Four gaps found shipping in Opus 4.8 eval samples during human review:
1. low-contrast (extended): the browser adapters parsed text/own-bg
colors with parseRgb only, so Chrome's oklch()-serialized computed
colors silently skipped every contrast check — a flat dark-on-dark
nav CTA (broader nav selector beating the button class) shipped at
1.5:1 undetected. checkElementColorsDOM and readOwnBackgroundColor
now fall back to parseAnyColor. Near-threshold ratios print two
decimals so a 4.497 finding no longer reads "4.5 needs 4.5".
2. NEW numbered-section-labels (slop, advisory): tiny (<=13px) styled
numeric index labels riding beside section headings, repeated across
2+ sections with distinct indices. Sibling of repeated-section-kickers
(which deliberately excludes bare numeric labels); handles both the
direct prev-sibling shape and label-before-heading-wrapper shape.
List/nav/table/card-item numbering is exempt.
3. side-tab (extended): the vertical pseudo-element stripe scan required
the stripe to touch both corners (top/bottom 0 or height 100%), so a
left accent bar inset a few px from each end evaded it; small end
insets (<=20px each) now count. Added a browser-side pseudo-element
check (getComputedStyle(el, '::before'/'::after')) since runtime-
assigned custom-property colors are invisible to the text scanner.
Selection-state exemptions stay as narrowed: only aria-selected=true /
aria-current / active-class markers exempt, plus button/link
affordances on the horizontal variant.
4. NEW repeated-container-text (quality): the same literal string (>=4
chars, contains letters) rendered 3+ times at 3+ structurally distinct
positions inside one bordered/elevated container. Parallel/templated
repetition (table cells, calendar grids, nav lists, identical sibling
rows) never counts — structural signatures, not word lists.
Verified: each rule fires on its repro sample via the file:// browser
scan; clean eval samples add no new findings (the new low-contrast hits
on other samples are genuine sub-AA oklch button pairs). Full test
suite green; browser bundle regenerated; README/homepage rule counts
bumped 49 -> 51 (docs-integrity test enforces them).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
