docs(foundations): add a page on CSS container queries#61
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Documents container-type/@container size queries (CSS Containment Module Level 3) and the newer style queries (CSS Conditional Rules Module Level 5). Status: recommended — a modern site should style components by their container, but the platform works without it. Size container queries have been Baseline widely available since February 2023; style queries reached Baseline newly available in May 2026. Wires relatedSlugs on anchor-positioning, css-containment, and dynamic-viewport-units; adds the changelog entry and OG images. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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…queries 'Baseline (widely available) since February 2023' conflated the newly- available date (Feb 2023, Firefox 110 — last core engine) with widely- available. Size queries became Baseline in Feb 2023 and are now widely available; the style-query date (May 2026) was already correct. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
After merging main (the inert page, #60), the total page count is 152; regenerate the count-driven og-default / checklist / spec images so they reflect it. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Reviewed and improved before merge:
Verified the CSS-WG / MDN sources, the MDN canonical |
jdevalk
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Jun 27, 2026
…lake (#62) The links job shelled out to `npx linkinator`, whose CLI runs `await main()` at the top level. On Node 22 the event loop can empty while that await is still pending, aborting with exit 13 ("unsettled top-level await") after fetching only `/` — a deterministic crash, not a broken link, that the earlier retry-on-13 hardening (#58/#59) could not reliably paper over (it still failed on PRs #60 and #61). Replace the CLI with scripts/check-links.mjs, which drives linkinator's LinkChecker class programmatically and resolves with `.then()`/process.exit so our process can't hit the same foot-gun. Pin linkinator as a devDependency for a stable version. Both jobs (internal --internal, external --config) use it; the config's `skip` list maps to the API's `linksToSkip`. Verified locally: builds, serves, and scans 1500 internal links (0 broken, exit 0) with no exit-13 crash. Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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What
Adds a new spec page: CSS container queries under
foundations.Covers both halves of the feature:
container-type/container-name+@container (min-width: …), so a component responds to the space its container gives it rather than the viewport.@container style(--custom-prop: …), testing a container's computed custom properties.Also:
relatedSlugsboth ways on three adjacent pages (anchor-positioning,css-containment,dynamic-viewport-units).addedchangelog entry.og-default,og/checklist,og/spec,og/spec/foundations).Why now
Container queries are a notable gap in an otherwise comprehensive modern-CSS set (we already cover anchor positioning, scroll-driven animations, text-wrap, css-containment, dynamic viewport units). Style queries reached Baseline (newly available) in May 2026, which prompted the audit — and surfaced that size queries (Baseline widely available since February 2023) were never documented either.
Primary sources
container-type,container-name,@container(W3C CSS WG).style()(W3C CSS WG, Working Draft 27 May 2026).@containerfor context (canonical current URL).Status
recommended— a modern, component-based site should style by container, not viewport, but the platform contract does not break without it. Notrequired.Checks
npm run buildpasses; page renders and appears at the HTML route, the.mdendpoint, and in/llms.txt.npm run lint(0 errors; 1 pre-existing warning in an untouched file) andnpm run format:checkpass.Opened as a draft for maintainer review per the daily standards-scan routine — not for auto-merge.
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