LangSmith

LangSmith is a developer platform from LangChain for debugging, testing, evaluating, and monitoring LLM applications. It provides observability into every step of your LLM application, from individual model calls to complex multi-step agent workflows.

Key features include: detailed tracing of LLM calls and chains, prompt versioning and management, evaluation frameworks for testing model outputs, dataset management for regression testing, and production monitoring with performance metrics. LangSmith works with any LLM application, not just those built with LangChain.

For AI engineers, LangSmith addresses critical production concerns: understanding why an agent took certain actions, identifying performance bottlenecks, catching regressions when prompts change, and building confidence through systematic evaluation. It's become an essential tool for teams building serious LLM applications.