Update app.py

app.py

@@ -17,7 +17,7 @@ logger = logging.getLogger(__name__)
 # --- Constants ---
 DEFAULT_API_URL   = "https://agents-course-unit4-scoring.hf.space"
 OPENAI_MODEL_ID   = os.getenv("OPENAI_MODEL_ID", "gpt-4.1")
-OPENAI_API_KEY    = os.getenv("open_api_key")
+OPENAI_API_KEY    = os.getenv("OPENAI_API_KEY")
 if not OPENAI_API_KEY:
     raise RuntimeError("Please set OPENAI_API_KEY in your Space secrets.")