diff --git a/rag/llm/chat_model.py b/rag/llm/chat_model.py
index 9fbc88348..726aecd8b 100644
--- a/rag/llm/chat_model.py
+++ b/rag/llm/chat_model.py
@@ -33,9 +33,9 @@ from openai.lib.azure import AzureOpenAI
 from strenum import StrEnum
 from zhipuai import ZhipuAI
 
+from common.token_utils import num_tokens_from_string, total_token_count_from_response
 from rag.llm import FACTORY_DEFAULT_BASE_URL, LITELLM_PROVIDER_PREFIX, SupportedLiteLLMProvider
 from rag.nlp import is_chinese, is_english
-from common.token_utils import num_tokens_from_string, total_token_count_from_response
 
 
 # Error message constants
@@ -66,7 +66,7 @@ LENGTH_NOTIFICATION_EN = "...\nThe answer is truncated by your chosen LLM due to
 
 class Base(ABC):
     def __init__(self, key, model_name, base_url, **kwargs):
-        timeout = int(os.environ.get("LM_TIMEOUT_SECONDS", 600))
+        timeout = int(os.environ.get("LLM_TIMEOUT_SECONDS", 600))
         self.client = OpenAI(api_key=key, base_url=base_url, timeout=timeout)
         self.model_name = model_name
         # Configure retry parameters
@@ -127,7 +127,7 @@ class Base(ABC):
             "tool_choice",
             "logprobs",
             "top_logprobs",
-            "extra_headers"
+            "extra_headers",
         }
 
         gen_conf = {k: v for k, v in gen_conf.items() if k in allowed_conf}
@@ -1213,7 +1213,7 @@ class GoogleChat(Base):
 
         # Build GenerateContentConfig
         try:
-            from google.genai.types import GenerateContentConfig, ThinkingConfig, Content, Part
+            from google.genai.types import Content, GenerateContentConfig, Part, ThinkingConfig
         except ImportError as e:
             logging.error(f"[GoogleChat] Failed to import google-genai: {e}. Please install: pip install google-genai>=1.41.0")
             raise
@@ -1242,14 +1242,14 @@ class GoogleChat(Base):
             role = "model" if item["role"] == "assistant" else item["role"]
             content = Content(
                 role=role,
-                parts=[Part(text=item["content"])]
+                parts=[Part(text=item["content"])],
             )
             contents.append(content)
 
         response = self.client.models.generate_content(
             model=self.model_name,
             contents=contents,
-            config=config
+            config=config,
         )
 
         ans = response.text
@@ -1299,7 +1299,7 @@ class GoogleChat(Base):
 
             # Build GenerateContentConfig
             try:
-                from google.genai.types import GenerateContentConfig, ThinkingConfig, Content, Part
+                from google.genai.types import Content, GenerateContentConfig, Part, ThinkingConfig
             except ImportError as e:
                 logging.error(f"[GoogleChat] Failed to import google-genai: {e}. Please install: pip install google-genai>=1.41.0")
                 raise
@@ -1326,7 +1326,7 @@ class GoogleChat(Base):
                 role = "model" if item["role"] == "assistant" else item["role"]
                 content = Content(
                     role=role,
-                    parts=[Part(text=item["content"])]
+                    parts=[Part(text=item["content"])],
                 )
                 contents.append(content)
 
@@ -1334,7 +1334,7 @@ class GoogleChat(Base):
                 for chunk in self.client.models.generate_content_stream(
                     model=self.model_name,
                     contents=contents,
-                    config=config
+                    config=config,
                 ):
                     text = chunk.text
                     ans = text
@@ -1406,7 +1406,7 @@ class LiteLLMBase(ABC):
     ]
 
     def __init__(self, key, model_name, base_url=None, **kwargs):
-        self.timeout = int(os.environ.get("LM_TIMEOUT_SECONDS", 600))
+        self.timeout = int(os.environ.get("LLM_TIMEOUT_SECONDS", 600))
         self.provider = kwargs.get("provider", "")
         self.prefix = LITELLM_PROVIDER_PREFIX.get(self.provider, "")
         self.model_name = f"{self.prefix}{model_name}"
@@ -1625,6 +1625,7 @@ class LiteLLMBase(ABC):
 
         if self.provider == SupportedLiteLLMProvider.OpenRouter:
             if self.provider_order:
+
                 def _to_order_list(x):
                     if x is None:
                         return []
@@ -1633,6 +1634,7 @@ class LiteLLMBase(ABC):
                     if isinstance(x, (list, tuple)):
                         return [str(s).strip() for s in x if str(s).strip()]
                     return []
+
                 extra_body = {}
                 provider_cfg = {}
                 provider_order = _to_order_list(self.provider_order)