Avoiding Subcomposition Pitfalls — Keep Composition Out of the Measure Pass

SubcomposeLayout runs its content's composition during the measure pass, not during the parent's composition pass. That trades extra layout cost for the ability to use measured constraints inside the children's composition. BoxWithConstraints, material3.Scaffold, and the lazy layouts are all built on top of it, so the cost is invisible until it nests or lands inside a hot path. This skill teaches Claude how to detect the misuse, how to replace SubcomposeLayout with a cheaper primitive when its power is not needed, and how to keep it efficient when it is.

When to use this skill