ios-design-system

Design

Clinic-architecture-aligned iOS design system engineering for SwiftUI (iOS 26 / Swift 6.2) covering token architecture, color/typography/spacing systems, component style libraries, asset governance, and theming. Enforces @Equatable on views and keeps design-system usage compatible with Feature-to-Domain+DesignSystem boundaries. Use when building or refactoring DesignSystem infrastructure for the clinic modular MVVM-C stack.

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Airbnb iOS Design System Best Practices

Opinionated, strict design system engineering for SwiftUI iOS 26 / Swift 6.2 apps. Contains 50 rules across 8 categories, prioritized by impact. Derived from Airbnb's Design Language System (DLS), Airbnb Swift Style Guide, Apple Human Interface Guidelines, and WWDC sessions. Mandates @Equatable on every view, @Observable for state, and style protocols as the primary component API.

Mandated Architecture Alignment

This skill is designed to work alongside swift-ui-architect. All code examples follow the same non-negotiable constraints:

Feature modules depend on Domain + DesignSystem; no direct Data dependency
@Observable for mutable UI state, ObservableObject / @Published never
@Equatable macro on every view
Style protocols as the primary component styling API (Airbnb DLS pattern)
Asset catalog as the source of truth for color values
Local SPM package for design system module boundary

Scope & Relationship to Sibling Skills

This skill is the infrastructure layer — it teaches how to BUILD the design system itself. When loaded alongside sibling skills:

Sibling Skill	Its Focus	This Skill's Focus
`swift-ui-architect`	Architecture (modular MVVM-C, route shells, protocol boundaries)	Design system infrastructure (tokens, styles, governance)
`ios-design`	Using design primitives (semantic colors, typography)	Engineering the token system that provides those primitives
`ios-ui-refactor`	Auditing/fixing visual quality issues	Preventing those issues via governance and automation
`ios-hig`	HIG compliance patterns	Asset and component infrastructure that makes compliance easy

Clinic Architecture Contract (iOS 26 / Swift 6.2)

All guidance in this skill assumes the clinic modular MVVM-C architecture:

Feature modules import Domain + DesignSystem only (never Data, never sibling features)
App target is the convergence point and owns DependencyContainer, concrete coordinators, and Route Shell wiring
Domain stays pure Swift and defines models plus repository, *Coordinating, ErrorRouting, and AppError contracts
Data owns SwiftData/network/sync/retry/background I/O and implements Domain protocols
Read/write flow defaults to stale-while-revalidate reads and optimistic queued writes
ViewModels call repository protocols directly (no default use-case/interactor layer)

When to Apply

Reference these guidelines when:

Setting up a design system for a new iOS app
Building token architecture (colors, typography, spacing, sizing)
Creating reusable component styles (ButtonStyle, LabelStyle, custom DLS protocols)
Organizing asset catalogs (colors, images, icons)
Migrating from ad-hoc styles to a governed token system
Preventing style drift and enforcing consistency via automation
Building theming infrastructure for whitelabel or multi-brand apps
Reviewing PRs for ungoverned colors, hardcoded values, or shadow tokens

Rule Categories by Priority

Priority	Category	Impact	Prefix	Rules
1	Token Architecture	CRITICAL	`token-`	6
2	Color System Engineering	CRITICAL	`color-`	7
3	Component Style Library	CRITICAL	`style-`	10
4	Typography Scale	HIGH	`type-`	5
5	Spacing & Sizing System	HIGH	`space-`	5
6	Consistency & Governance	HIGH	`govern-`	7
7	Asset Management	MEDIUM-HIGH	`asset-`	5
8	Theme & Brand Infrastructure	MEDIUM	`theme-`	5

Quick Reference

1. Token Architecture (CRITICAL)

token-three-layer-hierarchy - Use Raw → Semantic → Component token layers
token-enum-over-struct - Use caseless enums for token namespaces
token-single-file-per-domain - One token file per design domain
token-shapestyle-extensions - Extend ShapeStyle for dot-syntax colors
token-asset-catalog-source - Source color tokens from asset catalog
token-avoid-over-abstraction - Avoid over-abstracting beyond three layers

2. Color System Engineering (CRITICAL)

color-organized-xcassets - Organize color assets with folder groups by role
color-complete-pairs - Define both appearances for every custom color
color-limit-palette - Limit custom colors to under 20 semantic tokens
color-no-hex-in-views - Never use Color literals or hex in view code
color-system-first - Prefer system colors before custom tokens
color-tint-not-brand-everywhere - Set brand color as app tint, don't scatter it
color-audit-script - Audit for ungoverned colors with a build script

3. Component Style Library (CRITICAL)

style-dls-protocol-pattern - Define custom style protocols for complex DLS components
style-equatable-views - Apply @Equatable to every design system view
style-accessibility-first - Build accessibility into style protocols, not individual views
style-protocol-over-wrapper - Use Style protocols instead of wrapper views
style-static-member-syntax - Provide static member syntax for custom styles
style-environment-awareness - Make styles responsive to environment values
style-view-for-containers-modifier-for-styling - Views for containers, modifiers for styling
style-catalog-file - One style catalog file per component type
style-configuration-over-parameters - Prefer configuration structs over many parameters
style-preview-catalog - Create a preview catalog for all styles

4. Typography Scale (HIGH)

type-scale-enum - Define a type scale enum wrapping system styles
type-system-styles-first - Use system text styles before custom ones
type-custom-font-registration - Register custom fonts with a centralized extension
type-max-styles-per-screen - Limit typography variations to 3-4 per screen
type-avoid-font-design-mixing - Use one font design per app

5. Spacing & Sizing System (HIGH)

space-token-enum - Define spacing tokens as a caseless enum
space-radius-tokens - Define corner radius tokens by component type
space-no-magic-numbers - Zero hardcoded numbers in view layout code
space-insets-pattern - Use EdgeInsets constants for composite padding
space-size-tokens - Define size tokens for common dimensions

6. Consistency & Governance (HIGH)

govern-naming-conventions - Enforce consistent naming conventions across all tokens
govern-spm-package-boundary - Isolate the design system as a local SPM package
govern-single-source-of-truth - Every visual value has one definition point
govern-lint-for-tokens - Use SwiftLint rules to enforce token usage
govern-design-system-directory - Isolate tokens in a dedicated directory
govern-migration-incremental - Migrate to tokens incrementally
govern-prevent-local-tokens - Prevent feature modules from defining local tokens

7. Asset Management (MEDIUM-HIGH)

asset-separate-catalogs - Separate asset catalogs for colors, images, icons
asset-sf-symbols-first - Use SF Symbols before custom icons
asset-icon-export-format - Use PDF/SVG vectors, never multiple PNGs
asset-image-optimization - Use compression and on-demand resources
asset-naming-convention - Consistent naming convention for all assets

8. Theme & Brand Infrastructure (MEDIUM)

theme-environment-key - Use EnvironmentKey for theme propagation
theme-dont-over-theme - Avoid building a theme system unless needed
theme-tint-for-brand - Use .tint() as primary brand expression
theme-light-dark-only - Use ColorScheme for light/dark, not custom theming
theme-brand-layer-separation - Separate brand identity from system mechanics

How to Use

Read individual reference files for detailed explanations and code examples:

Section definitions - Category structure and impact levels
Rule template - Template for adding new rules

Reference Files

File	Description
references/_sections.md	Category definitions and ordering
assets/templates/_template.md	Template for new rules
metadata.json	Version and reference information