Use when implementing features or fixing bugs test-first, when user mentions "red-green-refactor", when test discipline is required for a specific task, when incremental-implementation needs TDD enforcement, or when a behavior change needs a failing test before any code is written.
Use when .forge/prd.md exists and the system needs a structural design before task breakdown, when modules will be implemented in parallel and need interface contracts to prevent integration failures, or when non-obvious technical decisions need to be recorded for future reference.
Use when .forge/prd.md and .forge/architecture.md exist and the work needs to be decomposed before implementation, when sizing tasks for a sprint, when mapping dependencies between modules, or when a critical path needs to be identified before parallel work begins.
Use when user wants to write a spec, create a PRD, or plan a new feature before implementation begins, when .forge/idea-brief.md exists and is ready to formalize, when requirements need to be captured before architecture or planning, or when a feature's scope and acceptance criteria need to be documented.
Use when creating a new forge-skill, editing an existing skill, when planning to contribute to forge-skills, when a session has produced a one-off prompt that should be promoted to a skill, or when verifying a skill works before deployment.
Use when checking if .forge/ artifacts are stale after a change to requirements, architecture, or any upstream artifact. Use before running /build, /review, or /ship to confirm the artifact chain is consistent. Use when the user says "is anything out of date" or "what needs to be regenerated".
Use when designing REST endpoints, defining error envelopes, setting a versioning or deprecation policy, choosing pagination shape, adding idempotency to mutations, reviewing API contracts, or when two services need a stable interface between them.
Use when establishing brand foundations before any design work, when two products need to feel related, when defining voice and tone for microcopy, or when logo usage and visual identity rules need documenting.