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LangSmith

APIyesFREEyesDOCS4/5
LA7.1#30of 74
outWeb

Ranked in AI agent platforms·Free plan·paid from $39/mo

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About

LangSmith is a commercial platform for building, testing, deploying, monitoring, and improving AI agents. It supports offline evaluation against curated datasets and real-time evaluation of production interactions. Teams can use human review, heuristic checks, LLM-as-judge scoring, pairwise comparisons, or custom evaluators written in Python or TypeScript. Annotation queues route runs to subject-matter experts, whose feedback can calibrate evaluations, prompts, or datasets. The Playground supports prompt experiments and output comparisons across versions or model providers; LangSmith chat can improve prompts. Observability includes agent traces, cost tracking, trajectory monitoring, online evaluations, and webhook or PagerDuty alerts. It accepts traces by SDK or API from LangGraph, custom Python, and other stacks, and lists Python, TypeScript, Go, and Java SDKs plus OpenTelemetry. Evaluations can integrate with pytest, Vitest, and GitHub workflows. Developer is free at 0.00 USD per month; Plus costs 39.00 USD per month. Base traces retain for 14 days, while extended traces retain for 180 days at additional cost.

Who it is for

It suits teams building AI agents that need evaluation and observability across development and production. Its SDK and API support teams working across different application stacks.

What is good

  • Offline and real-time evaluation options
  • Custom evaluators can use Python or TypeScript
  • Tracing SDKs include Python, TypeScript, Go, and Java
  • Developer plan is free

What to know first

  • Base traces retain for 14 days
  • Extended retention costs extra
  • Plus costs 39.00 USD per month

Verdict

LangSmith brings agent evaluation, prompt work, and observability into one platform, with support for varied stacks and CI workflows. Teams should account for trace retention limits and usage-based charges beyond included traces.

Compared on AI agent platforms

Free plan
Yeslangchain.com

Facts

Purpose
LangSmith is a commercial agent engineering platform for building, testing, deploying, monitoring, and improving AI agents.langchain.com · 5 Oct 2026
Evaluation
It supports offline evaluations on curated datasets and online evaluations that score production interactions in real time.langchain.com · 5 Oct 2026
Evaluators
Its evaluation framework supports human review, heuristic checks, LLM-as-judge evaluators, pairwise comparisons, and custom evaluators in Python or TypeScript.langchain.com · 5 Oct 2026
Human feedback
Annotation queues let teams assign runs to subject-matter experts and use feedback to calibrate evaluations, improve prompts, or augment datasets.langchain.com · 5 Oct 2026
Prompt tools
The Playground supports experimenting with prompts and comparing outputs across prompt versions or model providers, and LangSmith chat can auto-improve prompts.langchain.com · 5 Oct 2026
Integrations
The evaluation page says LangSmith integrates with pytest, Vitest, and GitHub workflows for evaluations in CI/CD pipelines.langchain.com · 5 Oct 2026
Framework support
LangSmith is framework-agnostic and accepts traces through its SDK or API from LangGraph, custom Python, or other application stacks.langchain.com · 5 Oct 2026
Observability
Its observability features include agent tracing, cost tracking, online LLM-as-judge and code evaluations, trajectory monitoring, and webhook or PagerDuty alerts.langchain.com · 5 Oct 2026
SDKs
The observability page lists SDKs for Python, TypeScript, Go, and Java, plus native tracing for popular agent frameworks and OpenTelemetry.langchain.com · 5 Oct 2026
Hosting
The pricing page lists Cloud hosting for Developer and Plus, with Cloud, Hybrid, or Self-Hosted options for Enterprise.langchain.com · 5 Oct 2026
Security
The LangSmith Trust Center lists SOC 2 Type II, ISO 27001:2022, GDPR, and HIPAA under compliance.trust.langchain.com · 5 Oct 2026
Data use
The pricing page says LangSmith does not use customer data to train models and that traces, prompts, and outputs remain private to the organization.langchain.com · 5 Oct 2026
Retention limit
The pricing page states base traces have 14-day retention and extended traces have 180-day retention, with an additional fee to upgrade base traces.langchain.com · 5 Oct 2026
Support
The Developer plan includes community support, and the Enterprise plan lists a support SLA.langchain.com · 5 Oct 2026

Company

Founded
2023langchain.com · 28 Sept 2026
Headquarters
San Francisco, California, United Stateslangchain.com · 28 Sept 2026

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