Prefer complete demo workflow state

backend/app/services/demo_workflow_service.py

@@ -51,12 +51,42 @@ class DemoWorkflowService:
 
     @staticmethod
     def _find_existing_project(db: Session) -> Project | None:
-        return (
+        projects = (
             db.query(Project)
             .filter(Project.name == DemoWorkflowService.PROJECT_NAME)
             .filter(Project.status != "deleted")
+            .order_by(Project.created_at.asc())
+            .all()
+        )
+        for project in projects:
+            if DemoWorkflowService._has_complete_demo_state(db, project.id):
+                return project
+        return projects[0] if projects else None
+
+    @staticmethod
+    def _has_complete_demo_state(db: Session, project_id: UUID) -> bool:
+        area = db.query(Area).filter(Area.project_id == project_id).first()
+        reference = (
+            db.query(Dataset)
+            .filter(Dataset.project_id == project_id)
+            .filter(Dataset.dataset_role == "reference")
+            .filter(Dataset.source_name == "fixture")
             .first()
         )
+        candidate = (
+            db.query(Dataset)
+            .filter(Dataset.project_id == project_id)
+            .filter(Dataset.dataset_role == "source")
+            .filter(Dataset.source_name == "fixture")
+            .first()
+        )
+        quality_check = (
+            db.query(QualityCheck)
+            .filter(QualityCheck.project_id == project_id)
+            .filter(QualityCheck.check_type == "demo_candidate_vs_reference")
+            .first()
+        )
+        return bool(area and reference and candidate and quality_check)
 
     @staticmethod
     def _create_area(db: Session, project_id: UUID) -> Area:

backend/tests/test_sprint15_demo_workflow.py

@@ -66,3 +66,12 @@ def test_demo_workflow_service_supports_container_fixture_mount() -> None:
     assert "project = existing" in service
     assert "if not reference:" in service
     assert "if not candidate:" in service
+
+
+def test_demo_workflow_prefers_complete_existing_demo_project() -> None:
+    service = (DemoWorkflowService._repo_root() / "backend" / "app" / "services" / "demo_workflow_service.py").read_text(encoding="utf-8")
+
+    assert "_has_complete_demo_state" in service
+    assert "order_by(Project.created_at.asc())" in service
+    assert "if DemoWorkflowService._has_complete_demo_state(db, project.id):" in service
+    assert "return projects[0] if projects else None" in service