Lean Ethereum is usually described as a destination: a tech-debt reset, post-quantum cryptography, and a ZK-proven state transition function. Much less has been said about how the network gets there from where it is today, and the path is not a single hard fork. It is two roads that have to meet: incremental changes on mainnet, and a greenfield lean stack currently being hardened in post-quantum devnets. Each has prerequisites the other does not control.