On the other hand if you're a business with 50k employees and you have to pay $10/seat for something that's a much more compelling case to build in house (but then it always was). So maybe with vibe coding it drops the cutoff to a lower number?

Businesses are more likely to build than buy, yes, but as we know from "Theory of the Firm" there are limits to this, it's not going to be correct to build _everything_.

So I mainly expect it to change what type of software gets sold, not the fact that it gets sold in the first place.

As a "10x" engineer I am not excited. I'm still working on projects with agents getting more done than ever, but I feel like software engineers has lost its soul for me. I don't really feel like I have a true understanding of anything anymore, I basically just spend all day making a set of small decisions or adjusting prompts to guide the agents down the good path. It used to be that I could close my eyes and visualize the code that I worked on--if there was a bug report I could often use that map to immediately know what the cause likely was. In meetings I could intelligently discuss various tradeoffs without having to refer back to anything. Now if someone asks me a technical question I basically have to forward it to the agent first, then interpret their response in light of my experience.

Backend code I'm fairly comfortable if the tests are good that it works correctly. It's a much more constrained environment. Obviously there can be things like performance issues that creep in or problems when it mocks too much of the environment.

Meanwhile frontend code I have to consider different browsers, screen sizes, a11y issues, and so on, which agents can certainly do but you have to be fairly explicit about it, and they don't always make the best tradeoffs.

This is partially a feature. Conflict and disagreement tends to produce better decisions in the end.

I agree we will only see it in hindsight, but I think that's always the case with any technology. It seems worse until it's suddenly better. I don't think it matters to argue the exact moment though. For example when did cars become clearly better than horses? No one cares about the exact date.

Architect a system for long-term maintainability.

Encode the right amount of business logic into tests, without being overly strict.

Models seem quite poor at all of these IME. Essentially any time there are qualitative tradeoffs they are not great at making them.