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

# Universal Router

> Unified swap execution contract ABI and usage

# Universal Router Contract

The Universal Router executes swaps across V2 and V3 pools via an encoded command interface. In practice, you do not need to encode commands yourself — the [Swap API](/api/swap) generates the calldata for you.

For the concept overview, see [Universal Router Concepts](/concepts/universal-router).

## Key Functions

### execute

Executes a sequence of commands in order.

```solidity theme={null}
function execute(
    bytes calldata commands,
    bytes[] calldata inputs,
    uint256 deadline
) external payable;
```

| Parameter  | Type      | Description                                        |
| ---------- | --------- | -------------------------------------------------- |
| `commands` | `bytes`   | Sequence of command codes (1 byte each)            |
| `inputs`   | `bytes[]` | ABI-encoded parameters for each command            |
| `deadline` | `uint256` | Unix timestamp after which the transaction reverts |

<Warning>
  You typically do not call `execute()` directly. Use the [Swap API](/api/swap) to generate the `{ to, data, value }` object, then send it as a transaction.
</Warning>

## Command Types

| Command             | Code   | Description                              |
| ------------------- | ------ | ---------------------------------------- |
| `V2_SWAP_EXACT_IN`  | `0x00` | V2 swap with exact input amount          |
| `V2_SWAP_EXACT_OUT` | `0x01` | V2 swap with exact output amount         |
| `V3_SWAP_EXACT_IN`  | `0x02` | V3 swap with exact input amount          |
| `V3_SWAP_EXACT_OUT` | `0x03` | V3 swap with exact output amount         |
| `WRAP_ETH`          | `0x0b` | Wrap native KAS to WKAS                  |
| `UNWRAP_WETH`       | `0x0c` | Unwrap WKAS to native KAS                |
| `PERMIT2_PERMIT`    | `0x0a` | Execute a Permit2 signature-based permit |
| `TRANSFER`          | `0x04` | Transfer tokens                          |

## Usage Pattern

The recommended pattern is to use the Swap API to generate calldata:

```typescript theme={null}
// 1. Get calldata from Swap API
const response = await fetch('/swap-api/api/v1/swap', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({
    tokenIn: '0x...',
    tokenOut: '0x...',
    amountIn: '1000000000000000000',
    tradeType: 0,
    slippage: 0.5,
    recipient: userAddress,
    deadline: 1200
  })
});

const swapData = await response.json();

// 2. Send the transaction directly
const tx = await signer.sendTransaction({
  to: swapData.to,      // Universal Router address
  data: swapData.data,  // Encoded execute() calldata
  value: swapData.value // Native KAS value (0 for ERC-20 swaps)
});
```

## Error Handling

Common revert reasons:

| Error                   | Cause                            | Solution                                   |
| ----------------------- | -------------------------------- | ------------------------------------------ |
| `EXPIRED`               | Transaction deadline exceeded    | Use a longer deadline or submit faster     |
| `V3_INVALID_AMOUNT_OUT` | Output below `minAmountOut`      | Increase slippage tolerance                |
| `TRANSFER_FROM_FAILED`  | Insufficient approval or balance | Check Permit2 approval and token balance   |
| `INSUFFICIENT_ETH`      | Not enough native KAS sent       | Ensure `value` matches the required amount |

## ABI

```json theme={null}
[
  "function execute(bytes calldata commands, bytes[] calldata inputs, uint256 deadline) external payable"
]
```