diff --git a/.changeset/warn-vite8-cloudflare-override.md b/.changeset/warn-vite8-cloudflare-override.md
new file mode 100644
index 000000000000..2b6f183fad9f
--- /dev/null
+++ b/.changeset/warn-vite8-cloudflare-override.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Warns on dev server startup when Vite 8 is detected at the top level of the user's project, and automatically adds a `"overrides": { "vite": "^7" }` entry to `package.json` when running `astro add cloudflare`. This prevents a `require_dist is not a function` crash caused by a Vite version split between Astro (requires Vite 7) and packages like `@tailwindcss/vite` that hoist Vite 8.
diff --git a/packages/astro/src/cli/add/index.ts b/packages/astro/src/cli/add/index.ts
index 1b48674cbc5d..0674933c7a36 100644
--- a/packages/astro/src/cli/add/index.ts
+++ b/packages/astro/src/cli/add/index.ts
@@ -246,6 +246,13 @@ export async function add(names: string[], { flags }: AddOptions) {
 					logger,
 					scripts: { 'generate-types': 'wrangler types' },
 				});
+
+				await updatePackageJsonOverrides({
+					configURL,
+					flags,
+					logger,
+					overrides: { vite: '^7' },
+				});
 			}
 			if (integrations.find((integration) => integration.id === 'tailwind')) {
 				const dir = new URL('./styles/', new URL(userConfig.srcDir ?? './src/', root));
@@ -715,6 +722,67 @@ async function updateAstroConfig({
 	}
 }
 
+async function updatePackageJsonOverrides({
+	configURL,
+	flags,
+	logger,
+	overrides,
+}: {
+	configURL: URL;
+	flags: Flags;
+	logger: Logger;
+	overrides: Record<string, string>;
+}): Promise<UpdateResult> {
+	const pkgURL = new URL('./package.json', configURL);
+	if (!existsSync(pkgURL)) {
+		logger.debug('add', 'No package.json found, skipping overrides update');
+		return UpdateResult.none;
+	}
+
+	const pkgPath = fileURLToPath(pkgURL);
+	const input = await fs.readFile(pkgPath, { encoding: 'utf-8' });
+	const pkgJson = JSON.parse(input);
+
+	pkgJson.overrides ??= {};
+	let hasChanges = false;
+	for (const [name, range] of Object.entries(overrides)) {
+		if (!(name in pkgJson.overrides)) {
+			pkgJson.overrides[name] = range;
+			hasChanges = true;
+		}
+	}
+
+	if (!hasChanges) {
+		return UpdateResult.none;
+	}
+
+	const output = JSON.stringify(pkgJson, null, 2);
+	const diff = getDiffContent(input, output);
+
+	if (!diff) {
+		return UpdateResult.none;
+	}
+
+	logger.info(
+		'SKIP_FORMAT',
+		`\n  ${magenta('Astro will add the following overrides to your package.json:')}`,
+	);
+
+	clack.box(diff, 'package.json', {
+		rounded: true,
+		withGuide: false,
+		width: 'auto',
+	});
+
+	if (await askToContinue({ flags, logger })) {
+		await fs.writeFile(pkgPath, output, { encoding: 'utf-8' });
+		logger.debug('add', 'Updated package.json overrides');
+		return UpdateResult.updated;
+	} else {
+		return UpdateResult.cancelled;
+	}
+}
+
 async function updatePackageJsonScripts({
 	configURL,
 	flags,
diff --git a/packages/astro/src/core/dev/dev.ts b/packages/astro/src/core/dev/dev.ts
index 36ffb1fcbb04..7ed92db0b13a 100644
--- a/packages/astro/src/core/dev/dev.ts
+++ b/packages/astro/src/core/dev/dev.ts
@@ -1,5 +1,6 @@
 import fs from 'node:fs';
 import type http from 'node:http';
+import { createRequire } from 'node:module';
 import type { AddressInfo } from 'node:net';
 import { performance } from 'node:perf_hooks';
 import colors from 'piccolore';
@@ -24,6 +25,19 @@ import {
 } from './update-check.js';
 import { BuildTimeAstroVersionProvider } from '../../cli/infra/build-time-astro-version-provider.js';
 import { piccoloreTextStyler } from '../../cli/infra/piccolore-text-styler.js';
+import type { Logger } from '../logger/core.js';
+
+function warnIfVite8({ root, logger }: { root: URL | string; logger: Logger }) {
+	try {
+		const require = createRequire(root);
+		const { version } = require('vite/package.json') as { version: string };
+		if (major(version) >= 8) {
+			logger.warn('SKIP_FORMAT', msg.vite8Warning({ viteVersion: version }));
+		}
+	} catch {
+		// If vite can't be resolved from the project root, skip the warning
+	}
+}
 
 export interface DevServer {
 	address: AddressInfo;
@@ -140,6 +154,8 @@ export default async function dev(inlineConfig: AstroInlineConfig): Promise<DevS
 		logger.warn('SKIP_FORMAT', msg.fsStrictWarning());
 	}
 
+	setImmediate(() => warnIfVite8({ root: restart.container.settings.config.root, logger }));
+
 	logger.info(null, colors.green('watching for file changes...'));
 
 	return {
diff --git a/packages/astro/src/core/messages/runtime.ts b/packages/astro/src/core/messages/runtime.ts
index 115c1fb5e780..f83062426916 100644
--- a/packages/astro/src/core/messages/runtime.ts
+++ b/packages/astro/src/core/messages/runtime.ts
@@ -179,6 +179,12 @@ export function fsStrictWarning() {
 	return `${title}\n${subtitle}\n`;
 }
 
+export function vite8Warning({ viteVersion }: { viteVersion: string }) {
+	const title = yellow('▶ ' + `Vite ${bold(viteVersion)} detected in your project.`);
+	const subtitle = `  Astro requires Vite 7. Add ${bold('"overrides": { "vite": "^7" }')} to your ${bold('package.json')} to avoid issues.`;
+	return `${title}\n${subtitle}\n`;
+}
+
 export function prerelease({ currentVersion }: { currentVersion: string }) {
 	const tag = currentVersion.split('-').slice(1).join('-').replace(/\..*$/, '') || 'unknown';
 	const badge = bgYellow(black(` ${tag} `));