ConvertFrom
annotation class ConvertFrom(val use: KClass<out MapTypeConverter<*, *>> = MapTypeConverter::class, val onFail: OnFail = OnFail.Auto)
Direction-scoped per-field override: applies only to the @MapFrom (reverse) direction; beats @ConvertWith there. Same parameter shape as ConvertWith — use left at its sentinel default means "keep the auto-discovered converter".
Typical home: a field of the @MapFrom class itself (the mapping's target), so a foreign source class never needs annotating. A directive on the source field is a fallback.