Build: sign the release APK with a permanent key

.github/workflows/ci.yml

@@ -65,12 +65,24 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - name: Assemble + unit tests
+        if: github.event_name == 'pull_request'
         run: cd android && bash ./gradlew :app:assembleDebug :app:testDebugUnitTest
       - uses: actions/upload-artifact@v4
+        if: github.event_name == 'pull_request'
         with:
           name: app-debug.apk
           path: android/app/build/outputs/apk/debug/app-debug.apk
           if-no-files-found: error
+      - name: Assemble signed release + unit tests
+        # the release key lives on the runner host (AUDIOBRIDGE_KEYSTORE_PROPS in the runner's .env)
+        if: github.event_name != 'pull_request'
+        run: cd android && bash ./gradlew :app:assembleRelease :app:testDebugUnitTest && cp app/build/outputs/apk/release/app-release.apk app/build/outputs/apk/release/AudioBridge.apk
+      - uses: actions/upload-artifact@v4
+        if: github.event_name != 'pull_request'
+        with:
+          name: AudioBridge.apk
+          path: android/app/build/outputs/apk/release/AudioBridge.apk
+          if-no-files-found: error
 
   desktop-tests:
     # the desktop crate's tests need a real Windows host, so this one stays GitHub-hosted

AGENTS.md

@@ -98,7 +98,7 @@ cargo ndk -t arm64-v8a --platform 26 clippy -p audiobridge-android --all-targets
   - Phone: `<filesDir>/audiobridge/client.key`, plus SharedPreferences `audiobridge` (`paired_pcs` JSON list of `{id, name, uri, muted}`, `mic_enabled` (also flipped remotely by a PC), `autostart_done`, `service_enabled` (the global switch, missing = on), headphone buttons: `headset_enabled`, `headset_single_earbud`, `headset_double_tap`, `headset_triple_tap`, `headset_target`).
 - **Global switch (phone):** `Prefs.serviceEnabled` (written with `commit`). Off stops `BridgeService` (native `setPeers("[]")` → hub stopped, no notification, no media session); every start path (`MainActivity.startBridge`, `BootReceiver`, a sticky restart in `onStartCommand`) checks `Prefs.shouldRun()`. Pairings and settings stay. It never tells PCs to switch off: they just see the phone offline.
 - **Default UDP port:** 47130, falling back to a random port.
-- **Screenshots and releases:** the pairing QR contains the PC's secret. Never publish it; promo shots replace it with a QR of the repo URL. GitHub Releases ship `AudioBridge.exe` (the release build) and `AudioBridge.apk` (the debug-signed APK from this machine's `~/.android/debug.keystore`; a different key can't update an installed app).
+- **Screenshots and releases:** the pairing QR contains the PC's secret. Never publish it; promo shots replace it with a QR of the repo URL. GitHub Releases ship `AudioBridge.exe` (the release build) and `AudioBridge.apk` (`:app:assembleRelease`, the `AudioBridge.apk` artifact of a push run on `main`). The APK is signed with the permanent release key on the netcup server: `~/.config/audiobridge/release.jks` with its passwords in `~/.config/audiobridge/keystore.properties` (both `chmod 600`, never commit them), passed to Gradle through `AUDIOBRIDGE_KEYSTORE_PROPS` (set in `~/.config/audiobridge-env.sh` and the runner's `~/runners/audiobridge/.env`); without it the release APK comes out unsigned. A different key can't update an installed app: moving from the old debug-signed APK (≤ 0.4.0) needs one uninstall + reinstall (re-pair the PCs), after that releases update in place. Losing the key means the same again for every user.
 
 ## Important Files
 - `Cargo.toml`: workspace deps, and profiles you must keep:

android/app/build.gradle.kts

@@ -1,3 +1,4 @@
+import java.util.Properties
 import org.jetbrains.kotlin.gradle.dsl.JvmTarget
 
 plugins {
@@ -6,6 +7,12 @@ plugins {
     id("org.jetbrains.kotlin.plugin.compose")
 }
 
+// Release signing key: AUDIOBRIDGE_KEYSTORE_PROPS names a properties file with storeFile, storePassword,
+// keyAlias and keyPassword. Without it the release APK is built unsigned; debug builds are unaffected.
+val releaseKeystoreProps: Properties? = providers.environmentVariable("AUDIOBRIDGE_KEYSTORE_PROPS").orNull
+    ?.takeIf { it.isNotBlank() }
+    ?.let { path -> Properties().apply { file(path).inputStream().use { load(it) } } }
+
 android {
     namespace = "app.audiobridge"
     compileSdk = 35
@@ -21,11 +28,23 @@ android {
         }
     }
 
+    signingConfigs {
+        releaseKeystoreProps?.let { props ->
+            create("release") {
+                storeFile = file(props.getProperty("storeFile"))
+                storePassword = props.getProperty("storePassword")
+                keyAlias = props.getProperty("keyAlias")
+                keyPassword = props.getProperty("keyPassword")
+            }
+        }
+    }
+
     buildTypes {
         release {
             isMinifyEnabled = true
             isShrinkResources = true
             proguardFiles(getDefaultProguardFile("proguard-android-optimize.txt"), "proguard-rules.pro")
+            signingConfig = signingConfigs.findByName("release")
         }
     }