fixed app.py

app.py

@@ -39,11 +39,9 @@ def respond(
     history: [{"role": "user", "content": ...}, {"role": "assistant", "content": ...}, ...]
     system_message: 自定义 System Prompt
     """
-    chat_history = [
-        {"role": "system", "content": system_message.strip() or "你是BangDream知识问答助手, 只能基于提供资料作答。"}
-    ]
-    chat_history.extend(history)
-    chat_history.append({"role": "user", "content": message})
+    default_system_message = "你是BangDream知识问答助手, 只能基于提供资料作答。"
+    system_msg = (system_message or default_system_message).strip()
+    chat_history = [{"role": "system", "content": system_msg}]
 
     query_vec = encode_query(encoder, message)
     results = retrieve_docs(collection, query_vec, top_k=30)