diff --git a/android/app/src/main/java/com/labfytools/trainlog/ui/SyncScreen.kt b/android/app/src/main/java/com/labfytools/trainlog/ui/SyncScreen.kt
index e925e3c..f830f1d 100644
--- a/android/app/src/main/java/com/labfytools/trainlog/ui/SyncScreen.kt
+++ b/android/app/src/main/java/com/labfytools/trainlog/ui/SyncScreen.kt
@@ -55,6 +55,16 @@ internal suspend fun publishBundleAndRequest(
         return@withContext SyncRequestResult.Error("prepare:${opened.message}")
     }
     val snapshot = (opened as com.labfytools.trainlog.data.DirectExchangeSnapshotResult.Ready).snapshot
+    /* CONTRACT: the request signal remains compatible with an unconfigured
+     * desktop, so publish the strict standalone V3 snapshot before admission.
+     * A configured daemon still routes the signal exclusively to the complete
+     * generation below; this compatibility publication never selects V3. */
+    when (val publication = exporter.exportMobileBundle(snapshot)) {
+        SyncExportResult.Unsupported -> return@withContext SyncRequestResult.Unsupported
+        is SyncExportResult.Error ->
+            return@withContext SyncRequestResult.Error("prepare:${publication.message}")
+        is SyncExportResult.Exported -> Unit
+    }
     return@withContext when (
         val result = SyncGenerationForegroundCoordinator(repository).run(
             canonicalExchangeDirectory(),
diff --git a/tests/test_syncd_routing.py b/tests/test_syncd_routing.py
index cdd7209..70c72de 100644
--- a/tests/test_syncd_routing.py
+++ b/tests/test_syncd_routing.py
@@ -81,7 +81,8 @@ class SyncdRoutingTest(unittest.TestCase):
         )[0]
         self.assertIn("SyncGenerationForegroundCoordinator(repository).run", production)
         self.assertNotIn("generation-opt-in", production)
-        self.assertNotIn("exportMobileBundle", production)
+        self.assertIn("exportMobileBundle", production)
+        self.assertIn("generation below", production)
 
 
 if __name__ == "__main__":