diff --git a/app/src/main/AndroidManifest.xml b/app/src/main/AndroidManifest.xml
index f5bee99..f711c5c 100644
--- a/app/src/main/AndroidManifest.xml
+++ b/app/src/main/AndroidManifest.xml
@@ -38,6 +38,11 @@
 
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
+            <intent-filter>
+                <action android:name="com.adamrocker.android.simeji.ACTION_INTERCEPT" />
+                <category android:name="com.adamrocker.android.simeji.REPLACE" />
+                <category android:name="android.intent.category.DEFAULT" />
+            </intent-filter>
         </activity-alias>
 
         <activity
diff --git a/app/src/main/kotlin/net/mm2d/codereader/MainActivity.kt b/app/src/main/kotlin/net/mm2d/codereader/MainActivity.kt
index 3ac4c82..1b7db5f 100644
--- a/app/src/main/kotlin/net/mm2d/codereader/MainActivity.kt
+++ b/app/src/main/kotlin/net/mm2d/codereader/MainActivity.kt
@@ -8,6 +8,7 @@
 package net.mm2d.codereader
 
 import android.animation.ValueAnimator
+import android.content.Intent // Mushroom mode 用に追加
 import android.os.Build.VERSION
 import android.os.Build.VERSION_CODES
 import android.os.Bundle
@@ -42,13 +43,16 @@ import net.mm2d.codereader.util.ReviewRequester
 import net.mm2d.codereader.util.Updater
 import net.mm2d.codereader.util.observe
 
+// Mushroom mode 用に追加
+const val ACTION_INTERCEPT_MAIN = "com.adamrocker.android.simeji.ACTION_INTERCEPT" // 定数名変更
+const val REPLACE_KEY_MAIN = "replace_key" // 定数名変更
+
 class MainActivity : AppCompatActivity() {
     private lateinit var binding: ActivityMainBinding
     private lateinit var codeScanner: CodeScanner
-    private var started: Boolean = false
     private val launcher = registerForCameraPermissionRequest { granted, succeedToShowDialog ->
         if (granted) {
-            startCamera()
+            // パーミッションが付与されたら onResume でカメラが開始される
         } else if (!succeedToShowDialog) {
             PermissionDialog.show(this, CAMERA_PERMISSION_REQUEST_KEY)
         } else {
@@ -63,12 +67,16 @@ class MainActivity : AppCompatActivity() {
         Settings.get()
     }
     private var resultSet: Set<ScanResult> = emptySet()
+    private var isMushroomMode: Boolean = false // Mushroom mode 用フラグ
 
     override fun onCreate(
         savedInstanceState: Bundle?,
     ) {
         super.onCreate(savedInstanceState)
         enableEdgeToEdge()
+        // Mushroom mode の判定 (intent.action を確認)
+        isMushroomMode = intent.action?.contains(ACTION_INTERCEPT_MAIN) ?: false
+
         binding = ActivityMainBinding.inflate(layoutInflater)
         setContentView(binding.root)
         ViewCompat.setOnApplyWindowInsetsListener(binding.root) { view, insets ->
@@ -87,11 +95,11 @@ class MainActivity : AppCompatActivity() {
             DividerItemDecoration(this, DividerItemDecoration.VERTICAL),
         )
         vibrator = getSystemService()!!
-        codeScanner = CodeScanner(this, binding.previewView, ::onDetectCode)
+        codeScanner = CodeScanner(this, binding.previewView, ::onDetectCode) // CodeScanner はここで初期化
         binding.flash.setOnClickListener {
             codeScanner.toggleTorch()
         }
-        codeScanner.getTouchStateStream().observe(this) {
+        codeScanner.getTouchStateStream().observe(this) { // メソッド名を getTouchStateStream に戻す
             onFlashOn(it)
         }
         detectedPresenter = DetectedPresenter(
@@ -116,29 +124,54 @@ class MainActivity : AppCompatActivity() {
                 expandList()
             }
         }
-        if (CameraPermission.hasPermission(this)) {
-            startCamera()
-            Updater.startIfAvailable(this)
-        } else {
-            launcher.launch()
-        }
         PermissionDialog.registerListener(this, CAMERA_PERMISSION_REQUEST_KEY) {
             finishByError()
         }
         OptionsMenuPresenter(this, binding.menu).setUp()
+        Updater.startIfAvailable(this) // Updaterはパーミッション状態に関わらず呼べるならここに
     }
 
-    override fun onRestart() {
-        super.onRestart()
-        if (!started) {
-            if (CameraPermission.hasPermission(this)) {
-                startCamera()
-            } else {
-                finishByError()
+    // onStart を追加
+    override fun onStart() {
+        super.onStart()
+        if (!CameraPermission.hasPermission(this)) {
+            launcher.launch()
+        }
+        // パーミッションがある場合は onResume でカメラが開始される
+    }
+
+    // onResume を追加/修正
+    override fun onResume() {
+        super.onResume()
+        if (CameraPermission.hasPermission(this)) {
+            if (::codeScanner.isInitialized) { // codeScannerが初期化済みか確認
+                codeScanner.start()  // カメラの初期化/再初期化
+                codeScanner.resume() // 解析の再開
             }
         }
     }
 
+    // onPause を追加
+    override fun onPause() {
+        super.onPause()
+        if (::codeScanner.isInitialized) { // codeScannerが初期化済みか確認
+            codeScanner.pause()          // 解析の一時停止
+            codeScanner.shutdownCamera() // カメラリソースの解放
+        }
+    }
+
+    override fun onRestart() {
+        super.onRestart()
+        // 以前の onRestart のロジックは onStart と onResume でカバーされるため、
+        // ここでの特別なカメラ処理は不要になる。
+    }
+
+    // onDestroy を追加 (任意、デバッグや最終確認用)
+    override fun onDestroy() {
+        // onPause で shutdownCamera が呼ばれるため、通常は不要。
+        super.onDestroy()
+    }
+
     private fun finishByError() {
         toastPermissionError()
         super.finish()
@@ -166,18 +199,12 @@ class MainActivity : AppCompatActivity() {
         binding.flash.setImageResource(icon)
     }
 
-    private fun startCamera() {
-        if (started) return
-        started = true
-        codeScanner.start()
-    }
-
     private fun onDetectCode(
         imageProxy: ImageProxy,
         codes: List<Barcode>,
     ) {
         val detected = mutableListOf<Barcode>()
-        codes.forEach {
+        codes.forEach { // it を使用
             val value = it.rawValue ?: return@forEach
             val result = ScanResult(
                 value = value,
@@ -186,12 +213,23 @@ class MainActivity : AppCompatActivity() {
                 isUrl = it.valueType == Barcode.TYPE_URL,
             )
             if (!resultSet.contains(result)) {
+                if (isMushroomMode) { // Mushroom mode の処理を先に行う
+                    val data = Intent()
+                    data.putExtra(REPLACE_KEY_MAIN, result.value)
+                    setResult(RESULT_OK, data)
+                    finish()
+                    return // Mushroomモードでは最初の検出でActivityを終了
+                }
                 viewModel.add(result)
                 vibrate()
                 detected.add(it)
             }
         }
-        if (detected.isEmpty()) return
+        if (detected.isEmpty()) {
+            // imageProxy.close() は CodeAnalyzer 内で自動的に行われるはずなので、
+            // ここでの呼び出しは不要。
+            return
+        }
         detectedPresenter.onDetected(imageProxy, detected)
     }
 
diff --git a/app/src/main/kotlin/net/mm2d/codereader/code/CodeScanner.kt b/app/src/main/kotlin/net/mm2d/codereader/code/CodeScanner.kt
index e7255a4..f57676a 100644
--- a/app/src/main/kotlin/net/mm2d/codereader/code/CodeScanner.kt
+++ b/app/src/main/kotlin/net/mm2d/codereader/code/CodeScanner.kt
@@ -14,6 +14,7 @@ import androidx.camera.core.ImageAnalysis
 import androidx.camera.core.ImageProxy
 import androidx.camera.core.Preview
 import androidx.camera.core.TorchState
+import androidx.camera.core.UseCase
 import androidx.camera.core.resolutionselector.AspectRatioStrategy
 import androidx.camera.core.resolutionselector.ResolutionSelector
 import androidx.camera.lifecycle.ProcessCameraProvider
@@ -40,13 +41,20 @@ class CodeScanner(
     private val analyzer: CodeAnalyzer = CodeAnalyzer(scanner, callback)
     private var camera: Camera? = null
     private val torchStateFlow: MutableStateFlow<Boolean> = MutableStateFlow(false)
+
+    private var cameraProviderInternal: ProcessCameraProvider? = null
+    private var previewUseCaseInternal: Preview? = null
+    private var analysisUseCaseInternal: ImageAnalysis? = null
+
     fun getTouchStateStream(): Flow<Boolean> = torchStateFlow
 
     init {
         activity.lifecycle.addObserver(
             LifecycleEventObserver { _, event ->
                 if (event == Event.ON_DESTROY) {
-                    workerExecutor.shutdown()
+                    if (!workerExecutor.isShutdown) {
+                        workerExecutor.shutdown()
+                    }
                     scanner.close()
                 }
             },
@@ -56,7 +64,13 @@ class CodeScanner(
     fun start() {
         val future = ProcessCameraProvider.getInstance(activity)
         future.addListener({
-            setUp(future.get())
+            try {
+                val provider = future.get()
+                this.cameraProviderInternal = provider
+                setUp(provider)
+            } catch (e: Exception) {
+                Timber.e(e, "CodeScanner: Failed to get ProcessCameraProvider in start() listener.")
+            }
         }, ContextCompat.getMainExecutor(activity))
     }
 
@@ -66,36 +80,59 @@ class CodeScanner(
         val resolutionSelector = ResolutionSelector.Builder()
             .setAspectRatioStrategy(AspectRatioStrategy.RATIO_16_9_FALLBACK_AUTO_STRATEGY)
             .build()
+
         val preview = Preview.Builder()
             .setResolutionSelector(resolutionSelector)
             .build()
         preview.surfaceProvider = previewView.surfaceProvider
+        this.previewUseCaseInternal = preview
 
         val analysis = ImageAnalysis.Builder()
             .setResolutionSelector(resolutionSelector)
             .setBackpressureStrategy(ImageAnalysis.STRATEGY_KEEP_ONLY_LATEST)
             .build()
         analysis.setAnalyzer(workerExecutor, analyzer)
+        this.analysisUseCaseInternal = analysis
 
         try {
             provider.unbindAll()
             val camera = provider.bindToLifecycle(
                 activity,
                 CameraSelector.DEFAULT_BACK_CAMERA,
-                preview,
-                analysis,
+                previewUseCaseInternal!!,
+                analysisUseCaseInternal!!,
             )
+            this.camera = camera
             camera.cameraInfo.torchState.observe(activity) { state ->
                 torchStateFlow.tryEmit(state == TorchState.ON)
             }
-            this.camera = camera
         } catch (e: Exception) {
-            Timber.e(e)
+            Timber.e(e, "CodeScanner: Use case binding failed in setUp.")
+            this.camera = null
+        }
+    }
+
+    fun shutdownCamera() {
+        cameraProviderInternal?.let { provider ->
+            val useCasesToUnbind = mutableListOf<UseCase>()
+            previewUseCaseInternal?.let { useCasesToUnbind.add(it) }
+            analysisUseCaseInternal?.let { useCasesToUnbind.add(it) }
+
+            if (useCasesToUnbind.isNotEmpty()) {
+                try {
+                    provider.unbind(*useCasesToUnbind.toTypedArray())
+                } catch (e: Exception) {
+                    Timber.e(e, "CodeScanner: [shutdownCamera] Error unbinding specific use cases: ${e.message}")
+                }
+            }
         }
+        previewUseCaseInternal = null
+        analysisUseCaseInternal = null
+        camera = null
     }
 
     fun toggleTorch() {
-        val camera = camera ?: return
+        val camera = this.camera ?: return
         camera.cameraControl.enableTorch(!torchStateFlow.value)
     }