Marcus Horndt

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Why I build agent-first

Agent-first means two things: AI as my building partner, and AI as the primary user of what I ship.

I build agent-first now. That means two things: AI is my partner while I build, and AI lives inside the things I build.

The first part changed how much one person can do. A solo founder with good agents is not one person anymore. The grunt work, the research, the boilerplate, the first draft of almost anything: that can be delegated, which frees the hours for the parts where human judgment actually decides the outcome. I do not automate to remove myself; I automate to spend myself where it counts.

The second part is the bigger bet. Most software was designed for humans to click through. I think the next wave is software designed for an agent to operate on your behalf, with the human steering rather than typing. So when I build, I ask early: what would this look like if an agent were the primary user, and the person was the one giving direction and approving the result?

That question changes the design. It pushes you toward clear structure, honest interfaces, and actions a machine can take safely and reversibly. It rewards systems that explain themselves.

There is a rule I hold onto through all of it: never trade quality for automation. If letting the machine do a step makes the result worse, that step is not ready to be automated yet. Speed is worth a lot. It is not worth shipping something I would be embarrassed to use myself.