The current plan is to have runtime support for effects in 5.0, but without a syntax nor an effect type system. Those two will come later in the 5.x branch. The

The current plan is to have runtime support for effects in 5.0, but without a syntax nor an effect type system. Those two will come later in the 5.x branch. The aim is to decouple the switch to the multicore runtime from the design of the typed effect system. In the interim period, effect handlers would be exposed through an experimental module (exposed through an experimental module (see https://discuss.ocaml.org/t/multicore-ocaml-september-2021-effect-handlers-will-be-in-ocaml-5-0 https://discuss.ocaml.org/t/multicore-ocaml-september-2021-e...) to allow early experimentation.