Prompt engineering was the visible phase.
Loop engineering is where AI starts becoming operating infrastructure.
I have seen many teams treat AI as a better input box. Ask better, get better. That works for individual productivity, but it does not change how an organization operates.
A loop is different. It has a goal, enough context, a way to act, a way to evaluate the result, and a rule for what happens next. It may retry, route, ask for help, update memory, or stop. That is why the move from prompting agents to loop engineering matters. It turns AI from a one-off assistant into part of a work system.
The hard part is not making the loop run. The hard part is deciding what the loop is allowed to optimize and where it must stop.
AI transformation begins when the organization designs the loop, not just the prompt.