Update app.py

app.py

@@ -11,7 +11,7 @@ from langchain_core.messages import HumanMessage, SystemMessage
 # --- Configuration ---
 NEBIUS_API_KEY = os.getenv("NEBIUS_API_KEY") 
 NEBIUS_BASE_URL = "https://api.studio.nebius.ai/v1/"
-MODEL_NAME = "Qwen/Qwen3-30B-A3B-Thinking-2507"
+MODEL_NAME = "openai/gpt-oss-120b"
 
 # --- System Prompt ---
 SYSTEM_PROMPT = """You are a 'Vibe Coding' Python Tutor.