Arduino CLI is a command-line tool and gRPC daemon for Arduino embedded development. It manages board platforms (cores), libraries, sketches, compilation, upload, monitoring, and debugging. The architecture is dual: a CLI frontend using the Cobra framework and a gRPC server (daemon mode) that exposes the same operations via protobuf-defined services. The core domain logic is organized under `internal/arduino/` with subsystems for building (preprocessor, compiler, linker, diagnostics), package management (index loading, install/uninstall, dependency resolution), sketch handling (profiles, YAML config), and hardware discovery/monitoring. External dependencies include gRPC, protobuf, Cobra/Viper for CLI, and Arduino-specific libraries for path handling, properties, serial communication, and pluggable discovery protocols. The system supports cross-platform operation (Linux, macOS, Windows) and includes extensive integration tests that exercise real CLI commands against isolated environments.