What is the problem to solve?
Drupal's AJAX system has served us well for over a decade. For over 15 years if you count its predecessors in CTools and AHAH. At the time of its creation, we had to create a custom system, because there weren't existing libraries with the functionality that we needed. It was fun to be at the bleeding edge of integrating AJAX into a server-rendered framework like Drupal.
But now HTMX exists. It's a well designed, well documented, well maintained library that's gaining a lot of traction, and I think it supports pretty much everything that Drupal needs from an AJAX system, including the ability for the response to trigger additional actions, which we can use to implement any of our current custom commands that don't have an already implemented corollary in HTMX. In the long run, I think we'd be well served by moving from our custom AJAX system to a library that an increasing number of developers are gaining familiarity with.
However, I don't think it would be easy to preserve Drupal's current AJAX API and change it to use HTMX under the hood. Instead, I think it would be better to convert usages of AJAX (for example, in Field UI, Layout Builder, Views UI, etc.) to use an HTMX-based API.
This would mean maintaining both Drupal's current AJAX API and a new HTMX API until contrib/custom modules have had sufficient time (possibly several major Drupal versions) to convert their ajax usages to htmx.
Who is this for?
Developers
Result: what will be the outcome?
(Describe the result: how will this improve things for the stated audience(s)?)
How can we know the desired result is achieved
(Usability test, a metric to track, feedback)
