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

# GPv2VaultRelayer API

> Vault relayer contract API for Balancer Vault interactions and token transfers

# GPv2VaultRelayer API

The `GPv2VaultRelayer` contract serves as an intermediary between CoW Protocol's settlement system and Balancer Vault, facilitating fund transfers and swap execution with protocol fees.

## State Variables

```solidity theme={null}
address public immutable creator;
IVault public immutable vault;
```

## Access Control

```solidity theme={null}
modifier onlyCreator {
    require(msg.sender == creator, "GPv2: not creator");
    _;
}
```

All external functions are restricted to the creator (settlement contract) through the `onlyCreator` modifier.

## Functions

### transferFromAccounts

Moves sell token amounts from user accounts to the settlement contract.

```solidity theme={null}
function transferFromAccounts(
    GPv2Transfer.Data[] calldata transfers
) external onlyCreator;
```

Supports three balance types:

| Balance Type | Description                      |
| ------------ | -------------------------------- |
| **ERC20**    | Standard ERC20 token transfers   |
| **External** | Balancer Vault external balances |
| **Internal** | Balancer Vault internal balances |

### batchSwapWithFee

Executes multi-step swaps through Balancer pools and simultaneously collects protocol fees.

```solidity theme={null}
function batchSwapWithFee(
    IVault.BatchSwapStep[] calldata swaps,
    IERC20[] calldata tokens,
    IVault.FundManagement calldata funds,
    int256[] calldata limits,
    uint256 deadline,
    GPv2Transfer.Data calldata feeTransfer
) external onlyCreator returns (int256[] memory tokenDeltas);
```

**Parameters:**

| Name          | Type              | Description                   |
| ------------- | ----------------- | ----------------------------- |
| `swaps`       | `BatchSwapStep[]` | Batch swap steps to execute   |
| `tokens`      | `IERC20[]`        | Token addresses involved      |
| `funds`       | `FundManagement`  | Fund management configuration |
| `limits`      | `int256[]`        | Maximum token amounts         |
| `deadline`    | `uint256`         | Transaction deadline          |
| `feeTransfer` | `Transfer.Data`   | Fee collection transfer       |

**Returns:** `int256[]` - Token deltas indicating amounts sent and received.

The function handles both sell orders (`GIVEN_IN`) and buy orders (`GIVEN_OUT`) swap kinds.

## Security

* Access restricted exclusively to the creator through `onlyCreator`
* Unauthorized calls revert with `"GPv2: not creator"`
* Immutable state prevents tampering
* Users never interact with this contract directly