fix: use kwargs registry directly and store it correctly in model_config

sqlmodel/main.py

@@ -613,11 +613,11 @@ def get_config(name: str) -> Any:
             # TODO: remove this in the future
             new_cls.model_config["read_with_orm_mode"] = True  # ty: ignore[invalid-key]
 
-        config_registry = get_config("registry")
+        config_registry = kwargs.get("registry", Undefined)
         if config_registry is not Undefined:
             config_registry = cast(registry, config_registry)
             # If it was passed by kwargs, ensure it's also set in config
-            new_cls.model_config["registry"] = config_table
+            new_cls.model_config["registry"] = config_registry
             setattr(new_cls, "_sa_registry", config_registry)  # noqa: B010
             setattr(new_cls, "metadata", config_registry.metadata)  # noqa: B010
             setattr(new_cls, "__abstract__", True)  # noqa: B010

tests/test_registry_kwarg.py

@@ -0,0 +1,30 @@
+"""Tests for SQLModelMetaclass.__new__ registry kwarg handling."""
+
+from sqlalchemy.orm import registry
+from sqlmodel import SQLModel
+
+
+def test_custom_registry_base_stores_registry_in_model_config() -> None:
+    """model_config['registry'] must hold the registry object passed as kwarg."""
+    custom_registry = registry()
+
+    class MyBase(SQLModel, registry=custom_registry):
+        pass
+
+    stored = MyBase.model_config.get("registry")
+    assert stored is custom_registry, (
+        f"model_config['registry'] should be the custom registry, got {stored!r}"
+    )
+
+
+def test_custom_registry_base_sets_sa_registry() -> None:
+    """_sa_registry must reference the registry object passed as kwarg."""
+    custom_registry = registry()
+
+    class MyBase2(SQLModel, registry=custom_registry):
+        pass
+
+    sa_registry = getattr(MyBase2, "_sa_registry", None)
+    assert sa_registry is custom_registry, (
+        f"_sa_registry should be the custom registry, got {sa_registry!r}"
+    )