pkgx is a standalone CLI package runner (~4 MiB) that can run any open-source tool without modifying the host system. It resolves dependencies, downloads pre-built tarballs from a distribution server (dist.pkgx.dev), installs them to ~/.pkgx, and injects the correct environment (PATH, MANPATH, PKG_CONFIG_PATH, etc.) before executing the requested command. The codebase is a Rust workspace split into a CLI crate (crates/cli) handling argument parsing, querying, and execution, and a library crate (crates/lib) providing core logic: local cellar management, pantry YAML parsing with platform-aware deserialization, SQLite-backed pantry indexing, async installation with atomic extraction and file locking, dependency graph hydration with support for multi-version projects (e.g., OpenSSL 1.1 vs 3), and environment variable construction (including moustache template expansion for runtime env vars). The architecture is monolithic but well-modularized, with clear separation of concerns. It demonstrates high craftsmanship in areas like cross-platform environment handling, progress visualization, and robust concurrent installation. The repository is actively maintained with comprehensive CI/CD pipelines, tests, and code quality checks.