Tasty Style Rules for AI Agents

A compact ruleset for writing correct @tenphi/tasty styles. It is not an API tour — most rules here are machine-checked by @tenphi/eslint-plugin-tasty, so following it generally means clean lint output. The plugin ships separately and can lag a new DSL rule, so treat this page as the source of truth and the plugin as the enforcement that catches most of it. For explanations and the complete API, see Style DSL, Style Properties, React API.

Notation: ❌ wrong → ✅ correct.

Color tokens (#name), custom properties ($name), preset names, recipe names, state aliases (@mobile) and extra units are project-defined in tasty.config.ts or a configure({ … }) call. Look them up before writing styles. Never invent a name — reuse an existing one, or add it to the config.

Only Tasty’s built-ins exist without config: #white, #black, #border, #outline, #current, #clear, and $gap, $radius, $border-width, $outline-width, $transition, $sharp-radius, $bold-font-weight, $icon-size (only where a preset applies), $font-sans-fallback, $font-mono-fallback.

const Card = tasty({ as: 'div', styles: { … }, styleProps: ['padding'] }); // new component
const Hero = tasty(Card, { styles: { … } });                              // extend a component
const cls = useStyles({ … });                                             // ad-hoc class name
tastyStatic('.card', { … });                                              // build-time extraction

• Wrap, don’t pass styles per instance: ❌ <Box styles={{ padding: '2x' }} /> → ✅ const Box = tasty({ styles: { padding: '2x' } }).
• Style values are static. Route anything conditional through a state map plus mods (or tokens / styleProps): ❌ fill: isOpen ? '#primary' : '#surface' → ✅ fill: { '': '#surface', open: '#primary' } with mods={{ open: isOpen }}.
• Keep JavaScript identifiers, calls, computed keys, and interpolated templates out of style values. Use token references inside strings for values supplied at runtime. Spell out style properties rather than spreading objects; if a runtime spread is unavoidable, add a // eslint-disable-next-line tasty/no-style-spread -- reason comment directly above it. tastyStatic() cannot use spreads.

Keys are camelCase — a Tasty property or a real CSS property. No kebab-case, no invented names.

Prefer the Tasty shorthand over its CSS equivalents:

Use logical category styles when layout must follow writing mode or direction: blockSize/inlineSize, blockPadding/inlinePadding, blockMargin/inlineMargin, blockInset/inlineInset, blockScrollMargin/inlineScrollMargin, blockScrollPadding/inlineScrollPadding, and blockBorder/inlineBorder. Use start/end value modifiers; do not replace them with physical sides. Native logical CSS properties remain valid as ordinary keys when an individual declaration is needed.

The last row goes the other way — longhands over the shorthand — because flex is lossy: it resets the components you omit to non-initial values (flex: '0' silently sets flex-basis: 0%) and cannot express flexShrink: 0 at all. The longhands also carry separate state maps.

• ❌ #f5f5f5, rgb(0 0 0), oklch(…), okhsl(…), okhst(…), red → ✅ #surface (add the token to the config if it doesn’t exist).
• CSS system colors (Canvas, CanvasText, Highlight, ButtonText, GrayText, …) are the exception, for forced-colors styles: hold one in a token ('#forced-border': 'CanvasText') or write it under a @media(forced-colors: active) state.
• ❌ var(--gap) → ✅ $gap · ❌ $accent-color → ✅ #accent · ❌ transparent → ✅ #clear · ❌ currentColor → ✅ #current.
• #clear is a default replace token for transparent, so #clear.5 and #clear.$opacity stay transparent. It does not read --clear-color; override it through replaceTokens if needed.
• A $name must be declared as a '$name': value key in the same styles object, or in the config.
• Names are case-sensitive and start lowercase — $myVar → --myVar; a leading capital folds ($Foo → --foo). Prefer kebab-case.
• A $name reference is untyped: it fills the first free slot in a shorthand (border: '1bw $my-style' → the line style). Write colors as #name; $name-color is a fallback for pointing at a raw CSS custom property that holds a color.
• preset and transition take token names, not values, so a $name cannot stand in for one (it warns in dev and is ignored).

Tasty units and their defaults: x 8px spacing step, r 6px radius, cr 10px card radius, bw 1px border width, ow 3px outline width, sf → minmax(0, Nfr). They compile to literal values; change them through units in the config, not with $gap/$radius tokens. All CSS units work too, plus anything in units in the config. Any other unit is an error. Inside @media(…) / @(…) conditions units resolve to their literal length (@media(w < 40x) → width < 320px), unless the project points that unit at a custom property; then write query lengths in px, em, or rem.

Prefer units over raw pixels: 8px → 1x … 64px → 8x; radius: '6px' → '1r'; border: '1px …' → '1bw …'.

❌ calc(100% - 2x) → ✅ (100% - 2x). Parentheses are wrapped in calc() automatically — and must be balanced.

true means “the design-system default” and is accepted only by: border, radius, outline, shadow, padding, margin, gap, inset, width, height, color, fade, preset, font, scrollbar, scrollMargin, scrollPadding, and the enhanced logical category styles listed above, plus hide. Anywhere else it is an error.

Never use it. Tasty owns specificity through doubled selectors and state ordering; !important breaks that. Express the exception as a state instead.

A value is [values…] [modifiers…], and several groups can be comma-separated (later groups override earlier ones). A group that names direction modifiers takes a single value, applied to every direction it names — per-side values come from comma groups. A group naming no direction keeps plain CSS shorthand order (1–4 values). (inset + dock is the one exception: a second value insets the spanned sides.) Only the modifiers a property knows are valid:

Directional modifiers beat placeholder zeros:

• ❌ padding: '0 0 2x 0' → ✅ padding: '2x bottom'
• ❌ padding: '1x 1x 2x 1x' → ✅ padding: '1x, 2x bottom'
• ❌ border: '0 0 1bw 0' — four tokens parse as one border value, so this renders no border at all → ✅ border: '1bw bottom'
• ❌ padding: '2x 4x top right' — a directional group takes one value, so 4x is dropped → ✅ padding: '2x top, 4x right'
• ❌ fade: '3x 1x top bottom' → ✅ fade: '3x top, 1x bottom'

Value-only properties reject both colors and modifiers: gap, columnGap, rowGap, opacity, zIndex, order, flexGrow, flexShrink, flexBasis, aspectRatio, lineClamp, and tabSize. Logical axis category styles accept one or two values in start/end order and the start, end, and longhand modifiers. fill, color, caretColor, and accentColor take a color only (use #clear for transparent). An overlay is a compound color, in any color slot: ❌ fill: '#surface #dark.04' (deprecated overlay layer) · ❌ fill: '#dark.04, #surface' (half-transparent mix) → ✅ fill: '#surface+#dark.04'. Write it as one word, with no spaces around +. Every layer after the first needs an opacity suffix, and its token must be opaque: a translucent layer token, or one that is #clear in some state, leaves the result see-through, so vary the suffix (#surface+#dark.$hover) or the whole compound per state instead. A comma mix in fill is deprecated too: ❌ fill: '#dark 4%, #surface' → ✅ fill: '#surface+#dark.04'. For any other mix, write color-mix() itself: ✅ fill: 'color-mix(in srgb, #dark $weight, #surface)'.

Use semantic names, not CSS property names: fade fill color theme border radius shadow outline preset text gap opacity translate rotate scale filter image background width height zIndex inset.

❌ transition: 'background-color 0.2s' → ✅ transition: 'fill'

Omit the duration to use $fill-transition with $transition as fallback, or use a duration token explicitly (transition: 'fill $transition'). Avoid raw time values in duration slots. An explicit zero can be useful to disable motion.

Use transition when defining a complete transition, and the native CSS animation shorthand when defining a complete animation. Tasty accepts animation directly and tracks local keyframes referenced by it; no special animation handler is needed. Use duration tokens in either form. Keep transitionDuration, animationDuration, and other motion longhands when a state or extension changes only one part of an existing effect. A shorthand resets omitted parts, including an animation’s timeline and range.

A property value can be an object of state: value. Key order is priority — later keys win.

Precedence ! > ^ > | > &; use parentheses to override.

Rules:

1. '' comes first. The bare default is the lowest-priority state. Written later, it triggers a MISPLACED_DEFAULT_STATE warning and Tasty moves it to the front.
2. Every state map needs '' or _ — except when extending (tasty(Parent, …)), where omitting '' merges into the parent’s states and including '' replaces them wholesale.
3. _ is standalone-only and always first (with '' right after it, if present). _ is a never-negated fallback floor for cases where a higher-priority branch may be unknown (@supports, container queries). If a map contains only _ and '', drop the ''.
4. No nested maps: ❌ { hovered: { pressed: 'x' } } → ✅ { 'hovered & pressed': 'x' }
5. State keys never sit at the top level of a styles object — :hover, .active, [open] belong inside a property value.
6. Write keys Tasty can fully read. Names start with a letter (a single letter is fine: x → [data-x]); join states with an operator (hovered & focused, not hovered focused); no space between @media and (. Tasty warns (INVALID_STATE_KEY) and skips what it cannot read.
7. Prefer automatic native states: use disabled, checked, and hidden in Tasty component styles instead of [disabled], [checked], and [hidden]. Tasty sets data-disabled, data-checked, and data-hidden from the native props automatically.

color: { '': '#text', hovered: '#accent', disabled: '#text.40' }

Advanced states:

• At root level write the selector directly: ❌ '@own(:hover)' → ✅ ':hover'.
• @name aliases must exist in states in the config or be declared locally as an '@name': '<state expression>' key; alias keys start with @ and their value must be a valid state expression.
• :is() / :has() / :not() / :where() work in state keys but support at most 2 levels of nested parentheses, and :has() is expensive — prefer @parent(), @own() and modifiers.

When extending a parent’s state map: '@inherit' reuses the parent’s value for that state, null removes a state (or resets a property, letting recipes fill in), false is a tombstone that blocks it entirely.

A capitalized key targets [data-element="Name"], and its value must be a style object.

styles: { Title: { preset: 'h3' }, Icon: { $: '>', color: { '': '#text', '@own(:last-child)': '#accent' } } }

❌ nested-selector keys ('& .title', '&:hover') → ✅ sub-elements and state maps. Use the $ affix property inside a sub-element to control how its selector attaches (> direct child, @ placeholder for the element itself, &::before for a root pseudo-element).

When $ ends in a pseudo-element, @own(…) is the pseudo-element’s own state ('@own(:focus)' → ::part(label):where(:focus)). A pseudo-element has no attributes, classes, or tree position, so @own([open]), @own(hovered), or @own(:first-child) there is ignored with a warning. Put a condition on the element before the pseudo-element in $: $: 'a[rel="next"]::before'.

recipe resolves on the component root and independently in each sub-element’s styles: styles: { Panel: { recipe: 'card elevated' } } is supported. Configured recipe definitions must be flat and cannot contain their own recipe key; references inside recipe values are not recursively expanded. Compose names where the recipe is applied, not inside configure({ recipes }). See Recipes.

At-rule keys match the real CSS at-rule names, so they are kebab-case, not camelCase. Inside @function, the callable is $$name but its parameters and local variables are $name:

styles: {
  '@function': { $$negative: { args: ['$value'], result: '(-1 * $value)' } },
  margin: '$$negative(2x) top',
}

The selector must be a string literal and valid CSS. Values must be static — strings, numbers, booleans, null, or objects/arrays of those. No variables, template literals, function calls, or spreads.

• Token, preset, recipe, unit and @alias names exist in the project config.
• Tasty shorthand chosen over CSS longhands; flexGrow/flexShrink/flexBasis over flex; hide: true over display: 'none'.
• Logical category styles keep native block/inline declarations and accept start/end, never physical direction modifiers.
• Colors are #tokens, not hex/rgb/oklch/named; $prop not var(--prop).
• Spacing uses x/r/bw/ow units; math uses (…), not calc(…).
• true only on the properties that accept it; no !important.
• Modifiers valid for the property; directional shorthand instead of placeholder zeros.
• Every state map starts with '' (or _), is flat, and lives inside a property value.
• @own() only inside sub-elements; sub-element keys are capitalized and hold objects.
• At-rule keys are kebab-case (@property, @font-face, @counter-style, @function); @function names use $$, their args and locals use $.
• Values are static; dynamic behavior comes from mods / tokens / styleProps.