diff --git a/src/commander_ai_lab/deck_builder/core/__init__.py b/src/commander_ai_lab/deck_builder/core/__init__.py
new file mode 100644
index 0000000..fd00f54
--- /dev/null
+++ b/src/commander_ai_lab/deck_builder/core/__init__.py
@@ -0,0 +1 @@
+# core subpackage