LGTM1. Interoperability/compatibility risk is very low.

On Wed, Aug 5, 2026 at 6:24 AM Javier Fernandez <[email protected]>
wrote:

> *Contact emails*
> [email protected]
>
> *Specification*
> https://www.w3.org/TR/css-typed-om-1/#stylevalue-subclasses
>
> *Summary*
> The CSS Typed OM spec exposes the CSSStyleValue hierarchy to worker global
> scopes ([Exposed=(Window, Worker, PaintWorklet, LayoutWorklet)]), but Blink
> only exposed CSSStyleValue, CSSKeywordValue, CSSNumericValue, CSSUnitValue
> and CSSUnparsedValue to Window and the worklets. As a result these
> constructors were undefined in Workers, unlike in Firefox and Safari.
>
> *Blink component*
> Blink>CSS
> <https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3ECSS%22>
>
> *Web Feature ID*
> css-typed-om <https://webstatus.dev/features/css-typed-om>
>
> *Motivation*
> Aligns Chrome with the spec's [Exposed] set and removes a cross‑thread
> inconsistency (these constructors are currently undefined in workers);
> enables off‑main‑thread CSS value manipulation
>
> *Initial public proposal*
> *No information provided*
>
> *TAG review*
> *No information provided*
>
> *TAG review status*
> Not applicable
>
> *Goals for experimentation*
> None
>
> *Risks*
>
>
> *Interoperability and Compatibility*
> This feature is already shipped by Firefox and Safari and it's purely
> additive worker‑scope exposure; zero change to existing Window behavior;
> matches the spec. Only theoretical risk: content that feature‑detects these
> globals inside a worker
>
> *Gecko*: Shipped/Shipping
>
> *WebKit*: Shipped/Shipping
>
> *Web developers*: No signals
>
> *Other signals*:
>
> *WebView application risks*
>
> Does this intent deprecate or change behavior of existing APIs, such that
> it has potentially high risk for Android WebView-based applications?
> *No information provided*
>
>
> *Debuggability*
> No special tooling; interfaces work in the worker DevTools console like
> any other worker‑exposed API
>
> *Will this feature be supported on all six Blink platforms (Windows, Mac,
> Linux, ChromeOS, Android, and Android WebView)?*
> Yes
>
> *Is this feature fully tested by web-platform-tests
> <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>?*
> Yes
> css/css-typed-om/stylevalue-subclasses/*.any.js (global=window,worker):
> cssKeywordValue, cssKeywordValue-value, cssUnparsedValue-empty,
> numeric-objects/cssUnitValue-to; and (full‑scope) the converted
> create-a-type, cssMathInvert-type, cssMathNegate-type, add-two-types,
> cssnumericvalue-multiply-two-types, arithmetic, to .any.js. (The CSSMath*
> ones require the full‑scope exposure.)
> https://wpt.fyi/results/css/css-typed-om/stylevalue-subclasses?label=experimental&label=master&aligned
>
> *Flag name on about://flags*
> *No information provided*
>
> *Finch feature name*
> *No information provided*
>
> *Non-finch justification*
> This is just a minor CSS change to allow some CSS javascript bindings to
> be run in Worker context, but that were already exposed to the Web via
> Window context.
>
> *Rollout plan*
> Will ship enabled for all users
>
> *Requires code in //chrome?*
> False
>
> *Tracking bug*
> https://issues.chromium.org/issues/534781956
>
> *Estimated milestones*
> Shipping on desktop 153
> Shipping on Android 153
> Shipping on WebView 153
>
> *Anticipated spec changes*
>
> Open questions about a feature may be a source of future web compat or
> interop issues. Please list open issues (e.g. links to known github issues
> in the project for the feature specification) whose resolution may
> introduce web compat/interop risk (e.g., changing to naming or structure of
> the API in a non-backward-compatible way).
> https://github.com/w3c/csswg-drafts/issues/14229
>
> *Link to entry on the Chrome Platform Status*
> https://chromestatus.com/feature/5114591051907072?gate=6116938171416576
>
> This intent message was generated by Chrome Platform Status
> <https://chromestatus.com/>.
>
>
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> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/0786569a-3c4b-421c-af22-a6bc4a717ccc%40igalia.com
> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/0786569a-3c4b-421c-af22-a6bc4a717ccc%40igalia.com?utm_medium=email&utm_source=footer>
> .
>


-- 
TAMURA Kent
Software Engineer, Google

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