diff --git a/netbox_custom_objects/migrations/0002_ensure_fk_constraints.py b/netbox_custom_objects/migrations/0002_ensure_fk_constraints.py
new file mode 100644
index 0000000..a309b98
--- /dev/null
+++ b/netbox_custom_objects/migrations/0002_ensure_fk_constraints.py
@@ -0,0 +1,31 @@
+from django.db import migrations
+
+
+def ensure_existing_fk_constraints(apps, schema_editor):
+    """
+    Go through all existing CustomObjectType models and ensure FK constraints
+    are properly set for any OBJECT type fields.
+    """
+    # Import the actual model class (not the historical version) to access methods
+    from netbox_custom_objects.models import CustomObjectType
+
+    for custom_object_type in CustomObjectType.objects.all():
+        try:
+            model = custom_object_type.get_model()
+            custom_object_type._ensure_all_fk_constraints(model)
+        except Exception as e:
+            print(f"Warning: Could not ensure FK constraints for {custom_object_type}: {e}")
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('netbox_custom_objects', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.RunPython(
+            ensure_existing_fk_constraints,
+            reverse_code=migrations.RunPython.noop
+        ),
+    ]
diff --git a/netbox_custom_objects/models.py b/netbox_custom_objects/models.py
index 3d117f3..af4d3de 100644
--- a/netbox_custom_objects/models.py
+++ b/netbox_custom_objects/models.py
@@ -446,11 +446,12 @@ def get_model(
         """
 
         # Double-check pattern: check cache again after acquiring lock
-        if self.is_model_cached(self.id) and not no_cache:
-            model = self.get_cached_model(self.id)
-            return model
+        with self._global_lock:
+            if self.is_model_cached(self.id) and not no_cache:
+                model = self.get_cached_model(self.id)
+                return model
 
-        # Generate the model inside the lock to prevent race conditions
+        # Generate the model outside the lock to avoid holding it during expensive operations
         model_name = self.get_table_model_name(self.pk)
 
         # TODO: Add other fields with "index" specified
@@ -523,8 +524,9 @@ def wrapped_post_through_setup(self, cls):
 
         self._after_model_generation(attrs, model)
 
-        # Cache the generated model
-        self._model_cache[self.id] = model
+        # Cache the generated model (protected by lock for thread safety)
+        with self._global_lock:
+            self._model_cache[self.id] = model
 
         # Do the clear cache now that we have it in the cache so there
         # is no recursion.
@@ -538,11 +540,76 @@ def wrapped_post_through_setup(self, cls):
 
     def get_model_with_serializer(self):
         from netbox_custom_objects.api.serializers import get_serializer_class
-        model = self.get_model(no_cache=True)
+        model = self.get_model()
         get_serializer_class(model)
         self.register_custom_object_search_index(model)
         return model
 
+    def _ensure_field_fk_constraint(self, model, field_name):
+        """
+        Ensure that a foreign key constraint is properly created at the database level
+        for a specific OBJECT type field with ON DELETE CASCADE. This is necessary because
+        models are created with managed=False, which may not properly create FK constraints
+        with CASCADE behavior.
+
+        :param model: The model containing the field
+        :param field_name: The name of the field to ensure FK constraint for
+        """
+        table_name = self.get_database_table_name()
+
+        # Get the model field
+        try:
+            model_field = model._meta.get_field(field_name)
+        except Exception:
+            return
+
+        if not (hasattr(model_field, 'remote_field') and model_field.remote_field):
+            return
+
+        # Get the referenced table
+        related_model = model_field.remote_field.model
+        related_table = related_model._meta.db_table
+        column_name = model_field.column
+
+        with connection.cursor() as cursor:
+            # Drop existing FK constraint if it exists
+            # Query for existing constraints
+            cursor.execute("""
+                SELECT constraint_name
+                FROM information_schema.table_constraints
+                WHERE table_name = %s
+                AND constraint_type = 'FOREIGN KEY'
+                AND constraint_name LIKE %s
+            """, [table_name, f"%{column_name}%"])
+
+            for row in cursor.fetchall():
+                constraint_name = row[0]
+                cursor.execute(f'ALTER TABLE "{table_name}" DROP CONSTRAINT IF EXISTS "{constraint_name}"')
+
+            # Create new FK constraint with ON DELETE CASCADE
+            constraint_name = f"{table_name}_{column_name}_fk_cascade"
+            cursor.execute(f"""
+                ALTER TABLE "{table_name}"
+                ADD CONSTRAINT "{constraint_name}"
+                FOREIGN KEY ("{column_name}")
+                REFERENCES "{related_table}" ("id")
+                ON DELETE CASCADE
+                DEFERRABLE INITIALLY DEFERRED
+            """)
+
+    def _ensure_all_fk_constraints(self, model):
+        """
+        Ensure that foreign key constraints are properly created at the database level
+        for ALL OBJECT type fields with ON DELETE CASCADE.
+
+        :param model: The model to ensure FK constraints for
+        """
+        # Query all OBJECT type fields for this CustomObjectType
+        object_fields = self.fields.filter(type=CustomFieldTypeChoices.TYPE_OBJECT)
+
+        for field in object_fields:
+            self._ensure_field_fk_constraint(model, field.name)
+
     def create_model(self):
         from netbox_custom_objects.api.serializers import get_serializer_class
         # Get the model and ensure it's registered
@@ -796,6 +863,8 @@ def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
         self._name = self.__dict__.get("name")
         self._original_name = self.name
+        self._original_type = self.type
+        self._original_related_object_type_id = self.related_object_type_id
 
     def __str__(self):
         return self.label or self.name.replace("_", " ").capitalize()
@@ -1482,11 +1551,35 @@ def save(self, *args, **kwargs):
                     # Normal field alteration
                     schema_editor.alter_field(model, old_field, model_field)
 
+        # Ensure FK constraints are properly created for OBJECT fields with CASCADE behavior
+        should_ensure_fk = False
+        if self.type == CustomFieldTypeChoices.TYPE_OBJECT:
+            if self._state.adding:
+                should_ensure_fk = True
+            else:
+                # Existing field - check if type changed to OBJECT or related_object_type changed
+                type_changed_to_object = (
+                    self._original_type != CustomFieldTypeChoices.TYPE_OBJECT
+                    and self.type == CustomFieldTypeChoices.TYPE_OBJECT
+                )
+                related_object_changed = (
+                    self._original_type == CustomFieldTypeChoices.TYPE_OBJECT
+                    and self.related_object_type_id != self._original_related_object_type_id
+                )
+                should_ensure_fk = type_changed_to_object or related_object_changed
+
         # Clear and refresh the model cache for this CustomObjectType when a field is modified
         self.custom_object_type.clear_model_cache(self.custom_object_type.id)
 
         super().save(*args, **kwargs)
 
+        # Ensure FK constraints AFTER the transaction commits to avoid "pending trigger events" errors
+        if should_ensure_fk:
+            def ensure_constraint():
+                self.custom_object_type._ensure_field_fk_constraint(model, self.name)
+
+            transaction.on_commit(ensure_constraint)
+
         # Reregister SearchIndex with new set of searchable fields
         self.custom_object_type.register_custom_object_search_index(model)
 
@@ -1540,3 +1633,34 @@ class CustomObjectObjectType(ObjectType):
 
     class Meta:
         proxy = True
+
+
+# Signal handlers to clear model cache when definitions change
+
+
+@receiver(post_save, sender=CustomObjectType)
+def clear_cache_on_custom_object_type_save(sender, instance, **kwargs):
+    """
+    Clear the model cache when a CustomObjectType is saved.
+    """
+    CustomObjectType.clear_model_cache(instance.id)
+
+
+@receiver(post_save, sender=CustomObjectTypeField)
+def clear_cache_on_field_save(sender, instance, **kwargs):
+    """
+    Clear the model cache when a CustomObjectTypeField is saved.
+    This ensures the parent CustomObjectType's model is regenerated.
+    """
+    if instance.custom_object_type_id:
+        CustomObjectType.clear_model_cache(instance.custom_object_type_id)
+
+
+@receiver(pre_delete, sender=CustomObjectTypeField)
+def clear_cache_on_field_delete(sender, instance, **kwargs):
+    """
+    Clear the model cache when a CustomObjectTypeField is deleted.
+    This is in addition to the manual clear in the delete() method.
+    """
+    if instance.custom_object_type_id:
+        CustomObjectType.clear_model_cache(instance.custom_object_type_id)
diff --git a/netbox_custom_objects/tests/base.py b/netbox_custom_objects/tests/base.py
index 20eac84..82b559e 100644
--- a/netbox_custom_objects/tests/base.py
+++ b/netbox_custom_objects/tests/base.py
@@ -23,6 +23,13 @@ def setUp(self):
         self.client = Client()
         self.client.force_login(self.user)
 
+    def tearDown(self):
+        """Clean up after each test."""
+        # Clear the model cache to ensure test isolation
+        # This prevents cached models with deleted fields from affecting other tests
+        CustomObjectType.clear_model_cache()
+        super().tearDown()
+
     @classmethod
     def create_custom_object_type(cls, **kwargs):
         """Helper method to create a custom object type."""