Use when mapping repository architecture, dependency graphs, and module boundaries before planning. Triggers on brownfield discovery or whenever durable structural context is missing.

Use when planning, implementing, reviewing, or refactoring code and you need a compact four-principle discipline that keeps changes scoped, simple, and goal-driven. Triggers on code-writing or code-review work.

Use when clarifying user intent, scope boundaries, and acceptance signals before planning. Triggers on governed intake or any change that cannot be planned from the initial request alone.

Use when reviewing the governed plan bundle before S2 implementation may start. Triggers on post-authoring audit or whenever plan artifacts change materially.

Use when executing RED/GREEN/REFACTOR with strict test-first discipline. Triggers on code changes or whenever implementation would otherwise run ahead of proof.