diff --git a/backend/packages/harness/deerflow/agents/middlewares/billing_middleware.py b/backend/packages/harness/deerflow/agents/middlewares/billing_middleware.py
index 65cef099..bfbebc14 100644
--- a/backend/packages/harness/deerflow/agents/middlewares/billing_middleware.py
+++ b/backend/packages/harness/deerflow/agents/middlewares/billing_middleware.py
@@ -438,8 +438,8 @@ def _resolve_model_name(model_key: str | None) -> str | None:
     if not model_key:
         return None
     model_cfg = get_app_config().get_model_config(model_key)
-    if model_cfg and model_cfg.display_name:
-        return model_cfg.display_name
+    if model_cfg and model_cfg.model:
+        return model_cfg.model
     return model_key