# LangSmith

> LangChain freemium obs/eval/deploy — free Developer 5k traces/mo

**Category:** AI Agents  
**Pricing:** freemium  
**URL:** https://www.langchain.com/langsmith  
**GitHub:** https://github.com/langchain-ai/langsmith-python  
**Added:** 2026-09-29

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## The Hook

LangSmith is LangChain’s agent observability, evaluation, and deployment platform — start on the free Developer seat, then pay as traces grow.

## What's Good

Freemium (docs.smith.langchain.com / langchain.com/langsmith). Tracing, evals, prompt hubs, and deployment hooks wired for LangChain/LangGraph (and broader OpenTelemetry-style ingest). Developer plan: $0/seat with ~5k base traces/mo then pay-as-you-go; Plus/Enterprise for teams. SDKs are MIT: Python at langchain-ai/langsmith-python and JS/TS at langchain-ai/langsmith-javascript (both moved out of the langsmith-sdk repo, archived on 16 Oct 2026).

## The Catch

The product is hosted freemium (self-host exists on higher plans) — not a MIT self-host default like Langfuse. Vs Langfuse / Braintrust / Arize Phoenix: LangSmith is the LangChain-native commercial control plane; Langfuse is OSS self-host; Braintrust is eval-first; Phoenix is ELv2 Arize. Free tier is real but thin for busy agent fleets — budget traces early.

## Verdict

Freemium LangChain obs/eval when the LangGraph stack wants one vendor pane — not Langfuse MIT self-host; free until ~5k traces.