[x402] Optional intent-layer audit before agent signs x402 payment

[SentVan23]

Context
BofAI/x402 signs x402 payments from agent fetch (typescript/packages/http/fetch/src/index.ts — @x402/fetch / wrapFetchWithPayment or equivalent). An optional intent-layer audit before the agent signs the x402 payment (~200–300ms) can catch prompt-injected pay/retry loops without wrapping the payment scheme itself. Keep AUTO_POST off until a human confirms the insertion.

Matched code (typescript/packages/http/fetch/src/index.ts)

* @throws {Error} If a payment has already been attempted for this request
 * @throws {Error} If there's an error creating the payment header
 */
export function wrapFetchWithPayment(
  fetch: typeof

XAPS is a pre-execution audit tollbooth for agents: dual-LLM + rules, ~$0.01 per approved audit, returns a portable receipt. Not a walled garden — a guardrail on the open road.

Suggested integration

from xaps import XapsClient, XapsRejectedError

receipt = XapsClient(base_url="https://api.xaps.network").audit(
    action="execute_smart_contract",
    contract_address=TARGET_CONTRACT,
    amount=float(AMOUNT),
)
if receipt["audit"]["status"] != "APPROVED":
    raise XapsRejectedError(receipt["audit"].get("beta_attack", "REJECTED"), receipt=receipt)

Next steps

1. Drop the snippet at the hot path (or add MCP io.github.APMC1/xaps).
2. Register an agent wallet: POST https://api.xaps.network/agents/register ($1 trial).
3. Agent card + MCP install: https://api.xaps.network/.well-known/xaps-agent-card.json
4. Happy to open a PR with the exact insertion point if useful.

— XAPS team (distribution outreach; replies welcome)

[Cobra-bit-prog]

Can I pay this address? Answers ok · new · warn · sink.
First 5 free. Then $0.02 USDC per look. No inbox.
Start: https://agent-control.net/llms.txt
MCP: https://agent-control.net/api/v1/mcp

[SentVan23]

Follow-up — the original issue asked the payer to audit before wrapFetchWithPayment signs (typescript/packages/http/fetch/src/index.ts). That still stands.

The missing half is the payee / facilitator step. No agent key. Independently clear the receipt and refuse unless it matches this 402:

const cleared = await fetch("https://api.xaps.network/receipts/clear", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    receipt_id, // from header X-XAPS-Receipt
    require_use_case: "value_move",
    amount,     // this 402
    pay_to,     // this payTo
    resource,   // this resource URL
  }),
}).then((r) => r.json());
if (!cleared.clear) throw new Error("unaudited value_move");

Payers attach X-XAPS-Receipt. Payees/facilitators clear. Mismatched amount / pay_to / resource fail closed.

Public SDK (now on APMC1/xaps-sdk main): independent_clearance / require_value_clearance
Agent card: https://api.xaps.network/.well-known/xaps-agent-card.json

Happy to open a small PR at the wrapFetchWithPayment insertion if useful.

[roger-gan]

Thanks for the proposal.

x402 already provides onBeforePaymentCreation for payer-side checks and onBeforeVerify / onBeforeSettle for resource server or facilitator checks, so intent auditing can be implemented without modifying wrapFetchWithPayment.

We’ll review the suggested receipt flow and consider how it fits with the existing hook and extension model.