Update app.py

app.py

@@ -23,10 +23,14 @@ logger = logging.getLogger(__name__)
 
 app = FastAPI(title="Talmud Language Classifier Training")
 
+VERCEL_PRODUCTION_URL = os.getenv('VERCEL_PRODUCTION_URL', 'https://talmud-annotation-platform.vercel.app')
+VERCEL_PREVIEW_URL_REGEX = r'https://talmud-annotation-platform-[a-zA-Z0-9]{9}-shmans-projects\.vercel\.app'
+
 # Enable CORS for Vercel callbacks
 app.add_middleware(
     CORSMiddleware,
-    allow_origins=["*"],  # In production, restrict to your Vercel domain
+    allow_origins=[VERCEL_PRODUCTION_URL], 
+    allow_origin_regex=VERCEL_PREVIEW_URL_REGEX,  
     allow_credentials=True,
     allow_methods=["*"],
     allow_headers=["*"],