Johan Andrén

Yep. Definitely a quite dated section of the docs. Maybe we should rather list the stages that does honour it rather than the ones that doesn't.

I think there has been a PR merged since this was opened up that added documentation on all stages that _do_ use the supervision strategy, that's in the Scaladoc/Javadoc though,...

Nobody is actively working on this or you'd see that here. You could give it a try fixing the issue and doing a PR if it is an important issue...

I think the forum (https://discuss.akka.io) is better for that kind of a discussion, let's please keep this issue to be about specifically implementing supervision on the flatMapMerge operator, thanks.

Please describe the use case you have and how an operator API would look to cover that use case.

`Running.WithSeqNrAccessible` already is a trait, and is completely internal so should be fine to use in more places, couldn't that work out?

https://github.com/akka/akka/pull/31330 now merged into main so this can be rebased

Note that there is a new CLA for you to sign, it's not a spurious CLA-bot-faillure :)

Thanks for all the work @He-Pin !

I'm on the fence wether it belongs in Akka or not. But at least counterparts of `traverse` and `sequence` is really missing in the Java CS APIs.