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Sponsor gas

Gas fees are a significant barrier to entry for new users. With Gas Sponsorship, you can eliminate this friction by covering transaction costs for your users.

When a user requests gas sponsorship using a configured policy, the policy engine will determine if that transaction is eligible for sponsorship. If eligible, when the user sends the transaction the Gas Manager will pay for the gas fee upfront. The Gas Manager will make a note of the sponsored cost and bill the sponsoring developer in fiat.

@alchemy/wallet-apis (v5.x.x) is currently in beta but is the recommended replacement for @account-kit/wallet-client (v4.x.x). If you run into any issues, please reach out.

Use the paymaster capability on the smart wallet client sendCalls or prepareCalls actions.

sendCalls.ts
import { client, config } from "./client.ts";
 
try {
  // Send a sponsored transaction
  const { id } = await client.sendCalls({
    capabilities: {
      paymaster: {
        policyId: config.policyId,
      },
    },
    calls: [
      {
        to: "0x0000000000000000000000000000000000000000",
        value: BigInt(0),
        data: "0x",
      },
    ],
  });
 
  console.log(id);
} catch (error) {
  console.error(error);
}
Using @account-kit/wallet-client (v4.x.x)?

The examples on this page use @alchemy/wallet-apis (v5.x.x). If you're using @account-kit/wallet-client (v4.x.x), the client setup looks like this:

client.ts (v4.x.x)
import { LocalAccountSigner } from "@aa-sdk/core";
import { createSmartWalletClient } from "@account-kit/wallet-client";
import { alchemy, sepolia } from "@account-kit/infra";
 
const signer = LocalAccountSigner.privateKeyToAccountSigner("0xYOUR_PRIVATE_KEY" as const);
 
export const client = createSmartWalletClient({
  transport: alchemy({ apiKey: "YOUR_API_KEY" }),
  chain: sepolia,
  signer,
  account: signer.address, // can also be passed per action as `from` or `account`
  // Optional: sponsor gas for your users (see "Sponsor gas" guide)
  policyId: "YOUR_POLICY_ID", 
});

Key v4.x.x differences:

  • Account address must be specified on the client or per action (from or account). In v5.x.x, the client automatically uses the signer's address as the account address via EIP-7702.
  • Chain imports come directly from @account-kit/infra instead of viem/chains.
  • Numeric values use hex strings: value: "0x0" instead of value: BigInt(0).
  • In v4.x.x, the paymaster capability on prepareCalls or sendCalls is called paymasterService instead of paymaster, or you can set the policyId directly on the client.
  • Signers use LocalAccountSigner / WalletClientSigner from @aa-sdk/core. In v5.x.x, a viem LocalAccount or WalletClient is used directly.

See the full migration guide for a complete cheat sheet.

Usage with prepare calls

Gas sponsorship also works with the prepare calls methods in the various frameworks. Usage of the capability will be the same as when using send calls. It is recommended to use prepare calls if you want to inspect the prepared call prior to prompting the user for signature.

See the prepareCalls SDK reference for full parameter descriptions.

Multiple policy IDs

Developers can configure multiple policy IDs for use in gas sponsorship. The backend will choose the first policy ID that where the transaction is eligible for sponsorship. This is done by passing an array of policy IDs instead of a single policy ID to the sponsor gas capability. See the wallet_prepareCalls API parameters for reference to the paymasterService.policyIds parameter.

Build more:

Troubleshooting:

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