Accessibility: Development warnings

Development warnings

The primitives and the kit check a few accessibility rules in development builds and report them with console.warn.

For agentsUpdated 2026-10-20

The primitives and the kit check a few accessibility rules in development builds and report them with console.warn. A warning names the rule in brackets and explains which component needs attention:

Warning	Where	What to do
`[primitives DIALOG_LABEL]`	A `Dialog.Content` (or alert dialog) with no `Dialog.Title`, `aria-label` or `aria-labelledby`	Render a `Dialog.Title`, or pass a name. The check waits for the mount flush, so a title that mounts in the same flush counts.
`[primitives SLIDER_LABEL]`	A `Slider.Thumb` with no name	Pass `aria-label` or `aria-labelledby` to each thumb. Two thumbs need two names.
`[primitives PROGRESS_INVALID_MAX]`	A `Progress` with a `max` that is not greater than 0	Pass a positive maximum. The bar falls back to 100.
`[primitives PROGRESS_INVALID_VALUE]`	A `Progress` value outside `0` to `max`, or not a number (and not `null`)	Clamp the value. The bar is shown as indeterminate until it is valid.
`[primitives TOAST_TYPE]`	A toast with a type other than `foreground` or `background`	Pass one of the two. The toast falls back to `foreground`.
`[primitives TOAST_ACTION_ALT_TEXT]`	A `Toast.Action` with an empty `altText`	Give `altText` the words a screen reader should announce in place of the button.
`[primitives SELECT_EMPTY_ITEM_VALUE]`	A `Select.Item` whose value is the empty string	Use a non-empty value. The empty string is how the select clears its value.
`[primitives CONTROLLED_CHANGE]`	A component switches between controlled (`value` given) and uncontrolled during its lifetime	Decide once: keep `value` present for the component's whole life, or never pass it.