The summary of the problem is that everyone should make sure they are running the latest versions of cider-nrepl, piggieback, figwheel and shadow-cljs. refactor-nrepl and sayid currently cause problems, as they weren’t updated. I’ve committed the necessary changes to refactor-nrepl (https://github.com/clojure-emacs/refactor-nrepl/commit/65da8bfbb04fb93554f3c1b56444f00dd4ac1ffd), but I don’t have permissions to cut a new snapshot myself, and I’ve sent a PR to sayid (https://github.com/bpiel/sayid/pull/40).

The gist of the problem that tools.deps users are experiencing is that this defaults now to using nREPL 0.4 (which is a good thing), but not all of the middlewares you might have in your deps is updated to support it (notably refactor-nrepl and sayid).

I assumed that was the case, since I saw it coincided with that update the cider-nrepl rolling out. it would have been good to have some way to not cause these sudden “halt and catch fire” errors. maybe by detecting that sayid and refactor-nrepl didn’t support nrepl 0.4 and either downgrading or disabling them?

It’s easier said than done - refactor-nrepl hasn’t had a stable release in a very long time and with a snapshot you can never know what’s the state there. And, of course, that would imply CIDER should know about some 3rd party middleware and treat it specially, which doesn’t seem very prudent to me (not to mention those injections come from the other projects, not from CIDER itself). Also - something like this would imply that you have to parse the deps (as you have to analyze them before starting the server), which is way outside the scope of CIDER.