diff --git a/.changeset/olive-bags-think.md b/.changeset/olive-bags-think.md
new file mode 100644
index 000000000..70fc7501e
--- /dev/null
+++ b/.changeset/olive-bags-think.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fix duplicated Astro and Vite injected styles
diff --git a/packages/astro/e2e/css-sourcemaps.test.js b/packages/astro/e2e/css-sourcemaps.test.js
deleted file mode 100644
index 4ea3fc0e2..000000000
--- a/packages/astro/e2e/css-sourcemaps.test.js
+++ /dev/null
@@ -1,36 +0,0 @@
-import { expect } from '@playwright/test';
-import { testFactory } from './test-utils.js';
-
-const test = testFactory({
-	root: './fixtures/css/',
-});
-
-let devServer;
-
-test.beforeAll(async ({ astro }) => {
-	devServer = await astro.startDevServer();
-});
-
-test.afterAll(async () => {
-	await devServer.stop();
-});
-
-test.describe('CSS Sourcemap HMR', () => {
-	test('removes Astro-injected CSS once Vite-injected CSS loads', async ({ page, astro }) => {
-		const html = await astro.fetch('/').then((res) => res.text());
-
-		// style[data-astro-dev-id] should exist in initial SSR'd markup
-		expect(html).toMatch('data-astro-dev-id');
-
-		await page.goto(astro.resolveUrl('/'));
-
-		// Ensure JS has initialized
-		await page.waitForTimeout(500);
-
-		// style[data-astro-dev-id] should NOT exist once JS runs
-		expect(await page.locator('style[data-astro-dev-id]').count()).toEqual(0);
-
-		// style[data-vite-dev-id] should exist now
-		expect(await page.locator('style[data-vite-dev-id]').count()).toBeGreaterThan(0);
-	});
-});
diff --git a/packages/astro/e2e/css.test.js b/packages/astro/e2e/css.test.js
index b302d9d90..3e0486d0f 100644
--- a/packages/astro/e2e/css.test.js
+++ b/packages/astro/e2e/css.test.js
@@ -29,21 +29,9 @@ test.describe('CSS HMR', () => {
 		await expect(h).toHaveCSS('color', 'rgb(0, 128, 0)');
 	});
 
-	test('removes Astro-injected CSS once Vite-injected CSS loads', async ({ page, astro }) => {
+	test('removes Astro-injected CSS once Vite-injected CSS loads', async ({ astro }) => {
 		const html = await astro.fetch('/').then((res) => res.text());
-
-		// style[data-astro-dev-id] should exist in initial SSR'd markup
-		expect(html).toMatch('data-astro-dev-id');
-
-		await page.goto(astro.resolveUrl('/'));
-
-		// Ensure JS has initialized
-		await page.waitForTimeout(500);
-
-		// style[data-astro-dev-id] should NOT exist once JS runs
-		expect(await page.locator('style[data-astro-dev-id]').count()).toEqual(0);
-
-		// style[data-vite-dev-id] should exist now
-		expect(await page.locator('style[data-vite-dev-id]').count()).toBeGreaterThan(0);
+		// style[data-vite-dev-id] should exist in initial SSR'd markup
+		expect(html).toMatch('data-vite-dev-id');
 	});
 });
diff --git a/packages/astro/e2e/fixtures/css-sourcemaps/astro.config.mjs b/packages/astro/e2e/fixtures/css-sourcemaps/astro.config.mjs
deleted file mode 100644
index 7e8fac1e7..000000000
--- a/packages/astro/e2e/fixtures/css-sourcemaps/astro.config.mjs
+++ /dev/null
@@ -1,7 +0,0 @@
-export default {
-	vite: {
-		css: {
-			devSourcemap: true,
-		}
-	}
-};
diff --git a/packages/astro/e2e/fixtures/css-sourcemaps/package.json b/packages/astro/e2e/fixtures/css-sourcemaps/package.json
deleted file mode 100644
index 1fa4c2c79..000000000
--- a/packages/astro/e2e/fixtures/css-sourcemaps/package.json
+++ /dev/null
@@ -1,8 +0,0 @@
-{
-  "name": "@e2e/css-sourcemaps",
-  "version": "0.0.0",
-  "private": true,
-  "dependencies": {
-    "astro": "workspace:*"
-  }
-}
diff --git a/packages/astro/e2e/fixtures/css-sourcemaps/src/env.d.ts b/packages/astro/e2e/fixtures/css-sourcemaps/src/env.d.ts
deleted file mode 100644
index 8c34fb45e..000000000
--- a/packages/astro/e2e/fixtures/css-sourcemaps/src/env.d.ts
+++ /dev/null
@@ -1 +0,0 @@
-/// <reference types="astro/client" />
\ No newline at end of file
diff --git a/packages/astro/e2e/fixtures/css-sourcemaps/src/pages/index.astro b/packages/astro/e2e/fixtures/css-sourcemaps/src/pages/index.astro
deleted file mode 100644
index 7275177f9..000000000
--- a/packages/astro/e2e/fixtures/css-sourcemaps/src/pages/index.astro
+++ /dev/null
@@ -1,9 +0,0 @@
-<h1>hello world</h1>
-
-<style>
-  @import "../styles/main.css";
-
-  h1 {
-    color: var(--h1-color);
-  }
-</style>
diff --git a/packages/astro/e2e/fixtures/css-sourcemaps/src/styles/main.css b/packages/astro/e2e/fixtures/css-sourcemaps/src/styles/main.css
deleted file mode 100644
index c80a6cde1..000000000
--- a/packages/astro/e2e/fixtures/css-sourcemaps/src/styles/main.css
+++ /dev/null
@@ -1,3 +0,0 @@
-:root {
-  --h1-color: red;
-}
diff --git a/packages/astro/e2e/view-transitions.test.js b/packages/astro/e2e/view-transitions.test.js
index 05a8f8ad0..a04b905af 100644
--- a/packages/astro/e2e/view-transitions.test.js
+++ b/packages/astro/e2e/view-transitions.test.js
@@ -631,7 +631,7 @@ test.describe('View Transitions', () => {
 	});
 
 	test('client:only styles are retained on transition', async ({ page, astro }) => {
-		const totalExpectedStyles = 8;
+		const totalExpectedStyles = 7;
 
 		// Go to page 1
 		await page.goto(astro.resolveUrl('/client-only-one'));
diff --git a/packages/astro/src/runtime/client/hmr.ts b/packages/astro/src/runtime/client/hmr.ts
index 989ddc6b9..5b6eddc23 100644
--- a/packages/astro/src/runtime/client/hmr.ts
+++ b/packages/astro/src/runtime/client/hmr.ts
@@ -1,46 +1,7 @@
 /// <reference types="vite/client" />
 
 if (import.meta.hot) {
-	// Vite injects `<style data-vite-dev-id>` for ESM imports of styles
-	// but Astro also SSRs with `<style data-astro-dev-id>` blocks. This MutationObserver
-	// removes any duplicates as soon as they are hydrated client-side.
-	const injectedStyles = getInjectedStyles();
-	const mo = new MutationObserver((records) => {
-		for (const record of records) {
-			for (const node of record.addedNodes) {
-				if (isViteInjectedStyle(node)) {
-					injectedStyles.get(node.getAttribute('data-vite-dev-id')!)?.remove();
-				}
-			}
-		}
-	});
-	mo.observe(document.documentElement, { subtree: true, childList: true });
-
-	// Vue `link` styles need to be manually refreshed in Firefox
-	import.meta.hot.on('vite:beforeUpdate', async (payload) => {
-		for (const file of payload.updates) {
-			if (file.acceptedPath.includes('vue&type=style')) {
-				const link = document.querySelector(`link[href="${file.acceptedPath}"]`);
-				if (link) {
-					link.replaceWith(link.cloneNode(true));
-				}
-			}
-		}
-	});
-}
-
-function getInjectedStyles() {
-	const injectedStyles = new Map<string, Element>();
-	document.querySelectorAll<HTMLStyleElement>('style[data-astro-dev-id]').forEach((el) => {
-		injectedStyles.set(el.getAttribute('data-astro-dev-id')!, el);
-	});
-	return injectedStyles;
-}
-
-function isStyle(node: Node): node is HTMLStyleElement {
-	return node.nodeType === node.ELEMENT_NODE && (node as Element).tagName.toLowerCase() === 'style';
-}
-
-function isViteInjectedStyle(node: Node): node is HTMLStyleElement {
-	return isStyle(node) && !!node.getAttribute('data-vite-dev-id');
+	// HMR temporarily not needed for now, but kept here in case we need it again.
+	// To re-instate this module again, update `vite-plugin-astro-server/route.ts`
+	// to add this module as a script similar to `/@vite/client`
 }
diff --git a/packages/astro/src/transitions/router.ts b/packages/astro/src/transitions/router.ts
index aabba6429..12ac5615d 100644
--- a/packages/astro/src/transitions/router.ts
+++ b/packages/astro/src/transitions/router.ts
@@ -208,7 +208,7 @@ async function updateDOM(
 				const devId = el.dataset.viteDevId;
 				// If this same style tag exists, remove it from the new page
 				return (
-					newDocument.querySelector(`style[data-astro-dev-id="${devId}"]`) ||
+					newDocument.querySelector(`style[data-vite-dev-id="${devId}"]`) ||
 					// Otherwise, keep it anyways. This is client:only styles.
 					noopEl
 				);
diff --git a/packages/astro/src/vite-plugin-astro-server/css.ts b/packages/astro/src/vite-plugin-astro-server/css.ts
index 46f1235bb..d256f48c7 100644
--- a/packages/astro/src/vite-plugin-astro-server/css.ts
+++ b/packages/astro/src/vite-plugin-astro-server/css.ts
@@ -28,7 +28,7 @@ export async function getStylesForURL(
 				mode === 'development' && // only inline in development
 				typeof ssrModule?.default === 'string' // ignore JS module styles
 			) {
-				importedStylesMap.set(importedModule.url, ssrModule.default);
+				importedStylesMap.set(importedModule.id ?? importedModule.url, ssrModule.default);
 			} else {
 				// NOTE: We use the `url` property here. `id` would break Windows.
 				importedCssUrls.add(importedModule.url);
diff --git a/packages/astro/src/vite-plugin-astro-server/route.ts b/packages/astro/src/vite-plugin-astro-server/route.ts
index a567c3266..34ab119da 100644
--- a/packages/astro/src/vite-plugin-astro-server/route.ts
+++ b/packages/astro/src/vite-plugin-astro-server/route.ts
@@ -12,7 +12,7 @@ import { loadMiddleware } from '../core/middleware/loadMiddleware.js';
 import { createRenderContext, getParamsAndProps, type SSROptions } from '../core/render/index.js';
 import { createRequest } from '../core/request.js';
 import { matchAllRoutes } from '../core/routing/index.js';
-import { isPage, resolveIdToUrl, viteID } from '../core/util.js';
+import { isPage } from '../core/util.js';
 import { getSortedPreloadedMatches } from '../prerender/routing.js';
 import { isServerLikeOutput } from '../prerender/utils.js';
 import { PAGE_SCRIPT_ID } from '../vite-plugin-scripts/index.js';
@@ -275,13 +275,6 @@ async function getScriptsAndStyles({ pipeline, filePath }: GetScriptsAndStylesPa
 			props: { type: 'module', src: '/@vite/client' },
 			children: '',
 		});
-		scripts.add({
-			props: {
-				type: 'module',
-				src: await resolveIdToUrl(moduleLoader, 'astro/runtime/client/hmr.js'),
-			},
-			children: '',
-		});
 	}
 
 	// TODO: We should allow adding generic HTML elements to the head, not just scripts
@@ -322,11 +315,11 @@ async function getScriptsAndStyles({ pipeline, filePath }: GetScriptsAndStylesPa
 			},
 			children: '',
 		});
-		// But we still want to inject the styles to avoid FOUC
+		// But we still want to inject the styles to avoid FOUC. The style tags
+		// should emulate what Vite injects so further HMR works as expected.
 		styles.add({
 			props: {
-				// Track the ID so we can match it to Vite's injected style later
-				'data-astro-dev-id': viteID(new URL(`.${url}`, settings.config.root)),
+				'data-vite-dev-id': url,
 			},
 			children: content,
 		});