Icon Button
A round, icon-only action for toolbars and dense rows. It is Button's interaction recipe — the same colours, hover lift, focus halo and disabled state — on a compact circular scale (28 / 32 / 36px), because an icon control in a dense row should not be as tall as a text button; md lines up with an sm text Button. For an icon button that must match a text button's height, use Button size=icon. Always pass a tooltip so it stays labelled.
Icon only
No label — just a centered icon. The tooltip doubles as the aria-label.
Variants
Both rest in the subtle text colour and rise to emphasis on hover. default is Button's ghost; outline is Button's outline (hairline, lift on hover).
Active / emphasis — brainstorm
Softer alternatives to a solid ink circle for an active/selected control. A → F, quiet → strong. B (brand tint) matches the app's selection language; D (solid brand) is the filled option for a primary action.
Sizes
sm / md / lg map to 28 / 32 / 36px circles. The icon scales with the button (size-3.5 / size-4 / size-5).
Sizes — outline
The same square scale with the outline variant.