Components
Suggestion Menu
Editor-driven slash command and @mention lists: focus stays in the editor, arrows clamp, Enter / Tab select, Escape closes.
Slash commands and mentions
Type “/” for the command menu (grouped, anchored to the composer's left edge, 240-512px) or “@” for the 576px mention list anchored to the caret. Keep typing to filter: groups drop away and matched characters render at weight 580. The first row is active after every change; ArrowUp / ArrowDown stop at the ends.