diff --git a/infrastructure/factory.py b/infrastructure/factory.py
index c79845f..a1814eb 100644
--- a/infrastructure/factory.py
+++ b/infrastructure/factory.py
@@ -8,7 +8,14 @@ from typing import Callable, Awaitable, Sequence
 from quart import Quart, request, g, send_from_directory
 
 from shared.config import init_config, config, pretty
-from shared.models import KV  # ensure models imported
+from shared.models import KV  # ensure shared models imported
+# Register all app model classes with SQLAlchemy so cross-domain
+# relationship() string references resolve correctly.
+for _mod in ("blog.models", "market.models", "cart.models", "events.models"):
+    try:
+        __import__(_mod)
+    except ImportError:
+        pass
 from shared.log_config import configure_logging
 from shared.events import EventProcessor