Deterministic guard layer: pre/post tool guards, prompt filter, output contracts, secrets, constitution compliance. Thin doc over hooks/scripts. Topics: constitution-compliance, input-tolerance, integrity-chain-validation, management, output-contract-enforcer, permission-fast-path, post-tool-use-validator, pre-tool-use-guard, quality-gatekeeper, secrets-sanitization, stop-validator, user-prompt-filter.