As far as I see, OnWillRenderObject is not being called in the Prefab Stage for the Scene viewport. This is very different from behavior of Scene viewport in traditional main stage of Edit mode, where every object received OnWillRenderObject calls. To reproduce this, make sure to hide the Game View and simply add some logging to a OnWillRenderObject function. Is that a bug or an intentionally introduced difference? Edit: Disregard that, the issue was simply caused by an object I was expecting to render sitting in the main stage instead of the prefab stage. That was the reason for absence of OnWillRenderObject calls - Scene view locked to prefab stage never interacted with it.