LangGraph

LangGraph builds AI agents as graphs: nodes do work, edges decide what happens next, and state persists between steps, so an agent can pause for human approval, recover from failures and pick up where it left off. It's from LangChain but works without it. The library is MIT and ungated.

Run it anywhere Python or JavaScript runs, with a Postgres or SQLite checkpointer for persistence. LangGraph 1.0 shipped in October 2025 as a long-term-support release with a semver promise, so minor upgrades shouldn't break you; the churn now lives in beta features and the wider LangChain ecosystem. Two high-severity auth advisories in the SDK landed in August and September 2026, so stay current.

The money is in LangSmith. Tracing is free for one seat with 5,000 base traces a month; Plus is $39 per seat a month with 10,000 base traces, then $5 per 1,000 more. LangChain's production Agent Server (task queues, cron, streaming endpoints) runs on LangSmith Deployment, metered by compute on Plus, and self-hosting that server requires Enterprise. Solo and small teams: free library plus your own server. Larger teams that want the managed runtime: budget for LangSmith.

The catch: the free path means building your own serving layer. The moment you want LangChain's runtime on your own hardware, you're in an Enterprise sales conversation.