diff --git a/rdagent/oai/backend/litellm.py b/rdagent/oai/backend/litellm.py
index 252ab0ac..250aa88a 100644
--- a/rdagent/oai/backend/litellm.py
+++ b/rdagent/oai/backend/litellm.py
@@ -88,6 +88,7 @@ class LiteLLMAPIBackend(APIBackend):
             stream=LITELLM_SETTINGS.chat_stream,
             temperature=LITELLM_SETTINGS.chat_temperature,
             max_tokens=LITELLM_SETTINGS.chat_max_tokens,
+            reasoning_effort=LITELLM_SETTINGS.reasoning_effort,
             **kwargs,
         )
         logger.info(
diff --git a/rdagent/oai/llm_conf.py b/rdagent/oai/llm_conf.py
index fcd6e350..474e8025 100644
--- a/rdagent/oai/llm_conf.py
+++ b/rdagent/oai/llm_conf.py
@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 from pathlib import Path
+from typing import Literal
 
 from pydantic import Field
 
@@ -14,6 +15,8 @@ class LLMSettings(ExtendedBaseSettings):
     chat_model: str = "gpt-4-turbo"
     embedding_model: str = "text-embedding-3-small"
 
+    reasoning_effort: Literal["low", "medium", "high"] | None = None
+
     # TODO: most of the settings are only used on deprec.DeprecBackend.
     # So they should move the settings to that folder.