Expert-level guidance for developing secure, clean, and refactored code across web (React/Next.js/Node.js), iOS (Swift/SwiftUI), and Android (Kotlin/Jetpack Compose) platforms. Use when working on complex multi-platform projects requiring exceptional code quality, security best practices, architecture patterns, and maintainable codebases. Includes advanced patterns for state management, API design, authentication, testing, and cross-platform consistency.