LangSmith is a unified observability and evals platform designed to help teams debug, test, and monitor large language model applications and intelligent agents. It captures traces, interactions, and metadata from LLM apps via client SDKs (Python and JavaScript) and surfaces visualizations, evaluations, and diagnostic tools in a web UI. LangSmith works with LangChain-native applications as well as any other LLM application, enabling teams to run automated evaluations, compare model versions, inspect agent decision traces, and detect regressions before and after deployment. Its value lies in centralized debugging, repeatable evals, and monitoring tailored specifically for language-model-driven systems so teams can ship agents and LLM features with confidence.