feat: implement CoW Protocol paymaster for stablecoin gas payments #116
Description
What problem does this solve?
Users need native tokens (ETH, MATIC, etc.) to pay for gas, even if they only hold stablecoins. This creates friction and forces users to maintain gas token balances across multiple chains.
Describe the solution
Implement a paymaster feature that allows users to pay for gas using stablecoins on any network where CoW Protocol is available. The paymaster would handle the stablecoin-to-gas-token swap via CoW Protocol, allowing seamless transactions without requiring users to hold native tokens.
Alternatives considered
- Traditional fiat on-ramps for gas (expensive, slow, requires KYC)
- DEX swaps before every transaction (poor UX, two transactions needed)
- Centralized paymaster services (introduces counterparty risk, fees)
- ERC-4337 paymasters without CoW (may get worse swap rates)
Implementation notes
- Integrate CoW Protocol SDK for stablecoin swaps
- Implement ERC-4337 paymaster contract that accepts stablecoins
- Calculate gas cost + swap slippage to determine required stablecoin amount
- Support common stablecoins (USDC, USDT, DAI) on each network
- Handle cases where CoW Protocol isn't available (fallback or reject)
- Add user preference for which stablecoin to use for gas
- Consider MEV protection via CoW's batch auction mechanism
- Deploy paymaster contracts on networks with CoW Protocol