There's no Thread in core mruby (you have to go through a mrbgem[0]), so I don't think there is Ractor stuff in there. [0]: https://github.com/mattn/mruby-thre

There's no Thread in core mruby (you have to go through a mrbgem[0]), so I don't think there is Ractor stuff in there. [0]: https://github.com/mattn/mruby-thread https://github.com/mattn/mruby-thread EDIT: confirmed $ nix-shell -p mruby nix$ mirb mirb - Embeddable Interactive Ruby Shell > RUBY_VERSION => "3.1" > Ractor uninitialized constant Ractor (NameError)