debugSnapshotVisibleOffsetsCount property
Lifetime count of snapshotVisibleOffsets calls. Perf oracle for the first-wins baseline: K animated mutations in one frame must produce exactly ONE staging snapshot, not K of them, because the slot keeps only the first. The walk is O(visible) with a map entry and a key hash per row, so the discarded ones were the dominant cost of a batched reparent.
Implementation
int debugSnapshotVisibleOffsetsCount = 0;