> ## Documentation Index
> Fetch the complete documentation index at: https://docs.celo.org/llms.txt
> Use this file to discover all available pages before exploring further.

# L2 Isthmus Hardfork

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

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

  * Baklava testnet activation was executed at timestamp `1749654000` ([block 37881140](https://celo-baklava.blockscout.com/block/0xec4a86ed28d74090b71cb59c34e4b31b8a49ef00b09880d67034dc56237e4b1d)) on Wed, Jun 11, 2025, 15:00:00 UTC.
  * Alfajores testnet activation was executed at timestamp `1750863600` ([block 49908280](https://celo-alfajores.blockscout.com/block/0x643b5ce0b59b83ffd8a9b9cfc13a91eeb1228094e0dbb3e1927ec2afc28dfbcb)) on Wed, Jun 25, 2025, 15:00:00 UTC.
  * **Mainnet** activation was executed at timestamp **`1752073200`** ([block 40172442](https://celo.blockscout.com/block/0xdef57aaf634a3de07e7763db9b21d5e192e784316b8c233a2a4cd1eea6bf4f41)) on Wed, Jul 9, 2025, 15:00:00 UTC.
</Note>

<Warning>
  If you're encountering a stuck node after Alfajores hardfork block (49908280), see the [FAQ](/legacy/faq#my-alfajores-node-stalled-at-the-isthmus-hardfork-block-49908280).
</Warning>

## 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](https://gov.optimism.io/t/proposal-preview-implement-prague-features-on-the-op-stack/9703).

  Notable EIP's included:

  * [EIP-7702](https://github.com/ethereum/EIPs/blob/f27ddf2b0af7e862a967ee38ceeaa7d980786ca1/EIPS/eip-7702.md): Set code transaction
  * [EIP-2537](https://github.com/ethereum/EIPs/blob/f27ddf2b0af7e862a967ee38ceeaa7d980786ca1/EIPS/eip-2537.md): BLS12-381 precompiles
  * [EIP-2935](https://github.com/ethereum/EIPs/blob/f27ddf2b0af7e862a967ee38ceeaa7d980786ca1/EIPS/eip-2935.md): Block hashes contract predeploy
  * [EIP-7623](https://github.com/ethereum/EIPs/blob/f27ddf2b0af7e862a967ee38ceeaa7d980786ca1/EIPS/eip-7623.md): Increase calldata cost

* **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](https://gov.optimism.io/t/proposal-preview-l2-withdrawals-root-in-block-header/9730).

For more information on the Isthmus implementation details, please review [OP's Isthmus specification](https://specs.optimism.io/protocol/isthmus/overview.html).

Isthmus additionally enables the [Holocene hardfork](https://docs.optimism.io/notices/holocene-changes) 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](https://specs.optimism.io/protocol/holocene/overview.html).

## For node operators

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

### Update to the latest release

The release contains the activation timestamps for Celo Mainnet, Baklava and Alfajores.

* `op-geth` at [v2.1.0](https://github.com/celo-org/op-geth/releases/tag/celo-v2.1.0)
* `op-node` at [v2.1.0](https://github.com/celo-org/optimism/releases/tag/celo-v2.1.0)

#### 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](https://github.com/Layr-Labs/eigenda/tree/master/api/proxy) to version [v1.8.2](https://github.com/Layr-Labs/eigenda/pkgs/container/eigenda-proxy/437919973?tag=v1.8.2).

### 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