CSS Coverage and Parity Status¶

Reference imported from v2.4.0. Check the installed runtime for your exact version.

This document is the canonical statement of validated CSS coverage for Fullbleed's deterministic HTML/CSS-to-PDF engine.

Scope baseline: static, paged document rendering (transactional/report workflows), not a live browser runtime.

Source taxonomy: https://developer.mozilla.org/en-US/docs/Web/CSS

Validation Basis¶

As of May 25, 2026:

Fixture suite: 86/86 fixtures passing with 603 assertion/paint checks (_css_working/tmp/fixture_full_latest.json)
Parity status check: green (.venv\Scripts\python.exe tools/generate_css_parity_status.py --check --json)
Canonical benchmark lane: examples/css_parity_canonical_100
Visual stress lane: examples/css_visual_charts_showcase

Primary generated artifacts:

_css_working/css_parity_status.json
_css_working/css_broad_coverage_sprint_s14.md
_css_working/tmp/fixture_full_latest.json

Official Wheel265 closeout (August 9, 2026)¶

The complete pinned independent IronPress gate finished with 1,642 PASS, 0 FAIL, and 20 REFERENCE-DISPUTED across 1,662 fixtures. Strict parity is therefore 100% for every adjudicable fixture in this corpus. Native parity has the same zero-failure implementation result; the 20 disputed references remain separately visible and are not silently counted as passes.

The durable report records invocation 78173eed3cd2bf2c70127eef63092119 with run_complete=True. This is a 100% result for the named, pinned Wheel265 corpus—not a claim that every CSS feature in the web platform is implemented. The module table below continues to describe the engine's broader standards surface and known boundaries.

Flow/reflow hardening (August 5, 2026)¶

The independent review's 18-case flow/reflow failure cluster now passes 18/18 in the pinned Chromium-oracle diagnostic lane. Thirteen cases are pixel-exact; the largest remaining above-floor difference is 0.97030199%. This is a filtered regression result, not a claim that the complete external corpus is at 100% parity.

The verified behavior added in this pass includes:

slicing the unused painted tail of fixed-height block, one-column grid, and column-flex items across fragmentainers without duplicating their content;
resetting fragmented flex-item basis and preserving auto-grid row continuations so later fragments remain measurable and drawable;
retaining display: contents grid descendants, metadata, and absolute paint phase across page continuations;
constructing figure and figcaption as UA block boxes so break-inside: avoid retains an empty, styled fixed-height caption; and
keeping fixed-height positioned containing blocks atomic, because clearing a continuation could otherwise detach nested absolute descendants.

Generated-content interaction closeout (August 6, 2026)¶

A follow-up run of the pinned 62-fixture generated-content and interaction slice produced 60 official comparator passes, zero implementation failures, and two reference-disputed cases. The disputed references are generated-content-first-letter-dropcap (the reference omits authored box paint and uses a different content width) and generated-content-string-set-running-header (the reference clips and mangles the running-header text). They remain visible in the evidence set and are not counted as comparator passes.

The formerly failing positioning, anonymous-table, and filtered generated- content cases now measure 0.05238154%, 0.39256615%, and 0.90102154% above-floor difference, respectively. Filtered forms use a scoped 8x8 native coverage pass to match Skia edge quantization; ordinary vector and variable- data rendering stays on the existing 4x4 raster path. Core layout geometry continues to use signed Q32.32 fixed-point arithmetic.

This targeted result does not replace the complete external-corpus report or claim 100% parity for every CSS fixture.

Independent compiled-reflow QA hardening (August 10, 2026)¶

Fullbleed 2.2.5 addresses the three pagination/generated-content issues reported by the independent 1,750-page compiled-reflow review:

a table taller than a fresh frame now fragments in the current remainder, so a break-after: avoid heading stays with the initial table fragment;
an oversized break-inside: avoid box relaxes avoidance before a fresh-page retry, preventing an avoidable underfilled heading page; and
string-set accepts both content() and content(text), including rules whose only declaration is string-set, and carries the value through string(name) continuation-page margin boxes.

Focused Rust regressions cover all three paths. The ordinary layout and compiled reflow lanes share this pagination and named-string implementation.

Current Coverage Summary¶

Tracked CSS modules: 22

Module status: 22/22 in_progress
Parser stage: 22/22 partial
Compute stage: 22/22 partial
Layout stage: 16/22 partial, 6/22 n/a
Paint stage: 10/22 partial, 12/22 n/a

Static PDF Library Readiness¶

Assessment: this epoch is ready to close for the static PDF library use case. Fullbleed is not claiming browser-equivalent CSS parity, but it now has enough validated breadth, deterministic fallback behavior, and diagnostics to be useful as a production library for transactional, report, VDP, form, invoice, statement, menu, and chart-style static PDFs.

The release-quality contract for this stage is:

Supported CSS/HTML behavior should render deterministically and stay covered by fixtures.
Unsupported or intentionally degraded behavior should be deterministic, diagnosable, and tracked as known-loss/fallback work rather than silently drifting.
Static paged output is the product target; interactive browser runtime behavior is out of scope.

Ready now:

Static paged layout with core block/inline/flex/table/grid-like lowering, positioned/fixed content, forced breaks, @page sizing, and core fragmentation controls.
Production document styling breadth: typography, generated content, counters, lists, tables, backgrounds, borders, outlines, overflow clipping, images, object-fit/object-position, 2D transforms, color functions, and broad cascade rollback coverage.
Static visual polish features with defined boundaries: background images and blends, box shadows, clip-path subsets, filters/backdrop-filters, blend modes, opacity grouping, isolation, and backdrop-root behavior.
Operational safety: full fixture lane, parity status artifact, deterministic diagnostics, reproducibility tooling, and benchmark/stress examples.

Not claimed in this epoch:

Full browser/CSS compatibility, exact browser print fidelity, JavaScript or interactive layout behavior.
True multi-column layout, full grid/flex/table edge parity, full vertical text layout, sticky positioning, 3D transforms/perspective, complete SVG filter and clip-source semantics, and all advanced CSS value/color/effect grammar.
Pixel-identical parity for every advanced visual effect; remaining gaps are backlog items for the next parity push.

Closeout decision: there are no remaining blockers that should hold this broad coverage epoch open for static PDF library usefulness. The remaining work belongs in the next epoch as parity-depth hardening.

Module Matrix (22 Tracked)¶

Legend: p parser, c compute, l layout, pa paint.

Module	Stage footprint	Validated now	Backlog focus
Syntax and at-rules	p:`partial` c:`partial` l:`n/a` pa:`n/a`	Typed + unparsed declaration paths plus `@media` print/all/list/not media-type handling, device-posture, shape, deprecated device-width/height/aspect-ratio aliases, WebKit extension Boolean media features, Level 5 static-output descriptor defaults, WebKit/Mozilla device-pixel-ratio aliases, scan, video-dynamic-range, display-mode, resolution, color capability/range, user-preference, input-device, viewport-segment, static-output environment, width/height, aspect-ratio, and orientation gating, `@supports` declaration/selector feature-query gating with `not`/`and`/`or` conditions, `@property` registered initial/inheritance/syntax-check behavior, `@starting-style`, `@keyframes`, and `@view-transition` static-output no-op handling, `@container` size-query gating for explicit named/unnamed query containers, and `@scope` subtree/limit gating	Advanced at-rule breadth and edge grammar
Selectors	p:`partial` c:`partial` l:`n/a` pa:`n/a`	Deterministic selector parser/indexing baseline plus `::before`/`::after` string, `::marker` generated-content marker overrides, `::marker content:none` marker suppression, `::marker` gating to list-item origins, `attr(...)`, explicit `quotes`, styled `counter(...)`/`counters(...)`, `counter-set`, duplicate-reset, reversed-counter-set generated-content text flow, and `display:none` pseudo-element counter suppression	Broader selector/pseudo-class and generated-content parity
Cascade and inheritance	p:`partial` c:`partial` l:`n/a` pa:`n/a`	Specificity + source order + `!important` channels plus `@layer` statement/block precedence, unlayered normal priority, reversed important layer priority, and fixture-backed `revert-layer` rollback for `color`, `background-color`, `width`, `height`, `box-sizing`, `display`, `visibility`, `position`, `z-index`, `direction`, `writing-mode`, `opacity`, `filter`, `backdrop-filter`, `clip-path`, `box-shadow`, `text-shadow`, text-decoration line/color/thickness/style, text underline offset/position, `text-overflow`, `text-indent`, `letter-spacing`, `word-spacing`, `tab-size`, `text-align`, `text-align-last`, `text-justify`, `text-transform`, `vertical-align`, `list-style-position`, `list-style-type`, `list-style-image`, `line-break`, `hyphens`, `hyphenate-character`, `overflow-wrap`, `word-break`, `word-wrap`, `white-space`, `white-space-collapse`, `text-wrap`, `text-wrap-mode`, `text-wrap-style`, `overflow`, `mix-blend-mode`, `isolation`, physical/logical inset offsets, physical/logical margin/padding edges, physical/logical `border-color`/`border-width`/`border-style` edges, outline shorthand plus width/style/color longhands, and `outline-offset`	Broader `revert`/`revert-layer` keyword breadth and deeper layer/import interactions
Values and units	p:`partial` c:`partial` l:`n/a` pa:`n/a`	Canonical calc path with var-chain, `min/max/clamp` subsets	Wider value grammar/function breadth
Box model	p:`partial` c:`partial` l:`partial` pa:`partial`	Margin/padding/border/box-sizing baseline plus `box-sizing` cascade rollback, `outline` shorthand, `outline-offset` outside/inside paint, dashed/dotted/double outline styles, groove/ridge/inset/outset shaded square-outline paint, and rounded plus non-uniform groove/ridge/inset/outset 3D outline paint	Edge-case constraint and interaction hardening
Display and formatting contexts	p:`partial` c:`partial` l:`partial` pa:`n/a`	Block/inline/flex/table/grid-like lowering baseline, `display:list-item` marker generation with implicit `list-item` counter support, including non-`li` children inside list containers, `display: contents` child rendering with no wrapper counter mutation, `visibility:hidden`/`collapse` paint suppression with retained layout plus explicit visible descendant paint, HTML table-row `visibility:collapse` slot removal while `visibility:hidden` keeps the row slot, HTML table-row-group group-wide `visibility:collapse` slot removal even when a child row computes visible, HTML table-column `visibility:collapse` slot removal while preserving non-collapsed column sizing, CSS `display:table-row` `visibility:collapse` slot removal while `visibility:hidden` keeps the row slot, CSS `display:table-row-group` group-wide `visibility:collapse` slot removal even when a child row computes visible, CSS `display:table-header-group`/`display:table-footer-group` ordering before/after body groups, CSS `display:table-column` `visibility:collapse` slot removal plus `display:table-column-group` group-wide collapse while preserving non-collapsed column sizing, CSS `display:table-caption` `caption-side: bottom` placement, plus `<img>` replaced-content intrinsic raster sizing, `object-fit: contain`/`cover`/`none`/`scale-down` paint, and `object-position` percentage/edge-offset paint	Broader formatting-context parity
Positioning	p:`partial` c:`partial` l:`partial` pa:`n/a`	Relative/absolute/fixed deterministic baseline plus `position`, `z-index`, and inset cascade rollback	Sticky/edge semantic breadth and interactions
Sizing	p:`partial` c:`partial` l:`partial` pa:`n/a`	Width/height/min/max core coverage plus `<img>` intrinsic raster dimensions, aspect-ratio preservation for missing paired dimensions, `object-fit: contain`/`cover`/`none`/`scale-down` image-box fitting, and `object-position` alignment inside image boxes	Remaining intrinsic sizing and pressure edge cases
Text and fonts	p:`partial` c:`partial` l:`partial` pa:`partial`	Text styling, fallback, shaping hooks baseline plus `font-family` quoted-name versus generic-family custom-property fallback and cascade override behavior, `font` shorthand core longhand set/reset behavior with system-font and `var()` custom-property fallback coverage, `line-height` unitless/length/percentage/custom-property inheritance behavior, `font-size` keyword/relative/custom-property computed sizing, `font-weight` relative keyword resolution, `font-style` italic/oblique-angle resolution, `vertical-align` MDN keyword/custom-property table-cell paint behavior plus cascade rollback, `white-space` keyword parsing and preserved-space wrapping plus cascade rollback, `white-space-collapse` longhand plus modern `white-space` collapse/wrap shorthand behavior plus cascade rollback, `text-wrap` shorthand/longhand keyword and custom-property wrapping mode behavior plus cascade rollback, `line-break:anywhere` wrapping, `hyphens` soft-hyphen wrapping, `hyphenate-character` soft-hyphen marker replacement, `word-spacing` length/percentage wrapping plus cascade rollback, `letter-spacing` percentage wrapping plus cascade rollback, `overflow-wrap`/`word-wrap`/`word-break` long-word splitting plus cascade rollback, `text-transform` core case rendering, `text-overflow` ellipsis gating plus cascade rollback, `text-decoration-color` currentColor/longhand/shorthand/custom-property paint plus cascade rollback, `text-decoration-thickness` length/percentage/shorthand/custom-property paint plus cascade rollback, `text-decoration-style` solid/double/dotted/dashed/wavy paint plus cascade rollback, `text-underline-offset` auto/length/percentage/negative/custom-property/inherited paint plus cascade rollback, `text-underline-position` auto/under/side-keyword/custom-property paint plus cascade rollback, `text-shadow` list/custom-property text and decoration paint plus cascade rollback, `text-indent` length/percentage/keyword wrapping plus cascade rollback, `tab-size` number/length preserved-tab drawing plus cascade rollback, text alignment cascade rollback, text transform, vertical alignment, and hyphenation cascade rollback, `text-align-last` final/forced-break alignment, `text-align: justify` word-gap distribution, and `text-justify` core justification modes	Typographic edge behavior breadth
Backgrounds and borders	p:`partial` c:`partial` l:`partial` pa:`partial`	Solid + shorthand/longhand gradient backgrounds, sized no-repeat multi-layer gradient backgrounds, repeat-x tiled sized gradients, `space`/`round` repeat semantics for sized gradients, explicit-size PNG `url(...)` backgrounds, auto-auto intrinsic PNG sizing, invalid negative `background-size` rejection, `contain`/`cover`/auto-dimension/single-value intrinsic-ratio PNG sizing, alpha-stacked PNG `url(...)` layers, default and explicit `repeat repeat` tiling, PNG `repeat-y`, two-axis `repeat`, `repeat no-repeat`, `no-repeat repeat`, single-value `space`/`round`, `round space`, `space round`, `round repeat`, `round no-repeat`, `no-repeat round`, `no-repeat space`, `space no-repeat`, `repeat space`, `repeat round`, `space repeat` tiling, horizontal-tb logical repeat aliases (`repeat-inline`/`repeat-block`), multi-layer PNG repeat-axis mapping plus shorter size/repeat/position list repetition, percentage/edge-offset/logical-alias `background-position` anchoring, shorthand URL position/size/repeat propagation, content-box `background-origin`/`background-clip`, multi-layer origin/clip list mapping, `background-blend-mode` normal/multiply/screen/difference/overlay/exclusion/hard-light/darken/lighten/color-dodge/color-burn/soft-light/hue/saturation/color/luminosity/plus-lighter over element background color, raster PNG background-blend multiply, multi-layer raster and bidirectional mixed raster/gradient background-blend mapping, multi-layer background-blend-mode list repetition, and extra-value truncation, border color propagation plus four-value color shorthand mapping, keyword border widths, four-value circular, slash-syntax elliptical, dashed/dotted rounded border-radius paint, rounded double border-radius paint, uniform and non-uniform rounded 3D border-radius paint, dashed/dotted/double, four-value side-specific style shorthand mapping, `none`/`hidden` width suppression, omitted-style `border` shorthand invisibility, groove/ridge/inset/outset square-border paint, collapsed-table `hidden` border conflict suppression, collapsed-table `inset`/`outset` alias paint, equal-width collapsed-table border-style precedence, authored-style collapsed-table precedence before `outset`/`groove` paint aliasing, RTL equal-style cell color/source precedence, collapsed table-level hidden outer border suppression, collapsed row-source border precedence, collapsed rowgroup-source border precedence, collapsed column-source vertical border precedence, and collapsed colgroup-source vertical border precedence, strict `box-shadow` length/color grammar plus modern `rgb()`/absolute-unit shadow paint, softened blurred inset edge paint, directional inset offset edge paint, and `box-shadow` cascade rollback	Remaining multi-layer image edge semantics, broader mixed raster asset stacks, and deeper border/background edge cases
Lists and counters	p:`partial` c:`partial` l:`partial` pa:`partial`	List rendering baseline + predefined/string `list-style-type` marker subset, including marker suppression, roman, Armenian/Georgian/Hebrew additive markers, leading-zero, broad numeric script markers, CJK fixed markers, Japanese/Korean/Chinese longhand markers, the `cjk-ideographic` legacy alias, string-based `symbols()` anonymous markers, string-symbol `@counter-style` rule resolution, unknown custom-ident decimal fallback, Ethiopic numeric markers, Japanese alphabetic markers, positive `<ol start>` numbering, upper-alpha, lower-greek, latin alias, disclosure markers, `display:list-item` marker generation with implicit `list-item` counter support, including non-`li` children inside list containers, inherited URL, `linear-gradient`, `radial-gradient`, and `conic-gradient` `list-style-image` marker rendering with `none` fallback to `list-style-type`, `::marker` generated content marker overrides, `::marker content:none` marker suppression with `content:normal` fallback, baseline `counter-reset`/`counter-increment` plus `counter(...)`/`counters(...)` generated content over nested reset scopes, duplicate same-name `counter-reset` last-entry behavior before `counters(...)` output, MDN `counter-set` ordering/default-zero behavior, MDN `reversed(...)` automatic initial values for decrementing generated content including first same-scope `counter-set` handling, CSS Lists `display:none`/`display:contents` element counter-mutation suppression and `display:none` pseudo-element counter-mutation suppression, and inherited `list-style-position` inside/outside placement plus `list-style-position`/`list-style-type`/`list-style-image` cascade rollback	Deeper counter-scope/generated-content edge breadth
Overflow	p:`partial` c:`partial` l:`partial` pa:`partial`	`visible`/`hidden`/`clip`/`scroll`/`auto` static clipping and bleed fixtures plus `overflow-x`/`overflow-y` axis combination and logical `overflow-inline`/`overflow-block` static clipping coverage plus overflow cascade rollback	Scroll-container semantics beyond static clipping
Flexbox	p:`partial` c:`partial` l:`partial` pa:`n/a`	Core flex flow/alignment subsets plus fixed-height column-item slicing across pages with continuation-basis reset	Spec edge cases and distribution pressure
Grid	p:`partial` c:`partial` l:`partial` pa:`n/a`	Deterministic baseline placement and repeat counting plus one-column fixed-height auto-row fragmentation and `display: contents` continuation paint propagation	Dedicated solver breadth (autoplacement/track sizing/span)
Tables	p:`partial` c:`partial` l:`partial` pa:`partial`	Table baseline + header repeat across pages + fixed-layout first-row/`<col>` hints, fixed-layout first-row colspan width distribution, fixed-layout over-constrained first-row and `<col>` width preservation, auto-width fallback plus auto-layout colspan and `<col>` minimum-width expansion, `empty-cells`, `border-spacing`, caption-side bottom placement paint for HTML captions and CSS `display:table-caption`, invalid caption-side inheritance behavior, HTML table-row/table-row-group/table-column plus CSS `display:table-row`, `display:table-row-group`, `display:table-column`, and `display:table-column-group` `visibility:collapse` slot removal, CSS `display:table-header-group`/`display:table-footer-group` ordering, collapsed `hidden` border-style conflict suppression, collapsed `inset`/`outset` alias paint, equal-width collapsed border-style precedence, raw-style precedence before collapsed `outset`/`groove` paint aliasing, RTL equal-style cell color/source precedence, collapsed table-level hidden outer border suppression, collapsed row-source border precedence, collapsed rowgroup-source border precedence, collapsed column-source vertical border precedence, and collapsed colgroup-source vertical border precedence	Remaining deeper `table-layout:auto/fixed` pressure edges and broader caption/writing-mode interactions
Transforms and coordinate spaces	p:`partial` c:`partial` l:`n/a` pa:`partial`	2D transforms + transform-origin + composition	3D/perspective breadth
Filters/effects/compositing	p:`partial` c:`partial` l:`partial` pa:`partial`	Effects subset (`filter` foreground group blur, repeated/currentColor/two-length currentColor/color-first/interleaved-color relative-length/two-length negative-offset, MDN color-first rem-offset third-length blur, MDN px-offset hex third-length blur, and MDN negative-mm plus zero-offset rem/named-color third-length blur drop-shadow with modern `rgb()`/named-color and absolute-unit/rem coverage plus duplicate-color, negative-blur, and inset/spread rejection diagnostics, empty optional filter-function defaults including `grayscale()`/`sepia()` full-effect defaults, plus saturate/grayscale/brightness/contrast/invert/sepia/hue-rotate/opacity and cascade rollback, fixture-backed `backdrop-filter` empty optional filter-function defaults including `grayscale()`/`sepia()` full-effect defaults, explicit/currentColor/two-length currentColor/modern-color-order absolute-unit, MDN px-offset hex third-length blur, MDN negative-mm modern-rgb third-length blur, color-first rem-offset third-length blur, repeated, two-length negative-offset, zero-offset rem/named-color third-length blur, semi-transparent third-length blur, and negative-blur and inset/spread fallback diagnostics for drop-shadow plus blur/brightness/contrast/grayscale/hue-rotate/invert/saturate/sepia/opacity-blended adjustment and drop-shadow/blur/saturate/brightness/contrast/invert/sepia/hue-rotate/opacity compute path plus cascade rollback and opacity-, filter-, backdrop-filter-, clip-path-, mask-/mask-image-/mask-border-, mix-blend-mode-, and will-change-established backdrop-root boundary coverage, standard blend-mode keywords plus raster `plus-lighter`/`plus-darker`, element-level `mix-blend-mode` group compositing, element-level `opacity` group compositing, opacity, `mix-blend-mode`, `box-shadow`, and `isolation` cascade rollback, `isolation: isolate` group containment for child blending, clip-path cascade rollback, clip-path inset/circle/ellipse/rect/xywh/polygon/path plus polygon evenodd self-overlap holes and explicit nonzero default-fill behavior, path evenodd holes, explicit nonzero same-winding fills, and `content-box path(...)` reference-origin/order coverage, and shape() line/curve/smooth/arc/relative-command/evenodd move-subpath plus explicit nonzero moved-subpath coverage with margin/border/half-border/padding/content boxes, one-token/four-token circle/ellipse positions, closest/farthest-side circle/ellipse radial extents, circle closest/farthest-corner radial extents, and rounded rect/xywh/reference-box clips)	Remaining function breadth, PDF-native foreground filters, advanced clip-path grammar, and deeper nested compositing/isolation breadth
Multi-column	p:`partial` c:`partial` l:`partial` pa:`partial`	Deterministic single-column fallback contract	True multicol balancing/span/rule semantics
Fragmentation	p:`partial` c:`partial` l:`partial` pa:`n/a`	Core break controls across block/flex/table subsets, including forced `break-before`/`break-after` page aliases, MDN column/region keyword compute, `break-inside` page avoidance, inherited `orphans`/`widows` line-count controls, fixed-height painted-tail slicing without content duplication, positioned-containing-block exclusion, and avoided `figure`/`figcaption` retention	Deeper fragmentation edge behavior
Paged media	p:`partial` c:`partial` l:`partial` pa:`n/a`	Core `@page` + forced break control subsets, including legacy page-break aliases for before/after/inside breaks	Named pages/margin-box breadth
Writing modes and logical properties	p:`partial` c:`partial` l:`partial` pa:`partial`	Horizontal-tb/LTR logical mapping baseline plus `direction: rtl` inherited inline inset, margin/padding, and border remapping; vertical writing-mode `direction: rtl` inline inset remapping; `direction`/`writing-mode` cascade rollback; vertical-rl logical sizing, min/max constraint, positioned inset, margin, padding, and border axis remaps; vertical-lr logical sizing, min/max constraint, inset, margin, padding, and border edge remaps; and basic vertical text-column paint/trace output with `vertical-rl` leftward and `vertical-lr` rightward line progression	Full vertical text/layout flow beyond the current static-layout and basic wrapped text-column subset
Custom properties and API-adjacent parsing	p:`partial` c:`partial` l:`n/a` pa:`n/a`	Deterministic custom-property resolution baseline	Broader API-adjacent grammar/interop lanes

Interpretation:

Fullbleed has broad, validated baseline coverage across all tracked modules.
"Partial" means implemented, fixture-validated subsets with deterministic fallback/diagnostic policy for unsupported forms.
Near-parity for static reporting is practical; full browser-level CSS parity is not yet claimed.

Validated Feature Areas¶

Validated means parser -> evaluator -> calculator -> layout/paint is exercised by tests/fixtures in the current lane.

Syntax/at-rule baseline including typed + unparsed declaration paths, @media print/all/list/not media-type handling, deterministic continuous device-posture matching, deterministic rectangular shape matching, deprecated device-width/device-height/device-aspect-ratio aliases against the paged rendering surface, WebKit extension Boolean media features against static engine support, Level 5 static-output descriptor defaults for environment-blending, nav-controls, and video-color-gamut, WebKit/Mozilla device-pixel-ratio aliases against the deterministic 1dppx reference-pixel density, deterministic progressive matching for scan, deterministic standard visual-output matching for video-dynamic-range, deterministic browser-mode matching for display-mode, CSS reference-pixel density matching for resolution, color-capability queries for color, monochrome, grid, color-index, color-gamut, and dynamic-range, deterministic user-preference defaults for prefers-color-scheme, prefers-reduced-motion, prefers-reduced-transparency, prefers-reduced-data, prefers-contrast, forced-colors, and inverted-colors, deterministic no-input defaults for hover, any-hover, pointer, and any-pointer, single-segment defaults for horizontal-viewport-segments and vertical-viewport-segments, static-output environment defaults for overflow-block, overflow-inline, update, and scripting, width/height media-query gating, paged viewport/page-box aspect-ratio range matching, and orientation matching, @supports feature-query gating for declaration support, selector(...), and not/and/or conditions over the engine-supported subset, @property registered custom-property initial-value, inherits: false, and invalid registered <color>/<length> assignment reset behavior, @starting-style, @keyframes, and @view-transition static-output no-op handling with debug counters, plus @container size-query gating for explicit named/unnamed query containers with container-name, container-type, and container shorthand coverage, and @scope scope-root/scope-limit subtree gating
Cascade and specificity ordering with typed + unparsed declaration paths, including @layer named/anonymous statement/block ordering, unlayered normal priority above layered normal declarations, reversed !important layer priority, and revert-layer current-layer rollback for color, background-color, width, height, box-sizing, display, visibility, position, z-index, direction, writing-mode, opacity, filter, backdrop-filter, clip-path, box-shadow, text-shadow, text-decoration line/color/thickness/style, text underline offset/position, text-overflow, text-indent, letter-spacing, word-spacing, tab-size, text-align, text-align-last, text-justify, text-transform, vertical-align, list-style-position, list-style-type, list-style-image, line-break, hyphens, hyphenate-character, overflow-wrap, word-break, word-wrap, white-space, white-space-collapse, text-wrap, text-wrap-mode, text-wrap-style, overflow, mix-blend-mode, isolation, physical/logical inset offsets, physical/logical margin/padding edges, physical/logical border-color/border-width/border-style edges, outline shorthand plus width/style/color longhands, and outline-offset
Custom properties and var-chain resolution with fallback and cycle-safe behavior
Length math including calc(), min(), max(), clamp(), additive mixed-unit paths
Color value coverage for modern rgb()/rgba(), hsl()/hsla(), and hwb() syntax (space-separated components, slash alpha, percentage channels where applicable, custom-property triplets, and HWB whiteness/blackness normalization), absolute lab()/lch()/oklab()/oklch() and color(srgb ...) alpha preservation, relative color syntax with origin-channel reuse plus custom-property origin/alpha substitution, background-color: currentColor, background: currentColor, and color-mix(in srgb, ...) compatibility coverage for percentage normalization, underfilled alpha multiplier behavior, var() operands, and currentColor
Box model and border propagation, including box-sizing compute and cascade rollback, side-specific border color paint behavior, four-value circular, slash-syntax elliptical, dashed/dotted rounded, double rounded, uniform and non-uniform 3D rounded border-radius background/border paint, outline shorthand outside-border paint, positive/negative outline-offset, dashed/dotted outline-style gaps, double outline two-line separation, groove/ridge/inset/outset shaded square-outline paint, and rounded plus non-uniform groove/ridge/inset/outset 3D outline paint
Positioning baseline (relative, absolute, fixed) with deterministic containing-block behavior plus position, z-index, and inset cascade rollback
Overflow baseline (visible, hidden, clip, scroll, and auto) with static clipping/bleed fixtures plus physical axis and logical overflow-inline/overflow-block clipping coverage plus overflow cascade rollback
Flex baseline including wrapped-line/content alignment subsets
Grid baseline including explicit row/column start placement, repeat track counting, deterministic slot fallback
HTML replaced-content baseline including raster <img> intrinsic dimensions for undimensioned images, intrinsic aspect-ratio preservation when one dimension is authored, object-fit: contain/cover/none/scale-down fitting inside an authored image box, and object-position percentage plus edge-offset alignment
Text/font baseline including inherited text styling, text-overflow: ellipsis gated by clipped overflow plus text-overflow cascade rollback, font-family quoted family names preserved as literal names across var() fallbacks and custom properties while unquoted generic families map to configured generic fallbacks, later font-family: var(...) declarations correctly overriding earlier concrete declarations, font shorthand setting and resetting font-style/font-weight/font-size/line-height/font-family, deterministic system-font keyword fallback, quoted-family semantics, custom-property shorthand values, fallbacks, cycle fallbacks, and later component longhand overrides, line-height normal/unitless/length/percentage behavior, custom-property fallback resolution, invalid negative custom values falling back to inherited line height, and MDN unitless-number inheritance versus computed length inheritance, font-size absolute/relative keywords, percentages, em/rem, custom-property fallback resolution, invalid negative custom values falling back to inherited size, and HTML :root font-size basis for rem, font-weight normal/bold/numeric plus bolder/lighter parent-relative computed resolution with custom-property fallback coverage, font-style normal/italic/oblique <angle> computed resolution with inheritance and custom-property fallback coverage, vertical-align baseline/sub/super/text-top/middle/text-bottom/top/bottom keyword parsing plus var() fallback resolution, table-cell paint placement, and cascade rollback, white-space normal/pre/nowrap/pre-wrap/break-spaces/pre-line parsing with inherited/custom-property/fallback resolution, preserved-space wrapping impact, and cascade rollback, white-space-collapse collapse/preserve/preserve-breaks/preserve-spaces/break-spaces parsing plus modern white-space collapse/wrap shorthand values such as wrap, collapse, and preserve nowrap with cascade rollback, text-wrap shorthand and text-wrap-mode/text-wrap-style longhand parsing for wrap, nowrap, balance, stable, pretty, and avoid-orphans with custom-property fallback, render-time no-wrap behavior independent from whitespace preservation, and cascade rollback, line-break auto/loose/normal/strict/anywhere parsing with inherited/custom-property resolution and anywhere wrapping impact, hyphens none/manual/auto parsing with inherited/custom-property resolution and soft-hyphen wrapping behavior, hyphenate-character auto/string parsing with inherited/custom-property resolution and WebKit-prefixed spelling, plus soft-hyphen marker replacement, word-spacing normal/length/percentage parsing plus cascade rollback, letter-spacing percentage parsing against the element font size with wrapping impact plus cascade rollback, overflow-wrap normal/anywhere/break-word, word-wrap aliasing, and word-break: break-all long-word split behavior plus overflow-wrap, word-wrap, and word-break cascade rollback, text-transform core uppercase/lowercase/capitalize rendering, text-decoration-color currentColor default, longhand, shorthand, custom-property resolution, underline paint coverage, and cascade rollback, text-decoration-line, text-decoration-thickness, text-decoration-style, text-underline-offset, and text-underline-position cascade rollback, text-decoration-thickness length, MDN percentage, shorthand, and custom-property resolution with underline stroke-width paint coverage, text-decoration-style solid/double/dotted/dashed/wavy resolution with underline paint coverage, text-underline-offset auto, length, MDN percentage, negative length, inherited, and custom-property resolution with underline-only paint coverage, text-underline-position auto, under, side-keyword combinations, inherited, and custom-property resolution with horizontal under underline paint coverage, text-shadow offset/blur/color list syntax, inherited/currentColor/custom-property resolution, front-to-back shadow ordering, glyph plus text-decoration paint coverage, and cascade rollback, text-indent length/percentage plus hanging/each-line keyword behavior with wrapping impact and cascade rollback, tab-size number/length/inheritance behavior for preserved tabs and cascade rollback, text-align, text-align-last, and text-justify cascade rollback, text-transform, vertical-align, line-break, hyphens, and hyphenate-character cascade rollback, overflow-wrap, word-wrap, and word-break cascade rollback, white-space, white-space-collapse, text-wrap, text-wrap-mode, and text-wrap-style cascade rollback, text-align-last final/forced-break line alignment, text-align: justify plus text-align-last: justify word-gap distribution, and text-justify auto/none/inter-word/inter-character behavior verified by render-time text trace
Selector and pseudo-element baseline including deterministic selector parser/indexing and ::before/::after string content insertion around inline paragraph text, ::marker generated-content list marker overrides, ::marker content:none marker suppression with content:normal list-style fallback, ::marker suppression on non-list-item origins plus generated marker text on list-container non-li display:list-item children, content: none/normal suppression for generated pseudo-elements, display:none pseudo-element rendering/counter-mutation suppression, generated content: attr(...) resolution from originating element attributes, explicit inherited quotes pairs for open-quote/close-quote with no-output quote keywords, and styled counter(...) plus nested counters(...) generated text backed by counter-reset/counter-increment/counter-set, including duplicate counter-reset last-entry behavior and reversed automatic initial values with same-scope counter-set
Display and formatting baseline including visibility:hidden/collapse paint and render-time text suppression while preserving layout slots, explicit visibility:visible descendants inside hidden ancestors still painting, HTML table-row visibility:collapse removing the row slot while visibility:hidden keeps it, HTML table-row-group group-wide visibility:collapse removing every row even when a child row computes visible, HTML table-column visibility:collapse removing the column slot while preserving non-collapsed column sizing, CSS display:table-row visibility:collapse removing the row slot while visibility:hidden keeps it, CSS display:table-row-group group-wide visibility:collapse removing every row even when a child row computes visible, CSS display:table-header-group/display:table-footer-group ordering before/after body groups, CSS display:table-column visibility:collapse removing the column slot plus display:table-column-group group-wide collapse while preserving non-collapsed column sizing, and CSS display:table-caption honoring caption-side: bottom placement
List rendering baseline including list-style-type marker subset coverage for none marker suppression, square unordered markers, lower-alpha ordered markers, string markers, string-based symbols() anonymous markers for symbolic/cyclic/fixed/numeric/alphabetic systems, string-symbol @counter-style rule resolution for named cyclic/fixed styles with suffix and fixed-start handling, unknown custom-ident counter-style decimal fallback, decimal-leading-zero, lower-roman, upper-roman, Armenian additive markers (armenian, upper-armenian, and lower-armenian), Georgian additive markers, Hebrew additive markers including the 15/16 special cases, broad CSS Counter Styles numeric scripts (arabic-indic, bengali, cambodian/khmer, cjk-decimal, devanagari, gujarati, gurmukhi, kannada, lao, malayalam, mongolian, myanmar, oriya, persian, tamil, telugu, thai, and tibetan), fixed CJK markers (cjk-earthly-branch and cjk-heavenly-stem), Japanese alphabetic markers (hiragana, hiragana-iroha, katakana, and katakana-iroha), Japanese longhand markers (japanese-informal and japanese-formal) with CJK-decimal fallback outside the supported additive range, Korean longhand markers (korean-hangul-formal, korean-hanja-informal, and korean-hanja-formal), Chinese longhand markers (simp-chinese-informal, simp-chinese-formal, trad-chinese-informal, and trad-chinese-formal) with zero-collapse behavior, the MDN cjk-ideographic legacy alias to trad-chinese-informal, Ethiopic numeric markers (ethiopic-numeric) with grouped hundred/myriad separators, positive <ol start> marker numbering, upper-alpha, lower-greek, the lower-latin/upper-latin aliases, disclosure-open/disclosure-closed, display:list-item marker generation with implicit list-item counter support, including non-li children inside list containers, inherited URL, linear-gradient, radial-gradient, and conic-gradient list-style-image marker rendering with none fallback to list-style-type, ::marker generated-content marker overrides, ::marker content:none marker suppression with content:normal fallback, and baseline counter-reset/counter-increment plus styled counter(...), nested counters(...), duplicate reset last-entry behavior, counter-set, and reversed(...) generated content including same-scope counter-set, CSS Lists display:none list-item counter-mutation suppression, display:contents child rendering with wrapper counter-mutation suppression, and display:none pseudo-element counter-mutation suppression, plus inherited list-style-position inside/outside placement, list-style shorthand position reset behavior, and list-style-position/list-style-type/list-style-image cascade rollback
Writing-mode/logical-property baseline including horizontal-tb/LTR logical sizing/inset/margin/padding mapping, horizontal-tb logical overflow mapping, horizontal-tb RTL inline inset/margin/padding/border remapping, vertical writing-mode RTL inline inset remapping, direction/writing-mode cascade rollback with logical side mapping preserved, vertical-rl logical sizing/min-max/inset/margin/padding/border remapping, vertical-lr logical sizing/min-max/inset/margin/padding/border remapping, basic vertical-rl text-column paint/trace output with overflow wrapping into the next leftward vertical line, and basic vertical-lr text-column paint/trace output with overflow wrapping into the next rightward vertical line
Table baseline including split behavior, header repeat coverage across pages, fixed-layout first-row plus <col> width hint behavior, fixed-layout first-row colspan width distribution, fixed-layout over-constrained first-row and <col> width preservation, table-layout: fixed auto-width fallback to auto layout, auto-layout colspan minimum-width expansion beyond undersized authored table width, auto-layout <col> minimum-width expansion beyond undersized authored table width, empty-cells: hide separated-border paint suppression, two-axis border-spacing including outside table edge spacing, caption-side: bottom placement when applied to HTML and CSS table-caption boxes, invalid caption-side values ignored without overriding inherited caption side, HTML table-row/table-row-group/table-column plus CSS display:table-row, display:table-row-group, display:table-column, and display:table-column-group visibility:collapse slot removal, CSS display:table-header-group/display:table-footer-group ordering, collapsed border-style: hidden suppression of conflicting adjacent borders, collapsed inset/outset border-style aliases to ridge/groove, equal-width collapsed border-style precedence, raw-style precedence before collapsed outset/groove paint aliasing, RTL equal-style cell color/source precedence, collapsed table-level hidden outer border suppression, collapsed row-source border precedence, collapsed rowgroup-source border precedence, collapsed column-source vertical border precedence, and collapsed colgroup-source vertical border precedence
Paged-media fragmentation baseline (break-before, break-after, legacy page-break-* aliases, MDN column/region keyword compute, break-inside avoid/avoid-page core paths, and inherited positive-integer orphans/widows controls)
2D transforms (translate, scale, rotate, skew, matrix) with transform-origin and composition model
Background image paint baseline including linear-gradient, radial-gradient, conic gradient support paths, background-image longhand gradient paint, sized no-repeat multi-layer background-image gradient compositing, repeat-x tiling for sized gradient background layers, space/round repeat semantics for sized gradients, explicit-size PNG url(...) background layers, auto-auto intrinsic PNG sizing, invalid negative background-size fallback to intrinsic sizing, contain/cover/auto-dimension/single-value intrinsic-ratio sizing for PNG backgrounds, alpha-stacked PNG url(...) background layers, plus default and explicit repeat repeat, repeat-y, two-axis repeat, repeat no-repeat, no-repeat repeat, single-value space/round, round space, space round, round repeat, round no-repeat, no-repeat round, no-repeat space, space no-repeat, repeat space, repeat round, space repeat, horizontal-tb repeat-inline/repeat-block logical aliases, multi-layer repeat-axis mapping, shorter background size/repeat/position list repetition across layers, percentage, edge-offset, and horizontal-tb logical-alias background-position anchoring for sized PNG backgrounds, shorthand URL position/size/repeat propagation, content-box background-origin/background-clip, multi-layer origin/clip list mapping, background-blend-mode normal/multiply/screen/difference/overlay/exclusion/hard-light/darken/lighten/color-dodge/color-burn/soft-light/hue/saturation/color/luminosity/plus-lighter over element background color, raster PNG background-blend multiply, multi-layer raster and bidirectional mixed raster/gradient background-blend mapping, background-blend-mode list repetition across multiple image layers, and background-blend-mode extra-value truncation
Effects subset with deterministic behavior in current lane: filter: blur(...), repeated/currentColor/two-length currentColor/color-first/interleaved-color relative-length, two-length negative-offset, MDN color-first rem-offset third-length blur, MDN px-offset hex third-length blur, and MDN negative-mm plus zero-offset rem/named-color third-length blur filter: drop-shadow(...) with modern rgb()/named-color and absolute-unit/rem coverage plus duplicate-color, negative-blur, and inset/spread rejection diagnostics, empty optional filter-function argument defaults including grayscale()/sepia() full-effect defaults, filter: saturate(...), filter: grayscale(...), filter: brightness(...), filter: contrast(...), filter: invert(...), filter: sepia(...), filter: hue-rotate(...), filter: opacity(...), and filter cascade rollback
Effects subset with deterministic behavior in current lane: empty optional filter-function defaults including grayscale()/sepia() full-effect defaults, explicit-color, currentColor, two-length currentColor, modern-color-order absolute-unit, MDN px-offset hex third-length blur, MDN negative-mm modern-rgb third-length blur, color-first rem-offset third-length blur, repeated, two-length negative-offset, zero-offset rem/named-color third-length blur, semi-transparent third-length blur, and negative-blur and inset/spread fallback diagnostics for backdrop-filter: drop-shadow(...), blur(...), brightness(...), contrast(...), grayscale(...), hue-rotate(...), invert(...), saturate(...), sepia(...), and opacity-blended adjustment paint coverage plus drop-shadow(...) blur(...) saturate(...) brightness(...) contrast(...) invert(...) sepia(...) hue-rotate(...) opacity(...) compute/raster path coverage, backdrop-filter cascade rollback, and opacity-, filter-, backdrop-filter-, clip-path-, mask-/mask-image-/mask-border-, mix-blend-mode-, and will-change-established backdrop-root boundary coverage
Effects subset with deterministic behavior in current lane: mix-blend-mode standard blend keywords (normal, multiply, screen, overlay, darken, lighten, color-dodge, color-burn, hard-light, soft-light, difference, exclusion, hue, saturation, color, luminosity) plus raster plus-lighter/plus-darker, element-level blend group compositing, element-level opacity group compositing, opacity, mix-blend-mode, and isolation cascade rollback, and isolation: isolate group containment for child blending
Effects subset with deterministic behavior in current lane: clip-path cascade rollback, clip-path: inset(...), clip-path: circle(...), clip-path: ellipse(...) including one-token and four-token edge-offset positions plus closest/farthest-side radial extent keywords and circle closest/farthest-corner radial extents, clip-path: rect(...), clip-path: xywh(...), clip-path: polygon(...) including evenodd self-overlap holes and explicit nonzero default-fill behavior, clip-path: path(...) including evenodd subpath holes, explicit nonzero same-winding fills, and content-box reference-origin coverage for both geometry-box/basic-shape orders, clip-path: shape(...) line/curve/smooth/arc commands, relative by commands, evenodd move-subpath hole behavior, explicit nonzero moved-subpath fill behavior, length-percentage relative control-point anchors, and basic/four-value position keywords, and 1-4 value circular/elliptical round <border-radius> corners for rectangle clips
Effects subset with deterministic behavior in current lane: clip-path visual geometry boxes (margin-box, border-box, half-border-box, padding-box, content-box) alone or combined with supported basic shapes, including rounded reference-box clipping, plus fallback diagnostics for SVG clip sources (url(...)) and standalone SVG-specific geometry boxes (fill-box, stroke-box, and view-box)
Box-shadow baseline with weighted blur hardening, negative spread support, currentColor default/explicit color resolution, multi-shadow list rendering, strict 2-4 length/color grammar rejection for unsupported forms, modern rgb() plus absolute-unit paint coverage, crisp inset spread rings above element backgrounds, softened blurred inset edge paint, directional inset offset edge paint, and cascade rollback

Known Gaps (Active Backlog)¶

These are known, tracked gaps for final parity push:

Broader filter and backdrop-filter function coverage beyond current subset, including SVG url() filters, advanced drop-shadow() forms beyond current flexible-color-order, two-length negative-offset, MDN px-offset hex third-length blur, MDN negative-mm plus zero-offset rem/named-color third-length blur, and negative-blur and inset/spread diagnostic foreground coverage plus explicit/currentColor/modern-color-order, MDN px-offset hex third-length blur, MDN negative-mm modern-rgb third-length blur, color-first rem-offset third-length blur, repeated, two-length negative-offset, zero-offset rem/named-color third-length blur, semi-transparent third-length blur, and negative-blur and inset/spread diagnostic backdrop coverage, and PDF-native foreground filters
Advanced clip-path grammar beyond the current inset(...)/circle(...)/ellipse(...)/rect(...)/xywh(...)/polygon(...)/path(...), line/curve/smooth/arc/relative-command shape(...) plus evenodd holes and explicit nonzero moved-subpath fills, and visual-box subset (SVG clip sources, SVG-specific geometry boxes, and advanced basic-shape edge options)
Plus-lighter PDF-native parity and deeper nested compositing/isolation semantics breadth
Deeper blurred inset shadow edge fidelity parity
Broader outline parity beyond the current solid/dashed/dotted/double, shaded groove/ridge/inset/outset square-outline, and rounded/non-uniform 3D outline baselines, including UA-specific edge fidelity
Broader multi-layer background image compositing semantics beyond the current sized gradient-layer repeat-x/space/round and PNG url(...) explicit-size/auto-auto-intrinsic/negative-size-invalid/contain/cover/auto-dimension-size/single-value-size/alpha-stack/default-repeat-repeat/repeat-y/repeat/repeat-no-repeat/no-repeat-repeat/space-space/round-round/round-space/space-round/round-repeat/round-no-repeat/no-repeat-round/no-repeat-space/space-no-repeat/repeat-space/repeat-round/space-repeat/logical-repeat-aliases/multi-layer-repeat-axis/background-list-repetition/percentage-position/edge-offset-position/logical-position-aliases/shorthand-position-size-repeat/content-box-origin-clip/multi-layer-origin-clip/background-blend-normal/background-blend-multiply/screen-mode/overlay-mode/exclusion-mode/hard-light-mode/darken-mode/lighten-mode/color-dodge-mode/color-burn-mode/soft-light-mode/hue-mode/saturation-mode/color-mode/luminosity-mode/plus-lighter-mode/list-repetition/truncation/raster-blend/raster-layer-mapping/mixed-raster-gradient-mapping/mixed-gradient-raster-mapping subset, including broader mixed raster asset combinations
Table layout and border edge semantics hardening beyond the current fixed-layout width-hint, first-row colspan width distribution, over-constrained first-row and <col> width, auto-width fallback, auto-layout colspan minimum expansion, auto-layout <col> minimum expansion, caption-side bottom, invalid caption-side inheritance, HTML table-row/table-row-group/table-column and CSS display:table-row, display:table-row-group, display:table-column, and display:table-column-group visibility:collapse, collapsed hidden cell conflict, collapsed inset/outset alias, equal-width style-precedence, raw-style alias-precedence, RTL cell color/source, table-level hidden outer-border, row-source, rowgroup-source, column-source, and colgroup-source lanes (deeper table-layout:auto/fixed pressure edges and broader caption/writing-mode interactions)
Writing-mode/direction remapping breadth beyond current horizontal-tb LTR plus fixture-backed RTL inline inset/margin/padding/border, vertical RTL inline inset remapping, vertical-rl logical sizing/min-max/inset/margin/padding/border, vertical-lr logical sizing/min-max/inset/margin/padding/border edges, and basic vertical-rl/vertical-lr wrapped text-column baselines
Advanced color-function breadth beyond the current modern rgb()/rgba(), hsl()/hsla(), hwb(), absolute Lab/Oklab/predefined-color alpha, relative color, and srgb color-mix(...) compatibility lanes

Iteration Progress Snapshot (S14)¶

Resolved during this sprint's visual-iteration loop:

Build-path drift removed by requiring release-feature builds with python,svg_raster before parity diagnosis.
Parser -> evaluator -> calculator path hardened for pending var-length math (calc(var(--x) * scalar) and additive mixed-unit forms).
Empty-element fill paint path revalidated on latest build (no stale-runtime false negatives).
Conic gradients moved from fallback-only behavior to first-class parser + painter support (with deterministic diagnostics retained for unsupported forms).
Property-rule/view-transition/keyframes/starting-style/media-level5-output/media-webkit-extension/media-device-posture/media-shape/media-vendor-pixel-ratio/media-device-alias/media-video-dynamic-range/media-scan/media-resolution/media-display-mode/media-color-range-output/media-viewport-segments/media-input-device-defaults/media-static-output-environment/media-additional-user-preferences/media-user-preferences/media-prefers-color-scheme/media-color-capability/media-type/media-aspect-ratio/media-orientation/scope/container/supports/cascade-layer/revert-layer/border/outline/overflow/overflow-inline/overflow-block/grid/paged-media/fragmentation/color-function/background-image/filter/backdrop-filter/clip-path/blend-mode/isolation/opacity/box-shadow/table-layout/table-border-style/list-marker/list-marker-generated-content/list-marker-content-none/display-list-item/list-container-display-list-item/list-style-position/list-style-type/list-style-image/list-style-image-gradient/list-style-image-radial-conic/cascade-list-style-image/cascade-visibility/table-visibility-collapse/table-rowgroup-visibility-collapse/display-table-rowgroup-visibility-collapse/display-table-header-footer-group-order/display-table-column-visibility-collapse/display-table-caption-side/list-display-none-counter-mutation/display-contents-counter-scope/visibility/generated-content/generated-content-counter/generated-content-counters/generated-content-counter-set/generated-content-duplicate-counter/generated-content-reversed-counter/generated-content-reversed-counter-set/generated-content-pseudo-display-none-counter/text-overflow/font-family/font/line-height/font-size/font-weight/font-style/vertical-align/white-space/white-space-collapse/text-wrap/line-break/hyphens/hyphenate-character/word-spacing/letter-spacing/overflow-wrap/word-break/text-transform/text-decoration-color/text-decoration-thickness/text-decoration-style/text-underline-offset/text-underline-position/text-shadow/text-indent/tab-size/text-align/text-align-last/text-justify/direction/writing-mode/HTML-replaced-content baseline fixture matrix expanded and green in the full fixture lane (86/86 fixtures, 603 assertion/paint checks).

Still open for final parity push:

Effects breadth beyond current subset (filter/backdrop-filter, plus PDF-native foreground filters and deeper nested compositing/isolation breadth).
Clip-path shape breadth beyond the current inset(...)/circle(...)/ellipse(...)/rect(...)/xywh(...)/polygon(...)/path(...), line/curve/smooth/arc/relative-command shape(...), and moved-subpath hole/fill lanes.
Deeper blurred inset shadow edge fidelity.
Broader multi-layer background compositing semantics beyond the current sized gradient-layer repeat-x/space/round and PNG url(...) explicit-size/auto-auto-intrinsic/negative-size-invalid/contain/cover/auto-dimension-size/single-value-size/alpha-stack/default-repeat-repeat/repeat-y/repeat/repeat-no-repeat/no-repeat-repeat/space-space/round-round/round-space/space-round/round-repeat/round-no-repeat/no-repeat-round/no-repeat-space/space-no-repeat/repeat-space/repeat-round/space-repeat/logical-repeat-aliases/multi-layer-repeat-axis/background-list-repetition/edge-offset-position/logical-position-aliases/background-blend-normal/background-blend-multiply/screen-mode/overlay-mode/exclusion-mode/hard-light-mode/darken-mode/lighten-mode/color-dodge-mode/color-burn-mode/soft-light-mode/hue-mode/saturation-mode/color-mode/luminosity-mode/plus-lighter-mode/list-repetition/truncation/raster-blend/raster-layer-mapping/mixed-raster-gradient-mapping/mixed-gradient-raster-mapping subset, including broader mixed raster asset combinations.
Deeper table-layout pressure beyond the current fixed first-row, first-row colspan distribution, <col> precedence, over-constrained first-row and <col> width, auto-width fallback, auto-layout colspan minimum expansion, auto-layout <col> minimum expansion, hidden cell/table, inset/outset alias, equal-width style-precedence, raw-style alias-precedence, RTL cell color/source, row-source, rowgroup-source, column-source, and colgroup-source lanes.
Advanced color-function breadth beyond the current modern rgb()/rgba(), hsl()/hsla(), hwb(), absolute Lab/Oklab/predefined-color alpha, relative color, and srgb color-mix(...) compatibility lanes.

Deterministic Compatibility Contract¶

When CSS is not supported, behavior must be:

Deterministic (no random/non-reproducible geometry or paint drift)
Diagnosable (structured known-loss/fallback signals)
Fixture-covered (repro + regression assertions)

Recent visual stress runs show the effects fallback lane is materially reduced; the primary known-loss signal observed in the current showcase debug output is PAGE_SIZE_OVERRIDDEN for explicit runtime page size precedence.

How To Re-Validate¶

Run from repo root with the project venv:

.\.venv\Scripts\python tools\run_css_fixture_suite.py --labels full --jobs 4 --out _css_working\tmp\fixture_full_latest.json
.\.venv\Scripts\python tools\generate_css_parity_status.py --check --json

Optional visual stress lane:

$env:FULLBLEED_DEBUG='1'
$env:FULLBLEED_PERF='1'
$env:FULLBLEED_FANCY='1'
$env:FULLBLEED_EMIT_PNG='1'
.\.venv\Scripts\python examples\css_visual_charts_showcase\run_example.py

Notes on Bootstrap¶

Bootstrap remains a vendored asset baseline for scaffolded workflows, but Bootstrap preflight screenshots are no longer treated as the canonical coverage definition. Canonical CSS coverage claims are now derived from parity fixtures and status artifacts in _css_working/.