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import { tool } from "@langchain/core/tools";
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import { z } from "zod";
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import { ChatOpenAI } from "@langchain/openai";
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const getProductStock = tool(
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  async ({ sku }) => getProductBySku(sku),     // ① 实际执行函数
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  {
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    name: "get_product_stock",                  // ② AI 用的名字
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    description: "按 SKU 查商品名与库存",        // ③ AI 读这个决定要不要调
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    schema: z.object({ sku: z.string() }),      // ④ 参数类型
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  }
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);

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START
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  ↓
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[agent]（LLM 思考：要不要调工具？）
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  ↓
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◇ toolsCondition
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  ├── 有 tool_calls → [tools]（执行工具）→ 回 [agent] 🔄
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  └── 无 tool_calls → END ✅

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① [HumanMessage("SKU-003 还剩多少库存？")]
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         ↓ agent 节点（LLM 分析：我需要查库存）
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② [HumanMessage, AIMessage(tool_calls: get_product_stock("SKU-003"))]
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         ↓ toolsCondition → 有 tool_calls → 去 tools
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③ [HumanMessage, AIMessage, ToolMessage("USB-C 线缆, 库存 120")]
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         ↓ 回到 agent（LLM 拿到数据，组织回答）
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④ [HumanMessage, AIMessage, ToolMessage, AIMessage("USB-C 线缆库存120件")]
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         ↓ toolsCondition → 无 tool_calls → END ✅

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import { ToolNode, toolsCondition } from "@langchain/langgraph/prebuilt";
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const toolNode = new ToolNode(tools);
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const graph = new StateGraph(MessagesAnnotation)
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  .addNode("agent", agentFn)
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  .addNode("tools", toolNode)
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  .addEdge(START, "agent")
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  .addConditionalEdges("agent", toolsCondition, ["tools", END])
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  .addEdge("tools", "agent")
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  .compile();

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import { createReactAgent } from "@langchain/langgraph/prebuilt";
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const agent = createReactAgent({
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  llm: model,           // ★ 参数名 llm，不是 model
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  tools: [getProductStock],
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  systemPrompt: "你是仓库助手...",
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  checkpointer: new MemorySaver(),
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});
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const result = await agent.invoke({
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  messages: [new HumanMessage("SKU-002 还剩多少？")],
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});

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const weatherAgent = createReactAgent({
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  name: "weather_agent",     // ★ 必须，supervisor 用它识别
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  llm: model,
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  tools: [lookupWeatherTool],
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  systemPrompt: "你只处理天气...",
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});
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const triviaAgent = createReactAgent({
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  name: "trivia_agent",
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  llm: model,
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  tools: [lookupCityTriviaTool],
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  systemPrompt: "你只讲城市小知识...",
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});

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const workflow = createSupervisor({
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  agents: [weatherAgent, triviaAgent],  // 直接传实例
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  llm: model,
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  prompt: `你是调度员，只负责选人。
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- 问天气 → 用 weather_agent
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- 问小知识 → 用 trivia_agent`,
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  addHandoffBackMessages: false,
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});

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👤 用户：成都今天天气怎么样？
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  🔧 supervisor 调用: transfer_to_weather_agent({})    ← 调度
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  📦 工具返回: Successfully transferred               ← handoff 完成
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  🔧 weather_agent 调用: lookup_weather("成都")        ← 子 Agent 开工
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  📦 工具返回: {"summary":"多云","tempHighC":27,...}   ← 真实数据
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  💬 weather_agent 回复: 成都今天多云，22~27°C，空气质量中高度污染...

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const stream = await app.stream(
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  { messages: [new HumanMessage(QUERY)] },
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  { streamMode: "values" }
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);
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let prevMsgCount = 0;
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for await (const event of stream) {
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  const msgs = event?.messages ?? [];
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  for (let i = prevMsgCount; i < msgs.length; i++) {
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    const m = msgs[i];
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    if (m.tool_calls?.length) console.log(`  🔧 调用: ${...}`);
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    else if (m._getType?.() === "tool") console.log(`  📦 工具返回: ${...}`);
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    else if (m._getType?.() === "ai") console.log(`  💬 回答: ${...}`);
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  }
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  prevMsgCount = msgs.length;
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}