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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 generates the calldata for you. For the concept overview, see Universal Router Concepts.

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Key Functions

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execute

Executes a sequence of commands in order. 
function execute(
    bytes calldata commands,
    bytes[] calldata inputs,
    uint256 deadline
) external payable;
ParameterTypeDescription
commandsbytesSequence of command codes (1 byte each)
inputsbytes[]ABI-encoded parameters for each command
deadlineuint256Unix timestamp after which the transaction reverts
You typically do not call execute() directly. Use the Swap API to generate the { to, data, value } object, then send it as a transaction.

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Command Types

CommandCodeDescription
V2_SWAP_EXACT_IN0x00V2 swap with exact input amount
V2_SWAP_EXACT_OUT0x01V2 swap with exact output amount
V3_SWAP_EXACT_IN0x02V3 swap with exact input amount
V3_SWAP_EXACT_OUT0x03V3 swap with exact output amount
WRAP_ETH0x0bWrap native KAS to WKAS
UNWRAP_WETH0x0cUnwrap WKAS to native KAS
PERMIT2_PERMIT0x0aExecute a Permit2 signature-based permit
TRANSFER0x04Transfer tokens

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Usage Pattern

The recommended pattern is to use the Swap API to generate calldata: 
// 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)
});

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Error Handling

Common revert reasons:
ErrorCauseSolution
EXPIREDTransaction deadline exceededUse a longer deadline or submit faster
V3_INVALID_AMOUNT_OUTOutput below minAmountOutIncrease slippage tolerance
TRANSFER_FROM_FAILEDInsufficient approval or balanceCheck Permit2 approval and token balance
INSUFFICIENT_ETHNot enough native KAS sentEnsure value matches the required amount

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ABI

[
  "function execute(bytes calldata commands, bytes[] calldata inputs, uint256 deadline) external payable"
]