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

# Fee Sponsoring

> Enable gasless transactions by routing submissions through a relayer proxy.

## Overview

By default, Smart Account Kit submits transactions directly via the Stellar RPC. Configure a `relayerUrl` to route submissions through a relayer proxy that sponsors fees - making your app effectively gasless for end users.

## Setup

```typescript theme={null}
const kit = new SmartAccountKit({
  rpcUrl: 'https://soroban-testnet.stellar.org',
  networkPassphrase: 'Test SDF Network ; September 2015',
  accountWasmHash: 'YOUR_WASM_HASH',
  webauthnVerifierAddress: 'YOUR_VERIFIER',
  relayerUrl: 'https://my-relayer.example.com',  // ← add this
});
```

Once configured, all `transfer()`, `signAndSubmit()`, and `executeAndSubmit()` calls automatically route through the relayer.

## Bypassing the Relayer

To use RPC directly for a specific operation:

```typescript theme={null}
// Force RPC for this transfer only
await kit.transfer(tokenContract, recipient, amount, { forceMethod: 'rpc' });
```

## Relayer Protocol

The relayer proxy must accept POST requests with one of two formats:

**For `invokeHostFunction` flows (func + auth):**

```json theme={null}
{ "func": "<xdr>", "auth": ["<xdr>", ...] }
```

**For signed transactions (e.g. deployments):**

```json theme={null}
{ "xdr": "<signed_tx_xdr>" }
```

The relayer wraps the transaction in a fee bump, sponsors fees, and returns the submitted transaction hash.

## Using RelayerClient Directly

Access the relayer client directly via `kit.relayer`:

```typescript theme={null}
if (kit.relayer) {
  // Submit func + auth for fee sponsoring
  const result = await kit.relayer.send(funcXdr, authXdrs);

  // Or submit a signed transaction
  const result = await kit.relayer.sendXdr(signedTx);

  if (result.success) {
    console.log('Hash:', result.hash);
  } else {
    console.error('Error:', result.error, result.errorCode);
  }
}
```

See [RelayerClient](/advanced/relayer-client) for the full API reference.