Most of these also apply to HTMX it seems.

I think a bigger difference is that TwinSpark seems to have some integrated DOM manipulation, so it's a bit bigger in scope and less opinionated?

HTMX on its own is great as long as you stay within its philosophy of rendering things on the server.

But most UIs I write need - as in it's optimal for UX and performance or out of necessity because it's talking to a third party - at least _some_ parts to be fully client side rendered.

I personally found that combining HTMX with something like lit-html is kind of the sweet spot for a lot of projects assuming full-stack development. These are very small/light libs that cover a ton of ground with minimal surprises and very good performance per default. The _only_ downside is that you don't get isomorphic rendering code but I happily pay that relatively small cost for having such a simple dependency graph.