Prerender

Prerender wraps SvelteKit's prerender(). Use it for data that can be resolved while building static output, such as documentation indexes, catalogs, and public content that changes with a deployment.

Use Query for request-time reads. Do not prerender account data, cookies, permissions, or rapidly changing records.

Define a prerender function

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The basic form looks like a query but returns a plain remote effect instead of a query resource:

import { Effect, Schema } from "effect";
import { Prerender } from "svelte-effect-runtime";

export const get_docs_index = Prerender(
	Schema.String,
	(section) =>
		Effect.succeed([
			{ section, title: "Installation" },
			{ section, title: "Client syntax" },
		]),
	{
		inputs: () => ["ser", "effect"],
	},
);

inputs tells SvelteKit which arguments to resolve during the build. Each input must match the caller-side schema type.

Call the function from a component like any other remote effect:

<script lang="ts" effect>
	import { get_docs_index } from "./docs.remote";

	const pages = yield* get_docs_index("ser");
</script>

{#each pages as page}
	<p>{page.title}</p>
{/each}

Dynamic fallback

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Set dynamic: true when an input may be absent from the build list and is still safe to resolve on demand:

export const get_product = Prerender(Schema.String, (slug) => ProductRepository.find_public(slug), {
	inputs: () => ["starter", "team"],
	dynamic: true,
});

Do not enable dynamic fallback just to hide request-time behavior. A normal query states that intent more clearly and provides query caching and refresh helpers.

Runtime services

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Prerender handlers use the server runtime, so they can yield services from layers installed with ServerRuntime.make(...).

Those services must be available in the build environment. Missing secrets, network access, or unavailable infrastructure can fail the build.

Build-time boundaries

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• Keep prerendered output public and independent of the current user.
• Avoid request-scoped cookies, locals, and headers.
• Keep inputs finite when dynamic is false.
• Treat handler failure as a deployment failure unless the effect recovers explicitly.

Prerender is a read operation. Use Command or Form for writes, even if a mutation helps prepare static data elsewhere in your deployment process.