feat(android-terminal): Phase E — offline queue + sync

Stamp / earn / enroll actions performed without connectivity now persist
in the existing pending_transactions Room table and drain via a
SyncWorker as soon as the network constraint is satisfied. Redemption
stays online-only (server needs the authoritative balance — queueing
would let cashiers redeem rewards customers have already spent).

Pieces:

- Hilt-Work plumbing: androidx.hilt:hilt-compiler KSP processor wired,
  RewardFlowApp now implements Configuration.Provider with the injected
  HiltWorkerFactory, AndroidManifest disables the WorkManager auto-init
  via the AndroidX startup tools:node="remove" pattern. Bumped Dagger
  to 2.55 so its compiler can read Kotlin 2.1 metadata — 2.51 crashed
  with "Unable to read Kotlin metadata due to unsupported metadata
  version" once we added @Inject lateinit var on the Application class.

- data/sync/SyncWorker.kt — @HiltWorker CoroutineWorker that drains the
  queue FIFO. Per row: HTTP error → permanent markFailed; IOException
  → Result.retry(); success → markSynced + sweep at end of run.

- data/repository/QueueRepository.kt — single entrypoint for "queue
  this offline action". queueStamp / queuePointsEarn / queueEnroll
  Moshi-serialize the request body and enqueueUniqueWork(KEEP) the
  worker under a NetworkType.CONNECTED constraint with 30s exponential
  backoff. scheduleSync() is idempotent.

- TerminalViewModel: runAction(block, queueOnNetworkFailure) — on
  IOException AND a queue lambda is provided, queue + emit
  ActionResult.Queued. HttpException paths still surface the server's
  message inline. Stamp / Earn / Enroll go through the queue path;
  redeem actions pass null. setStaffPinId records who initiated each
  queued row. init schedules a sync so anything left from a previous
  session drains on screen entry. pendingSyncCount is combined into
  state via Flow<Int> from the DAO; when it drops to 0 we refresh the
  recent-transactions feed so the UI shows what just synced.

- TerminalScreen: PendingSyncPill in the top bar (only visible when
  count > 0) gives the cashier feedback that a queued action is
  waiting + that the queue is draining live.

Cleartext + readable HTTP errors from yesterday remain in.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

clients/terminal-android/app/build.gradle.kts

@@ -90,6 +90,7 @@ dependencies {
     ksp(libs.hilt.compiler)
     implementation(libs.hilt.navigation.compose)
     implementation(libs.hilt.work)
+    ksp(libs.androidx.hilt.compiler)
 
     // CameraX + ML Kit (QR scanning)
     implementation(libs.camera.core)

clients/terminal-android/app/src/main/AndroidManifest.xml

@@ -19,6 +19,19 @@
         android:theme="@style/Theme.RewardFlowTerminal"
         tools:targetApi="35">
 
+        <!-- Disable WorkManager's default initializer; RewardFlowApp
+             implements Configuration.Provider with the HiltWorkerFactory. -->
+        <provider
+            android:name="androidx.startup.InitializationProvider"
+            android:authorities="${applicationId}.androidx-startup"
+            android:exported="false"
+            tools:node="merge">
+            <meta-data
+                android:name="androidx.work.WorkManagerInitializer"
+                android:value="androidx.startup"
+                tools:node="remove" />
+        </provider>
+
         <activity
             android:name=".MainActivity"
             android:exported="true"

clients/terminal-android/app/src/main/java/lu/rewardflow/terminal/RewardFlowApp.kt

@@ -1,7 +1,27 @@
 package lu.rewardflow.terminal
 
 import android.app.Application
+import androidx.hilt.work.HiltWorkerFactory
+import androidx.work.Configuration
 import dagger.hilt.android.HiltAndroidApp
+import javax.inject.Inject
 
+/**
+ * Application entry point. Wires Hilt's [HiltWorkerFactory] into
+ * WorkManager so [@HiltWorker] classes get constructor injection.
+ *
+ * The default WorkManager auto-initializer is disabled in the manifest
+ * (see ``<provider>`` removal under ``androidx.startup``); WorkManager
+ * picks up our [Configuration] via this provider on first access.
+ */
 @HiltAndroidApp
-class RewardFlowApp : Application()
+class RewardFlowApp : Application(), Configuration.Provider {
+
+    @Inject
+    lateinit var workerFactory: HiltWorkerFactory
+
+    override val workManagerConfiguration: Configuration
+        get() = Configuration.Builder()
+            .setWorkerFactory(workerFactory)
+            .build()
+}

clients/terminal-android/app/src/main/java/lu/rewardflow/terminal/data/repository/QueueRepository.kt

@@ -0,0 +1,100 @@
+package lu.rewardflow.terminal.data.repository
+
+import android.content.Context
+import androidx.work.BackoffPolicy
+import androidx.work.Constraints
+import androidx.work.ExistingWorkPolicy
+import androidx.work.NetworkType
+import androidx.work.OneTimeWorkRequestBuilder
+import androidx.work.WorkManager
+import com.squareup.moshi.Moshi
+import dagger.hilt.android.qualifiers.ApplicationContext
+import lu.rewardflow.terminal.data.db.dao.PendingTransactionDao
+import lu.rewardflow.terminal.data.db.entity.PendingTransaction
+import lu.rewardflow.terminal.data.model.EnrollRequest
+import lu.rewardflow.terminal.data.model.PointsEarnRequest
+import lu.rewardflow.terminal.data.model.StampRequest
+import lu.rewardflow.terminal.data.sync.SyncWorker
+import java.util.concurrent.TimeUnit
+import javax.inject.Inject
+import javax.inject.Singleton
+
+/**
+ * Single entrypoint for "queue an action that failed offline".
+ *
+ * The terminal screen calls one of [queueStamp] / [queuePointsEarn] /
+ * [queueEnroll] after detecting an [java.io.IOException] mid-action.
+ * The body is serialized to JSON, persisted via [PendingTransactionDao],
+ * and a [SyncWorker] is enqueued under a network constraint so the
+ * system runs it as soon as connectivity returns.
+ *
+ * Redemption flows are NOT queued here — the plan calls for them to
+ * stay online-only since balances at redeem time can't be retro'd.
+ */
+@Singleton
+class QueueRepository @Inject constructor(
+    @ApplicationContext private val context: Context,
+    private val dao: PendingTransactionDao,
+    moshi: Moshi,
+) {
+    private val stampAdapter = moshi.adapter(StampRequest::class.java)
+    private val earnAdapter = moshi.adapter(PointsEarnRequest::class.java)
+    private val enrollAdapter = moshi.adapter(EnrollRequest::class.java)
+
+    suspend fun queueStamp(request: StampRequest, staffPinId: Int) {
+        dao.insert(
+            PendingTransaction(
+                type = SyncWorker.TYPE_STAMP,
+                requestJson = stampAdapter.toJson(request),
+                staffPinId = staffPinId,
+            )
+        )
+        scheduleSync()
+    }
+
+    suspend fun queuePointsEarn(request: PointsEarnRequest, staffPinId: Int) {
+        dao.insert(
+            PendingTransaction(
+                type = SyncWorker.TYPE_POINTS_EARN,
+                requestJson = earnAdapter.toJson(request),
+                staffPinId = staffPinId,
+            )
+        )
+        scheduleSync()
+    }
+
+    suspend fun queueEnroll(request: EnrollRequest, staffPinId: Int) {
+        dao.insert(
+            PendingTransaction(
+                type = SyncWorker.TYPE_ENROLL,
+                requestJson = enrollAdapter.toJson(request),
+                staffPinId = staffPinId,
+            )
+        )
+        scheduleSync()
+    }
+
+    /** Kick the sync worker. Idempotent — KEEP policy means a queued or
+     *  running request isn't displaced. The system runs us when the
+     *  network constraint is satisfied. */
+    fun scheduleSync() {
+        val constraints = Constraints.Builder()
+            .setRequiredNetworkType(NetworkType.CONNECTED)
+            .build()
+
+        val request = OneTimeWorkRequestBuilder<SyncWorker>()
+            .setConstraints(constraints)
+            .setBackoffCriteria(BackoffPolicy.EXPONENTIAL, 30, TimeUnit.SECONDS)
+            .build()
+
+        WorkManager.getInstance(context).enqueueUniqueWork(
+            UNIQUE_SYNC_WORK_NAME,
+            ExistingWorkPolicy.KEEP,
+            request,
+        )
+    }
+
+    companion object {
+        const val UNIQUE_SYNC_WORK_NAME = "loyalty_sync"
+    }
+}

clients/terminal-android/app/src/main/java/lu/rewardflow/terminal/data/sync/SyncWorker.kt

@@ -0,0 +1,134 @@
+package lu.rewardflow.terminal.data.sync
+
+import android.content.Context
+import android.util.Log
+import androidx.hilt.work.HiltWorker
+import androidx.work.CoroutineWorker
+import androidx.work.WorkerParameters
+import com.squareup.moshi.Moshi
+import dagger.assisted.Assisted
+import dagger.assisted.AssistedInject
+import lu.rewardflow.terminal.data.api.LoyaltyApi
+import lu.rewardflow.terminal.data.db.dao.PendingTransactionDao
+import lu.rewardflow.terminal.data.db.entity.PendingTransaction
+import lu.rewardflow.terminal.data.model.EnrollRequest
+import lu.rewardflow.terminal.data.model.PointsEarnRequest
+import lu.rewardflow.terminal.data.model.StampRequest
+import retrofit2.HttpException
+import java.io.IOException
+
+/**
+ * Drains the `pending_transactions` queue against the loyalty API.
+ *
+ * Scheduled by [QueueRepository.scheduleSync] when:
+ * - A new action is queued (immediate try)
+ * - The system reports the network became available again
+ *
+ * Behavior per row:
+ * - HTTP success → mark synced, deleted at the end of the run.
+ * - [HttpException] (4xx/5xx) → permanent fail; the action's data is
+ *   stale or rejected. Mark failed and stop retrying it.
+ * - [IOException] → transient (lost network mid-flight). Leave row in
+ *   `pending` and return `Result.retry()` so WorkManager re-runs us
+ *   under the network constraint with backoff.
+ *
+ * Order is FIFO by `createdAt` so a stamp queued before a redeem stays
+ * before a redeem in the run order — though we don't currently queue
+ * redeems anyway.
+ */
+@HiltWorker
+class SyncWorker @AssistedInject constructor(
+    @Assisted appContext: Context,
+    @Assisted workerParams: WorkerParameters,
+    private val dao: PendingTransactionDao,
+    private val api: LoyaltyApi,
+    private val moshi: Moshi,
+) : CoroutineWorker(appContext, workerParams) {
+
+    private val stampAdapter = moshi.adapter(StampRequest::class.java)
+    private val earnAdapter = moshi.adapter(PointsEarnRequest::class.java)
+    private val enrollAdapter = moshi.adapter(EnrollRequest::class.java)
+
+    override suspend fun doWork(): Result {
+        val pending = dao.getPending()
+        if (pending.isEmpty()) return Result.success()
+
+        var hadTransientFailure = false
+        for (tx in pending) {
+            when (process(tx)) {
+                ProcessOutcome.Synced -> dao.markSynced(tx.id)
+                ProcessOutcome.PermanentFailure -> {
+                    // markFailed() bumps retryCount + records the error.
+                    // Already handled inside process(). Move on to the next.
+                }
+                ProcessOutcome.Transient -> {
+                    hadTransientFailure = true
+                    // Stop draining — we've lost the network mid-run.
+                    break
+                }
+            }
+        }
+
+        // Sweep synced rows out of the table so the queue size stays
+        // bounded over a long-running offline session.
+        runCatching { dao.deleteSynced() }
+
+        return if (hadTransientFailure) Result.retry() else Result.success()
+    }
+
+    private suspend fun process(tx: PendingTransaction): ProcessOutcome {
+        return try {
+            when (tx.type) {
+                TYPE_STAMP -> {
+                    val req = stampAdapter.fromJson(tx.requestJson)
+                    if (req == null) {
+                        dao.markFailed(tx.id, "Malformed queued payload")
+                        return ProcessOutcome.PermanentFailure
+                    }
+                    api.addStamp(req)
+                }
+                TYPE_POINTS_EARN -> {
+                    val req = earnAdapter.fromJson(tx.requestJson)
+                    if (req == null) {
+                        dao.markFailed(tx.id, "Malformed queued payload")
+                        return ProcessOutcome.PermanentFailure
+                    }
+                    api.earnPoints(req)
+                }
+                TYPE_ENROLL -> {
+                    val req = enrollAdapter.fromJson(tx.requestJson)
+                    if (req == null) {
+                        dao.markFailed(tx.id, "Malformed queued payload")
+                        return ProcessOutcome.PermanentFailure
+                    }
+                    api.enrollCustomer(req)
+                }
+                else -> {
+                    dao.markFailed(tx.id, "Unknown type: ${tx.type}")
+                    return ProcessOutcome.PermanentFailure
+                }
+            }
+            ProcessOutcome.Synced
+        } catch (e: HttpException) {
+            Log.w(TAG, "HTTP ${e.code()} syncing tx ${tx.id} (${tx.type})", e)
+            dao.markFailed(tx.id, "HTTP ${e.code()}: ${e.message()}")
+            ProcessOutcome.PermanentFailure
+        } catch (e: IOException) {
+            Log.w(TAG, "Network error syncing tx ${tx.id} — will retry", e)
+            ProcessOutcome.Transient
+        } catch (e: Exception) {
+            Log.e(TAG, "Unexpected error syncing tx ${tx.id}", e)
+            dao.markFailed(tx.id, e.message ?: e::class.simpleName ?: "Unknown error")
+            ProcessOutcome.PermanentFailure
+        }
+    }
+
+    private enum class ProcessOutcome { Synced, PermanentFailure, Transient }
+
+    companion object {
+        const val TYPE_STAMP = "stamp"
+        const val TYPE_POINTS_EARN = "points_earn"
+        const val TYPE_ENROLL = "enroll"
+        private const val TAG = "SyncWorker"
+    }
+}

clients/terminal-android/app/src/main/java/lu/rewardflow/terminal/ui/terminal/TerminalScreen.kt

@@ -69,6 +69,10 @@ fun TerminalScreen(
 ) {
     val state by viewModel.state.collectAsStateWithLifecycle()
 
+    androidx.compose.runtime.LaunchedEffect(staffPinId) {
+        viewModel.setStaffPinId(staffPinId)
+    }
+
     IdleTracker(
         timeoutMillis = AUTO_LOCK_TIMEOUT_MS,
         onIdle = onLockScreen,
@@ -95,6 +99,7 @@ private fun TerminalContent(
         TopBar(
             staffName = staffName,
             isOnline = state.isOnline,
+            pendingSyncCount = state.pendingSyncCount,
             onLockScreen = onLockScreen,
         )
         Row(modifier = Modifier.fillMaxSize()) {
@@ -156,6 +161,7 @@ private fun TerminalContent(
 private fun TopBar(
     staffName: String,
     isOnline: Boolean,
+    pendingSyncCount: Int,
     onLockScreen: () -> Unit,
 ) {
     Surface(
@@ -173,6 +179,10 @@ private fun TopBar(
             )
             Spacer(Modifier.size(16.dp))
             OnlinePill(isOnline = isOnline)
+            if (pendingSyncCount > 0) {
+                Spacer(Modifier.size(8.dp))
+                PendingSyncPill(count = pendingSyncCount)
+            }
             Spacer(modifier = Modifier.weight(1f))
             FilledTonalButton(onClick = onLockScreen) {
                 Text(stringResource(R.string.terminal_lock))
@@ -181,6 +191,23 @@ private fun TopBar(
     }
 }
 
+@Composable
+private fun PendingSyncPill(count: Int) {
+    val color = MaterialTheme.colorScheme.tertiary
+    Surface(
+        shape = RoundedCornerShape(12.dp),
+        color = color.copy(alpha = 0.18f),
+    ) {
+        Text(
+            text = stringResource(R.string.pin_pending_sync, count),
+            color = color,
+            style = MaterialTheme.typography.labelSmall,
+            fontWeight = FontWeight.SemiBold,
+            modifier = Modifier.padding(horizontal = 10.dp, vertical = 4.dp),
+        )
+    }
+}
+
 @Composable
 private fun OnlinePill(isOnline: Boolean) {
     val (label, color) = if (isOnline)

clients/terminal-android/app/src/main/java/lu/rewardflow/terminal/ui/terminal/TerminalViewModel.kt

@@ -12,7 +12,9 @@ import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.flow.launchIn
 import kotlinx.coroutines.flow.onEach
 import kotlinx.coroutines.launch
+import kotlinx.coroutines.flow.combine
 import lu.rewardflow.terminal.data.api.LoyaltyApi
+import lu.rewardflow.terminal.data.db.dao.PendingTransactionDao
 import lu.rewardflow.terminal.data.model.CardLookupResponse
 import lu.rewardflow.terminal.data.model.CategoryItem
 import lu.rewardflow.terminal.data.model.EnrollRequest
@@ -25,7 +27,9 @@ import lu.rewardflow.terminal.data.model.TransactionItem
 import lu.rewardflow.terminal.data.network.NetworkMonitor
 import lu.rewardflow.terminal.data.repository.CategoryRepository
 import lu.rewardflow.terminal.data.repository.DeviceConfigRepository
+import lu.rewardflow.terminal.data.repository.QueueRepository
 import retrofit2.HttpException
+import java.io.IOException
 import javax.inject.Inject
 
 /**
@@ -47,10 +51,20 @@ class TerminalViewModel @Inject constructor(
     private val api: LoyaltyApi,
     private val configRepository: DeviceConfigRepository,
     private val categoryRepository: CategoryRepository,
+    private val queueRepository: QueueRepository,
+    pendingTransactionDao: PendingTransactionDao,
     networkMonitor: NetworkMonitor,
     moshi: Moshi,
 ) : ViewModel() {
 
+    /** Set by [TerminalScreen] from the route arguments so queued
+     *  transactions can record which staff initiated the offline action. */
+    private var currentStaffPinId: Int = 0
+
+    fun setStaffPinId(id: Int) {
+        currentStaffPinId = id
+    }
+
     private val programAdapter: JsonAdapter<ProgramResponse> =
         moshi.adapter(ProgramResponse::class.java)
 
@@ -61,8 +75,25 @@ class TerminalViewModel @Inject constructor(
         loadCachedProgram()
         loadCategories()
         refreshRecentTransactions()
-        networkMonitor.isOnline
+        // Kick the sync worker on every screen entry so anything queued in
-            .onEach { online -> _state.value = _state.value.copy(isOnline = online) }
+        // a previous session drains as soon as the network constraint is
+        // satisfied. Idempotent — KEEP policy in scheduleSync().
+        queueRepository.scheduleSync()
+
+        combine(
+            networkMonitor.isOnline,
+            pendingTransactionDao.getPendingCount(),
+        ) { online, pending -> online to pending }
+            .onEach { (online, pending) ->
+                _state.value = _state.value.copy(
+                    isOnline = online,
+                    pendingSyncCount = pending,
+                )
+                // When the count drops to 0 after being non-zero, the
+                // queue just drained; refresh the customer + feed so the
+                // UI reflects the synced changes.
+                if (pending == 0) refreshRecentTransactions()
+            }
             .launchIn(viewModelScope)
     }
 
@@ -140,9 +171,15 @@ class TerminalViewModel @Inject constructor(
     }
 
     /** Submit the enrollment form. ``birthday`` is expected as an ISO
-     *  ``YYYY-MM-DD`` string or null. The new card is looked up after
+     *  ``YYYY-MM-DD`` string or null.
-     *  enrollment so the customer pane renders with the full lookup
+     *
-     *  shape (rewards, can_stamp, cooldown, etc). */
+     *  Online: enrolls + re-fetches the lookup-shape card so the
+     *  customer pane renders fully.
+     *
+     *  Offline (IOException): queues the enrollment for later sync;
+     *  the dialog closes and the cashier sees a "queued" toast. The
+     *  customer pane is NOT pre-populated since we don't know the
+     *  card_number until the server assigns one. */
     fun submitEnroll(
         name: String,
         email: String,
@@ -154,22 +191,17 @@ class TerminalViewModel @Inject constructor(
             _state.value = _state.value.copy(enrollError = "Name and email are required")
             return
         }
+        val request = EnrollRequest(
+            email = email.trim(),
+            customer_name = name.trim(),
+            customer_phone = phone?.trim()?.takeIf { it.isNotBlank() },
+            customer_birthday = birthday?.trim()?.takeIf { it.isNotBlank() },
+        )
         _state.value = _state.value.copy(enrolling = true, enrollError = null)
         viewModelScope.launch {
-            val result = runCatching {
+            val result = runCatching { api.enrollCustomer(request) }
-                api.enrollCustomer(
-                    EnrollRequest(
-                        email = email.trim(),
-                        customer_name = name.trim(),
-                        customer_phone = phone?.trim()?.takeIf { it.isNotBlank() },
-                        customer_birthday = birthday?.trim()?.takeIf { it.isNotBlank() },
-                    )
-                )
-            }
             result.fold(
                 onSuccess = { card ->
-                    // Re-fetch with the lookup shape so the customer pane has
-                    // the full set of fields (rewards, cooldown, etc).
                     runCatching { api.lookupCard(card.card_number) }
                         .onSuccess { hydrated ->
                             _state.value = _state.value.copy(
@@ -180,9 +212,6 @@ class TerminalViewModel @Inject constructor(
                             refreshRecentTransactions()
                         }
                         .onFailure {
-                            // Card was enrolled — but we couldn't fetch the
-                            // hydrated view. Close the dialog anyway and let
-                            // the user search by the new card_number.
                             _state.value = _state.value.copy(
                                 enrolling = false,
                                 enrollDialogOpen = false,
@@ -191,10 +220,27 @@ class TerminalViewModel @Inject constructor(
                         }
                 },
                 onFailure = { err ->
-                    _state.value = _state.value.copy(
+                    if (err is IOException) {
-                        enrolling = false,
+                        runCatching { queueRepository.queueEnroll(request, currentStaffPinId) }
-                        enrollError = err.message ?: "Enrollment failed",
+                            .onSuccess {
-                    )
+                                _state.value = _state.value.copy(
+                                    enrolling = false,
+                                    enrollDialogOpen = false,
+                                    actionResult = ActionResult.Queued,
+                                )
+                            }
+                            .onFailure { qErr ->
+                                _state.value = _state.value.copy(
+                                    enrolling = false,
+                                    enrollError = qErr.message ?: "Could not queue enrollment",
+                                )
+                            }
+                    } else {
+                        _state.value = _state.value.copy(
+                            enrolling = false,
+                            enrollError = readableErrorMessage(err),
+                        )
+                    }
                 },
             )
         }
@@ -231,51 +277,78 @@ class TerminalViewModel @Inject constructor(
         )
     }
 
-    /** Add a stamp to the currently-selected card. */
+    /** Add a stamp to the currently-selected card. Queueable offline. */
-    fun submitStamp(categoryIds: List<Int>) = runAction {
+    fun submitStamp(categoryIds: List<Int>) {
-        val card = _state.value.customer ?: return@runAction
+        val card = _state.value.customer ?: return
-        val response = api.addStamp(
+        val request = StampRequest(
-            StampRequest(
+            card_id = card.id,
-                card_id = card.id,
+            category_ids = categoryIds.ifEmpty { null },
-                category_ids = categoryIds.ifEmpty { null },
+        )
+        runAction(
+            block = {
+                val response = api.addStamp(request)
+                if (!response.success) error("Server reported failure")
+            },
+            queueOnNetworkFailure = { queueRepository.queueStamp(request, currentStaffPinId) },
+        )
+    }
+
+    /** Earn points on a purchase. [amountCents] must be > 0. Queueable offline. */
+    fun submitEarnPoints(amountCents: Int, categoryIds: List<Int>) {
+        if (amountCents <= 0) {
+            _state.value = _state.value.copy(
+                actionResult = ActionResult.Failure("Amount must be greater than 0")
             )
+            return
+        }
+        val card = _state.value.customer ?: return
+        val request = PointsEarnRequest(
+            card_id = card.id,
+            purchase_amount_cents = amountCents,
+            category_ids = categoryIds.ifEmpty { null },
+        )
+        runAction(
+            block = {
+                val response = api.earnPoints(request)
+                if (!response.success) error("Server reported failure")
+            },
+            queueOnNetworkFailure = { queueRepository.queuePointsEarn(request, currentStaffPinId) },
         )
-        if (!response.success) error("Server reported failure")
     }
 
-    /** Earn points on a purchase. [amountCents] must be > 0. */
+    /** Redeem the stamp reward on the currently-selected card. Online-only. */
-    fun submitEarnPoints(amountCents: Int, categoryIds: List<Int>) = runAction {
+    fun submitRedeemStamps() = runAction(
-        if (amountCents <= 0) error("Amount must be greater than 0")
+        block = {
-        val card = _state.value.customer ?: return@runAction
+            val card = _state.value.customer ?: return@runAction
-        val response = api.earnPoints(
+            val response = api.redeemStamps(StampRedeemRequest(card_id = card.id))
-            PointsEarnRequest(
+            if (!response.success) error("Server reported failure")
-                card_id = card.id,
+        },
-                purchase_amount_cents = amountCents,
+        queueOnNetworkFailure = null,
-                category_ids = categoryIds.ifEmpty { null },
+    )
+
+    /** Redeem a points reward by id. Online-only. */
+    fun submitRedeemReward(rewardId: String) = runAction(
+        block = {
+            val card = _state.value.customer ?: return@runAction
+            val response = api.redeemPoints(
+                PointsRedeemRequest(card_id = card.id, reward_id = rewardId)
             )
-        )
+            if (!response.success) error("Server reported failure")
-        if (!response.success) error("Server reported failure")
+        },
-    }
+        queueOnNetworkFailure = null,
+    )
 
-    /** Redeem the stamp reward on the currently-selected card. */
+    /**
-    fun submitRedeemStamps() = runAction {
+     * Run [block] online. On [IOException] (lost network mid-call) and
-        val card = _state.value.customer ?: return@runAction
+     * with a non-null [queueOnNetworkFailure], the action is queued via
-        val response = api.redeemStamps(
+     * [QueueRepository] and the dialog reports queued-success. On
-            StampRedeemRequest(card_id = card.id)
+     * [HttpException] / other failures the dialog surfaces the server's
-        )
+     * message — those are real errors, not connectivity blips.
-        if (!response.success) error("Server reported failure")
+     */
-    }
+    private fun runAction(
-
+        block: suspend () -> Unit,
-    /** Redeem a points reward by id. */
+        queueOnNetworkFailure: (suspend () -> Unit)?,
-    fun submitRedeemReward(rewardId: String) = runAction {
+    ) {
-        val card = _state.value.customer ?: return@runAction
-        val response = api.redeemPoints(
-            PointsRedeemRequest(card_id = card.id, reward_id = rewardId)
-        )
-        if (!response.success) error("Server reported failure")
-    }
-
-    private fun runAction(block: suspend () -> Unit) {
         if (_state.value.actionInProgress) return
         _state.value = _state.value.copy(
             actionInProgress = true,
@@ -291,14 +364,34 @@ class TerminalViewModel @Inject constructor(
                 )
                 refreshCurrentCustomer()
                 refreshRecentTransactions()
-            } else {
+                return@launch
-                _state.value = _state.value.copy(
-                    actionInProgress = false,
-                    actionResult = ActionResult.Failure(
-                        readableErrorMessage(result.exceptionOrNull())
-                    ),
-                )
             }
+
+            val err = result.exceptionOrNull()
+            if (err is IOException && queueOnNetworkFailure != null) {
+                runCatching { queueOnNetworkFailure() }
+                    .onSuccess {
+                        _state.value = _state.value.copy(
+                            actionInProgress = false,
+                            actionResult = ActionResult.Queued,
+                            activeAction = null,
+                        )
+                    }
+                    .onFailure { qErr ->
+                        _state.value = _state.value.copy(
+                            actionInProgress = false,
+                            actionResult = ActionResult.Failure(
+                                qErr.message ?: "Could not queue offline"
+                            ),
+                        )
+                    }
+                return@launch
+            }
+
+            _state.value = _state.value.copy(
+                actionInProgress = false,
+                actionResult = ActionResult.Failure(readableErrorMessage(err)),
+            )
         }
     }
 
@@ -386,11 +479,17 @@ data class TerminalUiState(
     val enrollDialogOpen: Boolean = false,
     val enrolling: Boolean = false,
     val enrollError: String? = null,
+    val pendingSyncCount: Int = 0,
 )
 
 enum class ActionKind { AddStamp, EarnPoints, RedeemStamps, RedeemReward }
 
 sealed interface ActionResult {
     data object Success : ActionResult
+
+    /** The action couldn't reach the server but was queued in Room and
+     *  will sync when connectivity returns. The cashier sees a "queued"
+     *  message instead of a hard failure. */
+    data object Queued : ActionResult
     data class Failure(val message: String) : ActionResult
 }

clients/terminal-android/gradle/libs.versions.toml

@@ -34,7 +34,11 @@ room = "2.6.1"
 workManager = "2.10.0"
 
 # Dependency Injection
-hilt = "2.51.1"
+# Dagger 2.55 added support for Kotlin 2.1 metadata. Older versions
+# (2.51 and below) crash when Dagger validates @Inject fields on classes
+# compiled by the Kotlin 2.1 toolchain — surfaces as
+# "Unable to read Kotlin metadata due to unsupported metadata version".
+hilt = "2.55"
 hiltNavigationCompose = "1.2.0"
 
 # Camera & QR scanning
@@ -92,6 +96,10 @@ hilt-android = { group = "com.google.dagger", name = "hilt-android", version.ref
 hilt-compiler = { group = "com.google.dagger", name = "hilt-android-compiler", version.ref = "hilt" }
 hilt-navigation-compose = { group = "androidx.hilt", name = "hilt-navigation-compose", version.ref = "hiltNavigationCompose" }
 hilt-work = { group = "androidx.hilt", name = "hilt-work", version.ref = "hiltNavigationCompose" }
+# Annotation processor for @HiltWorker — separate from the Dagger compiler
+# above. Generates the WorkerFactory binding so workers get constructor
+# injection like every other @Inject class.
+androidx-hilt-compiler = { group = "androidx.hilt", name = "hilt-compiler", version.ref = "hiltNavigationCompose" }
 
 # CameraX (QR scanning)
 camera-core = { group = "androidx.camera", name = "camera-core", version.ref = "cameraX" }