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LangSmith 101

A practical guide series for learning LangSmith - the platform that lets you see exactly what your LLM app did, test it against real examples instead of vibes, and fix a bad prompt without redeploying. Written by people who build agents for a living.

Foundations → Practitioner · ~30 minutes total
1 trace app call LLM run Tool run Project trace Dataset + eval

One request in your app becomes one trace in LangSmith - every LLM call, tool call, and retriever step nested inside it.

FOUNDATIONS

Start Here

Never opened LangSmith, or opened it once and got lost? These two guides get you oriented.

What Is LangSmith? (And Why Observability Matters)

The plain-English version: what problem it solves, how it relates to LangChain and LangGraph, and why "it worked when I tested it" isn't good enough.

Foundations 5 min read

Core Concepts: Traces, Runs & Projects

Three ideas that cover almost everything - once these click, the whole dashboard makes sense.

Foundations 6 min read
HANDS-ON

Build Something

Time to see your own app's traces show up, not just read about it.

Setting Up Tracing In Your App

A hands-on walkthrough - API key, environment variables, the @traceable decorator, and your first trace.

Hands-On 7 min read

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ADVANCED

Make It Production-Ready

The two things that separate "I glanced at some traces" from an app you'd actually trust in production.

Evaluations & Datasets: Testing LLM Apps On Purpose

Turning real traces into a test suite, and how LLM-as-judge evaluators score things a plain assertion can't.

Advanced 7 min read

Prompt Playground & Prompt Hub

Iterating on prompts without redeploying code, and how versioned commits keep production from breaking mid-edit.

Advanced 6 min read