diff --git a/app/src/main/java/com/cashpilot/android/ui/MainActivity.kt b/app/src/main/java/com/cashpilot/android/ui/MainActivity.kt
index 3574e63..7c47878 100644
--- a/app/src/main/java/com/cashpilot/android/ui/MainActivity.kt
+++ b/app/src/main/java/com/cashpilot/android/ui/MainActivity.kt
@@ -69,11 +69,12 @@ class MainActivity : ComponentActivity() {
                     val settings by viewModel.settings.collectAsState()
                     val hasNotif by viewModel.hasNotificationAccess.collectAsState()
                     val hasUsage by viewModel.hasUsageAccess.collectAsState()
+                    val hasBattery by viewModel.hasBatteryOptOut.collectAsState()
                     var showSettings by rememberSaveable { mutableStateOf(false) }
                     var setupDismissed by rememberSaveable { mutableStateOf(false) }
 
                     val needsSetup = !setupDismissed &&
-                        (settings.serverUrl.isBlank() || settings.apiKey.isBlank() || !hasNotif || !hasUsage)
+                        (settings.serverUrl.isBlank() || settings.apiKey.isBlank() || !hasNotif || !hasUsage || !hasBattery)
 
                     // Handle system Back from Settings → return to Dashboard
                     BackHandler(enabled = showSettings && !needsSetup) {
diff --git a/app/src/main/java/com/cashpilot/android/ui/MainViewModel.kt b/app/src/main/java/com/cashpilot/android/ui/MainViewModel.kt
index 52a13a2..59cb37e 100644
--- a/app/src/main/java/com/cashpilot/android/ui/MainViewModel.kt
+++ b/app/src/main/java/com/cashpilot/android/ui/MainViewModel.kt
@@ -2,6 +2,7 @@ package com.cashpilot.android.ui
 
 import android.app.AppOpsManager
 import android.app.Application
+import android.os.PowerManager
 import android.content.ComponentName
 import android.content.Context
 import android.os.Build
@@ -74,6 +75,9 @@ class MainViewModel(application: Application) : AndroidViewModel(application) {
     private val _hasUsageAccess = MutableStateFlow(false)
     val hasUsageAccess: StateFlow<Boolean> = _hasUsageAccess.asStateFlow()
 
+    private val _hasBatteryOptOut = MutableStateFlow(false)
+    val hasBatteryOptOut: StateFlow<Boolean> = _hasBatteryOptOut.asStateFlow()
+
     val lastHeartbeat: StateFlow<Long> = HeartbeatService.lastHeartbeat
     val lastHeartbeatFailed: StateFlow<Boolean> = HeartbeatService.lastHeartbeatFailed
 
@@ -225,5 +229,8 @@ class MainViewModel(application: Application) : AndroidViewModel(application) {
         } else {
             false
         }
+
+        val pm = ctx.getSystemService(Context.POWER_SERVICE) as? PowerManager
+        _hasBatteryOptOut.value = pm?.isIgnoringBatteryOptimizations(ctx.packageName) ?: false
     }
 }
diff --git a/app/src/main/java/com/cashpilot/android/ui/screen/SetupScreen.kt b/app/src/main/java/com/cashpilot/android/ui/screen/SetupScreen.kt
index 7d8d307..5ac0b70 100644
--- a/app/src/main/java/com/cashpilot/android/ui/screen/SetupScreen.kt
+++ b/app/src/main/java/com/cashpilot/android/ui/screen/SetupScreen.kt
@@ -20,6 +20,7 @@ import androidx.compose.material.icons.filled.CheckCircle
 import androidx.compose.material.icons.filled.ChevronRight
 import androidx.compose.material.icons.filled.Cloud
 import androidx.compose.material.icons.filled.Notifications
+import androidx.compose.material.icons.filled.BatteryAlert
 import androidx.compose.material.icons.filled.QueryStats
 import androidx.compose.material3.Button
 import androidx.compose.material3.Card
@@ -52,6 +53,7 @@ fun SetupScreen(viewModel: MainViewModel, onComplete: () -> Unit) {
     val settings by viewModel.settings.collectAsState()
     val hasNotif by viewModel.hasNotificationAccess.collectAsState()
     val hasUsage by viewModel.hasUsageAccess.collectAsState()
+    val hasBattery by viewModel.hasBatteryOptOut.collectAsState()
     val context = LocalContext.current
 
     var localUrl by rememberSaveable { mutableStateOf("") }
@@ -164,6 +166,23 @@ fun SetupScreen(viewModel: MainViewModel, onComplete: () -> Unit) {
                 }
             }
 
+            // Step 4: Battery optimization
+            SetupCard(
+                step = 4,
+                icon = Icons.Default.BatteryAlert,
+                title = stringResource(R.string.setup_battery_title),
+                description = stringResource(R.string.setup_battery_desc),
+                done = hasBattery,
+            ) {
+                TextButton(
+                    onClick = { openBatteryOptimizationSettings(context) },
+                ) {
+                    Text(stringResource(R.string.setup_grant_access))
+                    Spacer(Modifier.width(4.dp))
+                    Icon(Icons.Default.ChevronRight, null, Modifier.size(18.dp))
+                }
+            }
+
             Spacer(Modifier.height(8.dp))
 
             Button(
@@ -173,7 +192,7 @@ fun SetupScreen(viewModel: MainViewModel, onComplete: () -> Unit) {
                     onComplete()
                 },
                 modifier = Modifier.fillMaxWidth(),
-                enabled = serverDone && hasNotif && hasUsage,
+                enabled = serverDone && hasNotif && hasUsage && hasBattery,
             ) {
                 Text(stringResource(R.string.setup_continue))
             }
@@ -263,3 +282,10 @@ private fun openUsageAccessSettings(context: Context) {
             .addFlags(Intent.FLAG_ACTIVITY_NEW_TASK),
     )
 }
+
+private fun openBatteryOptimizationSettings(context: Context) {
+    context.startActivity(
+        Intent(AndroidSettings.ACTION_IGNORE_BATTERY_OPTIMIZATION_SETTINGS)
+            .addFlags(Intent.FLAG_ACTIVITY_NEW_TASK),
+    )
+}
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index 34eab1f..1e0d5e2 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -31,6 +31,8 @@
     <string name="setup_notif_desc">CashPilot reads foreground notifications to detect when passive income apps are running. No notification content is collected — only presence is checked.</string>
     <string name="setup_usage_title">Usage Access</string>
     <string name="setup_usage_desc">Allows CashPilot to check when apps were last active and measure per-app network usage. This data stays on your device and is only sent to your own server.</string>
+    <string name="setup_battery_title">Battery Optimization</string>
+    <string name="setup_battery_desc">Disable battery optimization so Android doesn\'t kill CashPilot\'s background service. Without this, heartbeats may stop when the screen is off.</string>
     <string name="setup_grant_access">Open Settings</string>
     <string name="setup_continue">Continue to Dashboard</string>
     <string name="setup_skip">Skip for now</string>