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This page records what has actually been exercised. It does not turn a private implementation into an upstream standard.

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Testnet evidence

The live flow creates the payload through an otherwise unmodified canonical x402Client, sends it through HTTPFacilitatorClient, and settles through the facilitator. The client package is currently @openx402/stellar-upto; it is shaped for contribution to @x402/stellar and is not yet an upstream release.

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Contract guarantees tested

  • payer, recipient, token, maximum, network, contract, facilitator, settlement identifier, and hook binding;
  • zero, partial, maximum, above-maximum, negative, and i128::MAX amounts;
  • approval, pull, pay, refund, and token-call rollback;
  • replay with the same and changed actual amount;
  • concurrent facilitators and channel-account sequence contention;
  • classic accounts and custom __check_auth accounts;
  • two OpenZeppelin context rules for outer settlement and nested approval;
  • optional settlement hook failure, reentry, balance mutation, and CPU cost;
  • reconciling spending-policy reserve and release behavior.

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Not yet conformance evidence

  • merged upstream scheme_upto_stellar.md and reusable client;
  • official x402 E2E on both networks;
  • pubnet exact or upto transaction hashes;
  • external audit and audited pubnet contract deployment;
  • full issued-USDC and unusual SEP-41 compatibility matrix.
Treat the upto specification source as the normative design draft and the repository evidence as the measured boundary.
Last modified on August 10, 2026