> ## 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.

# Karst

> Hardfork registry entry for the Karst network upgrade, which introduced the L2 Contract Manager and Osaka EIPs on L2.

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

Karst (Upgrade 19) introduced the L2 Contract Manager, activated a subset of
Osaka EIPs on L2, promoted `CANNON_KONA` to the respected game type, and
reduced the `bn256Pairing` precompile input limit as a preemptive Glamsterdam
defense. `op-geth` and `op-program` do not support Karst — see the
[end-of-support notice](/notices/op-geth-deprecation).

|                                         |                                                                             |
| --------------------------------------- | --------------------------------------------------------------------------- |
| Status                                  | Active                                                                      |
| Governing spec                          | [specs.optimism.io](https://specs.optimism.io/protocol/karst/overview.html) |
| Operator notice                         | [Upgrade 19 notice](/notices/upgrade-19)                                    |
| Mainnet activation (superchain default) | Wed, 08 Jul 2026 16:00:01 UTC (`1783526401`)                                |
| Sepolia activation (superchain default) | Wed, 17 Jun 2026 16:00:01 UTC (`1781712001`)                                |

Minimum component versions (from [Upgrade 19 notice](/notices/upgrade-19)):

| Component        | Minimum version |
| ---------------- | --------------- |
| `op-node`        | `v1.19.1`       |
| `op-reth`        | `v2.3.3`        |
| `op-challenger`  | `v1.9.3`        |
| `op-dispute-mon` | `v1.5.2`        |
| `op-contracts`   | `v7.0.0`        |

## What changed

Per the [spec overview](https://specs.optimism.io/protocol/karst/overview.html)
and the [Upgrade 19 notice](/notices/upgrade-19):

* [L2 Contract Manager (L2CM)](/op-stack/features/l2-contract-manager):
  governance-approved L2 predeploy upgrades through a consensus-layer
  mechanism.
* Osaka EIPs on L2, including
  [EIP-7825](https://eips.ethereum.org/EIPS/eip-7825) (transaction gas limit
  cap, not applied to deposits),
  [EIP-7823](https://eips.ethereum.org/EIPS/eip-7823) and
  [EIP-7883](https://eips.ethereum.org/EIPS/eip-7883) (MODEXP bounds and gas),
  [EIP-7910](https://eips.ethereum.org/EIPS/eip-7910) (`eth_config`),
  [EIP-7939](https://eips.ethereum.org/EIPS/eip-7939) (CLZ opcode), and
  [EIP-7951](https://eips.ethereum.org/EIPS/eip-7951) (secp256r1 gas cost
  alignment).
* Reduced the `bn256Pairing` precompile maximum input size from 427 to 300
  pairs (Glamsterdam defense).
* Promoted `CANNON_KONA` (game type 8) to the respected game type, making
  `kona-client` the primary fault proof program used for withdrawals.
* Consensus layer: network upgrade transactions applied during derivation.