LangGraph

LangGraph defines AI agent workflows as graphs, where nodes are processing steps and edges are conditional transitions. Each node is a step (call the LLM, run a tool, check a condition), and edges define what happens next.

The graph model matters because real agent workflows aren't linear. An agent might need to: research, then decide if it has enough info, loop back to research if not, then draft a response, then review it, then either revise or submit. LangGraph makes these branching, looping workflows explicit and debuggable.

It builds on LangChain but works independently. Supports any LLM provider. State management is built in: each graph execution has persistent state that nodes can read and write. Human-in-the-loop patterns (pause execution, wait for approval, resume) are first-class features. The star velocity tells you where the market is heading. Agent frameworks are the hottest category in open source AI right now.

The catch: the abstraction adds complexity. For simple "call an LLM with tools" flows, LangGraph is overkill. The OpenAI or Anthropic SDKs handle that directly. The LangChain ecosystem moves fast and breaks things; APIs change between versions. And debugging graph execution requires understanding the framework's internals, not just your business logic.