diff --git a/bench/bundle-test/index-wasm.ts b/bench/bundle-test/index-wasm.ts
index e31309b1..2ad36d8f 100644
--- a/bench/bundle-test/index-wasm.ts
+++ b/bench/bundle-test/index-wasm.ts
@@ -1,5 +1,5 @@
 import { codeToHtml, createShikiInternal } from '@shikijs/core'
-import { createWasmOnigEngine } from '@shikijs/engine-oniguruma'
+import { createOnigurumaEngine } from '@shikijs/engine-oniguruma'
 
 const shiki = createShikiInternal(
   {
@@ -9,7 +9,7 @@ const shiki = createShikiInternal(
     themes: [
       import('@shikijs/themes/vitesse-dark'),
     ],
-    engine: createWasmOnigEngine(import('@shikijs/engine-oniguruma/wasm-inlined')),
+    engine: createOnigurumaEngine(import('@shikijs/engine-oniguruma/wasm-inlined')),
   },
 )
 
diff --git a/packages/core/src/constructors/highlighter.ts b/packages/core/src/constructors/highlighter.ts
index 19821608..5c8ec3c1 100644
--- a/packages/core/src/constructors/highlighter.ts
+++ b/packages/core/src/constructors/highlighter.ts
@@ -16,7 +16,7 @@ import { createShikiInternalSync } from './internal-sync'
  *
  * @see http://shiki.style/guide/bundles#fine-grained-bundle
  */
-export async function createHighlighterCore(options: HighlighterCoreOptions = {}): Promise<HighlighterCore> {
+export async function createHighlighterCore(options: HighlighterCoreOptions<false>): Promise<HighlighterCore> {
   const internal = await createShikiInternal(options)
 
   return {
@@ -39,7 +39,7 @@ export async function createHighlighterCore(options: HighlighterCoreOptions = {}
  *
  * @see http://shiki.style/guide/bundles#fine-grained-bundle
  */
-export function createHighlighterCoreSync(options: HighlighterCoreOptions<true> = {}): HighlighterCore {
+export function createHighlighterCoreSync(options: HighlighterCoreOptions<true>): HighlighterCore {
   const internal = createShikiInternalSync(options)
 
   return {
@@ -56,11 +56,11 @@ export function createHighlighterCoreSync(options: HighlighterCoreOptions<true>
 
 export function makeSingletonHighlighterCore(
   createHighlighter: typeof createHighlighterCore,
-): (options?: Partial<HighlighterCoreOptions>) => Promise<HighlighterCore> {
+): (options: HighlighterCoreOptions) => Promise<HighlighterCore> {
   let _shiki: ReturnType<typeof createHighlighterCore>
 
   async function getSingletonHighlighterCore(
-    options: Partial<HighlighterCoreOptions> = {},
+    options: HighlighterCoreOptions,
   ): Promise<HighlighterCore> {
     if (!_shiki) {
       _shiki = createHighlighter({
@@ -89,7 +89,7 @@ export const getSingletonHighlighterCore = /* @__PURE__ */ makeSingletonHighligh
  * @deprecated Use `createHighlighterCore` or `getSingletonHighlighterCore` instead.
  */
 /* v8 ignore next 5 */
-export function getHighlighterCore(options: HighlighterCoreOptions = {}): Promise<HighlighterCore> {
+export function getHighlighterCore(options: HighlighterCoreOptions): Promise<HighlighterCore> {
   warnDeprecated('`getHighlighterCore` is deprecated. Use `createHighlighterCore` or `getSingletonHighlighterCore` instead.')
   return createHighlighterCore(options)
 }
diff --git a/packages/core/src/constructors/internal.ts b/packages/core/src/constructors/internal.ts
index 75085c15..4e0b3bcb 100644
--- a/packages/core/src/constructors/internal.ts
+++ b/packages/core/src/constructors/internal.ts
@@ -11,10 +11,13 @@ import { createShikiInternalSync } from './internal-sync'
 /**
  * Get the minimal shiki context for rendering.
  */
-export async function createShikiInternal(options: HighlighterCoreOptions = {}): Promise<ShikiInternal> {
+export async function createShikiInternal(options: HighlighterCoreOptions): Promise<ShikiInternal> {
   if (options.loadWasm) {
     warnDeprecated('`loadWasm` option is deprecated. Use `engine: createOnigurumaEngine(loadWasm)` instead.')
   }
+  if (!options.engine) {
+    throw new Error('`engine` option is required.')
+  }
 
   const [
     themes,
@@ -38,7 +41,7 @@ export async function createShikiInternal(options: HighlighterCoreOptions = {}):
 /**
  * @deprecated Use `createShikiInternal` instead.
  */
-export function getShikiInternal(options: HighlighterCoreOptions = {}): Promise<ShikiInternal> {
+export function getShikiInternal(options: HighlighterCoreOptions): Promise<ShikiInternal> {
   warnDeprecated('`getShikiInternal` is deprecated. Use `createShikiInternal` instead.')
   return createShikiInternal(options)
 }
diff --git a/packages/core/test/core.test.ts b/packages/core/test/core.test.ts
index da61b1d8..5f58dace 100644
--- a/packages/core/test/core.test.ts
+++ b/packages/core/test/core.test.ts
@@ -1,7 +1,7 @@
+import { createJavaScriptRegexEngine } from '@shikijs/engine-javascript'
 import { createOnigurumaEngine } from '@shikijs/engine-oniguruma'
 
 import { wasmBinary } from '@shikijs/engine-oniguruma/wasm-inlined'
-
 import js from '@shikijs/langs/javascript'
 import ts from '@shikijs/langs/typescript'
 import mtp from '@shikijs/themes/material-theme-palenight'
@@ -67,6 +67,7 @@ describe('should', () => {
       langs: [
         import('@shikijs/langs/cpp'),
       ],
+      engine: createJavaScriptRegexEngine(),
     })
 
     expect(shiki.getLoadedLanguages().sort())
@@ -85,7 +86,9 @@ describe('should', () => {
   })
 
   it('works without no initial langs and themes', async () => {
-    using shiki = await createHighlighterCore()
+    using shiki = await createHighlighterCore({
+      engine: createJavaScriptRegexEngine(),
+    })
 
     await shiki.loadLanguage(js)
     await shiki.loadTheme(nord)
@@ -101,6 +104,7 @@ describe('should', () => {
         mylang: 'javascript',
         mylang2: 'js', // nested alias
       },
+      engine: createJavaScriptRegexEngine(),
     })
 
     await shiki.loadLanguage(js)
@@ -117,6 +121,7 @@ describe('should', () => {
       langAlias: {
         js: 'typescript',
       },
+      engine: createJavaScriptRegexEngine(),
     })
 
     await shiki.loadLanguage(ts)
@@ -132,6 +137,7 @@ describe('errors', () => {
     using shiki = await createHighlighterCore({
       themes: [nord],
       langs: [js as any],
+      engine: createJavaScriptRegexEngine(),
     })
 
     await expect(() => shiki.codeToHtml('console.log("Hi")', { lang: 'javascript', theme: 'invalid' }))
@@ -142,6 +148,7 @@ describe('errors', () => {
     using shiki = await createHighlighterCore({
       themes: [nord],
       langs: [js as any],
+      engine: createJavaScriptRegexEngine(),
     })
 
     await expect(() => shiki.codeToHtml('console.log("Hi")', { lang: 'abc', theme: 'nord' }))
@@ -175,6 +182,7 @@ describe('errors', () => {
         mylang: 'mylang2',
         mylang2: 'mylang',
       },
+      engine: createJavaScriptRegexEngine(),
     })
 
     await shiki.loadLanguage(js)
@@ -187,7 +195,8 @@ describe('errors', () => {
   it('throw on using disposed instance', async () => {
     using shiki = await createHighlighterCore({
       themes: [nord],
-      langs: [js as any],
+      langs: [js],
+      engine: createJavaScriptRegexEngine(),
     })
 
     expect(shiki.codeToHtml('console.log("Hi")', { lang: 'javascript', theme: 'nord' }))
diff --git a/packages/core/test/injections.test.ts b/packages/core/test/injections.test.ts
index cc930160..ccade94d 100644
--- a/packages/core/test/injections.test.ts
+++ b/packages/core/test/injections.test.ts
@@ -4,7 +4,7 @@ import html from '@shikijs/langs/html'
 import ts from '@shikijs/langs/typescript'
 import vue from '@shikijs/langs/vue'
 import vl from '@shikijs/themes/vitesse-light'
-import { codeToHtml, createHighlighterCore } from 'shiki'
+import { codeToHtml, createHighlighterCore, createJavaScriptRegexEngine } from 'shiki'
 import { expect, it } from 'vitest'
 
 // Basically we need to make sure that the syntax inside `v-if` and `{{}}` is highlighted correctly.
@@ -35,6 +35,7 @@ it('injections-side-effects vue', async () => {
     langs: [
       html,
     ],
+    engine: createJavaScriptRegexEngine(),
   })
 
   const code = `<h1 v-if="count == 1 ? true : 'str'.toUpperCase()">{{ count * 2 }}</h1>`
@@ -60,6 +61,7 @@ it('injections-side-effects angular-html', async () => {
     langs: [
       html,
     ],
+    engine: createJavaScriptRegexEngine(),
   })
 
   const code = `<h2>Hero List</h2>
@@ -126,6 +128,7 @@ it('injections-side-effects angular-ts', async () => {
     langs: [
       ts,
     ],
+    engine: createJavaScriptRegexEngine(),
   })
 
   const code = `
diff --git a/packages/shiki/test/cf.ts b/packages/shiki/test/cf.ts
index 5a6a83c8..6f97b043 100644
--- a/packages/shiki/test/cf.ts
+++ b/packages/shiki/test/cf.ts
@@ -1,24 +1,21 @@
 import type { LanguageRegistration } from '@shikijs/types'
-import { loadWasm } from '@shikijs/engine-oniguruma'
+import { createOnigurumaEngine } from '@shikijs/engine-oniguruma'
 import js from '@shikijs/langs/javascript'
 import nord from '@shikijs/themes/nord'
-import { createHighlighterCore } from 'shiki/core'
 
+import { createHighlighterCore } from 'shiki/core'
 // @ts-expect-error no types
 // eslint-disable-next-line antfu/no-import-dist
 import wasm from '../dist/onig.wasm'
 
-// eslint-disable-next-line antfu/no-top-level-await
-await loadWasm(wasm)
-
-// cloudflare also supports dynamic import
-// await loadWasm(import('../dist/onig.wasm'))
-
 export default {
   async fetch() {
     const highlighter = await createHighlighterCore({
       themes: [nord],
       langs: [js as LanguageRegistration[]],
+      // cloudflare also supports dynamic import
+      // engine: createOnigurumaEngine(import('shiki/onig.wasm')),
+      engine: createOnigurumaEngine(wasm),
     })
 
     return new Response(
diff --git a/packages/shiki/test/get-highlighter.test.ts b/packages/shiki/test/get-highlighter.test.ts
index 1264ffcd..71cc5026 100644
--- a/packages/shiki/test/get-highlighter.test.ts
+++ b/packages/shiki/test/get-highlighter.test.ts
@@ -1,4 +1,4 @@
-import { createOnigurumaEngine, getSingletonHighlighter } from 'shiki'
+import { createJavaScriptRegexEngine, createOnigurumaEngine, getSingletonHighlighter } from 'shiki'
 import { expect, it } from 'vitest'
 import { getSingletonHighlighterCore } from '../src/core'
 import js from '../src/langs/javascript.mjs'
@@ -17,6 +17,7 @@ it('getSingletonHighlighterCore', async () => {
 
   const shiki2 = await getSingletonHighlighterCore({
     themes: [mtp],
+    engine: createJavaScriptRegexEngine(),
   })
 
   expect(shiki1).toBe(shiki2)
diff --git a/packages/types/src/options.ts b/packages/types/src/options.ts
index d8bb632f..2c95c878 100644
--- a/packages/types/src/options.ts
+++ b/packages/types/src/options.ts
@@ -10,7 +10,7 @@ export interface HighlighterCoreOptions<Sync extends boolean = false> {
   /**
    * Custom RegExp engine.
    */
-  engine?: Sync extends true ? RegexEngine : Awaitable<RegexEngine>
+  engine: Sync extends true ? RegexEngine : Awaitable<RegexEngine>
   /**
    * Theme names, or theme registration objects to be loaded upfront.
    */
@@ -38,7 +38,11 @@ export interface HighlighterCoreOptions<Sync extends boolean = false> {
   loadWasm?: Sync extends true ? never : LoadWasmOptions
 }
 
-export interface BundledHighlighterOptions<L extends string, T extends string> extends Pick<HighlighterCoreOptions, 'warnings' | 'engine'> {
+export interface BundledHighlighterOptions<L extends string, T extends string> extends Pick<HighlighterCoreOptions, 'warnings'> {
+  /**
+   * Custom RegExp engine.
+   */
+  engine?: Awaitable<RegexEngine>
   /**
    * Theme registation
    *