🔴 Optimism just approved the upgrade its Superchain needs before interoperability can go live
Optimism approved Upgrade 20, moving its fault-proof system toward the architecture required for future Superchain interoperability.
The Ethereum layer-2 network’s governance completed voting on Sept. 16, putting OP Sepolia, Ink Sepolia, Soneium Minato and Unichain Sepolia on course for a targeted Sept. 17 contract upgrade. Mainnet execution is scheduled for Sept. 24 if the new system completes a healthy seven-day testnet soak.
The change moves fault proofs from Output Root Dispute Games to Super Root Dispute Games, altering how OP Stack chains challenge incorrect state before withdrawals are finalized back to Ethereum. Optimism describes the upgrade as a prerequisite for interoperability because Super Roots can eventually represent multiple chains at the same timestamp.
That interoperability remains a later step. Upgrade 20 keeps each chain’s dispute infrastructure separate, and each new game still contains the Output Root of a single chain. By making the dispute-system transition now, Optimism aims to avoid modifying that security layer again when it activates cross-chain interoperability.
🔸 Super Roots change withdrawals before chains become interoperable
The biggest operational change comes from how Super Root games identify the state being challenged.
Existing Output Root games anchor a claim to an L2 block number. Super Root games instead use a timestamp, creating the common time reference that an eventual multi-chain dispute system will require. Permissioned chains move to game type 5, while permissionless fault-proof deployments use game type 9.
Chain operators must update their fault-proof infrastructure around the L1 contract cutover. op-challenger and op-dispute-mon need Super Root support before the switch, while op-proposer must move to the new RPC and game type when the upgraded contracts are executed.
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