[jeremyjh]

Java and Crystal are not equivalent - neither have preemptible threads. Lots of other languages have co-routines or other cooperative systems - async/await are really just variants of that.

I didn't check if Gossamer is actually preemptible.

I believe the short list of production languages with preemptible M:N schedulers are limited to:

Erlang/Elixir

Haskell

Go

[msgilligan]

Java threads including Virtual Threads (JDK 21+) are preemptive.