Paymaster

In ERC-4337 account abstraction, a contract that pays the gas for a user operation — either sponsoring it (making a transaction feel free, an app-funded subsidy) or letting the user pay fees in an ERC-20 token instead of the native coin (with a spread). Works alongside bundlers (which relay user operations to the EntryPoint). Paymasters are what enable gasless and pay-in-stablecoin UX.