diff --git a/code/addons/vitest/src/vitest-plugin/index.ts b/code/addons/vitest/src/vitest-plugin/index.ts
index 4d4981797291..c3e28d4ed781 100644
--- a/code/addons/vitest/src/vitest-plugin/index.ts
+++ b/code/addons/vitest/src/vitest-plugin/index.ts
@@ -24,7 +24,7 @@ import { oneWayHash } from 'storybook/internal/telemetry';
 import type { Presets } from 'storybook/internal/types';
 
 import { match } from 'micromatch';
-import { dirname, join, normalize, relative, resolve, sep } from 'pathe';
+import { join, normalize, relative, resolve, sep } from 'pathe';
 import picocolors from 'picocolors';
 import sirv from 'sirv';
 import { dedent } from 'ts-dedent';
diff --git a/code/builders/builder-vite/build-config.ts b/code/builders/builder-vite/build-config.ts
index 60918f8f8eb0..f6bc2c790c0f 100644
--- a/code/builders/builder-vite/build-config.ts
+++ b/code/builders/builder-vite/build-config.ts
@@ -7,6 +7,11 @@ const config: BuildEntries = {
         exportEntries: ['.'],
         entryPoint: './src/index.ts',
       },
+      {
+        exportEntries: ['./preset'],
+        entryPoint: './src/preset.ts',
+        dts: false,
+      },
     ],
   },
   extraOutputs: {
diff --git a/code/builders/builder-vite/package.json b/code/builders/builder-vite/package.json
index 4d3c1f0cf526..f010719527f2 100644
--- a/code/builders/builder-vite/package.json
+++ b/code/builders/builder-vite/package.json
@@ -33,7 +33,8 @@
       "default": "./dist/index.js"
     },
     "./input/iframe.html": "./input/iframe.html",
-    "./package.json": "./package.json"
+    "./package.json": "./package.json",
+    "./preset": "./dist/preset.js"
   },
   "files": [
     "dist/**/*",
@@ -41,6 +42,7 @@
     "README.md",
     "*.js",
     "*.d.ts",
+    "preset.js",
     "!src/**/*"
   ],
   "scripts": {
@@ -49,6 +51,7 @@
   },
   "dependencies": {
     "@storybook/csf-plugin": "workspace:*",
+    "@vitest/mocker": "3.2.4",
     "ts-dedent": "^2.0.0"
   },
   "devDependencies": {
diff --git a/code/builders/builder-vite/preset.js b/code/builders/builder-vite/preset.js
new file mode 100644
index 000000000000..4bd63d324002
--- /dev/null
+++ b/code/builders/builder-vite/preset.js
@@ -0,0 +1 @@
+export * from './dist/preset.js';
diff --git a/code/builders/builder-vite/src/index.ts b/code/builders/builder-vite/src/index.ts
index ff91de398583..557b162630d6 100644
--- a/code/builders/builder-vite/src/index.ts
+++ b/code/builders/builder-vite/src/index.ts
@@ -63,3 +63,5 @@ export const start: ViteBuilder['start'] = async ({
 export const build: ViteBuilder['build'] = async ({ options }) => {
   return viteBuild(options as Options);
 };
+
+export const corePresets = [import.meta.resolve('@storybook/builder-vite/preset')];
diff --git a/code/core/src/core-server/presets/vitePlugins/vite-inject-mocker/plugin.ts b/code/builders/builder-vite/src/plugins/vite-inject-mocker/plugin.ts
similarity index 97%
rename from code/core/src/core-server/presets/vitePlugins/vite-inject-mocker/plugin.ts
rename to code/builders/builder-vite/src/plugins/vite-inject-mocker/plugin.ts
index ec468cf21d3e..8937c9a33bce 100644
--- a/code/core/src/core-server/presets/vitePlugins/vite-inject-mocker/plugin.ts
+++ b/code/builders/builder-vite/src/plugins/vite-inject-mocker/plugin.ts
@@ -2,12 +2,12 @@ import { readFileSync } from 'node:fs';
 import { join } from 'node:path';
 import { fileURLToPath } from 'node:url';
 
+import { resolvePackageDir } from 'storybook/internal/common';
+
 import { exactRegex } from '@rolldown/pluginutils';
 import { dedent } from 'ts-dedent';
 import type { ResolvedConfig, ViteDevServer } from 'vite';
 
-import { resolvePackageDir } from '../../../../shared/utils/module';
-
 const entryPath = '/vite-inject-mocker-entry.js';
 
 const entryCode = dedent`
diff --git a/code/core/src/core-server/presets/vitePlugins/vite-mock/plugin.ts b/code/builders/builder-vite/src/plugins/vite-mock/plugin.ts
similarity index 96%
rename from code/core/src/core-server/presets/vitePlugins/vite-mock/plugin.ts
rename to code/builders/builder-vite/src/plugins/vite-mock/plugin.ts
index 57d06762d2a9..23861a121259 100644
--- a/code/core/src/core-server/presets/vitePlugins/vite-mock/plugin.ts
+++ b/code/builders/builder-vite/src/plugins/vite-mock/plugin.ts
@@ -1,18 +1,19 @@
 import { readFileSync } from 'node:fs';
 
+import {
+  babelParser,
+  extractMockCalls,
+  getAutomockCode,
+  getRealPath,
+  rewriteSbMockImportCalls,
+} from 'storybook/internal/mocking-utils';
 import { logger } from 'storybook/internal/node-logger';
 import type { CoreConfig } from 'storybook/internal/types';
 
+import { findMockRedirect } from '@vitest/mocker/redirect';
 import { normalize } from 'pathe';
 import type { Plugin, ResolvedConfig } from 'vite';
 
-import { getAutomockCode } from '../../../mocking-utils/automock';
-import {
-  babelParser,
-  extractMockCalls,
-  rewriteSbMockImportCalls,
-} from '../../../mocking-utils/extract';
-import { getRealPath } from '../../../mocking-utils/resolve';
 import { type MockCall, getCleanId, invalidateAllRelatedModules } from './utils';
 
 export interface MockPluginOptions {
@@ -55,7 +56,7 @@ export function viteMockPlugin(options: MockPluginOptions): Plugin[] {
       },
 
       buildStart() {
-        mockCalls = extractMockCalls(options, babelParser, viteConfig.root);
+        mockCalls = extractMockCalls(options, babelParser, viteConfig.root, findMockRedirect);
       },
 
       configureServer(server) {
@@ -64,7 +65,7 @@ export function viteMockPlugin(options: MockPluginOptions): Plugin[] {
             // Store the old mocks before updating
             const oldMockCalls = mockCalls;
             // Re-extract mocks to get the latest list
-            mockCalls = extractMockCalls(options, babelParser, viteConfig.root);
+            mockCalls = extractMockCalls(options, babelParser, viteConfig.root, findMockRedirect);
 
             // Invalidate the preview file
             const previewMod = server.moduleGraph.getModuleById(options.previewConfigPath);
diff --git a/code/core/src/core-server/presets/vitePlugins/vite-mock/utils.ts b/code/builders/builder-vite/src/plugins/vite-mock/utils.ts
similarity index 96%
rename from code/core/src/core-server/presets/vitePlugins/vite-mock/utils.ts
rename to code/builders/builder-vite/src/plugins/vite-mock/utils.ts
index d3d1de0d4bcf..6f582b9570cd 100644
--- a/code/core/src/core-server/presets/vitePlugins/vite-mock/utils.ts
+++ b/code/builders/builder-vite/src/plugins/vite-mock/utils.ts
@@ -1,4 +1,3 @@
-import { realpathSync } from 'fs';
 import type { ViteDevServer } from 'vite';
 
 /**
diff --git a/code/builders/builder-vite/src/preset.ts b/code/builders/builder-vite/src/preset.ts
new file mode 100644
index 000000000000..b309970c3314
--- /dev/null
+++ b/code/builders/builder-vite/src/preset.ts
@@ -0,0 +1,34 @@
+import { findConfigFile } from 'storybook/internal/common';
+import type { Options } from 'storybook/internal/types';
+
+import type { UserConfig } from 'vite';
+
+import { viteInjectMockerRuntime } from './plugins/vite-inject-mocker/plugin';
+import { viteMockPlugin } from './plugins/vite-mock/plugin';
+
+// This preset defines currently mocking plugins for Vite
+// It is defined as a viteFinal preset so that @storybook/addon-vitest can use it as well and that it doesn't have to be duplicated in addon-vitest.
+// The main vite configuration is defined in `./vite-config.ts`.
+export async function viteFinal(existing: UserConfig, options: Options) {
+  const previewConfigPath = findConfigFile('preview', options.configDir);
+
+  // If there's no preview file, there's nothing to mock.
+  if (!previewConfigPath) {
+    return existing;
+  }
+
+  const coreOptions = await options.presets.apply('core');
+
+  return {
+    ...existing,
+    plugins: [
+      ...(existing.plugins ?? []),
+      ...(previewConfigPath
+        ? [
+            viteInjectMockerRuntime({ previewConfigPath }),
+            viteMockPlugin({ previewConfigPath, coreOptions, configDir: options.configDir }),
+          ]
+        : []),
+    ],
+  };
+}
diff --git a/code/builders/builder-vite/src/vite-config.ts b/code/builders/builder-vite/src/vite-config.ts
index 50852eb307c9..9cb4e86042f2 100644
--- a/code/builders/builder-vite/src/vite-config.ts
+++ b/code/builders/builder-vite/src/vite-config.ts
@@ -58,6 +58,8 @@ export async function commonConfig(
   const { config: { build: buildProperty = undefined, ...userConfig } = {} } =
     (await loadConfigFromFile(configEnv, viteConfigPath, projectRoot)) ?? {};
 
+  // This is the main Vite config that is used by Storybook.
+  // Some shared vite plugins are defined in the `./preset.ts` file so that it can be shared between the @storybook/builder-vite and @storybook/addon-vitest package.
   const sbConfig: InlineConfig = {
     configFile: false,
     cacheDir: resolvePathInStorybookCache('sb-vite', options.cacheKey),
diff --git a/code/builders/builder-webpack5/build-config.ts b/code/builders/builder-webpack5/build-config.ts
index cd2d4bb30ccf..64d45a5ebec4 100644
--- a/code/builders/builder-webpack5/build-config.ts
+++ b/code/builders/builder-webpack5/build-config.ts
@@ -22,6 +22,16 @@ const config: BuildEntries = {
         entryPoint: './src/loaders/export-order-loader.ts',
         dts: false,
       },
+      {
+        exportEntries: ['./loaders/storybook-mock-transform-loader'],
+        entryPoint: './src/loaders/storybook-mock-transform-loader.ts',
+        dts: false,
+      },
+      {
+        exportEntries: ['./loaders/webpack-automock-loader'],
+        entryPoint: './src/loaders/webpack-automock-loader.ts',
+        dts: false,
+      },
     ],
   },
   extraOutputs: {
diff --git a/code/builders/builder-webpack5/package.json b/code/builders/builder-webpack5/package.json
index 8bacb3bba793..6d580a1d53fb 100644
--- a/code/builders/builder-webpack5/package.json
+++ b/code/builders/builder-webpack5/package.json
@@ -32,6 +32,8 @@
       "default": "./dist/index.js"
     },
     "./loaders/export-order-loader": "./dist/loaders/export-order-loader.js",
+    "./loaders/storybook-mock-transform-loader": "./dist/loaders/storybook-mock-transform-loader.js",
+    "./loaders/webpack-automock-loader": "./dist/loaders/webpack-automock-loader.js",
     "./package.json": "./package.json",
     "./presets/custom-webpack-preset": "./dist/presets/custom-webpack-preset.js",
     "./presets/preview-preset": "./dist/presets/preview-preset.js",
@@ -54,6 +56,7 @@
   },
   "dependencies": {
     "@storybook/core-webpack": "workspace:*",
+    "@vitest/mocker": "3.2.4",
     "case-sensitive-paths-webpack-plugin": "^2.4.0",
     "cjs-module-lexer": "^1.2.3",
     "css-loader": "^7.1.2",
diff --git a/code/core/src/core-server/presets/webpack/loaders/storybook-mock-transform-loader.ts b/code/builders/builder-webpack5/src/loaders/storybook-mock-transform-loader.ts
similarity index 91%
rename from code/core/src/core-server/presets/webpack/loaders/storybook-mock-transform-loader.ts
rename to code/builders/builder-webpack5/src/loaders/storybook-mock-transform-loader.ts
index 2da83caa09e7..ebc0aa6c402b 100644
--- a/code/core/src/core-server/presets/webpack/loaders/storybook-mock-transform-loader.ts
+++ b/code/builders/builder-webpack5/src/loaders/storybook-mock-transform-loader.ts
@@ -1,9 +1,8 @@
+import { rewriteSbMockImportCalls } from 'storybook/internal/mocking-utils';
 import { logger } from 'storybook/internal/node-logger';
 
 import type { LoaderDefinition } from 'webpack';
 
-import { rewriteSbMockImportCalls } from '../../../mocking-utils/extract';
-
 /**
  * A Webpack loader that normalize sb.mock(import(...)) calls to sb.mock(...)
  *
diff --git a/code/core/src/core-server/presets/webpack/loaders/webpack-automock-loader.ts b/code/builders/builder-webpack5/src/loaders/webpack-automock-loader.ts
similarity index 91%
rename from code/core/src/core-server/presets/webpack/loaders/webpack-automock-loader.ts
rename to code/builders/builder-webpack5/src/loaders/webpack-automock-loader.ts
index 980be6eb4018..8fa9d7dfb952 100644
--- a/code/core/src/core-server/presets/webpack/loaders/webpack-automock-loader.ts
+++ b/code/builders/builder-webpack5/src/loaders/webpack-automock-loader.ts
@@ -1,7 +1,6 @@
-import type { LoaderContext } from 'webpack';
+import { babelParser, getAutomockCode } from 'storybook/internal/mocking-utils';
 
-import { getAutomockCode } from '../../../mocking-utils/automock';
-import { babelParser } from '../../../mocking-utils/extract';
+import type { LoaderContext } from 'webpack';
 
 /** Defines the options that can be passed to the webpack-automock-loader. */
 interface AutomockLoaderOptions {
diff --git a/code/core/src/core-server/presets/webpack/plugins/webpack-inject-mocker-runtime-plugin.ts b/code/builders/builder-webpack5/src/plugins/webpack-inject-mocker-runtime-plugin.ts
similarity index 72%
rename from code/core/src/core-server/presets/webpack/plugins/webpack-inject-mocker-runtime-plugin.ts
rename to code/builders/builder-webpack5/src/plugins/webpack-inject-mocker-runtime-plugin.ts
index efcccf2f4f95..da843d1cd782 100644
--- a/code/core/src/core-server/presets/webpack/plugins/webpack-inject-mocker-runtime-plugin.ts
+++ b/code/builders/builder-webpack5/src/plugins/webpack-inject-mocker-runtime-plugin.ts
@@ -1,13 +1,10 @@
-import { join } from 'node:path';
+import { getMockerRuntime } from 'storybook/internal/mocking-utils';
 
-import { buildSync } from 'esbuild';
 // HtmlWebpackPlugin is a standard part of Storybook's Webpack setup.
 // We can assume it's available as a dependency.
 import type HtmlWebpackPlugin from 'html-webpack-plugin';
 import type { Compiler } from 'webpack';
 
-import { resolvePackageDir } from '../../../../shared/utils/module';
-
 const PLUGIN_NAME = 'WebpackInjectMockerRuntimePlugin';
 
 /**
@@ -55,26 +52,7 @@ export class WebpackInjectMockerRuntimePlugin {
         PLUGIN_NAME,
         (data, cb) => {
           try {
-            // The runtime template is the same for both dev and build in the final implementation,
-            // as all mocking logic is handled at build time or by the dev server's transform.
-            const runtimeTemplatePath = join(
-              resolvePackageDir('storybook'),
-              'assets',
-              'server',
-              'mocker-runtime.template.js'
-            );
-            // Use esbuild to bundle the runtime script and its dependencies (`@vitest/mocker`, etc.)
-            // into a single, self-contained string of code.
-            const bundleResult = buildSync({
-              entryPoints: [runtimeTemplatePath],
-              bundle: true,
-              write: false, // Return the result in memory instead of writing to disk
-              format: 'esm',
-              target: 'es2020',
-              external: ['msw/browser', 'msw/core/http'],
-            });
-
-            const runtimeScriptContent = bundleResult.outputFiles[0].text;
+            const runtimeScriptContent = getMockerRuntime();
             const runtimeAssetName = 'mocker-runtime-injected.js';
 
             // Use the documented `emitAsset` method to add the pre-bundled runtime script
diff --git a/code/core/src/core-server/presets/webpack/plugins/webpack-mock-plugin.ts b/code/builders/builder-webpack5/src/plugins/webpack-mock-plugin.ts
similarity index 94%
rename from code/core/src/core-server/presets/webpack/plugins/webpack-mock-plugin.ts
rename to code/builders/builder-webpack5/src/plugins/webpack-mock-plugin.ts
index 6bb87d340fc1..7a3f4b8f2dfe 100644
--- a/code/core/src/core-server/presets/webpack/plugins/webpack-mock-plugin.ts
+++ b/code/builders/builder-webpack5/src/plugins/webpack-mock-plugin.ts
@@ -1,17 +1,16 @@
-import { createRequire } from 'node:module';
 import { dirname, isAbsolute } from 'node:path';
 import { fileURLToPath } from 'node:url';
 
-import type { Compiler } from 'webpack';
-
-import { babelParser, extractMockCalls } from '../../../mocking-utils/extract';
 import {
+  babelParser,
+  extractMockCalls,
   getIsExternal,
   resolveExternalModule,
   resolveWithExtensions,
-} from '../../../mocking-utils/resolve';
+} from 'storybook/internal/mocking-utils';
 
-const require = createRequire(import.meta.url);
+import { findMockRedirect } from '@vitest/mocker/redirect';
+import type { Compiler } from 'webpack';
 
 // --- Type Definitions ---
 
@@ -131,7 +130,8 @@ export class WebpackMockPlugin {
     const mocks = extractMockCalls(
       { previewConfigPath, configDir: dirname(previewConfigPath) },
       babelParser,
-      compiler.context
+      compiler.context,
+      findMockRedirect
     );
 
     // 2. Resolve each mock call to its absolute path and replacement resource.
@@ -148,7 +148,7 @@ export class WebpackMockPlugin {
         } else {
           // No `__mocks__` file found. Use our custom loader to automock the module.
           const loaderPath = fileURLToPath(
-            import.meta.resolve('storybook/webpack/loaders/webpack-automock-loader')
+            import.meta.resolve('@storybook/builder-webpack5/loaders/webpack-automock-loader')
           );
           replacementResource = `${loaderPath}?spy=${mock.spy}!${absolutePath}`;
         }
diff --git a/code/builders/builder-webpack5/src/presets/custom-webpack-preset.ts b/code/builders/builder-webpack5/src/presets/custom-webpack-preset.ts
index 8cb3b7ba3d21..20947f59e5a9 100644
--- a/code/builders/builder-webpack5/src/presets/custom-webpack-preset.ts
+++ b/code/builders/builder-webpack5/src/presets/custom-webpack-preset.ts
@@ -1,3 +1,6 @@
+import { fileURLToPath } from 'node:url';
+
+import { findConfigFile } from 'storybook/internal/common';
 import { logger } from 'storybook/internal/node-logger';
 import type { Options, PresetProperty } from 'storybook/internal/types';
 
@@ -6,6 +9,8 @@ import { loadCustomWebpackConfig } from '@storybook/core-webpack';
 import webpackModule from 'webpack';
 import type { Configuration } from 'webpack';
 
+import { WebpackInjectMockerRuntimePlugin } from '../plugins/webpack-inject-mocker-runtime-plugin';
+import { WebpackMockPlugin } from '../plugins/webpack-mock-plugin';
 import { createDefaultWebpackConfig } from '../preview/base-webpack.config';
 
 export const swc: PresetProperty<'swc'> = (config: Record<string, any>): Record<string, any> => {
@@ -26,6 +31,38 @@ export const swc: PresetProperty<'swc'> = (config: Record<string, any>): Record<
   };
 };
 
+export async function webpackFinal(config: Configuration, options: Options) {
+  const previewConfigPath = findConfigFile('preview', options.configDir);
+
+  // If there's no preview file, there's nothing to mock.
+  if (!previewConfigPath) {
+    return config;
+  }
+
+  config.plugins = config.plugins || [];
+
+  // 1. Add the loader to normalize sb.mock(import(...)) calls.
+  config.module!.rules!.push({
+    test: /preview\.(t|j)sx?$/,
+    use: [
+      {
+        loader: fileURLToPath(
+          import.meta.resolve('@storybook/builder-webpack5/loaders/storybook-mock-transform-loader')
+        ),
+      },
+    ],
+  });
+
+  // 2. Add the plugin to handle module replacement based on sb.mock() calls.
+  // This plugin scans the preview file and sets up rules to swap modules.
+  config.plugins.push(new WebpackMockPlugin({ previewConfigPath }));
+
+  // 3. Add the plugin to inject the mocker runtime script into the HTML.
+  // This ensures the `sb` object is available before any other code runs.
+  config.plugins.push(new WebpackInjectMockerRuntimePlugin());
+  return config;
+}
+
 export async function webpack(config: Configuration, options: Options) {
   const { configDir, configType, presets } = options;
 
diff --git a/code/core/build-config.ts b/code/core/build-config.ts
index 20552490d75c..3912a937d994 100644
--- a/code/core/build-config.ts
+++ b/code/core/build-config.ts
@@ -77,14 +77,8 @@ const config: BuildEntries = {
         exportEntries: ['./internal/cli'],
       },
       {
-        entryPoint: './src/core-server/presets/webpack/loaders/webpack-automock-loader.ts',
-        exportEntries: ['./webpack/loaders/webpack-automock-loader'],
-        dts: false,
-      },
-      {
-        entryPoint: './src/core-server/presets/webpack/loaders/storybook-mock-transform-loader.ts',
-        exportEntries: ['./webpack/loaders/storybook-mock-transform-loader'],
-        dts: false,
+        exportEntries: ['./internal/mocking-utils'],
+        entryPoint: './src/mocking-utils/index.ts',
       },
     ],
     browser: [
diff --git a/code/core/package.json b/code/core/package.json
index 8c9e1f2fe2a5..f165c07cc143 100644
--- a/code/core/package.json
+++ b/code/core/package.json
@@ -118,6 +118,10 @@
       "default": "./dist/manager/globals.js"
     },
     "./internal/manager/globals-runtime": "./dist/manager/globals-runtime.js",
+    "./internal/mocking-utils": {
+      "types": "./dist/mocking-utils/index.d.ts",
+      "default": "./dist/mocking-utils/index.js"
+    },
     "./internal/node-logger": {
       "types": "./dist/node-logger/index.d.ts",
       "default": "./dist/node-logger/index.js"
@@ -175,9 +179,7 @@
     "./viewport": {
       "types": "./dist/viewport/index.d.ts",
       "default": "./dist/viewport/index.js"
-    },
-    "./webpack/loaders/storybook-mock-transform-loader": "./dist/core-server/presets/webpack/loaders/storybook-mock-transform-loader.js",
-    "./webpack/loaders/webpack-automock-loader": "./dist/core-server/presets/webpack/loaders/webpack-automock-loader.js"
+    }
   },
   "bin": "./dist/bin/dispatcher.js",
   "files": [
@@ -200,7 +202,6 @@
     "@testing-library/jest-dom": "^6.6.3",
     "@testing-library/user-event": "^14.6.1",
     "@vitest/expect": "3.2.4",
-    "@vitest/mocker": "3.2.4",
     "@vitest/spy": "3.2.4",
     "esbuild": "^0.18.0 || ^0.19.0 || ^0.20.0 || ^0.21.0 || ^0.22.0 || ^0.23.0 || ^0.24.0 || ^0.25.0",
     "recast": "^0.23.5",
diff --git a/code/core/src/core-server/load.ts b/code/core/src/core-server/load.ts
index 0217913fd4d8..ed24fc349d9d 100644
--- a/code/core/src/core-server/load.ts
+++ b/code/core/src/core-server/load.ts
@@ -1,9 +1,8 @@
 import {
   getProjectRoot,
+  getStorybookInfo,
   loadAllPresets,
-  loadMainConfig,
   resolveAddonName,
-  validateFrameworkName,
 } from 'storybook/internal/common';
 import { oneWayHash } from 'storybook/internal/telemetry';
 import type { BuilderOptions, CLIOptions, LoadOptions, Options } from 'storybook/internal/types';
@@ -30,19 +29,17 @@ export async function loadStorybook(
   options.configDir = configDir;
   options.cacheKey = cacheKey;
 
-  const config = await loadMainConfig(options);
-  const { framework } = config;
   const corePresets = [];
 
-  let frameworkName = typeof framework === 'string' ? framework : framework?.name;
-  if (!options.ignorePreview) {
-    validateFrameworkName(frameworkName);
-  }
-  if (frameworkName) {
-    corePresets.push(join(frameworkName, 'preset'));
+  const { frameworkPackage, builderPackage } = await getStorybookInfo(configDir);
+
+  if (frameworkPackage) {
+    corePresets.push(join(frameworkPackage, 'preset'));
   }
 
-  frameworkName = frameworkName || 'custom';
+  if (builderPackage) {
+    corePresets.push(join(builderPackage, 'preset'));
+  }
 
   // Load first pass: We need to determine the builder
   // We need to do this because builders might introduce 'overridePresets' which we need to take into account
diff --git a/code/core/src/core-server/presets/common-preset.ts b/code/core/src/core-server/presets/common-preset.ts
index 63c11d689faa..976dad85adca 100644
--- a/code/core/src/core-server/presets/common-preset.ts
+++ b/code/core/src/core-server/presets/common-preset.ts
@@ -1,13 +1,11 @@
 import { existsSync } from 'node:fs';
 import { readFile } from 'node:fs/promises';
-import { fileURLToPath } from 'node:url';
 
 import type { Channel } from 'storybook/internal/channels';
 import { optionalEnvToBoolean } from 'storybook/internal/common';
 import {
   JsPackageManagerFactory,
   type RemoveAddonOptions,
-  findConfigFile,
   getDirectoryFromWorkingDir,
   getPreviewBodyTemplate,
   getPreviewHeadTemplate,
@@ -288,73 +286,3 @@ export const managerEntries = async (existing: any) => {
     ...(existing || []),
   ];
 };
-
-export const viteFinal = async (
-  existing: import('vite').UserConfig,
-  options: Options
-): Promise<import('vite').UserConfig> => {
-  const previewConfigPath = findConfigFile('preview', options.configDir);
-
-  // If there's no preview file, there's nothing to mock.
-  if (!previewConfigPath) {
-    return existing;
-  }
-
-  const { viteInjectMockerRuntime } = await import('./vitePlugins/vite-inject-mocker/plugin');
-  const { viteMockPlugin } = await import('./vitePlugins/vite-mock/plugin');
-  const coreOptions = await options.presets.apply('core');
-
-  return {
-    ...existing,
-    plugins: [
-      ...(existing.plugins ?? []),
-      ...(previewConfigPath
-        ? [
-            viteInjectMockerRuntime({ previewConfigPath }),
-            viteMockPlugin({ previewConfigPath, coreOptions, configDir: options.configDir }),
-          ]
-        : []),
-    ],
-  };
-};
-
-export const webpackFinal = async (
-  config: import('webpack').Configuration,
-  options: Options
-): Promise<import('webpack').Configuration> => {
-  const previewConfigPath = findConfigFile('preview', options.configDir);
-
-  // If there's no preview file, there's nothing to mock.
-  if (!previewConfigPath) {
-    return config;
-  }
-
-  const { WebpackMockPlugin } = await import('./webpack/plugins/webpack-mock-plugin');
-  const { WebpackInjectMockerRuntimePlugin } = await import(
-    './webpack/plugins/webpack-inject-mocker-runtime-plugin'
-  );
-
-  config.plugins = config.plugins || [];
-
-  // 1. Add the loader to normalize sb.mock(import(...)) calls.
-  config.module!.rules!.push({
-    test: /preview\.(t|j)sx?$/,
-    use: [
-      {
-        loader: fileURLToPath(
-          import.meta.resolve('storybook/webpack/loaders/storybook-mock-transform-loader')
-        ),
-      },
-    ],
-  });
-
-  // 2. Add the plugin to handle module replacement based on sb.mock() calls.
-  // This plugin scans the preview file and sets up rules to swap modules.
-  config.plugins.push(new WebpackMockPlugin({ previewConfigPath }));
-
-  // 3. Add the plugin to inject the mocker runtime script into the HTML.
-  // This ensures the `sb` object is available before any other code runs.
-  config.plugins.push(new WebpackInjectMockerRuntimePlugin());
-
-  return config;
-};
diff --git a/code/core/src/core-server/presets/vitePlugins/vite-inject-mocker/constants.ts b/code/core/src/core-server/presets/vitePlugins/vite-inject-mocker/constants.ts
deleted file mode 100644
index cff1849840b7..000000000000
--- a/code/core/src/core-server/presets/vitePlugins/vite-inject-mocker/constants.ts
+++ /dev/null
@@ -1 +0,0 @@
-export const __STORYBOOK_GLOBAL_THIS_ACCESSOR__ = '__vitest_mocker__';
diff --git a/code/core/src/core-server/mocking-utils/automock.ts b/code/core/src/mocking-utils/automock.ts
similarity index 97%
rename from code/core/src/core-server/mocking-utils/automock.ts
rename to code/core/src/mocking-utils/automock.ts
index b1df00327a51..aac315198c81 100644
--- a/code/core/src/core-server/mocking-utils/automock.ts
+++ b/code/core/src/mocking-utils/automock.ts
@@ -8,11 +8,12 @@ import type {
 } from 'estree';
 import MagicString from 'magic-string';
 
-import { __STORYBOOK_GLOBAL_THIS_ACCESSOR__ } from '../presets/vitePlugins/vite-inject-mocker/constants';
 import { type Positioned, getArbitraryModuleIdentifier } from './esmWalker';
 
 type ParseFn = (code: string) => Program;
 
+export const __STORYBOOK_GLOBAL_THIS_ACCESSOR__ = '__vitest_mocker__';
+
 export function getAutomockCode(originalCode: string, isSpy: boolean, parse: ParseFn) {
   const mocked = automockModule(originalCode, isSpy ? 'autospy' : 'automock', parse, {
     globalThisAccessor: JSON.stringify(__STORYBOOK_GLOBAL_THIS_ACCESSOR__),
@@ -49,7 +50,8 @@ export function automockModule(
   parse: (code: string) => any,
   options: any = {}
 ): MagicString {
-  const globalThisAccessor = options.globalThisAccessor || '"__vitest_mocker__"';
+  const globalThisAccessor =
+    options.globalThisAccessor || JSON.stringify(__STORYBOOK_GLOBAL_THIS_ACCESSOR__);
   const ast = parse(code) as Program;
 
   const m = new MagicString(code);
diff --git a/code/core/src/core-server/mocking-utils/esmWalker.ts b/code/core/src/mocking-utils/esmWalker.ts
similarity index 100%
rename from code/core/src/core-server/mocking-utils/esmWalker.ts
rename to code/core/src/mocking-utils/esmWalker.ts
diff --git a/code/core/src/core-server/mocking-utils/extract.test.ts b/code/core/src/mocking-utils/extract.test.ts
similarity index 84%
rename from code/core/src/core-server/mocking-utils/extract.test.ts
rename to code/core/src/mocking-utils/extract.test.ts
index 8c0b8a8c4a32..be33590d426c 100644
--- a/code/core/src/core-server/mocking-utils/extract.test.ts
+++ b/code/core/src/mocking-utils/extract.test.ts
@@ -16,17 +16,22 @@ vi.mock('fs', async () => {
 
 vi.mock('./resolve', async () => {
   return {
-    resolveMock: vi.fn((path) => {
-      if (path === './bar/baz.js') {
-        return { absolutePath: '/abs/path/bar/baz.js', redirectPath: null };
+    resolveMock: vi.fn((path, root, importer, findMockRedirect) => {
+      const result =
+        path === './bar/baz.js'
+          ? { absolutePath: '/abs/path/bar/baz.js', redirectPath: null }
+          : path === './bar/baz.utils'
+            ? { absolutePath: '/abs/path/bar/baz.utils.ts', redirectPath: null }
+            : path === './bar/baz.utils.ts'
+              ? { absolutePath: '/abs/path/bar/baz.utils.ts', redirectPath: null }
+              : { absolutePath: '/abs/path', redirectPath: null };
+
+      if (findMockRedirect) {
+        const redirectPath = findMockRedirect(root, result.absolutePath, null);
+        return { ...result, redirectPath };
       }
-      if (path === './bar/baz.utils') {
-        return { absolutePath: '/abs/path/bar/baz.utils.ts', redirectPath: null };
-      }
-      if (path === './bar/baz.utils.ts') {
-        return { absolutePath: '/abs/path/bar/baz.utils.ts', redirectPath: null };
-      }
-      return { absolutePath: '/abs/path', redirectPath: null };
+
+      return result;
     }),
   };
 });
@@ -50,17 +55,21 @@ describe('extractMockCalls', () => {
   const root = '/project';
   const coreOptions = { disableTelemetry: true };
 
+  const findMockRedirect = vi.fn(() => null);
+
   const extractMockCalls = (previewContent: string) => {
     vi.mocked(readFileSync).mockReturnValue(previewContent);
     return extractModule.extractMockCalls(
       { previewConfigPath, configDir, coreOptions },
       parser,
-      root
+      root,
+      findMockRedirect
     );
   };
 
   beforeEach(() => {
     vi.clearAllMocks();
+    findMockRedirect.mockReturnValue(null);
   });
 
   it('returns empty array if readFileSync throws', () => {
@@ -84,7 +93,12 @@ describe('extractMockCalls', () => {
         spy: true,
       },
     ]);
-    expect(resolveModule.resolveMock).toHaveBeenCalledWith('foo', root, previewConfigPath);
+    expect(resolveModule.resolveMock).toHaveBeenCalledWith(
+      'foo',
+      root,
+      previewConfigPath,
+      findMockRedirect
+    );
   });
 
   it('handles no sb.mock calls in preview file', () => {
diff --git a/code/core/src/core-server/mocking-utils/extract.ts b/code/core/src/mocking-utils/extract.ts
similarity index 95%
rename from code/core/src/core-server/mocking-utils/extract.ts
rename to code/core/src/mocking-utils/extract.ts
index 8edf075e3146..cc809760c564 100644
--- a/code/core/src/core-server/mocking-utils/extract.ts
+++ b/code/core/src/mocking-utils/extract.ts
@@ -91,7 +91,12 @@ export function extractMockCalls(
       jsx?: boolean;
     }
   ) => t.Node,
-  root: string
+  root: string,
+  findMockRedirect: (
+    root: string,
+    absolutePath: string,
+    externalPath: string | null
+  ) => string | null
 ): MockCall[] {
   try {
     const previewConfigCode = readFileSync(options.previewConfigPath, 'utf-8');
@@ -155,7 +160,12 @@ export function extractMockCalls(
           node.arguments[1].type === 'ObjectExpression' &&
           hasSpyTrue(node.arguments[1]);
 
-        const { absolutePath, redirectPath } = resolveMock(path, root, options.previewConfigPath);
+        const { absolutePath, redirectPath } = resolveMock(
+          path,
+          root,
+          options.previewConfigPath,
+          findMockRedirect
+        );
 
         const pathWithoutExtension = path.replace(/\.[^/.]+$/, '');
         const basenameAbsolutePath = basename(absolutePath);
diff --git a/code/core/src/mocking-utils/index.ts b/code/core/src/mocking-utils/index.ts
new file mode 100644
index 000000000000..5d418381446e
--- /dev/null
+++ b/code/core/src/mocking-utils/index.ts
@@ -0,0 +1,5 @@
+export * from './automock';
+export * from './extract';
+export * from './resolve';
+export * from './esmWalker';
+export * from './runtime';
diff --git a/code/core/src/core-server/mocking-utils/resolve.ts b/code/core/src/mocking-utils/resolve.ts
similarity index 95%
rename from code/core/src/core-server/mocking-utils/resolve.ts
rename to code/core/src/mocking-utils/resolve.ts
index 3c52b03eaec5..35c7ff5b56ea 100644
--- a/code/core/src/core-server/mocking-utils/resolve.ts
+++ b/code/core/src/mocking-utils/resolve.ts
@@ -1,7 +1,6 @@
 import { readFileSync, realpathSync } from 'node:fs';
 import { createRequire } from 'node:module';
 
-import { findMockRedirect } from '@vitest/mocker/redirect';
 import { dirname, isAbsolute, join, resolve } from 'pathe';
 import { exports as resolveExports } from 'resolve.exports';
 
@@ -72,7 +71,16 @@ export function getIsExternal(path: string, importer: string) {
  * @param root The project's root directory.
  * @param importer The absolute path of the file containing the mock call (the preview file).
  */
-export function resolveMock(path: string, root: string, importer: string) {
+export function resolveMock(
+  path: string,
+  root: string,
+  importer: string,
+  findMockRedirect: (
+    root: string,
+    absolutePath: string,
+    externalPath: string | null
+  ) => string | null
+) {
   const isExternal = getIsExternal(path, root);
   const externalPath = isExternal ? path : null;
 
diff --git a/code/core/src/mocking-utils/runtime.ts b/code/core/src/mocking-utils/runtime.ts
new file mode 100644
index 000000000000..eca3c51629f4
--- /dev/null
+++ b/code/core/src/mocking-utils/runtime.ts
@@ -0,0 +1,28 @@
+import { resolvePackageDir } from 'storybook/internal/common';
+
+import { buildSync } from 'esbuild';
+import { join } from 'pathe';
+
+const runtimeTemplatePath = join(
+  resolvePackageDir('storybook'),
+  'assets',
+  'server',
+  'mocker-runtime.template.js'
+);
+
+export function getMockerRuntime() {
+  // Use esbuild to bundle the runtime script and its dependencies (`@vitest/mocker`, etc.)
+  // into a single, self-contained string of code.
+  const bundleResult = buildSync({
+    entryPoints: [runtimeTemplatePath],
+    bundle: true,
+    write: false, // Return the result in memory instead of writing to disk
+    format: 'esm',
+    target: 'es2020',
+    external: ['msw/browser', 'msw/core/http'],
+  });
+
+  const runtimeScriptContent = bundleResult.outputFiles[0].text;
+
+  return runtimeScriptContent;
+}
diff --git a/code/yarn.lock b/code/yarn.lock
index 3b713130c6f9..9065aeee49d4 100644
--- a/code/yarn.lock
+++ b/code/yarn.lock
@@ -7886,6 +7886,7 @@ __metadata:
   dependencies:
     "@storybook/csf-plugin": "workspace:*"
     "@types/node": "npm:^22.0.0"
+    "@vitest/mocker": "npm:3.2.4"
     empathic: "npm:^2.0.0"
     es-module-lexer: "npm:^1.5.0"
     glob: "npm:^10.0.0"
@@ -7909,6 +7910,7 @@ __metadata:
     "@types/node": "npm:^22.0.0"
     "@types/pretty-hrtime": "npm:^1.0.0"
     "@types/webpack-hot-middleware": "npm:^2.25.6"
+    "@vitest/mocker": "npm:3.2.4"
     case-sensitive-paths-webpack-plugin: "npm:^2.4.0"
     cjs-module-lexer: "npm:^1.2.3"
     css-loader: "npm:^7.1.2"
@@ -26023,7 +26025,6 @@ __metadata:
     "@types/semver": "npm:^7.5.8"
     "@types/ws": "npm:^8"
     "@vitest/expect": "npm:3.2.4"
-    "@vitest/mocker": "npm:3.2.4"
     "@vitest/spy": "npm:3.2.4"
     "@vitest/utils": "npm:^3.2.4"
     "@yarnpkg/esbuild-plugin-pnp": "npm:^3.0.0-rc.10"