diff --git a/apps/services/conversation.py b/apps/services/conversation.py
index f2b2551adc7aef8160c03e4839230eb68930aa7c..9068badfcd273712d5d98f2ef1397b65187fed05 100644
--- a/apps/services/conversation.py
+++ b/apps/services/conversation.py
@@ -12,6 +12,7 @@ from apps.schemas.collection import Conversation, KnowledgeBaseItem, LLMItem
 from apps.services.knowledge import KnowledgeBaseManager
 from apps.services.llm import LLMManager
 from apps.services.task import TaskManager
+from apps.services.user import UserManager
 from apps.templates.generate_llm_operator_config import llm_provider_dict
 from apps.llm.adapters import get_provider_from_endpoint
 from apps.llm.enum import DefaultModelId
@@ -48,7 +49,12 @@ class ConversationManager:
         """通过用户ID新建对话"""
         if not llm_id:
             # 获取系统默认模型的UUID
-            llm = await LLMManager.get_llm_by_id(DefaultModelId.DEFAULT_CHAT_MODEL_ID.value)
+            user_info = await UserManager.get_userinfo_by_user_sub(user_sub)
+            llm = None
+            if user_info.preferences.reasoning_model_preference:
+                llm = await LLMManager.get_llm_by_id(user_info.preferences.reasoning_model_preference.llm_id)
+            if llm is None:
+                llm = await LLMManager.get_llm_by_id(DefaultModelId.DEFAULT_CHAT_MODEL_ID.value)
             llm_item = LLMItem(
                 llm_id=llm.id,
                 model_name=llm.model_name,
diff --git a/apps/services/llm.py b/apps/services/llm.py
index babbb4e7b8ceb8ef1b7fb79d284158fd21bf4e20..2a1fbcba3ada38e1a57703940c64483c1d78f5f6 100644
--- a/apps/services/llm.py
+++ b/apps/services/llm.py
@@ -155,7 +155,7 @@ class LLMManager:
         if not result:
             err = f"[LLMManager] LLM {llm_id} 不存在"
             logger.error(err)
-            raise ValueError(err)
+            return None
 
         return LLM.model_validate(result)