FlashLoanRouter

Overview

The FlashLoanRouter is a solver contract that coordinates flash loans with CoW Protocol settlements. It serves as the central entry point for requesting flash loans and executing settlements atomically. The router manages three primary actors:

Solvers: Initiate settlements with flash loan specifications
Borrower contracts: Adapt protocol-specific flash loan mechanics
Settlement contract: Executes the final CoW Protocol settlement

Contract Details

Source: src/FlashLoanRouter.sol
License: GPL-3.0-or-later
Solidity: ^0.8.28
Address: 0x9da8B48441583a2b93e2eF8213aAD0EC0b392C69 (all networks)

State Variables

Immutable

Variable	Type	Description
`settlementContract`	`ICowSettlement`	CoW Protocol settlement contract
`settlementAuthentication`	`ICowAuthentication`	Solver authentication contract

Transient Storage

Variable	Type	Description
`pendingBorrower`	`IBorrower`	Current state: READY, borrower address, or SETTLING
`pendingDataHash`	`bytes32`	Hash of remaining loans and settlement data

Functions

flashLoanAndSettle

function flashLoanAndSettle(
    Loan.Data[] calldata loans,
    bytes calldata settlement
) external onlySolver

Main entry point for solvers. Requests all specified flash loans sequentially, then executes the settlement. Parameters:

loans: Array of flash loan specifications (amount, token, lender, borrower)
settlement: ABI-encoded call data for settle() on the CoW Settlement contract

Requirements:

Caller must be a registered solver
No other settlement can be in progress
Settlement data must encode a valid settle() call

Emits: Settlement(address solver)

borrowerCallBack

function borrowerCallBack(bytes memory loansWithSettlement) external onlyPendingBorrower

Called by borrower contracts after receiving flash loan proceeds. Validates data integrity and continues processing. Parameters:

loansWithSettlement: Encoded remaining loans and settlement data (must match stored hash)

Requirements:

Caller must be the expected pending borrower
Data hash must match the stored pendingDataHash

settlementContract (view)

function settlementContract() external view returns (ICowSettlement)

Returns the CoW Protocol settlement contract address.

settlementAuthentication (view)

function settlementAuthentication() external view returns (ICowAuthentication)

Returns the solver authentication contract address.

Events

Settlement

event Settlement(address indexed solver);

Emitted when a solver initiates a flash loan settlement.

Modifiers

onlySolver

Restricts function access to registered CoW Protocol solvers verified through the settlement authenticator.

onlyPendingBorrower

Restricts callback access to the borrower contract that the router is currently expecting a callback from.

Security

Reentrancy prevention: pendingBorrower transient storage prevents concurrent settlements
Data integrity: Hash comparison validates callback data has not been tampered with
Settlement validation: Only the settle() function selector is allowed
Sequential processing: Loans must be processed in the specified order

The router does not validate that flash loan proceeds are available for the settlement. It is the solver’s responsibility to ensure that loan parameters are correct and that the settlement will succeed.

Integration

Solvers integrating with the FlashLoanRouter must:

Be registered in the settlement authenticator
Encode settlement data as a valid settle() call
Specify correct loan parameters (lender, borrower, token, amount)
Ensure settlement logic includes repayment of all borrowed amounts plus fees

Next Steps

AaveBorrower

Aave flash loan adapter

ERC3156Borrower

ERC-3156 flash loan adapter

Contracts

Hooks Trampoline

Composable CoW

Contracts SDK