Sending Sponsored Transactions (Construction, Signing, Broadcast, Gasless, Gas Abstraction)

Guide for sending sponsored EVM transactions using @turnkey/core for custom frameworks, Node.js servers, or full manual control.

Overview

This functionality is in closed beta - please reach out to us if you are interested in integrating!

Traditionally, sending blockchain transactions onchain has been painful:

• You need to fund wallets with native gas tokens, creating onboarding friction
• Network congestion and gas spikes can cause transactions to stall or get dropped altogether

Turnkey reduces this to a couple of API calls. We handle gassing and our battle-tested broadcast logic ensures inclusion even under adverse network conditions. You and your users never touch gas tokens or deal with stuck transactions.

Chain Support:

• Base - eip155:8453
• Polygon - eip155:137
• Ethereum - eip155:1 (Coming soon)

Interested in another chain? Reach out to us!

Concepts

Gas sponsorship (aka gas abstraction, gasless transactions, fee abstraction)

A single endpoint lets you toggle between standard EIP-1559 transactions and sponsored transactions. EIP-1559 is the modern Ethereum fee model where transactions specify a base fee (determined by network congestion) and a priority fee (a tip to validators for faster inclusion). With sponsorship enabled, your users never need to hold native tokens to pay these fees—Turnkey covers them. Set sponsor: true to enable sponsorship.

Construction and Broadcast

A successful EVM transaction requires several components:

• Transaction construction: assembling the payload (recipient, value, calldata)
• Nonce, gas and tip fee: setting the correct nonce to order transactions, estimating gas usage and tip fees to ensure inclusion even during network congestion
• Signature: cryptographically signing the transaction with the sender’s private key
• Broadcast: submitting the signed transaction to the network and monitoring for inclusion

Turnkey handles all of this for you. Whether or not you use sponsorship, you pass through minimal payloads that define the contents of your transaction and we take care of construction, signing, and broadcast. We auto-fill any fields you omit.

This endpoint supports arbitrary EVM transactions, not just simple sends. You can interact with smart contracts, deploy contracts, or execute any valid EVM operation.

Transaction status and enriched transaction errors

After you send a transaction, Turnkey monitors its status until it fails or gets included in a block.

For transactions that experience reversion errors, Turnkey runs a transaction simulation to produce structured execution traces and decode common revert reasons. The result: actionable error messages that tell you exactly what went wrong, so you can debug and fix issues quickly instead of parsing opaque hex data.

Spend limits

Turnkey provides tools to manage your gas sponsorship budget. You configure USD gas limits at two levels: across all orgs and per sub-org. This gives you control over both total spend and per-user spend. You can set limit values and time windows through the dashboard.

You can query current gas usage and limits through our endpoints.

Policy engine

You can write policies against both sponsored and non-sponsored transactions using the normal eth.tx namespace in Turnkey’s policy DSL. This means you can seamlessly switch between sponsored and non-sponsored transactions and still use the same policies.

Note: Turnkey sets all gas-related fields to 0 for sponsored transactions.

Billing

Turnkey passes gas costs through to you and includes them as a line item at the end of the month. You pay based on the USD value of gas at time of broadcast; Turnkey internalizes the inventory risk of gas token price changes. Our battle-tested gas estimation aims to be cost efficient while ensuring quick transaction inclusion.

Advanced

Gas sponsorship smart contracts

We could not find a satisfactory setup for gas sponsorship contracts that were both fast and safe, so we made our own. The contracts are open source and you can check them out on github.

Based on our benchmarks, these are the most efficient gas sponsorship contracts on the market. They achieve this through optimized logic, calldata encoding, and using assembly extensively, which reduces gas overhead per sponsored transaction. The result: lower costs for you and faster execution for your users.

Security

Some gas sponsorship setups by other providers are subject to replay attacks. If a malicious actor compromises the provider infrastructure, they can replay the gas sponsorship request multiple times with different nonces to create multiple transactions from a single request. Concretely, this means if Bob signs a request to send Alice 1 ETH, a malicious actor could replay that request many times, draining all of Bob’s ETH.

At Turnkey, we never cut corners on security: we perform transaction construction in enclaves, and as long as the request includes the relevant nonce, only one transaction can be created from it. Since the user’s authenticator signs requests and the enclave verifies signatures, a malicious actor cannot modify or replay the request. This is inline with Turnkey’s core system design principal: everything can be compromised outside of the enclaves and funds will still be safe.

By default, our SDKs include a special gas station nonce for sponsored transaction requests.

RPCs

Turnkey’s send transaction and transaction status endpoints eliminate the need for third-party RPC providers. You save costs and reduce latency because we holistically incorporate internal data and minimize calls.

SDK Overview

The SDK primarily abstracts three endpoints: eth_send_transaction, get_send_transaction_status, and get_gas_usage.

You can sign and broadcast transactions in two primary ways:

1. Using the React handler (handleSendTransaction) from @turnkey/react-wallet-kit This gives you:

   • modals
   • spinner + chain logo
   • success screen
   • explorer link
   • built-in polling

2. Using low-level functions in @turnkey/core You manually call:

   • ethSendTransaction → submit
   • pollTransactionStatus → wait for inclusion

This page walks you through the @turnkey/core flow with full code examples. For using the React handler, see Sending Sponsored Transactions (React).

---

Using @turnkey/core directly

For custom frameworks, Node.js servers, or full manual control.

You will call:

ethSendTransaction(params)

→ returns { sendTransactionStatusId }

pollTransactionStatus(params)

→ returns { txHash, status }

Step 1 — Create a client

import { Turnkey } from "@turnkey/core";

const client = new Turnkey({
  apiBaseUrl: "https://api.turnkey.com",
  defaultOrganizationId: process.env.TURNKEY_ORG_ID,
});

---

Step 2 — Submit the transaction

const sendTransactionStatusId  = await client.ethSendTransaction({
  walletAccount,
  from: walletAccount.address,
  to: "0xRecipient",
  caip2: "eip155:8453",
  sponsor: true,
  value: "0",
  data: "0x",
  nonce: "0",
});

---

Step 3 — Wait for inclusion

const pollResult = await client?.pollTransactionStatus({
  sendTransactionStatusId,
});

if (!pollResult) {
  throw new TurnkeyError(
    "Polling returned no result",
    TurnkeyErrorCodes.SIGN_AND_SEND_TRANSACTION_ERROR,
  );
}

const { eth } = pollResult;
const txHash = eth?.txHash;
if (!txHash) {
  throw new TurnkeyError(
    "Missing txHash in transaction result",
    TurnkeyErrorCodes.SIGN_AND_SEND_TRANSACTION_ERROR,
  );
}
console.log(txHash)

---

ethSendTransaction Implementation

/**
 * Signs and submits an Ethereum transaction using Turnkey.
 *
 * Behavior:
 * - Constructs transaction intent (sponsored or EIP-1559)
 * - Submits via Turnkey
 * - Returns { sendTransactionStatusId }
 *
 * Does NOT poll — caller must poll via pollTransactionStatus.
 */
ethSendTransaction = async (
  params: EthSendTransactionParams
): Promise<string> => {
  const {
    organizationId,
    from,
    to,
    caip2,
    sponsor,
    value,
    data,
    nonce,
    gasLimit,
    maxFeePerGas,
    maxPriorityFeePerGas,
    walletAccount,
  } = params;

  return withTurnkeyErrorHandling(
    async () => {
      const intent = {
        from,
        to,
        caip2,
        ...(value ? { value } : {}),
        ...(data ? { data } : {}),
      };

      if (sponsor) {
        intent["sponsor"] = true;
      } else {
        if (nonce) intent["nonce"] = nonce;
        if (gasLimit) intent["gasLimit"] = gasLimit;
        if (maxFeePerGas) intent["maxFeePerGas"] = maxFeePerGas;
        if (maxPriorityFeePerGas)
          intent["maxPriorityFeePerGas"] = maxPriorityFeePerGas;
      }

      const resp = await this.httpClient.ethSendTransaction({
        ...intent,
        ...(organizationId && { organizationId }),
      });

      return { sendTransactionStatusId: resp.sendTransactionStatusId };
    },
    {
      errorMessage: "Failed to submit transaction",
      errorCode: TurnkeyErrorCodes.SIGN_AND_SEND_TRANSACTION_ERROR,
    }
  );
};

---

pollTransactionStatus Implementation

/**
 * Polls Turnkey until a transaction reaches a terminal state.
 *
 * Terminal states:
 * - COMPLETED / INCLUDED → resolves { txHash, status }
 * - FAILED / CANCELLED → rejects
 */
pollTransactionStatus({
  httpClient,
  organizationId,
  sendTransactionStatusId,
}: PollTransactionStatusParams): Promise<{
  txHash: string;
  status: string;
}> {
  return withTurnkeyErrorHandling(
    async () => {
      return new Promise((resolve, reject) => {
        const ref = setInterval(async () => {
          try {
            const resp = await httpClient.getSendTransactionStatus({
              organizationId,
              sendTransactionStatusId,
            });

            const status = resp?.txStatus;
            const txHash = resp?.eth?.txHash;
            const txError = resp?.txError;

            if (!status) return;

            if (txError || status === "FAILED" || status === "CANCELLED") {
              clearInterval(ref);
              reject(txError || `Transaction ${status}`);
              return;
            }

            if (status === "COMPLETED" || status === "INCLUDED") {
              clearInterval(ref);
              resolve({ txHash: txHash!, status });
            }
          } catch (e) {
            console.warn("polling error:", e);
          }
        }, 500);
      });
    },
    {
      errorMessage: "Failed to poll transaction status",
      errorCode: TurnkeyErrorCodes.SIGN_AND_SEND_TRANSACTION_ERROR,
    }
  );
}

---

Checking Gas Usage

You can configure gas limits for both sub-orgs and all orgs. We recommend checking sub-org gas usage against the limit on the client side so your application can handle edge cases when approaching or exceeding the gas limit.

You may also want to monitor your all org gas usage regularly to see if you are approaching your gas limit.

const resp = await httpClient?.getGasUsage({})
if (resp?.usageUsd! > resp?.windowLimitUsd!) { // you can also configure this to be a threshold
  console.error("Gas usage limit exceeded for sponsored transactions");
  return
}