iOS 27 and macOS 27 betas bring two major changes developers should address now. First, the Liquid Glass compatibility flag (`UIDesignRequiresCompatibility`) is removed in Xcode 27, making the new design system mandatory for all apps — with real geometry implications for safe areas, scroll insets, and navigation bars. Second, the Foundation Models framework now supports pluggable backends, letting developers swap in Apple's Private Cloud Compute model, MLX models from Hugging Face, or bundled SPM models using the same `LanguageModelSession` API. Also covered: a SwiftUI pattern for non-modal inspector-style panels using `presentationDetents` and `presentationBackgroundInteraction`, plus quick hits on Core AI, macOS Application Support Protection, UIBarMinimization, and SwiftUI blend modes.
