{
  "tool_id": "art-595-ap2-cartmandate-hashchain-builder",
  "kernel_id": "art-595-ap2-cartmandate-hashchain-builder",
  "display_name": "AP2 CartMandate Hash-Chain Builder",
  "tool_version": "1.0.0",
  "mandate_type": "payment_policy",
  "purpose": "Builds an illustrative Google AP2 CartMandate Verifiable Digital Credential (VDC) skeleton whose credentialSubject carries a deterministic hash-chain over an ordered list of cart line items: link_0 = keccak256(canon({index:0,item})), link_i = keccak256(canon({index:i,item,prev:link_(i-1)})), cart_root = the final link. Reuses this repo's existing RFC 8785/JCS canonicalization (cgCanon, from _hash.mjs) and the already-vendored @noble/hashes keccak256 bundle -- no new vendoring, no hand-rolled canonicalization or hashing. Stands beside art-16 (Google AP2 Mandate Builder) as a new node, not an edit to it -- art-16's flat CheckoutMandate/PaymentMandate shape has no line-item array to chain over. An intact chain proves the ordered cart_items list was not altered after the chain was built; it does NOT prove human authorisation, delivery, settlement, or that item prices are correct or current. Given a prior chain's per-item links (claimed_links) and a (possibly tampered) cart_items, the kernel recomputes and reports CART_CHAIN_INTACT plus the earliest divergent index, never a thrown exception. Zero network calls; never a facilitator, proxy, gateway, or settlement relay.",
  "control_description": "Builds an illustrative Google AP2 CartMandate Verifiable Digital Credential (VDC) skeleton whose credentialSubject carries a deterministic hash-chain over an ordered list of cart line items: link_0 = keccak256(canon({index:0,item})), link_i = keccak256(canon({index:i,item,prev:link_(i-1)})), cart_root = the final link. Reuses this repo's existing RFC 8785/JCS canonicalization (cgCanon, from _hash.mjs) and the already-vendored @noble/hashes keccak256 bundle -- no new vendoring, no hand-rolled canonicalization or hashing. Stands beside art-16 (Google AP2 Mandate Builder) as a new node, not an edit to it -- art-16's flat CheckoutMandate/PaymentMandate shape has no line-item array to chain over. An intact chain proves the ordered cart_items list was not altered after the chain was built; it does NOT prove human authorisation, delivery, settlement, or that item prices are correct or current. Given a prior chain's per-item links (claimed_links) and a (possibly tampered) cart_items, the kernel recomputes and reports CART_CHAIN_INTACT plus the earliest divergent index, never a thrown exception. Zero network calls; never a facilitator, proxy, gateway, or settlement relay.",
  "declared_inputs": [],
  "declared_outputs": [
    "art-596-ap2-x402-cart-correlation"
  ],
  "kernel_digest": "sha256:b0b1ed06bbeb16d1227f7073af8e46c323bff835b503b0d2f3a7231baa44803e",
  "trust_label": "independently verified: zkVM execution proof (risc0/groth16-bn254)",
  "data_vintage": "2026-08-20",
  "last_validated": "2026-08-20",
  "conformance_fixtures_vendored": true,
  "compute_proof_ready": "ready",
  "wave": 99,
  "source_url": "https://ainumbers.co/chaingraph/art-595-ap2-cartmandate-hashchain-builder.html",
  "generated_at": "2026-08-22T17:52:19.663Z"
}