as of 4.2, consult the usage of ILateMixinLoader for mod mixins, and for vanilla/forge mixins, consult the usage of IEarlyMixinLoader
@Deprecated
@Target(value=TYPE)
@Retention(value=CLASS)
public @interface MixinLoader
Purely a marker annotation. Use it in classes and said classes will be instantiated.
Make sure there is an empty-arg constructor as LoaderMixin will call newInstance on it.
Feel free to do any Mixin related things in the constructor. But, most importantly, add (mod mixin) configs there.