int(os.environ.get("PORT", "8080")) fails constantly in ways that waste your time: ValueError: invalid literal for int() with base 10: 'abc' . No variable name. No hint about what a valid value looks like. You grep the codebase for PORT to even find where the read happened. specenv is a zero-runtime-dependency Python library for typed environment variable loading — casting, validation, schema grouping, prefix namespacing. All of that is useful, but none of it is the actual design decisi...