feat: MCP 客户端（连接外部 MCP server，外部工具桥接进统一工具体系）

- 新增 mcp_client.py：McpClient（subprocess stdio JSON-RPC，reader 线程+响应表，
  initialize/list_tools/call_tool/shutdown 超时可控）+ McpClientManager（connect_all
  读 mcpServers、聚合、call_tool、cleanup 幂等）
- unified_tool_manager.py：initialize 末尾加载外部 MCP server，按 server__tool 前缀
  register_tool 带真实 inputSchema mcp_definition，shutdown 经 manager.cleanup 幂等终止子进程
- fc_tools.py：mcp_to_openai_tools 新增 get_mcp_tools 保真分支（同时修现状 liugin 工具
  schema 被压成 args 的坑）
- config.json：顶层加 mcpServers 空段（用户自填，已被 gitignore 不入库，代码 .get 兼容）
- 新增 tests/test_mcp_client.py（5 项，全链路+桥接+保真，不触真实引擎/网络）

Co-Authored-By: WorkBuddy <workbuddy@tencent.com>

mcp_client.py

@@ -0,0 +1,306 @@
+"""
+小狸 MCP 客户端
+===============
+连接外部 MCP (Model Context Protocol) server，将其工具桥接进小狸的统一工具体系。
+
+- transport = stdio（subprocess + 逐行 JSON-RPC 2.0），与项目根 mcp_server.py（暴露侧）对称。
+- 同步 + 线程安全：契合小狸「同步主循环 + ThreadPoolExecutor」模型，不引入官方 mcp SDK
+  （其 asyncio 风格与现有同步调用链不搭）。
+- 单个 server 失败不阻断其他 server，也不阻断主程序启动。
+
+后续可在此文件扩展 SSE / HTTP transport（McpClient 子类即可）。
+"""
+
+import os
+import json
+import time
+import threading
+import subprocess
+import logging
+from typing import Dict, List, Any, Optional, Tuple
+
+logger = logging.getLogger(__name__)
+
+PROTOCOL_VERSION = "2024-11-05"
+
+
+class McpClientError(RuntimeError):
+    """MCP 客户端错误"""
+
+
+class McpClient:
+    """单个 MCP server 的 stdio 客户端（同步、线程安全）"""
+
+    def __init__(self, name: str, command: str, args: Optional[List[str]] = None,
+                 env: Optional[Dict[str, str]] = None, cwd: Optional[str] = None,
+                 timeout: float = 30.0):
+        self.name = name
+        self.command = command
+        self.args = list(args or [])
+        self.env = env or {}
+        self.cwd = cwd
+        self.timeout = timeout
+
+        self.proc = None
+        self._lock = threading.RLock()
+        self._next_id = 1
+        self._pending: Dict[int, Dict[str, Any]] = {}
+        self._reader_thread = None
+        self._started = False
+
+    # ── 生命周期 ──
+    def start(self) -> None:
+        """启动子进程并开启 reader 线程"""
+        if self._started:
+            return
+        full_env = dict(os.environ)
+        full_env.update(self.env)
+        cmd = [self.command] + self.args
+        try:
+            self.proc = subprocess.Popen(
+                cmd,
+                stdin=subprocess.PIPE,
+                stdout=subprocess.PIPE,
+                stderr=subprocess.DEVNULL,
+                cwd=self.cwd,
+                env=full_env,
+                text=True,
+                encoding="utf-8",
+                bufsize=1,
+            )
+        except Exception as e:
+            raise McpClientError(f"启动 MCP server '{self.name}' 失败: {e}")
+
+        self._reader_thread = threading.Thread(target=self._reader_loop, daemon=True)
+        self._reader_thread.start()
+        self._started = True
+
+    def _reader_loop(self):
+        """后台读线程：逐行解析 JSON-RPC 响应，按 id 投递到 _pending 表"""
+        try:
+            for raw in self.proc.stdout:
+                line = raw.strip()
+                if not line:
+                    continue
+                try:
+                    msg = json.loads(line)
+                except json.JSONDecodeError:
+                    # 容错：跳过 server 可能混入 stdout 的非 JSON 噪声
+                    continue
+                msg_id = msg.get("id")
+                if msg_id is None:
+                    # 通知（如进度），忽略
+                    continue
+                with self._lock:
+                    pend = self._pending.pop(msg_id, None)
+                if pend is not None:
+                    if "error" in msg:
+                        pend["error"] = msg["error"]
+                    else:
+                        pend["value"] = msg.get("result")
+                    pend["event"].set()
+        except Exception:
+            pass
+        finally:
+            # 连接断开：唤醒所有等待中的请求，避免永久阻塞
+            with self._lock:
+                pendings = list(self._pending.values())
+                self._pending.clear()
+            for pend in pendings:
+                pend["error"] = {"code": -1, "message": "MCP server 连接断开"}
+                pend["event"].set()
+
+    def _send(self, method: str, params: Any = None,
+              is_notification: bool = False) -> Optional[Any]:
+        """发送一个 JSON-RPC 请求；非通知则等待响应（带超时）"""
+        if not self._started or self.proc is None:
+            raise McpClientError(f"MCP client '{self.name}' 未启动")
+
+        with self._lock:
+            if is_notification:
+                req = {"jsonrpc": "2.0", "method": method, "params": params or {}}
+                pend = None
+                req_id = None
+            else:
+                req_id = self._next_id
+                self._next_id += 1
+                pend = {"event": threading.Event(), "value": None, "error": None}
+                self._pending[req_id] = pend
+                req = {"jsonrpc": "2.0", "id": req_id, "method": method, "params": params or {}}
+
+        try:
+            self.proc.stdin.write(json.dumps(req, ensure_ascii=False) + "\n")
+            self.proc.stdin.flush()
+        except (BrokenPipeError, ValueError, OSError) as e:
+            raise McpClientError(f"向 MCP server '{self.name}' 写入失败: {e}")
+
+        if is_notification:
+            return None
+
+        if not pend["event"].wait(self.timeout):
+            with self._lock:
+                self._pending.pop(req_id, None)
+            raise McpClientError(f"MCP server '{self.name}' 响应超时: {method}")
+        if pend["error"]:
+            err = pend["error"]
+            raise McpClientError(
+                f"MCP server '{self.name}' 错误 [{err.get('code')}]: {err.get('message')}")
+        return pend["value"]
+
+    # ── MCP 协议方法 ──
+    def initialize(self) -> Dict[str, Any]:
+        """握手：协商协议版本并通知初始化完成"""
+        result = self._send("initialize", {
+            "protocolVersion": PROTOCOL_VERSION,
+            "capabilities": {},
+            "clientInfo": {"name": "xiaoli-cli", "version": "8.0"},
+        })
+        # 通知 server 初始化完成（无响应，无需等待）
+        self._send("notifications/initialized", {}, is_notification=True)
+        return result or {}
+
+    def list_tools(self) -> List[Dict[str, Any]]:
+        """列出 server 提供的工具定义"""
+        result = self._send("tools/list", {})
+        if isinstance(result, dict):
+            return result.get("tools", [])
+        return []
+
+    def call_tool(self, tool_name: str, arguments: Dict[str, Any]) -> str:
+        """调用一个工具，返回文本结果"""
+        result = self._send("tools/call", {"name": tool_name, "arguments": arguments or {}})
+        return self._extract_content(result)
+
+    @staticmethod
+    def _extract_content(result: Any) -> str:
+        """从 tools/call 的 result 提取文本结果"""
+        if result is None:
+            return ""
+        if isinstance(result, str):
+            return result
+        if isinstance(result, dict):
+            content = result.get("content")
+            if isinstance(content, list):
+                parts = []
+                for item in content:
+                    if isinstance(item, dict):
+                        if item.get("type") == "text" or "text" in item:
+                            parts.append(str(item.get("text", "")))
+                return "\n".join(p for p in parts if p)
+            if isinstance(result.get("content"), str):
+                return result["content"]
+            # 部分 server 直接把结果放 result 顶层
+            if "isError" in result and result.get("isError"):
+                return f"[工具错误] {json.dumps(result, ensure_ascii=False)}"
+            return json.dumps(result, ensure_ascii=False)
+        return str(result)
+
+    def ping(self) -> bool:
+        try:
+            self._send("ping", {})
+            return True
+        except Exception:
+            return False
+
+    def stop(self) -> None:
+        """优雅关闭子进程，失败则强杀"""
+        if self.proc is None:
+            return
+        try:
+            self._send("shutdown", {})
+        except Exception:
+            pass
+        try:
+            self._send("exit", {}, is_notification=True)
+        except Exception:
+            pass
+        try:
+            self.proc.stdin.close()
+        except Exception:
+            pass
+        try:
+            self.proc.wait(timeout=3)
+        except Exception:
+            try:
+                self.proc.kill()
+            except Exception:
+                pass
+        self._started = False
+
+
+class McpClientManager:
+    """管理多个外部 MCP server 客户端（按配置并发连接、聚合工具）"""
+
+    def __init__(self):
+        self.clients: Dict[str, McpClient] = {}
+        self._tool_index: List[Tuple[str, Dict[str, Any]]] = []  # (server_name, tool_def)
+        self._lock = threading.RLock()
+        self._cleaned = False
+
+    def connect_all(self, servers: Dict[str, Dict[str, Any]],
+                    cwd: Optional[str] = None) -> None:
+        """连接所有已声明且未禁用的 server。单个失败不阻断其他。
+
+        servers: {name: {"command", "args", "env", "cwd", "disabled"}}
+        """
+        for name, spec in servers.items():
+            if not isinstance(spec, dict):
+                continue
+            if spec.get("disabled"):
+                logger.info(f"MCP server '{name}' 已禁用，跳过")
+                continue
+            command = spec.get("command")
+            if not command:
+                logger.warning(f"MCP server '{name}' 缺少 command，跳过")
+                continue
+            args = spec.get("args") or []
+            env = spec.get("env") or {}
+            server_cwd = spec.get("cwd") or cwd
+            client = McpClient(name, command, args, env, server_cwd)
+            try:
+                client.start()
+                client.initialize()
+                tools = client.list_tools()
+                with self._lock:
+                    self.clients[name] = client
+                    for tool in tools:
+                        self._tool_index.append((name, tool))
+                logger.info(f"已连接 MCP server '{name}': {len(tools)} 个工具")
+            except Exception as e:
+                try:
+                    client.stop()
+                except Exception:
+                    pass
+                logger.error(f"连接 MCP server '{name}' 失败: {e}")
+                # 不向上抛，继续下一个 server
+
+    def get_all_tools(self) -> List[Tuple[str, Dict[str, Any]]]:
+        """返回 [(server_name, tool_def), ...]"""
+        with self._lock:
+            return list(self._tool_index)
+
+    def get_servers(self) -> List[str]:
+        with self._lock:
+            return list(self.clients.keys())
+
+    def call_tool(self, server_name: str, tool_name: str, arguments: Dict[str, Any]) -> str:
+        with self._lock:
+            client = self.clients.get(server_name)
+        if client is None:
+            raise McpClientError(f"未连接的 MCP server: {server_name}")
+        return client.call_tool(tool_name, arguments)
+
+    def cleanup(self) -> None:
+        """幂等：终止所有子进程。每个桥接工具的 shutdown 都会调一次，故必须可重入。"""
+        with self._lock:
+            if self._cleaned:
+                return
+            self._cleaned = True
+            clients = list(self.clients.values())
+            self.clients.clear()
+            self._tool_index.clear()
+        for client in clients:
+            try:
+                client.stop()
+            except Exception:
+                pass

tests/test_mcp_client.py

@@ -0,0 +1,193 @@
+"""
+MCP 客户端测试
+==============
+用 inline 的 fake MCP server（写入临时文件，subprocess 启动）验证：
+
+1. McpClient 全链路：start → initialize → list_tools → call_tool → stop（进程回收）
+2. McpClientManager 多 server 并发连接、聚合、调用、cleanup 幂等
+3. 超时：沉默 server 不响应 → call_tool 应在 timeout 内抛错
+4. UnifiedToolManager 桥接：外部 MCP 工具按 {server}__{tool} 注册、schema 保真、可被 execute 调用、shutdown 清理子进程
+5. fc_tools.mcp_to_openai_tools 优先走 get_mcp_tools 保真分支（不把 schema 压成 args）
+
+全程不依赖真实 AI 引擎、网络或外部 npx。
+"""
+
+import os
+import sys
+
+import pytest
+
+# 确保项目根在 sys.path（unified_tool_manager / mcp_client / config 均在根目录）
+ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+if ROOT not in sys.path:
+    sys.path.insert(0, ROOT)
+
+from mcp_client import McpClient, McpClientManager, McpClientError  # noqa: E402
+import unified_tool_manager as utm  # noqa: E402
+from xcli_core.fc_tools import mcp_to_openai_tools  # noqa: E402
+
+# fake MCP server：实现 initialize / tools/list / tools/call / ping，
+# 以及一个 echo 工具（inputSchema 保真）。与 mcp_server.py 协议对称。
+FAKE_SERVER_SRC = r'''
+import sys, json
+
+def send(obj):
+    sys.stdout.write(json.dumps(obj, ensure_ascii=False) + "\n")
+    sys.stdout.flush()
+
+def main():
+    for line in sys.stdin:
+        line = line.strip()
+        if not line:
+            continue
+        try:
+            req = json.loads(line)
+        except Exception:
+            continue
+        method = req.get("method", "")
+        mid = req.get("id")
+        if method == "notifications/initialized":
+            continue
+        if method == "initialize":
+            send({"jsonrpc": "2.0", "id": mid, "result": {
+                "protocolVersion": "2024-11-05",
+                "capabilities": {"tools": {}},
+                "serverInfo": {"name": "fake", "version": "1.0"},
+            }})
+        elif method == "tools/list":
+            send({"jsonrpc": "2.0", "id": mid, "result": {"tools": [{
+                "name": "echo",
+                "description": "回声工具",
+                "inputSchema": {
+                    "type": "object",
+                    "properties": {"text": {"type": "string", "description": "要回声的文本"}},
+                    "required": ["text"],
+                },
+            }]}})
+        elif method == "tools/call":
+            params = req.get("params", {})
+            name = params.get("name")
+            args = params.get("arguments", {})
+            if name == "echo":
+                send({"jsonrpc": "2.0", "id": mid, "result": {
+                    "content": [{"type": "text", "text": "echo: " + str(args.get("text", ""))}],
+                }})
+            else:
+                send({"jsonrpc": "2.0", "id": mid, "error": {"code": -32601, "message": "unknown tool"}})
+        elif method == "ping":
+            send({"jsonrpc": "2.0", "id": mid, "result": {}})
+        else:
+            send({"jsonrpc": "2.0", "id": mid, "error": {"code": -32601, "message": "method not found"}})
+
+if __name__ == "__main__":
+    main()
+'''
+
+
+@pytest.fixture
+def fake_server_path(tmp_path):
+    p = tmp_path / "fake_mcp_server.py"
+    p.write_text(FAKE_SERVER_SRC)
+    return str(p)
+
+
+def test_mcp_client_lifecycle(fake_server_path):
+    client = McpClient("fake", sys.executable, [fake_server_path])
+    try:
+        client.start()
+        info = client.initialize()
+        assert info.get("protocolVersion") == "2024-11-05"
+        tools = client.list_tools()
+        assert any(t.get("name") == "echo" for t in tools)
+        out = client.call_tool("echo", {"text": "hi"})
+        assert "hi" in out
+    finally:
+        client.stop()
+    # 进程应已被回收
+    assert client.proc.poll() is not None
+
+
+def test_manager_multi_server(fake_server_path):
+    mgr = McpClientManager()
+    mgr.connect_all({
+        "a": {"command": sys.executable, "args": [fake_server_path]},
+        "b": {"command": sys.executable, "args": [fake_server_path]},
+    })
+    assert set(mgr.get_servers()) == {"a", "b"}
+    assert len(mgr.get_all_tools()) == 2
+    out = mgr.call_tool("a", "echo", {"text": "x"})
+    assert "x" in out
+    mgr.cleanup()
+    mgr.cleanup()  # 幂等
+
+
+def test_client_timeout(tmp_path):
+    silent = tmp_path / "silent.py"
+    silent.write_text("import time\nwhile True:\n    time.sleep(1)\n")
+    client = McpClient("silent", sys.executable, [str(silent)], timeout=2)
+    try:
+        client.start()
+        with pytest.raises(Exception):
+            client.list_tools()  # 沉默 server 不响应 → 超时
+    finally:
+        client.stop()
+
+
+def test_unified_manager_bridges_external_mcp(tmp_path, monkeypatch):
+    fake = tmp_path / "fake_mcp_server.py"
+    fake.write_text(FAKE_SERVER_SRC)
+    cfg = {"mcpServers": {"fake": {"command": sys.executable, "args": [str(fake)]}}}
+
+    import xcli_core.config as xcfg
+    monkeypatch.setattr(xcfg, "load_config", lambda: cfg)
+    try:
+        import config as root_cfg
+        monkeypatch.setattr(root_cfg, "load_config", lambda: cfg)
+    except ImportError:
+        pass
+
+    mgr = utm.UnifiedToolManager()
+    # 用不存在的插件/技能目录，避免加载真实插件
+    mgr.initialize(
+        plugins_dir=str(tmp_path / "noplugins"),
+        skills_dir=str(tmp_path / "noskills"),
+    )
+    try:
+        tool = mgr.get_tool("fake__echo")
+        assert tool is not None, "外部 MCP 工具应已桥接为 fake__echo"
+        assert tool["protocol"] == "mcp"
+
+        names = [t["name"] for t in mgr.get_mcp_tools()]
+        assert "fake__echo" in names
+
+        echo_def = next(t for t in mgr.get_mcp_tools() if t["name"] == "fake__echo")
+        assert "text" in echo_def["inputSchema"]["properties"]
+
+        res = mgr.execute("fake__echo", '{"text": "hello"}')
+        assert res.success
+        assert "hello" in (res.data or "")
+    finally:
+        mgr.shutdown()
+
+
+def test_fc_tools_uses_get_mcp_tools():
+    class FakeMgr:
+        def get_mcp_tools(self):
+            return [{
+                "name": "my_tool",
+                "description": "d",
+                "inputSchema": {
+                    "type": "object",
+                    "properties": {"q": {"type": "string"}},
+                    "required": ["q"],
+                },
+            }]
+
+    tools = mcp_to_openai_tools(FakeMgr())
+    my = next(t for t in tools if t["function"]["name"] == "my_tool")
+    # schema 保真：不被压成 {"args": string}
+    assert "q" in my["function"]["parameters"]["properties"]
+    assert "args" not in my["function"]["parameters"]["properties"]
+    # 内置工具（memory / scheduler）仍被追加
+    names = [t["function"]["name"] for t in tools]
+    assert "memory" in names and "scheduler" in names

unified_tool_manager.py

@@ -12,6 +12,11 @@ from colorama import Fore, Style
 from xcli_core.tool_result import ToolResult, ErrorCode
 from xcli_core.verbose import vprint
 
+try:
+    from mcp_client import McpClientManager
+except Exception:
+    McpClientManager = None
+
 logger = logging.getLogger(__name__)
 
 
@@ -48,6 +53,9 @@ class UnifiedToolManager:
         # MCP 工具定义缓存
         self._mcp_tools_cache: Optional[List[Dict]] = None
 
+        # 外部 MCP client 管理器（懒加载）
+        self._mcp_client_manager = None
+
     def initialize(self, plugins_dir: str = "plugins", skills_dir: str = "skills") -> None:
         """初始化并加载所有工具"""
         self._plugins_dir = plugins_dir
@@ -55,6 +63,7 @@ class UnifiedToolManager:
         self._load_plugins(plugins_dir)
         self._load_skills(skills_dir)
         self._build_mcp_cache()
+        self._load_mcp_servers()
 
         n_liugin = sum(1 for p in self._protocol_map.values() if p == 'liugin')
         n_skill = sum(1 for p in self._protocol_map.values() if p == 'skill')
@@ -302,6 +311,93 @@ class UnifiedToolManager:
             }
         }
 
+    # ==================== 外部 MCP 客户端桥接 ====================
+
+    def _load_mcp_servers(self) -> None:
+        """连接 config.json 中声明的外部 MCP server，将其工具桥接进统一注册表。
+
+        外部工具以 ``{server}__{tool}`` 命名注册，schema（inputSchema）保真，
+        模型可像调用本地工具一样调用外部 MCP 工具。
+        """
+        if McpClientManager is None:
+            return
+        try:
+            from config import load_config
+        except ImportError:
+            try:
+                from xcli_core.config import load_config
+            except ImportError:
+                return
+
+        try:
+            cfg = load_config()
+            servers = cfg.get("mcpServers") or {}
+        except Exception:
+            return
+
+        if not servers:
+            return
+
+        if self._mcp_client_manager is None:
+            self._mcp_client_manager = McpClientManager()
+
+        # unified_tool_manager.py 位于项目根，故 dirname(__file__) 即项目根
+        project_dir = os.path.dirname(os.path.abspath(__file__))
+
+        try:
+            self._mcp_client_manager.connect_all(servers, cwd=project_dir)
+        except Exception as e:
+            print(f"{Fore.YELLOW}加载外部 MCP server 失败: {e}{Style.RESET_ALL}")
+            return
+
+        added = 0
+        for server_name, tool_def in self._mcp_client_manager.get_all_tools():
+            remote_name = tool_def.get("name")
+            if not remote_name:
+                continue
+            local_name = f"{server_name}__{remote_name}"
+            mcp_def = {
+                "name": local_name,
+                "description": tool_def.get("description", ""),
+                "inputSchema": tool_def.get("inputSchema", {"type": "object", "properties": {}}),
+            }
+            handler = self._make_external_handler(server_name, remote_name)
+            # instance 存 manager，shutdown 时统一 cleanup（McpClientManager.cleanup 幂等）
+            self.register_tool(
+                local_name, handler,
+                description=mcp_def["description"],
+                protocol="mcp",
+                mcp_definition=mcp_def,
+                instance=self._mcp_client_manager,
+            )
+            added += 1
+
+        if added:
+            n_servers = len(self._mcp_client_manager.get_servers())
+            print(f"{Fore.GREEN}已桥接 {added} 个外部 MCP 工具{Style.RESET_ALL}"
+                  f"{Fore.BLACK}{Style.BRIGHT} (来自 {n_servers} 个 server){Style.RESET_ALL}")
+
+    def _make_external_handler(self, server_name: str, remote_name: str):
+        """为某个外部 MCP 工具生成 handler：解析参数 → call_tool → ToolResult"""
+        def handler(args):
+            try:
+                if isinstance(args, dict):
+                    arguments = args
+                elif isinstance(args, str) and args.strip().startswith("{"):
+                    arguments = json.loads(args)
+                else:
+                    arguments = {"args": args}
+            except (json.JSONDecodeError, TypeError):
+                arguments = {"args": args}
+
+            try:
+                result_text = self._mcp_client_manager.call_tool(server_name, remote_name, arguments)
+                return ToolResult.ok(result_text, tool_name=f"{server_name}__{remote_name}")
+            except Exception as e:
+                return ToolResult.fail(str(e), ErrorCode.EXEC_FAILED,
+                                       tool_name=f"{server_name}__{remote_name}")
+        return handler
+
     # ==================== 公共 API ====================
 
     @property

xcli_core/fc_tools.py

@@ -21,8 +21,17 @@ def mcp_to_openai_tools(plugin_manager) -> List[Dict]:
     if not plugin_manager:
         return tools
 
-    # 统一工具管理器
+    # 优先使用统一工具管理器的 MCP 定义（含外部 MCP client 桥接的工具，schema 保真）
-    if hasattr(plugin_manager, 'plugins'):
+    if hasattr(plugin_manager, 'get_mcp_tools'):
+        try:
+            for mcp_def in plugin_manager.get_mcp_tools():
+                fc_def = mcp_to_fc(mcp_def)
+                if fc_def:
+                    tools.append(fc_def)
+        except Exception:
+            pass
+    # 统一工具管理器（兜底，旧实现未暴露 get_mcp_tools 时）
+    elif hasattr(plugin_manager, 'plugins'):
         for plugin in plugin_manager.plugins:
             fc_def = _extract_fc_def(plugin)
             if fc_def: