withastro · matthewp · Aug 27, 2026 · Aug 27, 2026
diff --git a/.changeset/metal-pans-allow.md b/.changeset/metal-pans-allow.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fixes SSR manifest containing stale `entryModules` references to prerender-only chunks that no longer exist in the final build output
diff --git a/packages/astro/src/core/build/internal.ts b/packages/astro/src/core/build/internal.ts
@@ -34,6 +34,15 @@ export interface BuildInternals {
 	// Used to render pages with the correct specifiers.
 	entrySpecifierToBundleMap: Map<string, string>;
 
+	/**
+	 * Specifiers written to `entrySpecifierToBundleMap` by the prerender environment
+	 * that have not been overwritten by the SSR or client environments. These point
+	 * to chunk files inside the prerender output directory, which is deleted after
+	 * page generation. They must be stripped from the SSR manifest to avoid dangling
+	 * references.
+	 */
+	prerenderOnlyEntrySpecifiers: Set<string>;
+
 	/**
 	 * A map for page-specific information.
 	 */
@@ -167,6 +176,7 @@ export function createBuildInternals(): BuildInternals {
 		prerenderCssAssetByModuleKey: new Map(),
 		inlinedScripts: new Map(),
 		entrySpecifierToBundleMap: new Map<string, string>(),
+		prerenderOnlyEntrySpecifiers: new Set<string>(),
 		pagesByKeys: new Map(),
 		pagesByViteID: new Map(),
 		pagesByClientOnly: new Map(),

diff --git a/packages/astro/src/core/build/plugins/plugin-internals.ts b/packages/astro/src/core/build/plugins/plugin-internals.ts
@@ -78,6 +78,7 @@ export function pluginInternals(
 				);
 			}
 			await Promise.all(promises);
+			const isPrerender = this.environment?.name === ASTRO_VITE_ENVIRONMENT_NAMES.prerender;
 			for (const [_, chunk] of Object.entries(bundle)) {
 				if (chunk.fileName.startsWith(options.settings.config.build.assets)) {
 					internals.clientChunksAndAssets.add(chunk.fileName);
@@ -86,7 +87,14 @@ export function pluginInternals(
 				if (chunk.type === 'chunk' && chunk.facadeModuleId) {
 					const specifiers = mapping.get(chunk.facadeModuleId) || new Set([chunk.facadeModuleId]);
 					for (const specifier of specifiers) {
-						internals.entrySpecifierToBundleMap.set(normalizeEntryId(specifier), chunk.fileName);
+						const normalizedId = normalizeEntryId(specifier);
+						internals.entrySpecifierToBundleMap.set(normalizedId, chunk.fileName);
+						if (isPrerender) {
+							internals.prerenderOnlyEntrySpecifiers.add(normalizedId);
+						} else {
+							// Present in SSR or client — no longer prerender-only
+							internals.prerenderOnlyEntrySpecifiers.delete(normalizedId);
+						}
 					}
 				}
 			}

diff --git a/packages/astro/src/core/build/plugins/plugin-manifest.ts b/packages/astro/src/core/build/plugins/plugin-manifest.ts
@@ -101,7 +101,8 @@ export async function manifestBuildPostHook(
 		// HTML on disk already has them inlined, and the SSR worker never renders
 		// these routes. Stripping keeps the entry chunk small on platforms like
 		// Cloudflare Workers that re-parse it on every cold isolate start.
-		const ssrManifest = stripPrerenderedRouteStyles(manifest);
+		let ssrManifest = stripPrerenderedRouteStyles(manifest);
+		ssrManifest = stripPrerenderOnlyEntryModules(ssrManifest, internals);
 		const code = injectManifest(ssrManifest, ssrManifestChunk.code);
 		mutate(ssrManifestChunk.fileName, code, false);
 	}
@@ -173,6 +174,26 @@ function stripPrerenderedRouteStyles(manifest: SerializedSSRManifest): Serialize
 	return stripped ? { ...manifest, routes } : manifest;
 }
 
+/**
+ * Returns a copy of the manifest with `entryModules` entries removed for
+ * specifiers that were only emitted by the prerender environment. Those
+ * chunks live in the prerender output directory, which is deleted after
+ * page generation, so referencing them from the SSR manifest would produce
+ * dangling asset URLs at runtime.
+ */
+function stripPrerenderOnlyEntryModules(
+	manifest: SerializedSSRManifest,
+	internals: BuildInternals,
+): SerializedSSRManifest {
+	if (internals.prerenderOnlyEntrySpecifiers.size === 0) return manifest;
+	const filtered = Object.fromEntries(
+		Object.entries(manifest.entryModules).filter(
+			([key]) => !internals.prerenderOnlyEntrySpecifiers.has(key),
+		),
+	);
+	return { ...manifest, entryModules: filtered };
+}
+
 async function buildManifest(
 	opts: StaticBuildOptions,
 	internals: BuildInternals,

diff --git a/packages/astro/test/units/build/prerender-entry-specifiers.test.ts b/packages/astro/test/units/build/prerender-entry-specifiers.test.ts
@@ -0,0 +1,39 @@
+import * as assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import { createBuildInternals } from '../../../dist/core/build/internal.js';
+
+describe('prerenderOnlyEntrySpecifiers', () => {
+	it('is initialized as an empty set', () => {
+		const internals = createBuildInternals();
+		assert.ok(internals.prerenderOnlyEntrySpecifiers instanceof Set);
+		assert.equal(internals.prerenderOnlyEntrySpecifiers.size, 0);
+	});
+
+	it('tracks specifiers added by the prerender environment', () => {
+		const internals = createBuildInternals();
+		internals.prerenderOnlyEntrySpecifiers.add('/project/src/lib/lazy.mjs');
+		assert.ok(internals.prerenderOnlyEntrySpecifiers.has('/project/src/lib/lazy.mjs'));
+	});
+
+	it('removes specifier when also present in SSR or client environment', () => {
+		const internals = createBuildInternals();
+		// Simulates prerender writing first
+		internals.prerenderOnlyEntrySpecifiers.add('/project/src/lib/shared.mjs');
+		// Simulates SSR overwriting — the specifier is no longer prerender-only
+		internals.prerenderOnlyEntrySpecifiers.delete('/project/src/lib/shared.mjs');
+		assert.equal(internals.prerenderOnlyEntrySpecifiers.has('/project/src/lib/shared.mjs'), false);
+	});
+
+	it('retains specifiers not overwritten by later environments', () => {
+		const internals = createBuildInternals();
+		// Prerender adds two entries
+		internals.prerenderOnlyEntrySpecifiers.add('/project/src/lib/lazy.mjs');
+		internals.prerenderOnlyEntrySpecifiers.add('/project/src/lib/shared.mjs');
+		// SSR overwrites only shared.mjs
+		internals.prerenderOnlyEntrySpecifiers.delete('/project/src/lib/shared.mjs');
+		// lazy.mjs remains prerender-only
+		assert.ok(internals.prerenderOnlyEntrySpecifiers.has('/project/src/lib/lazy.mjs'));
+		assert.equal(internals.prerenderOnlyEntrySpecifiers.has('/project/src/lib/shared.mjs'), false);
+		assert.equal(internals.prerenderOnlyEntrySpecifiers.size, 1);
+	});
+});