Vauban Research The x402 V2 protocol defines HTTP-native payment flows but leaves three gaps that block compliance use cases. First, the PAYMENT- RESPONSE carries a facilitator-issued reference rather than a self- contained, offline-verifiable cryptographic receipt; an auditor cannot validate a retained receipt without contacting the facilitator. Second, classical signatures alone (ES256K) do not satisfy the post-quantum migration horizon set by NIST SP 800-208, ANSSI, BSI, and EU eIDAS 2.0 for high-value or long-retention material. Third, off-chain receipts alone do not provide ledger- anchored finality required by frameworks such as MiCA Art. 76 (settlement record-keeping) and EU AI Act Art. 12 (transparency-and- documentation). This document consolidates three previously separate extensions into a single specification. It defines (a) a negotiable receipt-format extension with three variants (Stwo Circle STARK proof, hybrid ES256K + ML-DSA-65 dual-signature, classical ES256K fallback) over a JCS canonical preimage discipline grounded in RFC 8785; (b) a two-axis post-quantum discipline mapping hash-based proving and hybrid signatures to the NIST PQC migration roadmap; and (c) a Starknet on- chain anchor format with a canonical anchor tuple, Cairo event layout, RPC endpoint convention, and block explorer reference for human-readable audit. Topics under active coalition discussion are explicitly out of scope: the VPSF composability claim algebra, the payment lifecycle finite state machine, and the delegation binding extension are deferred to companion documents not included in this consolidated submission.