The checklist is a reusable, task-specific procedure that should load only when a pull-request review is being performed. A /review command provides an explicit invocation mechanism, prevents repeated copy-and-paste, and keeps the checklist out of unrelated coding, debugging, and documentation sessions.

In current Claude Code terminology, custom commands have been consolidated into skills. A .claude/skills/review/SKILL.md file creates a /review command, while the legacy .claude/commands/review.md format remains supported. Anthropic recommends skills when users repeatedly supply the same checklist or multi-step procedure; unlike CLAUDE.md content, the skill body is loaded only when invoked or determined relevant. ( https://code.claude.com/docs/en/skills )

Option B introduces an isolated agent context when the requirement is primarily to inject a repeatable review procedure. A subagent could be useful for independent verification, but it is not necessary merely to avoid repasting the checklist. Option C bloats every session with instructions that apply only to code review. Option D controls editing permissions and planning behavior; it does not encode review criteria.

The review skill can also pre-authorize read-only tools and accept a pull-request identifier or branch as an argument.

Official references/topics: Claude Code Skills; Custom Slash Commands; On-Demand Instructions; Reusable Review Workflows.