sveltejs · Rich-Harris · Sep 11, 2025 · Sep 2, 2025 · Sep 11, 2025 · Sep 11, 2025
diff --git a/.changeset/shaggy-ghosts-decide.md b/.changeset/shaggy-ghosts-decide.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: fail prerendering when remote function fails
diff --git a/packages/kit/src/runtime/server/remote.js b/packages/kit/src/runtime/server/remote.js
@@ -176,13 +176,19 @@ async function handle_remote_call_internal(event, state, options, manifest, id)
 			});
 		}
 
+		const status =
+			error instanceof HttpError || error instanceof SvelteKitError ? error.status : 500;
+
 		return json(
 			/** @type {RemoteFunctionResponse} */ ({
 				type: 'error',
 				error: await handle_error_and_jsonify(event, state, options, error),
-				status: error instanceof HttpError || error instanceof SvelteKitError ? error.status : 500
+				status
 			}),
 			{
+				// By setting a non-200 during prerendering we fail the prerender process (unless handleHttpError handles it).
+				// Errors at runtime will be passed to the client and are handled there
+				status: state.prerendering ? status : undefined,
 				headers: {
 					'cache-control': 'private, no-store'
 				}

diff --git a/packages/kit/test/build-errors/apps/prerender-remote-function-error/package.json b/packages/kit/test/build-errors/apps/prerender-remote-function-error/package.json
@@ -0,0 +1,22 @@
+{
+	"name": "prerenderable-remote-function-error",
+	"private": true,
+	"version": "0.0.1",
+	"scripts": {
+		"dev": "vite dev",
+		"build": "vite build",
+		"preview": "vite preview",
+		"prepare": "svelte-kit sync",
+		"check": "svelte-kit sync && tsc && svelte-check"
+	},
+	"devDependencies": {
+		"@sveltejs/adapter-auto": "workspace:^",
+		"@sveltejs/kit": "workspace:^",
+		"@sveltejs/vite-plugin-svelte": "catalog:",
+		"svelte": "^5.38.5",
+		"svelte-check": "^4.1.1",
+		"typescript": "^5.5.4",
+		"vite": "catalog:"
+	},
+	"type": "module"
+}
diff --git a/packages/kit/test/build-errors/apps/prerender-remote-function-error/src/app.html b/packages/kit/test/build-errors/apps/prerender-remote-function-error/src/app.html
@@ -0,0 +1,12 @@
+<!doctype html>
+<html lang="en">
+	<head>
+		<meta charset="utf-8" />
+		<link rel="icon" href="%sveltekit.assets%/favicon.png" />
+		<meta name="viewport" content="width=device-width, initial-scale=1" />
+		%sveltekit.head%
+	</head>
+	<body>
+		<div>%sveltekit.body%</div>
+	</body>
+</html>
diff --git a/packages/kit/test/build-errors/apps/prerender-remote-function-error/src/routes/+layout.js b/packages/kit/test/build-errors/apps/prerender-remote-function-error/src/routes/+layout.js
@@ -0,0 +1 @@
+export const prerender = true;
diff --git a/packages/kit/test/build-errors/apps/prerender-remote-function-error/src/routes/+page.svelte b/packages/kit/test/build-errors/apps/prerender-remote-function-error/src/routes/+page.svelte
@@ -0,0 +1,7 @@
+<script>
+	import { throws } from './data.remote.js';
+</script>
+
+{#await throws() then value}
+	{value}
+{/await}
diff --git a/...ages/kit/test/build-errors/apps/prerender-remote-function-error/src/routes/data.remote.ts b/...ages/kit/test/build-errors/apps/prerender-remote-function-error/src/routes/data.remote.ts
@@ -0,0 +1,5 @@
+import { prerender } from '$app/server';
+
+export const throws = prerender(() => {
+	throw new Error('remote function blew up');
+});
diff --git a/...s/kit/test/build-errors/apps/prerender-remote-function-error/static/favicon.png b/...s/kit/test/build-errors/apps/prerender-remote-function-error/static/favicon.png
diff --git a/packages/kit/test/build-errors/apps/prerender-remote-function-error/svelte.config.js b/packages/kit/test/build-errors/apps/prerender-remote-function-error/svelte.config.js
@@ -0,0 +1,14 @@
+import adapter from '../../../../../adapter-auto/index.js';
+
+/** @type {import('@sveltejs/kit').Config} */
+const config = {
+	kit: {
+		adapter: adapter(),
+
+		experimental: {
+			remoteFunctions: true
+		}
+	}
+};
+
+export default config;
diff --git a/packages/kit/test/build-errors/apps/prerender-remote-function-error/tsconfig.json b/packages/kit/test/build-errors/apps/prerender-remote-function-error/tsconfig.json
@@ -0,0 +1,8 @@
+{
+	"compilerOptions": {
+		"allowJs": true,
+		"checkJs": true,
+		"noEmit": true
+	},
+	"extends": "./.svelte-kit/tsconfig.json"
+}
diff --git a/packages/kit/test/build-errors/apps/prerender-remote-function-error/vite.config.js b/packages/kit/test/build-errors/apps/prerender-remote-function-error/vite.config.js
@@ -0,0 +1,23 @@
+import * as path from 'node:path';
+import { sveltekit } from '@sveltejs/kit/vite';
+
+/** @type {import('vite').UserConfig} */
+const config = {
+	build: {
+		minify: false
+	},
+
+	clearScreen: false,
+
+	logLevel: 'silent',
+
+	plugins: [sveltekit()],
+
+	server: {
+		fs: {
+			allow: [path.resolve('../../../../src')]
+		}
+	}
+};
+
+export default config;
diff --git a/packages/kit/test/build-errors/prerender.spec.js b/packages/kit/test/build-errors/prerender.spec.js
@@ -29,3 +29,15 @@ test('entry generators should match their own route', { timeout }, () => {
 		`Error: The entries export from /[slug]/[notSpecific] generated entry /whatever/specific, which was matched by /[slug]/specific - see the \`handleEntryGeneratorMismatch\` option in https://svelte.dev/docs/kit/configuration#prerender for more info.${EOL}To suppress or handle this error, implement \`handleEntryGeneratorMismatch\` in https://svelte.dev/docs/kit/configuration#prerender`
 	);
 });
+
+test('an error in a `prerender` function should fail the build', { timeout }, () => {
+	assert.throws(
+		() =>
+			execSync('pnpm build', {
+				cwd: path.join(process.cwd(), 'apps/prerender-remote-function-error'),
+				stdio: 'pipe',
+				timeout
+			}),
+		/remote function blew up/
+	);
+});
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml