diff --git a/app/src/main/java/cn/airnan/a2fair/A2FairApplication.kt b/app/src/main/java/cn/airnan/a2fair/A2FairApplication.kt
index f0d16cf..1a08e25 100644
--- a/app/src/main/java/cn/airnan/a2fair/A2FairApplication.kt
+++ b/app/src/main/java/cn/airnan/a2fair/A2FairApplication.kt
@@ -65,7 +65,7 @@ class A2FairApplication : Application() {
         tokenRepository = TokenRepository(database.tokenDao(), database.groupDao())
         settingsRepository = SettingsRepository(this, cryptoManager)
         
-        appLockManager = AppLockManager(settingsRepository)
+        appLockManager = AppLockManager(this, settingsRepository)
         ProcessLifecycleOwner.get().lifecycle.addObserver(appLockManager)
         
         backupManager = BackupManager(this, tokenRepository, cryptoManager)
diff --git a/app/src/main/java/cn/airnan/a2fair/MainActivity.kt b/app/src/main/java/cn/airnan/a2fair/MainActivity.kt
index 0d09c72..f05480f 100644
--- a/app/src/main/java/cn/airnan/a2fair/MainActivity.kt
+++ b/app/src/main/java/cn/airnan/a2fair/MainActivity.kt
@@ -5,7 +5,6 @@ import android.content.res.Configuration
 import android.os.Build
 import android.os.Bundle
 import android.view.WindowManager
-import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
 import androidx.activity.enableEdgeToEdge
 import androidx.compose.foundation.layout.fillMaxSize
@@ -13,6 +12,7 @@ import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
 import androidx.compose.ui.Modifier
 import androidx.datastore.preferences.core.intPreferencesKey
+import androidx.fragment.app.FragmentActivity
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import cn.airnan.a2fair.data.repository.dataStore
 import cn.airnan.a2fair.ui.navigation.AppNavigation
@@ -22,7 +22,7 @@ import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.runBlocking
 import java.util.Locale
 
-class MainActivity : ComponentActivity() {
+class MainActivity : FragmentActivity() {
 
     override fun attachBaseContext(newBase: Context) {
         val languageCode = try {
@@ -91,4 +91,4 @@ class MainActivity : ComponentActivity() {
             }
         }
     }
-}
\ No newline at end of file
+}
diff --git a/app/src/main/java/cn/airnan/a2fair/core/security/AppLockManager.kt b/app/src/main/java/cn/airnan/a2fair/core/security/AppLockManager.kt
index 1f6ce40..8b15c3c 100644
--- a/app/src/main/java/cn/airnan/a2fair/core/security/AppLockManager.kt
+++ b/app/src/main/java/cn/airnan/a2fair/core/security/AppLockManager.kt
@@ -1,37 +1,144 @@
 package cn.airnan.a2fair.core.security
 
+import android.content.BroadcastReceiver
+import android.content.Context
+import android.content.Intent
+import android.content.IntentFilter
 import androidx.lifecycle.DefaultLifecycleObserver
 import androidx.lifecycle.LifecycleOwner
 import cn.airnan.a2fair.data.repository.SettingsRepository
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.flow.collect
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.launch
 
-class AppLockManager(private val settingsRepository: SettingsRepository) : DefaultLifecycleObserver {
+class AppLockManager(
+    context: Context,
+    private val settingsRepository: SettingsRepository
+) : DefaultLifecycleObserver {
+    private val appContext = context.applicationContext
+    private val scope = CoroutineScope(SupervisorJob() + Dispatchers.Main.immediate)
+
     private val _isLocked = MutableStateFlow(false)
     val isLocked: StateFlow<Boolean> = _isLocked.asStateFlow()
 
-    private val scope = CoroutineScope(Dispatchers.Main)
+    private var pendingLockJob: Job? = null
+    private var lockDeadlineAtMillis: Long? = null
 
-    fun lock() {
-        scope.launch {
-            val isPinEnabled = settingsRepository.isPinEnabled.first()
-            if (isPinEnabled) {
-                _isLocked.value = true
+    private val screenOffReceiver = object : BroadcastReceiver() {
+        override fun onReceive(context: Context?, intent: Intent?) {
+            if (intent?.action == Intent.ACTION_SCREEN_OFF) {
+                scheduleLock()
             }
         }
     }
 
+    init {
+        appContext.registerReceiver(screenOffReceiver, IntentFilter(Intent.ACTION_SCREEN_OFF))
+        observeSettings()
+    }
+
+    fun lock() {
+        pendingLockJob?.cancel()
+        pendingLockJob = null
+        lockDeadlineAtMillis = null
+        scope.launch {
+            val appLockSettings = settingsRepository.appLockSettings.first()
+            _isLocked.value = appLockSettings.isAppLockEnabled
+        }
+    }
+
     fun unlock() {
+        pendingLockJob?.cancel()
+        pendingLockJob = null
+        lockDeadlineAtMillis = null
         _isLocked.value = false
     }
 
+    override fun onStart(owner: LifecycleOwner) {
+        super.onStart(owner)
+        scope.launch {
+            refreshLockStateWhenForegrounded()
+        }
+    }
+
     override fun onStop(owner: LifecycleOwner) {
         super.onStop(owner)
-        lock()
+        scheduleLock()
+    }
+
+    private fun observeSettings() {
+        scope.launch {
+            settingsRepository.appLockSettings.collect { settings ->
+                if (!settings.isAppLockEnabled) {
+                    pendingLockJob?.cancel()
+                    pendingLockJob = null
+                    lockDeadlineAtMillis = null
+                    _isLocked.value = false
+                }
+            }
+        }
+    }
+
+    private fun scheduleLock() {
+        pendingLockJob?.cancel()
+        pendingLockJob = null
+
+        scope.launch {
+            val appLockSettings = settingsRepository.appLockSettings.first()
+            if (!appLockSettings.isAppLockEnabled) {
+                lockDeadlineAtMillis = null
+                _isLocked.value = false
+                return@launch
+            }
+
+            val delayMillis = appLockSettings.lockTrigger.delayMillis
+            if (delayMillis <= 0L) {
+                lockDeadlineAtMillis = null
+                _isLocked.value = true
+                return@launch
+            }
+
+            val deadline = System.currentTimeMillis() + delayMillis
+            lockDeadlineAtMillis = deadline
+            pendingLockJob = scope.launch {
+                delay(delayMillis)
+                val latestSettings = settingsRepository.appLockSettings.first()
+                if (latestSettings.isAppLockEnabled && lockDeadlineAtMillis == deadline) {
+                    _isLocked.value = true
+                }
+            }
+        }
+    }
+
+    private suspend fun refreshLockStateWhenForegrounded() {
+        val appLockSettings = settingsRepository.appLockSettings.first()
+        if (!appLockSettings.isAppLockEnabled) {
+            unlock()
+            return
+        }
+
+        val deadline = lockDeadlineAtMillis
+        if (deadline == null) {
+            return
+        }
+
+        if (System.currentTimeMillis() >= deadline) {
+            pendingLockJob?.cancel()
+            pendingLockJob = null
+            lockDeadlineAtMillis = null
+            _isLocked.value = true
+        } else {
+            pendingLockJob?.cancel()
+            pendingLockJob = null
+            lockDeadlineAtMillis = null
+        }
     }
 }
diff --git a/app/src/main/java/cn/airnan/a2fair/core/security/PinPolicy.kt b/app/src/main/java/cn/airnan/a2fair/core/security/PinPolicy.kt
new file mode 100644
index 0000000..61a4726
--- /dev/null
+++ b/app/src/main/java/cn/airnan/a2fair/core/security/PinPolicy.kt
@@ -0,0 +1,7 @@
+package cn.airnan.a2fair.core.security
+
+const val PIN_LENGTH = 6
+
+private val PinRegex = Regex("^\\d{$PIN_LENGTH}$")
+
+fun String.isValidPin(): Boolean = PinRegex.matches(this)
diff --git a/app/src/main/java/cn/airnan/a2fair/data/repository/SettingsRepository.kt b/app/src/main/java/cn/airnan/a2fair/data/repository/SettingsRepository.kt
index 99b20a6..8042071 100644
--- a/app/src/main/java/cn/airnan/a2fair/data/repository/SettingsRepository.kt
+++ b/app/src/main/java/cn/airnan/a2fair/data/repository/SettingsRepository.kt
@@ -9,26 +9,60 @@ import androidx.datastore.preferences.core.intPreferencesKey
 import androidx.datastore.preferences.core.longPreferencesKey
 import androidx.datastore.preferences.core.stringPreferencesKey
 import androidx.datastore.preferences.preferencesDataStore
+import cn.airnan.a2fair.core.security.isValidPin
 import cn.airnan.a2fair.crypto.CryptoManager
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.flow.SharedFlow
+import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.map
 
 val Context.dataStore: DataStore<Preferences> by preferencesDataStore(name = "settings")
 
+enum class AppLockTrigger(val preferenceValue: Int, val delayMillis: Long) {
+    IMMEDIATELY(0, 0L),
+    AFTER_1_MINUTE(1, 60_000L),
+    AFTER_3_MINUTES(2, 3 * 60_000L),
+    AFTER_5_MINUTES(3, 5 * 60_000L);
+
+    companion object {
+        val DEFAULT = IMMEDIATELY
+
+        fun fromPreferenceValue(value: Int): AppLockTrigger {
+            return entries.firstOrNull { it.preferenceValue == value } ?: DEFAULT
+        }
+    }
+}
+
+data class AppLockSettings(
+    val isPinEnabled: Boolean = false,
+    val hasPinCode: Boolean = false,
+    val isBiometricEnabled: Boolean = false,
+    val lockTrigger: AppLockTrigger = AppLockTrigger.DEFAULT
+) {
+    val isAppLockEnabled: Boolean
+        get() = isPinEnabled && hasPinCode
+
+    val canUseBiometric: Boolean
+        get() = isAppLockEnabled && isBiometricEnabled
+}
+
 class SettingsRepository(private val context: Context, private val cryptoManager: CryptoManager) {
 
     private val dataStore = context.dataStore
 
-    val isPinEnabled: Flow<Boolean> = dataStore.data.map { preferences ->
+    private val storedPinEnabled: Flow<Boolean> = dataStore.data.map { preferences ->
         preferences[PreferencesKeys.PIN_ENABLED] ?: false
     }
 
-    suspend fun setPinEnabled(enabled: Boolean) {
-        dataStore.edit { preferences ->
-            preferences[PreferencesKeys.PIN_ENABLED] = enabled
-        }
+    private val storedBiometricEnabled: Flow<Boolean> = dataStore.data.map { preferences ->
+        preferences[PreferencesKeys.BIOMETRIC_ENABLED] ?: false
+    }
+
+    private val storedLockTrigger: Flow<AppLockTrigger> = dataStore.data.map { preferences ->
+        AppLockTrigger.fromPreferenceValue(
+            preferences[PreferencesKeys.APP_LOCK_TRIGGER] ?: AppLockTrigger.DEFAULT.preferenceValue
+        )
     }
 
     val pinCode: Flow<String?> = dataStore.data.map { preferences ->
@@ -44,23 +78,87 @@ class SettingsRepository(private val context: Context, private val cryptoManager
         }
     }
 
+    val appLockSettings: Flow<AppLockSettings> = combine(
+        storedPinEnabled,
+        pinCode,
+        storedBiometricEnabled,
+        storedLockTrigger
+    ) { pinEnabled, decryptedPinCode, biometricEnabled, lockTrigger ->
+        val hasPinCode = decryptedPinCode?.isValidPin() == true
+        val isAppLockEnabled = pinEnabled && hasPinCode
+        AppLockSettings(
+            isPinEnabled = isAppLockEnabled,
+            hasPinCode = hasPinCode,
+            isBiometricEnabled = isAppLockEnabled && biometricEnabled,
+            lockTrigger = lockTrigger
+        )
+    }
+
+    val isPinEnabled: Flow<Boolean> = appLockSettings.map { settings ->
+        settings.isPinEnabled
+    }
+
+    suspend fun setPinEnabled(enabled: Boolean) {
+        if (!enabled) {
+            disablePin()
+            return
+        }
+
+        dataStore.edit { preferences ->
+            preferences[PreferencesKeys.PIN_ENABLED] = true
+        }
+    }
+
     suspend fun setPinCode(pin: String?) {
+        require(pin == null || pin.isValidPin()) { "PIN must be exactly 6 digits." }
         dataStore.edit { preferences ->
             if (pin == null) {
                 preferences.remove(PreferencesKeys.PIN_CODE)
+                preferences[PreferencesKeys.PIN_ENABLED] = false
+                preferences[PreferencesKeys.BIOMETRIC_ENABLED] = false
             } else {
                 preferences[PreferencesKeys.PIN_CODE] = cryptoManager.encrypt(pin)
             }
         }
     }
 
-    val isBiometricEnabled: Flow<Boolean> = dataStore.data.map { preferences ->
-        preferences[PreferencesKeys.BIOMETRIC_ENABLED] ?: false
+    suspend fun enablePin(pin: String) {
+        require(pin.isValidPin()) { "PIN must be exactly 6 digits." }
+        dataStore.edit { preferences ->
+            preferences[PreferencesKeys.PIN_CODE] = cryptoManager.encrypt(pin)
+            preferences[PreferencesKeys.PIN_ENABLED] = true
+        }
+    }
+
+    suspend fun disablePin() {
+        dataStore.edit { preferences ->
+            preferences[PreferencesKeys.PIN_ENABLED] = false
+            preferences[PreferencesKeys.BIOMETRIC_ENABLED] = false
+            preferences.remove(PreferencesKeys.PIN_CODE)
+            preferences[PreferencesKeys.FAILED_ATTEMPTS] = 0
+            preferences[PreferencesKeys.LOCKOUT_END_TIME] = 0L
+        }
+    }
+
+    val isBiometricEnabled: Flow<Boolean> = appLockSettings.map { settings ->
+        settings.isBiometricEnabled
     }
 
     suspend fun setBiometricEnabled(enabled: Boolean) {
         dataStore.edit { preferences ->
-            preferences[PreferencesKeys.BIOMETRIC_ENABLED] = enabled
+            val hasPinCode = preferences[PreferencesKeys.PIN_CODE] != null
+            val isPinEnabled = preferences[PreferencesKeys.PIN_ENABLED] ?: false
+            preferences[PreferencesKeys.BIOMETRIC_ENABLED] = enabled && hasPinCode && isPinEnabled
+        }
+    }
+
+    val appLockTrigger: Flow<AppLockTrigger> = appLockSettings.map { settings ->
+        settings.lockTrigger
+    }
+
+    suspend fun setAppLockTrigger(trigger: AppLockTrigger) {
+        dataStore.edit { preferences ->
+            preferences[PreferencesKeys.APP_LOCK_TRIGGER] = trigger.preferenceValue
         }
     }
 
@@ -145,6 +243,7 @@ class SettingsRepository(private val context: Context, private val cryptoManager
         val FLAG_SECURE_ENABLED = booleanPreferencesKey("flag_secure_enabled")
         val FAILED_ATTEMPTS = intPreferencesKey("failed_attempts")
         val LOCKOUT_END_TIME = longPreferencesKey("lockout_end_time")
+        val APP_LOCK_TRIGGER = intPreferencesKey("app_lock_trigger")
         val THEME_MODE = intPreferencesKey("theme_mode")
         val DYNAMIC_COLOR = booleanPreferencesKey("dynamic_color")
         val SEED_COLOR = intPreferencesKey("seed_color")
diff --git a/app/src/main/java/cn/airnan/a2fair/ui/settings/security/BiometricAuth.kt b/app/src/main/java/cn/airnan/a2fair/ui/settings/security/BiometricAuth.kt
new file mode 100644
index 0000000..6681dff
--- /dev/null
+++ b/app/src/main/java/cn/airnan/a2fair/ui/settings/security/BiometricAuth.kt
@@ -0,0 +1,135 @@
+package cn.airnan.a2fair.ui.settings.security
+
+import android.content.Context
+import android.content.ContextWrapper
+import androidx.annotation.StringRes
+import androidx.biometric.BiometricManager
+import androidx.biometric.BiometricPrompt
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
+import androidx.core.content.ContextCompat
+import androidx.fragment.app.FragmentActivity
+import cn.airnan.a2fair.R
+
+enum class BiometricAuthMode(val authenticators: Int) {
+    BiometricOnly(BiometricManager.Authenticators.BIOMETRIC_STRONG),
+    AppConfirmation(
+        BiometricManager.Authenticators.BIOMETRIC_STRONG or
+            BiometricManager.Authenticators.DEVICE_CREDENTIAL
+    )
+}
+
+sealed interface BiometricAuthResult {
+    object Success : BiometricAuthResult
+    object Failed : BiometricAuthResult
+    object Cancelled : BiometricAuthResult
+    data class Unavailable(@StringRes val messageRes: Int) : BiometricAuthResult
+}
+
+class BiometricAuthenticator(private val context: Context) {
+
+    fun getAvailability(mode: BiometricAuthMode): BiometricAuthResult? {
+        val activity = context.findFragmentActivity()
+            ?: return BiometricAuthResult.Unavailable(R.string.biometric_not_available_on_this_screen)
+
+        return when (BiometricManager.from(activity).canAuthenticate(mode.authenticators)) {
+            BiometricManager.BIOMETRIC_SUCCESS -> null
+            BiometricManager.BIOMETRIC_ERROR_NO_HARDWARE -> {
+                BiometricAuthResult.Unavailable(R.string.biometric_error_no_hardware)
+            }
+            BiometricManager.BIOMETRIC_ERROR_HW_UNAVAILABLE -> {
+                BiometricAuthResult.Unavailable(R.string.biometric_error_hw_unavailable)
+            }
+            BiometricManager.BIOMETRIC_ERROR_NONE_ENROLLED -> {
+                BiometricAuthResult.Unavailable(
+                    if (mode == BiometricAuthMode.BiometricOnly) {
+                        R.string.biometric_error_none_enrolled
+                    } else {
+                        R.string.security_verification_unavailable
+                    }
+                )
+            }
+            else -> BiometricAuthResult.Unavailable(R.string.biometric_error_unavailable)
+        }
+    }
+
+    fun authenticate(
+        mode: BiometricAuthMode,
+        @StringRes titleRes: Int,
+        @StringRes subtitleRes: Int,
+        onResult: (BiometricAuthResult) -> Unit
+    ) {
+        val activity = context.findFragmentActivity()
+        if (activity == null) {
+            onResult(BiometricAuthResult.Unavailable(R.string.biometric_not_available_on_this_screen))
+            return
+        }
+
+        val availability = getAvailability(mode)
+        if (availability != null) {
+            onResult(availability)
+            return
+        }
+
+        val executor = ContextCompat.getMainExecutor(activity)
+        val prompt = BiometricPrompt(
+            activity,
+            executor,
+            object : BiometricPrompt.AuthenticationCallback() {
+                override fun onAuthenticationError(errorCode: Int, errString: CharSequence) {
+                    super.onAuthenticationError(errorCode, errString)
+                    if (errorCode in cancellationErrorCodes) {
+                        onResult(BiometricAuthResult.Cancelled)
+                    } else {
+                        onResult(BiometricAuthResult.Failed)
+                    }
+                }
+
+                override fun onAuthenticationSucceeded(result: BiometricPrompt.AuthenticationResult) {
+                    super.onAuthenticationSucceeded(result)
+                    onResult(BiometricAuthResult.Success)
+                }
+
+                override fun onAuthenticationFailed() {
+                    super.onAuthenticationFailed()
+                    onResult(BiometricAuthResult.Failed)
+                }
+            }
+        )
+
+        val builder = BiometricPrompt.PromptInfo.Builder()
+            .setTitle(activity.getString(titleRes))
+            .setSubtitle(activity.getString(subtitleRes))
+            .setAllowedAuthenticators(mode.authenticators)
+
+        // BiometricOnly (without DEVICE_CREDENTIAL) requires a negative button text
+        if (mode == BiometricAuthMode.BiometricOnly) {
+            builder.setNegativeButtonText(activity.getString(R.string.cancel))
+        }
+
+        val promptInfo = builder.build()
+
+        prompt.authenticate(promptInfo)
+    }
+
+    private companion object {
+        val cancellationErrorCodes = setOf(
+            BiometricPrompt.ERROR_NEGATIVE_BUTTON,
+            BiometricPrompt.ERROR_USER_CANCELED,
+            BiometricPrompt.ERROR_CANCELED,
+            BiometricPrompt.ERROR_TIMEOUT
+        )
+    }
+}
+
+@Composable
+fun rememberBiometricAuthenticator(): BiometricAuthenticator {
+    val context = androidx.compose.ui.platform.LocalContext.current
+    return remember(context) { BiometricAuthenticator(context) }
+}
+
+private tailrec fun Context.findFragmentActivity(): FragmentActivity? = when (this) {
+    is FragmentActivity -> this
+    is ContextWrapper -> baseContext.findFragmentActivity()
+    else -> null
+}
diff --git a/app/src/main/java/cn/airnan/a2fair/ui/settings/security/LockScreen.kt b/app/src/main/java/cn/airnan/a2fair/ui/settings/security/LockScreen.kt
index 452f30f..ddc300c 100644
--- a/app/src/main/java/cn/airnan/a2fair/ui/settings/security/LockScreen.kt
+++ b/app/src/main/java/cn/airnan/a2fair/ui/settings/security/LockScreen.kt
@@ -1,8 +1,5 @@
 package cn.airnan.a2fair.ui.settings.security
 
-import android.widget.Toast
-import androidx.biometric.BiometricManager
-import androidx.biometric.BiometricPrompt
 import androidx.compose.foundation.layout.*
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.Fingerprint
@@ -11,16 +8,12 @@ import androidx.compose.material3.*
 import androidx.compose.runtime.*
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
-import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.res.stringResource
-import androidx.compose.ui.text.input.PasswordVisualTransformation
 import androidx.compose.ui.unit.dp
-import androidx.core.content.ContextCompat
-import androidx.fragment.app.FragmentActivity
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
-import cn.airnan.a2fair.A2FairApplication
 import cn.airnan.a2fair.R
-import kotlinx.coroutines.flow.first
+import cn.airnan.a2fair.A2FairApplication
+import cn.airnan.a2fair.core.security.PIN_LENGTH
 import kotlinx.coroutines.launch
 
 @Composable
@@ -28,24 +21,29 @@ fun LockScreen(
     onUnlock: () -> Unit,
     modifier: Modifier = Modifier
 ) {
-    val context = LocalContext.current
-    val app = context.applicationContext as A2FairApplication
+    val app = androidx.compose.ui.platform.LocalContext.current.applicationContext as A2FairApplication
     val settingsRepo = app.settingsRepository
-    
-    val isBiometricEnabled by settingsRepo.isBiometricEnabled.collectAsStateWithLifecycle(initialValue = false)
+    val biometricAuthenticator = rememberBiometricAuthenticator()
+
+    val appLockSettings by settingsRepo.appLockSettings.collectAsStateWithLifecycle(
+        initialValue = cn.airnan.a2fair.data.repository.AppLockSettings()
+    )
     val pinCode by settingsRepo.pinCode.collectAsStateWithLifecycle(initialValue = null)
-    
+
+    val isBiometricEnabled = appLockSettings.canUseBiometric
+
     val failedAttempts by settingsRepo.failedAttempts.collectAsStateWithLifecycle(initialValue = 0)
     val lockoutEndTime by settingsRepo.lockoutEndTime.collectAsStateWithLifecycle(initialValue = 0L)
-    
+
     var enteredPin by remember { mutableStateOf("") }
     var errorMessage by remember { mutableStateOf<String?>(null) }
     val incorrectPinMsg = stringResource(R.string.incorrect_pin)
+    val pinHintMsg = stringResource(R.string.pin_digits_hint)
     var remainingLockOutTime by remember { mutableStateOf(0L) }
-    
+
     val scope = rememberCoroutineScope()
     val biometricFailedMsg = stringResource(R.string.biometric_failed)
-    
+
     LaunchedEffect(lockoutEndTime) {
         while (true) {
             val now = System.currentTimeMillis()
@@ -62,12 +60,40 @@ fun LockScreen(
         }
     }
     
-    // Auto prompt biometric if enabled
     LaunchedEffect(isBiometricEnabled) {
         if (isBiometricEnabled) {
-            showBiometricPrompt(context as FragmentActivity, onUnlock, onFailed = {
-                errorMessage = biometricFailedMsg
-            })
+            biometricAuthenticator.authenticate(
+                mode = BiometricAuthMode.AppConfirmation,
+                titleRes = R.string.unlock_2fair,
+                subtitleRes = R.string.biometric_prompt_subtitle
+            ) { result ->
+                when (result) {
+                    BiometricAuthResult.Success -> onUnlock()
+                    BiometricAuthResult.Failed -> errorMessage = biometricFailedMsg
+                    else -> Unit
+                }
+            }
+        }
+    }
+
+    fun submitPin(candidate: String) {
+        if (pinCode != null && candidate == pinCode) {
+            scope.launch {
+                settingsRepo.setFailedAttempts(0)
+                settingsRepo.setLockoutEndTime(0L)
+            }
+            onUnlock()
+        } else {
+            val newAttempts = failedAttempts + 1
+            errorMessage = incorrectPinMsg
+            enteredPin = ""
+            scope.launch {
+                settingsRepo.setFailedAttempts(newAttempts)
+                if (newAttempts >= 5) {
+                    val lockoutTime = System.currentTimeMillis() + 30000L
+                    settingsRepo.setLockoutEndTime(lockoutTime)
+                }
+            }
         }
     }
 
@@ -92,125 +118,88 @@ fun LockScreen(
                 style = MaterialTheme.typography.headlineSmall
             )
             Spacer(modifier = Modifier.height(16.dp))
-            
-            OutlinedTextField(
-                value = enteredPin,
-                onValueChange = { 
-                    enteredPin = it
-                    errorMessage = null
-                },
-                visualTransformation = PasswordVisualTransformation(),
-                singleLine = true,
-                isError = errorMessage != null,
+
+            PinIndicatorRow(
+                filledCount = enteredPin.length,
+                isError = errorMessage != null || remainingLockOutTime > 0L,
                 modifier = Modifier.fillMaxWidth(0.8f)
             )
-            
-            if (errorMessage != null) {
-                Text(
-                    text = errorMessage!!,
-                    color = MaterialTheme.colorScheme.error,
-                    style = MaterialTheme.typography.bodySmall,
-                    modifier = Modifier.padding(top = 4.dp)
-                )
-            }
-            
-            if (remainingLockOutTime > 0) {
+            Spacer(modifier = Modifier.height(12.dp))
 
-                Text(
-                    text = stringResource(R.string.try_again_in, remainingLockOutTime),
-                    color = MaterialTheme.colorScheme.error,
-                    style = MaterialTheme.typography.bodyMedium,
-                    modifier = Modifier.padding(top = 8.dp)
-                )
-            }
-            
-            Spacer(modifier = Modifier.height(24.dp))
-            
-            Row(
-                modifier = Modifier.fillMaxWidth(0.8f),
-                horizontalArrangement = Arrangement.SpaceBetween,
-                verticalAlignment = Alignment.CenterVertically
-            ) {
-                if (isBiometricEnabled && remainingLockOutTime == 0L) {
-                    IconButton(onClick = {
-                        showBiometricPrompt(context as FragmentActivity, onUnlock, onFailed = {
-                            errorMessage = biometricFailedMsg
-                        })
-                    }) {
-                        Icon(
-                            imageVector = Icons.Default.Fingerprint,
-                            contentDescription = stringResource(R.string.use_biometric),
-                            modifier = Modifier.size(48.dp)
-                        )
-                    }
+            Text(
+                text = when {
+                    remainingLockOutTime > 0L -> stringResource(R.string.try_again_in, remainingLockOutTime)
+                    errorMessage != null -> errorMessage!!
+                    enteredPin.isEmpty() -> pinHintMsg
+                    else -> stringResource(R.string.pin_digits_remaining, PIN_LENGTH - enteredPin.length)
+                },
+                color = if (errorMessage != null || remainingLockOutTime > 0L) {
+                    MaterialTheme.colorScheme.error
                 } else {
-                    Spacer(modifier = Modifier.width(48.dp))
-                }
-                
-                Button(
+                    MaterialTheme.colorScheme.onSurfaceVariant
+                },
+                style = MaterialTheme.typography.bodyMedium
+            )
+            Spacer(modifier = Modifier.height(24.dp))
+
+            PinNumberPad(
+                resetLabel = stringResource(R.string.clear_pin_input),
+                deleteLabel = stringResource(R.string.delete_digit),
+                onDigit = { digit ->
+                    if (remainingLockOutTime > 0L || enteredPin.length >= PIN_LENGTH) {
+                        return@PinNumberPad
+                    }
+                    val updatedPin = enteredPin + digit
+                    enteredPin = updatedPin
+                    errorMessage = null
+                    if (updatedPin.length == PIN_LENGTH) {
+                        submitPin(updatedPin)
+                    }
+                },
+                onDelete = {
+                    if (remainingLockOutTime == 0L && enteredPin.isNotEmpty()) {
+                        enteredPin = enteredPin.dropLast(1)
+                        errorMessage = null
+                    }
+                },
+                onReset = {
+                    if (remainingLockOutTime == 0L && enteredPin.isNotEmpty()) {
+                        enteredPin = ""
+                        errorMessage = null
+                    }
+                },
+                modifier = Modifier.fillMaxWidth(0.9f),
+                isEnabled = remainingLockOutTime == 0L,
+                isDeleteEnabled = enteredPin.isNotEmpty(),
+                isResetEnabled = enteredPin.isNotEmpty()
+            )
+
+            if (isBiometricEnabled) {
+                Spacer(modifier = Modifier.height(16.dp))
+                FilledTonalButton(
                     onClick = {
-                        if (pinCode != null && enteredPin == pinCode) {
-                            scope.launch {
-                                settingsRepo.setFailedAttempts(0)
-                                settingsRepo.setLockoutEndTime(0L)
-                            }
-                            onUnlock()
-                        } else {
-                            val newAttempts = failedAttempts + 1
-                            errorMessage = incorrectPinMsg
-                            enteredPin = ""
-                            scope.launch {
-                                settingsRepo.setFailedAttempts(newAttempts)
-                                if (newAttempts >= 5) {
-                                    val lockoutTime = System.currentTimeMillis() + 30000L // 30s lockout
-                                    settingsRepo.setLockoutEndTime(lockoutTime)
-                                }
+                        biometricAuthenticator.authenticate(
+                            mode = BiometricAuthMode.AppConfirmation,
+                            titleRes = R.string.unlock_2fair,
+                            subtitleRes = R.string.biometric_prompt_subtitle
+                        ) { result ->
+                            when (result) {
+                                BiometricAuthResult.Success -> onUnlock()
+                                BiometricAuthResult.Failed -> errorMessage = biometricFailedMsg
+                                else -> Unit
                             }
                         }
                     },
-                    enabled = remainingLockOutTime == 0L && enteredPin.isNotEmpty()
+                    enabled = remainingLockOutTime == 0L
                 ) {
-                    Text(stringResource(R.string.unlock))
+                    Icon(
+                        imageVector = Icons.Default.Fingerprint,
+                        contentDescription = stringResource(R.string.use_biometric)
+                    )
+                    Spacer(modifier = Modifier.width(8.dp))
+                    Text(stringResource(R.string.use_biometric))
                 }
             }
         }
     }
 }
-
-private fun showBiometricPrompt(
-    activity: FragmentActivity,
-    onSuccess: () -> Unit,
-    onFailed: () -> Unit
-) {
-    val biometricManager = BiometricManager.from(activity)
-    if (biometricManager.canAuthenticate(BiometricManager.Authenticators.BIOMETRIC_STRONG or BiometricManager.Authenticators.DEVICE_CREDENTIAL) != BiometricManager.BIOMETRIC_SUCCESS) {
-        return
-    }
-
-    val executor = ContextCompat.getMainExecutor(activity)
-    val biometricPrompt = BiometricPrompt(activity, executor,
-        object : BiometricPrompt.AuthenticationCallback() {
-            override fun onAuthenticationError(errorCode: Int, errString: CharSequence) {
-                super.onAuthenticationError(errorCode, errString)
-                onFailed()
-            }
-
-            override fun onAuthenticationSucceeded(result: BiometricPrompt.AuthenticationResult) {
-                super.onAuthenticationSucceeded(result)
-                onSuccess()
-            }
-
-            override fun onAuthenticationFailed() {
-                super.onAuthenticationFailed()
-                onFailed()
-            }
-        })
-
-    val promptInfo = BiometricPrompt.PromptInfo.Builder()
-        .setTitle(activity.getString(R.string.unlock_2fair))
-        .setSubtitle(activity.getString(R.string.biometric_prompt_subtitle))
-        .setAllowedAuthenticators(BiometricManager.Authenticators.BIOMETRIC_STRONG or BiometricManager.Authenticators.DEVICE_CREDENTIAL)
-        .build()
-
-    biometricPrompt.authenticate(promptInfo)
-}
diff --git a/app/src/main/java/cn/airnan/a2fair/ui/settings/security/PinInputComponents.kt b/app/src/main/java/cn/airnan/a2fair/ui/settings/security/PinInputComponents.kt
new file mode 100644
index 0000000..ee77bd8
--- /dev/null
+++ b/app/src/main/java/cn/airnan/a2fair/ui/settings/security/PinInputComponents.kt
@@ -0,0 +1,137 @@
+package cn.airnan.a2fair.ui.settings.security
+
+import androidx.compose.foundation.background
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.shape.CircleShape
+import androidx.compose.material3.FilledTonalButton
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.OutlinedButton
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.clip
+import androidx.compose.ui.semantics.contentDescription
+import androidx.compose.ui.semantics.semantics
+import androidx.compose.ui.unit.dp
+import cn.airnan.a2fair.core.security.PIN_LENGTH
+
+@Composable
+fun PinIndicatorRow(
+    filledCount: Int,
+    modifier: Modifier = Modifier,
+    isError: Boolean = false
+) {
+    val activeColor = if (isError) {
+        MaterialTheme.colorScheme.error
+    } else {
+        MaterialTheme.colorScheme.primary
+    }
+    val inactiveColor = if (isError) {
+        MaterialTheme.colorScheme.error.copy(alpha = 0.24f)
+    } else {
+        MaterialTheme.colorScheme.surfaceVariant
+    }
+
+    Row(
+        modifier = modifier,
+        horizontalArrangement = Arrangement.Center
+    ) {
+        repeat(PIN_LENGTH) { index ->
+            Box(
+                modifier = Modifier
+                    .padding(horizontal = 6.dp)
+                    .size(14.dp)
+                    .clip(CircleShape)
+                    .background(if (index < filledCount) activeColor else inactiveColor)
+            )
+        }
+    }
+}
+
+@Composable
+fun PinNumberPad(
+    resetLabel: String,
+    deleteLabel: String,
+    onDigit: (String) -> Unit,
+    onDelete: () -> Unit,
+    onReset: () -> Unit,
+    modifier: Modifier = Modifier,
+    isEnabled: Boolean = true,
+    isDeleteEnabled: Boolean = true,
+    isResetEnabled: Boolean = true
+) {
+    val rows = listOf(
+        listOf("1", "2", "3"),
+        listOf("4", "5", "6"),
+        listOf("7", "8", "9")
+    )
+
+    Column(
+        modifier = modifier,
+        verticalArrangement = Arrangement.spacedBy(12.dp)
+    ) {
+        rows.forEach { rowDigits ->
+            Row(
+                modifier = Modifier.fillMaxWidth(),
+                horizontalArrangement = Arrangement.spacedBy(12.dp)
+            ) {
+                rowDigits.forEach { digit ->
+                    FilledTonalButton(
+                        onClick = { onDigit(digit) },
+                        modifier = Modifier
+                            .weight(1f)
+                            .height(56.dp),
+                        enabled = isEnabled
+                    ) {
+                        Text(text = digit, style = MaterialTheme.typography.titleLarge)
+                    }
+                }
+            }
+        }
+
+        Row(
+            modifier = Modifier.fillMaxWidth(),
+            horizontalArrangement = Arrangement.spacedBy(12.dp),
+            verticalAlignment = Alignment.CenterVertically
+        ) {
+            OutlinedButton(
+                onClick = onReset,
+                modifier = Modifier
+                    .weight(1f)
+                    .height(56.dp),
+                enabled = isEnabled && isResetEnabled
+            ) {
+                Text(text = resetLabel)
+            }
+
+            FilledTonalButton(
+                onClick = { onDigit("0") },
+                modifier = Modifier
+                    .weight(1f)
+                    .height(56.dp),
+                enabled = isEnabled
+            ) {
+                Text(text = "0", style = MaterialTheme.typography.titleLarge)
+            }
+
+            OutlinedButton(
+                onClick = onDelete,
+                modifier = Modifier
+                    .weight(1f)
+                    .height(56.dp)
+                    .semantics { contentDescription = deleteLabel },
+                enabled = isEnabled && isDeleteEnabled
+            ) {
+                Text(text = deleteLabel)
+            }
+        }
+    }
+}
diff --git a/app/src/main/java/cn/airnan/a2fair/ui/settings/security/PinSetupScreen.kt b/app/src/main/java/cn/airnan/a2fair/ui/settings/security/PinSetupScreen.kt
index 3649d5d..e7c4db7 100644
--- a/app/src/main/java/cn/airnan/a2fair/ui/settings/security/PinSetupScreen.kt
+++ b/app/src/main/java/cn/airnan/a2fair/ui/settings/security/PinSetupScreen.kt
@@ -8,10 +8,9 @@ import androidx.compose.runtime.*
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.res.stringResource
-import androidx.compose.ui.text.input.PasswordVisualTransformation
 import androidx.compose.ui.unit.dp
-import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import cn.airnan.a2fair.R
+import cn.airnan.a2fair.core.security.PIN_LENGTH
 import cn.airnan.a2fair.data.repository.SettingsRepository
 import kotlinx.coroutines.launch
 
@@ -26,12 +25,22 @@ fun PinSetupScreen(
     var pin by remember { mutableStateOf("") }
     var confirmPin by remember { mutableStateOf("") }
     var errorMessage by remember { mutableStateOf<String?>(null) }
-    
+
     val pinTooShortMsg = stringResource(R.string.pin_too_short)
     val pinsDoNotMatchMsg = stringResource(R.string.pins_do_not_match)
-    
+    val pinRequirementMsg = stringResource(R.string.pin_requirement)
+
     val scope = rememberCoroutineScope()
-    
+    val currentPin = if (step == 1) pin else confirmPin
+    val helperMessage = errorMessage ?: when {
+        currentPin.isEmpty() -> pinRequirementMsg
+        currentPin.length < PIN_LENGTH -> stringResource(
+            R.string.pin_digits_remaining,
+            PIN_LENGTH - currentPin.length
+        )
+        else -> pinRequirementMsg
+    }
+
     Scaffold(
         topBar = {
             TopAppBar(
@@ -58,47 +67,86 @@ fun PinSetupScreen(
                 style = MaterialTheme.typography.titleLarge
             )
             Spacer(modifier = Modifier.height(16.dp))
-            
-            OutlinedTextField(
-                value = if (step == 1) pin else confirmPin,
-                onValueChange = { 
+
+            Text(
+                text = pinRequirementMsg,
+                style = MaterialTheme.typography.bodyMedium,
+                color = MaterialTheme.colorScheme.onSurfaceVariant
+            )
+            Spacer(modifier = Modifier.height(24.dp))
+
+            PinIndicatorRow(
+                filledCount = currentPin.length,
+                isError = errorMessage != null
+            )
+            Spacer(modifier = Modifier.height(12.dp))
+
+            Text(
+                text = helperMessage,
+                style = MaterialTheme.typography.bodyMedium,
+                color = if (errorMessage != null) {
+                    MaterialTheme.colorScheme.error
+                } else {
+                    MaterialTheme.colorScheme.onSurfaceVariant
+                }
+            )
+            Spacer(modifier = Modifier.height(24.dp))
+
+            PinNumberPad(
+                resetLabel = if (step == 1) {
+                    stringResource(R.string.clear_pin_input)
+                } else {
+                    stringResource(R.string.reset_pin_input)
+                },
+                deleteLabel = stringResource(R.string.delete_digit),
+                onDigit = { digit ->
+                    if (currentPin.length >= PIN_LENGTH) return@PinNumberPad
                     if (step == 1) {
-                        pin = it
+                        pin += digit
                     } else {
-                        confirmPin = it
+                        confirmPin += digit
                     }
                     errorMessage = null
                 },
-                visualTransformation = PasswordVisualTransformation(),
-                singleLine = true,
-                isError = errorMessage != null,
-                modifier = Modifier.fillMaxWidth()
+                onDelete = {
+                    if (step == 1 && pin.isNotEmpty()) {
+                        pin = pin.dropLast(1)
+                    } else if (step == 2 && confirmPin.isNotEmpty()) {
+                        confirmPin = confirmPin.dropLast(1)
+                    }
+                    errorMessage = null
+                },
+                onReset = {
+                    if (step == 1) {
+                        pin = ""
+                    } else {
+                        step = 1
+                        pin = ""
+                        confirmPin = ""
+                    }
+                    errorMessage = null
+                },
+                isDeleteEnabled = currentPin.isNotEmpty(),
+                isResetEnabled = currentPin.isNotEmpty() || step == 2
             )
-            
-            if (errorMessage != null) {
-                Text(
-                    text = errorMessage!!,
-                    color = MaterialTheme.colorScheme.error,
-                    style = MaterialTheme.typography.bodySmall,
-                    modifier = Modifier.padding(top = 4.dp)
-                )
-            }
-            
             Spacer(modifier = Modifier.height(24.dp))
-            
+
             Button(
                 onClick = {
                     if (step == 1) {
-                        if (pin.length < 4) {
+                        if (pin.length != PIN_LENGTH) {
                             errorMessage = pinTooShortMsg
                         } else {
+                            confirmPin = ""
+                            errorMessage = null
                             step = 2
                         }
                     } else {
-                        if (pin == confirmPin) {
+                        if (confirmPin.length != PIN_LENGTH) {
+                            errorMessage = pinTooShortMsg
+                        } else if (pin == confirmPin) {
                             scope.launch {
-                                settingsRepository.setPinCode(pin)
-                                settingsRepository.setPinEnabled(true)
+                                settingsRepository.enablePin(pin)
                                 onNavigateBack()
                             }
                         } else {
diff --git a/app/src/main/java/cn/airnan/a2fair/ui/settings/security/SecuritySettingsScreen.kt b/app/src/main/java/cn/airnan/a2fair/ui/settings/security/SecuritySettingsScreen.kt
index 6ab1cd3..b384ba0 100644
--- a/app/src/main/java/cn/airnan/a2fair/ui/settings/security/SecuritySettingsScreen.kt
+++ b/app/src/main/java/cn/airnan/a2fair/ui/settings/security/SecuritySettingsScreen.kt
@@ -1,8 +1,9 @@
 package cn.airnan.a2fair.ui.settings.security
 
 import androidx.compose.foundation.layout.*
+import androidx.compose.foundation.selection.selectable
 import androidx.compose.material.icons.Icons
-import androidx.compose.material.icons.filled.ArrowBack
+import androidx.compose.material.icons.automirrored.filled.ArrowBack
 import androidx.compose.material3.*
 import androidx.compose.runtime.*
 import androidx.compose.ui.Alignment
@@ -11,6 +12,7 @@ import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.unit.dp
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import cn.airnan.a2fair.R
+import cn.airnan.a2fair.data.repository.AppLockTrigger
 import cn.airnan.a2fair.data.repository.SettingsRepository
 import kotlinx.coroutines.launch
 
@@ -22,11 +24,46 @@ fun SecuritySettingsScreen(
     onNavigateToPinSetup: () -> Unit,
     modifier: Modifier = Modifier
 ) {
-    val isPinEnabled by settingsRepository.isPinEnabled.collectAsStateWithLifecycle(initialValue = false)
-    val isBiometricEnabled by settingsRepository.isBiometricEnabled.collectAsStateWithLifecycle(initialValue = false)
+    val appLockSettings by settingsRepository.appLockSettings.collectAsStateWithLifecycle(
+        initialValue = cn.airnan.a2fair.data.repository.AppLockSettings()
+    )
+    val pinCode by settingsRepository.pinCode.collectAsStateWithLifecycle(initialValue = null)
     val isFlagSecureEnabled by settingsRepository.isFlagSecureEnabled.collectAsStateWithLifecycle(initialValue = false)
-    
+
+    val isPinEnabled = appLockSettings.isPinEnabled
+    val isBiometricEnabled = appLockSettings.isBiometricEnabled
+    val lockTrigger = appLockSettings.lockTrigger
+
     val scope = rememberCoroutineScope()
+    val snackbarHostState = remember { SnackbarHostState() }
+    val biometricAuthenticator = rememberBiometricAuthenticator()
+    var showLockTriggerDialog by remember { mutableStateOf(false) }
+    var verificationAction by remember { mutableStateOf<SecurityVerificationAction?>(null) }
+
+    val enableBiometricTitle = stringResource(R.string.enable_biometric_verification_title)
+    val enableBiometricSubtitle = stringResource(R.string.enable_biometric_verification_desc)
+    val disableBiometricTitle = stringResource(R.string.disable_biometric_verification_title)
+    val disableBiometricDesc = stringResource(R.string.disable_biometric_verification_desc)
+    val disablePinTitle = stringResource(R.string.disable_pin_verification_title)
+    val disablePinDesc = stringResource(R.string.disable_pin_verification_desc)
+    val biometricFailedMessage = stringResource(R.string.biometric_failed)
+    val biometricNoHardwareMessage = stringResource(R.string.biometric_error_no_hardware)
+    val biometricHardwareUnavailableMessage = stringResource(R.string.biometric_error_hw_unavailable)
+    val biometricNotEnrolledMessage = stringResource(R.string.biometric_error_none_enrolled)
+    val biometricUnavailableMessage = stringResource(R.string.biometric_error_unavailable)
+    val biometricNotAvailableOnScreenMessage = stringResource(R.string.biometric_not_available_on_this_screen)
+    val securityVerificationUnavailableMessage = stringResource(R.string.security_verification_unavailable)
+
+    val lockTriggerOptions = remember {
+        AppLockTrigger.entries.map { trigger ->
+            trigger to when (trigger) {
+                AppLockTrigger.IMMEDIATELY -> R.string.lock_trigger_immediately
+                AppLockTrigger.AFTER_1_MINUTE -> R.string.lock_trigger_after_1_minute
+                AppLockTrigger.AFTER_3_MINUTES -> R.string.lock_trigger_after_3_minutes
+                AppLockTrigger.AFTER_5_MINUTES -> R.string.lock_trigger_after_5_minutes
+            }
+        }
+    }
 
     Scaffold(
         topBar = {
@@ -34,11 +71,12 @@ fun SecuritySettingsScreen(
                 title = { Text(stringResource(R.string.security)) },
                 navigationIcon = {
                     IconButton(onClick = onNavigateBack) {
-                        Icon(Icons.Default.ArrowBack, contentDescription = stringResource(R.string.back))
+                        Icon(Icons.AutoMirrored.Filled.ArrowBack, contentDescription = stringResource(R.string.back))
                     }
                 }
             )
         },
+        snackbarHost = { SnackbarHost(snackbarHostState) },
         modifier = modifier
     ) { padding ->
         Column(
@@ -66,11 +104,7 @@ fun SecuritySettingsScreen(
                         if (checked) {
                             onNavigateToPinSetup()
                         } else {
-                            scope.launch {
-                                settingsRepository.setPinEnabled(false)
-                                settingsRepository.setPinCode(null)
-                                settingsRepository.setBiometricEnabled(false)
-                            }
+                            verificationAction = SecurityVerificationAction.DisablePin
                         }
                     }
                 )
@@ -95,14 +129,77 @@ fun SecuritySettingsScreen(
                     Switch(
                         checked = isBiometricEnabled,
                         onCheckedChange = { checked ->
-                            scope.launch {
-                                settingsRepository.setBiometricEnabled(checked)
+                            if (checked) {
+                                biometricAuthenticator.authenticate(
+                                    mode = BiometricAuthMode.BiometricOnly,
+                                    titleRes = R.string.enable_biometric_verification_title,
+                                    subtitleRes = R.string.enable_biometric_verification_desc
+                                ) { result ->
+                                    when (result) {
+                                        BiometricAuthResult.Success -> {
+                                            scope.launch {
+                                                settingsRepository.setBiometricEnabled(true)
+                                            }
+                                        }
+                                        is BiometricAuthResult.Unavailable -> {
+                                            scope.launch {
+                                                snackbarHostState.showSnackbar(
+                                                    message = when (result.messageRes) {
+                                                        R.string.biometric_error_no_hardware -> biometricNoHardwareMessage
+                                                        R.string.biometric_error_hw_unavailable -> biometricHardwareUnavailableMessage
+                                                        R.string.biometric_error_none_enrolled -> biometricNotEnrolledMessage
+                                                        R.string.biometric_not_available_on_this_screen -> biometricNotAvailableOnScreenMessage
+                                                        R.string.security_verification_unavailable -> securityVerificationUnavailableMessage
+                                                        else -> biometricUnavailableMessage
+                                                    }
+                                                )
+                                            }
+                                        }
+                                        BiometricAuthResult.Failed -> {
+                                            scope.launch {
+                                                snackbarHostState.showSnackbar(
+                                                    message = biometricFailedMessage
+                                                )
+                                            }
+                                        }
+                                        BiometricAuthResult.Cancelled -> Unit
+                                    }
+                                }
+                            } else {
+                                verificationAction = SecurityVerificationAction.DisableBiometric
                             }
                         }
                     )
                 }
                 
                 Spacer(modifier = Modifier.height(16.dp))
+
+                Card(
+                    onClick = { showLockTriggerDialog = true },
+                    modifier = Modifier.fillMaxWidth()
+                ) {
+                    Column(
+                        modifier = Modifier.padding(16.dp)
+                    ) {
+                        Text(
+                            stringResource(R.string.lock_trigger_title),
+                            style = MaterialTheme.typography.titleMedium
+                        )
+                        Text(
+                            stringResource(R.string.lock_trigger_desc),
+                            style = MaterialTheme.typography.bodyMedium,
+                            color = MaterialTheme.colorScheme.onSurfaceVariant
+                        )
+                        Spacer(modifier = Modifier.height(8.dp))
+                        Text(
+                            text = stringResource(lockTrigger.toLabelRes()),
+                            style = MaterialTheme.typography.bodyLarge,
+                            color = MaterialTheme.colorScheme.primary
+                        )
+                    }
+                }
+
+                Spacer(modifier = Modifier.height(16.dp))
             }
             
             Row(
@@ -129,4 +226,84 @@ fun SecuritySettingsScreen(
             }
         }
     }
+
+    verificationAction?.let { action ->
+        SecurityVerificationDialog(
+            title = when (action) {
+                SecurityVerificationAction.DisableBiometric -> disableBiometricTitle
+                SecurityVerificationAction.DisablePin -> disablePinTitle
+            },
+            description = when (action) {
+                SecurityVerificationAction.DisableBiometric -> disableBiometricDesc
+                SecurityVerificationAction.DisablePin -> disablePinDesc
+            },
+            expectedPin = pinCode,
+            onDismissRequest = { verificationAction = null },
+            onVerified = {
+                scope.launch {
+                    when (action) {
+                        SecurityVerificationAction.DisableBiometric -> {
+                            settingsRepository.setBiometricEnabled(false)
+                        }
+                        SecurityVerificationAction.DisablePin -> {
+                            settingsRepository.disablePin()
+                        }
+                    }
+                    verificationAction = null
+                }
+            }
+        )
+    }
+
+    if (showLockTriggerDialog) {
+        AlertDialog(
+            onDismissRequest = { showLockTriggerDialog = false },
+            title = { Text(stringResource(R.string.lock_trigger_title)) },
+            text = {
+                Column {
+                    lockTriggerOptions.forEach { (trigger, labelRes) ->
+                        Row(
+                            modifier = Modifier
+                                .fillMaxWidth()
+                                .selectable(
+                                    selected = lockTrigger == trigger,
+                                    onClick = {
+                                        scope.launch {
+                                            settingsRepository.setAppLockTrigger(trigger)
+                                        }
+                                        showLockTriggerDialog = false
+                                    }
+                                )
+                                .padding(vertical = 8.dp),
+                            verticalAlignment = Alignment.CenterVertically
+                        ) {
+                            RadioButton(
+                                selected = lockTrigger == trigger,
+                                onClick = null
+                            )
+                            Spacer(modifier = Modifier.width(12.dp))
+                            Text(text = stringResource(labelRes))
+                        }
+                    }
+                }
+            },
+            confirmButton = {
+                TextButton(onClick = { showLockTriggerDialog = false }) {
+                    Text(stringResource(R.string.close))
+                }
+            }
+        )
+    }
+}
+
+private enum class SecurityVerificationAction {
+    DisableBiometric,
+    DisablePin
+}
+
+private fun AppLockTrigger.toLabelRes(): Int = when (this) {
+    AppLockTrigger.IMMEDIATELY -> R.string.lock_trigger_immediately
+    AppLockTrigger.AFTER_1_MINUTE -> R.string.lock_trigger_after_1_minute
+    AppLockTrigger.AFTER_3_MINUTES -> R.string.lock_trigger_after_3_minutes
+    AppLockTrigger.AFTER_5_MINUTES -> R.string.lock_trigger_after_5_minutes
 }
diff --git a/app/src/main/java/cn/airnan/a2fair/ui/settings/security/SecurityVerificationDialog.kt b/app/src/main/java/cn/airnan/a2fair/ui/settings/security/SecurityVerificationDialog.kt
new file mode 100644
index 0000000..96fe5da
--- /dev/null
+++ b/app/src/main/java/cn/airnan/a2fair/ui/settings/security/SecurityVerificationDialog.kt
@@ -0,0 +1,116 @@
+package cn.airnan.a2fair.ui.settings.security
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.material3.AlertDialog
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.unit.dp
+import cn.airnan.a2fair.R
+import cn.airnan.a2fair.core.security.PIN_LENGTH
+
+@Composable
+fun SecurityVerificationDialog(
+    title: String,
+    description: String,
+    expectedPin: String?,
+    onDismissRequest: () -> Unit,
+    onVerified: () -> Unit
+) {
+    var enteredPin by remember { mutableStateOf("") }
+    var errorMessage by remember { mutableStateOf<String?>(null) }
+    val incorrectPinMessage = stringResource(R.string.incorrect_pin)
+    val pinHintMessage = stringResource(R.string.confirm_current_pin)
+
+    fun submitPin(candidate: String) {
+        if (!expectedPin.isNullOrEmpty() && candidate == expectedPin) {
+            onVerified()
+        } else {
+            enteredPin = ""
+            errorMessage = incorrectPinMessage
+        }
+    }
+
+    AlertDialog(
+        onDismissRequest = onDismissRequest,
+        title = { Text(text = title) },
+        text = {
+            Column(
+                modifier = Modifier.fillMaxWidth(),
+                verticalArrangement = Arrangement.spacedBy(12.dp)
+            ) {
+                Text(
+                    text = description,
+                    style = MaterialTheme.typography.bodyMedium,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant
+                )
+
+                PinIndicatorRow(
+                    filledCount = enteredPin.length,
+                    isError = errorMessage != null,
+                    modifier = Modifier.fillMaxWidth()
+                )
+
+                Text(
+                    text = errorMessage ?: pinHintMessage,
+                    style = MaterialTheme.typography.bodyMedium,
+                    color = if (errorMessage != null) {
+                        MaterialTheme.colorScheme.error
+                    } else {
+                        MaterialTheme.colorScheme.onSurfaceVariant
+                    }
+                )
+
+                Spacer(modifier = Modifier.height(4.dp))
+
+                PinNumberPad(
+                    resetLabel = stringResource(R.string.clear_pin_input),
+                    deleteLabel = stringResource(R.string.delete_digit),
+                    onDigit = { digit ->
+                        if (enteredPin.length >= PIN_LENGTH) return@PinNumberPad
+                        val updatedPin = enteredPin + digit
+                        enteredPin = updatedPin
+                        errorMessage = null
+                        if (updatedPin.length == PIN_LENGTH) {
+                            submitPin(updatedPin)
+                        }
+                    },
+                    onDelete = {
+                        if (enteredPin.isNotEmpty()) {
+                            enteredPin = enteredPin.dropLast(1)
+                            errorMessage = null
+                        }
+                    },
+                    onReset = {
+                        if (enteredPin.isNotEmpty()) {
+                            enteredPin = ""
+                            errorMessage = null
+                        }
+                    },
+                    modifier = Modifier
+                        .fillMaxWidth()
+                        .padding(top = 4.dp),
+                    isDeleteEnabled = enteredPin.isNotEmpty(),
+                    isResetEnabled = enteredPin.isNotEmpty()
+                )
+            }
+        },
+        confirmButton = {
+            TextButton(onClick = onDismissRequest) {
+                Text(text = stringResource(R.string.cancel))
+            }
+        }
+    )
+}
diff --git a/app/src/main/res/values-zh-rCN/strings.xml b/app/src/main/res/values-zh-rCN/strings.xml
index 00d6396..4467b16 100644
--- a/app/src/main/res/values-zh-rCN/strings.xml
+++ b/app/src/main/res/values-zh-rCN/strings.xml
@@ -69,6 +69,12 @@
     <string name="app_lock_pin_desc">打开应用时需要输入 PIN 码</string>
     <string name="biometric_unlock">生物识别解锁</string>
     <string name="biometric_unlock_desc">使用指纹/面部解锁应用</string>
+    <string name="lock_trigger_title">锁定时机</string>
+    <string name="lock_trigger_desc">选择离开应用后何时自动锁定</string>
+    <string name="lock_trigger_immediately">立即</string>
+    <string name="lock_trigger_after_1_minute">1 分钟</string>
+    <string name="lock_trigger_after_3_minutes">3 分钟</string>
+    <string name="lock_trigger_after_5_minutes">5 分钟</string>
     <string name="block_screenshots">禁止截屏</string>
     <string name="block_screenshots_desc">防止对应用内容进行截屏或录屏</string>
 
@@ -76,8 +82,14 @@
     <string name="set_pin">设置 PIN 码</string>
     <string name="enter_new_pin">输入新 PIN 码</string>
     <string name="confirm_pin">确认 PIN 码</string>
-    <string name="pin_too_short">PIN 码至少需要 4 位</string>
+    <string name="pin_requirement">PIN 码固定为 6 位数字</string>
+    <string name="pin_digits_hint">请输入 6 位数字 PIN 码</string>
+    <string name="pin_digits_remaining">还需输入 %d 位</string>
+    <string name="pin_too_short">PIN 码必须为 6 位数字</string>
     <string name="pins_do_not_match">两次输入的 PIN 码不一致</string>
+    <string name="delete_digit">删除</string>
+    <string name="reset_pin_input">重输</string>
+    <string name="clear_pin_input">清空</string>
     <string name="next">下一步</string>
     <string name="confirm">确认</string>
 
@@ -91,6 +103,19 @@
     <string name="try_again_in">请等待 %d 秒后重试</string>
     <string name="unlock_2fair">解锁 2FAir</string>
     <string name="biometric_prompt_subtitle">使用您的生物识别凭证登录</string>
+    <string name="confirm_current_pin">请输入当前 PIN 码以继续</string>
+    <string name="enable_biometric_verification_title">验证生物识别</string>
+    <string name="enable_biometric_verification_desc">启用生物识别解锁前，请先完成一次生物识别验证</string>
+    <string name="disable_biometric_verification_title">确认关闭生物识别</string>
+    <string name="disable_biometric_verification_desc">关闭生物识别解锁前，请先输入当前 PIN 码。关闭后会保留 PIN 码。</string>
+    <string name="disable_pin_verification_title">确认关闭应用锁 PIN 码</string>
+    <string name="disable_pin_verification_desc">关闭应用锁前，请先输入当前 PIN 码。关闭后会同时关闭生物识别并清除已保存的 PIN 码。</string>
+    <string name="biometric_error_no_hardware">此设备不支持生物识别</string>
+    <string name="biometric_error_hw_unavailable">生物识别当前暂时不可用</string>
+    <string name="biometric_error_none_enrolled">请先在系统设置中录入生物识别信息</string>
+    <string name="biometric_error_unavailable">当前无法使用生物识别</string>
+    <string name="biometric_not_available_on_this_screen">当前页面无法发起生物识别</string>
+    <string name="security_verification_unavailable">当前没有可用的系统认证方式</string>
 
     <!-- Backup & Restore -->
     <string name="export_successful">导出成功</string>
diff --git a/app/src/main/res/values-zh-rTW/strings.xml b/app/src/main/res/values-zh-rTW/strings.xml
index bf9cecb..d9b5fe1 100644
--- a/app/src/main/res/values-zh-rTW/strings.xml
+++ b/app/src/main/res/values-zh-rTW/strings.xml
@@ -69,6 +69,12 @@
     <string name="app_lock_pin_desc">開啟應用程式時需要輸入 PIN 碼</string>
     <string name="biometric_unlock">生物辨識解鎖</string>
     <string name="biometric_unlock_desc">使用指紋/臉部解鎖應用程式</string>
+    <string name="lock_trigger_title">鎖定時機</string>
+    <string name="lock_trigger_desc">選擇離開應用程式後何時自動鎖定</string>
+    <string name="lock_trigger_immediately">立即</string>
+    <string name="lock_trigger_after_1_minute">1 分鐘</string>
+    <string name="lock_trigger_after_3_minutes">3 分鐘</string>
+    <string name="lock_trigger_after_5_minutes">5 分鐘</string>
     <string name="block_screenshots">禁止截圖</string>
     <string name="block_screenshots_desc">防止對應用程式內容進行截圖或錄影</string>
 
@@ -76,8 +82,14 @@
     <string name="set_pin">設定 PIN 碼</string>
     <string name="enter_new_pin">輸入新 PIN 碼</string>
     <string name="confirm_pin">確認 PIN 碼</string>
-    <string name="pin_too_short">PIN 碼至少需要 4 位</string>
+    <string name="pin_requirement">PIN 碼固定為 6 位數字</string>
+    <string name="pin_digits_hint">請輸入 6 位數字 PIN 碼</string>
+    <string name="pin_digits_remaining">還需輸入 %d 位</string>
+    <string name="pin_too_short">PIN 碼必須為 6 位數字</string>
     <string name="pins_do_not_match">兩次輸入的 PIN 碼不一致</string>
+    <string name="delete_digit">刪除</string>
+    <string name="reset_pin_input">重輸</string>
+    <string name="clear_pin_input">清空</string>
     <string name="next">下一步</string>
     <string name="confirm">確認</string>
 
@@ -91,6 +103,19 @@
     <string name="try_again_in">請等待 %d 秒後重試</string>
     <string name="unlock_2fair">解鎖 2FAir</string>
     <string name="biometric_prompt_subtitle">使用您的生物辨識憑證登入</string>
+    <string name="confirm_current_pin">請輸入目前的 PIN 碼以繼續</string>
+    <string name="enable_biometric_verification_title">驗證生物辨識</string>
+    <string name="enable_biometric_verification_desc">啟用生物辨識解鎖前，請先完成一次生物辨識驗證</string>
+    <string name="disable_biometric_verification_title">確認關閉生物辨識</string>
+    <string name="disable_biometric_verification_desc">關閉生物辨識解鎖前，請先輸入目前的 PIN 碼。關閉後會保留 PIN 碼。</string>
+    <string name="disable_pin_verification_title">確認關閉應用程式 PIN 碼鎖定</string>
+    <string name="disable_pin_verification_desc">關閉應用程式鎖定前，請先輸入目前的 PIN 碼。關閉後會同時關閉生物辨識並清除已儲存的 PIN 碼。</string>
+    <string name="biometric_error_no_hardware">此裝置不支援生物辨識</string>
+    <string name="biometric_error_hw_unavailable">生物辨識目前暫時無法使用</string>
+    <string name="biometric_error_none_enrolled">請先在系統設定中錄入生物辨識資訊</string>
+    <string name="biometric_error_unavailable">目前無法使用生物辨識</string>
+    <string name="biometric_not_available_on_this_screen">目前頁面無法啟動生物辨識</string>
+    <string name="security_verification_unavailable">目前沒有可用的系統驗證方式</string>
 
     <!-- Backup & Restore -->
     <string name="export_successful">匯出成功</string>
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index 2a65b31..c4946bb 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -69,6 +69,12 @@
     <string name="app_lock_pin_desc">Require PIN to open the app</string>
     <string name="biometric_unlock">Biometric Unlock</string>
     <string name="biometric_unlock_desc">Use fingerprint/face to unlock</string>
+    <string name="lock_trigger_title">Lock Timing</string>
+    <string name="lock_trigger_desc">Choose when the app should lock after leaving it</string>
+    <string name="lock_trigger_immediately">Immediately</string>
+    <string name="lock_trigger_after_1_minute">After 1 minute</string>
+    <string name="lock_trigger_after_3_minutes">After 3 minutes</string>
+    <string name="lock_trigger_after_5_minutes">After 5 minutes</string>
     <string name="block_screenshots">Block Screenshots</string>
     <string name="block_screenshots_desc">Prevent taking screenshots of the app</string>
 
@@ -76,8 +82,14 @@
     <string name="set_pin">Set PIN</string>
     <string name="enter_new_pin">Enter a new PIN</string>
     <string name="confirm_pin">Confirm your PIN</string>
-    <string name="pin_too_short">PIN must be at least 4 characters</string>
+    <string name="pin_requirement">PIN must be exactly 6 digits</string>
+    <string name="pin_digits_hint">Enter your 6-digit PIN</string>
+    <string name="pin_digits_remaining">%d digits remaining</string>
+    <string name="pin_too_short">PIN must be exactly 6 digits</string>
     <string name="pins_do_not_match">PINs do not match</string>
+    <string name="delete_digit">Delete</string>
+    <string name="reset_pin_input">Start over</string>
+    <string name="clear_pin_input">Clear</string>
     <string name="next">Next</string>
     <string name="confirm">Confirm</string>
 
@@ -91,6 +103,19 @@
     <string name="try_again_in">Try again in %ds</string>
     <string name="unlock_2fair">Unlock 2FAir</string>
     <string name="biometric_prompt_subtitle">Log in using your biometric credential</string>
+    <string name="confirm_current_pin">Enter your current PIN to continue</string>
+    <string name="enable_biometric_verification_title">Verify biometric unlock</string>
+    <string name="enable_biometric_verification_desc">Authenticate once with biometrics before enabling biometric unlock</string>
+    <string name="disable_biometric_verification_title">Confirm to turn off biometric unlock</string>
+    <string name="disable_biometric_verification_desc">Enter your current PIN before turning off biometric unlock. Your PIN will remain enabled.</string>
+    <string name="disable_pin_verification_title">Confirm to turn off app lock PIN</string>
+    <string name="disable_pin_verification_desc">Enter your current PIN before turning off app lock. This will also turn off biometric unlock and clear the saved PIN.</string>
+    <string name="biometric_error_no_hardware">This device does not support biometric authentication</string>
+    <string name="biometric_error_hw_unavailable">Biometric authentication is temporarily unavailable</string>
+    <string name="biometric_error_none_enrolled">Set up biometrics in system settings before enabling biometric unlock</string>
+    <string name="biometric_error_unavailable">Biometric authentication is currently unavailable</string>
+    <string name="biometric_not_available_on_this_screen">Biometric authentication is not available on this screen</string>
+    <string name="security_verification_unavailable">No system verification method is available right now</string>
 
     <!-- Backup & Restore -->
     <string name="export_successful">Export successful</string>