Protocols
payment scheme
In x402, a payment scheme is the rule for how a payment payload is built, verified, and settled. Version 2 names exact, upto, and batch-settlement. A scheme on a network also declares an asset transfer method, such as EIP-3009 or Permit2 on EVM, and a flow: authorization, upfront, or escrow.
Explanation
The exact scheme pays a stated amount. Upto authorizes a ceiling and settles the amount used. Batch settlement gathers many authorizations into a later onchain transaction, which is the pattern Circle's Gateway nanopayments use. The specification says at least one check, a verify or a settle, must happen before the resource runs. Clients should prefer the authorization flow when a server offers both a pay-later and a pay-first option for the same request.
None of those names are visible on a standard ERC-20 Transfer log. This index therefore stores x402 rows as scheme transfer. Reporting them all as exact would invent a distinction the chain does not have. MPP sessions are a different protocol and are stored as scheme session because the Tempo Settled log is specifically a channel settlement.
Live data
Related terms
Sources
- x402 Protocol Specification, version 2 — Coinbase x402
- Nanopayments — Circle
- Agent GDP methodology — Agent GDP