This topic can be used for discussions and feedback around ⚙ D13533 Adding Manifold Next Event Estimation Sampling Technique
There is a test build here.
Important: This feature is in early development, and not in master yet. The implementation may have bugs and limitations. This is a feature contributed by Reality Labs and developed specifically to render eye caustics. We are still evaluating how well it works as a feature for general rendering of refractive caustics in Cycles.
Just opening this topic, to keep the code review focused on development and give users a chance for feedback here.