Doing Non-Custodial Transactions on Tachyon

Overview

The Tachyon API provides a powerful combination of the /quote endpoint and /submit-signed-tx endpoint that works seamlessly with NEAR’s Chain Signatures technology. This approach allows users to get accurate cost estimates upfront and then submit pre-signed transactions that can be funded and executed efficiently.

Workflow Overview

Step-by-Step Integration

Step 1: Get Transaction Quote

First, obtain a quote for your transaction to understand the costs and gas requirements:


const quoteRequest = {
  to: "0x1234567890abcdef1234567890abcdef12345678",
  callData: "0xa9059cbb000000000000000000000000742d35cc...", // ERC20 transfer data
  value: "0",
  chainId: 1, // Ethereum mainnet
  maxFeePerGas: "20000000000",
  maxPriorityFeePerGas: "2000000000", 
  gasLimit: "21000",
};
 
const quoteResponse = await fetch('https://api.tachyon.rath.fi/api/quote', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
    'api-key': 'your-api-key'
  },
  body: JSON.stringify(quoteRequest)
});
 
const quote = await quoteResponse.json();
console.log('Estimated cost:', quote.costUSD);
console.log('Min Balance Required:', quote.minBalanceRequired);

Step 2: Sign Transaction with Chain Signatures

Use NEAR’s Chain Signatures to sign the transaction. This can be done through:

Direct NEAR Integration: Use NEAR wallet or account to call the MPC service
Tachyon’s Chain Signature Integration: For users who have configured Tachyon with NEAR accounts


// Example using NEAR wallet selector
const signTransaction = async (transactionData, derivationPath) => {
  const wallet = await selector.wallet();
  
  // Prepare transaction for signing
  const unsignedTx = {
    to: transactionData.to,
    value: BigInt(transactionData.value),
    data: transactionData.callData,
    gasLimit: BigInt(transactionData.gasLimit),
    maxFeePerGas: BigInt(transactionData.maxFeePerGas),
    maxPriorityFeePerGas: BigInt(transactionData.maxPriorityFeePerGas)
  };
  
  // Sign with MPC
  const signature = await wallet.signAndSendTransaction({
    receiverId: 'v1.signer',
    actions: [{
      type: 'FunctionCall',
      params: {
        methodName: 'sign',
        args: {
          payload: [hashToSign],
          path: derivationPath,
          key_type: 'Ecdsa'
        },
        gas: '300000000000000',
        deposit: '1000000000000000000000000' // 1 NEAR
      }
    }]
  });
  
  return signature;
};

Step 3: Submit Signed Transaction

Submit the signed transaction along with funding requirements:


const submitSignedRequest = {
  signedTx: "0x02f8b20180843b9aca0085174876e800825208942c169...", // Your signed tx
  chainId: 1,
  fromAddress: "0xYourDerivedAddress", // Address derived from Chain Signatures
  minBalanceRequired: "${quote.minBalanceRequired}", // Minimum balance needed
  
  // Optional: Reference the quote for cost tracking
  quoteReference: quote.id,
  estimatedCost: quote.estimatedCost
};
 
const submitResponse = await fetch('https://api.tachyon.rath.fi/api/submit-signed-tx', {
  method: 'POST', 
  headers: {
    'Content-Type': 'application/json',
    'api-key': 'your-api-key'
  },
  body: JSON.stringify(submitSignedRequest)
});
 
const result = await submitResponse.json();
console.log('Transaction submitted:', result.transactionId);