Proposal Type: Protocol Upgrade
Voting Cycle Type: off-cycle
Hi, I’m Matthew Cruz, Engineering Manager of the Solutions team at OP Labs. I have reviewed this proposal with: Josh Klopfenstein, Paul Dowman, and Andrea Federici from the OP Labs Team. OP Labs and the named individuals herein do not represent or speak on behalf of the Optimism Foundation.
Executive Summary
Upgrade 19 bundles six protocol changes that advance L2 upgradeability, align the OP Stack execution layer with Ethereum’s Fusaka hardfork, promote the Rust kona-client to primary fault proof, and lay groundwork for interop. The L2 hardfork shipped in this upgrade is named Karst.
Karst (L2 hardfork) — execution-layer changes:
- Osaka on L2 — adoption of 7 EIPs from Ethereum’s Fusaka: EIP-7642, EIP-7823, EIP-7825, EIP-7883, EIP-7910, EIP-7939, EIP-7951.
- Glamsterdam Defense: BN256 pairing input size reduction —
bn256Pairingprecompile maximum input reduced from Jovian’s 81,984 bytes (427 pairs) to 57,600 bytes (300 pairs) to restore Jovian-era headroom under EIP-7825’s transaction gas cap, accommodating a potential EIP-7904’s pairing cost increase on L1.
Beyond Karst, Upgrade 19 also bundles four contracts and fault proof related changes:
- L2 Contract Manager (L2CM) — deterministic L2-predeploy upgrade mechanism via
ProxyAdmin.upgradePredeploys(). - OPCMv2 adoption — redesigned OP Contracts Manager v2, replacing OPCM v1’s five functions with two unified
deploy()/upgrade()calls. CANNON_KONAas respected game type + new Kona absolute prestate — the Rust-basedkona-clienton the Cannon VM (deployed as a fallback in U18) becomes the primary fault proof program for withdrawals, with a new absolute prestate. Permissionless fault proof chains flip their respected game type fromCANNONtoCANNON_KONA.- Portal
rootClaim/rootClaimByChainIddispatch by game type — in preparation for interop’sSuperDisputeGame, the OptimismPortal detects the game type and calls eitherrootClaim()orrootClaimByChainId(). TheSuperDisputeGamebranch is dormant in U19 but the dispatch logic ships now so the portal is ready for the next interop-bearing upgrade.
This upgrade also marks the end of support for op-geth and op-program see this notice page for more details.
Motivation
L2 contract upgrades have historically been one of the more brittle parts of the OP Stack’s release process. L2CM addresses this directly by making upgrade transactions “100% deterministic with a clear, immutable record of the exact transactions and bytecode executed.”
OP Contract Manager v2 modernizes the operational tooling used to execute the upgrade itself. The OPCMv2 is an accumulation of learnings and recent changes to the protocol, particularly around dispute game types, and have exposed significant pain points in OPCM v1. Inspiring the consolidation into two unified entry points and the move to dynamic game-type handling.
Osaka on L2 keeps the OP Stack execution layer aligned with L1, preserving the strict equivalence that lets developers reason about gas costs, precompiles, and opcodes consistently across both layers.
The kona-client promotion to primary fault proof and the BN256 input reduction are paired safety measures. Promoting kona-client was driven by the end of support for op-geth/op-program and to consolidate around a Rust implementation of the OP Stack; the BN256 reduction preserves headroom in fault proof transaction sizes so that anticipated L1 precompile cost increases under Glamsterdam’s EIP-7904 cannot push proofs past the maximum transaction size.
The Portal rootClaim / rootClaimByChainId dispatch is small but forward-looking — it prepares the OptimismPortal for the next interop-bearing upgrade without requiring a re-touch of the portal at that time.
Impacted Stakeholders and Expected Outcomes
- App developers:
- EIP-7825 transaction gas limit (Osaka on L2): L2 transactions are now subject to a per-transaction gas limit of 2^24 = 16,777,216 gas. If your application submits transactions with very high gas limits, verify they remain within the new threshold. Deposit transactions are exempt. Most applications will not be affected.
- MODEXP gas changes (EIP-7883 + EIP-7823, Osaka on L2): the gas cost floor for
MODEXP(0x05) increases, and a new input size cap (1024-byte modulus) is enforced. If your contracts callMODEXP, update your gas estimates and verify inputs are within the new size limit. - P256VERIFY gas change (EIP-7951, Osaka on L2): the gas cost for
P256VERIFY(0x100) increases from 3,450 to 6,900 gas. If your contracts callP256VERIFY, update your gas estimates. - CLZ opcode (EIP-7939, Osaka on L2): a new Count Leading Zeros opcode (0x1e) is available. Existing contracts are not affected.
- BN256 pairing input size limit (Glamsterdam Defense): the maximum input for
ecPairing(0x08) is reduced from 427 to 300 pairs (57,600 bytes). If your contracts call the BN256 pairing precompile with more than 300 pairs, those calls will fail. Standard ZK proof verification (e.g., Groth16) is not affected. - Withdrawal proving: the respected game type on permissionless chains changes from
CANNON(0) toCANNON_KONA(8). Standard SDK usage handles this automatically.
- Node operators:
op-gethandop-programare no longer supported. Operators must migrate toop-rethandkona-clientbefore Karst activation. (notice page) - Chain operators: New component versions are required for op-node, op-reth, op-challenger, op-dispute-mon, and op-contracts. The contracts pre-audit release is
op-contracts/v7.0.0-rc.4. Required component versions (must be updated before the activation timestamp). We have information on which components are necessary in our notice page here.
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
L2 Contract Manager (L2CM)
Osaka on L2
- Specs:
- specs/protocol/karst/overview.md — Karst upgrade overview; lists all 7 activated EIPs
- specs/protocol/karst/exec-engine.md — BN256 pairing input size reduction
- specs/protocol/karst/derivation.md — L2CM network upgrade transactions during derivation
- Failure Mode Analysis
Glamsterdam Defense (BN256 pairing input size reduction)
OPCMv2 adoption
Contract Changesx
The contract changes can be found at this contract release tag: op-contracts/v7.0.0-rc.4, which will be finalized as op-contracts/v7.0.0 after this upgrade is approved by governance.
The canonical OPCMv2 address on Ethereum Mainnet is 0x9ce712ff84e02659846dc6450bb9b7642fe8be5d (version 7.1.17; superchain-registry). Chains must be deployed or upgraded via this address to satisfy the Standard Rollup Charter version criteria. A full diff from the previous upgrade can be seen here.
Absolute Prestate
This upgrade includes the absolute presate for kona-proof:
- kona-clientv1.6.0-rc.2: The absolute prestate hash (cannon64-kona variant) is
0x0337ecb3604c0b40c352e0c7711beb17a212d583f4fe956fd8d66e29ad5f9025. It has been publicly verified here.
Calldata
The expected calldata to sign on for a bundled OP, Ink, Mode, Metal, Zora, and Soneium and the seperate Unichain will be commented below (because of a post character limit). This also includes the upgrade on OP Mainnet, Ink, Metal, Mode, and Zora Mainnets as these networks will be upgraded in one superchain-ops task. The Unichain Mainnet calldata will also be posted in a comment below because of the same character limit.
Impact Summary
- Performance: No anticipated downtime.
- Withdrawal proofs: The CANNON_KONA primary fault proof transition after the smart contract upgrade is executed.
- Upgrade documentation: Upgrade 19 notice page covers the operator-facing details, including the op-geth/op-program end of support details.
- Other: None beyond the per-stakeholder items above.
Precommitment Impact Review
This Upgrade Proposal does not impact any of the precommitments in the Standard Rollup Charter.
- Collective Fee Take: no modification or onchain implementation introduced.
- Governor/Servicer Role Separation: no change to role structures or authorization patterns.
- Ossified GasLimits: no change
- Direct Fee Margin Controls: no change to the relevant configuration structure and authorization.
Security Considerations
We have done threat modelling for the new features in this release. The Upgrade 19 audit is a combined audit of the full contracts diff since the last release (op-contracts/v6.0.0).
Action Plan
- Alphanet and Betanet testing has been completed.
- Sepolia activation: Wed, Jun 17, 2026 at 16:00:01 UTC (timestamp
1781712001). Chains:OP,Soneium,Ink,Unichain,Mode,Metal, andZora. Smart contract upgrade will happen prior to activation. - Mainnet smart contract upgrade: expected the week of Jul 1, 2026 (week prior to L2 activation).
- Mainnet L2 activation: Wed, Jul 8, 2026 at 16:00:01 UTC (timestamp
1783526401), pending Optimism Governance approval. Chains:OP,Soneium,Ink,Unichain,Mode,Metal, andZora. Smart contract upgrade will happen prior to activation.
Communication and education plan: The Upgrade 19 notice page is published with necessary information for application developers, chain operators, and node operators to be ready.
Conclusion
Upgrade 19 advances the following goals. L2CM and OPCMv2 make protocol upgrades themselves more deterministic and auditable. Osaka on L2 preserves equivalence with the EVM. The CANNON_KONA promotion as the new respected game type for permissionless fault proof chains. The BN256 reduction takes proactive measures to harden the fault proof system ahead of the Glamsterdam L1 hardfork. This marks the explicit end of support for op-geth and op-program in favor of op-reth and kona-client.