连接 Client — Downcity City SDK Docs

User City 有两条常用通路：

city.ai.* 调内置 AIService
city.service(id).action(name).invoke() 调自定义 Service 或服务 Service

import { City } from "@downcity/federation/legacy";

const city = new City({
  federation_url: "http://127.0.0.1:43127",
  user_token: "ub_xxx",
});

// AI Service — SDK 通路
const msg = await city.ai.text({ prompt: "hello", model: "deepseek-v4-flash" });
const stream = await city.ai.stream({ prompt: "hello", model: "deepseek-v4-flash" });

// AI Service — OpenAI 通路（用 OpenAI SDK 直接调）
import OpenAI from "openai";
const openai = new OpenAI({ baseURL: "http://127.0.0.1:43127/v1/ai", apiKey: "ub_xxx" });
await openai.chat.completions.create({ model: "deepseek-v4-flash", messages: [...] });

// 自定义 Service
const result = await city.service("translate").action("zh2en").invoke({ text: "你好" });

// GET action（如读取登录结果）
const login = await city.service("accounts").get("login/result", { login_id: "login_xxx" });

创建 Bureau、暂停 Bureau、请求 Federation 签发 user_token 和维护 Runtime env 都属于可信环境动作，用 FederationAdmin 发起，不放到产品前端。