diff --git a/apps/stage-pocket/android/app/build.gradle b/apps/stage-pocket/android/app/build.gradle
index 8e7876e01..005114daf 100644
--- a/apps/stage-pocket/android/app/build.gradle
+++ b/apps/stage-pocket/android/app/build.gradle
@@ -1,4 +1,5 @@
 apply plugin: 'com.android.application'
+apply plugin: 'org.jetbrains.kotlin.android'
 
 android {
     namespace = "ai.moeru.airi_pocket"
@@ -22,6 +23,9 @@ android {
             proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
         }
     }
+    kotlinOptions {
+        jvmTarget = '21'
+    }
 }
 
 repositories {
diff --git a/apps/stage-pocket/android/app/src/main/java/ai/moeru/airi_pocket/MainActivity.java b/apps/stage-pocket/android/app/src/main/java/ai/moeru/airi_pocket/MainActivity.java
deleted file mode 100644
index e9dc211cb..000000000
--- a/apps/stage-pocket/android/app/src/main/java/ai/moeru/airi_pocket/MainActivity.java
+++ /dev/null
@@ -1,84 +0,0 @@
-package ai.moeru.airi_pocket;
-
-import android.net.Uri;
-import android.net.http.SslError;
-import android.webkit.SslErrorHandler;
-import android.webkit.WebView;
-import com.getcapacitor.Bridge;
-import com.getcapacitor.BridgeActivity;
-import com.getcapacitor.BridgeWebViewClient;
-import com.getcapacitor.Logger;
-
-public class MainActivity extends BridgeActivity {
-
-    @Override
-    protected void load() {
-        super.load();
-
-        if (bridge == null || !bridge.isDevMode()) {
-            return;
-        }
-
-        bridge.setWebViewClient(new DebugTlsBypassWebViewClient(bridge));
-    }
-
-    private static final class DebugTlsBypassWebViewClient extends BridgeWebViewClient {
-
-        private final Bridge bridge;
-
-        private DebugTlsBypassWebViewClient(Bridge bridge) {
-            super(bridge);
-            this.bridge = bridge;
-        }
-
-        @Override
-        public void onReceivedSslError(WebView view, SslErrorHandler handler, SslError error) {
-            if (shouldBypassDevServerCertificate(error)) {
-                Logger.warn("Bypassing TLS certificate validation for debug dev server: " + error.getUrl());
-                handler.proceed();
-                return;
-            }
-
-            super.onReceivedSslError(view, handler, error);
-        }
-
-        // NOTICE: Android WebView rejects the self-signed HTTPS cert used by the debug dev server.
-        // Keep this bypass debug-only and scoped to the configured dev server origin.
-        private boolean shouldBypassDevServerCertificate(SslError error) {
-            if (error == null) {
-                return false;
-            }
-
-            String serverUrl = bridge.getServerUrl();
-            String errorUrl = error.getUrl();
-            if (serverUrl == null || serverUrl.isEmpty() || errorUrl == null || errorUrl.isEmpty()) {
-                return false;
-            }
-
-            Uri serverUri = Uri.parse(serverUrl);
-            Uri errorUri = Uri.parse(errorUrl);
-            if (!"https".equalsIgnoreCase(serverUri.getScheme())) {
-                return false;
-            }
-
-            return serverUri.getHost().equalsIgnoreCase(errorUri.getHost()) && normalizePort(serverUri) == normalizePort(errorUri);
-        }
-
-        private int normalizePort(Uri uri) {
-            int port = uri.getPort();
-            if (port != -1) {
-                return port;
-            }
-
-            if ("https".equalsIgnoreCase(uri.getScheme())) {
-                return 443;
-            }
-
-            if ("http".equalsIgnoreCase(uri.getScheme())) {
-                return 80;
-            }
-
-            return -1;
-        }
-    }
-}
diff --git a/apps/stage-pocket/android/app/src/main/java/ai/moeru/airi_pocket/MainActivity.kt b/apps/stage-pocket/android/app/src/main/java/ai/moeru/airi_pocket/MainActivity.kt
new file mode 100644
index 000000000..694610a96
--- /dev/null
+++ b/apps/stage-pocket/android/app/src/main/java/ai/moeru/airi_pocket/MainActivity.kt
@@ -0,0 +1,63 @@
+package ai.moeru.airi_pocket
+
+import android.net.Uri
+import android.net.http.SslError
+import android.webkit.SslErrorHandler
+import android.webkit.WebView
+import com.getcapacitor.Bridge
+import com.getcapacitor.BridgeActivity
+import com.getcapacitor.BridgeWebViewClient
+import com.getcapacitor.Logger
+
+class MainActivity : BridgeActivity() {
+
+    override fun load() {
+        super.load()
+
+        val bridge = bridge ?: return
+        if (!bridge.isDevMode) {
+            return
+        }
+
+        bridge.setWebViewClient(DebugTlsBypassWebViewClient(bridge))
+    }
+
+    private class DebugTlsBypassWebViewClient(
+        private val bridge: Bridge,
+    ) : BridgeWebViewClient(bridge) {
+
+        override fun onReceivedSslError(view: WebView, handler: SslErrorHandler, error: SslError) {
+            if (shouldBypassDevServerCertificate(error)) {
+                Logger.warn("Bypassing TLS certificate validation for debug dev server: ${error.url}")
+                handler.proceed()
+                return
+            }
+
+            super.onReceivedSslError(view, handler, error)
+        }
+
+        // NOTICE: Android WebView rejects the self-signed HTTPS cert used by the debug dev server.
+        // Keep this bypass debug-only and scoped to the configured dev server origin.
+        private fun shouldBypassDevServerCertificate(error: SslError?): Boolean {
+            val serverUrl = bridge.serverUrl?.takeUnless(String::isEmpty) ?: return false
+            val errorUrl = error?.url?.takeUnless(String::isEmpty) ?: return false
+
+            val serverUri = Uri.parse(serverUrl)
+            if (!serverUri.scheme.equals("https", ignoreCase = true)) {
+                return false
+            }
+
+            val errorUri = Uri.parse(errorUrl)
+            return serverUri.host.equals(errorUri.host, ignoreCase = true)
+                && normalizePort(serverUri) == normalizePort(errorUri)
+        }
+
+        private fun normalizePort(uri: Uri): Int =
+            uri.port.takeUnless { it == -1 }
+                ?: when (uri.scheme?.lowercase()) {
+                    "https" -> 443
+                    "http" -> 80
+                    else -> -1
+                }
+    }
+}
diff --git a/apps/stage-pocket/android/build.gradle b/apps/stage-pocket/android/build.gradle
index f8f0e43b6..74a1f0c86 100644
--- a/apps/stage-pocket/android/build.gradle
+++ b/apps/stage-pocket/android/build.gradle
@@ -9,6 +9,7 @@ buildscript {
     dependencies {
         classpath 'com.android.tools.build:gradle:8.13.0'
         classpath 'com.google.gms:google-services:4.4.4'
+        classpath 'org.jetbrains.kotlin:kotlin-gradle-plugin:2.2.21'
 
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files