Self-hosted alternatives to principle-boundary-discipline

P

principle-boundary-discipline

Apply when wiring validation, error handling, or framework adapters

principle-boundary-discipline is an agent skill from Cursor's plugins collection that applies a design principle for wiring validation, error handling and framework adapters. It says to place validation, type narrowing and error handling at the system's boundaries, meaning the command-line arguments, configuration files, external APIs and network protocols, and to trust internal code unconditionally once data has crossed into the system. Business logic should live in pure functions, with a thin and mechanical shell around them, so the logic can be tested without the framework. The reasoning given is that scattered validation is noisy, redundant and creates a false sense of safety. Inside the system, data should be typed and errors propagated, without re-validating what has already been checked. When data crosses the boundary outward, the code should expose domain concepts rather than the boundary's private representation. The principle guides how to structure a new feature or adapter, and it suits developers who want validation to happen in one place and core logic to stay easy to test. It is listed on skills.sh, where the page shows install counts and GitHub stars for the Cursor plugins repository. Install it with npx skills add https://github.com/cursor/plugins --skill principle-boundary-discipline.