Developer Quickstart

Which Path?

You want to	Use
Send USDC cross-chain from a backend, bot or script	The Cashmere Agent SDK: one call per transfer, every chain
Let an AI agent (Claude, Hermes, LangChain…) quote and send transfers	The SDK’s MCP server and agent tools
Build the transactions yourself, in another language or a wallet UI	The Gas API and the contracts, as below

With the SDK

Requires Node.js 22 or later.

npm install @cashmerelabs/cashmere-agent-sdk

import { CashmereCCTP } from '@cashmerelabs/cashmere-agent-sdk';

const cctp = new CashmereCCTP({ evm: { privateKey: process.env.EVM_PRIVATE_KEY! } });

// Quote first: fee, CCTP version and duration, nothing is sent
const quote = await cctp.simulate({ from: 'base', to: 'arbitrum', amount: '100' });

// Then send: the SDK fetches the signed quote, approves USDC and waits for confirmation
const { txHash, explorerUrl } = await cctp.transfer({
  from: 'base',
  to: 'arbitrum',
  amount: '100',
  recipient: '0xYourArbitrumAddress',
});

Destination minting is automatic: Cashmere’s relayers mint the USDC to the recipient once the source transaction confirms.

Without the SDK (EVM)

You need an RPC endpoint and a wallet holding USDC and some gas on the source chain, plus the addresses from Contract Addresses. No API key is required.

1. Get a Quote
2. Build Params
3. Send

const isNative = true; // pay the Cashmere fee in the source chain's gas token; false takes it from the USDC

const response = await fetch(
  'https://gas.cashmere.exchange/getEcdsaSig_native?' +
    new URLSearchParams({
      localDomain: '6',            // Base
      destinationDomain: '3',      // Arbitrum
      isV2: 'true',                // transferV2
      isNative: String(isNative),
    })
);
if (!response.ok) throw new Error(`Gas API error ${response.status}`);
const quote = await response.json(); // { fee, deadline, signature, isNative, cctpVersion }

The quote is valid for about 100 seconds. Its fee and deadline are signed: pass them unchanged.

import { zeroPadValue, parseUnits, 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/6/3').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 disabled
  destinationDomain: 3,
  minFinalityThreshold: 1000,                        // V2 Fast; 2000 from chains without Fast
  recipient: zeroPadValue(recipientAddress, 32),
  solanaOwner: ZeroHash,                             // only used when sending to Solana
  isNative,
  hookData: '0x00',                                  // must be non-empty: Circle rejects 0x
  signature: quote.signature,
};

Bridging into Solana (destinationDomain = 5)? Set recipient to the destination wallet’s USDC associated token account (ATA) and solanaOwner to the wallet, both as 32-byte hex. Cashmere’s relayers create the ATA if it doesn’t exist. See Recipient Encoding.

import { ethers } from 'ethers';

const provider = new ethers.JsonRpcProvider(process.env.RPC_URL);
const signer = new ethers.Wallet(process.env.PRIVATE_KEY!, provider);
const cashmere = new ethers.Contract(CASHMERE_CCTP_ADDRESS, CASHMERE_ABI, signer);
const usdc = new ethers.Contract(USDC_ADDRESS, ['function approve(address,uint256) returns (bool)'], signer);

// The contract pulls `amount` and takes its fee out of it
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');

Units
amount and maxFee are USDC base units (6 decimals). The quote’s fee is USDC base units when isNative=false, and otherwise the source chain’s smallest native unit: wei on EVM chains (18), lamports on Solana (9), MIST on Sui (9), octas on Aptos (8).

Without the SDK (Solana)

Request the quote from /getEd25519Sig_native with localDomain=5 and version=2. Always pass version: without it the signed message has no version byte and the program rejects it.
Encode the recipient as 32 bytes (see Recipient Encoding).
Put an Ed25519Program instruction with the quote’s publicKey, message and signature right before transfer_v2, in one VersionedTransaction that uses the Cashmere lookup table 865YCTTsymGpBjLMTvjd3T3RCGT8yvxnAHhyKZqRFfLi.
Pass the quote’s fee and deadline unchanged, max_fee from Circle Iris and min_finality_threshold = 2000 (Solana sends V2 Norm).

import { Ed25519Program } from '@solana/web3.js';

const quote = await fetch(
  'https://gas.cashmere.exchange/getEd25519Sig_native?localDomain=5&destinationDomain=6&isNative=true&version=2',
).then(r => r.json());

const ed25519Ix = Ed25519Program.createInstructionWithPublicKey({
  publicKey: Buffer.from(quote.publicKey.slice(2), 'hex'),
  message: Buffer.from(quote.message.slice(2), 'hex'),
  signature: Buffer.from(quote.signature.slice(2), 'hex'),
});

The full transaction is in Smart Contracts → Solana.

Without the SDK (Aptos)

Request the quote with localDomain=9 and version=2.
Call transfer_v2_outer on 0xe49afb1896889e3e1dd7bcbb9e31d1df8221899d3d368e98588ac6b4d84b136d::transfer with the quote’s fee and deadline, max_fee from Circle Iris, min_finality_threshold = 2000 and the signature as a byte array.

The full payload is in Smart Contracts → Aptos.

Without the SDK (Sui)

Request the quote with localDomain=8 and version=2.
In one transaction, call prepare_deposit_for_burn_v2 on package 0x7eab670b…, then Circle’s deposit_for_burn_with_package_auth, the USDC handler’s burn and complete_burn.

The full transaction, with every object ID, is in Smart Contracts → Sui.

Monitor the Outcome

The transactions API lists transfers with their source and destination status:

curl "https://kapi.cashmere.exchange/transactionsmainnet?senders=0xYourAddress&limit=20"

A transfer is complete when its destination status is success. See Backend APIs for every field.

Next Steps

Backend APIs: the Gas API and transactions API in detail.
Smart Contracts: per-chain entry points, signed payloads and errors.
Agent Integration: the MCP server, the agent skill and framework tools.

Welcome

Overview

Products

Goat Street

Goat LP

Developer Resources

API Reference

Which Path?

With the SDK

Without the SDK (EVM)

Without the SDK (Solana)

Without the SDK (Aptos)

Without the SDK (Sui)

Monitor the Outcome

Next Steps

​Which Path?

​With the SDK

​Without the SDK (EVM)

​Without the SDK (Solana)

​Without the SDK (Aptos)

​Without the SDK (Sui)

​Monitor the Outcome

​Next Steps

Which Path?

With the SDK

Without the SDK (EVM)

Without the SDK (Solana)

Without the SDK (Aptos)

Without the SDK (Sui)

Monitor the Outcome

Next Steps