{
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "$id": "https://real-life.org/trust-tasks/delivery-ack/0.1",
 "title": "Payload: delivery-ack/0.1 (rltp-delivery@0.79, target Trust Tasks framework 0.4)",
 "description": "Payload schema per Trust Tasks 6.3 ($id = Type URI, describes only the payload). Arrival acknowledgement per Delivery Contract 4.2: machine-generated at the durable recording of the referenced document's defined effect; the document carrying this payload MUST carry a proof in the form the 4.2/4.4 acknowledgement class rule selects: eddsa-jcs-2022 under the issuer anchor for signature-class payloads, the deniable channel-keyed MAC for designated-verifier payloads; meaning is arrival only, never acceptance or any human act.",
 "type": "object",
 "required": [
  "ref",
  "meaning"
 ],
 "additionalProperties": false,
 "properties": {
  "ref": {
   "type": "string",
   "description": "multibase-encoded multihash (sha2-256: 0x12 0x20 + 32 bytes) over JCS-canonicalized input; emit 'u' (46 chars after header), accept 'u'/'z' per CID 1.0; decoded multihash verified at parse",
   "pattern": "^(u[A-Za-z0-9_-]{45}[AQgw]|z[1-9A-HJ-NP-Za-km-z]{44,48})$"
  },
  "meaning": {
   "const": "received"
  }
 }
}