I mean it never been released, always was in beta and not enabled by default, and very soon replaced with never implementation, that called internally by Kotlin team as kapt3 (this name appeared in commits, as I remember), it's not even official versions, real difference from an end user point of view was change kapt1 to kapt2/3, from generateStubs to kapt plugin, under the hood it's completely different way to implement jsr269