Transfer Execution

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Overview

1. Get a quote from /getEcdsaSig_native (EVM) or /getEd25519Sig_native (Solana, Aptos, Sui).
2. Fill the contract parameters with it.
3. Call the Cashmere contract on the source chain.
4. Track the transfer with /transactionsmainnet until the destination mint succeeds.

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Step-by-Step (EVM)

const localDomain = 0;        // Ethereum
const destinationDomain = 3;  // Arbitrum
const isNative = false;       // take the fee from the USDC; true pays it in ETH

const res = await fetch(
  'https://gas.cashmere.exchange/getEcdsaSig_native?' +
    new URLSearchParams({
      localDomain: String(localDomain),
      destinationDomain: String(destinationDomain),
      isV2: 'true',
      isNative: String(isNative),
    })
);
if (!res.ok) throw new Error(`Gas API error ${res.status}`);
const quote = await res.json(); // { fee, deadline, signature, isNative, cctpVersion }

import { parseUnits, zeroPadValue, ZeroHash } from 'ethers';

const amount = parseUnits('100', 6); // USDC has 6 decimals

// Circle's fee for V2 Fast (threshold 1000), in basis points, possibly fractional such as 1.3
const circleFees = await fetch(
  `https://iris-api.circle.com/v2/burn/USDC/fees/${localDomain}/${destinationDomain}`
).then(r => r.json());
const { minimumFee } = circleFees.find((f: { finalityThreshold: number }) => f.finalityThreshold === 1000);
const maxFee = (amount * BigInt(Math.ceil(minimumFee * 10)) + 99_999n) / 100_000n; // rounded up

const params = {
  amount,
  maxFee,
  fee: BigInt(quote.fee),
  deadline: BigInt(quote.deadline),
  gasDropAmount: 0n,                 // gas drop is not offered
  destinationDomain,
  minFinalityThreshold: 1000,        // V2 Fast; 2000 from sources without Fast
  recipient: zeroPadValue(destinationAddress, 32),
  solanaOwner: ZeroHash,             // only used when sending to Solana
  isNative,
  hookData: '0x00',                  // Circle rejects empty hook data
  signature: quote.signature,
};

import { Contract } from 'ethers';

const usdc = new Contract(USDC_ADDRESS, ['function approve(address,uint256) returns (bool)'], signer);
const cashmere = new Contract(CASHMERE_CCTP_ADDRESS, CASHMERE_ABI, signer);

// The contract pulls exactly `amount`, and takes the fee out of it when isNative is false
await (await usdc.approve(CASHMERE_CCTP_ADDRESS, params.amount)).wait();

const tx = await cashmere.transferV2(params, { value: params.isNative ? params.fee : 0n });
const receipt = await tx.wait();
if (receipt?.status !== 1) throw new Error('transfer reverted');

​

Step-by-Step (Solana)

1. Request a quote with localDomain=5 and version=2.
2. Encode the recipient as 32 bytes (see Recipient Encoding).
3. Build an Ed25519Program.createInstructionWithPublicKey instruction from the quote’s publicKey, message and signature, and place it right before transfer_v2.
4. Call transfer_v2 with the quote’s fee and deadline unchanged, max_fee from Circle Iris and min_finality_threshold = 2000.

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Permit Variants

• On EVM, transferV2WithPermit takes an EIP-2612 PermitParams struct in place of a separate approve. Sign the permit locally, then call the contract with the same quote.
• Solana, Aptos and Sui have no approval step: the sender signs the transaction that moves the USDC.

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Monitoring Settlement

// Poll until the USDC is minted on the destination chain
async function waitForMint(sender: string, sourceTxHash: string, timeoutMs = 45 * 60_000) {
  const url = `https://kapi.cashmere.exchange/transactionsmainnet?senders=${sender}&limit=10`;
  const giveUp = Date.now() + timeoutMs;

  while (Date.now() < giveUp) {
    const { transactions } = await fetch(url).then(r => r.json());
    const tx = transactions.find((t) => t.source_tx_hash === sourceTxHash);
    if (tx?.destination_tx_status === 'success') return tx;
    if (tx?.destination_tx_status === 'failed') throw new Error(tx.destination_tx_error ?? 'mint failed');
    await new Promise((r) => setTimeout(r, 10_000));
  }
  throw new Error('transfer not settled yet: check it again later');
}

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Common Pitfalls

• Signature mismatch: isV2, isNative and both domains must match the call you make.
• Empty hook data: pass hookData: '0x00'. Circle reverts V2 burns whose hook data is 0x.
• Allowance errors: approve amount USDC before transferV2, or use the permit variant.
• Native fee shortfall: with isNative=true, send at least fee wei as msg.value.
• Expired deadline: request a fresh quote if the transaction isn’t sent within about 100 seconds.
• Wrong recipient format: CCTP accepts any 32 bytes, so a mistake can’t be fixed after the burn. An EVM address sent to Aptos or Sui mints to an account nobody controls, and into Solana the recipient must be the USDC token account.