> ## 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.

# GPv2Settlement

> The main settlement contract for executing CoW Protocol batch trades

# GPv2Settlement Contract

The `GPv2Settlement` contract serves as CoW Protocol's core infrastructure, inheriting from `GPv2Signing`, `ReentrancyGuard`, and `StorageAccessible` to enable batch settlements and order validation.

**Source:** `src/contracts/GPv2Settlement.sol`
**License:** LGPL-3.0-or-later
**Solidity:** `>=0.7.6 <0.9.0`

## State Variables

### Immutable

| Variable        | Type                 | Description                                   |
| --------------- | -------------------- | --------------------------------------------- |
| `authenticator` | `GPv2Authentication` | Determines solver authorization               |
| `vault`         | `IVault`             | Balancer Vault for fund management            |
| `vaultRelayer`  | `GPv2VaultRelayer`   | Enables vault interactions on behalf of users |

### Storage

| Variable       | Type                        | Description                                           |
| -------------- | --------------------------- | ----------------------------------------------------- |
| `filledAmount` | `mapping(bytes => uint256)` | Tracks per-order fill amounts to prevent over-filling |

## Primary Functions

### settle()

Executes batch orders at uniform clearing prices with pre/intra/post-settlement interactions.

```solidity theme={null}
function settle(
    IERC20[] calldata tokens,
    uint256[] calldata clearingPrices,
    GPv2Trade.Data[] calldata trades,
    GPv2Interaction.Data[][3] calldata interactions
) external nonReentrant onlySolver;
```

### swap()

Matches orders directly against Balancer V2 pools for optimized single-pool trades.

```solidity theme={null}
function swap(
    IVault.SingleSwap calldata swap,
    GPv2Trade.Data calldata trade
) external nonReentrant onlySolver returns (int256);
```

### invalidateOrder()

Allows order owners to revoke on-chain orders by invalidating the order UID.

```solidity theme={null}
function invalidateOrder(bytes calldata orderUid) external;
```

### Storage Cleanup

Gas refund functions for expired orders:

```solidity theme={null}
function freeFilledAmountStorage(bytes[] calldata orderUids) external;
function freePreSignatureStorage(bytes[] calldata orderUids) external;
```

## Settlement Execution Flow

```mermaid theme={null}
sequenceDiagram
    participant Solver
    participant Settlement
    participant VaultRelayer
    participant Vault

    Solver->>Settlement: settle(tokens, prices, trades, interactions)
    Settlement->>Settlement: Execute pre-settlement interactions
    Settlement->>Settlement: Validate trades and signatures
    Settlement->>VaultRelayer: transferFromAccounts (pull sell tokens)
    Settlement->>Settlement: Execute intra-settlement interactions
    Settlement->>Vault: Transfer tokens to recipients
    Settlement->>Settlement: Execute post-settlement interactions
```

## Security Protections

* All orders include a `validTo` timestamp checked on execution
* Filled amount tracking prevents over-filling
* Limit price validation ensures trades respect order parameters
* Solver authorization restricts settlement access via `onlySolver` modifier
* `nonReentrant` modifier prevents reentrancy attacks