The line-number ::before was an inline-block at the head of every line, so CSS tab stops (multiples of tab-size from the line box start) landed mid-phase after the gutter's width - the first tab rendered at whatever remainder was left (width 1 at tab-size 2, 3 at 4, 1 at 5...). Numbers now sit absolutely positioned inside reserved padding, each line is its own pre-formatted block, and the first tab stop lands a full tab-size from where the code starts at every width. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>