Indeed subtle but I think this is the behavior in JVM Clojure that people tend to rely on. I've fixed a similar issue in #babashka a while back. Running commit + tests here now: https://github.com/borkdude/clojurescript/commit/6157b0803bcf23975ef1f9dc0781cc04b7f5ec25

Sorry, I believe you didn't like threads in this channel.

Threads are ok, it’s just a little bit more annoying when going through the history

fwiw, this behavior for clojure is documented here, https://clojure.org/reference/special_forms#fn > One and only one overload can itself be variadic, by specifying the ampersand followed by a single rest-param. Such a variadic entry point, when called with arguments that exceed the positional params, collects them in a seq which is bound to, or destructured by, the rest param. If the supplied args do not exceed the positional params, the rest param will be nil.

Thanks for digging that up!