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L2 Isthmus Hardfork

This page outlines breaking changes related to the Isthmus network upgrade for node operators.

info

This page will be kept updated with key information about the hardfork.

  • Baklava testnet activation is tentatively planned at timestamp 1749654000 on Wed, Jun 11, 2025, 15:00:00 UTC.
  • Alfajores testnet activation is tentatively planned at timestamp 1750863600 on Wed, Jun 25, 2025, 15:00:00 UTC.
  • Mainnet activation is planned at timestamp 1752073200 on Wed, Jul 9, 2025, 15:00:00 UTC.

What's included in Isthmus​

Isthmus contains these main changes:

  • Implement Prague features on the OP Stack: This includes the EIPs that are relevant to the L2 that are being added to Ethereum with its Pectra activation. Learn more about this here.

    Notable EIP's included:

  • L2 Withdrawals Root in Block Header: This lowers the lift for chain operators by allowing them to run a full node to operate op-dispute-mon, making it easier to guarantee the security of the fault proofs for the chains in the Superchain as the number of chains scales. Learn more about this here.

For more information on the Isthmus implementation details, please review OP's Isthmus specification.

Isthmus additionally enables the Holocene hardfork with the following changes:

  • Holocene block derivation: A set of changes that render the derivation pipeline stricter and simpler, improving worst-case scenarios for the Fault Proof System and Interoperability.
  • EIP-1559 configurability: The elasticity and denominator EIP-1559 parameters become configurable via the SystemConfig L1 contract, allowing the gas target and gas limit to be configured independently.

For more information on the Holocene details, please review OP's Holocene specification.

For node operators​

Node operators will need to upgrade to the respective Isthmus releases before the activation dates.

Update to the latest release​

The releases contain the activation timestamps for Baklava and Alfajores.

Updating the EigenDA proxy​

The Isthmus hardfork also prepares the Celo networks for the EigenDA v2 update.

This means that operators need to make sure to upgrade the EigenDA proxy to version v1.8.1.

Verify Your Configuration​

Make the following checks to verify that your node is properly configured.

  • op-node and op-geth will log their configurations at startup
  • Check that the Isthmus time is set to activation-timestamp in the op-node startup logs
  • Check that the Isthmus time is set to activation-timestamp in the op-geth startup logs