diff --git a/api/app/core/workflow/nodes/base_node.py b/api/app/core/workflow/nodes/base_node.py
index dacbef85..b84011d3 100644
--- a/api/app/core/workflow/nodes/base_node.py
+++ b/api/app/core/workflow/nodes/base_node.py
@@ -1,7 +1,7 @@
 import asyncio
 import logging
-import uuid
 from abc import ABC, abstractmethod
+from datetime import datetime
 from functools import cached_property
 from typing import Any, AsyncGenerator
 
@@ -13,6 +13,7 @@ from app.core.workflow.engine.variable_pool import VariablePool
 from app.core.workflow.nodes.enums import BRANCH_NODES
 from app.core.workflow.variable.base_variable import VariableType, FileObject
 from app.db import get_db_read
+from app.models import ModelConfig, ModelApiKey, LoadBalanceStrategy
 from app.schemas import FileInput
 from app.services.multimodal_service import MultimodalService
 
@@ -629,7 +630,7 @@ class BaseNode(ABC):
             )
         if isinstance(content, str):
             if enable_file:
-                return [{"text": content}]
+                return [{"type": "text", "text": content}]
             return content
 
         elif isinstance(content, FileObject):
@@ -667,3 +668,12 @@ class BaseNode(ABC):
         elif isinstance(content, str):
             return content
         return result
+
+    def model_balance(self, model_config: ModelConfig) -> ModelApiKey:
+        api_keys = [key for key in model_config.api_keys if key.is_active]
+        if not api_keys:
+            raise ValueError("No active API keys available for model")
+        if model_config.load_balance_strategy == LoadBalanceStrategy.ROUND_ROBIN:
+            if model_config.load_balance_strategy == LoadBalanceStrategy.ROUND_ROBIN:
+                return min(api_keys, key=lambda x: (int(x.usage_count or "0"), x.last_used_at or datetime.min))
+        return api_keys[0]
diff --git a/api/app/core/workflow/nodes/llm/node.py b/api/app/core/workflow/nodes/llm/node.py
index 4b63bc4e..92a0dff7 100644
--- a/api/app/core/workflow/nodes/llm/node.py
+++ b/api/app/core/workflow/nodes/llm/node.py
@@ -112,11 +112,12 @@ class LLMNode(BaseNode):
                 raise BusinessException("模型配置缺少 API Key", BizCode.INVALID_PARAMETER)
 
             # 在 Session 关闭前提取所有需要的数据
-            api_config = config.api_keys[0]
+            api_config = self.model_balance(config)
             model_name = api_config.model_name
             provider = api_config.provider
             api_key = api_config.api_key
             api_base = api_config.api_base
+            is_omni = api_config.is_omni
             model_type = config.type
 
         # 4. 创建 LLM 实例（使用已提取的数据）
@@ -129,7 +130,8 @@ class LLMNode(BaseNode):
                 provider=provider,
                 api_key=api_key,
                 base_url=api_base,
-                extra_params=extra_params
+                extra_params=extra_params,
+                is_omni=is_omni
             ),
             type=ModelType(model_type)
         )
diff --git a/api/app/core/workflow/nodes/parameter_extractor/node.py b/api/app/core/workflow/nodes/parameter_extractor/node.py
index 4811c118..700ed85f 100644
--- a/api/app/core/workflow/nodes/parameter_extractor/node.py
+++ b/api/app/core/workflow/nodes/parameter_extractor/node.py
@@ -95,11 +95,12 @@ class ParameterExtractorNode(BaseNode):
             if not config.api_keys or len(config.api_keys) == 0:
                 raise BusinessException("Model configuration is missing API Key", BizCode.INVALID_PARAMETER)
 
-            api_config = config.api_keys[0]
+            api_config = self.model_balance(config)
             model_name = api_config.model_name
             provider = api_config.provider
             api_key = api_config.api_key
             api_base = api_config.api_base
+            is_omni = api_config.is_omni
             model_type = config.type
 
         llm = RedBearLLM(
@@ -108,6 +109,7 @@ class ParameterExtractorNode(BaseNode):
                 provider=provider,
                 api_key=api_key,
                 base_url=api_base,
+                is_omni=is_omni
             ),
             type=ModelType(model_type)
         )
diff --git a/api/app/core/workflow/nodes/question_classifier/node.py b/api/app/core/workflow/nodes/question_classifier/node.py
index e2fd97ae..5cebd886 100644
--- a/api/app/core/workflow/nodes/question_classifier/node.py
+++ b/api/app/core/workflow/nodes/question_classifier/node.py
@@ -56,11 +56,12 @@ class QuestionClassifierNode(BaseNode):
             if not config.api_keys or len(config.api_keys) == 0:
                 raise BusinessException("模型配置缺少 API Key", BizCode.INVALID_PARAMETER)
 
-            api_config = config.api_keys[0]
+            api_config = self.model_balance(config)
             model_name = api_config.model_name
             provider = api_config.provider
             api_key = api_config.api_key
             base_url = api_config.api_base
+            is_omni = api_config.is_omni
             model_type = config.type
 
         return RedBearLLM(
@@ -69,6 +70,7 @@ class QuestionClassifierNode(BaseNode):
                 provider=provider,
                 api_key=api_key,
                 base_url=base_url,
+                is_omni=is_omni
             ),
             type=ModelType(model_type)
         )
diff --git a/api/app/schemas/conversation_schema.py b/api/app/schemas/conversation_schema.py
index 0fcbc718..13766ef6 100644
--- a/api/app/schemas/conversation_schema.py
+++ b/api/app/schemas/conversation_schema.py
@@ -86,6 +86,7 @@ class ChatResponse(BaseModel):
     """聊天响应（非流式）"""
     conversation_id: uuid.UUID
     message: str
+    message_id: str
     usage: Optional[Dict[str, Any]] = None
     elapsed_time: Optional[float] = None