fix(llm-validation): accept stepfun multimodal models and return 422 on capability mismatch

backend/src/api/routes/assistant.py

@@ -1239,7 +1239,7 @@ async def _dispatch_intent(
             )
         provider = LLMProviderService(db).get_provider(provider_id)
         provider_model = provider.default_model if provider else ""
-        if not is_multimodal_model(provider_model):
+        if not is_multimodal_model(provider_model, provider.provider_type if provider else None):
             raise HTTPException(
                 status_code=422,
                 detail=(

backend/src/api/routes/tasks.py

@@ -83,9 +83,13 @@ async def create_task(
                         db_provider = llm_service.get_provider(provider_id)
                         if not db_provider:
                             raise ValueError(f"LLM Provider {provider_id} not found")
-                        if request.plugin_id == "llm_dashboard_validation" and not is_multimodal_model(db_provider.default_model):
-                            raise ValueError(
-                                "Selected provider model is not multimodal for dashboard validation"
+                        if request.plugin_id == "llm_dashboard_validation" and not is_multimodal_model(
+                            db_provider.default_model,
+                            db_provider.provider_type,
+                        ):
+                            raise HTTPException(
+                                status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
+                                detail="Selected provider model is not multimodal for dashboard validation",
                             )
                 finally:
                     db.close()