principle-boundary-discipline

Boundary Discipline Place validation, type narrowing, and error handling at system boundaries. Trust internal code unconditionally. Business logic lives in pure functions; the shell is thin and mechanical. Why: Scattered validation is noisy, redundant, and gives a false sense of safety. Validate data once at the boundary. Keep logic out of framework wiring so it can be tested without the framework. The pattern: At boundaries (CLI args, config files, external APIs, network protocols): validate, return errors, handle defensively. Inside the system: typed data, error propagation, no re-validation. Trust the types. Across the boundary. Expose domain concepts, not the boundary's private representation. Keep general-purpose mechanism inside and special-purpose policy at the edge. Applications: Validation and error handling: Validate config at parse time (the boundary), not inside business logic Parse raw data into domain types at the boundary Do not re-export transport, storage, framework, or wire types through the public surface No redundant nil checks deep in call chains if the boundary already validated Show more Installs 889 Repository cursor/plugins GitHub Stars 3.1K First Seen May 24, 2026 Security Audits Gen Agent Trust Hub Pass Socket Pass Snyk Pass