name: cctp
description: "Circle CCTP for cross-chain USDC transfers. Bridge USDC between Base, Ethereum, Arbitrum, and other chains. Use when building cross-chain payment features."
metadata:
openclaw:
emoji: "🌉"

CCTP (Cross-Chain Transfer Protocol)

Circle's protocol for native USDC transfers between chains. Burns on source, mints on destination — no wrapped tokens.

How It Works

1. Burn USDC on source chain (call TokenMessenger.depositForBurn)
2. Circle attestation service signs the burn
3. Fetch attestation from Circle API
4. Mint USDC on destination chain (call MessageTransmitter.receiveMessage)

Supported Chains

Step 1: Burn on Source Chain

import { encodeFunctionData } from 'viem';

// Approve USDC spend
await walletClient.writeContract({
  address: USDC_SOURCE,
  abi: erc20Abi,
  functionName: 'approve',
  args: [TOKEN_MESSENGER, amount],
});

// Burn USDC
const burnTx = await walletClient.writeContract({
  address: TOKEN_MESSENGER,
  abi: tokenMessengerAbi,
  functionName: 'depositForBurn',
  args: [
    amount,
    DESTINATION_DOMAIN,     // e.g., 6 for Base
    destinationAddress32,   // bytes32 padded address
    USDC_SOURCE,
  ],
});

// Get message hash from burn event
const receipt = await publicClient.waitForTransactionReceipt({ hash: burnTx });
const messageHash = extractMessageHash(receipt);

Step 2: Fetch Attestation

const ATTESTATION_API = 'https://iris-api.circle.com/attestations';

async function waitForAttestation(messageHash: string): Promise<string> {
  while (true) {
    const res = await fetch(`${ATTESTATION_API}/${messageHash}`);
    const data = await res.json();

    if (data.status === 'complete') {
      return data.attestation;
    }

    // Typically takes 10-20 minutes
    await new Promise(r => setTimeout(r, 30000));
  }
}

Step 3: Mint on Destination

const attestation = await waitForAttestation(messageHash);

const mintTx = await destWalletClient.writeContract({
  address: MESSAGE_TRANSMITTER_DEST,
  abi: messageTransmitterAbi,
  functionName: 'receiveMessage',
  args: [messageBytes, attestation],
});

Timing

Agent Use Case

AgentHQ agents on different chains can pay each other:
1. Agent A (Arbitrum) wants to pay Agent B (Base)
2. Agent A burns USDC on Arbitrum via CCTP
3. USDC mints on Base
4. Agent B receives payment, x402 flow completes
5. EAS attestation records the cross-chain payment

References

• references/full-reference.md — Complete CCTP guide, message format, error handling, V2 features
• Docs: https://developers.circle.com/stablecoins/cctp-getting-started

Cross-References

• agent-wallet-management: Cross-chain fund movement
• circle-wallet: Circle wallet integration
• x402: Cross-chain payment settlement