Update agent.py

agent.py

@@ -159,8 +159,8 @@ def build_graph(provider: str = "openai"):
         # Google Gemini
         llm = ChatGoogleGenerativeAI(model="gemini-2.0-flash", temperature=0)
     elif provider == "openai":
-        # OpenAI (e.g., GPT-4 or GPT-3.5)
-        llm = ChatOpenAI(model="gpt-4", temperature=0)
+        # OpenAI (e.g., GPT-4 or GPT-3.5 free)
+        llm = ChatOpenAI(model="gpt-3.5-turbo", temperature=0)
     elif provider == "huggingface":
         # Hugging Face endpoint
         llm = ChatHuggingFace(