diff --git a/api/apps/services/models_api_service.py b/api/apps/services/models_api_service.py
index b6fcf1492c..1daf0b28c7 100644
--- a/api/apps/services/models_api_service.py
+++ b/api/apps/services/models_api_service.py
@@ -373,6 +373,6 @@ def list_tenant_added_models(tenant_id: str, model_type_filter: str = None):
                     }
                 )
 
-    added_models.sort(key=lambda x: (factory_rank_mapping.get(x["provider_name"]), x["provider_name"], x["instance_name"], -x["rank"], x["name"]))
+    added_models.sort(key=lambda x: (factory_rank_mapping.get(x["provider_name"], -500), x["provider_name"], x["instance_name"], -x["rank"], x["name"]))
 
     return True, added_models
diff --git a/rag/llm/chat_model.py b/rag/llm/chat_model.py
index 0ab017bd2f..c19f89a3ec 100644
--- a/rag/llm/chat_model.py
+++ b/rag/llm/chat_model.py
@@ -396,6 +396,7 @@ class Base(ABC):
         hist.append(
             {
                 "role": "assistant",
+                "content": None,
                 "tool_calls": [
                     {
                         "index": getattr(tool_call, "index", None),
@@ -425,6 +426,7 @@ class Base(ABC):
         hist.append(
             {
                 "role": "assistant",
+                "content": None,
                 "tool_calls": [
                     {
                         "index": getattr(tc, "index", None),
@@ -1884,6 +1886,7 @@ class LiteLLMBase(ABC):
     def _append_history(self, hist, tool_call, tool_res, reasoning_content=None):
         assistant_msg = {
             "role": "assistant",
+            "content": None,
             "tool_calls": [
                 {
                     "index": getattr(tool_call, "index", None),
@@ -1914,6 +1917,7 @@ class LiteLLMBase(ABC):
         """
         assistant_msg = {
             "role": "assistant",
+            "content": None,
             "tool_calls": [
                 {
                     "index": getattr(tc, "index", None),