t402 TypeScript SDK

Version 2.5.0 - TypeScript implementation of the t402 Payment Protocol.

Installation

# Core packages
pnpm add @t402/core @t402/evm

# Server frameworks
pnpm add @t402/express   # Express.js
pnpm add @t402/next      # Next.js
pnpm add @t402/hono      # Hono
pnpm add @t402/fastify   # Fastify

# Client libraries
pnpm add @t402/fetch     # Fetch API
pnpm add @t402/axios     # Axios

# UI components
pnpm add @t402/paywall   # Universal paywall
pnpm add @t402/react     # React hooks/components
pnpm add @t402/vue       # Vue composables/components

# WDK (gasless payments, bridging)
pnpm add @t402/wdk-gasless  # ERC-4337
pnpm add @t402/wdk-bridge   # LayerZero
pnpm add @t402/wdk-multisig # Safe multi-sig

# CLI tool
pnpm add -g @t402/cli
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Package Architecture

@t402/core              Core types, client, server, facilitator abstractions
@t402/extensions        Bazaar, Sign-In-With-X extensions

Mechanisms (Chain-specific payment implementations):
@t402/evm               EIP-3009, ERC-4337, USDT0 bridge for EVM chains
@t402/svm               Solana SPL token support
@t402/ton               TON Jetton (TEP-74) support
@t402/tron              TRON TRC-20 support
@t402/near              NEAR NEP-141 support
@t402/aptos             Aptos Fungible Asset support
@t402/tezos             Tezos FA2 support
@t402/polkadot          Polkadot Asset Hub support
@t402/stacks            Stacks SIP-010 support (Bitcoin L2)
@t402/cosmos            Cosmos/Noble support

HTTP Integrations:
@t402/express           Express.js middleware
@t402/hono              Hono middleware
@t402/fastify           Fastify middleware
@t402/next              Next.js integration
@t402/fetch             Fetch API wrapper
@t402/axios             Axios interceptor

UI Components:
@t402/paywall           Universal payment wall
@t402/react             React hooks and components
@t402/vue               Vue composables and components

WDK (Wallet Development Kit):
@t402/wdk               Tether WDK integration
@t402/wdk-gasless       ERC-4337 gasless payments
@t402/wdk-bridge        LayerZero cross-chain bridging
@t402/wdk-multisig      Safe multi-sig support
@t402/wdk-ton           TON wallet management
@t402/wdk-ton-gasless   Gasless TON transactions via relay
@t402/wdk-tron-gasfree  Gas-free TRON USDT transfers
@t402/wdk-defi          DeFi pre-payment processor
@t402/wdk-protocol      High-level T402Protocol

Mobile:
@t402/react-native      React Native SDK with PaymentSheet

Mechanisms (Additional):
@t402/btc               Bitcoin (PSBT + Lightning)

Transports:
@t402/a2a               Agent-to-Agent transport

Tools:
@t402/mcp               AI Agent MCP server
@t402/cli               Command-line tools
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Quick Start

Client (Make Payments)

import { t402Client, wrapFetchWithPayment } from "@t402/fetch";
import { registerExactEvmScheme } from "@t402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

const client = new t402Client();

registerExactEvmScheme(client, {
  signer: privateKeyToAccount(process.env.PRIVATE_KEY as `0x${string}`),
});

const fetchWithPayment = wrapFetchWithPayment(fetch, client);
const response = await fetchWithPayment("https://api.example.com/data");
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Server (Require Payments)

import express from "express";
import { paymentMiddleware, t402ResourceServer } from "@t402/express";
import { ExactEvmScheme } from "@t402/evm/exact/server";

const app = express();

app.use(
  paymentMiddleware(
    {
      "GET /api/data": {
        accepts: [
          { scheme: "exact", price: "$0.01", network: "eip155:8453", payTo: "0x..." },
        ],
        description: "Premium API data",
      },
    },
    new t402ResourceServer(facilitatorClient)
      .register("eip155:8453", new ExactEvmScheme()),
  ),
);
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Gasless Payments (ERC-4337)

import { SafeSmartAccount, createBundlerClient, createPaymaster } from "@t402/evm/erc4337";

const safeAccount = new SafeSmartAccount({
  owner: privateKeyToAccount(ownerPrivateKey),
  chainId: 8453,
});

const bundler = createBundlerClient({ provider: "pimlico", apiKey, chainId: 8453 });
const paymaster = createPaymaster({ provider: "pimlico", apiKey, chainId: 8453 });

const callData = safeAccount.encodeExecute(targetAddress, 0n, data);
const userOp = await bundler.buildUserOperation({ sender: smartAccountAddress, callData });
const hash = await bundler.sendUserOperation({ ...userOp, signature });
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Cross-Chain Bridge

import { Usdt0Bridge, LayerZeroScanClient } from "@t402/evm";

const bridge = new Usdt0Bridge(signer, "arbitrum");

const quote = await bridge.quote({
  fromChain: "arbitrum",
  toChain: "ethereum",
  amount: 100_000000n,
  recipient: "0x...",
});

const result = await bridge.send({ ...quote });

const scanClient = new LayerZeroScanClient();
await scanClient.waitForDelivery(result.messageGuid);
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MCP Server (AI Agents)

# Run MCP server
npx @t402/mcp

# Claude Desktop config
{
  "mcpServers": {
    "t402": {
      "command": "npx",
      "args": ["@t402/mcp"],
      "env": { "T402_DEMO_MODE": "true" }
    }
  }
}
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Supported Networks

Chain	Token	CAIP-2 Identifier
Ethereum	USDT0	eip155:1
Base	USDT0	eip155:8453
Arbitrum	USDT0	eip155:42161
Optimism	USDT0	eip155:10
Ink	USDT0	eip155:57073
Solana	USDC	solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp
TON	USDT	ton:mainnet
TRON	USDT	tron:mainnet

Development

# Install dependencies
pnpm install

# Build all packages
pnpm build

# Run tests
pnpm test

# Run linting
pnpm lint

# Type checking
pnpm typecheck
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Monorepo Structure

typescript/
├── packages/
│   ├── core/              # @t402/core
│   ├── extensions/        # @t402/extensions
│   ├── a2a/               # @t402/a2a
│   ├── mechanisms/        # @t402/evm, @t402/svm, @t402/ton, @t402/tron, @t402/btc, etc.
│   ├── http/              # @t402/express, @t402/next, @t402/hono, etc.
│   ├── wdk/               # @t402/wdk
│   ├── wdk-gasless/       # @t402/wdk-gasless
│   ├── wdk-bridge/        # @t402/wdk-bridge
│   ├── wdk-multisig/      # @t402/wdk-multisig
│   ├── wdk-ton/           # @t402/wdk-ton
│   ├── wdk-ton-gasless/   # @t402/wdk-ton-gasless
│   ├── wdk-tron-gasfree/  # @t402/wdk-tron-gasfree
│   ├── wdk-defi/          # @t402/wdk-defi
│   ├── wdk-protocol/      # @t402/wdk-protocol
│   ├── react-native/      # @t402/react-native
│   ├── mcp/               # @t402/mcp
│   └── cli/               # @t402/cli
└── pnpm-workspace.yaml
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License

Apache 2.0 - See LICENSE for details.