diff --git a/packages/script/src/module.ts b/packages/script/src/module.ts
index 99131a99..cdc99f7c 100644
--- a/packages/script/src/module.ts
+++ b/packages/script/src/module.ts
@@ -1023,6 +1023,7 @@ export default defineNuxtModule<ModuleOptions>({
         dev: true,
       })
       addBuildPlugin(NuxtScriptBundleTransformer({
+        nuxt,
         scripts: registryScriptsWithImport,
         registryConfig: nuxt.options.runtimeConfig.public.scripts as Record<string, any> | undefined,
         proxyConfigs,
diff --git a/packages/script/src/plugins/transform.ts b/packages/script/src/plugins/transform.ts
index 8e056902..7258ad6a 100644
--- a/packages/script/src/plugins/transform.ts
+++ b/packages/script/src/plugins/transform.ts
@@ -1,3 +1,4 @@
+import type { Nuxt } from '@nuxt/schema'
 import type { FetchOptions } from 'ofetch'
 import type { SourceMapInput } from 'rollup'
 import type { InferInput } from 'valibot'
@@ -84,6 +85,12 @@ export interface AssetBundlerTransformerOptions {
    * @default false
    */
   integrity?: boolean | IntegrityAlgorithm
+  /**
+   * The active Nuxt instance. Used to resolve the build directory and register the
+   * `build:done` copy hook. Defaults to `useNuxt()`; pass it explicitly to run the
+   * transformer without an active Nuxt context (e.g. unit tests).
+   */
+  nuxt?: Nuxt
   renderedScript?: Map<string, RenderedScriptMeta | Error>
   /**
    * Set of registry script keys that use Partytown.
@@ -214,7 +221,7 @@ async function downloadScript(opts: {
 export function NuxtScriptBundleTransformer(options: AssetBundlerTransformerOptions = {
   renderedScript: new Map(),
 }) {
-  const nuxt = useNuxt()
+  const nuxt = options.nuxt ?? useNuxt()
   const { renderedScript = new Map() } = options
   const cacheDir = join(nuxt.options.buildDir, 'cache', 'scripts')
 
@@ -239,7 +246,7 @@ export function NuxtScriptBundleTransformer(options: AssetBundlerTransformerOpti
     await Promise.all(scripts.map(async ([url, content]) => {
       if (content instanceof Error || !content.filename)
         return
-      await fsp.writeFile(join(nuxt.options.buildDir, 'cache', 'scripts', content.filename), content.content)
+      await fsp.writeFile(join(cacheDir, content.filename), content.content)
       logger.debug(colors.gray(`  ├─ ${url} → ${joinURL(content.src)} (${content.size.toFixed(2)} kB ${content.encoding})`))
     }))
   })
diff --git a/test/unit/bundle-sdk-patches.test.ts b/test/unit/bundle-sdk-patches.test.ts
index 1cd7c7ee..522eb9b4 100644
--- a/test/unit/bundle-sdk-patches.test.ts
+++ b/test/unit/bundle-sdk-patches.test.ts
@@ -34,18 +34,14 @@ vi.mock('../../packages/script/src/assets', () => ({
 const fetchMock = vi.fn()
 vi.stubGlobal('fetch', fetchMock)
 
-vi.mock('@nuxt/kit', async (og) => {
-  const mod = await og<typeof import('@nuxt/kit')>()
-  const nuxt = {
-    options: { buildDir: '.nuxt', app: { baseURL: '/' }, runtimeConfig: { app: {} } },
-    hooks: { hook: vi.fn() },
-  }
-  return { ...mod, useNuxt: () => nuxt, tryUseNuxt: () => nuxt }
-})
-
 vi.mocked(hasProtocol).mockImplementation(() => true)
 vi.mocked(hash).mockImplementation(() => 'fathom-script')
 
+const mockNuxt = {
+  options: { buildDir: '.nuxt', app: { baseURL: '/' }, runtimeConfig: { app: {} } },
+  hooks: { hook: vi.fn() },
+} as any
+
 let _proxyConfigs: ReturnType<typeof buildProxyConfigsFromRegistry> | undefined
 async function getProxyConfigs() {
   if (!_proxyConfigs)
@@ -63,7 +59,7 @@ function mockUpstream(bytes: Buffer) {
 }
 
 async function runTransform(code: string, options: AssetBundlerTransformerOptions) {
-  const plugin = NuxtScriptBundleTransformer(options).vite() as any
+  const plugin = NuxtScriptBundleTransformer({ ...options, nuxt: mockNuxt }).vite() as any
   await plugin.transform.handler.call({}, code, 'file.js')
 }
 
diff --git a/test/unit/bundle-two-deploy-repro.test.ts b/test/unit/bundle-two-deploy-repro.test.ts
index 8c244881..50400e4a 100644
--- a/test/unit/bundle-two-deploy-repro.test.ts
+++ b/test/unit/bundle-two-deploy-repro.test.ts
@@ -31,23 +31,19 @@ vi.mock('../../packages/script/src/assets', () => ({
 const fetchMock = vi.fn()
 vi.stubGlobal('fetch', fetchMock)
 
-vi.mock('@nuxt/kit', async (og) => {
-  const mod = await og<typeof import('@nuxt/kit')>()
-  const nuxt = {
-    options: { buildDir: '.nuxt', app: { baseURL: '/' }, runtimeConfig: { app: {} } },
-    hooks: { hook: vi.fn() },
-  }
-  return { ...mod, useNuxt: () => nuxt, tryUseNuxt: () => nuxt }
-})
-
 vi.mocked(hasProtocol).mockImplementation(() => true)
 // Source URL hash is stable across both "deploys" — the URL doesn't change between deployments,
 // only the upstream bytes do. This is exactly the real-world scenario in #724.
 vi.mocked(hash).mockImplementation(() => 'adsbygoogle')
 
+const mockNuxt = {
+  options: { buildDir: '.nuxt', app: { baseURL: '/' }, runtimeConfig: { app: {} } },
+  hooks: { hook: vi.fn() },
+} as any
+
 async function runTransform(code: string, options?: AssetBundlerTransformerOptions) {
   mockBundleStorage.hasItem.mockResolvedValue(false)
-  const plugin = NuxtScriptBundleTransformer({ renderedScript: new Map(), ...options }).vite() as any
+  const plugin = NuxtScriptBundleTransformer({ renderedScript: new Map(), ...options, nuxt: mockNuxt }).vite() as any
   const out = await plugin.transform.handler.call({}, code, 'file.js')
   return out?.code as string
 }
diff --git a/test/unit/transform.test.ts b/test/unit/transform.test.ts
index 7f4ed929..45044828 100644
--- a/test/unit/transform.test.ts
+++ b/test/unit/transform.test.ts
@@ -51,45 +51,10 @@ vi.stubGlobal('fetch', vi.fn(() => {
   return Promise.resolve({ arrayBuffer: vi.fn(() => Buffer.from('')), ok: true, headers: { get: vi.fn() } })
 }))
 
-vi.mock('@nuxt/kit', async (og) => {
-  const mod = await og<typeof import('@nuxt/kit')>()
-
-  return {
-    ...mod,
-    useNuxt() {
-      return {
-        options: {
-          buildDir: '.nuxt',
-          app: {
-            baseURL: '/',
-          },
-          runtimeConfig: {
-            app: {},
-          },
-        },
-        hooks: {
-          hook: vi.fn(),
-        },
-      }
-    },
-    tryUseNuxt() {
-      return {
-        options: {
-          buildDir: '.nuxt',
-          app: {
-            baseURL: '/',
-          },
-          runtimeConfig: {
-            app: {},
-          },
-        },
-        hooks: {
-          hook: vi.fn(),
-        },
-      }
-    },
-  }
-})
+const mockNuxt = {
+  options: { buildDir: '.nuxt', app: { baseURL: '/' }, runtimeConfig: { app: {} } },
+  hooks: { hook: vi.fn() },
+} as any
 
 // we want to control normalizeScriptData() output
 vi.mocked(hasProtocol).mockImplementation(() => true)
@@ -97,7 +62,7 @@ vi.mocked(hasProtocol).mockImplementation(() => true)
 vi.mocked(hash).mockImplementation(src => src.pathname)
 
 async function transform(code: string | string[], options?: AssetBundlerTransformerOptions) {
-  const plugin = NuxtScriptBundleTransformer(options).vite() as any
+  const plugin = NuxtScriptBundleTransformer({ ...options, nuxt: mockNuxt }).vite() as any
   const res = await plugin.transform.handler.call(
     {},
     Array.isArray(code) ? code.join('\n') : code,