如何流式传输图的完整状态¶

LangGraph 支持多种流式传输模式。主要的有

values：此流式传输模式流式传输图的值。这是在每次调用节点后，图的完整状态。
updates：此流式传输模式流式传输图的更新。这是在每次调用节点后，图的状态更新。

本指南涵盖 streamMode="values"。

// process.env.OPENAI_API_KEY = "sk-...";

定义状态¶

状态是我们图中所有节点的接口。

import { Annotation } from "@langchain/langgraph";
import { BaseMessage } from "@langchain/core/messages";

const StateAnnotation = Annotation.Root({
  messages: Annotation<BaseMessage[]>({
    reducer: (x, y) => x.concat(y),
  }),
});

设置工具¶

我们将首先定义我们要使用的工具。对于这个简单的示例，我们将创建一个占位符搜索引擎。但是，创建您自己的工具非常容易 - 请参阅此处的文档，了解如何操作。

import { tool } from "@langchain/core/tools";
import { z } from "zod";

const searchTool = tool(async ({ query: _query }: { query: string }) => {
  // This is a placeholder for the actual implementation
  return "Cold, with a low of 3℃";
}, {
  name: "search",
  description:
    "Use to surf the web, fetch current information, check the weather, and retrieve other information.",
  schema: z.object({
    query: z.string().describe("The query to use in your search."),
  }),
});

await searchTool.invoke({ query: "What's the weather like?" });

const tools = [searchTool];

我们现在可以将这些工具包装在一个简单的 ToolNode 中。此对象将在我们的 LLM 调用它们时实际运行工具（函数）。

import { ToolNode } from "@langchain/langgraph/prebuilt";

const toolNode = new ToolNode(tools);

设置模型¶

现在我们将加载聊天模型。

它应该与消息一起工作。我们将以消息的形式表示所有代理状态，因此它需要能够很好地与它们一起工作。
它应该与工具调用一起工作，这意味着它可以返回其响应中的函数参数。

注意

这些模型要求不是使用 LangGraph 的通用要求 - 它们只是此示例的要求。

import { ChatOpenAI } from "@langchain/openai";

const model = new ChatOpenAI({ model: "gpt-4o" });

完成此操作后，我们应确保模型知道它可以调用这些工具。我们可以通过调用 bindTools 来做到这一点。

const boundModel = model.bindTools(tools);

定义图¶

我们现在可以将所有内容放在一起。

import { END, START, StateGraph } from "@langchain/langgraph";
import { AIMessage } from "@langchain/core/messages";

const routeMessage = (state: typeof StateAnnotation.State) => {
  const { messages } = state;
  const lastMessage = messages[messages.length - 1] as AIMessage;
  // If no tools are called, we can finish (respond to the user)
  if (!lastMessage?.tool_calls?.length) {
    return END;
  }
  // Otherwise if there is, we continue and call the tools
  return "tools";
};

const callModel = async (
  state: typeof StateAnnotation.State,
) => {
  // For versions of @langchain/core < 0.2.3, you must call `.stream()`
  // and aggregate the message from chunks instead of calling `.invoke()`.
  const { messages } = state;
  const responseMessage = await boundModel.invoke(messages);
  return { messages: [responseMessage] };
};

const workflow = new StateGraph(StateAnnotation)
  .addNode("agent", callModel)
  .addNode("tools", toolNode)
  .addEdge(START, "agent")
  .addConditionalEdges("agent", routeMessage)
  .addEdge("tools", "agent");

const graph = workflow.compile();

流式传输值¶

我们现在可以与代理交互。在交互之间，您可以获取和更新状态。

let inputs = { messages: [{ role: "user", content: "what's the weather in sf" }] };

for await (
  const chunk of await graph.stream(inputs, {
    streamMode: "values",
  })
) {
  console.log(chunk["messages"]);
  console.log("\n====\n");
}

[ [ 'user', "what's the weather in sf" ] ]

====

[
  [ 'user', "what's the weather in sf" ],
  AIMessage {
    "id": "chatcmpl-9y660d49eLzT7DZeBk2ZmX8C5f0LU",
    "content": "",
    "additional_kwargs": {
      "tool_calls": [
        {
          "id": "call_iD5Wk4vPsTckffDKJpEQaMkg",
          "type": "function",
          "function": "[Object]"
        }
      ]
    },
    "response_metadata": {
      "tokenUsage": {
        "completionTokens": 17,
        "promptTokens": 70,
        "totalTokens": 87
      },
      "finish_reason": "tool_calls",
      "system_fingerprint": "fp_3aa7262c27"
    },
    "tool_calls": [
      {
        "name": "search",
        "args": {
          "query": "current weather in San Francisco"
        },
        "type": "tool_call",
        "id": "call_iD5Wk4vPsTckffDKJpEQaMkg"
      }
    ],
    "invalid_tool_calls": [],
    "usage_metadata": {
      "input_tokens": 70,
      "output_tokens": 17,
      "total_tokens": 87
    }
  }
]

====

[
  [ 'user', "what's the weather in sf" ],
  AIMessage {
    "id": "chatcmpl-9y660d49eLzT7DZeBk2ZmX8C5f0LU",
    "content": "",
    "additional_kwargs": {
      "tool_calls": [
        {
          "id": "call_iD5Wk4vPsTckffDKJpEQaMkg",
          "type": "function",
          "function": "[Object]"
        }
      ]
    },
    "response_metadata": {
      "tokenUsage": {
        "completionTokens": 17,
        "promptTokens": 70,
        "totalTokens": 87
      },
      "finish_reason": "tool_calls",
      "system_fingerprint": "fp_3aa7262c27"
    },
    "tool_calls": [
      {
        "name": "search",
        "args": {
          "query": "current weather in San Francisco"
        },
        "type": "tool_call",
        "id": "call_iD5Wk4vPsTckffDKJpEQaMkg"
      }
    ],
    "invalid_tool_calls": [],
    "usage_metadata": {
      "input_tokens": 70,
      "output_tokens": 17,
      "total_tokens": 87
    }
  },
  ToolMessage {
    "content": "Cold, with a low of 3℃",
    "name": "search",
    "additional_kwargs": {},
    "response_metadata": {},
    "tool_call_id": "call_iD5Wk4vPsTckffDKJpEQaMkg"
  }
]

====

[
  [ 'user', "what's the weather in sf" ],
  AIMessage {
    "id": "chatcmpl-9y660d49eLzT7DZeBk2ZmX8C5f0LU",
    "content": "",
    "additional_kwargs": {
      "tool_calls": [
        {
          "id": "call_iD5Wk4vPsTckffDKJpEQaMkg",
          "type": "function",
          "function": "[Object]"
        }
      ]
    },
    "response_metadata": {
      "tokenUsage": {
        "completionTokens": 17,
        "promptTokens": 70,
        "totalTokens": 87
      },
      "finish_reason": "tool_calls",
      "system_fingerprint": "fp_3aa7262c27"
    },
    "tool_calls": [
      {
        "name": "search",
        "args": {
          "query": "current weather in San Francisco"
        },
        "type": "tool_call",
        "id": "call_iD5Wk4vPsTckffDKJpEQaMkg"
      }
    ],
    "invalid_tool_calls": [],
    "usage_metadata": {
      "input_tokens": 70,
      "output_tokens": 17,
      "total_tokens": 87
    }
  },
  ToolMessage {
    "content": "Cold, with a low of 3℃",
    "name": "search",
    "additional_kwargs": {},
    "response_metadata": {},
    "tool_call_id": "call_iD5Wk4vPsTckffDKJpEQaMkg"
  },
  AIMessage {
    "id": "chatcmpl-9y660ZKNXvziVJze0X5aTlZ5IoN35",
    "content": "Currently, in San Francisco, it's cold with a temperature of around 3℃ (37.4°F).",
    "additional_kwargs": {},
    "response_metadata": {
      "tokenUsage": {
        "completionTokens": 23,
        "promptTokens": 103,
        "totalTokens": 126
      },
      "finish_reason": "stop",
      "system_fingerprint": "fp_3aa7262c27"
    },
    "tool_calls": [],
    "invalid_tool_calls": [],
    "usage_metadata": {
      "input_tokens": 103,
      "output_tokens": 23,
      "total_tokens": 126
    }
  }
]

====