withastro · ematipico · Mar 25, 2026 · Mar 25, 2026
diff --git a/.changeset/fix-queued-rendering-html-pages.md b/.changeset/fix-queued-rendering-html-pages.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fixes `experimental.queuedRendering` incorrectly escaping the HTML output of `.html` page files, causing the page content to render as plain text instead of HTML in the browser.
diff --git a/packages/astro/src/runtime/server/render/page.ts b/packages/astro/src/runtime/server/render/page.ts
@@ -2,6 +2,7 @@ import type { RouteData, SSRResult } from '../../../types/public/internal.js';
 import { renderToAsyncIterable, renderToReadableStream, renderToString } from './astro/render.js';
 import { encoder } from './common.js';
 import { type NonAstroPageComponent, renderComponentToString } from './component.js';
+import { markHTMLString } from '../escape.js';
 import { renderCspContent } from './csp.js';
 import type { AstroComponentFactory } from './index.js';
 import { isDeno, isNode } from './util.js';
@@ -32,7 +33,13 @@ export async function renderPage(
 			// then process it through the queue system
 
 			// Call the component function to get the vnode tree
-			const vnode = await (componentFactory as any)(pageProps);
+			let vnode = await (componentFactory as any)(pageProps);
+
+			// .html pages return plain strings that are already valid HTML.
+			// Mark them as safe HTML so the queue builder doesn't escape the content.
+			if ((componentFactory as any)['astro:html'] && typeof vnode === 'string') {
+				vnode = markHTMLString(vnode);
+			}
 
 			// Build a render queue from the vnode tree
 			const queue = await buildRenderQueue(

diff --git a/packages/astro/test/units/render/queue-rendering.test.js b/packages/astro/test/units/render/queue-rendering.test.js
@@ -3,6 +3,7 @@ import { describe, it } from 'node:test';
 import { buildRenderQueue } from '../../../dist/runtime/server/render/queue/builder.js';
 import { renderQueue } from '../../../dist/runtime/server/render/queue/renderer.js';
 import { NodePool } from '../../../dist/runtime/server/render/queue/pool.js';
+import { renderPage } from '../../../dist/runtime/server/render/page.js';
 
 /**
  * Tests for the queue-based rendering engine
@@ -261,3 +262,84 @@ describe('Queue-based rendering engine', () => {
 		});
 	});
 });
+
+/**
+ * Regression tests for issue #16053:
+ * queuedRendering breaks .html pages by escaping their raw HTML string output.
+ */
+describe('renderPage() with queuedRendering and .html pages', () => {
+	function createMockResultWithQueue() {
+		const pool = new NodePool(1000);
+		return {
+			_metadata: {
+				hasHydrationScript: false,
+				rendererSpecificHydrationScripts: new Set(),
+				hasRenderedHead: false,
+				renderedScripts: new Set(),
+				hasDirectives: new Set(),
+				hasRenderedServerIslandRuntime: false,
+				headInTree: false,
+				extraHead: [],
+				extraStyleHashes: [],
+				extraScriptHashes: [],
+				propagators: new Set(),
+			},
+			styles: new Set(),
+			scripts: new Set(),
+			links: new Set(),
+			componentMetadata: new Map(),
+			cancelled: false,
+			compressHTML: false,
+			partial: false,
+			response: { status: 200, statusText: 'OK', headers: new Headers() },
+			shouldInjectCspMetaTags: false,
+			_experimentalQueuedRendering: {
+				enabled: true,
+				pool,
+			},
+		};
+	}
+
+	it('does not escape HTML tags when rendering a .html page component', async () => {
+		// Simulate the component factory generated by vite-plugin-html for a .html file.
+		// These return a plain string and have `astro:html = true`.
+		const htmlPageFactory = function render(_props) {
+			return '<body>\n  <script src="https://unpkg.com/@sveltia/cms/dist/sveltia-cms.js"></script>\n</body>';
+		};
+		htmlPageFactory['astro:html'] = true;
+		htmlPageFactory.moduleId = 'src/pages/admin/index.html';
+
+		const result = createMockResultWithQueue();
+
+		const response = await renderPage(result, htmlPageFactory, {}, null, false);
+		const html = await response.text();
+
+		// The raw <script> tag must appear verbatim — not HTML-escaped
+		assert.ok(
+			html.includes('<script src="https://unpkg.com/@sveltia/cms/dist/sveltia-cms.js"></script>'),
+			`Expected unescaped <script> tag in output, got:\n${html}`,
+		);
+		assert.ok(
+			!html.includes('&lt;script'),
+			`Expected no HTML-escaped tags in output, got:\n${html}`,
+		);
+	});
+
+	it('still escapes HTML in non-.html page components with queuedRendering', async () => {
+		// A regular (non-.html) component factory should NOT have astro:html = true,
+		// so raw string output from it should be treated as text and escaped.
+		const regularFactory = function render(_props) {
+			return '<script>alert("xss")</script>';
+		};
+		// No astro:html flag set — this is the default for non-.html components
+		regularFactory.moduleId = 'src/pages/regular.astro';
+
+		const result = createMockResultWithQueue();
+
+		const response = await renderPage(result, regularFactory, {}, null, false);
+		const html = await response.text();
+
+		assert.ok(!html.includes('<script>alert'), `Expected escaped output, got:\n${html}`);
+		assert.ok(html.includes('&lt;script&gt;'), `Expected HTML-escaped output, got:\n${html}`);
+	});
+});