Ethereum Foundation researchers, including Vitalik Buterin, have outlined a roughly seven-fork path to Lean Ethereum by the end of 2029. The plan describes Lean Ethereum as the protocol's third major version and is designed to preserve backward compatibility, allowing existing applications to continue operating without being rebuilt from scratch. H* is planned as the final fork without Lean features, followed by upgrades through I* and J* toward completion at L*. I* would introduce leanVM and Lean transactions, while J* is slated to add Lean attestations, data availability sampling and PCS. Ethereum's first major version was its original launch, and the second followed the 2022 Merge, which changed how the network reaches consensus.