LangSmith is the production monitoring and debugging layer for applications built with LangChain, LangGraph, or any LLM framework. It provides trace-level visibility into agent runs, automated evaluations, custom dashboards, and dataset management for regression testing. Developers use it to diagnose agent failures, measure prompt quality, and track token costs. It also includes managed LangGraph deployment (LangSmith Platform), removing the need for self-hosted agent infrastructure. Key features: - Distributed tracing for LLM calls, tool use, and agent steps - Automated evaluation and LLM-as-judge scoring - Dataset and prompt versioning for regression testing - Custom dashboards and cost tracking per model call - Managed LangGraph deployment (1 free dev deployment included on Plus) - 400-day trace retention on extended storage add-on
Developer (Free): 5,000 traces/month, 14-day retention, 1 seat. Plus: $39/seat/month, 10,000 base traces, overage $2.50/1,000 traces. Enterprise: custom pricing.