Conduct a structured code review covering correctness, security, and maintainability. Use when the user asks to review a diff, audit a file, or check for bugs.
Systematically diagnose bugs, test failures, and unexpected behavior before proposing a fix. Use when facing any failure whose root cause is not obvious.
Drive feature work and bug fixes via failing tests first. Use when implementing any feature or fixing a bug, before writing implementation code.
Turn a vague request into a step-by-step plan with verifiable checkpoints. Use before any multi-step implementation, not after.