@@ -6,6 +6,7 @@ import emotion from '@rolldown/plugin-emotion';
 import type { StorybookConfig } from '@storybook/react-vite';
 import dsTokenFallbacks from '@wordpress/theme/postcss-plugins/postcss-ds-token-fallbacks';
 import dsTokenFallbacksJs from '@wordpress/theme/vite-plugins/vite-ds-token-fallbacks';
+import { createPostcssBrowserPlugin } from './postcss-browser-plugin.mjs';
 import { statusIndexer } from './status-indexer.js';
 
 /**
@@ -143,6 +144,15 @@ const config: StorybookConfig = {
 					},
 				],
 			},
+			optimizeDeps: {
+				rolldownOptions: {
+					plugins: [
+						createPostcssBrowserPlugin(
+							path.resolve( import.meta.dirname, '..' )
+						),
+					],
+				},
+			},
 			plugins: [
 				dsTokenFallbacksJs(),
 				react() as PluginOption,
 
@@ -7,11 +7,15 @@ const EMPTY_MODULE_ID = '\0postcss-browser-empty';
 // Temporary workaround for https://github.com/vitejs/vite/issues/23512.
 // Remove this plugin and its optimizer registration once the installed Vite
 // version handles browser:false imports without warnings. Keep the Browser
-// regression test to verify removal.
+// regression test and Storybook smoke check to verify removal.
 //
 // The separate CSS Modules missing-`from` warning is tracked in:
 // https://github.com/madyankin/postcss-modules/pull/173
 // https://github.com/vitejs/vite/issues/15410
+/**
+ * @param {string} rootDir
+ * @return {import('vite').Plugin} The PostCSS browser import resolver.
+ */
 export function createPostcssBrowserPlugin( rootDir ) {
 	const require = createRequire(
 		path.join( rootDir, 'packages/block-editor/package.json' )
@@ -35,13 +39,15 @@ export function createPostcssBrowserPlugin( rootDir ) {
 			) {
 				return EMPTY_MODULE_ID;
 			}
+			return null;
 		},
 		load( id ) {
 			if ( id === EMPTY_MODULE_ID ) {
 				// PostCSS probes these optional APIs. Honor its browser:false
 				// mappings without Vite's warning-producing external proxies.
 				return 'module.exports = {};';
 			}
+			return null;
 		},
 	};
 }
@@ -6,7 +6,7 @@ import { defineConfig } from 'vitest/config';
 import { createVitePlugins } from './config/vite-plugins.mjs';
 import { createPlaywrightProvider } from './config/playwright-provider.mjs';
 import { createBrowserTraceArtifacts } from './config/browser-traces.mjs';
-import { createPostcssBrowserPlugin } from './config/postcss-browser-plugin.mjs';
+import { createPostcssBrowserPlugin } from '../../storybook/postcss-browser-plugin.mjs';
 import {
 	discoverTestFiles,
 	getVitestTestsByProject,