diff --git a/app/build.gradle.kts b/app/build.gradle.kts
index a7394e5..49ec10c 100644
--- a/app/build.gradle.kts
+++ b/app/build.gradle.kts
@@ -161,6 +161,10 @@ android {
         }
     }
 
+    lint {
+        fatal += "NewApi"
+    }
+
     applicationVariants.configureEach {
         outputs.configureEach {
             val output = this as com.android.build.gradle.internal.api.BaseVariantOutputImpl
@@ -314,6 +318,9 @@ dependencies {
     // Debug/Test dependencies
     debugImplementation("androidx.compose.ui:ui-tooling")
     debugImplementation("androidx.compose.ui:ui-test-manifest")
+    "androidTestPlayImplementation"(composeBom23)
+    "androidTestOtherImplementation"(composeBom23)
+    "androidTestOtherLegacyImplementation"(composeBom21)
     androidTestImplementation("androidx.compose.ui:ui-test-junit4")
 
     // Common Compose-related libraries
diff --git a/app/lint.xml b/app/lint.xml
new file mode 100644
index 0000000..d4af354
--- /dev/null
+++ b/app/lint.xml
@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<lint>
+    <!--
+      Xposed/LSPosed code runs inside processes injected by the Xposed framework
+      (LSPosed requires Android 8.1+), not in the sfa app main process. Lint's
+      NewApi check based on the app's minSdk does not apply here.
+    -->
+    <issue id="NewApi">
+        <ignore path="src/main/java/io/nekohasekai/sfa/xposed" />
+        <ignore path="src/main/java/io/github/libxposed/service" />
+    </issue>
+</lint>
diff --git a/app/src/main/java/io/nekohasekai/sfa/bg/RootClient.kt b/app/src/main/java/io/nekohasekai/sfa/bg/RootClient.kt
index a7b24b9..bd372ad 100644
--- a/app/src/main/java/io/nekohasekai/sfa/bg/RootClient.kt
+++ b/app/src/main/java/io/nekohasekai/sfa/bg/RootClient.kt
@@ -4,6 +4,7 @@ import android.content.ComponentName
 import android.content.Intent
 import android.content.ServiceConnection
 import android.content.pm.PackageInfo
+import android.os.Build
 import android.os.IBinder
 import android.os.RemoteException
 import androidx.core.content.ContextCompat
@@ -130,7 +131,13 @@ object RootClient {
             val list = slice.list as List<PackageInfo>
             list
         } catch (e: RemoteException) {
-            throw e.rethrowFromSystemServer()
+            throw e.rethrowAsRuntime()
         }
     }
+
+    private fun RemoteException.rethrowAsRuntime(): RuntimeException = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
+        rethrowFromSystemServer()
+    } else {
+        RuntimeException(this)
+    }
 }
diff --git a/app/src/main/java/io/nekohasekai/sfa/compose/screen/settings/AppSettingsScreen.kt b/app/src/main/java/io/nekohasekai/sfa/compose/screen/settings/AppSettingsScreen.kt
index 9c94f63..352efdd 100644
--- a/app/src/main/java/io/nekohasekai/sfa/compose/screen/settings/AppSettingsScreen.kt
+++ b/app/src/main/java/io/nekohasekai/sfa/compose/screen/settings/AppSettingsScreen.kt
@@ -79,6 +79,7 @@ import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.unit.dp
+import androidx.core.app.NotificationManagerCompat
 import androidx.core.os.LocaleListCompat
 import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.compose.LifecycleEventEffect
@@ -195,7 +196,7 @@ fun AppSettingsScreen(navController: NavController) {
             val channel = Application.notification.getNotificationChannel("service")
             notificationEnabled = channel?.importance != NotificationManager.IMPORTANCE_NONE
         } else {
-            notificationEnabled = Application.notification.areNotificationsEnabled()
+            notificationEnabled = NotificationManagerCompat.from(context).areNotificationsEnabled()
         }
         if (silentInstallEnabled) {
             scope.launch {
diff --git a/app/src/main/java/io/nekohasekai/sfa/qrs/QRSDecoder.kt b/app/src/main/java/io/nekohasekai/sfa/qrs/QRSDecoder.kt
index c33c8bb..29008b5 100644
--- a/app/src/main/java/io/nekohasekai/sfa/qrs/QRSDecoder.kt
+++ b/app/src/main/java/io/nekohasekai/sfa/qrs/QRSDecoder.kt
@@ -1,7 +1,7 @@
 package io.nekohasekai.sfa.qrs
 
+import android.util.Base64
 import java.io.ByteArrayOutputStream
-import java.util.Base64
 import java.util.zip.Inflater
 
 class QRSDecoder {
@@ -44,7 +44,7 @@ class QRSDecoder {
     @Synchronized
     fun processFrame(base64Content: String): DecodeProgress? {
         val payload = try {
-            Base64.getDecoder().decode(base64Content)
+            Base64.decode(base64Content, Base64.NO_WRAP)
         } catch (e: Exception) {
             return null
         }
diff --git a/app/src/main/java/io/nekohasekai/sfa/qrs/QRSEncoder.kt b/app/src/main/java/io/nekohasekai/sfa/qrs/QRSEncoder.kt
index bd19bca..f15edf7 100644
--- a/app/src/main/java/io/nekohasekai/sfa/qrs/QRSEncoder.kt
+++ b/app/src/main/java/io/nekohasekai/sfa/qrs/QRSEncoder.kt
@@ -1,7 +1,7 @@
 package io.nekohasekai.sfa.qrs
 
+import android.util.Base64
 import java.io.ByteArrayOutputStream
-import java.util.Base64
 import java.util.zip.Deflater
 
 class QRSEncoder(private val sliceSize: Int = QRSConstants.DEFAULT_SLICE_SIZE) {
@@ -57,7 +57,7 @@ class QRSEncoder(private val sliceSize: Int = QRSConstants.DEFAULT_SLICE_SIZE) {
 
         return codec.encode(data, compressed, compressed.size).mapIndexed { index, block ->
             val payload = buildPayload(block)
-            val base64 = Base64.getEncoder().encodeToString(payload)
+            val base64 = Base64.encodeToString(payload, Base64.NO_WRAP)
             QRSFrame("$urlPrefix$base64", index, block.totalBlocks)
         }
     }
diff --git a/app/src/main/java/io/nekohasekai/sfa/utils/VpnDetectionTest.kt b/app/src/main/java/io/nekohasekai/sfa/utils/VpnDetectionTest.kt
index f210ed1..bb974ac 100644
--- a/app/src/main/java/io/nekohasekai/sfa/utils/VpnDetectionTest.kt
+++ b/app/src/main/java/io/nekohasekai/sfa/utils/VpnDetectionTest.kt
@@ -2,8 +2,10 @@ package io.nekohasekai.sfa.utils
 
 import android.content.Context
 import android.net.ConnectivityManager
+import android.net.LinkProperties
 import android.net.Network
 import android.net.NetworkCapabilities
+import android.os.Build
 import java.net.NetworkInterface
 import java.util.Collections
 
@@ -67,7 +69,7 @@ object VpnDetectionTest {
         }
 
         // Check activeLinkProperties interface
-        val activeLinkProperties = runCatching { cm.getLinkProperties(cm.activeNetwork) }.getOrNull()
+        val activeLinkProperties = readActiveLinkProperties(cm)
         if (isVpnInterface(activeLinkProperties?.interfaceName)) {
             activeLinkProperties?.interfaceName?.let(frameworkInterfaces::add)
             frameworkDetected += "LinkProperties"
@@ -117,7 +119,7 @@ object VpnDetectionTest {
         } catch (_: Throwable) {
             null
         }
-        val activeLinkProperties = runCatching { cm.getLinkProperties(cm.activeNetwork) }.getOrNull()
+        val activeLinkProperties = readActiveLinkProperties(cm)
         val networks = cm.allNetworks ?: emptyArray()
         val proxies = buildList {
             add(formatProxyInfo(defaultProxy))
@@ -129,7 +131,12 @@ object VpnDetectionTest {
         return proxies.firstOrNull { !it.isNullOrEmpty() }
     }
 
-    private fun readProxyFromLinkProperties(lp: android.net.LinkProperties?): android.net.ProxyInfo? {
+    private fun readActiveLinkProperties(cm: ConnectivityManager): LinkProperties? {
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) return null
+        return runCatching { cm.getLinkProperties(cm.activeNetwork) }.getOrNull()
+    }
+
+    private fun readProxyFromLinkProperties(lp: LinkProperties?): android.net.ProxyInfo? {
         if (lp == null) return null
         return try {
             val method = lp.javaClass.getMethod("getHttpProxy")