diff --git a/apps/stage-tamagotchi/src/preload/beat-sync.ts b/apps/stage-tamagotchi/src/preload/beat-sync.ts
index ca537100c..02fbe5247 100644
--- a/apps/stage-tamagotchi/src/preload/beat-sync.ts
+++ b/apps/stage-tamagotchi/src/preload/beat-sync.ts
@@ -5,18 +5,23 @@ import { createDetector, StageEnvironment } from '@proj-airi/stage-shared'
 import { ipcRenderer } from 'electron'
 
 import { beatSyncSignalBeat, beatSyncToggle } from '../shared/eventa'
+import { exposeWithCustomAPI } from './shared'
 
 const context = createContext(electronAPI.ipcRenderer).context
 const signalBeat = defineInvoke(context, beatSyncSignalBeat)
 
+function enableLoopbackAudio() {
+  return ipcRenderer.invoke('enable-loopback-audio')
+}
+
+function disableLoopbackAudio() {
+  return ipcRenderer.invoke('disable-loopback-audio')
+}
+
 const detector = createDetector({
   env: StageEnvironment.Tamagotchi,
-  enableLoopbackAudio() {
-    return ipcRenderer.invoke('enable-loopback-audio')
-  },
-  disableLoopbackAudio() {
-    return ipcRenderer.invoke('disable-loopback-audio')
-  },
+  enableLoopbackAudio,
+  disableLoopbackAudio,
 })
 
 detector.on('beat', () => signalBeat())
@@ -29,3 +34,9 @@ defineInvokeHandler(context, beatSyncToggle, async (enabled) => {
     detector.stop()
   }
 })
+
+exposeWithCustomAPI({
+  enableLoopbackAudio,
+  disableLoopbackAudio,
+  detector,
+})
diff --git a/packages/stage-shared/src/beat-sync.ts b/packages/stage-shared/src/beat-sync.ts
index 77aacc777..0671dd1ce 100644
--- a/packages/stage-shared/src/beat-sync.ts
+++ b/packages/stage-shared/src/beat-sync.ts
@@ -11,7 +11,7 @@ export interface DetectorEventMap {
   beat: (e: AnalyserBeatEvent) => void
 }
 
-interface Detector {
+export interface Detector {
   start: (createSource: (context: AudioContext) => Promise<AudioNode>) => Promise<void>
   updateParameters: (params: Partial<AnalyserWorkletParameters>) => void
   startScreenCapture: () => Promise<void>
@@ -24,7 +24,7 @@ interface Detector {
   readonly source: AudioNode | undefined
 }
 
-type CreateDetectorOptions = |
+export type CreateDetectorOptions = |
   {
     env: StageEnvironment.Tamagotchi
     enableLoopbackAudio: () => Promise<any>