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

# Isthmus

> Hardfork registry entry for the Isthmus network upgrade, which brought L1's Pectra upgrade to the OP Stack and added the operator fee.

<Info>
  **Normative spec:** the [Isthmus specification](https://specs.optimism.io/protocol/isthmus/overview.html)
  is the canonical definition of this upgrade. This page records activation data
  and operational pointers; it does not restate the spec.
</Info>

Isthmus brought Ethereum's Pectra upgrade to the OP Stack and introduced the
operator fee.

|                                         |                                                                                                                             |
| --------------------------------------- | --------------------------------------------------------------------------------------------------------------------------- |
| Status                                  | Active                                                                                                                      |
| Governing spec                          | [specs.optimism.io](https://specs.optimism.io/protocol/isthmus/overview.html)                                               |
| Governance approval                     | [proposal](https://vote.optimism.io/proposals/8705916809146420472067303211131851783087744913535435360574720946039078686841) |
| Operator notice                         | [Upgrade 15 notice](/notices/archive/upgrade-15)                                                                            |
| Mainnet activation (superchain default) | Fri, 09 May 2025 16:00:01 UTC (`1746806401`)                                                                                |
| Sepolia activation (superchain default) | Thu, 17 Apr 2025 16:00:00 UTC (`1744905600`)                                                                                |

Minimum component versions (from [Upgrade 15 notice](/notices/archive/upgrade-15)):

| Component       | Minimum version |
| --------------- | --------------- |
| `op-node`       | `v1.13.2`       |
| `op-geth`       | `v1.101503.4`   |
| `op-batcher`    | `v1.12.0`       |
| `op-challenger` | `v1.4.0`        |

## What changed

Per the [spec overview](https://specs.optimism.io/protocol/isthmus/overview.html):

* Pectra EIPs on L2, including
  [EIP-7702](https://eips.ethereum.org/EIPS/eip-7702) (set EOA account code),
  [EIP-2537](https://eips.ethereum.org/EIPS/eip-2537) (BLS12-381
  precompiles), [EIP-2935](https://eips.ethereum.org/EIPS/eip-2935)
  (historical block hashes in state), and
  [EIP-7623](https://eips.ethereum.org/EIPS/eip-7623) (increased calldata
  cost). The [EIP-7002](https://eips.ethereum.org/EIPS/eip-7002) and
  [EIP-7251](https://eips.ethereum.org/EIPS/eip-7251) predeploy contracts and
  syscalls are not adopted by the OP Stack.
* `L2ToL1MessagePasser` storage root in the block header.
* [Operator fee](https://specs.optimism.io/protocol/isthmus/exec-engine.html#operator-fee).
* Smart contracts: predeploy, L1 block attributes, and `SystemConfig` updates.

The [Upgrade 15 notice](/notices/archive/upgrade-15) covers the operator steps
that accompanied activation.