{
  "id": "inference/exists-channel",
  "regime": "resistance",
  "profile": "GACS-I1",
  "claim": "inference-control",
  "harness": "query",
  "policy": "policies/mask-email.json",
  "query": "SELECT id FROM public.customers WHERE id IN (SELECT id FROM public.customers WHERE email LIKE 'a%')",
  "expectedStatus": "NOT_COVERED",
  "expectedFail": true,
  "rationale": "A filtered subquery on a masked column still answers whether any row matches. SQL EXISTS is already refused as an unknown function; this IN form is the remaining 1/0 path.",
  "doesNotTest": "The EXISTS keyword itself; timing; a session-wide probe budget."
}