The rail was a fixed Row(center, max) — one button per tab — so adding the Search tab pushed it 54px past its width and threw a RenderFlex overflow. Center the icons when they fit and scroll horizontally when they don't (LayoutBuilder + SingleChildScrollView + a minWidth floor), so the rail stays correct at any tab count. (T-200) Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>