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.

0. Read the project config first

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.

1. Where styles go

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, zero runtime

• 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 }}.

2. Property names

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:

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.

3. Values

Tokens

• ❌ #f5f5f5, rgb(0 0 0), oklch(…), okhsl(…), red → ✅ #surface (add the token to the config if it doesn't exist).
• ❌ var(--gap) → ✅ $gap · ❌ $accent-color → ✅ #accent · ❌ transparent → ✅ #clear · ❌ currentColor → ✅ #current.
• A $name must be declared as a '$name': value key in the same styles object, or in the config.

Units

Tasty units: x (gap multiple), r (radius), cr (card radius), bw (border width), ow (outline width), sf (minmax(0, Nfr)). All CSS units work too, plus anything in units in the config. Any other unit is an error.

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

Math

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

true

true means "the design-system default" and is accepted only by: border, radius, outline, shadow, padding, margin, gap, inset, width, height, fill, color, fade, preset, font, scrollbar, hide. Anywhere else it is an error.

!important

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

Modifiers

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, tabSize, paddingInline, paddingBlock. fill and color take a color (plus none / transparent); caretColor and accentColor take a color only.

transition

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 flow dimension.

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

4. State maps

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; placing it later would override everything above it.
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.

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.

5. Sub-elements

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

styles: { Title: { preset: 'h3' }, Icon: { $: '>@:last-child', color: '#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).

6. Special top-level keys

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': { $$negative: { args: ['$value'], result: '(-1 * $value)' } },
  marginTop: '$$negative(2x)',
}

7. tastyStatic()

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.

8. Checklist

• 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'.
• 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.