately.
• query.batch() batches calls from the same macrotask to solve n+1 reads.
• query.live() returns an async iterable; SSR uses the first yield, clients stay connected while rendered.
• Prefer event-driven live queries over polling when a mutation can notify listeners (Promise.withResolvers()/pubsub).
• Live queries expose connected and reconnect(), but no refresh(); .run() returns Promise<AsyncGenerator<T>>.
• Do not service-worker-cache live query responses; exclude Cache-Control: no-store streams.
• form().enhance() submit() returns true when submission is valid/successful and false for validation failures.
• .updates() is client-requested; server handlers must opt in with requested(queryFn, limit).
• requested() now yields { arg, query }; call query.refresh()/query.set(...) on the bound instance.
• limit is required for requested() to cap client-controlled refresh requests.
• Inside command/form handlers, use void query.refresh()/void query.set(value); SvelteKit awaits and serializes the updates.
• For live queries, single-flight mutations can call void live_query.reconnect().
• Prefer form() over command() where progressive enhancement matters.
• Use prerender() for data that changes at most once per deployment.
• Last verified: 2026-06-08

Reference Files

• references/remote-functions.md - Current patterns, examples, and gotchas