Prompt chains are easy to demo and hard to operate. Production workflows need explicit state transitions, tool boundaries, and failure paths that engineering and operations teams can inspect.
Graph-based agent design helps separate planning, retrieval, execution, evaluation, and escalation into nodes with clear responsibilities. That makes testing and observability far more practical.
The most valuable guardrail is often not a prompt. It is a deterministic gate that checks whether the agent is allowed to take a particular action in a particular business context.