MPP on Avalanche

Machine Payments Protocol (MPP) streaming payment channels deployed on Avalanche C-Chain. Adapted from Tempo's TempoStreamChannel for standard ERC-20 tokens.

Deployed Contracts

What is this?

Payment channels for AI agents and services. Deposit once, sign unlimited off-chain vouchers at zero gas, settle when ready.

Agent (payer)                         Service (payee)
  |                                      |
  |-- POST /api/data ------------------>|
  |<-- 402 Payment Required ------------|
  |                                      |
  |-- GET /.well-known/mpp ------------>|
  |<-- { payee, price, token } ---------|
  |                                      |
  |  [open channel on-chain, deposit USDC]
  |                                      |
  |-- POST /api/data + voucher -------->|
  |<-- 200 OK + data ------------------|
  |                                      |
  |  (repeat, cumulative amount grows)   |
  |                                      |
  |         [service settles on-chain when ready]

Project Structure

contracts/          Solidity smart contracts (Foundry)
  src/StreamChannel.sol       MPP payment channel (ERC-20 compatible)
  test/StreamChannel.t.sol    22 tests
  script/DeployStreamChannel.s.sol

mpp-example/        TypeScript agent + service example
  src/agent.ts      Payer: opens channel, signs vouchers, calls API
  src/service.ts    Payee: Express server with 402 flow, auto-settles

mpp-site/           Static website with interactive demo
  index.html        Docs + live API console
  app.js            Wallet connection, voucher signing, real API calls

Quick Start

1. Run the service (payee)

cd mpp-example
cp .env.example .env
# Set SERVICE_PRIVATE_KEY in .env
npm install
npm run service

2. Open the website

Visit http://localhost:3402 — the service serves the site and the MPP API.

3. Or run the agent (CLI)

# Set PRIVATE_KEY and PAYEE_ADDRESS in .env
npm run agent

Contract Details

• EIP-712 Domain: "Tempo Stream Channel" v1 (cross-compatible with Tempo)
• Grace Period: 15 minutes (for unilateral close)
• Token: Any ERC-20 (USDC, USDT, WAVAX, etc.)
• Safe Transfers: Handles non-bool-returning tokens (USDT)

How Vouchers Work

Each voucher is an EIP-712 signed message: Voucher(bytes32 channelId, uint128 cumulativeAmount). The cumulative amount only goes up — each voucher supersedes the last. The service only needs to settle the final voucher on-chain.

Build & Test Contracts

cd contracts
forge install  # install forge-std + solady
forge test -vv # 22/22 tests pass

License

MIT