The Hardfork combinator is a remarkable piece of technology, which plays a central role in the deployment of Cardano Shelley, created to allow the orderly transition from Byron to Cardano Shelley. In this technical video, Philipp Kant will walk you through the whole process, so you can see for yourself how everything works. This is a whistle-stop tour - in reality, this process will take considerably longer but Philipp has condensed some of the steps here. The combinator has been designed to actually avoid an actual hard fork, as you might know them from other blockchain systems. In those cases, disagreement between the different entities running nodes on the network can lead to the system diverging, and creating different versions of the protocol that evolve separately and independently of one another. The hard fork combinator gives us the capability for a node to speak multiple protocols (though only one at once!). While running the first protocol (i.e. Byron), it can be triggered by a special on-chain update whereupon it manages the smooth transition to running the next protocol (i.e. Shelley). This code has now been successfully tested against a number of mainnet candidates in ‘dry runs’ and is now ready for deployment on the Byron mainnet.
Hard Fork Combinator: full tech demo