Technical Summary: WebSpark.Bootswatch WebSpark.Bootswatch is a .NET 10-exclusive Razor Class Library that provides seamless integration of Bootswatch themes into ASP.NET Core applications, enabling developers to quickly implement modern, responsive UI theming with Bootstrap 5 as the foundation. The library offers comprehensive theming capabilities including dynamic theme switching, light/dark mode support, and built-in caching mechanisms through the StyleCache service, while providing convenient abstractions via extension methods and custom tag helpers like <bootswatch-theme-switcher /> for straightforward UI implementation. Built primarily with HTML (63.8%), C# (28.6%), and JavaScript (2.6%), the project leverages the Microsoft.Extensions ecosystem and the external WebSpark.HttpClientUtility package to handle HTTP operations and dependency injection patterns within the ASP.NET Core middleware pipeline. The architecture emphasizes production-readiness with comprehensive error handling, fallback mechanisms, and full XML documentation support for IntelliSense integration, while the recent major version 2.0 release represents a strategic decision to prioritize latest package versions and .NET 10 performance improvements over broad framework compatibility—a trade-off that simplifies maintenance and reduces testing complexity. The library targets ASP.NET Core developers seeking an opinionated, batteries-included solution for theme management rather than implementing theming from scratch, with particular utility for multi-tenant applications or projects requiring flexible visual branding and accessibility support through light/dark mode variants. While currently showing declining activity (5 commits in 90 days), the project maintains active curation with clear versioning strategy and documented migration paths, making it suitable for enterprise applications that prioritize modern .NET versions and staying current with framework releases.