LangGraph

LangGraph models agent workflows as state machines / graphs — explicit transitions, persistable state, and human-in-the-loop checkpoints at any node. It's the serious choice when production reliability matters more than developer ergonomics.

The killer features are built-in checkpoint persistence (resume from any point after a crash), human-in-the-loop pauses (route to a person for approval before sensitive actions), and tight integration with LangSmith for observability. For agents running unsupervised under SLA, these aren't optional.

The learning curve is real. Verbose to set up compared to CrewAI, and the documentation expects you to think in graph terms. The LangGraph Platform handles hosting and gives you a managed runtime if you don't want to operate the orchestration yourself.