That's so cool! It definitely needs explaining and showing off!

I expected Alice to have to notice that a fork had happened, somehow, then copy her local Test.txt elsewhere so it didn't get overwritten, then pull, then use some diff app like kdiff3 to compare the two versions...

but all that happens is that fossil adds MERGE CONFLICT to the file in the problem areas, so she can search for those and edit in just the one file.

Checked-in binaries are, I guess, a whole different problem?

I need to try it again to make sure I've got it: I merged before pulling, which may have made it so Alice didn't need to realise there was a fork...