LangSmith Client SDK

This package contains the TypeScript client for interacting with the LangSmith platform.

To install:

yarn add langsmith

LangSmith helps you and your team develop and evaluate language models and intelligent agents. It is compatible with any LLM Application and provides seamless integration with LangChain, a widely recognized open-source framework that simplifies the process for developers to create powerful language model applications.

Note: You can enjoy the benefits of LangSmith without using the LangChain open-source packages! To get started with your own proprietary framework, set up your account and then skip to Logging Traces Outside LangChain.

Cookbook: For tutorials on how to get more value out of LangSmith, check out the Langsmith Cookbook repo.

A typical workflow looks like:

1. Set up an account with LangSmith.
2. Log traces.
3. Debug, Create Datasets, and Evaluate Runs.

We'll walk through these steps in more detail below.

1. Connect to LangSmith

Sign up for LangSmith using your GitHub, Discord accounts, or an email address and password. If you sign up with an email, make sure to verify your email address before logging in.

Then, create a unique API key on the Settings Page.

Note: Save the API Key in a secure location. It will not be shown again.

2. Log Traces

You can log traces natively in your LangChain application or using a LangSmith RunTree.

Logging Traces with LangChain

LangSmith seamlessly integrates with the JavaScript LangChain library to record traces from your LLM applications.

yarn add langchain

1. Copy the environment variables from the Settings Page and add them to your application.

Tracing can be activated by setting the following environment variables or by manually specifying the LangChainTracer.

process.env["LANGCHAIN_TRACING_V2"] = "true";
process.env["LANGCHAIN_ENDPOINT"] = "https://api.smith.langchain.com";
process.env["LANGCHAIN_API_KEY"] = "<YOUR-LANGSMITH-API-KEY>";
// process.env["LANGCHAIN_PROJECT"] = "My Project Name"; // Optional: "default" is used if not set

Tip: Projects are groups of traces. All runs are logged to a project. If not specified, the project is set to default.

2. Run an Agent, Chain, or Language Model in LangChain

If the environment variables are correctly set, your application will automatically connect to the LangSmith platform.

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

const chat = new ChatOpenAI({ temperature: 0 });
const response = await chat.predict(
  "Translate this sentence from English to French. I love programming."
);
console.log(response);

Logging Traces Outside LangChain

Note: this API is experimental and may change in the future

You can still use the LangSmith development platform without depending on any LangChain code. You can connect either by setting the appropriate environment variables, or by directly specifying the connection information in the RunTree.

1. Copy the environment variables from the Settings Page and add them to your application.

process.env["LANGCHAIN_ENDPOINT"] = "https://api.smith.langchain.com"; // or your own server
process.env["LANGCHAIN_API_KEY"] = "<YOUR-LANGSMITH-API-KEY>";
// process.env["LANGCHAIN_PROJECT"] = "My Project Name"; // Optional: "default" is used if not set

2. Log traces using a RunTree.

A RunTree tracks your application. Each RunTree object is required to have a name and run_type. These and other important attributes are as follows:

• name: string - used to identify the component's purpose
• run_type: string - Currently one of "llm", "chain" or "tool"; more options will be added in the future
• inputs: Record<string, any> - the inputs to the component
• outputs: Optional<Record<string, any>> - the (optional) returned values from the component
• error: Optional<string> - Any error messages that may have arisen during the call

import { RunTree, RunTreeConfig } from "langsmith";

const parentRunConfig: RunTreeConfig = {
  name: "My Chat Bot",
  run_type: "chain",
  inputs: {
    text: "Summarize this morning's meetings.",
  },
  serialized: {}, // Serialized representation of this chain
  // project_name: "Defaults to the LANGCHAIN_PROJECT env var"
  // apiUrl: "Defaults to the LANGCHAIN_ENDPOINT env var"
  // apiKey: "Defaults to the LANGCHAIN_API_KEY env var"
};

const parentRun = new RunTree(parentRunConfig);

await parentRun.postRun();

const childLlmRun = await parentRun.createChild({
  name: "My Proprietary LLM",
  run_type: "llm",
  inputs: {
    prompts: [
      "You are an AI Assistant. The time is XYZ." +
        " Summarize this morning's meetings.",
    ],
  },
});

await childLlmRun.postRun();

await childLlmRun.end({
  outputs: {
    generations: [
      "I should use the transcript_loader tool" +
        " to fetch meeting_transcripts from XYZ",
    ],
  },
});

await childLlmRun.patchRun();

const childToolRun = await parentRun.createChild({
  name: "transcript_loader",
  run_type: "tool",
  inputs: {
    date: "XYZ",
    content_type: "meeting_transcripts",
  },
});
await childToolRun.postRun();

await childToolRun.end({
  outputs: {
    meetings: ["Meeting1 notes.."],
  },
});

await childToolRun.patchRun();

const childChainRun = await parentRun.createChild({
  name: "Unreliable Component",
  run_type: "tool",
  inputs: {
    input: "Summarize these notes...",
  },
});

await childChainRun.postRun();

try {
  // .... the component does work
  throw new Error("Something went wrong");
} catch (e) {
  await childChainRun.end({
    error: `I errored again ${e.message}`,
  });
  await childChainRun.patchRun(); 
  throw e;
}

await childChainRun.patchRun();

await parentRun.end({
  outputs: {
    output: ["The meeting notes are as follows:..."],
  },
});

// False directs to not exclude child runs
await parentRun.patchRun();

Create a Dataset from Existing Runs

Once your runs are stored in LangSmith, you can convert them into a dataset. For this example, we will do so using the Client, but you can also do this using the web interface, as explained in the LangSmith docs.

import { Client } from "langsmith/client";
const client = new Client({
  // apiUrl: "https://api.langchain.com", // Defaults to the LANGCHAIN_ENDPOINT env var
  // apiKey: "my_api_key", // Defaults to the LANGCHAIN_API_KEY env var
  /* callerOptions: {
         maxConcurrency?: Infinity; // Maximum number of concurrent requests to make
         maxRetries?: 6; // Maximum number of retries to make
    */
});
const datasetName = "Example Dataset";
// We will only use examples from the top level AgentExecutor run here,
// and exclude runs that errored.
const runs = await client.listRuns({
  projectName: "my_project",
  executionOrder: 1,
  error: false,
});

const dataset = await client.createDataset(datasetName, {
  description: "An example dataset",
});

for (const run of runs) {
  await client.createExample(run.inputs, run.outputs ?? {}, {
    datasetId: dataset.id,
  });
}

Evaluating Runs

Check out the LangSmith Testing & Evaluation dos for up-to-date workflows.

For generating automated feedback on individual runs, you can run evaluations directly using the LangSmith client.

import { StringEvaluator } from "langsmith/evaluation";

function jaccardChars(output: string, answer: string): number {
  const predictionChars = new Set(output.trim().toLowerCase());
  const answerChars = new Set(answer.trim().toLowerCase());
  const intersection = [...predictionChars].filter((x) => answerChars.has(x));
  const union = new Set([...predictionChars, ...answerChars]);
  return intersection.length / union.size;
}

async function grader(config: {
  input: string;
  prediction: string;
  answer?: string;
}): Promise<{ score: number; value: string }> {
  let value: string;
  let score: number;
  if (config.answer === null || config.answer === undefined) {
    value = "AMBIGUOUS";
    score = 0.5;
  } else {
    score = jaccardChars(config.prediction, config.answer);
    value = score > 0.9 ? "CORRECT" : "INCORRECT";
  }
  return { score: score, value: value };
}

const evaluator = new StringEvaluator({
  evaluationName: "Jaccard",
  gradingFunction: grader,
});

const runs = await client.listRuns({
  projectName: "my_project",
  executionOrder: 1,
  error: false,
});

for (const run of runs) {
  client.evaluateRun(run, evaluator);
}

Additional Documentation

To learn more about the LangSmith platform, check out the docs.