Design Systems Slds Apply

Applying SLDS

The Salesforce Lightning Design System (SLDS) is a CSS framework with thousands of artifacts. This skill teaches agents how to find and correctly use them.

Version: This skill targets SLDS v2. Legacy --lwc-* tokens and slds-*--modifier syntax are deprecated.

Audit scope: The companion design-systems-slds-validate skill analyzer only scans .css, .html, and .js files. Use it directly for LWC and similar HTML/CSS/JS components; treat it as a partial signal for JSX/TSX or other framework-specific template formats and supplement with manual review.

What is SLDS?

Scope

This skill covers:

• Which blueprint to use for a given UI pattern
• How to style with hooks (color, spacing, typography, shadows, borders)
• Which utility classes to use for layout, spacing, visibility
• Which icon to use and from which category
• SLDS naming conventions, class structure, hook syntax

This skill includes basic accessibility reminders (icon alt text, focus outlines, color-not-sole-indicator) in the validation checklists. Full WCAG compliance requires a dedicated accessibility review.

This skill does NOT cover (use companion skills):

• Design decisions -- visual hierarchy, composition, interaction patterns
• LWC mechanics -- component structure, @wire, @api, lifecycle, events (not yet available)
• Full accessibility -- WCAG conformance, ARIA patterns, keyboard navigation, focus management, contrast ratios (not yet available)

Component Selection Hierarchy

Always follow this order:

1. Lightning Base Components (LWC only)    ← Check first
2. SLDS Blueprints (any framework)         ← Use exact SLDS classes
3. Custom with Styling Hooks               ← Use var(--slds-g-*)
4. Custom CSS (last resort)                ← Still use hooks for values

If building in LWC, check for an LBC first: Lightning Component Library

If no LBC exists (or not using LWC), select an SLDS Blueprint. See references/component-selection.md.

Core Rules

Do

• Follow the selection hierarchy: LBC > Blueprint > Hooks > Custom CSS
• Use var(--slds-g-*, fallback) for all themeable values
• Create custom classes (my-*, c-*) instead of overriding .slds-*
• Verify every hook, class, and utility exists before using it — run the search scripts; never assume an artifact exists based on naming patterns (see Verify Before You Use)
• Pair surface colors with on-surface colors for text
• Provide alternative-text on every <lightning-icon>

Don't

• Hard-code colors, spacing, or typography values
• Override .slds-* classes directly
• Use deprecated --lwc-* tokens as primary values
• Use --slds-s-* (shared) hooks -- they are private/internal
• Reassign hook values -- only reference them with var()
• Use color alone to convey meaning
• Invent hook names by interpolating patterns from other families (see Naming Traps below)

Hook Naming Traps

SLDS hook families do NOT all follow the same naming pattern. Agents frequently invent hooks that don't exist by assuming {prefix}-{number} works universally. Always verify a hook exists via the bundled search-hooks.cjs script or assets/hooks-index.json before using it.

Trap 1: Font size hooks are NOT numbered

Rule: For font sizes, use --slds-g-font-size-base (the one base size) or --slds-g-font-scale-* (the numbered scale). Never --slds-g-font-size-N.

Trap 2: Color hooks always require a number

Rule: Every --slds-g-color-* hook ends in a number. Pick by emphasis: -1 (low), -2 (medium), -3 (high).

Trap 3: Not all values have hook equivalents

Some CSS values (e.g., min-width: 7rem for label alignment) have no SLDS hook. This is acceptable:

.c-field-label {
  /* No SLDS hook exists for this width; intentional custom value */
  min-width: 7rem;
}

Rule: When no hook exists, use the value directly with a comment explaining it's intentional. Prefer SLDS grid utilities (slds-size_*) as alternatives to hardcoded widths where possible.

Verify Before You Use

Rule: Never include an SLDS hook, utility class, blueprint class, or icon in generated code without first confirming it exists in the metadata. Guessing based on naming patterns is the primary source of invented artifacts.

Run the appropriate search command before emitting any SLDS artifact:

If the search returns no match: do not use the artifact. Find an alternative from the search results or build custom with verified hooks.

Naming Conventions

Use a consistent prefix for custom classes to avoid collision with SLDS:

Avoid: generic names (container, wrapper), SLDS-like names (custom-slds-button), BEM on SLDS classes (slds-card__custom-header).

Custom hook namespacing:

:root {
  --my-app-primary: var(--slds-g-color-accent-1);
  --my-app-card-padding: var(--slds-g-spacing-4);
}

Knowledge Map

This skill bundles comprehensive SLDS knowledge. Read files as needed -- don't read everything upfront.

Decision Guides (start here for each task)