Catalog

Every widget below is generated from the parity manifest that melos fortal:parity:check holds against the Dart recipes, so the sizes, variants, and defaults on this page are the ones a caller actually gets.

This is the API reference. Start with the Fortal overview for installation and theming. For live examples and source, choose a component in the sidebar, such as Button.

A — value means the widget does not expose that axis. When values are listed but their default is —, the parameter is nullable with no pinned value. That is the typography path: an omitted size or weight resolves from the active scope's tokens (text3, regular) rather than from an enum, so a host text run cannot resize Fortal text. See Typography.

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At a glance

Actions and inputs

FortalButton

Radix Button · recipe registry_source/lib/src/fortal/components/button.dart

Named constructors: FortalButton.classic, FortalButton.ghost, FortalButton.outline, FortalButton.soft, FortalButton.solid, FortalButton.surface

Other defaults: enabled: true, highContrast: false, loading: false

Style props: color, radius, highContrast

States: idle, hovered, pressed, focused, disabled, loading, highContrast

Flutter differences:

• The visual recipe maps Radix size, variant, and states onto the established required-label Remix button; arbitrary child content is deferred.

Not covered:

• arbitrary child content

FortalIconButton

Radix IconButton · recipe registry_source/lib/src/fortal/components/icon_button.dart

Named constructors: FortalIconButton.classic, FortalIconButton.ghost, FortalIconButton.outline, FortalIconButton.soft, FortalIconButton.solid, FortalIconButton.surface

Other defaults: enabled: true, highContrast: false, loading: false, semanticLabel: required

Style props: color, radius, highContrast

States: idle, hovered, pressed, focused, disabled, loading, highContrast

Flutter differences:

• A required semanticLabel supplies the accessible name that icon-only DOM buttons receive from aria-label.

FortalCheckbox

Radix Checkbox · recipe registry_source/lib/src/fortal/components/checkbox.dart

Named constructors: FortalCheckbox.classic, FortalCheckbox.soft, FortalCheckbox.surface

Other defaults: enabled: true, highContrast: false, selected: false, tristate: false

Style props: color, highContrast

States: unchecked, checked, indeterminate, hovered, pressed, focused, disabled, highContrast

Flutter differences:

• Nullable bool plus tristate maps the Radix indeterminate checked state.

FortalRadio

Radix RadioGroup.Item · recipe registry_source/lib/src/fortal/components/radio.dart

Named constructors: FortalRadio.classic, FortalRadio.soft, FortalRadio.surface

Other defaults: enabled: true, highContrast: false

Style props: color, highContrast

States: unchecked, checked, hovered, pressed, focused, disabled, highContrast, group

Flutter differences:

• RemixRadioGroup provides typed Flutter group semantics and selection coordination.

FortalSelect

Radix Select · recipe registry_source/lib/src/fortal/components/select.dart

Named constructors: FortalSelect.ghost, FortalSelect.soft, FortalSelect.surface

Other defaults: contentHighContrast: false, open: null

Style props: color, radius, highContrast

States: closed, open, placeholder, selected, highlighted, disabled, highContrast

Flutter differences:

• The visual recipe maps supported Radix states onto the established data-driven RemixSelectItem list and single historical variant.

Not covered:

• structured content
• independent trigger/content variants

FortalSlider

Radix Slider · recipe registry_source/lib/src/fortal/components/slider.dart

Named constructors: FortalSlider.classic, FortalSlider.soft, FortalSlider.surface

Other defaults: highContrast: false, inverted: false, max: 100, min: 0, minSpacing: 0, step: 1

Style props: color, radius, highContrast

States: idle, hovered, pressed, focused, disabled, highContrast, rtl

Flutter differences:

• The visual recipe maps Radix styling onto the established scalar horizontal slider; range and multi-thumb behavior is deferred.

Not covered:

• multiple thumbs
• range values
• vertical orientation
• inversion

FortalSwitch

Radix Switch · recipe registry_source/lib/src/fortal/components/switch.dart

Named constructors: FortalSwitch.classic, FortalSwitch.soft, FortalSwitch.surface

Other defaults: enabled: true, highContrast: false, selected: false

Style props: color, radius, highContrast

States: unchecked, checked, hovered, pressed, focused, disabled, highContrast

Flutter differences:

• Boolean selection and Flutter focus/feedback APIs replace DOM checked attributes and events.

FortalTextArea

Radix TextArea · recipe registry_source/lib/src/fortal/components/textfield.dart

Named constructors: FortalTextArea.classic, FortalTextArea.soft, FortalTextArea.surface

Other defaults: enabled: true, error: false, maxLines: null, readOnly: false

Style props: color, radius

States: idle, hovered, focused, disabled, readOnly, invalid

Flutter differences:

• TextArea reuses the shared TextField visual-state helpers while retaining multiline minimum heights, start alignment, and distinct padding; its soft placeholder remains accent-12 at 0.65 opacity.
• Native invalid semantics remain in parity coverage. Remix's red error treatment is a Fortal extension rather than an upstream TextArea visual state.
• Flutter text-editing flags, constraints, and platform scrolling replace textarea DOM attributes, CSS sizing, the themed 12px browser scrollbar, and the browser resize handle.

Not covered:

• browser resize handle and resize-axis prop
• themed 12px browser scrollbar and fixed CSS textarea overflow behavior
• responsive size, radius, and resize objects

Documented approximations:

• Flutter's editable text contract has no cross-platform browser resize-handle primitive.
• Flutter's line and constraint model replaces CSS block sizing and native textarea overflow behavior.

FortalTextField

Radix TextField.Root · recipe registry_source/lib/src/fortal/components/textfield.dart

Named constructors: FortalTextField.classic, FortalTextField.soft, FortalTextField.surface

Other defaults: enabled: true, error: false, readOnly: false

Style props: color, radius

States: idle, hovered, focused, disabled, readOnly, invalid, leading, trailing

Flutter differences:

• Native invalid semantics remain part of the upstream coverage. Remix's error flag is a Fortal extension that adds red error and focus roles while setting those invalid semantics; Flutter text editing APIs replace input DOM props.

FortalToggle

Fortal extension (no Radix counterpart) · recipe registry_source/lib/src/fortal/components/toggle.dart

Named constructors: FortalToggle.ghost, FortalToggle.outline

Other defaults: enabled: true, highContrast: false, selected: false

Style props: color, radius, highContrast

States: off, on, hovered, pressed, focused, disabled, highContrast

Flutter differences:

• Fortal extension: excluded from the Radix parity score and styled from shared Fortal tokens.

FortalToggleGroup

Fortal extension (no Radix counterpart) · recipe registry_source/lib/src/fortal/components/toggle_group.dart

Named constructors: FortalToggleGroup.soft, FortalToggleGroup.surface

Other defaults: enabled: true, highContrast: false, loop: true

Style props: color, radius, highContrast

States: unselected, selected, hovered, pressed, focused, disabled, highContrast, rtl

Flutter differences:

• Fortal extension: excluded from the Radix parity score and styled from shared Fortal tokens.

Navigation

FortalLink

Radix Link · recipe registry_source/lib/src/fortal/components/link.dart

Other defaults: autofocus: false, enableFeedback: true, enabled: true, excludeSemantics: false, highContrast: false, softWrap: true, truncate: false

Style props: color, radius, highContrast

States: idle, hovered, focused, disabled, highContrast, inert, truncated, semantic

Flutter differences:

• Every upstream underline rule is gated behind :where(:any-link, button), so a FortalLink with no onPressed is disabled exactly as enabled: false is: it keeps the accent colour but gives up its underline, focus stop, link role, and activation.
• An omitted size resolves the text3 token rather than inheriting the ambient 1em run.
• An omitted weight stays unset on a non-inheriting Flutter TextStyle and therefore uses the engine's regular weight rather than the ambient weight.
• text-underline-offset has no Flutter TextStyle equivalent, so the underline sits at the font's own offset.
• Flutter reads decorationThickness as a multiple of the font underline thickness rather than a CSS length, so the pinned min(2px, max(1px, 0.05em)) ramp lands as a 1x–2x stroke.
• The decoration colour approximates Radix color-mix(in oklab, …) with an sRGB Color.lerp.
• A focus-visible outline replaces the underline rather than stacking both, matching the upstream text-decoration-line: none override.
• linkUrl is assistive metadata only and is never launched; navigation stays the caller responsibility in onPressed.
• Radix wrap covers pretty and balance line breaking; Flutter exposes no equivalent line breaker, so the recipe maps only the wrap/nowrap pair onto softWrap and folds truncate into one ellipsized line.
• CSS leading trim has no Flutter primitive, so the token line box is painted untrimmed.

Not covered:

• asChild element polymorphism
• responsive size, weight, trim, and wrap objects
• pretty and balance text wrapping
• leading trim
• per-instance color prop: callers re-scope FortalScope.accent
• text-underline-offset
• the coarse-pointer active tap highlight
• the transparent underline when the only child is a non-ghost Code
• URL launching: onPressed owns navigation

Documented approximations:

• Flutter expresses decorationThickness as a multiple of the font underline thickness and offers no underline-offset property.
• Flutter has no OKLab colour-mix primitive, and shipping one for a single decoration colour is outside the recipe contract.

FortalMenu

Radix DropdownMenu · recipe registry_source/lib/src/fortal/components/menu.dart

Named constructors: FortalMenu.soft, FortalMenu.solid

Other defaults: highContrast: false, submenuOpenDelayMilliseconds: 100

Style props: color, highContrast

States: closed, open, highlighted, disabled, checked, unchecked, submenuOpen, rtl, escape, focusRestored, highContrast

Flutter differences:

• Checkbox, radio, and submenu behavior delegates to the pinned Naked beta.8 primitives; Remix uses one standard leading flex slot and normal item spacing instead of Radix's CSS-specific absolute row geometry.

Not covered:

• compositional items

Documented approximations:

• Standard MenuItemStyler flex, padding, and spacing keep the layout reusable and avoid menu-only public gutter and offset APIs.

FortalSegmentedControl

Radix SegmentedControl.Root · recipe registry_source/lib/src/fortal/components/segmented_control.dart

Named constructors: FortalSegmentedControl.classic, FortalSegmentedControl.surface

Other defaults: enabled: true, loop: true, orientation: horizontal

Style props: radius

States: unselected, selected, hovered, pressed, focused, disabled, rtl

Flutter differences:

• The standard Remix item-state styler maps the track, inactive and selected labels, selected inset fill, surface ring or five-layer classic shadow, focus outline, and disabled precedence without a Fortal-specific widget.
• Vertical orientation and per-item disabling are Remix extensions; looping focus traversal and RTL direction remain constructor and Naked coordinator behavior.

Not covered:

• 100 ms translated sliding indicator
• duplicate inactive and active labels with opacity crossfade
• CSS separators between inactive items
• selection-dependent intrinsic-width stability when callers change an item label with the selection
• responsive size and radius objects

Documented approximations:

• A shared translated indicator requires a Fortal-specific render or widget layer outside the plain-styler recipe contract.
• Duplicate labels would require private stacked label widgets instead of the component's standard LabelStyleMixin surface.
• Conditional between-item pseudo-elements are not expressible through the standard item styler without a segmented-control-specific widget API.
• The equal-segment render layout shrinks to the incoming constraints rather than forcing an overflow, so a wrapped label would be clipped by the pinned track height.

FortalTabBar

Radix Tabs · recipe registry_source/lib/src/fortal/components/tabs.dart

Other defaults: highContrast: false

Style props: color, highContrast

States: inactive, active, hovered, pressed, focused, disabled, automatic, manual, rtl, highContrast

Flutter differences:

• The visual recipe maps Radix tab states onto the established single-child TabBar.

Not covered:

• wrapping tab bars
• tab-bar justification

Overlays

FortalDialog

Radix Dialog.Content · recipe registry_source/lib/src/fortal/components/dialog.dart

Other defaults: maxWidth: 600, modal: true, width: infinity

States: closed, open, modal

Flutter differences:

• The mapped upstream align values start and center use Alignment.topCenter and Alignment.center in Flutter. The align parameter accepts any AlignmentGeometry, including physical and directional bottom positions, while preserving viewport insets.
• Logical-pixel BoxConstraints replace CSS width and height strings; inherited Fortal and Mix scopes are replayed through Navigator overlays; modal controls accessibility route scoping while the Flutter Navigator route remains pointer-modal.

Documented approximations:

• Flutter Navigator dialog routes are modal routes; non-modal pointer interaction requires a separate OverlayEntry lifecycle rather than the current dialog route API.

FortalPopover

Radix Popover.Content · recipe registry_source/lib/src/fortal/components/popover.dart

Other defaults: arrow: false, maxWidth: 480

States: closed, open, escape, outsideTap, focusRestored

Flutter differences:

• A separate anchor Widget and OverlayPositionConfig replace Radix anchor and collision props; Fortal intentionally renders no Popover arrow.

FortalTooltip

Radix Tooltip · recipe registry_source/lib/src/fortal/components/tooltip.dart

Other defaults: arrow: true, collisionPadding: 10, delayMilliseconds: 200, disableHoverableContent: false, maxWidth: 360, sideOffset: 4

States: closed, delayedOpen, triggerHovered, focused, touch, escape

Flutter differences:

• OverlayPositionConfig and resolved OverlayPlacement drive a CustomPaint arrow after collision resolution; width constraints use logical pixels.

Feedback

FortalCallout

Radix Callout.Root · recipe registry_source/lib/src/fortal/components/callout.dart

Named constructors: FortalCallout.outline, FortalCallout.soft, FortalCallout.surface

Other defaults: highContrast: false

Style props: color, highContrast

States: idle, highContrast

Flutter differences:

• Widget icon/content slots replace the upstream compound React nodes.

FortalProgress

Radix Progress · recipe registry_source/lib/src/fortal/components/progress.dart

Named constructors: FortalProgress.classic, FortalProgress.soft, FortalProgress.surface

Other defaults: durationMilliseconds: 5000, highContrast: false, max: 100, value: null

Style props: color, radius, highContrast

States: determinate, highContrast

Flutter differences:

• The visual recipe maps Radix styling onto the established normalized determinate progress value.

Not covered:

• indeterminate mode
• custom maximum
• animation controls

FortalSkeleton

Radix Skeleton · recipe registry_source/lib/src/fortal/components/skeleton.dart

Other defaults: loading: true

States: loading, loaded, animationDisabled

Flutter differences:

• Responsive CSS width and height props map to caller-owned Flutter constraints or child geometry; the Fortal recipe supplies only the pinned childless minimum height, surface, radius, and pulse timing.
• RemixSkeleton owns loading semantics and reduced-motion behavior, so the recipe adds no semantic or motion logic.

Not covered:

• responsive width and height props: callers use Flutter constraints, responsive builders, or child geometry

Documented approximations:

• The shared Flutter phase controller uses the resolved container color as its stable initial and resting value.

FortalSpinner

Radix Spinner · recipe registry_source/lib/src/fortal/components/spinner.dart

Other defaults: color: currentColor, leafCount: 8, loading: true

States: spinning, animationDisabled

Flutter differences:

• A leaf painter maps the Radix spinner geometry; loading gates and child overlays are deferred.

Not covered:

• loading gate
• child overlay

Layout

FortalAccordion

Fortal extension (no Radix counterpart) · recipe registry_source/lib/src/fortal/components/accordion.dart

Named constructors: FortalAccordion.soft, FortalAccordion.surface

Other defaults: enabled: true

Style props: color, radius

States: collapsed, expanded, hovered, pressed, focused, disabled

Flutter differences:

• Fortal extension: excluded from the Radix parity score and styled from shared Fortal tokens.
• Panel anatomy (container radius, border, fill, and clipping) has no Radix Accordion source of its own — Radix Themes ships none — and instead derives from the mapped Table family's container/row-divider treatment (see data_table.dart).

FortalCard

Radix Card · recipe registry_source/lib/src/fortal/components/card.dart

Named constructors: FortalCard.classic, FortalCard.ghost, FortalCard.surface

Other defaults: enabled: true

States: idle, passive

Flutter differences:

• The visual recipe maps Radix size and variant onto the established passive Remix card.

Not covered:

• interactive card behavior

FortalDisclosure

Radix Collapsible · recipe registry_source/lib/src/fortal/components/disclosure.dart

Named constructors: FortalDisclosure.soft, FortalDisclosure.surface

Other defaults: defaultExpanded: false, enabled: true, expanded: null

Style props: color, radius

States: collapsed, expanded, hovered, pressed, focused, disabled

Flutter differences:

• Radix Primitives calls this component Collapsible; Remix uses the WAI-ARIA/Naked UI name Disclosure with trigger and content slots on one widget.
• Radix Themes 3.3.0 ships no styled Collapsible, so Fortal treats the recipe as an extension and derives its panel treatment from the mapped Table family.

Not covered:

• Radix Collapsible.Content forceMount has no NakedDisclosure equivalent.

FortalDivider

Radix Separator · recipe registry_source/lib/src/fortal/components/divider.dart

Other defaults: color: gray, decorative: true, lengths: [16, 32, 64, full], thickness: 1

Style props: color

States: decorative, semantic

Flutter differences:

• Axis and separator Semantics replace DOM orientation and role attributes.

Data display

FortalAvatar

Radix Avatar · recipe registry_source/lib/src/fortal/components/avatar.dart

Named constructors: FortalAvatar.soft, FortalAvatar.solid

Other defaults: highContrast: false

Style props: color, radius, highContrast

States: idle, loading, loaded, error, highContrast

Flutter differences:

• ImageProvider and Widget fallback replace DOM src/fallback nodes; no ring prop is exposed.

FortalBadge

Radix Badge · recipe registry_source/lib/src/fortal/components/badge.dart

Named constructors: FortalBadge.outline, FortalBadge.soft, FortalBadge.solid, FortalBadge.surface

Other defaults: highContrast: false

Style props: color, radius, highContrast

States: idle, highContrast

Flutter differences:

• Arbitrary Widget content uses DefaultTextStyle and IconTheme; there is no dedicated icon API.

FortalDataList

Radix DataList.Root · recipe registry_source/lib/src/fortal/components/data_list.dart

Other defaults: highContrast: false

Style props: highContrast

States: idle, highContrast, customChild, rtl

Flutter differences:

• A data-driven RemixDataList maps Radix's shared horizontal label column, vertical stacking, row and column gaps, item alignment, label minimum, typography, and high-contrast label role without claiming the upstream compositional child API.
• The constructor owns orientation and each RemixDataListItem owns alignment; the recipe exposes only size and global highContrast.

Not covered:

• compositional Root, Item, Label, and Value child API
• per-label color, highContrast, and width props
• responsive orientation, size, align, trim, and width objects
• CSS leading trim and value-edge negative margins

Documented approximations:

• The Remix API guarantees one shared label column and deterministic list semantics through a data model rather than arbitrary child anatomy.
• The data-driven RemixDataList has one shared label styler and shared column width, with no per-label visual-prop surface.
• Responsive CSS-object syntax is a framework-level adaptation already owned by Flutter layout builders.
• Flutter has no CSS leading-trim primitive, and offset arithmetic is outside the plain-styler recipe contract.

FortalDataTable

Radix Table · recipe registry_source/lib/src/fortal/components/data_table.dart

Named constructors: FortalDataTable.ghost, FortalDataTable.surface

Other defaults: enabled: true

States: idle, passive, hovered, selected

Flutter differences:

• The mapped family is named data_table publicly but cites Radix Table. The recipe maps size and variant onto cell padding, minimum cell height, typography, radius, the gray-a5 row divider, bold column headers, and the surface panel, border, gray-a2 header background, and suppressed last-row divider.
• Radix Table is a passive layout. Controlled sorting, page-scoped selection, pagination, row hover, arbitrary row actions, and horizontal scrolling are Flutter and Fortal extensions with no Radix counterpart, built from existing accent and gray control tokens.
• Radix row-header cells use normal weight, but Flutter 3.44 exposes no row-header semantics role and the v1 data-driven API carries no row-header model, so .rt-TableRowHeaderCell is cited and deferred instead of fabricated.
• Row background and divider are painted per cell exactly as .rt-TableCell does upstream, because Flutter's Table has no widget between the table and its cells.

Not covered:

• row-header cells (.rt-TableRowHeaderCell): Flutter has no row-header semantics role and the v1 data-driven API has no row-header model
• responsive size and layout objects: Radix resolves breakpoints in CSS while Flutter callers rebuild with a different size
• per-row align and per-cell width, min-width, max-width, and padding props: expressed as column-level TableColumnWidth, column alignment, and cell widgets instead
• layout auto versus fixed: RenderTable always negotiates one shared column map

Typography

FortalHeading

Radix Heading · recipe registry_source/lib/src/fortal/components/heading.dart

Other defaults: accent: false, align: null, excludeSemantics: false, headingLevel: 1, highContrast: false, softWrap: true, truncate: false

Style props: color, highContrast

States: idle, accent, highContrast, truncated, semantic

Flutter differences:

• Radix as selects an h1–h6 element that carries the visual and the semantic level together; Flutter splits them, so headingLevel drives a Semantics header node while size stays purely visual.
• --heading-font-size-adjust is 1, so headings reuse the raw token size and differ from body text only in the pinned line box.
• A neutral FortalHeading resolves gray-12 rather than inheriting the ambient foreground; accent is an explicit opt-in.
• Radix wrap covers pretty and balance line breaking; Flutter exposes no equivalent line breaker, so the recipe maps only the wrap/nowrap pair onto softWrap and folds truncate into one ellipsized line.
• CSS leading trim has no Flutter primitive, so the token line box is painted untrimmed.

Not covered:

• as and asChild element polymorphism
• responsive size, weight, align, trim, and wrap objects
• pretty and balance text wrapping
• leading trim
• per-instance color prop: callers re-scope FortalScope.accent

FortalText

Radix Text · recipe registry_source/lib/src/fortal/components/text.dart

Other defaults: accent: false, align: null, highContrast: false, softWrap: true, truncate: false

Style props: color, highContrast

States: idle, accent, highContrast, truncated

Flutter differences:

• An omitted size and weight resolve the text3 and regular tokens, and neutral text resolves gray-12, rather than inheriting the ambient DefaultTextStyle. This deliberately differs from an unsized Radix Text rendering at 1em; an explicit size selects another token.
• The as element choice and asChild map to Flutter widget composition; FortalText always renders exactly one Text node.
• Radix wrap covers pretty and balance line breaking; Flutter exposes no equivalent line breaker, so the recipe maps only the wrap/nowrap pair onto softWrap and folds truncate into one ellipsized line.
• CSS leading trim has no Flutter primitive, so the token line box is painted untrimmed.
• Radix align accepts left, center, and right; the recipe forwards Flutter's TextAlign so start and end are also reachable.

Not covered:

• as and asChild element polymorphism
• responsive size, weight, align, trim, and wrap objects
• pretty and balance text wrapping
• leading trim
• per-instance color prop: callers re-scope FortalScope.accent

FortalCode

Radix Code · recipe registry_source/lib/src/fortal/components/code.dart

Named constructors: FortalCode.ghost, FortalCode.outline, FortalCode.soft, FortalCode.solid

Other defaults: accent: false, highContrast: false, softWrap: true, truncate: false

Style props: color, radius, highContrast

States: idle, accent, highContrast, truncated

Flutter differences:

• Radix renders Code as an inline element inside a text run; RemixBadge paints a standalone box, so a Code inside a wrapped sentence is a sibling widget rather than an inline span.
• An omitted size anchors the upstream Code factors to the text3 token rather than the ambient 1em run.
• --code-font-weight: inherit becomes an optional weight argument. When omitted, the non-inheriting Flutter TextStyle leaves weight unset and therefore uses the engine's regular weight rather than the ambient weight.
• Ghost uses the ambient foreground as a post-composition fallback unless the caller opts into the local accent, matching the upstream [data-accent-color] gate while allowing an explicit recipe foreground to win.
• The Link-nested hover, solid high-contrast hover filter, and ::selection rules need an actionable ancestor FortalCode never has.
• Radix wrap covers pretty and balance line breaking; Flutter exposes no equivalent line breaker, so the recipe maps only the wrap/nowrap pair onto softWrap and folds truncate into one ellipsized line.
• CSS leading trim has no Flutter primitive, so the token line box is painted untrimmed.

Not covered:

• asChild element polymorphism
• responsive size and wrap objects
• pretty and balance text wrapping
• per-instance color prop: callers re-scope FortalScope.accent
• inline flow inside a surrounding text run
• actionable Code hover, filter, and ::selection treatments

FortalKbd

Radix Kbd · recipe registry_source/lib/src/fortal/components/kbd.dart

Named constructors: FortalKbd.classic, FortalKbd.soft

Other defaults: excludeSemantics: false

Style props: radius

States: idle, explicitDark, semantic

Flutter differences:

• Radix uses two type-scale factors: an explicit size multiplies its token by 0.8, while an unsized Kbd renders at 0.75em. Fortal keeps those factors but anchors an omitted size to the text3 token rather than the ambient DefaultTextStyle. Because --letter-spacing-N is an em, an explicit size also re-resolves its letter spacing against Kbd's own 0.8 font size.
• The unsized path keeps the text3 token's resolved letter spacing instead of inheriting the ambient DefaultTextStyle's absolute value.
• vertical-align: text-top positions the cap inside a surrounding text run; a standalone Flutter box has no inline baseline to align against.
• The hover, open, active, and focus-visible rules apply only when Kbd is nested in an anchor or button, which FortalKbd never is.
• Kbd publishes one native keyboardKey Semantics node and no tap action, because it is inert upstream.

Not covered:

• asChild element polymorphism
• responsive size objects
• the -0.03em vertical nudge and text-top inline alignment
• actionable Kbd hover, open, active, and focus-visible treatments

Documented approximations:

• A transform wrapper for a sub-pixel baseline tweak sits outside the plain-styler recipe contract, and a standalone Flutter box has no inline text run to align against.

Audited, not mapped

These upstream families are tracked deliberately rather than missed. Each names the Remix composition that covers it today and the condition that would reopen it.

Radix CheckboxGroup

• Why not mapped: RemixCheckboxGroup deliberately owns no visual or root-layout anatomy, so generating a FortalCheckboxGroup wrapper would invent a root style surface that the underlying coordinator does not have. FortalCheckboxGroupItem maps the item-level typography, label gap, and checkbox visuals independently.
• Use instead: Use RemixCheckboxGroup for selection, roving focus, semantics, and layout transparency; render each option as FortalCheckboxGroupItem(size:, variant:, highContrast:), which maps the checkbox recipe, size-linked text1/text2/text3 label typography, and scaled 6/7/8 item-label gaps. The caller continues to own root direction and spacing. Callers that need a per-item override can pass a CheckboxStyler to RemixCheckboxGroupItem.style directly.
• Reopens when: Map the remaining root contract only if RemixCheckboxGroup gains layout anatomy that can express the pinned root direction and gap without a Fortal-only wrapper.