Hey! I get this error when trying to load my mod together with a few others:

de.fr3qu3ncy.shadowmobs.caps.BooleanCapability cannot be cast to com.robertx22.age_of_exile.dimension.dungeon_data.WorldDungeonCap
	at com.robertx22.age_of_exile.uncommon.datasaving.Load.dungeonData(Load.java:38) ~[mmorpg:?] {re:classloading}
	at com.robertx22.age_of_exile.event_hooks.ontick.OnTickDungeonWorld.onEndTick(OnTickDungeonWorld.java:13) ~[mmorpg:?] {re:classloading}

How can the other mod access my (BooleanCapability) cap? It is loaded by World#getCapability and the capability has a unique resource location, both caps are attached in CapabilityAttachEvent<World>.

The BooleanCapability class doesn't even exist in age_of_exile.

Other mod's code: https://github.com/RobertSkalko/Age-of-Exile/blob/c5740a9cca788b8d02d904ca5230f34381e25d43/src/main/java/com/robertx22/age_of_exile/uncommon/datasaving/Load.java#L36

My code: https://pastebin.com/KknmYrpc

it is okay for other mods to access your capabilities - assuming both developers know what they're doing.

i don't feel like looking at source code of either mod, but i can tell you that authors of cold sweat mod had the same issue with half a dozen other mods, including the exile-whatever mod. they changed something two months ago and cut the list of incompatible mods by half. maybe you could ask them about it on their discord?

Your code is faulty.

        @Nonnull
        @Override
        public <T> LazyOptional<T> getCapability(@Nonnull Capability<T> cap, @Nullable Direction side) {
            return implementation.cast();
        }

Me, accessing a restaurant's website: "Hello, yes sir, I would like to see your menu."
You, the restaurant owner: "HERE'S MY FRIDGE"

The whole point of the cap parameter is so that you know which capability is being asked for. If you aren't being asked for your capability, don't return YOUR capability.