JJ and GitButler already create and inject this into the commit headers (using the same interoperable reverse-hex format), which is recognized by Gerrit and some forges like Tangled for incremental commit based review.

I doubt that core Git will adopt it anytime soon as it was not discussed at this years contributor summit (last week) and doesn't seem to be a hot topic on the ML.

What I would like to see is support for `git rebase` not dropping it, which is the current main issue. The `git replay` command, as well as commands based on the same sequencing code (`git history` for example) do not drop custom headers like this, so there is partial non-breakage, but several of the other history editing commands do drop custom headers.