Craft

Since Opus 4.5 arrived late last year, I’ve thought the future of software engineering would be engineers working with AI agents in natural language. The underlying code would increasingly be written and understood primarily by AI. DHH describes that shift in his Rails World opening keynote. Describing what the software should do becomes a larger part of the work, while agents handle more of the implementation.

That could eventually give us entirely new programming languages designed around agents. Rust already hints at the shift. A language can be unpleasant for a human to write and still be a great choice for the resulting software. DHH’s experience with Rust puts that tradeoff into practice: agents handle the code, while the product benefits from its performance and small executables.

I think this leads to better software. More of the effort can go toward making the product work well, including improvements that previously cost too much to justify. Engineers still have to figure out what to build and how it should work, then judge whether the result delivers that experience. Those decisions remain human work even as less of the implementation requires human hands.

Taste becomes even more important when almost any feature is within reach. Being able to build everything makes it easier to produce a product that tries to do everything, and those products tend to be poor. Good products have focus. It takes judgment to choose what belongs and discipline to leave the rest out, even when adding it is cheap.

The first 90 percent of the code accounts for the first 90 percent of the development time. The remaining 10 percent of the code accounts for the other 90 percent of the development time.

— Tom Cargill, Bell Labs, via the Ninety-ninety rule

This rule is so true it barely reads like a joke. Anyone who has shipped software has watched a project reach “almost done” and then stay there while the real work finally shows itself.

Not even AI can break it. It changes how quickly we can get through the first 90 percent: scaffolding, boilerplate, tests, happy paths, and enough of the shape of the thing that it feels almost done.

But the second 90 percent still requires human judgment. Someone has to know which rough edges matter, which tradeoffs are acceptable, and when the product is actually right.

Morgan Wallen at Death Valley on Saturday. What I kept thinking about was how plainly he loves the work itself: making the songs, playing them, being up there. That’s the part you can’t manufacture, and from the stands it was the most obvious thing in the place.