It's not always what the nerds want to do though: I know of what the insides used to look like in one of those on the list, and things were very custom, because some early technical decisions were outright landmines that were too expensive to move away from. So having custom harnesses to actually survive that codebase I remember seems like a baseline to get reasonable turnaround of AI helpers. The company had done cowboy development for way too long, and solved too many problems by creating bigger, more custom problems.

So don't assume it's all nerds having fun. Now, is it what the future will look like for everyone? I don't think so, but that's because I expect AI is bringing us a more unified dev experience, with more developers than even Google has. This will make general programming harnesses very good, quite fast, solely because said harnesses can be differentiators in the AI race. So we are seeing some of the largest companies inthe world, with the largest research budgets, dedicating more money to the dev experience of their product than almost anyone else does.