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LangSmith

LangChain's platform for LLM tracing, datasets, evaluation, and experiment tracking.

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About

LangSmith is LangChain's commercial platform for developing LLM apps: end-to-end tracing of chains and agents, dataset curation, LLM-as-judge evaluations, and prompt versioning — deeply integrated with LangChain and LangGraph. The SDKs (langchain-ai/langsmith-sdk) are MIT-licensed; the platform itself is closed SaaS.

Free tier: 5,000 traces/month. It is the default observability choice if you already build on LangChain; framework-agnostic teams often prefer Langfuse or OpenLIT.

What it can do

  • Automatic tracing for LangChain/LangGraph apps
  • Datasets and LLM-as-judge evaluations
  • Prompt versioning and playground
  • Experiment tracking and comparison
  • Framework-agnostic ingestion API

Setup

  1. Sign up at smith.langchain.com.
  2. Install the SDK: pip install langsmith (or the JS SDK).
  3. Set LANGSMITH_API_KEY and enable tracing (LANGSMITH_TRACING=true).
  4. Run your LangChain/LangGraph app — traces appear automatically.
  5. Build datasets and evals in the web UI.

Prerequisites

LangSmith account (free tier: 5k traces/mo); API key.

Use cases

codeautomationdata

Works with

Generic APIAny agent (.md)

Trust score — 8/10

/10 trustVerified

Scored 8/10 (verified tier). LangChain's official platform with an MIT SDK, active development (100 releases/12mo), and deep framework integration verified via docs. Docked because the platform is closed SaaS (the SDK repo is a proxy metric) and it is strongest inside the LangChain ecosystem — less compelling outside it. Verified tier on docs + SDK + independent coverage.

★ 1,076 GitHub stars

How the trust score is built

Full methodology →
Adoption · stars/downloads, log-scaled vs peers
6.0/10
Maintenance · recency, releases, issue load
8.2/10
Openness · license + docs
9.7/10
Manual review · sanity read + red-flag check
9.0/10
  • · 1,076 GitHub stars (log-scaled vs catalog peers)
  • · last push 1d ago; 100 releases/12mo; 250 open issues
  • · manual review: LangChain's official platform; deep LangGraph integration; SDK metrics are a proxy for the SaaS platform; license: MIT (SDK; platform is closed SaaS)

Sources

Every fact above was checked against these sources. Where a claim comes from the provider and couldn't be independently verified, the text says so.