Pre-execution Steps

​

How it works

1. The quote comes back with preExecutionSteps, a list of things to sign. Quotes never need the signatures, so you can show a quote before asking the user for anything.
2. You have the user sign each one.
3. You send the signatures back as preExecutionStepsData on the build request. The build puts them into the transaction.

const quote = await dzap.getZapBundleQuote(request);

// [{ id: 'aave-delegation-with-sig-8453-0x…', type: 'sign', data: { domain, types, primaryType, message } }]
console.log(quote.preExecutionSteps);

const prepared = await dzap.prepareZapPreExecutionData({
  preExecutionSteps: quote.preExecutionSteps,
  signer: walletClient,
  account: account.address,     // optional, read from the signer when left out
});
if (prepared.status !== TxnStatus.success) throw new Error(prepared.errorMsg);

const buildRequest = { ...request, preExecutionStepsData: prepared.preExecutionStepsData };
const route = await dzap.buildZapBundleTx(buildRequest);
const result = await dzap.zap({ request: buildRequest, steps: route.steps, signer: walletClient });

const result = await dzap.zap({ request, preExecutionSteps: quote.preExecutionSteps, signer: walletClient });

​

Types

// What the quote asks for, on quote.preExecutionSteps (and on buildZapTxn / buildZapBundleTx responses)
type ZapPreExecutionStep = {
  id: string;                     // send it back unchanged; it's how the build matches the signature to the step
  type: 'sign';                   // the only kind today
  data: ZapTypedDataPayload;      // { domain, types, primaryType, message }, ready for signTypedData
};

// What you send back, on the request's preExecutionStepsData
type ZapPreExecutionStepData = {
  id: string;
  type: 'sign';
  signature: HexString;
  message: Record<string, unknown>;   // the step's data.message, unchanged
};

// What prepareZapPreExecutionData returns
type ZapPreExecutionResult =
  | { status: TxnStatus.success; code: StatusCodes | number; preExecutionStepsData: ZapPreExecutionStepData[] }
  | { status: Exclude<TxnStatus, TxnStatus.success>; code: StatusCodes; errorMsg: string; error: any };

​

Things to know before you ship it

• It’s a signature, not a transaction. No gas, and the wallet shows it as a typed-data request. Nothing happens on-chain until the built transaction is sent.
• Sign everything in the list, and don’t count on its length. An Aave v3 borrow asks for one signature today. Other markets ask for their own (Aave v4 and Morpho each have an authorization), and most routes return an empty list. If your code loops over whatever comes back, it keeps working when that changes.
• The signature can pin parts of the route. For an Aave borrow, the signed message.value is the amount the build borrows. Change destAmount between quote and build and the build is rejected. Quote again and sign again.
• It expires. The Aave delegation is valid for an hour and tied to the user’s current delegation nonce on that debt token, so any other delegation signed in the meantime invalidates it. Ask for the signature when the user is about to confirm, not when the page loads, and don’t reuse it for a later transaction.
• Building without it fails. The build won’t fall back to something else. It errors until the signatures are there.

​

Without the SDK

"preExecutionStepsData": [{
  "id": "<the step's id>",
  "type": "sign",
  "signature": "0x…",
  "message": { "…": "the step's data.message, unchanged" }
}]

​

Errors

• No signature provided for borrow delegation: the build had no preExecutionStepsData, or it had signatures from a different quote. Sign what the latest quote returned.
• Signed credit delegation (…) does not match the borrow amount: the signed amount and the built amount differ. Either destAmount changed after signing, or you left destAmount out and the maximum dropped below what was signed. Quote and sign again.
• The signature stopped working after a while: it expired, or another delegation used up its nonce. Quote again right before asking the user to sign.