LangSmith

LangSmith is an agent observability platform that traces step-by-step agent execution, monitors latency, cost, and error rates in real time, and automatically surfaces failure patterns and usage insights. It's used by ML/AI engineers, platform engineers, and product managers monitoring AI agents in production, sitting in the post-deployment layer of the AI stack alongside agent frameworks like LangChain and LangGraph. It's delivered as SaaS, with managed cloud, bring-your-own-cloud, and self-hosted options.