bugfix：修复一些bug

app/clients/mcp.py

@@ -8,6 +8,7 @@
 import asyncio
 import json
 import os
+import re
 import socket
 import subprocess
 import sys
@@ -29,18 +30,37 @@ CONFIG_PATH = PROJECT_ROOT / "mcp_servers.json"
 # 物料服务返回的目录版本须与主进程一致，否则模型查到的字段和校验依据不同
 MATERIAL_SERVER = "materials"
 LOCAL_HOSTS = {"localhost", "127.0.0.1"}
+# 配置中引用环境变量的写法
+ENV_REFERENCE = re.compile(r"\$\{(\w+)\}")
 
 
 class MCPServiceError(RuntimeError):
     """MCP 配置错误、服务不可用，或物料目录版本不一致"""
 
 
+def _expand_env(value):
+    """只展开字符串值里的 ${NAME}；变量未设置时报错，不把字面量当成地址或密钥"""
+    if isinstance(value, dict):
+        return {key: _expand_env(item) for key, item in value.items()}
+    if isinstance(value, list):
+        return [_expand_env(item) for item in value]
+    if not isinstance(value, str):
+        return value
+
+    def lookup(match: re.Match) -> str:
+        if (found := os.environ.get(match[1])) is None:
+            raise MCPServiceError(f"MCP 服务配置引用的环境变量 {match[1]} 未设置")
+        return found
+
+    return ENV_REFERENCE.sub(lookup, value)
+
+
 def load_mcp_config(path: Path = CONFIG_PATH) -> dict[str, dict]:
     """读取服务列表并展开环境变量；文件缺失或格式不对时报错"""
     if not path.exists():
         raise MCPServiceError(f"未找到 MCP 服务配置: {path}")
     try:
-        config = json.loads(os.path.expandvars(path.read_text(encoding="utf-8")))
+        config = _expand_env(json.loads(path.read_text(encoding="utf-8")))
     except json.JSONDecodeError as error:
         raise MCPServiceError(f"MCP 服务配置不是合法 JSON: {error}") from error
     if not isinstance(config, dict) or not all(