Langgraph

This is the framework you reach for when your agent workflow outgrows simple chains and needs real state management. It treats agent coordination as directed graphs with persistent state, conditional branching, and cyclic flows instead of linear pipelines. The killer features are checkpointing (so you can pause and resume), time-travel debugging (replay from any point), and human-in-the-loop gates for approval workflows. You define a state schema with TypedDict, add nodes as functions that update state, then wire them with conditional edges based on outputs. Overkill for basic tasks, but if you're building production multi-agent systems where agents need to loop back, maintain context across sessions, or wait for human input, this is the right tool.