@pomstan @chjara you can use indirection. Your main contract calls a function on another contract to do the actual work. The main contract has a mutable pointer to the other contract. Basically we've reached a point where you can decide the level of immutability you want in a smart contract. You can easily make a contract that has parts you can change and other parts you cannot. it can be verified by reading the contract code. So far AFAIK nobody's ever found a hack that cheats a correctly written contract