diff --git a/api/services/app_generate_service.py b/api/services/app_generate_service.py
index 17a112136d..06fc51bddc 100644
--- a/api/services/app_generate_service.py
+++ b/api/services/app_generate_service.py
@@ -133,17 +133,13 @@ class AppGenerateService:
                 from services.workflow.virtual_workflow import VirtualWorkflowSynthesizer
 
                 try:
-                    virtual_workflow = VirtualWorkflowSynthesizer.synthesize(app_model)
+                    workflow = VirtualWorkflowSynthesizer.ensure_workflow(app_model)
                     logger.info(
-                        "[AGENT_V2_UPGRADE] Transparent upgrade for app %s (mode=%s)",
+                        "[AGENT_V2_UPGRADE] Transparent upgrade for app %s (mode=%s), wf=%s",
                         app_model.id,
                         effective_mode,
+                        workflow.id,
                     )
-                    workflow_id_arg = args.get("workflow_id")
-                    if not workflow_id_arg:
-                        workflow = virtual_workflow
-                    else:
-                        workflow = cls._get_workflow(app_model, invoke_from, workflow_id_arg)
 
                     if streaming:
                         with rate_limit_context(rate_limit, request_id):
diff --git a/api/services/workflow/virtual_workflow.py b/api/services/workflow/virtual_workflow.py
index 6167f01349..fdcffaa506 100644
--- a/api/services/workflow/virtual_workflow.py
+++ b/api/services/workflow/virtual_workflow.py
@@ -73,6 +73,36 @@ class VirtualWorkflowSynthesizer:
 
         return workflow
 
+    @staticmethod
+    def ensure_workflow(app: App) -> Any:
+        """Ensure the old app has a workflow, creating one if needed.
+
+        On first call for a legacy app, synthesizes a workflow from its
+        AppModelConfig and persists it as a draft. On subsequent calls,
+        returns the existing draft. This is a one-time lazy upgrade:
+        the app gets a real workflow that can be edited in the workflow editor.
+
+        The app's workflow_id is NOT updated (preserving its legacy state),
+        but the workflow is findable via app_id + version="draft".
+        """
+        from models.workflow import Workflow
+
+        from extensions.ext_database import db
+
+        existing = db.session.query(Workflow).filter_by(
+            app_id=app.id, version="draft"
+        ).first()
+        if existing:
+            return existing
+
+        workflow = VirtualWorkflowSynthesizer.synthesize(app)
+        workflow.version = "draft"
+
+        db.session.add(workflow)
+        db.session.commit()
+        logger.info("Created draft workflow %s for legacy app %s", workflow.id, app.id)
+        return workflow
+
 
 def _extract_model_config(config: AppModelConfig) -> dict[str, Any]:
     if config.model: