Use after neutral discovery and before Scope Ledger drafting when consequential design uncertainty, ownership placement, lifecycle/state responsibility, compatibility, migration, algorithm choice, operability, or reversibility could admit a materially different safe approach. Begin with a lightweight design-space probe when the lead currently sees one obvious design but an alternative may plausibly exist. Run the full comparison when the probe identifies two or more viable approaches or when choosing incorrectly would be materially consequential. Do not trigger when settled constraints clearly force one safe design.
Explain, trace, or deeply review existing code using inspected repository evidence without implementing changes. Use for code-understanding requests unless the user explicitly asks only for a concise, brief, quick, high-level, or initial overview. This skill explicitly owns thorough reviews, comprehensive explanations, audits, diagnosis, correctness analysis, architecture assessment, risk analysis, execution tracing, concurrency analysis, lifecycle analysis, and full subsystem understanding.
Use when actual scientific or model inputs, outputs, semantics, units, boundaries, classifications, calibration, uncertainty, tolerances, or claims change or require authoritative resolution. Independently derive and evaluate the scientifically defensible contract, compare competing interpretations, create independent golden vectors, and make evidence-qualified recommendations while leaving product policy, scope, architecture, and implementation authority with the user and lead. Do not trigger for mechanical work that cannot affect model behavior or claims.
Use before approval when testability or oracle quality could materially affect scope, behavior, architecture, observability, or validation planning, and after approval before implementation when the detailed planned evidence may not falsify a broken design. Apply to unclear parser, protocol, config, lifecycle, retained-state, performance, scientific/model, security, workflow-checker, or other material oracles. Do not trigger when accepted checks directly prove a localized mechanical change.
Use when reviewing or changing Codex workflow authority, approval, validation routing, review rules, templates, repo-managed skills, or enforcing scripts. Select conformance mode when checking implementation against accepted workflow policy. Select effectiveness mode when the user explicitly asks whether the workflow, its rules, or its architecture should be retained, changed, consolidated, replaced, or removed. Do not trigger for ordinary product documentation or runtime work whose workflow contract is unchanged.
Use after current-state discovery when material product, operator, compatibility, failure, classification, default, threshold, ordering, precedence, persistence, or test-oracle semantics still admit more than one plausible interpretation. Compare interpretations and make conditional recommendations, but unresolved material semantics remain user-owned and block concrete design selection and an unconditional Scope Ledger until explicitly resolved by the user, controlling authority, or evidence that eliminates every competing interpretation. Do not trigger merely because requirements are detailed or work is Non-trivial.
Deliver a concise initial orientation to existing code without implementing changes. Use only when the user explicitly asks for a concise, brief, quick, high-level, or initial overview and no more specific repo-managed review, audit, diagnostic, domain, or engineering skill applies. Do not compose this skill with a specialist skill or use its output format to constrain specialist analysis.
Use for read-only review of newly written gocluster Go implementation when the work is High-risk or substantial: shared/exported interfaces, material algorithms or state machines, substantial rewrites, meaningful residual uncertainty, or multiple production packages with shared impact or cross-package uncertainty. Do not trigger for every Non-trivial Go edit.