Live on Avalanche C-Chain

Machine Payments Protocol
on Avalanche

Streaming payment channels for AI agents and services. Deposit once, sign unlimited off-chain vouchers at zero gas, settle when ready. Adapted from Tempo's MPP for any EVM chain.

Try the Demo View on SnowTrace GitHub

Mainnet 0xF1EB69d85897ba945B5E2EbcBAD831bf3671F137

Fuji 0x6e2DD66C1bfb66a2b579D291CdF6EA559E93619b

How It Works

Payment channels let agents pay per-request without a transaction each time. Only the open and settle/close touch the chain.

Open Channel

Payer deposits USDC into the StreamChannel contract, naming the payee.

On-chain ~150k gas

Sign Vouchers

Payer signs EIP-712 cumulative vouchers off-chain. Each voucher says "I owe you X total". Send via HTTP headers.

Zero gas

Settle or Close

Payee submits the latest voucher on-chain to collect. Unused deposit is refunded to payer.

On-chain ~90k gas

⚡ Cumulative Vouchers

Each voucher supersedes the last. Only the final one matters — settle once, not per request.

🔒 Escrowed Deposits

Funds are locked in the contract. Payee can't take more than signed. Payer can reclaim after grace period.

🌐 Any ERC-20 Token

Works with USDC, USDT, WAVAX, or any standard token on Avalanche.

🔗 Chain-Aware IDs

Channel IDs include block.chainid — no cross-chain replay attacks.

Deployed Contracts

Network	Contract	Chain ID	USDC
Mainnet	`0xF1EB69d85897ba945B5E2EbcBAD831bf3671F137`	43114	`0xB97EF9Ef8734C71904D8002F8b6Bc66Dd9c48a6E`
Fuji	`0x6e2DD66C1bfb66a2b579D291CdF6EA559E93619b`	43113	`0x5425890298aed601595a70AB815c96711a31Bc65`

EIP-712 Domain: The contract uses domain name "Tempo Stream Channel" version "1" — matching Tempo's original spec for cross-compatibility.

Need test tokens? Get Fuji AVAX from Core Faucet and test USDC from Aave Faucet (select Fuji network).

Try the MPP API

This is a real API gated by MPP payments. No voucher = 402 rejected. Valid voucher = data returned. Try it.

Controls

localhost:3402

1. Call without payment

Hit the API with no voucher — get 402.

2. Discover pricing

Learn the service's payment terms.

3. Open a payment channel

Connect wallet, approve USDC, deposit into channel.

Not connected

Deposit (USDC)

4. Make paid API calls

Signs a voucher (zero gas), sends via HTTP headers, gets data.

Query

Requests: 0 · Paid: 0.00 USDC (off-chain)

Live Request / Response

Integration Guide

For Services (Accept Payments)

Add MPP payment gating to any HTTP API. Agents discover your pricing via /.well-known/mpp, then send signed vouchers with each request.

service.ts
import express from "express";

// MPP discovery endpoint
app.get("/.well-known/mpp", (req, res) => {
  res.json({
    version: "draft-tempo-stream-00",
    payee: SERVICE_ADDRESS,
    channel_contract: "0xF1EB69d85897ba945B5E2EbcBAD831bf3671F137",
    chain_id: 43114,
    price_per_request: "100000",  // 0.10 USDC
    accepted_tokens: [USDC_ADDRESS],
  });
});

// Paid API endpoint
app.post("/api/data", async (req, res) => {
  const channelId = req.headers["x-mpp-channel-id"];
  const amount    = req.headers["x-mpp-cumulative-amount"];
  const voucher   = req.headers["x-mpp-voucher"];

  if (!channelId || !amount || !voucher) {
    return res.status(402).json({
      error: "Payment Required",
      mpp_info: "GET /.well-known/mpp"
    });
  }

  // Store voucher, serve data, settle later
  storeVoucher(channelId, amount, voucher);
  res.json({ data: "your response here" });
});

agent.ts
import { createWalletClient, http, parseUnits } from "viem";

// 1. Open channel (one-time, on-chain)
const channelId = await walletClient.writeContract({
  address: STREAM_CHANNEL,
  abi: streamChannelAbi,
  functionName: "open",
  args: [payeeAddress, USDC, parseUnits("1", 6), salt, zeroAddress],
});

// 2. Sign vouchers off-chain (zero gas, repeat per request)
const signature = await walletClient.signTypedData({
  domain: {
    name: "Tempo Stream Channel",
    version: "1",
    chainId: 43114,
    verifyingContract: STREAM_CHANNEL,
  },
  types: {
    Voucher: [
      { name: "channelId", type: "bytes32" },
      { name: "cumulativeAmount", type: "uint128" },
    ],
  },
  primaryType: "Voucher",
  message: { channelId, cumulativeAmount: parseUnits("0.10", 6) },
});

// 3. Send to service via HTTP
await fetch("https://api.example.com/data", {
  headers: {
    "X-MPP-Channel-Id": channelId,
    "X-MPP-Cumulative-Amount": "100000",
    "X-MPP-Voucher": signature,
  },
});

HTTP 402 Flow
# 1. Agent makes request without payment
POST /api/data
→ 402 Payment Required
{
  "error": "Payment Required",
  "mpp_info": "GET /.well-known/mpp"
}

# 2. Agent discovers pricing
GET /.well-known/mpp
→ 200 OK
{
  "version": "draft-tempo-stream-00",
  "payee": "0x3d7A...D787",
  "channel_contract": "0xF1EB...F137",
  "chain_id": 43114,
  "price_per_request": "100000",
  "accepted_tokens": ["0xB97E...a6E"]
}

# 3. Agent opens channel on-chain, then sends with voucher
POST /api/data
X-MPP-Channel-Id: 0x9a0b6130...
X-MPP-Cumulative-Amount: 100000
X-MPP-Voucher: 0x1daffe21...
→ 200 OK
{ "data": "..." }

IStreamChannel.sol
interface IStreamChannel {
  struct Channel {
    bool finalized;
    uint64 closeRequestedAt;
    address payer;
    address payee;
    address token;
    address authorizedSigner;
    uint128 deposit;
    uint128 settled;
  }

  function open(
    address payee, address token,
    uint128 deposit, bytes32 salt,
    address authorizedSigner
  ) external returns (bytes32 channelId);

  function settle(
    bytes32 channelId, uint128 cumulativeAmount,
    bytes calldata signature
  ) external;

  function close(...) external;
  function topUp(bytes32, uint256) external;
  function requestClose(bytes32) external;
  function withdraw(bytes32) external;

  function getChannel(bytes32)
    external view returns (Channel memory);
}

Contract Functions

Function	Caller	Description
`open()`	Payer	Deposit tokens and create a new payment channel
`settle()`	Payee	Submit a signed voucher to claim accumulated payment
`topUp()`	Payer	Add more tokens to an existing channel (cancels pending close)
`close()`	Payee	Final settlement + refund remaining deposit to payer
`requestClose()`	Payer	Start 15-minute grace period for unilateral withdrawal
`withdraw()`	Payer	Reclaim unsettled deposit after grace period expires
`getChannel()`	Anyone	Read channel state (view function, no gas)
`computeChannelId()`	Anyone	Compute deterministic channel ID from parameters
`getVoucherDigest()`	Anyone	Get the EIP-712 digest for a voucher (for verification)
`getChannelsBatch()`	Anyone	Read multiple channels in one call

Events

Event	Emitted When
`ChannelOpened`	A new channel is created with a deposit
`Settled`	Payee claims payment via a signed voucher
`TopUp`	Payer adds more funds to a channel
`CloseRequested`	Payer initiates the 15-minute grace period
`CloseRequestCancelled`	Payer tops up, cancelling a pending close
`ChannelClosed`	Channel is finalized (cooperative or after grace)
`ChannelExpired`	Payer withdraws after grace period

Machine Payments Protocol
on Avalanche

How It Works

Open Channel

Sign Vouchers

Settle or Close

⚡ Cumulative Vouchers

🔒 Escrowed Deposits

🌐 Any ERC-20 Token

🔗 Chain-Aware IDs

Deployed Contracts

Try the MPP API

Controls

1. Call without payment

2. Discover pricing

3. Open a payment channel

4. Make paid API calls

Live Request / Response

Integration Guide

For Services (Accept Payments)

Contract Functions

Events

Links

🔍 SnowTrace (Mainnet)

🧪 SnowTrace (Fuji)

📖 MPP Specification

💻 Original Source

Machine Payments Protocolon Avalanche

How It Works

Open Channel

Sign Vouchers

Settle or Close

⚡ Cumulative Vouchers

🔒 Escrowed Deposits

🌐 Any ERC-20 Token

🔗 Chain-Aware IDs

Deployed Contracts

Try the MPP API

Controls

1. Call without payment

2. Discover pricing

3. Open a payment channel

4. Make paid API calls

Live Request / Response

Integration Guide

For Services (Accept Payments)

Contract Functions

Events

Links

🔍 SnowTrace (Mainnet)

🧪 SnowTrace (Fuji)

📖 MPP Specification

💻 Original Source

Machine Payments Protocol
on Avalanche