API: POST https://attest.gammaqc.com/verify with {"receipt": <json>, "signature": "<hex>"} → {verified, key_id, reason?}
Discovery: /api · /healthz · /.well-known/attestor.json (JWKS)
Spec: RFC8785-style canonical JSON (sorted keys, no whitespace) signed with Ed25519, hex-encoded. JWKS rotation: 180-day period, 60-day overlap. PQC roadmap: ML-DSA-65 (NIST FIPS-204) drop-in primitive swap — receipt envelope alg field flips on cutover, no client breaking changes.