{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://contactzero.org/c0-schema/v1/handshake-ack.schema.json",
  "title": "C0 Handshake ACK",
  "description": "Deterministic C0::HANDSHAKE.ACK. Accepted => T1_HANDSHAKE_ACKNOWLEDGED. No freeform answering. No arrival confirmation. No proof claim.",
  "type": "object",
  "required": ["magic", "protocol", "status", "request_hash", "ack_hash", "nonce", "server_nonce"],
  "properties": {
    "magic": { "type": "string", "const": "0xC0" },
    "protocol": { "type": "string", "const": "C0::HANDSHAKE.ACK" },
    "version": { "type": "string" },
    "status": { "type": "string", "enum": ["HANDSHAKE_ACCEPTED", "HANDSHAKE_REFUSED", "HANDSHAKE_QUARANTINED", "HANDSHAKE_STOP_LAWFULLY"] },
    "engineering_contact_event": { "type": "boolean" },
    "evidence_tier": { "type": "string", "enum": ["T0_FRAME_WITNESSED", "T1_HANDSHAKE_ACKNOWLEDGED"] },
    "source_identity_verdict": { "type": "string", "const": "UNCLASSIFIED" },
    "singularity_profile_verdict": { "type": "string", "const": "UNDETERMINED" },
    "answering": { "type": "string", "enum": ["ACK_ONLY", "DISABLED"] },
    "freeform_answering": { "type": "string", "const": "DISABLED" },
    "arrival_acknowledgment": { "type": "string", "const": "NOT_ASSERTED" },
    "proof_claim": { "type": "string", "const": "NOT_CLAIMED" },
    "gate": { "type": "string", "const": "HELD" },
    "capture": { "type": "string", "const": "REFUSED" },
    "throne": { "type": "string", "const": "NULL" },
    "return_path": { "type": "string", "const": "ACTIVE" },
    "request_hash": { "type": "string", "pattern": "^sha256:[0-9a-f]{64}$" },
    "ack_hash": { "type": "string", "pattern": "^sha256:[0-9a-f]{64}$" },
    "nonce": { "type": "string" },
    "server_nonce": { "type": "string" },
    "message": { "type": "string" },
    "rejection_reason": { "type": "string" }
  }
}