We're pleased to announce the upcoming Upgrade 15 for Metal L2, the Isthmus Hard Fork. This upgrade introduces significant enhancements including the implementation of Prague features on the OP Stack, designed to align closely with Ethereum's forthcoming Pectra upgrade. This alignment ensures Metal L2 continues to benefit from the latest Ethereum improvements.

The Isthmus hard fork for the Sepolia Superchain will be activated at Thu Apr 17 16:00:00 UTC 2025 (1744905600) and the Mainnet Superchain will be activated at Fri May 9 2025 16:00:01 UTC (1746806401). This is for all chains who have opted into the hard fork inheritance behavior. Note: These are timestamps not blockheight.

Upgrade 15 also includes the addition of the L2 Withdrawals Root in the Block Header, streamlining the security process for chain operators. By enabling operators to more easily run full nodes for dispute monitoring, this change significantly boosts the overall security and scalability of fault proofs across the Superchain.

Lastly, Upgrade 15 introduces a new Operator Fee structure, enhancing the accuracy and flexibility of fee calculations on the OP Stack. This development is essential for future support of chains employing Alt-DA and ZK proving technologies. Activation of Upgrade 15 on Metal L2 Mainnet will follow the successful deployment of Ethereum's Pectra upgrade, with an exact date yet to be announced. For detailed instructions and further information, visit the full upgrade page on Optimism.