In aiming to achieve better compatibility with other mods, Sponge has been replacing various @Redirects with @WrapOperations. This leads to greater user experience when they throw our mods together (like in NeoForge). Otherwise, if Sponge moves to using WrapOperation, there's no way Sponge's event tracking system will work when Observable is installed.

I've went and made a branch of Sponge to begin testing with the WrapOperation changes to see if this will be sufficient, once Observable switches over to using the same annotation for its own functionality.

For what it's worth, this is discovered from SpongePowered/Sponge#4165 's investigation. It seems likely that the PR that rearchitects some of Sponge's injection points to avoid collisions is "working" with observable.