@t402/aptos

Aptos blockchain implementation for T402 payments using the Fungible Asset standard.

Installation

pnpm add @t402/aptos

Overview

The @t402/aptos package enables T402 payments on Aptos using the Move-based Fungible Asset (FA) standard. It uses the exact-direct scheme — the client executes the transfer directly on-chain via primary_fungible_store::transfer.

Key features:

Fungible Asset standard — Move-native token transfers
Direct settlement — client submits the transfer directly
Metadata-based addressing — tokens identified by FA metadata address

Network IDs

Network	CAIP-2 ID	Chain ID	RPC Endpoint
Mainnet	`aptos:1`	1	`https://fullnode.mainnet.aptoslabs.com/v1`
Testnet	`aptos:2`	2	`https://fullnode.testnet.aptoslabs.com/v1`
Devnet	`aptos:149`	149	`https://fullnode.devnet.aptoslabs.com/v1`

Client Usage

import { ExactDirectAptosClient } from '@t402/aptos/exact-direct/client'
 
const client = new ExactDirectAptosClient({
  address: '0x1234...abcd',
  signAndSubmitTransaction: async (payload) => {
    // Use your Aptos wallet (Petra, Martian, etc.)
    const result = await wallet.signAndSubmitTransaction(payload)
    return result.hash
  }
})
 
const payload = await client.createPaymentPayload(2, requirements)

Server Usage

import { ExactDirectAptosServer } from '@t402/aptos/exact-direct/server'
 
const server = new ExactDirectAptosServer({
  rpcUrl: 'https://fullnode.mainnet.aptoslabs.com/v1'
})
 
const enhanced = await server.enhancePaymentRequirements(baseRequirements)

Facilitator Usage

import { ExactDirectAptosFacilitator } from '@t402/aptos/exact-direct/facilitator'
 
const facilitator = new ExactDirectAptosFacilitator({
  rpcUrl: 'https://fullnode.mainnet.aptoslabs.com/v1'
})
 
const result = await facilitator.verify(payload, requirements)
const settled = await facilitator.settle(payload, requirements)

PaymentRequirements

const requirements = {
  scheme: 'exact-direct',
  network: 'aptos:1',
  amount: '1000000', // 1 USDT (6 decimals)
  asset: '0xf73e887a8754f540ee6e1a93bdc6dde2af69fc7ca5de32013e89dd44244473cb', // FA metadata address
  payTo: '0xRecipientAddress...',
  maxTimeoutSeconds: 600
}

Payment Flow

Client builds a primary_fungible_store::transfer transaction
Client signs and submits to the Aptos network
Transaction executes the Move entry function
Client returns the txHash as proof
Facilitator verifies the transaction via REST API

Aptos uses the Fungible Asset standard (not legacy Coin). The asset field in requirements is the FA metadata address, not a module address.

Token Addresses (FA Metadata)

Token	Network	Metadata Address	Decimals
USDT	Mainnet	`0xf73e887a8754f540ee6e1a93bdc6dde2af69fc7ca5de32013e89dd44244473cb`	6
USDC	Mainnet	`0xbae207659db88bea0cbead6da0ed00aac12edcdda169e591cd41c94180b46f3b`	6
USDT	Testnet	`0xf73e887a8754f540ee6e1a93bdc6dde2af69fc7ca5de32013e89dd44244473cb`	6

Payload Structure

interface ExactDirectAptosPayload {
  txHash: string;           // Aptos transaction hash
  from: string;             // sender address (0x format)
  to: string;               // recipient address
  amount: string;           // amount as string
  metadataAddress: string;  // FA metadata address
}

Transaction Details

The transfer uses Move’s entry function:

0x1::primary_fungible_store::transfer

With arguments:

metadata_address — FA metadata object address
recipient — destination address
amount — transfer amount (u64)

Default gas configuration:

Max gas: 100,000 units
Gas price: 100 octas
Expiration: 600 seconds

Error Codes

Code	Description
`invalid_payload_structure`	Missing txHash, from, to, amount, or metadataAddress
`network_mismatch`	Chain ID doesn’t match requirements
`amount_mismatch`	Transferred amount less than required
`recipient_mismatch`	Transfer recipient doesn’t match payTo
`asset_mismatch`	FA metadata address doesn’t match
`transaction_not_found`	Transaction hash not found
`transaction_failed`	Transaction executed but failed (VM error)

Example: Full Integration

import { t402Client } from '@t402/fetch'
import { registerExactDirectAptosClient } from '@t402/aptos/exact-direct/client'
 
const client = new t402Client()
registerExactDirectAptosClient(client, {
  address: wallet.address,
  signAndSubmitTransaction: wallet.signAndSubmitTransaction
})
 
const response = await client.fetch('https://api.example.com/premium')

Go SDK

import "github.com/t402-io/t402/sdks/go/mechanisms/aptos"
 
// Client
client := aptos.NewExactDirectAptosScheme(signer, &aptos.Config{
    MaxGasAmount: 100000,
    GasUnitPrice: 100,
})
payload, err := client.CreatePaymentPayload(ctx, requirements)
 
// Facilitator
facilitator := aptos.NewExactDirectAptosFacilitator(rpcURL)
result, err := facilitator.Verify(ctx, payload, requirements)

@t402/near @t402/tezos