diff --git a/pageindex/utils.py b/pageindex/utils.py
index dc7acd888..7d661183f 100644
--- a/pageindex/utils.py
+++ b/pageindex/utils.py
@@ -2,6 +2,7 @@
 import openai
 import logging
 import os
+import re
 from datetime import datetime
 import time
 import json
@@ -16,9 +17,35 @@
 import yaml
 from pathlib import Path
 from types import SimpleNamespace as config
+from typing import Dict, Optional
 
 CHATGPT_API_KEY = os.getenv("CHATGPT_API_KEY")
 
+# Singleton clients for reuse across calls, cached per API key.
+_sync_clients: Dict[str, openai.OpenAI] = {}
+_async_clients: Dict[str, openai.AsyncOpenAI] = {}
+
+
+def _normalize_api_key(api_key: Optional[str]) -> str:
+    return api_key or CHATGPT_API_KEY or ""
+
+
+def _get_sync_client(api_key: Optional[str] = None) -> openai.OpenAI:
+    """Get or create the shared sync OpenAI client."""
+    key = _normalize_api_key(api_key)
+    if key not in _sync_clients:
+        _sync_clients[key] = openai.OpenAI(api_key=api_key or CHATGPT_API_KEY)
+    return _sync_clients[key]
+
+
+def _get_async_client(api_key: Optional[str] = None) -> openai.AsyncOpenAI:
+    """Get or create the shared async OpenAI client."""
+    key = _normalize_api_key(api_key)
+    if key not in _async_clients:
+        _async_clients[key] = openai.AsyncOpenAI(api_key=api_key or CHATGPT_API_KEY)
+    return _async_clients[key]
+
+
 def count_tokens(text, model=None):
     if not text:
         return 0
@@ -28,12 +55,11 @@ def count_tokens(text, model=None):
 
 def ChatGPT_API_with_finish_reason(model, prompt, api_key=CHATGPT_API_KEY, chat_history=None):
     max_retries = 10
-    client = openai.OpenAI(api_key=api_key)
+    client = _get_sync_client(api_key)
     for i in range(max_retries):
         try:
             if chat_history:
-                messages = chat_history
-                messages.append({"role": "user", "content": prompt})
+                messages = chat_history + [{"role": "user", "content": prompt}]
             else:
                 messages = [{"role": "user", "content": prompt}]
             
@@ -54,18 +80,17 @@ def ChatGPT_API_with_finish_reason(model, prompt, api_key=CHATGPT_API_KEY, chat_
                 time.sleep(1)  # Wait for 1秒 before retrying
             else:
                 logging.error('Max retries reached for prompt: ' + prompt)
-                return "Error"
+                return "", "error"
 
 
 
 def ChatGPT_API(model, prompt, api_key=CHATGPT_API_KEY, chat_history=None):
     max_retries = 10
-    client = openai.OpenAI(api_key=api_key)
+    client = _get_sync_client(api_key)
     for i in range(max_retries):
         try:
             if chat_history:
-                messages = chat_history
-                messages.append({"role": "user", "content": prompt})
+                messages = chat_history + [{"role": "user", "content": prompt}]
             else:
                 messages = [{"role": "user", "content": prompt}]
             
@@ -89,15 +114,15 @@ def ChatGPT_API(model, prompt, api_key=CHATGPT_API_KEY, chat_history=None):
 async def ChatGPT_API_async(model, prompt, api_key=CHATGPT_API_KEY):
     max_retries = 10
     messages = [{"role": "user", "content": prompt}]
+    client = _get_async_client(api_key)
     for i in range(max_retries):
         try:
-            async with openai.AsyncOpenAI(api_key=api_key) as client:
-                response = await client.chat.completions.create(
-                    model=model,
-                    messages=messages,
-                    temperature=0,
-                )
-                return response.choices[0].message.content
+            response = await client.chat.completions.create(
+                model=model,
+                messages=messages,
+                temperature=0,
+            )
+            return response.choices[0].message.content
         except Exception as e:
             print('************* Retrying *************')
             logging.error(f"Error: {e}")
@@ -709,4 +734,4 @@ def load(self, user_opt=None) -> config:
 
         self._validate_keys(user_dict)
         merged = {**self._default_dict, **user_dict}
-        return config(**merged)
\ No newline at end of file
+        return config(**merged)