It's a nice observation that Spec-Driven Development essentially implements the waterfall model.

Personally, I tried SDD, consciously trying to like it, but gave up. I find writing specs much harder than writing code, especially when trying to express the finer points of a project. And of course, there is also that personal preference: I like writing code, much more than text. Yes, there are times where I shout "Do What I Mean, not what I say!", but these are mostly learning opportunities.

You can do SDD in waterfall or Agile. The interaction I’m having with users right now is that the feedback and iterations are happening within hours or days instead of the usual 1-2 week sprint length. In my case SDD is enabling my team to be hyper-agile.

I have no idea how to reconcile sdd and waterfall. With SDD you’re working per feature, right? Waterfall is speccing the entire project upfront and with a strong force against any changes as you go before a final delivery.