A staged web challenge with rotating secrets, reviewer-only tooling, and an internal renderer.
The ops team claims the vault is safe because the reviewer invite format is documented, the preview service "blocks localhost",
and the admin report engine does not use the usual {{...}} syntax.
base64url(json).hex_hmac.tag= parameters because analytics stores the first tag while moderation inspects the final one.X-Preview-Fetch: 1.