Accessibility

MentionsInput implements the WAI-ARIA editable combobox with list autocomplete pattern:

• The input has role="combobox" with aria-autocomplete="list" (or "inline" when suggestionsDisplay="inline"), aria-haspopup="listbox", and aria-expanded reflecting whether suggestions are open.
• The open suggestions overlay is a role="listbox" (labeled via a11ySuggestionsListLabel) referenced by aria-controls, and its focused role="option" is referenced by aria-activedescendant, so focus never leaves the input while navigating with the arrow keys.
• Inline autocomplete announces the current completion through a visually hidden live region referenced by aria-describedby.
• Remember to give the input an accessible name — pass aria-label or associate a <label> yourself.

Expected screen-reader behavior

Typing a trigger announces that a list is available; ArrowUp/ArrowDown announce each suggestion as it becomes active (via aria-activedescendant); Enter or Tab inserts the active suggestion; Escape closes the list.

Known deviation

In multiline mode the ARIA-in-HTML spec disallows an explicit role on <textarea>, but the combobox role is required for the aria-expanded/aria-controls/aria-activedescendant wiring above and is well supported by screen readers (axe-core rates it minor). Single-line mode (singleLine) renders an <input type="text"> and is fully conformant.

These invariants are enforced by the axe-core suite in tests/MentionsInputA11y.spec.tsx, which validates the closed, open-overlay, inline-autocomplete, and form states.