# Aggregator Router API

The Aggregator Router executes single-pool swaps for contract callers such as aggregators, solvers, and smart wallets. It is the prepaid counterpart to the Balancer Router: instead of pulling the input token through Permit2, the caller transfers the input token to the Vault before invoking the swap, and the router settles that payment. There are no token approvals and no Permit2 signatures, and the swap functions do not take a wethIsEth flag or accept ETH. See Token Approvals for how the prepaid and Permit2 models compare.

# State-changing functions

# swapSingleTokenExactIn

function swapSingleTokenExactIn(
    address pool,
    IERC20 tokenIn,
    IERC20 tokenOut,
    uint256 exactAmountIn,
    uint256 minAmountOut,
    uint256 deadline,
    bytes calldata userData
) external returns (uint256 amountOut);

Swaps an exact amount of tokenIn for tokenOut through a single pool. The caller must have transferred exactAmountIn of tokenIn to the Vault before this call.

Parameters:

Returns:

# swapSingleTokenExactOut

function swapSingleTokenExactOut(
    address pool,
    IERC20 tokenIn,
    IERC20 tokenOut,
    uint256 exactAmountOut,
    uint256 maxAmountIn,
    uint256 deadline,
    bytes calldata userData
) external returns (uint256 amountIn);

Swaps tokenIn for an exact amount of tokenOut through a single pool. The caller funds the Vault with tokenIn up to maxAmountIn before this call.

Parameters:

Returns:

# Queries

Query functions simulate a swap against current on-chain state without executing it or moving any tokens, so they require no prepayment and no approvals.

# querySwapSingleTokenExactIn

function querySwapSingleTokenExactIn(
    address pool,
    IERC20 tokenIn,
    IERC20 tokenOut,
    uint256 exactAmountIn,
    address sender,
    bytes calldata userData
) external returns (uint256 amountOut);

Simulates swapSingleTokenExactIn and returns the calculated output amount.

Parameters:

Returns:

# querySwapSingleTokenExactOut

function querySwapSingleTokenExactOut(
    address pool,
    IERC20 tokenIn,
    IERC20 tokenOut,
    uint256 exactAmountOut,
    address sender,
    bytes calldata userData
) external returns (uint256 amountIn);

Simulates swapSingleTokenExactOut and returns the calculated input amount.

Parameters:

Returns: