Crate r402 

r402

x402 Payment Protocol SDK for Rust — umbrella crate.

This crate re-exports the workspace under feature flags. Prefer depending on individual crates when you need a minimal dependency graph.

Included crates

Feature	Crate	Role
(always)	r402-core	Wire types, Facilitator, schemes, hooks, extensions
evm (default)	r402-evm	EVM exact + upto (ERC-3009 / Permit2)
svm	r402-svm	Solana exact (SPL Token / Token-2022)
tron	r402-tron	Tron exact (TIP-712 / EIP-3009 + Permit2)
casper	r402-casper	Casper exact (CEP-18, remote facilitator)
http (default)	r402-http	Axum middleware + reqwest client
mcp	r402-mcp	MCP transport on official rmcp (V2)

Forwarding features: client, server, facilitator, telemetry, cache, ext-bazaar, ext-payment-id, all-extensions, full.

Quick Start

[dependencies]
# Minimal EVM HTTP server/client
r402 = { version = "0.15", features = ["evm", "http", "client", "server", "facilitator"] }

# Multi-chain
r402 = { version = "0.15", features = [
  "evm", "svm", "tron", "casper",
  "http", "client", "server", "facilitator",
] }

// After enabling the matching features:
use r402::evm;    // r402-evm
use r402::svm;    // r402-svm
use r402::tron;   // r402-tron
use r402::casper; // r402-casper
use r402::http;   // r402-http
use r402::mcp;    // r402-mcp (needs feature "mcp")

Features

Flag	Default	What it enables
evm	yes	Re-export r402-evm as evm
svm		Re-export r402-svm as svm
tron		Re-export r402-tron as tron
casper		Re-export r402-casper as casper
http	yes	Re-export r402-http as http
mcp		Re-export r402-mcp as mcp
client		Forward client to enabled chain + http crates
server		Forward server to enabled chain + http crates
facilitator		Forward facilitator (Casper also enables http-client)
telemetry		Forward telemetry / tracing
cache		r402-core settlement cache
ext-bazaar		Bazaar extension
ext-payment-id		Payment-identifier extension
all-extensions		All built-in extensions
full		Every feature above

License

Licensed under either of MIT or Apache-2.0, at your option.

Re-exports

pub use r402_casper as casper;casper

pub use r402_evm as evm;evm

pub use r402_http as http;http

pub use r402_mcp as mcp;mcp

pub use r402_svm as svm;svm

pub use r402_tron as tron;tron

Modules

amount

Human-readable currency amount parsing.

cachecache

Shared cache primitives used by facilitator implementations.

chain

Blockchain-specific types and providers for x402 payment processing.

error

Layered error types for x402 facilitator operations.

error_reason

Machine-readable error codes used in x402 verify/settle responses.

extensions

Extension framework for x402 protocol extensions.

facilitator

Unified asynchronous interface for x402 payment facilitators.

hooks

Lifecycle hooks for facilitator verify / settle operations.

payment

Typestate lifecycle for a single x402 payment.

resource_server

Resource-server orchestration shared by HTTP and MCP transports.

scheme

Scheme identifiers, registry, and the extensible payment scheme system.

wire

On-the-wire JSON types for the x402 protocol.

Structs

HookSettleContext

Context passed to settle-related hooks.

HookVerifyContext

Context passed to verify-related hooks.

HookedFacilitator

Facilitator decorator that runs registered hooks around verify and settle.

PaymentProblem

A structured payment-problem record returned through wire boundaries.

ResourceServer

Server-side payment orchestrator (Go X402ResourceServer subset).

Enums

ClientError

Client-side error returned when constructing / signing payments.

ErrorReason

Canonical error code returned on the wire when a payment fails.

FacilitatorError

Top-level facilitator failure.

FailureRecovery

Outcome returned by “on failure” hooks, indicating whether recovery happened.

HookDecision

Decision returned by “before” hooks to control whether the operation proceeds.

SettlementError

Settlement-phase failures.

VerificationError

Verification-phase failures.

Traits

AsPaymentProblem

Trait for converting errors into PaymentProblems.

DynFacilitator

Object-safe erasure of Facilitator, suitable for storing as Box<dyn DynFacilitator> or Arc<dyn DynFacilitator>.

DynFacilitatorHooks

Object-safe erasure of FacilitatorHooks.

Facilitator

Unified asynchronous interface for x402 facilitators.

FacilitatorHooks

Lifecycle hooks for facilitator verify and settle operations.

Type Aliases

BoxFuture

Boxed future alias used by DynFacilitator and legacy code.

WirePaymentPayload

Wire payment payload with typed requirements and opaque scheme body.