diff --git a/android/app/src/main/AndroidManifest.xml b/android/app/src/main/AndroidManifest.xml
index 280180f..312d428 100644
--- a/android/app/src/main/AndroidManifest.xml
+++ b/android/app/src/main/AndroidManifest.xml
@@ -6,9 +6,12 @@
     <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
     <uses-permission android:name="android.permission.FOREGROUND_SERVICE_MICROPHONE" />
     <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
+    <uses-permission android:name="android.permission.WAKE_LOCK" />
+    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
+    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
 
     <application
-        android:allowBackup="true"
+        android:allowBackup="false"
         android:icon="@drawable/ic_launcher"
         android:label="${launcherName}"
         android:supportsRtl="true"
diff --git a/android/app/src/main/java/com/pediatricscribe/twa/AudioRecordingService.java b/android/app/src/main/java/com/pediatricscribe/twa/AudioRecordingService.java
index 7084d6b..1f11f7a 100644
--- a/android/app/src/main/java/com/pediatricscribe/twa/AudioRecordingService.java
+++ b/android/app/src/main/java/com/pediatricscribe/twa/AudioRecordingService.java
@@ -3,21 +3,29 @@ package com.pediatricscribe.twa;
 import android.app.Notification;
 import android.app.NotificationChannel;
 import android.app.NotificationManager;
+import android.app.PendingIntent;
 import android.app.Service;
 import android.content.Intent;
 import android.os.Build;
 import android.os.IBinder;
+import android.os.PowerManager;
 
 import androidx.core.app.NotificationCompat;
 
 /**
  * Foreground service that keeps the app alive during audio recording.
+ * Acquires a partial wake lock to prevent CPU sleep during recording.
  * The TWA web app sends a message to start/stop this service when recording.
  */
 public class AudioRecordingService extends Service {
 
     private static final String CHANNEL_ID = "recording_channel";
     private static final int NOTIFICATION_ID = 1;
+    private static final String WAKE_LOCK_TAG = "PedScribe:AudioRecording";
+
+    public static final String ACTION_STOP = "com.pediatricscribe.twa.STOP_RECORDING";
+
+    private PowerManager.WakeLock wakeLock;
 
     @Override
     public void onCreate() {
@@ -27,12 +35,34 @@ public class AudioRecordingService extends Service {
 
     @Override
     public int onStartCommand(Intent intent, int flags, int startId) {
+        if (intent != null && ACTION_STOP.equals(intent.getAction())) {
+            stopSelf();
+            return START_NOT_STICKY;
+        }
+
+        // Acquire wake lock to keep CPU active during recording
+        PowerManager pm = (PowerManager) getSystemService(POWER_SERVICE);
+        if (pm != null) {
+            wakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, WAKE_LOCK_TAG);
+            wakeLock.acquire(60 * 60 * 1000L); // 1 hour max
+        }
+
+        // Stop action in notification
+        Intent stopIntent = new Intent(this, AudioRecordingService.class);
+        stopIntent.setAction(ACTION_STOP);
+        PendingIntent stopPending = PendingIntent.getService(
+                this, 0, stopIntent,
+                PendingIntent.FLAG_UPDATE_CURRENT | PendingIntent.FLAG_IMMUTABLE
+        );
+
         Notification notification = new NotificationCompat.Builder(this, CHANNEL_ID)
                 .setContentTitle("Pediatric AI Scribe")
                 .setContentText("Recording in progress...")
                 .setSmallIcon(android.R.drawable.ic_btn_speak_now)
                 .setPriority(NotificationCompat.PRIORITY_LOW)
                 .setOngoing(true)
+                .setCategory(NotificationCompat.CATEGORY_SERVICE)
+                .addAction(android.R.drawable.ic_media_pause, "Stop Recording", stopPending)
                 .build();
 
         startForeground(NOTIFICATION_ID, notification);
@@ -46,6 +76,10 @@ public class AudioRecordingService extends Service {
 
     @Override
     public void onDestroy() {
+        if (wakeLock != null && wakeLock.isHeld()) {
+            wakeLock.release();
+            wakeLock = null;
+        }
         stopForeground(true);
         super.onDestroy();
     }
@@ -58,6 +92,7 @@ public class AudioRecordingService extends Service {
                     NotificationManager.IMPORTANCE_LOW
             );
             channel.setDescription("Shows when audio recording is active");
+            channel.setShowBadge(false);
             NotificationManager manager = getSystemService(NotificationManager.class);
             if (manager != null) {
                 manager.createNotificationChannel(channel);
diff --git a/docker-compose.yml b/docker-compose.yml
index d37ba9f..96663ee 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -1,6 +1,6 @@
 services:
   pediatric-scribe:
-    image: danielonyejesi/pediatric-ai-scribe-v3:v8
+    image: danielonyejesi/pediatric-ai-scribe-v3:v9
     ports:
       - "3552:3000"
     env_file:
diff --git a/package.json b/package.json
index 818a67d..5ad6418 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "pediatric-ai-scribe",
-  "version": "8.0.0",
+  "version": "9.0.0",
   "description": "AI-powered pediatric clinical documentation platform",
   "main": "server.js",
   "scripts": {
diff --git a/public/.well-known/assetlinks.json b/public/.well-known/assetlinks.json
new file mode 100644
index 0000000..e7b5818
--- /dev/null
+++ b/public/.well-known/assetlinks.json
@@ -0,0 +1,12 @@
+[
+  {
+    "relation": ["delegate_permission/common.handle_all_urls"],
+    "target": {
+      "namespace": "android_app",
+      "package_name": "com.pediatricscribe.twa",
+      "sha256_cert_fingerprints": [
+        "TO_BE_REPLACED_WITH_YOUR_SIGNING_KEY_SHA256"
+      ]
+    }
+  }
+]
diff --git a/public/sw.js b/public/sw.js
index 6fb8090..a487324 100644
--- a/public/sw.js
+++ b/public/sw.js
@@ -1,22 +1,94 @@
-// Minimal service worker — pass everything through, cache nothing
-self.addEventListener('install', function() {
-  self.skipWaiting();
-});
+// ============================================================
+// SERVICE WORKER — Cache shell, network-first for API
+// Provides offline fallback for app shell while keeping
+// API calls always fresh (critical for medical data accuracy)
+// ============================================================
 
-self.addEventListener('activate', function(event) {
-  // Clear all old caches
+var CACHE_NAME = 'pedscribe-v11';
+var SHELL_ASSETS = [
+  '/',
+  '/index.html',
+  '/css/styles.css',
+  '/js/app.js',
+  '/js/auth.js',
+  '/manifest.json'
+];
+
+// Install: precache app shell
+self.addEventListener('install', function(event) {
   event.waitUntil(
-    caches.keys().then(function(names) {
-      return Promise.all(
-        names.map(function(name) { return caches.delete(name); })
-      );
+    caches.open(CACHE_NAME).then(function(cache) {
+      return cache.addAll(SHELL_ASSETS);
+    }).then(function() {
+      return self.skipWaiting();
     })
   );
 });
 
-self.addEventListener('fetch', function(event) {
-  // Only intercept same-origin requests — let external CDNs go through natively
-  if (event.request.url.startsWith(self.location.origin)) {
-    event.respondWith(fetch(event.request));
-  }
+// Activate: clear old caches
+self.addEventListener('activate', function(event) {
+  event.waitUntil(
+    caches.keys().then(function(names) {
+      return Promise.all(
+        names.filter(function(name) { return name !== CACHE_NAME; })
+             .map(function(name) { return caches.delete(name); })
+      );
+    }).then(function() {
+      return self.clients.claim();
+    })
+  );
+});
+
+// Fetch: network-first for API, cache-first for static assets
+self.addEventListener('fetch', function(event) {
+  var url = new URL(event.request.url);
+
+  // Only handle same-origin requests
+  if (url.origin !== self.location.origin) return;
+
+  // API calls — always network, never cache (medical data must be fresh)
+  if (url.pathname.startsWith('/api/')) {
+    event.respondWith(fetch(event.request));
+    return;
+  }
+
+  // Component HTML — network-first with cache fallback
+  if (url.pathname.startsWith('/components/')) {
+    event.respondWith(
+      fetch(event.request).then(function(response) {
+        var clone = response.clone();
+        caches.open(CACHE_NAME).then(function(cache) { cache.put(event.request, clone); });
+        return response;
+      }).catch(function() {
+        return caches.match(event.request);
+      })
+    );
+    return;
+  }
+
+  // Static assets (JS, CSS, icons) — stale-while-revalidate
+  if (url.pathname.match(/\.(js|css|png|ico|woff2?)$/)) {
+    event.respondWith(
+      caches.match(event.request).then(function(cached) {
+        var fetchPromise = fetch(event.request).then(function(response) {
+          var clone = response.clone();
+          caches.open(CACHE_NAME).then(function(cache) { cache.put(event.request, clone); });
+          return response;
+        }).catch(function() { return cached; });
+        return cached || fetchPromise;
+      })
+    );
+    return;
+  }
+
+  // HTML pages — network-first
+  event.respondWith(
+    fetch(event.request).then(function(response) {
+      var clone = response.clone();
+      caches.open(CACHE_NAME).then(function(cache) { cache.put(event.request, clone); });
+      return response;
+    }).catch(function() {
+      return caches.match(event.request) || caches.match('/index.html');
+    })
+  );
 });
diff --git a/server.js b/server.js
index 84ddbb2..479aece 100644
--- a/server.js
+++ b/server.js
@@ -88,6 +88,13 @@ app.use('/api/auth/resend-verification', rateLimit({
   standardHeaders: true, legacyHeaders: false
 }));
 
+// Serve .well-known/assetlinks.json for TWA verification (must be before static)
+app.get('/.well-known/assetlinks.json', (req, res) => {
+  res.setHeader('Content-Type', 'application/json');
+  res.setHeader('Cache-Control', 'public, max-age=86400');
+  res.sendFile(path.join(__dirname, 'public', '.well-known', 'assetlinks.json'));
+});
+
 app.use(loggingMiddleware);
 app.use(express.static(path.join(__dirname, 'public'), {
   setHeaders: (res, filePath) => {
@@ -134,7 +141,7 @@ app.get('/api/models', async (req, res) => {
 const { activeProvider } = require('./src/utils/ai');
 app.get('/api/health', (req, res) => {
   res.json({
-    status: 'running', version: '3.1.0', provider: activeProvider,
+    status: 'running', version: '9.0.0', provider: activeProvider,
     timestamp: new Date().toISOString(),
     openrouter: process.env.OPENROUTER_API_KEY ? 'configured' : 'missing',
     bedrock: process.env.AWS_BEDROCK_REGION ? 'configured' : 'not configured',
@@ -197,7 +204,7 @@ const PORT = process.env.PORT || 3000;
 server.listen(PORT, () => {
   console.log('');
   console.log('==========================================');
-  console.log('🏥 PEDIATRIC AI SCRIBE v3.1');
+  console.log('🏥 PEDIATRIC AI SCRIBE v9.0');
   console.log('==========================================');
   console.log('🌐 http://localhost:' + PORT);
   console.log('🤖 Provider: ' + activeProvider);
diff --git a/src/routes/adminConfig.js b/src/routes/adminConfig.js
index 15eae0d..1e5a2ad 100644
--- a/src/routes/adminConfig.js
+++ b/src/routes/adminConfig.js
@@ -257,9 +257,21 @@ router.put('/config/models/toggle', async function(req, res) {
       disabled = disabled.filter(function(id) { return id !== modelId; });
     } else {
       if (!disabled.includes(modelId)) disabled.push(modelId);
+
+      // Safety: prevent disabling all models
+      var { getAvailableModels } = require('../utils/models');
+      var allModels = getAvailableModels();
+      var customRaw = await db.getSetting('models.custom') || '[]';
+      var custom;
+      try { custom = JSON.parse(customRaw); } catch(e) { custom = []; }
+      var enabledCount = allModels.filter(function(m) { return !disabled.includes(m.id); }).length + custom.length;
+      if (enabledCount === 0) {
+        return res.status(400).json({ error: 'Cannot disable all models. At least one model must remain enabled.' });
+      }
     }
 
     await db.setSetting('models.disabled', JSON.stringify(disabled));
+    logger.audit(req.user.id, 'admin_model_toggle', (enabled ? 'Enabled' : 'Disabled') + ' model: ' + modelId, req, { category: 'admin' });
     res.json({ success: true });
   } catch (e) { res.status(500).json({ error: e.message }); }
 });
@@ -270,16 +282,34 @@ router.post('/config/models/custom', async function(req, res) {
     var { id, name, cost, category } = req.body;
     if (!id || !name) return res.status(400).json({ error: 'id and name required' });
 
+    // Validate model ID format (provider/model-name)
+    var trimmedId = id.trim();
+    if (trimmedId.length > 200) return res.status(400).json({ error: 'Model ID too long (max 200 chars)' });
+    if (!/^[a-zA-Z0-9._\-\/\:]+$/.test(trimmedId)) {
+      return res.status(400).json({ error: 'Invalid model ID format. Use only letters, numbers, dots, dashes, slashes, and colons.' });
+    }
+
+    // Check if model ID conflicts with a built-in model
+    var { OPENROUTER_MODELS, BEDROCK_MODELS, AZURE_MODELS } = require('../utils/models');
+    var allBuiltIn = [].concat(OPENROUTER_MODELS, BEDROCK_MODELS, AZURE_MODELS);
+    if (allBuiltIn.find(function(m) { return m.id === trimmedId; })) {
+      return res.status(400).json({ error: 'Model ID conflicts with a built-in model. Use the toggle to enable/disable built-in models.' });
+    }
+
+    var validCategories = ['free', 'fast', 'smart', 'premium'];
+    var cat = validCategories.includes(category) ? category : 'smart';
+
     var customRaw = await db.getSetting('models.custom') || '[]';
     var custom;
     try { custom = JSON.parse(customRaw); } catch(e) { custom = []; }
 
     // Prevent duplicates
-    custom = custom.filter(function(m) { return m.id !== id; });
-    custom.push({ id: id.trim(), name: name.trim(), cost: cost || '?', category: category || 'smart', tag: 'CUSTOM' });
+    var existing = custom.find(function(m) { return m.id === trimmedId; });
+    custom = custom.filter(function(m) { return m.id !== trimmedId; });
+    custom.push({ id: trimmedId, name: name.trim().substring(0, 100), cost: (cost || '?').substring(0, 20), category: cat, tag: 'CUSTOM' });
 
     await db.setSetting('models.custom', JSON.stringify(custom));
-    logger.audit(req.user.id, 'admin_model_add', 'Added custom model: ' + id, req, { category: 'admin' });
+    logger.audit(req.user.id, existing ? 'admin_model_update' : 'admin_model_add', (existing ? 'Updated' : 'Added') + ' custom model: ' + trimmedId, req, { category: 'admin' });
     res.json({ success: true });
   } catch (e) { res.status(500).json({ error: e.message }); }
 });