feat(update): silent self-update via PackageInstaller session — #2438

Replaces the ACTION_VIEW + application/vnd.android.package-archive handoff
with a PackageInstaller session, and declares
UPDATE_PACKAGES_WITHOUT_USER_ACTION so the update can land with no confirm
dialog at all.

The platform grants the silent path when the installer opts in via
setRequireUserAction(USER_ACTION_NOT_REQUIRED), the installed app targets
API 29+, the installer holds that permission, and the target is the
installer itself. Minstrel updating Minstrel satisfies all four. Where it
can't be granted — anything pre-S — the platform returns
STATUS_PENDING_USER_ACTION and we show its dialog instead, so this degrades
rather than failing.

Prior art: Mihon, which is out-of-store and self-updating and whose updates
are quiet for exactly this reason. It also confirmed REQUEST_INSTALL_PACKAGES
is not what draws install warnings — Mihon declares it too.

No setRequestUpdateOwnership(true), despite it reading like the obvious
declaration for a self-updater. Ownership can only be claimed on initial
installation (a no-op on update) and additionally wants the privileged
ENFORCE_UPDATE_OWNERSHIP permission. It's an API for app stores claiming the
apps they install.

Also: the install now has an outcome. The old path fired an intent and
assumed, so a failure and a user declining were indistinguishable. Sessions
report back, so InstallOutcome distinguishes Installed / Cancelled / Failed,
and cancelling returns to IDLE rather than showing an error — the user chose
it. DOWNLOADING and INSTALLING became separate stages because the install
half now genuinely waits, and "Downloading…" through a confirm dialog is a
lie.

The FileProvider and res/xml/file_paths.xml are gone. They existed only to
expose the cached APK as a content:// URI for the old intent; a session
takes a stream. Nothing else used that authority.

Two judgement calls worth naming:

- The pending-user-action intent is only launched if it resolves to a system
  component. Below API 34 a dynamically registered receiver can't declare
  itself unexported, so another app can broadcast at us, and an unchecked
  startActivity on an attacker-supplied extra would be an escalation
  primitive. The real confirm activity is a system app, so the check costs
  the legitimate path nothing.
- Cancellation unregisters the receiver but deliberately does NOT abandon the
  session. By then it's committed, and killing an install because the user
  navigated away from the banner misreads their intent.

Untestable here: no androidTest source set and no Robolectric, so the
gesture-level behaviour is operator on-device verification.

android/app/src/main/AndroidManifest.xml

@@ -8,7 +8,16 @@
     <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
     <uses-permission android:name="android.permission.FOREGROUND_SERVICE_MEDIA_PLAYBACK" />
     <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
+    <!-- In-app self-update. REQUEST_INSTALL_PACKAGES lets us hand an APK to the
+         platform installer at all; UPDATE_PACKAGES_WITHOUT_USER_ACTION (API 31+)
+         is what lets that install happen with NO confirm dialog. The platform
+         grants the silent path only when the installer opts in via
+         SessionParams.setRequireUserAction(USER_ACTION_NOT_REQUIRED), the
+         installed app targets API 29+, the installer holds this permission, and
+         the target is the installer itself — all true here, since Minstrel is
+         updating Minstrel. See update/data/SelfUpdateSession.kt. -->
     <uses-permission android:name="android.permission.REQUEST_INSTALL_PACKAGES" />
+    <uses-permission android:name="android.permission.UPDATE_PACKAGES_WITHOUT_USER_ACTION" />
     <uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />
     <uses-permission android:name="android.permission.CHANGE_WIFI_MULTICAST_STATE" />
 
@@ -48,15 +57,11 @@
             </intent-filter>
         </service>
 
-        <provider
-            android:name="androidx.core.content.FileProvider"
-            android:authorities="${applicationId}.fileprovider"
-            android:exported="false"
-            android:grantUriPermissions="true">
-            <meta-data
-                android:name="android.support.FILE_PROVIDER_PATHS"
-                android:resource="@xml/file_paths" />
-        </provider>
+        <!-- The FileProvider that used to live here existed solely to expose the
+             downloaded update APK as a content:// URI for the old ACTION_VIEW
+             install intent. A PackageInstaller session takes a stream instead,
+             so both the provider and res/xml/file_paths.xml are gone — nothing
+             else in the app ever used that authority. -->
 
         <!-- On-demand WorkManager initialization: MinstrelApplication
              implements Configuration.Provider and supplies the

android/app/src/main/java/com/fabledsword/minstrel/settings/ui/AboutCardViewModel.kt

@@ -6,22 +6,27 @@ import com.fabledsword.minstrel.BuildConfig
 import com.fabledsword.minstrel.api.ErrorCopy
 import com.fabledsword.minstrel.models.UpdateInfo
 import com.fabledsword.minstrel.update.data.ApkInstaller
+import com.fabledsword.minstrel.update.data.InstallStage
 import com.fabledsword.minstrel.update.data.UpdateRepository
+import com.fabledsword.minstrel.update.data.isBusy
 import com.fabledsword.minstrel.update.data.isVersionNewer
+import com.fabledsword.minstrel.update.data.message
+import com.fabledsword.minstrel.update.data.stage
 import dagger.hilt.android.lifecycle.HiltViewModel
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.flow.update
 import kotlinx.coroutines.launch
+import java.io.File
 import javax.inject.Inject
 
 /**
  * One of three terminal states the Check-for-updates button surfaces.
  * `Idle` is the pre-check state; `Latest` means the installed build
  * matches or exceeds the server's bundled APK; `UpdateAvailable`
- * surfaces an "Install vX.Y.Z" button that downloads + launches the
- * system installer via [ApkInstaller].
+ * surfaces an "Install vX.Y.Z" button that downloads the APK and
+ * installs it via [ApkInstaller].
  */
 sealed interface UpdateCheckResult {
     data object Idle : UpdateCheckResult
@@ -33,7 +38,7 @@ sealed interface UpdateCheckResult {
 data class AboutUiState(
     val installedVersion: String = BuildConfig.VERSION_NAME,
     val isChecking: Boolean = false,
-    val isInstalling: Boolean = false,
+    val installStage: InstallStage = InstallStage.IDLE,
     val installMessage: String? = null,
     val result: UpdateCheckResult = UpdateCheckResult.Idle,
 )
@@ -43,9 +48,9 @@ data class AboutUiState(
  * [UpdateRepository.getLatest], compares versus the build's
  * VERSION_NAME via [isVersionNewer], and reports the terminal state.
  * When an update is available, [install] downloads the APK via
- * [ApkInstaller] and hands it to the system installer — routing the
- * user to the "install unknown apps" settings page first when that
- * permission hasn't been granted.
+ * [ApkInstaller] and installs it — routing the user to the "install
+ * unknown apps" settings page first when that permission hasn't been
+ * granted.
  */
 @HiltViewModel
 class AboutCardViewModel @Inject constructor(
@@ -75,7 +80,7 @@ class AboutCardViewModel @Inject constructor(
     }
 
     fun install(info: UpdateInfo) {
-        if (internal.value.isInstalling) return
+        if (internal.value.installStage.isBusy()) return
         if (!installer.canInstall()) {
             installer.requestInstallPermission()
             internal.update {
@@ -84,21 +89,32 @@ class AboutCardViewModel @Inject constructor(
             return
         }
         viewModelScope.launch {
-            internal.update { it.copy(isInstalling = true, installMessage = null) }
-            runCatching { installer.downloadApk(info.apkUrl) }
-                .onSuccess { apk ->
-                    installer.launchInstall(apk)
-                    internal.update { it.copy(isInstalling = false) }
-                }
-                .onFailure { e ->
-                    val why = ErrorCopy.fromThrowable(e)
-                    internal.update {
-                        it.copy(
-                            isInstalling = false,
-                            installMessage = "Couldn't download update: $why",
-                        )
-                    }
+            internal.update {
+                it.copy(installStage = InstallStage.DOWNLOADING, installMessage = null)
+            }
+            val apk = download(info.apkUrl)
+            if (apk != null) {
+                // The install half now suspends on the platform's verdict, so it
+                // gets its own stage — reporting "Downloading…" through it would
+                // be a lie once a confirm dialog is on screen.
+                internal.update { it.copy(installStage = InstallStage.INSTALLING) }
+                val outcome = installer.install(apk)
+                internal.update {
+                    it.copy(installStage = outcome.stage(), installMessage = outcome.message())
                 }
+            }
         }
     }
+
+    private suspend fun download(apkUrl: String): File? =
+        runCatching { installer.downloadApk(apkUrl) }
+            .onFailure { e ->
+                internal.update {
+                    it.copy(
+                        installStage = InstallStage.ERROR,
+                        installMessage = "Couldn't download update: ${ErrorCopy.fromThrowable(e)}",
+                    )
+                }
+            }
+            .getOrNull()
 }

android/app/src/main/java/com/fabledsword/minstrel/settings/ui/SettingsScreen.kt

@@ -58,6 +58,8 @@ import com.fabledsword.minstrel.nav.ServerUrl
 import com.fabledsword.minstrel.shared.widgets.MinstrelTopAppBar
 import com.fabledsword.minstrel.theme.ThemeMode
 import com.fabledsword.minstrel.theme.ThemePreferenceViewModel
+import com.fabledsword.minstrel.update.data.InstallStage
+import com.fabledsword.minstrel.update.data.isBusy
 
 @Composable
 fun SettingsScreen(
@@ -381,7 +383,7 @@ private fun UpdateControls(state: AboutUiState, viewModel: AboutCardViewModel) {
     UpdateCheckLine(result = state.result)
     Button(
         onClick = viewModel::checkForUpdates,
-        enabled = !state.isChecking && !state.isInstalling,
+        enabled = !state.isChecking && !state.installStage.isBusy(),
         modifier = Modifier.fillMaxWidth(),
     ) {
         if (state.isChecking) {
@@ -393,7 +395,7 @@ private fun UpdateControls(state: AboutUiState, viewModel: AboutCardViewModel) {
     if (available != null) {
         InstallButton(
             version = available.info.version,
-            isInstalling = state.isInstalling,
+            stage = state.installStage,
             onClick = { viewModel.install(available.info) },
         )
     }
@@ -407,16 +409,22 @@ private fun UpdateControls(state: AboutUiState, viewModel: AboutCardViewModel) {
 }
 
 @Composable
-private fun InstallButton(version: String, isInstalling: Boolean, onClick: () -> Unit) {
+private fun InstallButton(version: String, stage: InstallStage, onClick: () -> Unit) {
     Button(
         onClick = onClick,
-        enabled = !isInstalling,
+        enabled = !stage.isBusy(),
         modifier = Modifier.fillMaxWidth(),
     ) {
-        if (isInstalling) {
+        if (stage.isBusy()) {
             ButtonSpinner()
         }
-        Text(if (isInstalling) "Downloading…" else "Install $version")
+        Text(
+            when (stage) {
+                InstallStage.DOWNLOADING -> "Downloading…"
+                InstallStage.INSTALLING -> "Installing…"
+                else -> "Install $version"
+            },
+        )
     }
 }
 

android/app/src/main/java/com/fabledsword/minstrel/update/data/ApkInstaller.kt

@@ -5,7 +5,6 @@ import android.content.Intent
 import android.net.Uri
 import android.os.Build
 import android.provider.Settings
-import androidx.core.content.FileProvider
 import dagger.hilt.android.qualifiers.ApplicationContext
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.withContext
@@ -17,27 +16,26 @@ import javax.inject.Inject
 import javax.inject.Singleton
 
 private const val APK_FILENAME = "minstrel-update.apk"
-private const val APK_MIME = "application/vnd.android.package-archive"
 
 /**
- * Downloads the server-bundled APK and hands it to Android's package
- * installer. Mirrors Flutter's `update/installer.dart` — the native
- * side that the Flutter MethodChannel delegated to.
+ * Downloads the server-bundled APK and installs it over ourselves.
  *
  * The download goes through the shared [OkHttpClient] so it inherits
  * the auth cookie + the BaseUrlInterceptor host rewrite (apkUrl is
  * server-relative, e.g. `/api/client/apk`). The APK lands in the
- * cache dir, exposed to the system installer via the app's
- * FileProvider content:// URI.
+ * cache dir; [SelfUpdateSession] streams it from there into a
+ * [android.content.pm.PackageInstaller] session.
  *
  * On Android O+ the user must have granted "install unknown apps"
  * for Minstrel; [canInstall] reports it and [requestInstallPermission]
- * opens the relevant settings screen.
+ * opens the relevant settings screen. That grant is still required with
+ * the session API — silent *updates* don't imply silent *permission*.
  */
 @Singleton
 class ApkInstaller @Inject constructor(
     @ApplicationContext private val context: Context,
     private val okHttpClient: OkHttpClient,
+    private val session: SelfUpdateSession,
 ) {
     suspend fun downloadApk(apkUrl: String): File = withContext(Dispatchers.IO) {
         val request = Request.Builder()
@@ -61,19 +59,13 @@ class ApkInstaller @Inject constructor(
         Build.VERSION.SDK_INT < Build.VERSION_CODES.O ||
             context.packageManager.canRequestPackageInstalls()
 
-    /** Hand the downloaded APK to the system installer's confirm dialog. */
-    fun launchInstall(apk: File) {
-        val uri: Uri = FileProvider.getUriForFile(
-            context,
-            "${context.packageName}.fileprovider",
-            apk,
-        )
-        val intent = Intent(Intent.ACTION_VIEW).apply {
-            setDataAndType(uri, APK_MIME)
-            addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION or Intent.FLAG_ACTIVITY_NEW_TASK)
-        }
-        context.startActivity(intent)
-    }
+    /**
+     * Install [apk] over ourselves, suspending until the platform decides.
+     *
+     * Note for callers: on a successful silent install this never returns —
+     * the process is replaced. Don't treat the absence of a verdict as failure.
+     */
+    suspend fun install(apk: File): InstallOutcome = session.run(apk)
 
     /** Open the "install unknown apps" settings page for Minstrel. */
     fun requestInstallPermission() {

android/app/src/main/java/com/fabledsword/minstrel/update/data/InstallOutcome.kt

@@ -0,0 +1,68 @@
+package com.fabledsword.minstrel.update.data
+
+/**
+ * Terminal verdict from the platform on a self-update install (#2438).
+ *
+ * The old `ACTION_VIEW` handoff had no verdict at all — we fired an intent and
+ * assumed. A [PackageInstaller][android.content.pm.PackageInstaller] session
+ * reports back, so "declined" and "failed" stop looking identical.
+ */
+sealed interface InstallOutcome {
+    /**
+     * The platform completed the install.
+     *
+     * Rarely observed on a self-update: our process is replaced the moment the
+     * new APK lands, so the coroutine awaiting this usually dies before it
+     * resumes. Modelled anyway — silently relying on being killed would make
+     * the success path invisible to anyone reading this.
+     */
+    data object Installed : InstallOutcome
+
+    /** The user declined the platform's confirm dialog. Not an error. */
+    data object Cancelled : InstallOutcome
+
+    /** The platform refused. [reason] is its own message, where it gave one. */
+    data class Failed(val reason: String?) : InstallOutcome
+}
+
+/**
+ * Where an install has got to, for the two surfaces that show it: the shell's
+ * [UpdateBanner][com.fabledsword.minstrel.update.ui.UpdateBanner] and the
+ * Settings About card.
+ *
+ * DOWNLOADING and INSTALLING are deliberately distinct. They used to be one
+ * state because the install half was fire-and-forget and took no time from our
+ * side; now that we await the platform's verdict, collapsing them would leave
+ * the UI claiming "Downloading…" through an install that can sit on a confirm
+ * dialog indefinitely.
+ */
+enum class InstallStage { IDLE, DOWNLOADING, INSTALLING, ERROR }
+
+/** True while an install is underway and a second tap should do nothing. */
+fun InstallStage.isBusy(): Boolean =
+    this == InstallStage.DOWNLOADING || this == InstallStage.INSTALLING
+
+/**
+ * The stage an outcome lands the UI in. A cancelled install returns to IDLE
+ * rather than ERROR — the user chose it, so presenting it as a failure would
+ * be a lie with a red tint.
+ */
+fun InstallOutcome.stage(): InstallStage = when (this) {
+    InstallOutcome.Installed, InstallOutcome.Cancelled -> InstallStage.IDLE
+    is InstallOutcome.Failed -> InstallStage.ERROR
+}
+
+/**
+ * User-facing copy for an outcome; null when there is nothing worth saying.
+ *
+ * Lives beside the outcome rather than in either UI package because two
+ * separate screens surface the same verdicts and must not drift — the same
+ * reasoning that puts [ErrorCopy][com.fabledsword.minstrel.api.ErrorCopy]
+ * outside the UI layer.
+ */
+fun InstallOutcome.message(): String? = when (this) {
+    InstallOutcome.Installed -> null
+    InstallOutcome.Cancelled -> "Update cancelled."
+    is InstallOutcome.Failed -> reason?.let { "Couldn't install update: $it" }
+        ?: "Couldn't install update."
+}

android/app/src/main/java/com/fabledsword/minstrel/update/data/SelfUpdateSession.kt

@@ -0,0 +1,220 @@
+package com.fabledsword.minstrel.update.data
+
+import android.app.PendingIntent
+import android.content.BroadcastReceiver
+import android.content.Context
+import android.content.Intent
+import android.content.IntentFilter
+import android.content.IntentSender
+import android.content.pm.ApplicationInfo
+import android.content.pm.PackageInstaller
+import android.content.pm.PackageManager
+import android.os.Build
+import androidx.core.content.ContextCompat
+import androidx.core.content.IntentCompat
+import dagger.hilt.android.qualifiers.ApplicationContext
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.suspendCancellableCoroutine
+import kotlinx.coroutines.withContext
+import java.io.File
+import javax.inject.Inject
+import javax.inject.Singleton
+import kotlin.coroutines.resume
+
+private const val STAGED_APK_NAME = "minstrel-update"
+
+/** Whole-file write: openWrite takes a Long offset, and Kotlin won't widen 0. */
+private const val WRITE_FROM_START = 0L
+
+/** Our own broadcast, delivered by the platform via the session's IntentSender. */
+private const val RESULT_ACTION = "com.fabledsword.minstrel.INSTALL_RESULT"
+
+/**
+ * Installs an APK over ourselves through a [PackageInstaller] session (#2438).
+ *
+ * Split from [ApkInstaller] because the two halves are different work — one
+ * speaks HTTP, the other speaks to the package manager — and the session half
+ * carries a receiver, a PendingIntent and version-gated params that would
+ * crowd the downloader out of its own file.
+ *
+ * ## Why a session, rather than the ACTION_VIEW intent this replaced
+ *
+ * Two reasons, and the second is the one that matters to users.
+ *
+ * The old path fired `ACTION_VIEW` at an `application/vnd.android.package-archive`
+ * URI and hoped. It could not report an outcome, so a failed install and a
+ * user who declined looked identical — see [InstallOutcome].
+ *
+ * More importantly, a session is where the platform lets a self-updater say it
+ * is one. [PackageInstaller.SessionParams.setRequireUserAction] with
+ * `USER_ACTION_NOT_REQUIRED`, paired with the `UPDATE_PACKAGES_WITHOUT_USER_ACTION`
+ * manifest permission, is the sanctioned way to update with **no dialog at
+ * all**. The platform grants that when all of: the installer opts in (here),
+ * the installed app targets API 29+ (we're on 36), the installer holds the
+ * permission (we do), and the target is the installer itself or something it
+ * first installed (we are updating ourselves). All four hold.
+ *
+ * ## What is deliberately absent
+ *
+ * No `setRequestUpdateOwnership(true)`. It reads like the right declaration for
+ * a self-updater and it is not: ownership can only be claimed on **initial**
+ * installation — setting it on an update is documented as a no-op — and it also
+ * wants the privileged `ENFORCE_UPDATE_OWNERSHIP` permission. It exists for app
+ * stores claiming the apps they install, not for an app updating itself.
+ */
+@Singleton
+class SelfUpdateSession @Inject constructor(
+    @ApplicationContext private val context: Context,
+) {
+    /**
+     * Stage [apk] and hand it to the platform, suspending until a terminal
+     * verdict arrives.
+     *
+     * Never returns on the happy path when the install is silent: the platform
+     * replaces this process the moment the new APK lands, so the coroutine dies
+     * rather than resuming. Callers must treat that as success, not a hang.
+     */
+    suspend fun run(apk: File): InstallOutcome {
+        val staged = withContext(Dispatchers.IO) { runCatching { stage(apk) } }
+        return staged.fold(
+            onSuccess = { sessionId -> awaitCommit(sessionId) },
+            onFailure = { InstallOutcome.Failed(it.message) },
+        )
+    }
+
+    /** Open a session, stream the APK in, return the session id. */
+    private fun stage(apk: File): Int {
+        val installer = context.packageManager.packageInstaller
+        val sessionId = installer.createSession(newParams())
+        installer.openSession(sessionId).use { session ->
+            session.openWrite(STAGED_APK_NAME, WRITE_FROM_START, apk.length()).use { sink ->
+                apk.inputStream().use { source -> source.copyTo(sink) }
+                // fsync before the session closes: the platform validates the
+                // staged bytes at commit, and buffered tail bytes read as a
+                // truncated APK.
+                session.fsync(sink)
+            }
+        }
+        return sessionId
+    }
+
+    // Explicit `params.` receivers rather than an apply {} block: lintVitalRelease
+    // runs on assembleRelease, and NewApi is easier for it to reason about when
+    // the guarded call has a named receiver instead of an implicit one.
+    private fun newParams(): PackageInstaller.SessionParams {
+        val params = PackageInstaller.SessionParams(
+            PackageInstaller.SessionParams.MODE_FULL_INSTALL,
+        )
+        params.setAppPackageName(context.packageName)
+        params.setInstallReason(PackageManager.INSTALL_REASON_USER)
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
+            // The whole point of this class. Pre-S there is no such API, so the
+            // confirm dialog is unavoidable there — degrade, don't fail.
+            params.setRequireUserAction(PackageInstaller.SessionParams.USER_ACTION_NOT_REQUIRED)
+        }
+        return params
+    }
+
+    /**
+     * Commit the session and wait for the platform to report back.
+     *
+     * A pending-user-action status is *not* terminal — the platform is asking us
+     * to show its dialog, and the real verdict arrives in a second broadcast
+     * once the user decides. So the receiver stays registered across it.
+     */
+    private suspend fun awaitCommit(sessionId: Int): InstallOutcome =
+        suspendCancellableCoroutine { continuation ->
+            val installer = context.packageManager.packageInstaller
+            val receiver = object : BroadcastReceiver() {
+                override fun onReceive(unused: Context, intent: Intent) {
+                    val status = intent.getIntExtra(
+                        PackageInstaller.EXTRA_STATUS,
+                        PackageInstaller.STATUS_FAILURE,
+                    )
+                    if (status == PackageInstaller.STATUS_PENDING_USER_ACTION) {
+                        confirmWithUser(intent)
+                    } else {
+                        context.unregisterReceiver(this)
+                        val why = intent.getStringExtra(PackageInstaller.EXTRA_STATUS_MESSAGE)
+                        if (continuation.isActive) continuation.resume(outcomeOf(status, why))
+                    }
+                }
+            }
+            ContextCompat.registerReceiver(
+                context,
+                receiver,
+                IntentFilter(RESULT_ACTION),
+                ContextCompat.RECEIVER_NOT_EXPORTED,
+            )
+            continuation.invokeOnCancellation {
+                // Stop listening, but deliberately do NOT abandon the session.
+                // Cancellation here means our caller's scope died — the user
+                // navigated away, or the VM cleared — and by this point the
+                // session is already committed. The user asked for this install;
+                // killing it because nobody is watching the banner any more
+                // would be the wrong reading of their intent.
+                runCatching { context.unregisterReceiver(receiver) }
+            }
+            runCatching {
+                installer.openSession(sessionId).use { it.commit(resultSender(sessionId)) }
+            }.onFailure { error ->
+                // Resuming normally means invokeOnCancellation never fires, so
+                // clean up the staged session here or it sits until it expires.
+                runCatching { context.unregisterReceiver(receiver) }
+                runCatching { installer.abandonSession(sessionId) }
+                if (continuation.isActive) {
+                    continuation.resume(InstallOutcome.Failed(error.message))
+                }
+            }
+        }
+
+    private fun resultSender(sessionId: Int): IntentSender {
+        // Scoped to our own package so the broadcast can't be answered elsewhere.
+        val intent = Intent(RESULT_ACTION).setPackage(context.packageName)
+        var flags = PendingIntent.FLAG_UPDATE_CURRENT
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
+            // The platform writes its status extras into this intent, so it has
+            // to stay mutable — FLAG_IMMUTABLE would arrive with none of them.
+            flags = flags or PendingIntent.FLAG_MUTABLE
+        }
+        // Session id as the request code keeps concurrent sessions from
+        // colliding on FLAG_UPDATE_CURRENT.
+        return PendingIntent.getBroadcast(context, sessionId, intent, flags).intentSender
+    }
+
+    /**
+     * Show the platform's own confirm dialog, which arrives as an extra.
+     *
+     * The system-app check is not ceremony. Below API 34 a dynamically
+     * registered receiver cannot declare itself unexported, so another app on
+     * the device can broadcast [RESULT_ACTION] at us — and calling
+     * `startActivity` on an attacker-supplied extra would hand it whatever we
+     * can reach. The genuine confirm activity belongs to the platform
+     * installer, so demanding a system component costs the real path nothing.
+     */
+    private fun confirmWithUser(result: Intent) {
+        val pending = IntentCompat.getParcelableExtra(
+            result,
+            Intent.EXTRA_INTENT,
+            Intent::class.java,
+        ) ?: return
+        if (isPlatformActivity(pending)) {
+            context.startActivity(pending.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK))
+        }
+    }
+
+    private fun isPlatformActivity(intent: Intent): Boolean {
+        val flags = intent.resolveActivityInfo(context.packageManager, 0)
+            ?.applicationInfo
+            ?.flags
+            ?: 0
+        val systemFlags = ApplicationInfo.FLAG_SYSTEM or ApplicationInfo.FLAG_UPDATED_SYSTEM_APP
+        return (flags and systemFlags) != 0
+    }
+
+    private fun outcomeOf(status: Int, message: String?): InstallOutcome = when (status) {
+        PackageInstaller.STATUS_SUCCESS -> InstallOutcome.Installed
+        PackageInstaller.STATUS_FAILURE_ABORTED -> InstallOutcome.Cancelled
+        else -> InstallOutcome.Failed(message)
+    }
+}

android/app/src/main/java/com/fabledsword/minstrel/update/ui/UpdateBanner.kt

@@ -28,6 +28,8 @@ import com.composables.icons.lucide.Download
 import com.composables.icons.lucide.Lucide
 import com.composables.icons.lucide.X
 import com.fabledsword.minstrel.models.UpdateInfo
+import com.fabledsword.minstrel.update.data.InstallStage
+import com.fabledsword.minstrel.update.data.isBusy
 
 /**
  * Shell-level soft banner that nudges an available update. Renders
@@ -79,7 +81,7 @@ private fun BannerBody(
             .padding(start = 16.dp, top = 8.dp, end = 4.dp, bottom = 8.dp),
     ) {
         BannerRow(info = info, stage = stage, onInstall = onInstall, onDismiss = onDismiss)
-        if (stage == InstallStage.DOWNLOADING) {
+        if (stage.isBusy()) {
             LinearProgressIndicator(
                 modifier = Modifier
                     .fillMaxWidth()
@@ -124,8 +126,17 @@ private fun BannerRow(
             color = MaterialTheme.colorScheme.onSurfaceVariant,
             modifier = Modifier.weight(1f),
         )
-        TextButton(onClick = onInstall, enabled = stage != InstallStage.DOWNLOADING) {
-            Text(if (stage == InstallStage.DOWNLOADING) "Installing…" else "Install")
+        TextButton(onClick = onInstall, enabled = !stage.isBusy()) {
+            // Downloading and installing are separate words because they're now
+            // separate waits — the install half suspends on the platform, which
+            // may be sitting on a confirm dialog.
+            Text(
+                when (stage) {
+                    InstallStage.DOWNLOADING -> "Downloading…"
+                    InstallStage.INSTALLING -> "Installing…"
+                    else -> "Install"
+                },
+            )
         }
         IconButton(onClick = onDismiss) {
             Icon(

android/app/src/main/java/com/fabledsword/minstrel/update/ui/UpdateBannerViewModel.kt

@@ -5,7 +5,11 @@ import androidx.lifecycle.viewModelScope
 import com.fabledsword.minstrel.api.ErrorCopy
 import com.fabledsword.minstrel.models.UpdateInfo
 import com.fabledsword.minstrel.update.data.ApkInstaller
+import com.fabledsword.minstrel.update.data.InstallStage
 import com.fabledsword.minstrel.update.data.UpdateBannerController
+import com.fabledsword.minstrel.update.data.isBusy
+import com.fabledsword.minstrel.update.data.message
+import com.fabledsword.minstrel.update.data.stage
 import dagger.hilt.android.lifecycle.HiltViewModel
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.SharingStarted
@@ -13,13 +17,11 @@ import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.launch
+import java.io.File
 import javax.inject.Inject
 
 private const val SHARE_STOP_TIMEOUT_MS = 5_000L
 
-/** Install lifecycle for the banner's Install button. */
-enum class InstallStage { IDLE, DOWNLOADING, ERROR }
-
 data class UpdateBannerUiState(
     val info: UpdateInfo? = null,
     val stage: InstallStage = InstallStage.IDLE,
@@ -28,9 +30,9 @@ data class UpdateBannerUiState(
 
 /**
  * Thin VM over [UpdateBannerController]. Surfaces the available update
- * and runs the download → system-install handoff via [ApkInstaller],
- * mirroring the About card's flow (route to "install unknown apps"
- * settings first when the permission is missing).
+ * and runs the download → install handoff via [ApkInstaller], mirroring
+ * the About card's flow (route to "install unknown apps" settings first
+ * when the permission is missing).
  */
 @HiltViewModel
 class UpdateBannerViewModel @Inject constructor(
@@ -38,7 +40,7 @@ class UpdateBannerViewModel @Inject constructor(
     private val installer: ApkInstaller,
 ) : ViewModel() {
 
-    private val installState = MutableStateFlow(IdleInstall)
+    private val installState = MutableStateFlow(InstallSnapshot(InstallStage.IDLE, null))
 
     val uiState: StateFlow<UpdateBannerUiState> =
         combine(controller.available, installState) { info, install ->
@@ -52,7 +54,7 @@ class UpdateBannerViewModel @Inject constructor(
     fun dismiss(version: String) = controller.dismiss(version)
 
     fun install(info: UpdateInfo) {
-        if (installState.value.stage == InstallStage.DOWNLOADING) return
+        if (installState.value.stage.isBusy()) return
         if (!installer.canInstall()) {
             installer.requestInstallPermission()
             installState.value = InstallSnapshot(
@@ -63,21 +65,28 @@ class UpdateBannerViewModel @Inject constructor(
         }
         viewModelScope.launch {
             installState.value = InstallSnapshot(InstallStage.DOWNLOADING, null)
-            runCatching { installer.downloadApk(info.apkUrl) }
-                .onSuccess { apk ->
-                    installer.launchInstall(apk)
-                    installState.value = IdleInstall
-                }
-                .onFailure { e ->
-                    installState.value = InstallSnapshot(
-                        InstallStage.ERROR,
-                        "Couldn't download update: ${ErrorCopy.fromThrowable(e)}",
-                    )
-                }
+            val apk = download(info.apkUrl)
+            if (apk != null) {
+                // Await the platform's verdict rather than firing an intent and
+                // assuming it worked. On a silent install this suspends until
+                // the process is replaced, so the line below is only reached
+                // when the install did NOT simply succeed.
+                installState.value = InstallSnapshot(InstallStage.INSTALLING, null)
+                val outcome = installer.install(apk)
+                installState.value = InstallSnapshot(outcome.stage(), outcome.message())
+            }
         }
     }
+
+    private suspend fun download(apkUrl: String): File? =
+        runCatching { installer.downloadApk(apkUrl) }
+            .onFailure { e ->
+                installState.value = InstallSnapshot(
+                    InstallStage.ERROR,
+                    "Couldn't download update: ${ErrorCopy.fromThrowable(e)}",
+                )
+            }
+            .getOrNull()
 }
 
 private data class InstallSnapshot(val stage: InstallStage, val message: String?)
-
-private val IdleInstall = InstallSnapshot(InstallStage.IDLE, null)

android/app/src/main/res/xml/file_paths.xml

@@ -1,9 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<paths>
-    <!-- The downloaded update APK lives in the app cache dir; the
-         FileProvider exposes just that directory to the system
-         installer via a content:// URI. -->
-    <cache-path
-        name="updates"
-        path="." />
-</paths>