LangSmith
LangSmith is a unified DevOps platform for developing, collaborating, testing, deploying, and monitoring LLM applications.
LangSmith, part of LangChain, is a platform that provides tools for debugging, testing, evaluating, and managing prompts for LLM applications. It offers functionalities like nested traces for debugging, dataset curation for testing, application-level usage stats for monitoring, and a prompt playground for managing prompts. LangSmith facilitates native collaboration, integrates with LangChain, and promotes best practices for LLM application development. It's designed to transform LLM applications into enterprise-ready products, emphasizing observability and testing in complex LLM apps
Pricing: Free and monthly subscriptions.
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What is LangSmith?
LangSmith is a platform built by LangChain for developing, debugging, evaluating, and monitoring LLM applications and AI agents. While it has deep integration with LangChain and LangGraph, it works with any LLM stack through SDKs for Python, TypeScript, Go, and Java, plus OpenTelemetry support.
How It Works
LangSmith captures structured traces of every step in an AI agent or LLM application run. Each trace shows the exact prompts sent, model responses, tool calls, retrieval steps, token usage, latency, and errors. Teams use this data to debug failures, then build evaluation datasets to measure quality before deploying changes. In production, dashboards track cost, latency, error rates, and quality scores with native alerting.
Key Features
Tracing provides step-by-step visibility into agent runs with an AI assistant ("Polly") that summarizes large traces and pinpoints problems. The evaluation system supports LLM-as-judge, code-based evaluators, and human annotation queues with side-by-side comparison of prompt and model versions. Prompt Hub handles versioned prompt management. For LangGraph users, LangSmith also offers a managed deployment runtime for shipping agents as production APIs.
Pricing
The free Developer plan includes 5,000 traces per month with 14-day retention and 1 seat. The Plus plan costs $39 per seat per month with 10,000 traces and 400-day extended retention. Additional traces cost $2.50-$5.00 per 1,000 depending on retention. Enterprise plans include self-hosting, custom limits, and dedicated support. LangSmith holds SOC 2 Type 2, HIPAA, and GDPR compliance certifications.
Who Should Use It
LangSmith is the strongest choice for teams already using LangChain or LangGraph, where the integration is deepest and includes deployment capabilities. Teams using other frameworks can still use LangSmith for tracing and evaluation, but may want to compare with open-source alternatives like Langfuse that offer more generous free tiers and self-hosting options.
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