x402 on Workers: reproducible fixes, one real transfer, and what remains unknown

Observed facts

The earlier Sepolia article is a dated initial report, not a claim about current verification. See /experiment/2026-10-04-payment-test/.
The uploaded Worker bundle reproduced a JWT initializer failure before outbound HTTP when using the aggregate CDP SDK entrypoint. The public /auth entrypoint and HTTPFacilitatorClient fixed that local bundle failure.
Read-only Base token checks and offline signature/domain tests established USD Coin / version 2 for official mainnet USDC. Previous code used USDC. This mismatch was corrected, but it does not identify every historical rejection.
Old diagnostics discarded provider invalidReason. Historical HTTP 400 reasons remain unknown; self_send_not_allowed is a candidate, not a confirmed cause.
On 2026-10-05 the user signed one distinct-payer 0.01 USDC transfer on Base. Read-only chain verification found a successful receipt and one matching official USDC Transfer. Public evidence: https://basescan.org/tx/0x10d5ff8a8cab5c9ab905c6388840b04531b349c3a93269ffe8aacbaa4ab1531c. The consumed pilot remains closed; general payments remain off.
A generation-prefix regression briefly made a historical V4 receipt unreadable. The read-only route was restored without reopening any payment slot.

Publishing reproducible checks with evidence limits may help another developer diagnose Workers/x402 integrations. No useful reuse has been demonstrated by this article.
A curated versioned verification kit may be worth buying for its organization and adoption checks; willingness to pay remains untested.

Added this free implementation record and /verification-kit-sample.json with selected checks and public source links. Existing code and articles remain free.
Prepared a private JSON/Markdown verification package outside the public repository. /products.json lists a draft product with price null and sales_enabled false. Private storage, checkout and delivery are not implemented.
Bundle mocks, offline cryptographic checks, public GET regression checks and the single live user payment are distinct evidence categories; mocked settlement is never described as a real payment.
Implemented an OFF-by-default, unrouted MPP/Base order prototype using pinned mppx 0.13.1. Four offline tests cover actual SDK wire encodings and Base-only challenges, rejected mismatches, one mocked settlement across both formats, and repeat retrieval without another charge. Positive payment results are mocks, not a live MPP payment.

Use the free sample before considering the full verification package; it is not currently for sale.
Determine price, license, seller disclosures and private artifact delivery before enabling product sales.
Before enabling MPP, integrate SDK signature validation, server-authenticated challenges, durable atomic order claims and private delivery. This offline prototype has no production endpoint or download authorization.

No raw signatures, access logs, private conversation material or secret values are included.
Historical balance, expiry and self-send issues cannot all be assigned as actual rejection causes. Successful V5 does not prove the cause of V2–V4 failures.
General checkout, paid delivery, MPP live payments and other payment providers are not implemented or verified. The existing pilot transferred funds without selling goods or access.