fix: Use gemini-2.5-flash as default (confirmed working)

app.py

@@ -331,16 +331,14 @@ with st.sidebar:
         gemini_model = st.selectbox(
             "Gemini Model",
             [
-                "gemini-1.5-flash",
-                "gemini-1.5-pro",
+                "gemini-2.5-flash",  # This one was working!
                 "gemini-2.0-flash",
-                "gemini-2.5-flash",  # May require newer API
+                "gemini-1.5-pro",
             ],
-            index=0,  # Default to 1.5 Flash (stable, free tier)
-            help="""**Gemini 1.5 Flash** (Recommended): Stable, fast, FREE tier (15 RPM)
-**Gemini 1.5 Pro**: Better reasoning, 2M context, FREE tier
-**Gemini 2.0 Flash**: Newer model, may have lower limits
-**Gemini 2.5 Flash**: Latest, may require paid plan"""
+            index=0,  # Default to 2.5 Flash (confirmed working)
+            help="""**Gemini 2.5 Flash** (Recommended): Latest, confirmed working
+**Gemini 2.0 Flash**: Newer model
+**Gemini 1.5 Pro**: More stable for complex tasks"""
         )
         st.caption(f"✨ Using {gemini_model}")
     

code_chatbot/rag.py

@@ -118,10 +118,11 @@ class ChatEngine:
                 if not os.getenv("GOOGLE_API_KEY"):
                     raise ValueError("Google API Key is required for Gemini")
             
-            # Use models/ prefix for Gemini models
-            model_name = self.model_name or "gemini-1.5-flash"
-            if not model_name.startswith("models/"):
-                model_name = f"models/{model_name}"
+            # Use model name without prefix - langchain handles it
+            model_name = self.model_name or "gemini-2.5-flash"
+            # Remove models/ prefix if present (langchain adds it)
+            if model_name.startswith("models/"):
+                model_name = model_name.replace("models/", "")
             
             return ChatGoogleGenerativeAI(
                 model=model_name,