diff --git a/ai-hub/app/api/routes/sessions.py b/ai-hub/app/api/routes/sessions.py
index 0803877..e54e16e 100644
--- a/ai-hub/app/api/routes/sessions.py
+++ b/ai-hub/app/api/routes/sessions.py
@@ -42,7 +42,8 @@
                 session_id=session_id,
                 prompt=request.prompt,
                 provider_name=request.provider_name,
-                load_faiss_retriever=request.load_faiss_retriever
+                load_faiss_retriever=request.load_faiss_retriever,
+                user_service=services.user_service
             )
             return schemas.ChatResponse(answer=response_text, provider_used=provider_used, message_id=message_id)
         except Exception as e:
diff --git a/ai-hub/app/core/providers/factory.py b/ai-hub/app/core/providers/factory.py
index e0ded0d..78e6179 100644
--- a/ai-hub/app/core/providers/factory.py
+++ b/ai-hub/app/core/providers/factory.py
@@ -86,10 +86,13 @@
     if not modelName:
         modelName = settings.LLM_PROVIDERS.get(provider_name, {}).get("model")
         if not modelName:
-            if provider_name == "gemini": modelName = settings.GEMINI_MODEL_NAME
-            elif provider_name == "deepseek": modelName = settings.DEEPSEEK_MODEL_NAME
-            else:
-                raise ValueError(f"No model name provided for '{provider_name}'.")
+             # Fallback: check base type if user-selected instance is missing from global settings
+             if provider_name == "gemini": modelName = settings.GEMINI_MODEL_NAME
+             elif provider_name == "deepseek": modelName = settings.DEEPSEEK_MODEL_NAME
+             elif "gemini" in provider_name.lower(): modelName = settings.GEMINI_MODEL_NAME
+             elif "deepseek" in provider_name.lower(): modelName = settings.DEEPSEEK_MODEL_NAME
+             else:
+                 raise ValueError(f"No model name provided for '{provider_name}'.")
         
     # Extract base type (e.g. 'gemini_2' -> 'gemini')
     litellm_providers = [p.value for p in litellm.LlmProviders]
diff --git a/ai-hub/app/core/services/rag.py b/ai-hub/app/core/services/rag.py
index 3eb1987..9af3909 100644
--- a/ai-hub/app/core/services/rag.py
+++ b/ai-hub/app/core/services/rag.py
@@ -24,8 +24,9 @@
         session_id: int,
         prompt: str,
         provider_name: str,
-        load_faiss_retriever: bool = False
-    ) -> Tuple[str, str]:
+        load_faiss_retriever: bool = False,
+        user_service = None
+    ) -> Tuple[str, str, int]:
         """
         Processes a user prompt within a session, saves the chat history, and returns a response.
         """
@@ -49,18 +50,26 @@
         # Keep provider_name in sync with the model actually being used
         if session.provider_name != provider_name:
             session.provider_name = provider_name
-
+        
         db.commit()
 
-        # Fetch user preferences for overrides
-        api_key_override = None
-        model_name_override = ""
+        # Resolve provider: User Prefs > System Settings
         llm_prefs = {}
         user = session.user
         if user and user.preferences:
             llm_prefs = user.preferences.get("llm", {}).get("providers", {}).get(provider_name, {})
-            api_key_override = llm_prefs.get("api_key")
-            model_name_override = llm_prefs.get("model", "")
+
+        # System Settings Fallback
+        if (not llm_prefs or not llm_prefs.get("api_key") or "*" in str(llm_prefs.get("api_key"))) and user_service:
+            system_prefs = user_service.get_system_settings(db)
+            system_provider_prefs = system_prefs.get("llm", {}).get("providers", {}).get(provider_name, {})
+            if system_provider_prefs:
+                merged = system_provider_prefs.copy()
+                if llm_prefs: merged.update({k: v for k, v in llm_prefs.items() if v})
+                llm_prefs = merged
+            
+        api_key_override = llm_prefs.get("api_key")
+        model_name_override = llm_prefs.get("model", "")
             
         # Get the appropriate LLM provider with all extra prefs passed as kwargs
         kwargs = {k: v for k, v in llm_prefs.items() if k not in ["api_key", "model"]}