withastro · matthewp · Apr 13, 2026 · Apr 3, 2026 · Apr 3, 2026 · Apr 3, 2026
diff --git a/.changeset/fix-svelte-prerender-node.md b/.changeset/fix-svelte-prerender-node.md
@@ -0,0 +1,6 @@
+---
+'@astrojs/cloudflare': patch
+'@astrojs/svelte': patch
+---
+
+Fixes `.svelte` files in `node_modules` failing with `Unknown file extension ".svelte"` when using the Cloudflare adapter with `prerenderEnvironment: 'node'`
diff --git a/packages/integrations/cloudflare/src/index.ts b/packages/integrations/cloudflare/src/index.ts
@@ -306,7 +306,6 @@ export default function createIntegration({
 									if (conf.ssr) {
 										// Cloudflare does not support externalizing modules in server environments
 										conf.ssr.external = undefined;
-										conf.ssr.noExternal = true;
 									}
 								},
 							},

diff --git a/packages/integrations/cloudflare/src/vite-plugin-dev-server-prerender-middleware.ts b/packages/integrations/cloudflare/src/vite-plugin-dev-server-prerender-middleware.ts
@@ -18,14 +18,6 @@ export function createNodePrerenderPlugin(): vite.Plugin {
 			};
 		},
 
-		// Disable dep optimization for the `prerender` environment so dependencies
-		// are loaded via native import() with correct import.meta.url semantics.
-		configEnvironment(environmentName) {
-			if (environmentName === 'prerender') {
-				return { optimizeDeps: { noDiscovery: true, include: [] } };
-			}
-		},
-
 		configureServer(server) {
 			(server as any)[devPrerenderMiddlewareSymbol] = true;
 		},

diff --git a/packages/integrations/cloudflare/test/fixtures/prerender-node-env/astro.config.mjs b/packages/integrations/cloudflare/test/fixtures/prerender-node-env/astro.config.mjs
@@ -1,3 +1,6 @@
 import { defineConfig } from 'astro/config';
+import svelte from '@astrojs/svelte';
 
-export default defineConfig({});
+export default defineConfig({
+	integrations: [svelte()],
+});
diff --git a/...ges/integrations/cloudflare/test/fixtures/prerender-node-env/fake-svelte-pkg/package.json b/...ges/integrations/cloudflare/test/fixtures/prerender-node-env/fake-svelte-pkg/package.json
@@ -0,0 +1,11 @@
+{
+  "name": "fake-svelte-pkg",
+  "version": "1.0.0",
+  "type": "module",
+  "exports": {
+    ".": "./src/index.js"
+  },
+  "peerDependencies": {
+    "svelte": "^5.0.0"
+  }
+}
diff --git a/...ions/cloudflare/test/fixtures/prerender-node-env/fake-svelte-pkg/src/FakeComponent.svelte b/...ions/cloudflare/test/fixtures/prerender-node-env/fake-svelte-pkg/src/FakeComponent.svelte
@@ -0,0 +1 @@
+<p>Hello from fake svelte component</p>
diff --git a/...ges/integrations/cloudflare/test/fixtures/prerender-node-env/fake-svelte-pkg/src/index.js b/...ges/integrations/cloudflare/test/fixtures/prerender-node-env/fake-svelte-pkg/src/index.js
@@ -0,0 +1 @@
+export { default as FakeComponent } from './FakeComponent.svelte';
diff --git a/packages/integrations/cloudflare/test/fixtures/prerender-node-env/package.json b/packages/integrations/cloudflare/test/fixtures/prerender-node-env/package.json
@@ -4,6 +4,9 @@
   "private": true,
   "dependencies": {
     "@astrojs/cloudflare": "workspace:*",
-    "astro": "workspace:*"
+    "@astrojs/svelte": "workspace:*",
+    "astro": "workspace:*",
+    "svelte": "^5.0.0",
+    "fake-svelte-pkg": "file:./fake-svelte-pkg"
   }
 }
diff --git a/...egrations/cloudflare/test/fixtures/prerender-node-env/src/components/SvelteWrapper.svelte b/...egrations/cloudflare/test/fixtures/prerender-node-env/src/components/SvelteWrapper.svelte
@@ -0,0 +1,7 @@
+<script>
+  import { FakeComponent } from 'fake-svelte-pkg';
+</script>
+
+<div id="svelte-wrapper">
+  <FakeComponent />
+</div>
diff --git a/packages/integrations/cloudflare/test/fixtures/prerender-node-env/src/pages/svelte.astro b/packages/integrations/cloudflare/test/fixtures/prerender-node-env/src/pages/svelte.astro
@@ -0,0 +1,15 @@
+---
+export const prerender = true;
+
+import SvelteWrapper from '../components/SvelteWrapper.svelte';
+---
+
+<html lang="en">
+	<head>
+		<meta charset="utf-8" />
+		<title>Svelte Prerender Test</title>
+	</head>
+	<body>
+		<SvelteWrapper />
+	</body>
+</html>
diff --git a/packages/integrations/cloudflare/test/prerender-node-env.test.js b/packages/integrations/cloudflare/test/prerender-node-env.test.js
@@ -39,6 +39,20 @@ describe('prerenderEnvironment: node', () => {
 		);
 	});
 
+	it('renders svelte component that imports .svelte files from node_modules', async () => {
+		const res = await fixture.fetch('/svelte');
+		assert.equal(res.status, 200);
+		const html = await res.text();
+		assert.ok(
+			html.includes('id="svelte-wrapper"'),
+			'Expected the prerendered page to contain the svelte wrapper',
+		);
+		assert.ok(
+			html.includes('Hello from fake svelte component'),
+			'Expected the fake svelte component to be rendered',
+		);
+	});
+
 	it('includes styles in prerendered page', async () => {
 		const res = await fixture.fetch('/');
 		const html = await res.text();

diff --git a/packages/integrations/svelte/package.json b/packages/integrations/svelte/package.json
@@ -40,7 +40,8 @@
   "dependencies": {
     "@sveltejs/vite-plugin-svelte": "^6.2.4",
     "svelte2tsx": "^0.7.52",
-    "vite": "^7.3.1"
+    "vite": "^7.3.1",
+    "vitefu": "^1.1.2"
   },
   "devDependencies": {
     "astro": "workspace:*",

diff --git a/packages/integrations/svelte/src/index.ts b/packages/integrations/svelte/src/index.ts
@@ -1,7 +1,9 @@
 import type { Options } from '@sveltejs/vite-plugin-svelte';
 import { svelte, vitePreprocess } from '@sveltejs/vite-plugin-svelte';
 import type { AstroIntegration, AstroRenderer } from 'astro';
+import { fileURLToPath } from 'node:url';
 import type { Plugin } from 'vite';
+import { crawlFrameworkPkgs } from 'vitefu';
 import { createSvelteOptimizeEsbuildPlugins } from './optimize-esbuild-plugins.js';
 
 function getRenderer(): AstroRenderer {
@@ -18,28 +20,63 @@ export default function svelteIntegration(options?: Options): AstroIntegration {
 	return {
 		name: '@astrojs/svelte',
 		hooks: {
-			'astro:config:setup': async ({ updateConfig, addRenderer }) => {
+			'astro:config:setup': async ({ config, updateConfig, addRenderer }) => {
 				addRenderer(getRenderer());
+
+				const sveltePackages = await crawlFrameworkPkgs({
+					root: fileURLToPath(config.root),
+					isBuild: false,
+					isFrameworkPkgByJson(pkgJson) {
+						return !!pkgJson.peerDependencies?.svelte;
+					},
+				});
+
 				updateConfig({
 					vite: {
-						plugins: [svelte(options), configEnvironmentPlugin()],
+						plugins: [svelte(options), configEnvironmentPlugin(sveltePackages.ssr.noExternal)],
 					},
 				});
 			},
 		},
 	};
 }
 
-function configEnvironmentPlugin(): Plugin {
+function configEnvironmentPlugin(svelteNoExternal: string[]): Plugin {
 	return {
 		name: '@astrojs/svelte:config-environment',
 		configEnvironment(environmentName, options) {
+			const isServer = environmentName !== 'client';
+
+			if (isServer && svelteNoExternal.length > 0) {
+				// Add svelte framework packages to noExternal so they go through
+				// Vite's transform pipeline (Node can't import .svelte files natively).
+				const result: any = {
+					resolve: {
+						noExternal: svelteNoExternal,
+					},
+				};
+
+				if (
+					(environmentName === 'ssr' || environmentName === 'prerender') &&
+					options.optimizeDeps?.noDiscovery === false
+				) {
+					result.optimizeDeps = {
+						include: ['svelte/server', 'svelte/internal/server'],
+						exclude: ['@astrojs/svelte/server.js'],
+						esbuildOptions: {
+							plugins: createSvelteOptimizeEsbuildPlugins('server'),
+						},
+					};
+				}
+
+				return result;
+			}
+
 			if (
 				environmentName === 'client' ||
 				((environmentName === 'ssr' || environmentName === 'prerender') &&
 					options.optimizeDeps?.noDiscovery === false)
 			) {
-				const isServer = environmentName !== 'client';
 				return {
 					optimizeDeps: {
 						include: isServer
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		export { default as FakeComponent } from './FakeComponent.svelte';