diff --git a/ee/app/models/ai/catalog/item.rb b/ee/app/models/ai/catalog/item.rb
index a380da17b0590fd106032d88089ddca7d0a99b1a..415352fcec6310c105e8dd60bc5d2c2e35a8c777 100644
--- a/ee/app/models/ai/catalog/item.rb
+++ b/ee/app/models/ai/catalog/item.rb
@@ -49,6 +49,8 @@ class Item < ApplicationRecord
       scope :with_ids, ->(ids) { where(id: ids) }
       scope :with_item_type, ->(item_type) { where(item_type: item_type) }
 
+      scope :without_consumers, -> { left_joins(:consumers).where(ai_catalog_item_consumers: { id: nil }) }
+
       scope :order_by_id_desc, -> do
         return reorder(id: :desc) unless ::Gitlab::Saas.feature_available?(:gitlab_duo_saas_only)
 
diff --git a/ee/app/services/ee/projects/destroy_service.rb b/ee/app/services/ee/projects/destroy_service.rb
index 5978de80d45cc18146af800b3cdf2854cebfeb6c..4de24d113194281ea7f40e17e034618ce5b89955 100644
--- a/ee/app/services/ee/projects/destroy_service.rb
+++ b/ee/app/services/ee/projects/destroy_service.rb
@@ -40,6 +40,7 @@ def geo_replicate
       override :destroy_project_related_records
       def destroy_project_related_records(project)
         destroy_compliance_requirement_statuses!
+        destroy_ai_catalog_items!
 
         with_scheduling_epic_cache_update do
           super && log_destroy_events
@@ -125,6 +126,21 @@ def destroy_compliance_requirement_statuses!
         ::ComplianceManagement::ComplianceFramework::ProjectRequirementComplianceStatus
           .delete_all_project_statuses(project.id)
       end
+
+      def destroy_ai_catalog_items!
+        ::Ai::Catalog::ItemConsumer.for_projects(project).delete_all
+
+        project_owned_items = ::Ai::Catalog::Item.for_project(project)
+
+        # Hard delete items that have no remaining consumers
+        project_owned_items.without_consumers.delete_all
+
+        # Soft delete all items owned by the project
+        project_owned_items.update_all(
+          project_id: nil,
+          deleted_at: Time.zone.now
+        )
+      end
     end
   end
 end
diff --git a/ee/spec/models/ai/catalog/item_spec.rb b/ee/spec/models/ai/catalog/item_spec.rb
index 14b90300ccc1e82834a38e6294c07bf85ae0f298..7b85ee0aff335b34cd9880bae42600e015d86429 100644
--- a/ee/spec/models/ai/catalog/item_spec.rb
+++ b/ee/spec/models/ai/catalog/item_spec.rb
@@ -383,6 +383,37 @@
         expect(result).not_to include(item_without_reference)
       end
     end
+
+    describe '.without_consumers' do
+      let_it_be(:project) { create(:project) }
+      let_it_be(:item_with_consumers) { create(:ai_catalog_item, :public, project: project) }
+      let_it_be(:item_without_consumers) { create(:ai_catalog_item, :public, project: project) }
+      let_it_be(:consumer) { create(:ai_catalog_item_consumer, project: project, item: item_with_consumers) }
+
+      it 'returns only items without any consumers' do
+        expect(described_class.without_consumers).to contain_exactly(item_without_consumers)
+      end
+
+      context 'when an item has multiple consumers' do
+        let_it_be(:another_consumer) do
+          create(:ai_catalog_item_consumer, project: create(:project), item: item_with_consumers)
+        end
+
+        it 'still excludes the item' do
+          expect(described_class.without_consumers).to contain_exactly(item_without_consumers)
+        end
+      end
+
+      context 'when all items have consumers' do
+        before do
+          create(:ai_catalog_item_consumer, project: project, item: item_without_consumers)
+        end
+
+        it 'returns an empty collection' do
+          expect(described_class.without_consumers).to be_empty
+        end
+      end
+    end
   end
 
   describe 'callbacks' do
diff --git a/ee/spec/services/projects/destroy_service_spec.rb b/ee/spec/services/projects/destroy_service_spec.rb
index 787025c1fce8c17dafd8f0cc9481f99878362694..b2dd2c9584d7c1b5196feaccc448178f524426b1 100644
--- a/ee/spec/services/projects/destroy_service_spec.rb
+++ b/ee/spec/services/projects/destroy_service_spec.rb
@@ -540,4 +540,73 @@
       project_destroy_service.execute
     end
   end
+
+  context 'when project has AI catalog items with consumers' do
+    let_it_be(:project2) { create(:project) }
+
+    let!(:ai_catalog_item) { create(:ai_catalog_item, :public, project: project) }
+    let!(:project_consumer) { create(:ai_catalog_item_consumer, item: ai_catalog_item, project: project) }
+    let!(:another_project_consumer) { create(:ai_catalog_item_consumer, item: ai_catalog_item, project: project2) }
+
+    context 'when the item has consumers from other projects' do
+      it 'deletes project consumers, soft deletes catalog item and unsets the project association' do
+        expect { project_destroy_service.execute }
+          .to change { Ai::Catalog::ItemConsumer.where(id: project_consumer.id).count }.by(-1)
+          .and change { ai_catalog_item.reload.project_id }.from(project.id).to(nil)
+          .and change { ai_catalog_item.reload.deleted_at }.from(nil)
+
+        expect(another_project_consumer.reload).to be_present
+
+        expect(Project.unscoped.all).not_to include(project)
+      end
+    end
+
+    context 'when the item only has consumers from the same project' do
+      let(:another_project_consumer) { nil }
+
+      it 'deletes the item and its consumers via cascade' do
+        expect { project_destroy_service.execute }
+          .to change { Ai::Catalog::Item.where(id: ai_catalog_item.id).count }.by(-1)
+          .and change { Ai::Catalog::ItemConsumer.where(id: project_consumer.id).count }.by(-1)
+
+        expect(Project.unscoped.all).not_to include(project)
+      end
+    end
+
+    context 'when the item has no consumers' do
+      let(:project_consumer) { nil }
+      let(:another_project_consumer) { nil }
+
+      it 'deletes the item along with the project' do
+        expect { project_destroy_service.execute }
+          .to change { Ai::Catalog::Item.where(id: ai_catalog_item.id).count }.by(-1)
+
+        expect(Project.unscoped.all).not_to include(project)
+      end
+    end
+
+    it 'does not cause N+1 queries when checking for external consumers' do
+      # Baseline: project with 1 catalog item
+      baseline_project = create(:project, namespace: user.namespace)
+      baseline_item = create(:ai_catalog_item, :public, project: baseline_project)
+      create(:ai_catalog_item_consumer, item: baseline_item, project: baseline_project)
+      create(:ai_catalog_item_consumer, item: baseline_item, project: project2)
+
+      baseline = ActiveRecord::QueryRecorder.new do
+        described_class.new(baseline_project, user, {}).execute
+      end
+
+      # Test: project with 3 catalog items (should not cause N+1)
+      test_project = create(:project, namespace: user.namespace)
+      3.times do
+        item = create(:ai_catalog_item, :public, project: test_project)
+        create(:ai_catalog_item_consumer, item: item, project: test_project)
+        create(:ai_catalog_item_consumer, item: item, project: project2)
+      end
+
+      expect do
+        described_class.new(test_project, user, {}).execute
+      end.not_to exceed_query_limit(baseline)
+    end
+  end
 end