Update app.py

app.py

@@ -266,7 +266,7 @@ if st.session_state.vector_store is not None:
     )
     # configure response synthesizer
     response_synthesizer = get_response_synthesizer(
-        response_mode="compact", service_context=service_context
+        response_mode="tree_summarize", service_context=service_context
     )
 
     # assemble query engine