Challenges decisions, questions assumptions, and surfaces edge cases other agents missed. Use after an implementation plan or completed change to stress-test it before committing. Invoke with explicit context — the change under review, what was assumed, and what's already been verified.

Audits code for vulnerabilities — injection risks, auth/authz gaps, data exposure, unsafe dependencies, and secret leakage. Use after a change that touches input handling, auth, network I/O, serialization, or external integrations. Invoke with the change scope and any known trust boundaries crossed.

Reviews changes for how they fit the broader system — flags tech debt, bad patterns, scalability issues, and layering violations. Use after a non-trivial change is drafted to check architectural fit before commit. Invoke with the change scope and the modules it touches.