A vibecoded prototype isn’t just a rough sketch. It’s a working, interactive specification, and one heck of a starting point.
My colleague built a one-page static prototype in Claude - fast, imperfect, but good enough to demonstrate her idea. I took this prototype and used it as the brief for an agent-driven build: directing a high-effort thinking agent swarm to break it into vertical slices, write implementation plans for each, then cross-reference them to make sure approaches were aligned.
Once I was satisfied that the plans were sound, I told the agent to go forth and implement - then left it alone.
The shell of the application came together quickly while I worked on other things, and while the actual implementation diverged from the prototype in a handful of small ways, it was fine - the groundwork was solid - I could refine the details as I built out the rest of the functionality.
Agents tend toward completeness. They’ll solve for edge cases you didn’t ask for, and often they arrive at solutions that - while technically correct - are much more complicated than the problem warrants.
Agent for Velocity, Me for Judgement
So, next came an intense collaborative phase working through the slices closely: simplifying, correcting, improving.
The responsibility split felt right. Agent for velocity. Me for judgement.
At the end of a week, I had a solid version of my colleague’s idea ready to hand over to the team for iteration, and I had learned two valuable lessons:
Two Lessons
First: there’s really no need to write functional specs anymore. Just build them instead. A few hours with an agent can produce superb, interactive results that demonstrate an idea far better than words.
Second: upfront cross-referencing pays for itself immediately. Before starting development the agent checked all of the sliced implementation plans against each other. Conflicts surfaced early, and a few brainstorming sessions at the beginning meant that approaches were aligned throughout.
Rapid prototyping made the idea understandable.
Careful planning made the plan coherent and consistent.
Collaboration made the product solid.
I wonder how many good ideas are still stuck in a Word document.
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