MCP_SESSION_ID is improperly named

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未提供文件、测试、入口点、环境、复现步骤或预期命名。首先在仓库和现有 issue 中搜索对 MCP_SESSION_ID 的引用，然后明确预期的名称和受影响的用法。完成的标准是复现命名差异、确认预期标识符，并且相关测试通过。