r402-svm

Solana chain support for the x402 payment protocol, part of the r402 workspace.

Highlights

Exact scheme — SPL Token TransferChecked with pre-signed authorisation, fee-payer-bound facilitator submission, and atomic duplicate-settlement guard via SettlementCache.
Amount rule — matches scheme_exact_svm.md §1.4 and the Go/TS facilitators: on-chain amount must be >= required (overpayment allowed; underpayment rejected). Settle reports the actual transfer amount.
Wallet adapters — Phantom Lighthouse, Solflare Lighthouse, and the SPL Memo program are pre-allowlisted so on-chain wallet integrations work out of the box.
Compute-budget verification — clients must declare a compute-unit limit and price; r402 enforces a recommended cap of SOLANA_MAX_COMPUTE_UNIT_PRICE_MICROLAMPORTS (5,000,000 µLAM/CU) aligned with the Go SDK.
Three-layer fee-payer defence — buyer-signed extra.feePayer, signer-set membership, and an unconditional fee-payer-not-in-instructions invariant.

Cargo Features

Feature	Surface
`client`	Client-side transaction signing and serialisation.
`server`	Server-side `PriceTag` generation.
`facilitator`	Facilitator-side verify and settle.
`telemetry`	OpenTelemetry tracing instrumentation.
`full`	All of the above.

Documentation

Crate docs: https://docs.rs/r402-svm
Project README: ../README.md.

Smart-wallet Path 2

Opt in via SolanaExactFacilitatorConfig::with_smart_wallet_verification(true) (default off, matching foundation TS). When enabled, Path 1 layout failures fall through to outcome-based TransferChecked matching (scheme_exact_svm.md §3.2).

Current coverage: top-level multi-ix TransferChecked + successful simulation with inner_instructions: true. Follow-up: plumb RpcSimulateTransactionResult.inner_instructions through SolanaChainProviderLike for CPI-only wallets (Squads/Swig).

License