Changelog

2026-10-17

Added references for the Style tools framework, the Props tools framework, the shared editor inputs and the HTML validation engine, plus an architecture explanation covering both tabs.
Added how-tos: add a style tool, add an HTML attribute tool, add an HTML check.
Added ADR-0002 (forced element states via an injected, EID-scoped stylesheet) and ADR-0003 (remove flag on ATTRIBUTE-UPDATE).
Updated the matched-rules reference: registerStylesheet now takes { origin, displayPath }, MatchedRule.origin, :is(*) semantics for activePseudoClasses, and the new STATE_PSEUDO_CLASSES / buildForcedStateCss exports. Updated the matcher section of the matched-rules explanation accordingly.

Added reference page and explanation page for the new apps/frontend/src/lib/matched-rules library — the in-page primitive that returns every CSS rule affecting a DOM element in the preview iframe, with source positions, specificity, and cascade-aware ordering. Foundation for the upcoming Styles inspector panel.
Added the first ADR — ADR-0001: Matched-rules library is in-page and uses lightningcss-wasm — recording why we chose an in-page implementation over a DevTools Protocol bridge, why lightningcss-wasm over CSSOM / a hand-written parser, and the matcher/cascade split. Removed the “no ADRs yet” placeholder from the ADR index.

Added an explanation of the StyleController’s Classes component — covers the multi-select intersection rule, the deliberate replace vs replaceAll split between remove and rename, and the ActionManager do/reverse payload pattern.