Tracing Quick Start

You can get started with LangSmith tracing using either LangChain, the Python SDK, the TypeScript SDK, or the API. The following sections provide a quick start guide for each of these options.

First, create an API key by navigating to the settings page, then follow the instructions below:

Python SDK

1. Install the LangSmith library

Start by installing the Python library.

Shell

pip install langsmith

2. Configure your environment

Shell

export LANGCHAIN_TRACING_V2=true
export LANGCHAIN_API_KEY=<your-api-key>

# The below examples use the OpenAI API, though it's not necessary in general
export OPENAI_API_KEY=<your-openai-api-key>

3. Log a trace

We provide multiple ways to log traces to LangSmith. Below, we'll highlight how to use our simple @traceable decorator. See more in the Integrations section.

import openai
from langsmith.wrappers import wrap_openai
from langsmith import traceable

# Auto-trace LLM calls in-context
client = wrap_openai(openai.Client())

@traceable # Auto-trace this function
def pipeline(user_input: str):
    result = client.chat.completions.create(
        messages=[{"role": "user", "content": user_input}],
        model="gpt-4o-mini"
    )
    return result.choices[0].message.content

pipeline("Hello, world!")
# Out:  Hello there! How can I assist you today?

4. View the trace

By default, the trace will be logged to the project with the name default. You can change the project you log to by following the instructions

here

. An example of a trace logged using the above code is made public and can be viewed here .

TypeScript SDK

1. Install the LangSmith library

Start by installing the TypeScript library.

npm

npm install langsmith

yarn

yarn add langsmith

pnpm

pnpm add langsmith

bun

bun add langsmith

2. Configure your environment

Shell

export LANGCHAIN_TRACING_V2=true
export LANGCHAIN_API_KEY=<your-api-key>

# The below examples use the OpenAI API, though it's not necessary in general
export OPENAI_API_KEY=<your-openai-api-key>

3. Log a Trace

We provide multiple ways to log traces to LangSmith. Below, we'll highlight how to use our simple traceable higher order function (HOF). See more in the Integrations section.

import { OpenAI } from "openai";
import { traceable } from "langsmith/traceable";
import { wrapOpenAI } from "langsmith/wrappers";

// Auto-trace LLM calls in-context
const client = wrapOpenAI(new OpenAI());
// Auto-trace this function
const pipeline = traceable(async (user_input) => {
    const result = await client.chat.completions.create({
        messages: [{ role: "user", content: user_input }],
        model: "gpt-4o-mini",
    });
    return result.choices[0].message.content;
});

await pipeline("Hello, world!")
// Out: Hello there! How can I assist you today?

4. View the trace

By default, the trace will be logged to the project with the name default. You can change the project you log to by following the instructions

here

. An example of a trace logged using the above code is made public and can be viewed here .

LangChain

1. Install or upgrade LangChain

pip

pip install langchain_openai langchain_core

yarn

yarn add @langchain/openai @langchain/core

npm

npm install @langchain/openai @langchain/core

pnpm

pnpm add @langchain/openai @langchain/core

2. Configure your environment

Shell

export LANGCHAIN_TRACING_V2=true
export LANGCHAIN_API_KEY=<your-api-key>

# The below examples use the OpenAI API, though it's not necessary in general
export OPENAI_API_KEY=<your-openai-api-key>

3. Log a trace

No extra code is needed to log a trace to LangSmith. Just run your LangChain code as you normally would.

Python

from langchain_openai import ChatOpenAI
from langchain_core.prompts import ChatPromptTemplate
from langchain_core.output_parsers import StrOutputParser

prompt = ChatPromptTemplate.from_messages([
    ("system", "You are a helpful assistant. Please respond to the user's request only based on the given context."),
    ("user", "Question: {question}\nContext: {context}")
])
model = ChatOpenAI(model="gpt-4o-mini")
output_parser = StrOutputParser()

chain = prompt | model | output_parser

question = "Can you summarize this morning's meetings?"
context = "During this morning's meeting, we solved all world conflict."
chain.invoke({"question": question, "context": context})

TypeScript

import { ChatOpenAI } from "@langchain/openai";
import { ChatPromptTemplate } from "@langchain/core/prompts";
import { StringOutputParser } from "@langchain/core/output_parsers";

const prompt = ChatPromptTemplate.fromMessages([
  ["system", "You are a helpful assistant. Please respond to the user's request only based on the given context."],
  ["user", "Question: {question}\nContext: {context}"],
]);
const model = new ChatOpenAI({ modelName: "gpt-4o-mini" });
const outputParser = new StringOutputParser();

const chain = prompt.pipe(model).pipe(outputParser);

const question = "Can you summarize this morning's meetings?"
const context = "During this morning's meeting, we solved all world conflict."
await chain.invoke({ question: question, context: context });

4. View the trace

By default, the trace will be logged to the project with the name default. You can change the project you log to by following the instructions

here

. An example of a trace logged using the above code is made public and can be viewed here .

API

1. Log a trace

Log a trace using the LangSmith API.

Here, we'll show you to use the requests library in Python to log a trace, but you can use any HTTP client in any language.

import openai
import requests
from datetime import datetime
from uuid import uuid4

def post_run(run_id, name, run_type, inputs, parent_id=None):
    """Function to post a new run to the API."""
    data = {
        "id": run_id.hex,
        "name": name,
        "run_type": run_type,
        "inputs": inputs,
        "start_time": datetime.utcnow().isoformat(),
    }
    if parent_id:
        data["parent_run_id"] = parent_id.hex
    requests.post(
        "https://api.smith.langchain.com/runs",
        json=data,
        headers=headers
    )

def patch_run(run_id, outputs):
    """Function to patch a run with outputs."""
    requests.patch(
        f"https://api.smith.langchain.com/runs/{run_id}",
        json={
            "outputs": outputs,
            "end_time": datetime.utcnow().isoformat(),
        },
        headers=headers,
    )

# Send your API Key in the request headers
headers = {"x-api-key": "<YOUR API KEY>"}

# This can be a user input to your app
question = "Can you summarize this morning's meetings?"

# This can be retrieved in a retrieval step
context = "During this morning's meeting, we solved all world conflict."
messages = [
    {"role": "system", "content": "You are a helpful assistant. Please respond to the user's request only based on the given context."},
    {"role": "user", "content": f"Question: {question}\nContext: {context}"}
]

# Create parent run
parent_run_id = uuid4()
post_run(parent_run_id, "Chat Pipeline", "chain", {"question": question})

# Create child run
child_run_id = uuid4()
post_run(child_run_id, "OpenAI Call", "llm", {"messages": messages}, parent_run_id)

# Generate a completion
client = openai.Client()
chat_completion = client.chat.completions.create(model="gpt-4o-mini", messages=messages)

# End runs
patch_run(child_run_id, chat_completion.dict())
patch_run(parent_run_id, {"answer": chat_completion.choices[0].message.content})

2. View the trace

By default, the trace will be logged to the project with the name default. You can change the project you log to by following the instructions

here

. An example of a trace logged using the above code is made public and can be viewed here .