Invoker command

An invoker command is two attributes on a <button>. commandfor names the element the button acts on, by id, and command names what to do to it: show-modal on a modal dialog, close or request-close to send it away, show-popover, hide-popover or toggle-popover on a popover. That is the whole of the wiring, and it has been Baseline since December 2025. What it replaces is the click handler every design system wrote a hundred times: query the document for an id, call showModal(), remember to give focus back on close.

The reason this is a design term rather than an API note is what moves. The relationship between a control and the thing it controls is now stated in the same place as the control, which means one element answers a pointer, a keyboard and a screen reader without anyone deciding to make it do so. A real <button> is focusable, is announced as a button, fires on Enter and on Space, and takes the platform’s own focus return when the dialog it opened closes. The div that somebody remembered to give tabindex and a role was never any of those things reliably, and it failed silently for the readers least able to work around it. It also means nothing has to load first: markup is parsed before your bundle arrives, so the control is live in the moment the reader can see it rather than in the moment hydration finishes.

The platform’s command names are a closed set, and that is the interesting constraint. A command value the platform does not recognise does nothing on its own; a value written with a leading double dash (--copy, --archive) is a custom command, and invoking it fires a CommandEvent on the target element instead. Notice where the listener ends up. The thing being acted on hears about it, rather than the button holding a closure that reaches across the page, so a component can own its own commands and any number of buttons anywhere can invoke them. What has not disappeared is script: a custom command still needs a handler, and the honest summary is that the wiring moved and the behaviour did not.

Two fences are worth keeping. Declarative wiring is not an accessible name: a button reading Delete still has to say what it deletes, and the command attribute tells assistive technology nothing about intent. And the term names the control, not the surface. A disclosure is a control that shows and hides its own content in place, which is a shape of interface; an invoker command is how any control says what it operates on, including a disclosure’s. The <dialog> element’s own closedby attribute belongs to the dialog rather than here.