> no good story for what happens when one component in a tree needs to update another component in the tree

HTMX has a decent answer to this. Any component can target replacement for any other component. So if the state of everything on the page changes then re-render the whole page, even if what the user clicked on is a button heavily nested.

> it's impossible to implement "optimistic UI," ... hurting the user experience

Do we actually need optimistic UI? Some apps need to work in offline mode sure, like offline maps or audiobooks or something. The HTMX author agrees, this is not the solution for that. Most of the stuff I have worked on though ... is useless without an internet connection.

In the case of "useless without internet connection" do we really need optimistic UI. The actual experience of htmx is incredibly fast. There is no overhead of all the SPA stuff. No virtual dom, hardly any js. It's basically the speed of the network. In my limited practice I've actually felt the need to add delays because the update happens _too fast_.

I'm still evaluating htmx but not for any of the reasons you've stated. My biggest concern is ... do I want my api to talk in html?