Semi.Avalonia is a comprehensive UI theme library for the Avalonia cross-platform framework, inspired by Semi Design. It provides a complete set of themed controls (buttons, text boxes, data grids, calendars, etc.) with light, dark, and high-contrast variants. The library is distributed as multiple NuGet packages and includes extensive demo applications for desktop, web, Android, and DRM platforms. The architecture is centered around a design token system defined in XAML resource dictionaries, which are consumed by control themes via dynamic resource binding. This allows for runtime theme switching and easy customization. The codebase demonstrates strong use of the MVVM pattern, custom value converters, and internationalization. While actively maintained with nightly CI/CD pipelines, the project carries significant technical debt in the form of large duplicated theme files, a monolithic icon resource, and tight coupling to Avalonia nightly builds. The core theming engine and utility converters are well-crafted and reusable, but the demo applications are tightly coupled to the library's specific branding and structure. No automated tests are present in the repository, which is a notable quality risk for a library of this scope.