This is the contracts release for [Upgrade 18](https://gov.optimism.io/t/upgrade-18-custom-gas-token-v2-and-kona-proofs/10576). The main changes in this release are:
- Custom Gas Token v2: gated behind the CUSTOM_GAS_TOKEN feature flag in SystemConfig and is intended for new chains that enable it at deployment.
- Creator Pattern Dispute Game Refactor: efficient deployment of dispute game contracts, allowing one single implementation to be used for all chains (which is then cloned and configured separately for each chain).
- Cannon + Kona: This upgrade adds a [new game type]() to use [Kona Proof](https://github.com/ethereum-optimism/optimism/tree/develop/kona/crates/proof/proof) with the Cannon [Fault Proof VM](https://specs.optimism.io/fault-proof/index.html#fault-proof-vm). It does not change the respected game type.
optimism/packages/contracts-bedrock/src/dispute/lib/Types.sol
Lines 76 to 77 in b9dc580
The audit results [are published here](https://github.com/ethereum-optimism/optimism/blob/develop/docs/security-reviews/2026_01-U18-Cantina.pdf).
Also included in this release are changes to L2 contracts which have not yet been approved by governance, and are not currently planned for activation on any Optimism Governed chains.
These changes would enable a revenue sharing scheme, in which fees earned on L2 could be divided between multiple parties based on predefined values. This functionality is disabled by default.