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Upgrade 18 (approved by Optimism Governance) introduced CANNON_KONA (8) as an available game type alongside CANNON (0). Upgrade 19 promotes CANNON_KONA to the respected game type for chains managed by the Optimism Security Council — meaning it is applied automatically as part of the onchain upgrade. Non-managed chains that want to switch must follow this guide.

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Overview

Kona proofs use the kona-client fault proof program, which is a combination of kona-node and op-reth. This runs alongside the existing op-program (a combination of op-node and op-geth). Both programs:
  • Use Cannon as the FPVM, and
  • Are used by the same dispute game implementation (FaultDisputeGame.sol).
After the cannon+kona upgrade is deployed, both game types are available:
  • CANNON (0) — op-program
  • CANNON_KONA (8) — kona-client
By default, the respected game type remains CANNON (0), meaning only those games are used for withdrawals. This guide explains how to switch your chain so that Kona proofs (CANNON_KONA, 8) become the respected game type.
This guide assumes you have already completed the cannon+kona upgrade, including setting both cannonPrestate and cannonKonaPrestate in OpChainConfig, and that your fault proof infrastructure is healthy.
The high-level flow is:
  • Verify that cannon+kona support is correctly deployed on-chain.
  • Confirm that your off-chain infra (especially op-challenger) is Kona-ready.
  • Switch the respected game type to CANNON_KONA (8).
  • Update op-proposer to post Kona games.
  • Monitor the system.

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How to Switch to Kona Proofs

1

Confirm cannon+kona support is deployed

Before changing the respected game type, verify that your chain has been upgraded to support both CANNON and CANNON_KONA games.
The required upgrade is performed via OPCM.upgrade with an OpChainConfig that sets both cannonPrestate and cannonKonaPrestate.
  1. Check OpChainConfig prestates Ensure that the OpChainConfig used in your most recent upgrade included:
    • cannonPrestate pointing to a valid cannon64 prestate.
    • cannonKonaPrestate pointing to a valid cannon64-kona prestate.
    Both hashes must come from the standard prestates in the superchain registry and must embed an up-to-date chain config for your chain.
  2. Verify DisputeGameFactory implementations After the cannon+kona upgrade, the DisputeGameFactory should have:
    • A non-zero implementation for CANNON (0), and
    • A non-zero implementation for CANNON_KONA (8).
    Example (using cast):
    cast
    Both calls should return non-zero addresses.
2

Ensure op-challenger is Kona-ready

Your challengers must be able to play both cannon and kona games before you change the respected game type.
  1. Trace types If you explicitly configure trace types, ensure that cannon-kona is included. A typical setting is:
  2. Prestate URLs Make sure op-challenger can fetch both cannon and cannon-kona prestates:
    • If they are at the same URL, use:
    • If they are at different locations, use:
  3. Kona host binary For operators not using the standard OP Labs op-challenger Docker images, you must also provide:
    The kona-host binary is available from the Kona repository (for example under bin/host). Build it from the same release as the cannon-kona prestate you configured.
3

Switch the respected game type to CANNON_KONA

Once both on-chain and off-chain pieces are ready, you can switch the respected game type so that Kona proofs become the canonical path for withdrawals.
Changing the respected game type affects which games can be used to prove withdrawals. Only perform this step once you are confident in your Kona setup.
The respected game type is configured in the AnchorStateRegistry contract.
  1. Encode the calldata Use cast calldata to encode a call to setRespectedGameType(uint32) with game type 8 (which corresponds to CANNON_KONA):
    cast
  2. Send the transaction Send the transaction from the Guardian to the AnchorStateRegistry:
    cast
  3. Verify the new respected game type After the transaction confirms, verify that the respected game type is now 8:
    cast
    The returned value should be 8, indicating that CANNON_KONA is now the respected game type.
4

Update op-proposer to use game type 8

With CANNON_KONA set as the respected game type, your proposers must create Kona games.
  1. Update the proposer game type Change your op-proposer configuration from game type 0 to 8:
    This change is not required as part of the initial cannon+kona upgrade; it is only required when you actually switch the respected game type to CANNON_KONA.
  2. Restart proposers Restart your proposer processes so they pick up the new configuration. Verify in logs and metrics that they are now using game type 8.
5

Monitor, and validate

After switching to Kona proofs, closely monitor your chain to ensure everything is functioning as expected.
  1. Run test withdrawals
    • Perform a few small test withdrawals and ensure that:
      • New fault dispute games are created with game type CANNON_KONA (8).
      • Your challengers are responding correctly using kona-host.
  2. Observe metrics and logs
    • Monitor op-proposer and op-challenger logs for errors.
    • Watch dispute game metrics (for example, game counts and step timings) for anomalies.

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References