Whitepaper
The protocol's normative specification. Wire format, validation rules, security model.
The full normative specification for the aa-native scheme is published as a whitepaper (PDF). It is the authoritative source for any conformance question.
Download the whitepaper (PDF, ~280 KB, 16 pages)
What's inside
- Background. The x402 V2 protocol; why ERC-4337 accounts cannot satisfy
exact; the two motivations foraa-native. - The aa-native scheme. Payload format, wire-format integration,
requestHashderivation, verification rules, settlement procedure, and the complete error code list. - Comparison to
exact. Side-by-side table plus prose on operational simplicity and trust assumptions. - Reference implementation.
SettlementContract.sol, the facilitator service, and the four-package SDK suite. - Security considerations. Replay protection (on-chain and off-chain), cross-merchant replay, paymaster abuse, settlement finality, refund posture.
- Future work and standardization. Multi-chain deployment, per-merchant settlement contracts, session keys, and the path to upstream standardization through
coinbase/x402#639.
The two appendices are a glossary of the AA and x402 terms used throughout, and a reference list of every external standard and document the spec relies on (RFC 2119, ERC-4337, EIP-3009, x402 V2 transport, NERO AA platform docs).
Citing
The whitepaper version printed on the title page is the canonical reference. When citing the spec in upstream conversations, link directly to the PDF; when referring to a specific clause, cite the section number (e.g., "see whitepaper §2.4 for the full validation rules").
Source
The whitepaper source is in the project repo at docs/whitepaper/whitepaper.md. It builds to PDF via Pandoc + Typst (make pdf in that directory). The protocol-flow figure is generated from a D2 diagram source at docs/whitepaper/figures/protocol-flow.d2.