UI Design System Enforcement

This skill enforces consistency across all application UI. It is the default for all app interface work — dashboards, forms, settings, CRUD, data display. For creative/marketing work, use ultra-frontend instead.

Hard Rules

1. shadcn-svelte first. Never build custom components when shadcn-svelte has one. Before creating anything, check src/lib/components/ui/ for existing components.
2. Theme tokens only. Use CSS variables (bg-primary, text-muted-foreground, border-border) — never raw Tailwind colors (bg-blue-500, text-gray-500). See the Color section below.
3. Scan before building. Before creating any new page or component, find and read an existing similar one in the project. Match its structure, spacing, and patterns. State what you're matching.
4. One way to do things. If the project already does X a certain way, do it that way. Don't introduce a second pattern.
5. Svelte 5 only. Use $state, $derived, $bindable, $props, snippets. No legacy Svelte 4 patterns (stores, export let, slots).

Pre-Build Checklist

Before writing any UI code:

1. Glob for similar existing pages/components in the project
2. Read at least one to understand established patterns
3. State which patterns you're following and why
4. Check src/lib/components/ui/ for relevant shadcn components
5. If no similar code exists, state the conventions you'll establish and why

Colors & Theme Tokens

Always Use Semantic Tokens

bg-background, bg-foreground
bg-primary, text-primary, bg-primary-foreground
bg-secondary, text-secondary
bg-muted, text-muted-foreground
bg-accent, text-accent-foreground
bg-destructive, text-destructive
bg-success, text-success
border-border, border-input
ring-ring

Status Colors — Use Semantic Tokens with Opacity

<!-- CORRECT -->
<span class="bg-success/10 text-success">Active</span>
<span class="bg-destructive/10 text-destructive">Failed</span>
<span class="bg-warning/10 text-warning">Pending</span>
<span class="bg-muted text-muted-foreground">Draft</span>

<!-- WRONG — raw Tailwind colors -->
<span class="bg-green-100 text-green-700">Active</span>
<span class="bg-red-100 text-red-700">Failed</span>
<span class="bg-amber-100 text-amber-700">Pending</span>

Exceptions

• Email/brand preview components that render non-themed UI may use hardcoded colors
• Charts may use --chart-1 through --chart-5 tokens or raw colors for data series differentiation
• Dynamic brand colors from database/API (e.g., customer portal branding) use inline style: bindings

Layout Conventions

Dashboard Content Wrapper

The dashboard layout provides p-4 padding. Pages within it follow this structure:

<div class="flex flex-1 flex-col overflow-auto">
  <div class="w-full px-6 lg:px-8 py-6 space-y-6">
    <!-- Page content -->
  </div>
</div>

Max-Width by Page Type

Section Spacing

• Between major page sections: space-y-6
• Grid gaps between cards/items: gap-6
• Tight item groups (form fields, button groups, related items): gap-4 or space-y-4
• Within a component (label to input, icon to text): gap-2 or space-y-2

Responsive Breakpoints

• md: (768px) — two-column layouts
• lg: (1024px) — three-column layouts, sidebar shows
• Use @container queries when component responsiveness is independent of viewport

Component Patterns

Button Variants

Button Sizes

Icons

• In menus/dropdowns: h-4 w-4 with mr-2 spacing
• Standalone/page-level: h-5 w-5
• Feature/empty-state illustrations: h-6 w-6 or larger
• Source: @tabler/icons-svelte (project standard)

Feedback Patterns

Data Display

Dropdown Menus

<DropdownMenu.Root bind:open={dropdownOpen}>
  <DropdownMenu.Trigger>
    {#snippet child({ props })}
      <Button variant="ghost" size="icon" {...props}>
        <DotsVerticalIcon />
        <span class="sr-only">Open menu</span>
      </Button>
    {/snippet}
  </DropdownMenu.Trigger>
  <DropdownMenu.Content align="end" class="w-48">
    <DropdownMenu.Group>
      <!-- Standard actions first -->
      <DropdownMenu.Item>
        <EyeIcon class="mr-2 h-4 w-4" />View Details
      </DropdownMenu.Item>
      <DropdownMenu.Separator />
      <!-- Destructive actions last -->
      <DropdownMenu.Item variant="destructive">
        <TrashIcon class="mr-2 h-4 w-4" />Delete
      </DropdownMenu.Item>
    </DropdownMenu.Group>
  </DropdownMenu.Content>
</DropdownMenu.Root>

Form Patterns

When to Use Which

Form Field Spacing

<!-- Standard form layout -->
<div class="grid gap-6 md:grid-cols-2">
  <div class="space-y-2">
    <Form.Field>
      <Form.Control>
        {#snippet children({ props })}
          <Form.Label>Field Name</Form.Label>
          <Input {...props} />
        {/snippet}
      </Form.Control>
      <Form.Description>Helper text</Form.Description>
      <Form.FieldErrors />
    </Form.Field>
  </div>
</div>

• Label to input: space-y-2 (via Form.Field)
• Between form fields: gap-6 (in grid) or space-y-4 (in stack)
• Form sections: space-y-6
• Submit buttons: Full-width w-full in modals/sheets, right-aligned in page forms

Page Headers

<!-- Standard page header -->
<div class="flex items-center justify-between">
  <div>
    <h1 class="text-2xl font-semibold tracking-tight">{title}</h1>
    <p class="text-muted-foreground">{description}</p>
  </div>
  <div class="flex items-center gap-2">
    <!-- Action buttons -->
  </div>
</div>

What This Skill Does NOT Cover

• Creative/marketing UI — use ultra-frontend instead
• Architectural decisions (folder structure, service patterns, data layer)
• Business logic in components
• Accessibility beyond what shadcn provides (shadcn handles ARIA by default)