HarmonyOS application development expert. Use when building HarmonyOS apps with ArkTS, ArkUI, Stage model, and distributed capabilities. Covers HarmonyOS NEXT (API 12+) best practices.

HarmonyOS Application Development Core Principles ArkTS First — Use ArkTS with strict type safety, no any or dynamic types Declarative UI — Build UI with ArkUI's declarative components and state management Stage Model — Use modern Stage model (UIAbility), not legacy FA model Distributed by Design — Leverage cross device capabilities from the start Atomic Services — Consider atomic services and cards for lightweight experiences One time Development — Design for multi device adaptation (phone, tablet, watch, TV) Hard Rules (Must Follow) These rules are mandatory. Violating them means the skill is not working correctly. No Dynamic Types ArkTS prohibits dynamic typing. Never use any , type assertions, or dynamic property access. No Direct State Mutation Never mutate @State/@Prop variables directly in nested objects. Use immutable updates. Stage Model Only Always use Stage model (UIAbility). Never use deprecated FA model (PageAbility). Component Reusability Extract reusable UI into @Component. No inline complex UI in build() methods. Quick Reference When to Use What Scenario Pattern Example Component local state @State Counter, form inputs Parent to child data @Prop Read only child data Two way binding @Link Shared mutable state Cross component state @Provide/@Consume Theme, user context Persistent state PersistentStorage User preferences App wide state AppStorage Global state Complex state logic @Observed/@ObjectLink Nested object updates State Decorator Selection Project Structure Recommended Architecture Layer Separation ArkUI Component Patterns Basic Component Structure List with LazyForEach Custom Dialog Extended Reference Detailed material starting at State Management Patterns has been moved to [ reference/extended.md ](reference/extended.md) to keep this skill concise. Load that reference when the task requires the moved examples, command catalogs, checklists, platform details, or implementation templates.

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