Peter Steinberger put it plainly: you shouldn't be prompting coding agents anymore, you should be designing loops that prompt your agents. Boris Cherny, who leads Claude Code at Anthropic, backed it up. He doesn't prompt Claude anymore. He has loops running that prompt Claude. His job is to write loops.
Neither one is lying. The sentence just travels a lot better than the detail it leaves out.
What actually changes
Prompt engineering puts a human in the loop at every step. Write a prompt, read the output, write the next prompt. The agent only moves when you push it.
Loop engineering flips that. You set a goal once. A trigger fires. The agent acts, checks whether the goal was met, and keeps going until it is. You show up at the end to review.
