fix(middleware): 修复 RuntimeConfigMiddleware 的工具override 导致的其余中间件失效的问题（还需要进一步排查 subagents 的 model 是否有问题）

docs/latest/advanced/agents-config.md

@@ -114,6 +114,16 @@ class ReporterContext(BaseContext):
 
 中间件位于 `src/agents/common/middlewares`，包含上下文感知提示词、模型选择、动态工具加载以及附件注入等实现。如果需要编写新的中间件，请遵循 LangChain 官方文档中对 `AgentMiddleware`、`ModelRequest`、`ModelResponse` 等接口的定义，完成后在该目录的 `__init__.py` 暴露入口，主智能体即可在 `middleware` 列表中引用。
 
+#### RuntimeConfigMiddleware
+
+`RuntimeConfigMiddleware`（[runtime_config_middleware.py](https://github.com/xerrors/Yuxi-Know/blob/main/src/agents/common/middlewares/runtime_config_middleware.py)）是系统默认的核心中间件之一，负责在每次模型调用前自动注入运行时配置：
+
+1. **自动注入当前时间**：在 system prompt 开头追加当前时间，格式为 `当前时间：YYYY-MM-DD HH:MM:SS`，确保 LLM 能获取准确的时间上下文。
+2. **动态加载工具**：根据 `context.tools`、`context.knowledges`、`context.mcps` 自动组装可用工具列表。
+3. **模型选择**：根据 `context.model` 加载对应模型配置。
+
+如需自定义时间注入逻辑或禁用该行为，可继承该中间件并覆盖 `awrap_model_call` 方法。
+
 #### 文件上传中间件
 
 文件上传功能通过 `inject_attachment_context` 中间件实现（位于 `src/agents/common/middlewares/attachment_middleware.py`）。该中间件基于 LangChain 1.0 的 `AgentMiddleware` 标准实现，具有以下特点：

src/agents/common/middlewares/runtime_config_middleware.py

@@ -4,29 +4,15 @@ from collections.abc import Callable
 from typing import Any
 
 from langchain.agents.middleware import AgentMiddleware, ModelRequest, ModelResponse
+from langchain_core.messages import SystemMessage
 
 from src.agents.common import load_chat_model
-from src.agents.common.tools import get_kb_based_tools, get_buildin_tools
+from src.agents.common.tools import get_buildin_tools, get_kb_based_tools
 from src.services.mcp_service import get_enabled_mcp_tools
+from src.utils.datetime_utils import shanghai_now
 from src.utils.logging_config import logger
 
 
-def _is_system_message(msg: Any) -> bool:
-    if isinstance(msg, dict):
-        role = msg.get("role") or msg.get("type")
-        return role == "system"
-    msg_type = getattr(msg, "type", None) or getattr(msg, "role", None)
-    return msg_type == "system"
-
-
-def _get_message_content(msg: Any) -> str | None:
-    if isinstance(msg, dict):
-        content = msg.get("content")
-        return str(content) if content is not None else None
-    content = getattr(msg, "content", None)
-    return str(content) if content is not None else None
-
-
 class RuntimeConfigMiddleware(AgentMiddleware):
     """运行时配置中间件 - 应用模型/工具/知识库/MCP/提示词配置
 
@@ -54,35 +40,26 @@ class RuntimeConfigMiddleware(AgentMiddleware):
 
         model = load_chat_model(getattr(runtime_context, "model", None))
         enabled_tools = await self.get_tools_from_context(runtime_context)
-        system_prompt = getattr(runtime_context, "system_prompt", None)
-        logger.debug(f"RuntimeConfigMiddleware: model={model}, "
-                     f"tools={[t.name for t in enabled_tools]}. ")
 
-        existing_systems: list[Any] = []
-        remaining: list[Any] = []
-        in_prefix = True
-        for msg in request.messages:
-            if in_prefix and _is_system_message(msg):
-                existing_systems.append(msg)
-            else:
-                in_prefix = False
-                remaining.append(msg)
+        # 合并之前中间件设置的 tools，避免覆盖
+        existing_tools = list(request.tools or [])
+        merged_tools = existing_tools + enabled_tools
 
-        existing_contents = [_get_message_content(m) for m in existing_systems]
+        # 动态生成 system message，添加当前时间
+        cur_datetime = f"当前时间：{shanghai_now().strftime('%Y-%m-%d %H:%M:%S')} UTC"
+        system_prompt = getattr(runtime_context, "system_prompt", "") or ""
+        new_content = list(request.system_message.content_blocks) + [
+            {"type": "text", "text": f"{cur_datetime}\n\n{system_prompt}"}
+        ]
+        new_system_message = SystemMessage(content=new_content)
 
-        new_systems: list[Any] = []
-        if system_prompt:
-            try:
-                idx = existing_contents.index(system_prompt)
-            except ValueError:
-                new_systems.append({"role": "system", "content": system_prompt})
-            else:
-                new_systems.append(existing_systems.pop(idx))
-                existing_contents.pop(idx)
+        logger.debug(f"RuntimeConfigMiddleware: model={model}, tools={[t.name for t in merged_tools]}. ")
 
-        messages = [*new_systems, *existing_systems, *remaining]
-
-        request = request.override(model=model, tools=enabled_tools, messages=messages)
+        request = request.override(
+            model=model,
+            tools=merged_tools,
+            system_message=new_system_message
+        )
         return await handler(request)
 
     async def get_tools_from_context(self, context) -> list:

src/agents/deep_agent/graph.py

@@ -5,10 +5,8 @@ from deepagents.middleware.patch_tool_calls import PatchToolCallsMiddleware
 from deepagents.middleware.subagents import SubAgentMiddleware
 from langchain.agents import create_agent
 from langchain.agents.middleware import (
-    ModelRequest,
     SummarizationMiddleware,
     TodoListMiddleware,
-    dynamic_prompt,
 )
 
 from src.agents.common import BaseAgent, load_chat_model
@@ -17,7 +15,6 @@ from src.agents.common.tools import get_tavily_search
 from src.services.mcp_service import get_tools_from_all_servers
 
 from .context import DeepContext
-from .prompts import DEEP_PROMPT
 
 
 def _get_research_sub_agent(search_tools: list) -> dict:
@@ -57,12 +54,6 @@ critique_sub_agent = {
 }
 
 
-@dynamic_prompt
-def context_aware_prompt(request: ModelRequest) -> str:
-    """从 runtime context 动态生成系统提示词"""
-    return DEEP_PROMPT + "\n\n\n" + request.runtime.context.system_prompt
-
-
 class DeepAgent(BaseAgent):
     name = "深度分析智能体"
     description = "具备规划、深度分析和子智能体协作能力的智能体，可以处理复杂的多步骤任务"
@@ -111,7 +102,6 @@ class DeepAgent(BaseAgent):
             model=model,
             system_prompt=context.system_prompt,
             middleware=[
-                context_aware_prompt,  # 动态系统提示词
                 inject_attachment_context,  # 附件上下文注入
                 RuntimeConfigMiddleware(extra_tools=all_mcp_tools),
                 TodoListMiddleware(),