Test terminal generation resume boundary

android/app/src/main/java/com/labfytools/trainlog/data/SyncGenerationForegroundCoordinator.kt

@@ -17,7 +17,7 @@ internal sealed interface ForegroundGenerationResult {
 internal class SyncGenerationForegroundCoordinator(private val repository: TrainlogRepository) {
     private val service = SyncGenerationService(repository)
 
-    private fun resumableGeneration(runId: String, consumerPeerId: String? = null): CapturedSyncGeneration? =
+    internal fun resumableGeneration(runId: String, consumerPeerId: String? = null): CapturedSyncGeneration? =
         repository.inSyncGenerationTransaction { db ->
             db.rawQuery(
                 "SELECT generation_id,manifest_sha256,staging_path FROM sync_generations " +
@@ -209,9 +209,9 @@ internal class SyncGenerationForegroundCoordinator(private val repository: Train
              * CONTRACT: an explicit retry for the same run republishes that
              * exact generation and resumes ACK handling; it never recaptures
              * mutable application state under an existing identity.
-             * INVARIANT: only an active generation for the correlated desktop
+             * INVARIANT: a completed inbound ledger makes the run ineligible;
-             * consumer is resumable; acknowledged or archived runs remain
+             * an acknowledged outbound generation remains resumable only to
-             * excluded from new foreground work. */
+             * finish its missing inbound half. */
             val captured =
                 resumableGeneration(
                     request.getString("run_id"),

android/app/src/test/java/com/labfytools/trainlog/data/SyncGenerationServiceTest.kt

@@ -26,6 +26,54 @@ import org.robolectric.annotation.Config
 class SyncGenerationServiceTest {
     private val context: Context = ApplicationProvider.getApplicationContext()
 
+    @Test
+    fun acknowledgedOutboundRemainsResumableUntilInboundIsTerminal() {
+        val sourceName = "generation-resume-source-${UUID.randomUUID()}.db"
+        val destinationName = "generation-resume-destination-${UUID.randomUUID()}.db"
+        val root = Files.createTempDirectory("trainlog-generation-resume-").toFile()
+        val source = TrainlogRepository(context, sourceName)
+        val destination = TrainlogRepository(context, destinationName)
+        try {
+            val sourceService = SyncGenerationService(source)
+            val destinationService = SyncGenerationService(destination)
+            val runId = "sy_${UUID.randomUUID()}"
+            val outbound =
+                sourceService.capture(
+                    java.io.File(root, "source-owned"),
+                    destinationService.peerId(),
+                    runId,
+                )
+            val outboundDirectory =
+                sourceService.publish(outbound, java.io.File(root, "source-objects"))
+            sourceService.acceptAcknowledgement(
+                destinationService.consume(outboundDirectory).toByteArray()
+            )
+
+            val coordinator = SyncGenerationForegroundCoordinator(source)
+            assertEquals(
+                outbound.generationId,
+                coordinator.resumableGeneration(runId, destinationService.peerId())?.generationId,
+            )
+
+            val inbound =
+                destinationService.capture(
+                    java.io.File(root, "destination-owned"),
+                    sourceService.peerId(),
+                    runId,
+                )
+            sourceService.consume(
+                destinationService.publish(inbound, java.io.File(root, "destination-objects"))
+            )
+            assertEquals(null, coordinator.resumableGeneration(runId, destinationService.peerId()))
+        } finally {
+            source.close()
+            destination.close()
+            context.deleteDatabase(sourceName)
+            context.deleteDatabase(destinationName)
+            root.deleteRecursively()
+        }
+    }
+
     @Test
     fun v19MigrationPreservesDataAndInventsNoGenerationState() {
         val name = "generation-migration-${UUID.randomUUID()}.db"