OP Labs has scheduled Upgrade 19 - Karst Hard Fork (detailed changes), and Conduit will be rolling it out to Zircuit Testnet, along with the L1 contracts upgrade to op-contracts/v7.0.0.

This is both a hard fork (consensus-breaking, every node must be updated before activation) and an L1 contracts upgrade. Unlike our recent contracts-only upgrades, this one includes EVM changes that are relevant to app and smart contract developers on your chain, so please read step 2 below even if you don't run your own nodes.

Activation Timeline: Tue Sep 08 2026 16:00:01 GMT+0000 (1788883201)

Use the timestamp for your chain wherever a Karst activation time is required below.

Required Actions

• If you or your partners are running external nodes, please ensure the following steps are completed before the fork time:

  • Update op-node to version: v1.19.3 (Release) with flag :--override.karst=1788883201.

  • Update op-reth to version: v2.1.2 (Release). op-geth has reached end of support, so you must be running op-reth.

  • Use updated genesis.json files from here: https://api.conduit.xyz/file/v1/optimism/genesis/zircuit-garfield-testnet

  • Conduit has updated our external node setup guide to reflect these changes -- you can use it as a reference for spinning up your node. Please reach out if you require a latest op-reth snapshot.

• This upgrade includes various EIPs that affect gas pricing and might be relevant for application developers on your chain. Full details here.

• After your chain's upgrade completes, we will republish contracts.json with updated addresses in a new format, aligned with op-contracts/v7.0.0 and OPCMv2.

  • The file currently published for your chain may still contain addresses that are outdated as of the v5.0.0 contract upgrades. If you are relying on that copy today, treat those addresses as potentially stale.

  • If you have contract addresses hardcoded, or tooling that reads or parses contracts.json, plan to re-download the file after your chain's activation and update both the stored addresses and any parsing logic that assumes the old structure.

  • If you depend on specific contract addresses and want us to confirm what is changing for your chain ahead of time, let us know and we'll flag them.

Questions?
If you have any questions, reach out through your usual support channels or at support@conduit.xyz.