feat(watch): improve lap detection with CMDeviceMotion and low-pass filtering

src/navigation/MainTabNavigator.tsx

@@ -4,7 +4,7 @@ import { Ionicons } from "@expo/vector-icons";
 import { MainTabParamList } from "./types";
 import { WorkoutNavigator } from "./WorkoutNavigator";
 import { HistoryNavigator } from "./HistoryNavigator";
-import { SettingsScreen } from "../features/settings/screens/SettingsScreen";
+import { SettingsNavigator } from "./SettingsNavigator";
 
 const Tab = createBottomTabNavigator<MainTabParamList>();
 
@@ -45,8 +45,9 @@ export function MainTabNavigator() {
       />
       <Tab.Screen
         name="Settings"
-        component={SettingsScreen}
+        component={SettingsNavigator}
         options={{
+          headerShown: false,
           tabBarLabel: t("settings"),
           tabBarIcon: ({ color, size }) => (
             <Ionicons name="settings-outline" size={size} color={color} />

src/navigation/SettingsNavigator.tsx

@@ -0,0 +1,26 @@
+import { useTranslation } from "react-i18next";
+import { createNativeStackNavigator } from "@react-navigation/native-stack";
+import { SettingsStackParamList } from "./types";
+import { SettingsScreen } from "../features/settings/screens/SettingsScreen";
+
+const Stack = createNativeStackNavigator<SettingsStackParamList>();
+
+export function SettingsNavigator() {
+  const { t } = useTranslation("navigation");
+
+  return (
+    <Stack.Navigator
+      screenOptions={{
+        headerStyle: { backgroundColor: "#0ea5e9" },
+        headerTintColor: "#fff",
+        headerTitleStyle: { fontWeight: "bold" },
+      }}
+    >
+      <Stack.Screen
+        name="SettingsMain"
+        component={SettingsScreen}
+        options={{ title: t("settings") }}
+      />
+    </Stack.Navigator>
+  );
+}

src/navigation/types.ts

@@ -26,6 +26,10 @@ export type HistoryStackParamList = {
   SessionDetail: { sessionId: string };
 };
 
+export type SettingsStackParamList = {
+  SettingsMain: undefined;
+};
+
 export type RootStackProps<T extends keyof RootStackParamList> =
   NativeStackScreenProps<RootStackParamList, T>;
 

targets/watch/WorkoutManager.swift

@@ -393,32 +393,44 @@ class WorkoutManager: NSObject, ObservableObject, HKLiveWorkoutBuilderDelegate {
         healthStore.execute(query)
     }
 
-    // MARK: - Lap Detection (Accelerometer)
+    // MARK: - Lap Detection (CMDeviceMotion)
+
+    private var filteredUserAccel: Double = 0
+    private var filteredRotationX: Double = 0
+    private let filterAlpha: Double = 0.3
 
     private func startLapDetection() {
-        guard motionManager.isAccelerometerAvailable else { return }
-        motionManager.accelerometerUpdateInterval = 0.1 // 10 Hz
-        motionManager.startAccelerometerUpdates()
+        guard motionManager.isDeviceMotionAvailable else { return }
+        motionManager.deviceMotionUpdateInterval = 0.1 // 10 Hz
+        motionManager.startDeviceMotionUpdates(using: .xMagneticNorthZVertical)
 
         lapDetectionTimer = Timer.scheduledTimer(withTimeInterval: 0.2, repeats: true) { [weak self] _ in
-            self?.processAccelerometerData()
+            self?.processDeviceMotion()
         }
     }
 
     private func stopLapDetection() {
         lapDetectionTimer?.invalidate()
         lapDetectionTimer = nil
-        motionManager.stopAccelerometerUpdates()
+        motionManager.stopDeviceMotionUpdates()
     }
 
-    private func processAccelerometerData() {
-        guard let data = motionManager.accelerometerData else { return }
+    private func processDeviceMotion() {
+        guard let motion = motionManager.deviceMotion else { return }
 
-        let magnitude = sqrt(data.acceleration.x * data.acceleration.x +
-                             data.acceleration.y * data.acceleration.y +
-                             data.acceleration.z * data.acceleration.z)
+        // userAcceleration has gravity removed — clean movement signal
+        let rawUserAccel = sqrt(motion.userAcceleration.x * motion.userAcceleration.x +
+                                motion.userAcceleration.y * motion.userAcceleration.y +
+                                motion.userAcceleration.z * motion.userAcceleration.z)
 
-        let isStationary = magnitude < 1.1 // Near rest (~1g from gravity)
+        // Low-pass filter for smoothing
+        filteredUserAccel = filterAlpha * rawUserAccel + (1 - filterAlpha) * filteredUserAccel
+
+        // Rotation rate on x-axis detects the flip/turn at the wall
+        let rawRotationX = abs(motion.rotationRate.x)
+        filteredRotationX = filterAlpha * rawRotationX + (1 - filterAlpha) * filteredRotationX
+
+        let isStationary = filteredUserAccel < 0.05
         let now = Date()
 
         if isStationary {
@@ -439,7 +451,6 @@ class WorkoutManager: NSObject, ObservableObject, HKLiveWorkoutBuilderDelegate {
                         self.lapDetected = true
                         self.lastLapDetectionTime = now
                     }
-                    // Reset after detection
                     DispatchQueue.main.asyncAfter(deadline: .now() + 1.5) {
                         self.lapDetected = false
                     }