Comment by CuriouslyC

AI loves waterfall because every time you insert yourself in the agentic coding loop you reduce the velocity of the system, and if the system blocks on your input the reduction can be pretty epic. Beyond that, AI has myopia, and if you tell it to implement something without a larger framework it understands how to slot it into, it'll put it somewhere that makes no sense, duplicate code, make incompatible interfaces, etc. It's much more efficient to just have the system outlined clearly from the get-go, and this also helps because you can generate E2E tests for validation up front to ensure the features really are valid and working.