Interaction
The interaction module enables CoW Protocol settlements to invoke arbitrary smart contracts, supporting capabilities such as EIP-2612 permit calls for gasless approvals and AMM trades (Uniswap, Balancer, Curve, etc.).
Types
Interaction
Represents a complete smart contract call with three components:
interface Interaction {
target: string; // Contract address to invoke
value: BigNumberish; // Native Ether amount in wei (defaults to 0)
callData: string; // Encoded function data (defaults to "0x")
}
InteractionLike
A flexible partial type requiring only the target address:
interface InteractionLike {
target: string;
value?: BigNumberish;
callData?: string;
}
Functions
normalizeInteraction
Processes a single interaction, applying default values for optional fields.
function normalizeInteraction(interaction: InteractionLike): Interaction;
normalizeInteractions
Handles arrays of interactions.
function normalizeInteractions(interactions: InteractionLike[]): Interaction[];
0 for value and "0x" for callData.
Execution Stages
enum InteractionStage {
PRE = 0, // Setup operations before token transfers
INTRA = 1, // Swaps after sell tokens arrive (default)
POST = 2, // Cleanup after all trading concludes
}
Common Use Cases
import { ethers } from "ethers";
// EIP-2612 permit (PRE stage)
const permitInteraction = {
target: tokenAddress,
value: 0,
callData: tokenContract.interface.encodeFunctionData("permit", [
owner, spender, value, deadline, v, r, s
]),
};
// Uniswap swap (INTRA stage)
const swapInteraction = {
target: uniswapRouterAddress,
value: 0,
callData: router.interface.encodeFunctionData("exactInputSingle", [params]),
};
// WETH unwrap (POST stage)
const unwrapInteraction = {
target: wethAddress,
value: 0,
callData: weth.interface.encodeFunctionData("withdraw", [amount]),
};
Best Practices
- Validate target addresses before constructing interactions
- Use Ethers.js for safe calldata encoding
- Exercise caution with Ether transfers (non-zero
value)
- Test extensively on testnets prior to mainnet use
- Select appropriate stages based on token balance availability
Last modified on March 4, 2026
