That means new slots and support windows are out for now. I’ll write up a separate motivation for them later :)
I’m still leaning toward a new version-checking slot, especially if it would mean that extension “.so” filenames can keep using just abi3 for abi3t & abi3+abi3t.
From your post, I can’t tell whether you think there are other ways of doing things more minimally than what I proposed. If there are, let me know.
It seems that abi3t is the best name for this, in a world where abi3 and this need to coexist for a while. When phase out the t everywhere else and stop supporting the unadorned abi3, it’ll be just another naming wart for abi4 to fix.