Bitcoin Core

It's already possible now you include a flag in a transaction where you basically tell the network, look, I might want to replace this later. So if you have a direct connection to a miner, then that miner can do whatever it wants because this is not a consensus rule. How do you switch it on? You put a setting in your config file called mempoolfulrbf. And there are very different aspects of this feature and also of this discussion, which we'll get to.