Porcupine is a cross-platform wake word (keyword spotting) engine by Picovoice. The repository is a comprehensive SDK that provides native bindings for 10+ platforms including Android, iOS, Web (WASM), Python, Node.js, Java, .NET, Flutter, React Native, and embedded microcontrollers (STM32). The core engine is a proprietary binary (libpv_porcupine), but the repository contains all wrapper code, demos, and test infrastructure. The API is consistent across all bindings: a Porcupine class with init/process/release, a high-level PorcupineManager that handles microphone capture, and a set of built-in keywords for immediate use. The codebase demonstrates strong engineering practices: uniform error hierarchies, platform abstraction for library loading, and extensive CI/CD pipelines. The demos are production-quality and serve as integration templates. The repository is actively maintained with frequent commits and a large community (4.9k stars). The primary limitation is that the core engine is proprietary and requires a Picovoice access key, making the SDK itself not fully open-source. However, the binding code, patterns, and test infrastructure are reusable for other voice AI engines.