What it is
LangChain makes open-source frameworks for building AI applications and agents: LangChain for quick starts with any model provider, LangGraph for low-level control over agent steps and state, and Deep Agents for long-running tasks. LangSmith, its commercial platform, adds tracing and observability, evaluations, agent deployment, code sandboxes, an LLM gateway, and Fleet, a no-code agent builder.
The frameworks are free and open source. LangSmith's Developer plan is free for one seat with 5,000 traces a month; Plus costs $39 per seat a month with 10,000 traces, then usage-based charges. It is a code-first toolkit, and its layers of abstraction add a learning curve compared with calling a model API directly.
Best for
- Developers building agents that use any model provider
- Tracing and debugging what an agent did, step by step
- Running evaluations before shipping changes