diff --git a/app/src/main/java/com/freshkeeper/MainActivity.kt b/app/src/main/java/com/freshkeeper/MainActivity.kt
index ca0d70e..43a9955 100644
--- a/app/src/main/java/com/freshkeeper/MainActivity.kt
+++ b/app/src/main/java/com/freshkeeper/MainActivity.kt
@@ -6,10 +6,12 @@ import android.os.Bundle
 import android.widget.Toast
 import androidx.activity.compose.setContent
 import androidx.activity.enableEdgeToEdge
+import androidx.compose.runtime.LaunchedEffect
 import androidx.core.view.WindowCompat
 import androidx.fragment.app.FragmentActivity
 import androidx.navigation.NavHostController
 import androidx.navigation.compose.rememberNavController
+import com.freshkeeper.model.Screen
 import com.freshkeeper.service.AssetFileManager
 import com.freshkeeper.service.DeepLinkHandler
 import com.freshkeeper.service.NetworkManager
@@ -31,7 +33,6 @@ class MainActivity : FragmentActivity() {
     private lateinit var sharedPreferences: SharedPreferences
     private var navController: NavHostController? = null
     private lateinit var updateManager: UpdateManager
-    private val currentUserId = Firebase.auth.currentUser?.uid
 
     override fun onCreate(savedInstanceState: Bundle?) {
         enableEdgeToEdge()
@@ -54,10 +55,14 @@ class MainActivity : FragmentActivity() {
 
         val notificationManager = NotificationManager(this)
         notificationManager.setupNotificationChannel()
-        notificationManager.scheduleReminderIfEnabled(
-            currentUserId,
-            FirebaseFirestore.getInstance(),
-        )
+
+        val currentUserId = Firebase.auth.currentUser?.uid
+        if (currentUserId != null) {
+            notificationManager.scheduleReminderIfEnabled(
+                currentUserId,
+                FirebaseFirestore.getInstance(),
+            )
+        }
 
         val networkManager = NetworkManager(this)
 
@@ -80,6 +85,13 @@ class MainActivity : FragmentActivity() {
                 saveLanguageToPreferences(languageCode)
                 updateLocale(languageCode)
             }
+
+            LaunchedEffect(Unit) {
+                if (currentUserId == null && navController?.currentDestination?.route != Screen.SignIn.route) {
+                    navController?.navigate(Screen.SignIn.route)
+                }
+            }
+
             if (!networkManager.isNetworkAvailable()) {
                 Toast.makeText(this, "Please connect to the internet", Toast.LENGTH_LONG).show()
             }