> ## 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.

# AaveBorrower

> Protocol adapter enabling the FlashLoanRouter to access flash loans from Aave V3 pools

## Overview

The `AaveBorrower` contract serves as a protocol adapter between the FlashLoanRouter's generic interface and Aave V3's specific flash loan mechanism. It implements Aave's flash loan receiver interface while maintaining the router's standardized borrowing pattern.

## Contract Details

* **Source**: `src/AaveBorrower.sol`
* **License**: GPL-3.0-or-later
* **Solidity**: ^0.8.28
* **Address**: `0x7d9C4DeE56933151Bc5C909cfe09DEf0d315CB4A` (all networks)
* **Inherits**: `Borrower`, `IAaveFlashLoanReceiver`

## Functions

### flashLoanAndCallBack

```solidity theme={null}
function flashLoanAndCallBack(
    address lender,
    IERC20 token,
    uint256 amount,
    bytes calldata callBackData
) external onlyRouter
```

Initiates a flash loan request to an Aave V3 pool. Only callable by the registered router.

**Parameters:**

* `lender`: Address of the Aave V3 Pool contract
* `token`: ERC-20 token to borrow
* `amount`: Amount of tokens to borrow
* `callBackData`: Data to pass back to the router unchanged

### executeOperation

```solidity theme={null}
function executeOperation(
    address[] calldata assets,
    uint256[] calldata amounts,
    uint256[] calldata premiums,
    address initiator,
    bytes calldata params
) external returns (bool)
```

Aave's callback function invoked after the flash loan funds have been transferred. Notifies the router by calling `borrowerCallBack()`.

**Parameters:**

* `assets`: Array of borrowed token addresses
* `amounts`: Array of borrowed amounts
* `premiums`: Array of flash loan fees
* `initiator`: Address that initiated the flash loan
* `params`: Encoded callback data (passed through unchanged)

**Returns:** `true` to indicate successful execution

### approve

```solidity theme={null}
function approve(
    IERC20 token,
    address target,
    uint256 amount
) external onlySettlementContract
```

Allows the settlement contract to authorize token spending during settlement. Used to approve the Aave pool for repayment.

### triggerFlashLoan (internal)

```solidity theme={null}
function triggerFlashLoan(
    address lender,
    IERC20 token,
    uint256 amount,
    bytes calldata callBackData
) internal override
```

Internal implementation that constructs Aave-specific flash loan parameters and calls `IAavePool.flashLoan()`.

**Key implementation details:**

* Interest rate mode is set to `0` (no debt position, must repay in same transaction)
* Referral code is set to `0` (Aave's referral program is currently inactive)
* Assets and amounts are wrapped in single-element arrays

## Execution Flow

1. Router calls `flashLoanAndCallBack()` on the AaveBorrower
2. AaveBorrower calls `IAavePool.flashLoan()` on the Aave V3 pool
3. Aave transfers the requested tokens to the AaveBorrower
4. Aave invokes `executeOperation()` on the AaveBorrower
5. AaveBorrower calls `router.borrowerCallBack()` to continue execution
6. During settlement, the settlement contract calls `approve()` to authorize Aave pool repayment
7. After settlement, Aave pulls the borrowed amount plus premium via `transferFrom()`

## Repayment Model

Aave uses a "pull" repayment model:

1. Settlement approves the Aave pool to spend the borrower's tokens
2. Aave's flash loan mechanism calls `transferFrom()` to reclaim the principal plus premium
3. If the approval is insufficient or the borrower lacks funds, the transaction reverts

<Warning>
  Always verify that the `lender` address is a legitimate Aave V3 Pool contract. Using an incorrect address could result in loss of funds or failed transactions.
</Warning>

## Integration Notes

* Flash loan premiums on Aave are typically 0.05%-0.09% depending on the asset
* Premiums may vary by network and pool configuration
* Solvers must account for premiums when calculating settlement profitability
* The settlement must include an interaction to approve the Aave pool for repayment

## Security

* `flashLoanAndCallBack()`: Only callable by the registered router
* `approve()`: Only callable by the settlement contract
* `executeOperation()`: Called by Aave within the flash loan flow
* Immutable router and settlement contract references prevent manipulation

## Next Steps

<CardGroup cols={2}>
  <Card title="ERC3156Borrower" icon="file-contract" href="/flash-loan-router/contracts/erc3156-borrower">
    ERC-3156 flash loan adapter
  </Card>

  <Card title="Borrower Base" icon="code" href="/flash-loan-router/contracts/base/borrower">
    Abstract base contract
  </Card>
</CardGroup>