AI Coding Agents Shift From Prompt Engineering to Loop Engineering for Runtime Verification

AI coding agents from Greptile, Cursor, and Devin have reached a consensus: agents should execute their own code. The industry is moving rapidly toward runtime verification as the key to shipping agent code at scale, according to a report from The New Stack.

This shift marks a departure from traditional prompt engineering. Boris Cherny, creator of Claude Code, told CNBC that he no longer writes his own AI prompts. Instead, he relies on loops where an agent prompts Claude itself. "It's an agent that prompts Claude," Cherny said. "I don't write the prompt anymore. Claude writes the prompt, and now I'm talking to that new Claude that is kind of coordinating."

Loop Engineering Replaces Prompt Engineering

The new paradigm, dubbed "loop engineering," focuses on designing feedback loops that allow agents to iteratively refine their outputs. Cherny described loops as among the work he would be proudest of in a decade. The approach reduces the need for manual prompt crafting and instead lets agents self-prompt through repeated execution cycles.

• Greptile, Cursor, and Devin all now support agent code execution as a core feature.
• Runtime verification ensures that agent-generated code behaves correctly before deployment.
• The shift reduces reliance on static prompts and moves toward dynamic, self-correcting agents.
• Loop engineering allows agents to coordinate multiple steps without human intervention.

Implications for Developer Workflows

The move to runtime verification addresses a critical gap: ensuring that agent code runs safely and reliably at scale. Without verification, agents could produce code that passes static checks but fails in production. By executing code in sandboxed environments, tools like Greptile and Cursor can catch errors early. Devin, an autonomous coding agent, uses similar runtime checks to validate its outputs.

What comes next is a race to standardize runtime verification across the industry. As more developers adopt agent-driven workflows, the ability to trust agent output will become a competitive differentiator. Loop engineering may soon become as fundamental as prompt engineering was in 2023, reshaping how developers interact with AI coding assistants.