updated app

app.py

@@ -9,9 +9,10 @@ from sentence_transformers import CrossEncoder
 
 QWEN_MODEL="qwen/qwen3-235b-a22b:free"
 DEEPSEEK_MODEL="deepseek/deepseek-chat-v3.1:free"
+GPT_OSS_MODEL="openai/gpt-oss-20b:free"
 api_key = os.getenv("OPENROUTER_API_KEY")
 deepseek_key = os.getenv("DEEPSEEK_API_KEY")
-client = OpenAI(base_url="https://openrouter.ai/api/v1", api_key=deepseek_key)
+client = OpenAI(base_url="https://openrouter.ai/api/v1", api_key=api_key)
 
 # open ai method
 #api_key = os.getenv("OPENAI_API_KEY")
@@ -24,7 +25,7 @@ collection = load_collection()
 encoder = load_encoder()
 reranker = CrossEncoder("BAAI/bge-reranker-large")
 
-def reformulate_query(user_question, model_name=DEEPSEEK_MODEL):
+def reformulate_query(user_question, model_name=GPT_OSS_MODEL):
     prompt = f"""你是一个BangDream知识检索助手。请把用户的问题扩写或转写为适合知识库语义检索的检索语句，涵盖所有可能的提问方式或同义关键词。
     用户问题：{user_question}
     """
@@ -101,7 +102,7 @@ def respond(
 
     response = ""
     stream = client.chat.completions.create(
-        model=DEEPSEEK_MODEL,
+        model=GPT_OSS_MODEL,
         messages=messages,
         temperature=temperature,
         max_tokens=max_tokens,