[csswg-drafts] [css-values] Can we remove the limit for @property initial-value being computationally independent? (#13628)

mirisuzanne has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-values] Can we remove the limit for @property initial-value being computationally independent? ==
This came up in the discussion of https://github.com/w3c/csswg-drafts/issues/12735

Authors have used custom properties for a long time to establish design systems. The general approach is to define things on the root. These values may or may not be computationally independent, and the authors is not considering that distinction specifically. These are reasonable context-dependent props from a design system:

```css
html {
  --accent-color: light-dark(deepPink, hotPink);
  --complementary-color: oklch(from var(--accent-color) l c calc(h + 180));
  --gap: round(2cqi, 0.25lh);
  --xx-large: 2.5em;
}
```

Now there are various reasons that an author might want to move any one of those into `@property` - to support animating, or enforce a type, or turn off inheritance, etc. And `@property` allows us to set what _seems like_ a global variable fallback in the `initial-value`. From an authoring perspective, any and all of these seem like reasonable global fallbacks for my custom property. But none of them are allowed as `initial-value` settings. And the 'computationally independent' restriction is not a concept that exists anywhere else when authoring. It's surprising when you try to move custom property 'defaults' from the root to `@property` and you run into a totally unfamiliar restriction.

/cc @tabatkins who asked me to open the issue

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/13628 using your GitHub account


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Received on Wednesday, 11 March 2026 16:57:31 UTC