This repository is a comprehensive .NET SDK for the Alpaca Markets API, providing both REST and WebSocket clients for algorithmic trading, market data retrieval (stocks, crypto, options), and account management. The architecture is a layered client library with core (`Alpaca.Markets`) and extensions (`Alpaca.Markets.Extensions`) NuGet packages, targeting multiple .NET frameworks (netstandard2.0/2.1, net462, net8.0, net10.0). Entry points include configuration classes that instantiate typed clients (e.g., `IAlpacaTradingClient`, `IAlpacaDataClient`, `IAlpacaCryptoDataClient`, `IAlpacaOptionsDataClient`) via environment-specific base URLs (live, paper). The library supports advanced order types (bracket, OCO, trailing stop), real-time streaming with automatic reconnection, and efficient pagination using `IAsyncEnumerable`. The codebase exhibits high craftsmanship with clean separation of interfaces, messages, and parameters; fluent builder patterns for orders; and robust testing infrastructure using mocks. The extensions package adds DI integration (`AddAlpaca*Client`), Polly-based retry, and reusable subscription management. While the SDK is actively maintained and well-tested, it relies on Newtonsoft.Json (rather than System.Text.Json) and maintains compatibility with older frameworks, adding complexity. A minor risk is dependency on internal Alpaca API endpoints that could change, but the library's design isolates these concerns.