@t402/evm

EVM (Ethereum Virtual Machine) implementation of the t402 payment protocol using the Exact payment scheme with EIP-3009 TransferWithAuthorization.

Installation

``bash
npm install @t402/evm
`

Overview

This package provides three main components for handling t402 payments on EVM-compatible blockchains:

- Client - For applications that need to make payments (have wallets/signers)
- Facilitator - For payment processors that verify and execute on-chain transactions
- Service - For resource servers that accept payments and build payment requirements

Package Exports

$3

V2 Protocol Support - Modern t402 protocol with CAIP-2 network identifiers

Client:
- ExactEvmClient - V2 client implementation using EIP-3009
- toClientEvmSigner(account) - Converts viem accounts to t402 signers
- ClientEvmSigner - TypeScript type for client signers

Facilitator:
- ExactEvmFacilitator - V2 facilitator for payment verification and settlement
- toFacilitatorEvmSigner(wallet) - Converts viem wallets to facilitator signers
- FacilitatorEvmSigner - TypeScript type for facilitator signers

Service:
- ExactEvmServer - V2 service for building payment requirements

$3

V1 Protocol Support - Legacy t402 protocol with simple network names

Exports:
- ExactEvmClientV1 - V1 client implementation
- ExactEvmFacilitatorV1 - V1 facilitator implementation
- NETWORKS - Array of all supported V1 network names

Supported V1 Networks:
`typescript
[
"abstract", "abstract-testnet",
"base-sepolia", "base",
"avalanche-fuji", "avalanche",
"iotex", "sei", "sei-testnet",
"polygon", "polygon-amoy",
"peaq", "story", "educhain",
"skale-base-sepolia"
]
`

$3

Convenience builder for creating fully-configured EVM clients

Exports:
- createEvmClient(config) - Creates t402Client with EVM support
- EvmClientConfig - Configuration interface

What it does:
- Automatically registers V2 wildcard scheme (eip155:*)
- Automatically registers all V1 networks from NETWORKS
- Optionally applies payment policies
- Optionally uses custom payment selector

Example:
`typescript
import { createEvmClient } from "@t402/evm/client";
import { toClientEvmSigner } from "@t402/evm";
import { privateKeyToAccount } from "viem/accounts";

const account = privateKeyToAccount("0x...");
const signer = toClientEvmSigner(account);

const client = createEvmClient({ signer });
// Ready to use with both V1 and V2!
`

Version Differences

$3


- Network format: CAIP-2 (eip155:8453)
- Wildcard support: Yes (eip155:*)
- Payload structure: Partial (core wraps with metadata)
- Extensions: Full support
- Validity window: 1 hour (default)

$3

- Network format: Simple names (base-sepolia)
- Wildcard support: No (fixed list)
- Payload structure: Complete
- Extensions: Limited
- Validity window: 10 minutes with buffer

Usage Patterns

$3

`typescript
import { createEvmClient } from "@t402/evm/client";
import { wrapFetchWithPayment } from "@t402/fetch";

const client = createEvmClient({ signer: myEvmSigner });
const paidFetch = wrapFetchWithPayment(fetch, client);
`

$3

`typescript
import { t402Client } from "@t402/core/client";
import { ExactEvmClient } from "@t402/evm";
import { ExactEvmClientV1 } from "@t402/evm/v1";

const client = new t402Client()
.register("eip155:*", new ExactEvmClient(signer))
.registerSchemeV1("base-sepolia", new ExactEvmClientV1(signer))
.registerSchemeV1("base", new ExactEvmClientV1(signer));
`

$3

`typescript
import { t402Client } from "@t402/core/client";
import { ExactEvmClient } from "@t402/evm";

const client = t402Client.fromConfig({
schemes: [
{ network: "eip155:*", client: new ExactEvmClient(signer) },
{ network: "base-sepolia", client: new ExactEvmClientV1(signer), t402Version: 1 }
],
policies: [myCustomPolicy]
});
`

Supported Networks

V2 Networks (via CAIP-2):
- eip155:1 - Ethereum Mainnet
- eip155:8453 - Base Mainnet
- eip155:84532 - Base Sepolia
- eip155:* - Wildcard (matches all EVM chains)
- Any eip155: network

V1 Networks (simple names):
See NETWORKS constant in @t402/evm/v1

Asset Support

Supports any ERC-3009 compatible token:
- USDC (primary)
- EURC
- Any token implementing transferWithAuthorization()

Development

`bash


Build

npm run build

Test

npm run test

Integration tests

npm run test:integration

Lint & Format

npm run lint
npm run format
`

Related Packages

- @t402/core - Core protocol types and client
- @t402/evm-core - Shared EVM types and utilities
- @t402/fetch - HTTP wrapper with automatic payment handling
- @t402/svm - Solana implementation
- @t402/ton - TON implementation
- @t402/tron - TRON implementation
- @t402/near - NEAR Protocol implementation
- @t402/aptos - Aptos implementation
- @t402/tezos - Tezos implementation
- @t402/polkadot - Polkadot Asset Hub implementation
- @t402/stacks - Stacks implementation
- @t402/cosmos` - Cosmos (Noble) implementation