(r-a team member here) The progress is in Salsa (the incremental framework we use), not in r-a itself yet. And there is progress but it's not particularly fast, it's also not a priority for the r-a team (though if you want to contribute, you're welcome of course).
You mean progress to make the framework faster itself?
I was asking about something else, i.e. basically saving whatever possible from those expensive computations on disk, so next time it starts, it can spend significantly less time (assuming things didn't change too much). clangd has such feature and it's super helpful.
Or you mean Salsa already supports such persistent caching in some form?
I meant, the progress to make Salsa support persistent caching is not advancing particularly fast. It does exist, but is preliminary.