Building CLI apps with TypeScript in 2026

Building TypeScript command-line interfaces often involves moving beyond fragile manual argument parsing toward robust, type-safe solutions that align with the language's powerful type system. While traditional libraries provide basic structure, they often fall short when handling complex constraints like mutually exclusive options or nested subcommands, leading to runtime checks that the compiler cannot verify. Optique addresses these challenges by using functional parser composition to build CLI structures where types are inferred automatically. This approach allows for the creation of discriminated unions, ensuring that variables like server ports or client URLs are only accessible in their respective modes. Beyond basic parsing, the library handles validation for integers and specific string choices, generates context-aware shell completions for multiple environments, and integrates seamlessly with validation ecosystems like Zod and Valibot. This runtime-agnostic tool works across Node.js, Deno, and Bun, providing a consistent way to manage help text and error handling without the boilerplate of manual logic. By adopting a composable approach to parser construction, developers can ensure their command-line interfaces are not only user-friendly but also structurally sound and type-safe from the start.