# Fee Sponsorship

Fordefi supports fee sponsorship across multiple chains. With fee sponsorship, a designated **fee payer vault** covers the transaction fees on behalf of the **origin vault** that initiates the transaction.

This is useful when you want to abstract gas costs away from your users or consolidate fee payments into a single vault.

## Supported Chains

| Chain | Example Script | Fee Payer Field | Additional Setup |
|  --- | --- | --- | --- |
| EVM | [Link to code](https://github.com/FordefiHQ/api-examples/blob/main/python/simple-api-transfers/evm/sponsored_transactions_7702/sponsored_token_transfer_evm.py) | `vault_id` | Origin vault must be upgraded to an EIP-7702 smart account |
| Solana | [Link to code](https://github.com/FordefiHQ/api-examples/blob/main/python/simple-api-transfers/solana/sponsored_token_transfer_solana.py) | `vault_id` | None |
| Aptos | [Link to code](https://github.com/FordefiHQ/api-examples/blob/main/python/simple-api-transfers/move-chains/aptos/sponsored_fungible_assets_aptos.py) | `vault_id` | None |
| Sui | [Link to code](https://github.com/FordefiHQ/api-examples/blob/main/python/simple-api-transfers/move-chains/sui/sponsored_token_transfer_sui.py) | `vault_id` | None |


## Prerequisites

### 1. Fordefi API Setup

Set up an API User and an API signer by following the [Fordefi API Signer documentation](https://docs.fordefi.com/developers/getting-started/set-up-an-api-signer/api-signer-docker).

### 2. Fordefi Vaults

You need **2 Fordefi vaults** on the target chain:

- **Origin vault**: The vault initiating the transaction
- **Fee payer vault**: The vault that holds the gas token and will pay transaction fees on behalf of the origin vault


### 3. Enable Fee Sponsorship

Enable fee sponsorship in your organization settings through the [Fordefi web console](https://docs.fordefi.com/user-guide/fee_sponsorship#activate-the-feature). Fee sponsorship is always enabled via the Fordefi workspace settings (ask your workspace admin for help).

### 4. EVM Only: Upgrade to Smart Account

For **EVM chains only**, the origin vault must be upgraded to an EIP-7702 smart account before it can use fee sponsorship. The fee payer vault does not require any upgrade. See the [EVM fee sponsorship code examples](https://github.com/FordefiHQ/api-examples/tree/main/python/simple-api-transfers/evm/sponsored_transactions_7702) for details.

## How It Works

All sponsored transactions follow the same pattern across supported chains:

1. Build a transaction request that includes a `details.fee_payer` field pointing to the fee payer vault
2. Sign the request payload with your API User's private key
3. Broadcast the transaction via the Fordefi API


The `fee_payer` field is the key difference from a standard transfer:


```json
"fee_payer": {
    "type": "vault",
    "vault_id": "<FEE_PAYER_VAULT_ID>"
}
```

This field is added inside the `details` object of the transaction request body.