On a GitHub Projects Board (kanban) view, stretches the board to the full window width instead of sitting inside the page’s normal centered, padded column — more room for columns before they need to scroll horizontally.
On by default (unlike Board dependency arrows, which is opt-in). No in-page control — this is a layout default you either want or don’t, toggled once from Settings, not something to flip per session.
Mockup illustrating the layout — not a literal screenshot.
min-width (GitHub sets it inline, computed as columnCount × each column’s configured width — sized to always fit every column at full width no matter how much room the page actually gives it) and turns each column into a flexible, shrinkable flex item with a 140px floor, instead of a fixed-width one.Board-module__boardContainer, Board-module__horizontalGroupAreaContainer, column-frame-module__Box__, …) read off a live board’s DOM. GitHub’s Projects app (internally “memex”) doesn’t publish stable class names — CSS-module hashes regenerate on every deploy, but the un-hashed prefixes this matches on have been stable across the redesigns checked so far.