One accountable human owner · AI-assisted, consent-based offline QA

Why does your Base USDC x402 checkout fail?

Request an evidence-first, fixed-scope analysis of an HTTP 402 payment quote, CORS preflight, or post-payment delivery problem. We use public, sanitized or wholly synthetic fixtures. This page does not connect a wallet, charge a fee, or prove a settlement.

SlothProof open-weight free screening demo · Free sample: two real public x402 routes compared without paying · New: open-source 12-test x402 price-contract QA kit

What a reproducible x402 finding needs

  1. Public 402 response: capture HTTP status and a safe decoding of PAYMENT-REQUIRED from the seller's public endpoint. In x402 v2 this advertises the resource and accepts list; it is not a payment receipt.
  2. Network and asset: distinguish Base mainnet eip155:8453 from Base Sepolia eip155:84532; check the actual asset value, not merely the token name. Native Circle Base USDC contract: 0x833589fCD6eDb6E08f4C7C32D4f71b54bdA02913.
  3. Price and payee: compare the precise amount in six-decimal Base USDC units and payTo against the seller's own documented terms. A seller address need not be the customer's address.
  4. Browser compatibility: compare an unpaid OPTIONS preflight and CORS exposure of PAYMENT-REQUIRED against the request origin. Browser success and server-to-server success are different claims.
  5. Delivery and settlement: separate a payment quote, a verified on-chain transfer, and the actual post-payment resource body. Claim a successful sale only when real source-specific settlement and delivery evidence exists.

Official protocol source: x402 Foundation HTTP transport v2. This is a reproducibility checklist, not a wallet audit or a promise that your seller is solvent.

Request a narrow, priced diagnostic

Single 402 / OPTIONS QA pilot

$5 USDC on Base, proposed fixed scope

One authorized public/nonsecret 402 or OPTIONS symptom, one wholly synthetic regression fixture, a one-page fault classification, and a concise CORS/header checklist.

Ask for a $5 written scope

Expanded offline x402 diagnostics

$19 USDC on Base, proposed fixed scope

For one independently owned public API origin: up to two sanitized 402/OPTIONS/OpenAPI fixture sets, a maximum of six offline checks, a Markdown and JSON finding bundle, and one factual correction round.

Open a $19 QA request on GitHub

GitHub sign-in is required for the issue form. Email is an alternative.

Two-origin price-contract QA bundle

$39 USDC on an agreed supported network, proposed fixed scope

Two independently hosted public API origins (for example two brand products operated by the same company): compare their separate first-party OpenAPI fixed USD prices with unpaid x402 v2 Base Circle USDC quotes, up to six synthetic quote/asset/network/resource assertions total, one short actionable report and one post-fix recheck.

Request a $39 written scope

A single-origin $19 request is a different scope. We do not perform paid live calls, wallet signing, customer-data collection or unauthorized testing.

All listed prices are nonbinding until scope, acceptance, refund policy, and supported settlement rail are agreed in writing. Do not transfer USDC in response to this page. No package requires a stake, bond, private key, API token, customer password, or raw confidential HAR. This service does not conduct live unauthorised pentests, execute signed user payments, promise a critical finding, or guarantee a buyer/sponsor reimbursement.

Safe, free example of the kind of discrepancy we report

A fictional quote for eip155:84532 (testnet) is not a $0.01 charge on Base mainnet. The word “USDC” in a listing is not token identity. This example is a local synthetic fixture; no seller, wallet, or payment is involved.

HTTP/1.1 402 Payment Required
PAYMENT-REQUIRED: <base64-encoded JSON from the seller>

Decoded accepts[0]:
  network: eip155:84532   # TESTNET, not Base 8453
  scheme: exact
  amount: 10000            # 0.010000 of a six-decimal test token
  asset: 0x<testnet-token-address>
  payTo: 0x<testnet-payee-address>
Result: NEEDS INDEPENDENT VERIFICATION; 0 mainnet USDC receipts.

For existing public no-payment comparisons, see the TapeOut x402 offline route evidence and free synthetic API sample. The original merchant's separately priced $0.01 live public quote checker is available through its existing merchant directory; this consultation offer is a different, manually scoped service.

How to request work without sharing secrets

  1. Send only the public endpoint path, stated price/network, the minimal redacted 402/OPTIONS symptom, and your desired written deliverable.
  2. We confirm that the requested public tests are authorised, reproducible, and feasible. We disclose substantial AI assistance and identify the responsible human economic owner without pretending to hold a professional audit license.
  3. We agree the exact scope, fee, accepted asset/chain, refunds, delivery and review terms before any charge or client-specific work.
  4. We deliver bounded offline test artifacts and one concise report. You can independently rerun the synthetic checks.

Never send us secret keys, seed phrases, signed payment payloads, bank identity, cookies, bearer headers, raw unredacted HARs, personal data, or private repository access. Use made-up values such as example.invalid for fixtures.

Neither a publicly listed service, a click on a contact link, a 402 response nor a draft quote is an order. No external customer payment is represented or claimed by this page.