Is clojure.repl.deps/sync-deps supposed to work with :local/root deps?
Haven't tried to reproduce it with another project, but just had a case where sync-deps didn't work (namespace not found when evaluating the (ns ...)), but after quitting and restarting the repl (in cider) everything is fine.
Should work as far as I know. I presume you added a local project to your deps.edn and then did a sync-deps?
Yes, that's what I did. I'll report back if I reproduce it, I guess there could have been many other things that could have gone wrong with a long running session.