Proposal Type: Protocol Upgrade
Hi I’m Paul, an Engineering Manager at OP Labs and core contributor of the OP Stack. I reviewed this proposal in collaboration with Sanjana Mehta from the OP Labs Team.
The following proposal has received preliminary review from the Developer Advisory Board. Neither OP Labs, I, nor any other entity mentioned represent or speak on behalf of the Optimism Foundation.
Executive Summary
At its core, U18 delivers three new advancements to the OP Stack:
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Custom Gas Token v2 (CGT v2):
A redesigned implementation that allows OP Stack chains to use any asset - not just ETH - as their native gas token. This unlocks economic alignment for diverse ecosystems, from stablecoin-based rollups offering predictable fees to governance-token-driven networks. CGT v2 emphasizes flexibility, minimal protocol footprint, and forward compatibility by decoupling native asset logic from the bridging layer.
Note: Custom Gas Token v2 is a new implementation that is not compatible with legacy CGT chains. There is currently no migration path from legacy CGT to CGT v2.
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Creator Pattern Dispute Game Refactor:
Simplifies chain deployment by introducing clone-with-immutable-arguments (CWIA) for dispute game contracts. This change removes the need for chain-specific deployments, reducing operational overhead while preserving safety and upgradeability across chains, and reducing gas costs to ensure all operations stay below the EIP-7825 transaction gas limit cap.
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Cannon + Kona:
Adds a second, Rust-based fault proof implementation - Kona - to operate alongside Cannon, increasing redundancy and diversity in the fault proof layer. The new game type, CANNON_KONA, is registered but not yet set as the canonical proof type, ensuring a safe rollout path as the ecosystem transitions toward full permissionless fault proofs.
Motivation
Upgrade 18 advances the OP Stack’s technical foundation by expanding flexibility in fee token configuration, improving deployment efficiency, and strengthening the fault proof layer.
Custom Gas Token v2 allows OP Stack chains to designate a token other than ETH as their native gas asset, enabling greater alignment between fee markets and chain economics. The dispute game refactor standardizes deployment and reduces operational complexity, and Kona proofs introduces a second proof implementation, increasing diversity and redundancy in the fault-proof layer for chains operating permissionless fault proofs.
Specifications
Blockspace Charter
This Protocol Upgrade is scoped to the Standard Rollup Charter. These changes will be made to the charter as a part of this upgrade, and the new prestates have been added to standard prestates TOML in accordance to the existing Standard Rollup Charter.
Technical details
Custom Gas Token
Creator Pattern Dispute Game Refactor
Cannon + Kona
- Kona Proof is a rust-based Fault Proof Program for the OP Stack
Contract changes
The contracts changes included in this upgrade are mostly implementing the three features described above, but the exact version is visible at the op-contracts/v6.0.0-rc.2 tag, which will be finalized as op-contracts/v6.0.0 after this upgrade is approved by governance. A full diff from the previous upgrade can be seen here.
After the veto period has ended, we will ask the Security Council to sign transactions to update the contracts using OP Contracts Manager, and to establish a new absolute prestate hash for chains using permisionless fault proofs. These transactions must to be executed before the actual activation to avoid a broken Fault Proofs system after the activation.
Absolute Prestate
This upgrade includes the absolute prestate for both op-program and kona-proof:
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op-program v1.9.0-rc.1: The absolute prestate hash (cannon64 variant) is
0x033c000916b4a88cfffeceddd6cf0f4be3897a89195941e5a7c3f8209b4dbb6e. It has been publicly verified here. -
Kona (kona-host and kona-client) v1.2.7: The absolute prestate hash (cannon64-kona variant) is
0x0323914d3050e80c3d09da528be54794fde60cd26849cd3410dde0da7cd7d4fa. It has been publicly verified here.
Calldata
The expected calldata to sign on OP Mainnet is below. This also includes the upgrade on Ink, Metal, Mode, Zora, Arena-Z, Swell Mainnets as these networks will be upgraded in one superchain-ops task alongside OP Mainnet.
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
To generate the above calldata:
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Clone the superchain-ops repository, and use the main branch
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cd src/tasks/eth/040-U18-op-ink-mmz-arena-swell
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Run the below command either as council or foundation:
just simulate-stack eth 040-U18-op-ink-mmz-arena-swell <council|foundation>
The terminal output will include the calldata and state changes.
The tasks use the OPCMUpgradeV600 template, refer to it to see how the calldata is generated: https://github.com/ethereum-optimism/superchain-ops/blob/main/src/template/OPCMUpgradeV600.sol
There are several other chains which will be upgraded, in bundles, in additional transactions outlined below. The calldata can be verified in the same way as above (in the superchain-ops repository).
Soneium Mainnet
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
Unichain Mainnet
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
Base Mainnet
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
This can be verified here: https://github.com/base/contract-deployments/tree/main/mainnet/2026-01-09-op-stack-upgrade-18
Impact summary
Custom Gas Token v2 (CGT v2)
This feature does not impact the usage, security, or trust assumptions of standard chains that use ETH as the gas token, since CGT v2 is gated behind the CUSTOM_GAS_TOKEN feature flag in SystemConfig and is intended for new chains that enable it at deployment. This allows us to maintain version alignment across L1 contracts, with the feature remaining disabled as part of this upgrade. Likewise, the CGT-specific predeploy contracts are not deployed in this upgrade.
Creator Pattern Dispute Game Refactor
This has no impact on the usage or security of dispute game contracts. It changes how they are deployed, allowing one single implementation to be used for all chains (which is then cloned and configured separately for each chain). This is more efficient and allows deployments for multiple chains to avoid going over the new maximum transaction size that was introduced in the Ethereum Fusaka hard fork.
Cannon + Kona
This upgrade adds a new game type to use Kona Proof with the Cannon Fault Proof VM. It does not change the respected game type. Chain operators may change the respected game type to CANNON_KONA in order to use Kona Proof instead of op-program.
Action Plan
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Alphanet and Betanet testing has been completed.
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Mainnet upgrade will be executed after Feb 5, 2026.
Security Considerations
We performed an Audit as well as extensive end-to-end testing, including on devnets and testnets. The audit results are published here. We have done extensive threat modelling for the new features in this release.
Precommitment impact review
This Upgrade Proposal does not impact any of the precommitments in the Standard Rollup Charter.
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Collective Fee Take: no modification or onchain implementation introduced.
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Governor/Servicer Role Separation: no change to role structures or authorization patterns.
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Ossified GasLimits: no change
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Direct Fee Margin Controls: no change to the relevant configuration structure and authorization.
Conclusion
U18 is a proposed network upgrade for OP Stack chains that addresses several key improvements:
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Custom Gas Token v2 enables chains to use any asset as their native gas token, providing greater economic flexibility and alignment for diverse ecosystems.
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Creator Pattern Dispute Game Refactor streamlines chain deployment by implementing clone-with-immutable-arguments for dispute game contracts, reducing operational overhead and gas costs while staying within the EIP-7825 transaction gas limit.
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Cannon + Kona introduces a second, Rust-based fault proof implementation alongside the existing Cannon system, strengthening the fault proof layer through increased redundancy and implementation diversity.
These changes enhance the OP Stack’s technical foundation by expanding configurability, improving deployment efficiency, and reinforcing security without impacting existing standard chains using ETH as their gas token.
We request the Collective’s approval to proceed with this upgrade according to the timeline above.