diff --git a/translator/app.py b/translator/app.py
index 3fdf576..e2bb97a 100644
--- a/translator/app.py
+++ b/translator/app.py
@@ -5,7 +5,6 @@
 
 import streamlit as st
 from langchain.prompts import ChatPromptTemplate
-from langchain_core.runnables import Runnable
 from langchain_ollama import ChatOllama
 from langchain_openai import ChatOpenAI
 from utils import parse_config
@@ -16,10 +15,13 @@ class TranslatorApp:
 
     def __init__(self, config_path: str = 'config.yaml'):
         self._config = parse_config(config_path)
-        self._chain = self._prepare_chain()
+        self._chain = None
 
-    def _prepare_chain(self) -> Runnable:
+    def _prepare_chain(self) -> None:
         """Prepare the chain for translation"""
+        if self._chain is not None:
+            return
+
         system_template = (
             '你是專業的翻譯人員，請判斷接下來句子的語言是否為{source_lang}，若是的話則請將該句翻譯成{target_lang}，'
             '並且符合{description}（僅回傳翻譯結果即可），若非的話則請回傳一模一樣的句子。'
@@ -50,11 +52,12 @@ class TranslatorApp:
             ('system', system_template),
             ('human', user_template)
         ])
-        return prompt | llm
+        self._chain = prompt | llm
 
     def run(self) -> None:
         """ Run the Streamlit app """
 
+        # Interface
         st.set_page_config(
             page_title=self._config['app']['page_title'],
             page_icon=self._config['app']['page_favicon_path'],
@@ -76,20 +79,21 @@ class TranslatorApp:
         translate_button = st.button('翻譯')
         output_container = st.empty()
 
-
+        # Prepare chain
+        self._prepare_chain()
+        
+        # Action
         if input_text or translate_button:
             if not input_text.strip():
                 st.warning("請輸入要翻譯的文字")
             else:
                 with st.spinner('翻譯中...'):
-
                     result = self._chain.stream({
                         'input_text': input_text,
                         'source_lang': self._config['app']['lang_directions'][direction]['source_lang'],
                         'target_lang': self._config['app']['lang_directions'][direction]['target_lang'],
                         'description': self._config['app']['lang_directions'][direction]['description']
                     })
-
                 output_container.write_stream(
                     stream=result
                 )