This proposal outlines the features to be introduced with the Isthmus hard fork. These are key to maintaining parity with L1 and provide the best experience to users and developers of the Superchain that we can. This proposal introduces the Isthmus hard fork. The features to be activated are:

• L2 Withdrawals Root in Block Header
• Operator Fee
• Implement Prague features in Isthmus

Blockspace Charter

• This upgrade does not require any changes to the Standard Rollup Charter beyond those in Upgrade #14, which this builds upon.

This proposal is eligible for Voting Cycle #35: https://gov.optimism.io/t/voting-cycle-roundup-35/9771

If passed in the Token House, it will proceed to a veto period in the Citizens’ House.