How can I apply @starting-style formatting to a dialog element using only classes?

I would like to implement the following native CSS code using Tailwind CSS:

dialog {
  border: unset;
  border-radius: 1.25rem;

  &,
  &::backdrop {
    opacity: 0;
    transition: all 0.15s;
  }
  &::backdrop {
    background-color: black;
  }
  
  /* Open */
  opacity: 1;
  &::backdrop {
    opacity: 0.5;
  }

  /* Close */
  @starting-style {
    &,
    &::backdrop {
      opacity: 0;
    }
  }
}

<button commandfor="my-dialog" command="show-modal">Open Dialog</button>

<dialog id="my-dialog">
  <p>Hello World</p>
  <button commandfor="my-dialog" command="close">Close</button>
</dialog>

But by default, I can only do it in CSS using the at-rule.

dialog {
  /* Close */
  @starting-style {
    &,
    &::backdrop {
      opacity: 0;
    }
  }
}

<script src="https://cdn.jsdelivr.net/npm/@tailwindcss/browser@4"></script>

<button
  commandfor="my-dialog" command="show-modal"
  class="py-1 px-2 rounded-md bg-sky-500 text-white"
>Open Dialog</button>

<dialog
  id="my-dialog"
  class="
    opacity-100 [::backdrop]:opacity-50 [&,&::backdrop]:transition-all [&,&::backdrop]:duration-300
    fixed top-1/2 left-1/2 -translate-1/2
    space-y-2 py-2 px-4 rounded-lg [::backdrop]:bg-black
  "
>
  <p>Hello World</p>
  <button
    commandfor="my-dialog" command="close"
    class="py-1 px-2 rounded-md bg-sky-500 text-white"
  >Close</button>
</dialog>

But I don't want to use CSS.

Solution

<script src="https://cdn.jsdelivr.net/npm/@tailwindcss/browser@4"></script>

<button
  commandfor="my-dialog" command="show-modal"
  class="py-1 px-2 rounded-md bg-sky-500 text-white"
>Open Dialog</button>

<dialog
  id="my-dialog"
  class="
    starting:[&,&::backdrop]:opacity-0
    opacity-100 [::backdrop]:opacity-50 [&,&::backdrop]:transition-all [&,&::backdrop]:duration-300
    fixed top-1/2 left-1/2 -translate-1/2
    space-y-2 py-2 px-4 rounded-lg [::backdrop]:bg-black
  "
>
  <p>Hello World</p>
  <button
    commandfor="my-dialog" command="close"
    class="py-1 px-2 rounded-md bg-sky-500 text-white"
  >Close</button>
</dialog>

Note: It's important to note, however, that the @starting-style at-rule is part of the 2024 baseline. Therefore, alongside the default minimum browser support defined by TailwindCSS, you must also take into account the minimum browser versions required for @starting-style support.

Compatibility: Browser support - TailwindCSS v4 Docs
@starting-style browser support - Can I Use?

TailwindCSS v4	with `@starting-style`
Chrome 111	Chrome 117
Safari 16.4	Safari 17.5
Firefox 128	Firefox 129