code · pull · Mar 13, 2026 · Mar 13, 2026 · Mar 13, 2026
diff --git a/.changeset/fix-before-hydration-client.md b/.changeset/fix-before-hydration-client.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Emit the `before-hydration` script chunk for the `client` Vite environment. The chunk was only emitted for `prerender` and `ssr` environments, causing a 404 when browsers tried to load it. This broke hydration for any integration using `injectScript('before-hydration', ...)`, including Lit SSR.
diff --git a/.changeset/small-jeans-whisper.md b/.changeset/small-jeans-whisper.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fix `Astro.url.pathname` for the root page when using `build.format: "file"` so it resolves to `/index.html` instead of `/.html` during builds.
diff --git a/packages/astro/src/core/build/generate.ts b/packages/astro/src/core/build/generate.ts
@@ -541,7 +541,11 @@ function getUrlForPath(
 	}
 	let buildPathname: string;
 	if (pathname === '/' || pathname === '') {
-		buildPathname = collapseDuplicateTrailingSlashes(base + ending, trailingSlash !== 'never');
+		if (format === 'file') {
+			buildPathname = joinPaths(base, 'index.html');
+		} else {
+			buildPathname = collapseDuplicateTrailingSlashes(base + ending, trailingSlash !== 'never');
+		}
 	} else if (routeType === 'endpoint') {
 		const buildPathRelative = removeLeadingForwardSlash(pathname);
 		buildPathname = joinPaths(base, buildPathRelative);

diff --git a/packages/astro/src/vite-plugin-scripts/index.ts b/packages/astro/src/vite-plugin-scripts/index.ts
@@ -61,7 +61,8 @@ export default function astroScriptsPlugin({ settings }: { settings: AstroSettin
 			const hasHydrationScripts = settings.scripts.some((s) => s.stage === 'before-hydration');
 			if (
 				hasHydrationScripts &&
-				(this.environment.name === ASTRO_VITE_ENVIRONMENT_NAMES.prerender ||
+				(this.environment.name === ASTRO_VITE_ENVIRONMENT_NAMES.client ||
+					this.environment.name === ASTRO_VITE_ENVIRONMENT_NAMES.prerender ||
 					this.environment.name === ASTRO_VITE_ENVIRONMENT_NAMES.ssr)
 			) {
 				this.emitFile({

diff --git a/packages/astro/test/before-hydration.test.js b/packages/astro/test/before-hydration.test.js
@@ -59,6 +59,16 @@ describe('Astro Scripts before-hydration', () => {
 					let $ = cheerio.load(html);
 					assert.equal($('astro-island[before-hydration-url]').length, 1);
 				});
+
+				it('Emits the before-hydration chunk to the client output', async () => {
+					let html = await fixture.readFile('/index.html');
+					let $ = cheerio.load(html);
+					let url = $('astro-island').attr('before-hydration-url');
+					assert.ok(url, 'before-hydration-url attribute should have a value');
+					// The URL should point to a file that exists in the build output
+					let content = await fixture.readFile(url);
+					assert.ok(content, 'before-hydration chunk should exist in the client build output');
+				});
 			});
 		});
 

diff --git a/packages/astro/test/fixtures/page-format/src/pages/index.astro b/packages/astro/test/fixtures/page-format/src/pages/index.astro
@@ -1,6 +1,10 @@
 ---
+const url = Astro.url;
 ---
 <html>
 	<head><title>testing</title></head>
-	<body><h1>testing</h1></body>
+	<body>
+		<h1>testing</h1>
+		<h2 id="url">{url.pathname}</h2>
+	</body>
 </html>
diff --git a/packages/astro/test/fixtures/page-format/src/pages/nested/page.astro b/packages/astro/test/fixtures/page-format/src/pages/nested/page.astro
@@ -1,4 +1,6 @@
 ---
 const another = new URL('./another/', Astro.url);
+const url = Astro.url;
 ---
 <a id="another" href={another.pathname}></a>
+<p id="url">{url.pathname}</p>
diff --git a/packages/astro/test/page-format.test.js b/packages/astro/test/page-format.test.js
@@ -43,6 +43,18 @@ describe('build.format', () => {
 				await fixture.build();
 			});
 
+			it('Astro.url pathname includes /index.html for root page in build', async () => {
+				let html = await fixture.readFile('/index.html');
+				let $ = cheerio.load(html);
+				assert.equal($('#url').text(), '/index.html');
+			});
+
+			it('Astro.url pathname includes .html for non-root pages in build', async () => {
+				let html = await fixture.readFile('/nested/page.html');
+				let $ = cheerio.load(html);
+				assert.equal($('#url').text(), '/nested/page.html');
+			});
+
 			it('relative urls created point to sibling folders', async () => {
 				let html = await fixture.readFile('/nested/page.html');
 				let $ = cheerio.load(html);