RapidEnumerator primed the walk position at the first pierce point, then the skipped first rapid advanced it again. Raw programs start with a zero rapid so this was invisible, but lead-in programs start with a real incremental offset to the pierce, which shifted every later rapid by that delta and drew rapids off the sheet. Start the walk at the program origin. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>