Use when implementing any feature or fix using TDD, before writing any implementation code
Use when domain logic leaks into API/Infrastructure, project references violate layer boundaries, or you need to decide between CQS (always), CQRS bus (complex domains), and DDD patterns (invariants and events).
Use when configuring Git hooks in .NET projects before team commits occur, to enforce commit message standards and code formatting automatically
Use before writing any test or implementation task, when observable behavior needs to be captured in business language scenarios and approved by the user before code begins
Use when running mutation testing, killing mutants, verifying test quality, checking mutation score, or analyzing survivors after the test baseline is green
Use when writing tests from the outside-in, defining behavior before code, or any feature where tests should start from observable business behavior and let internal design emerge
Use when understanding project composition by language, measuring code change impact, or generating code statistics for CI/CD metrics
Use when editing code structure with text matching ambiguity, handling "old_string not unique" problems, or performing formatting-independent pattern matching across function signatures, method calls, and class structures