Vibe engineering
I feel like vibe coding is pretty well established now as covering the fast, loose and irresponsible way of building software with AI—entirely prompt-driven, and with no attention paid to how the code actually works. This leaves us with a terminology gap: what should we call the other end of the spectrum, where seasoned professionals accelerate their work with LLMs while staying proudly and confidently accountable for the software they produce?
I propose we call this vibe engineering, with my tongue only partially in my cheek.
One of the lesser spoken truths of working productively with LLMs as a software engineer on non-toy-projects is that it’s difficult. There’s a lot of depth to understanding how to use the tools, there are plenty of traps to avoid, and the pace at which they can churn out working code raises the bar for what the human participant can and should be contributing.
The rise of coding agents—tools like Claude Code (released February 2025), OpenAI’s Codex CLI (April) and Gemini CLI (June) that can iterate on code, actively testing and modifying it until it achieves a specified goal, has dramatically increased the usefulness of LLMs for real-world coding problems.
I’m increasingly hearing from experienced, credible software engineers who are running multiple copies of agents at once, tackling several problems in parallel and expanding the scope of what they can take on. I was skeptical of this at first but I’ve started running multiple agents myself now and it’s surprisingly effective, if mentally exhausting!
This feels very different from classic vibe coding, where I outsource a simple, low-stakes task to an LLM and accept the result if it appears to work. Most of my tools.simonwillison.net collection (previously) were built like that. Iterating with coding agents to produce production-quality code that I’m confident I can maintain in the future feels like a different process entirely.
It’s also become clear to me that LLMs actively reward existing top tier software engineering practices:
Automated testing . If your project has a robust, comprehensive and stable test suite agentic coding tools can fly with it. Without tests? Your agent might claim something works without having actually tested it at all, plus any new change could break an unrelated feature without you realizing it. Test-first development is particularly effective with agents that can iterate in a loop.
. If your project has a robust, comprehensive and stable test suite agentic coding tools can fly with it. Without tests? Your agent might claim something works without having actually tested it at all, plus any new change could break an unrelated feature without you realizing it. Test-first development is particularly effective with agents that can iterate in a loop. Planning in advance . Sitting down to hack something together goes much better if you start with a high level plan. Working with an agent makes this even more important—you can iterate on the plan first, then hand it off to the agent to write the code.
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