> ## Documentation Index
> Fetch the complete documentation index at: https://docs.avok.xyz/llms.txt
> Use this file to discover all available pages before exploring further.

# Sponsor EVM sends

> Let users pay EVM fees in a token, using your own ERC-4337 bundler and ERC-7677 paymaster.

On EVM, a sponsored send lets the user pay the fee in an ERC-20 token instead of native gas. You
bring your own bundler and paymaster. For the model, see [Sponsorship](/concepts/sponsorship).

## Configure the infrastructure

Set both `bundlerUrl` and `paymasterUrl` on the client config. They are required together. With
only one, the chain falls back to self-pay.

```ts theme={null}
const client = createAvokClient(
  {
    connection,
    bundlerUrl: "https://your-bundler.example",     // ERC-4337, EntryPoint v0.8
    paymasterUrl: "https://your-paymaster.example", // ERC-7677
    requireSponsorship: true, // fail loudly instead of silently self-paying
  },
  wallet,
);
```

Many providers (Pimlico, Alchemy) serve both from one endpoint; pass the same URL twice.

`requireSponsorship: true` makes a fee-token send throw `SponsorshipUnavailableError` (before
anything is signed) if the sponsored rail is not reachable, naming which side is missing. Leave it
`false` (the default) to let such a send degrade silently to self-pay.

## Send with a fee token

Trigger the send through the provider with an EIP-5792 `wallet_sendCalls` request. The per-send fee
token rides in the `paymasterService` capability's `context`:

```ts theme={null}
const provider = client.getEip1193Provider();

const { id } = await provider.request({
  method: "wallet_sendCalls",
  params: [
    {
      chainId: "0x2105", // 8453 (Base), hex; optional, defaults to the active chain
      calls: [{ to: "0xRecipient", value: "0x0", data: "0x" }],
      capabilities: {
        paymasterService: {
          url: "https://your-paymaster.example",
          context: { token: "0xFeeTokenAddress" },
        },
      },
    },
  ],
});
```

A single-token paymaster (for example, Circle USDC) can omit `context.token`; the provider then
falls back to the chain's default registry fee token. If you use wagmi, its `useSendCalls` produces
the same request.

## Confirm which rail ran

The returned `id` is the intent id. Check the rail rather than assuming your configuration took
effect: use `wallet_getCallsStatus`, or on the core send path inspect `receipt.rail`. A sponsored
EVM receipt has `rail: "sponsored"`, an `id` that is a userOpHash, and `status: "pending"` until
the bundler reports a receipt. See [Receipts](/reference/receipts).