Bryan asked what that arena was and whether keeping its capacity had a point. It does not: Moves::clear runs only when the root changes, beside a rebuild of the whole tree, where RequestArena::reset runs every frame and the allocation rig checks it. Arena also holds an IdTracker a clear has to reset. The parallel was drawn on the shape of the code rather than on how often it runs. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>