There's a good reason that most successful examples of those tools like openspec are to-do apps etc. As soon as the project grows to 'relevant' size of complexity, maintaining specs is just as hard as whatever other methodology offers. Also from my brief attempts - similar to human based coding, we actually do quite well with incomplete specs. So do agents, but they'll shrug at all the implicit things much more than humans do. So you'll see more flip-flopped things you did not specify, and if you nail everything down hard, the specs get unwieldy - large and overly detailed.
That's a rather short-sighted way of putting it. There's no way that the spec is anywhere as unwieldly as the actual code, and the more details, the better. If it gets too large, work on splitting a self-contained subset of it to a separate document.
But also, you don't have to upgrade every iteration. I think it's absolutely worthwhile to step off the hamster wheel every now and then, just work with you head down for a while and come back after a few weeks. One notices that even though the world didn't stop spinning, you didn't get the whiplash of every rotation.
At the end of the day, it doesn’t matter if a cat is black or white so long as it catches mice.
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Ive also found that picking something and learning about it helps me with mental models for picking up other paradigms later, similar to how learning Java doesn’t actually prevent you from say picking up Python or Javascript