@t402/aptos

Aptos implementation of the t402 payment protocol using the exact-direct payment scheme with Fungible Asset (FA) transfers.

Installation

npm install @t402/aptos
# or
pnpm add @t402/aptos

Overview

This package provides support for USDT/USDC payments on Aptos using the exact-direct scheme with the Fungible Asset standard. The client executes a primary_fungible_store::transfer call directly on-chain, then provides the transaction hash as proof of payment.

Three main components:

• Client - For applications that make payments (have Aptos wallets)
• Facilitator - For payment processors that verify transactions via Aptos REST API
• Server - For resource servers that accept payments and build payment requirements

Supported Networks

Package Exports

Main Package (@t402/aptos)

Constants:

• APTOS_MAINNET_CAIP2 - CAIP-2 identifier for mainnet (aptos:1)
• APTOS_TESTNET_CAIP2 - CAIP-2 identifier for testnet (aptos:2)
• APTOS_DEVNET_CAIP2 - CAIP-2 identifier for devnet (aptos:149)
• APTOS_NETWORKS - Array of supported networks
• FA_TRANSFER_FUNCTION - Transfer function identifier
• DEFAULT_MAINNET_RPC - Default Aptos Labs RPC endpoint

Tokens:

• TOKEN_REGISTRY - Token configurations by network
• getTokenConfig(network, symbol) - Get token by symbol
• getTokenByAddress(network, metadataAddress) - Get token by metadata address
• getSupportedTokens(network) - Get all tokens for network
• getDefaultToken(network) - Get default token (USDT)
• isTokenSupported(network, symbol) - Check token support

Utilities:

• isValidAptosAddress(address) - Validate hex address format
• normalizeAptosAddress(address) - Normalize to 64-char format
• compareAddresses(addr1, addr2) - Compare addresses (case-insensitive)
• isValidTxHash(txHash) - Validate transaction hash
• isAptosNetwork(network) - Check if network is Aptos
• formatAmount(amount, decimals) - Format for display
• parseAmount(amount, decimals) - Parse to smallest units
• extractTransferDetails(tx) - Extract transfer from transaction
• isFATransferTransaction(tx) - Check if tx is FA transfer

Client (@t402/aptos/exact-direct/client)

import { createExactDirectAptosClient } from '@t402/aptos/exact-direct/client';

const client = createExactDirectAptosClient({
  signer: myAptosSigner,
});

Server (@t402/aptos/exact-direct/server)

import { registerExactDirectAptosServer } from '@t402/aptos/exact-direct/server';

registerExactDirectAptosServer(server);

Facilitator (@t402/aptos/exact-direct/facilitator)

import { createExactDirectAptosFacilitator } from '@t402/aptos/exact-direct/facilitator';

const facilitator = createExactDirectAptosFacilitator(signer);

Payment Flow

1. Client requests protected resource
2. Server responds with 402 + payment requirements (network, amount, payTo)
3. Client calls 0x1::primary_fungible_store::transfer with FA metadata
4. Client submits transaction hash as payment proof
5. Facilitator queries Aptos REST API to verify the transaction
6. Facilitator confirms payment matches requirements

Payload Structure

interface ExactDirectAptosPayload {
  txHash: string;           // 0x-prefixed transaction hash
  from: string;             // Sender address (0x...)
  to: string;               // Recipient address
  amount: string;           // Amount in smallest units
  metadataAddress: string;  // FA metadata object address
  version?: string;         // Transaction version (optional)
}

Address Format

Aptos uses hex addresses:

• Prefixed with 0x
• 1-64 hex characters (leading zeros can be omitted)
• Full format: 64 hex characters

Examples:

0x1                                                                (short form)
0x0000000000000000000000000000000000000000000000000000000000000001  (full form)
0xf73e887a8754f540ee6e1a93bdc6dde2af69fc7ca5de32013e89dd44244473cb  (USDT metadata)

Fungible Asset Standard

This package uses Aptos Fungible Asset (FA) standard:

• Modern replacement for legacy Coin module
• Metadata object identifies the asset
• primary_fungible_store::transfer for transfers

// Transfer function call
{
  function: "0x1::primary_fungible_store::transfer",
  arguments: [
    metadataAddress,  // FA metadata object
    recipientAddress, // Recipient
    amount            // Amount in smallest units
  ]
}

Token Metadata Addresses

Development

# Build
pnpm build

# Test
pnpm test

# Test with coverage
pnpm test:coverage

# Lint
pnpm lint

Related Packages

• @t402/core - Core protocol types and client
• @t402/fetch - HTTP wrapper with automatic payment handling
• @t402/evm - EVM chains implementation
• @t402/near - NEAR Protocol implementation