Optimism's governance body finalized voting on Sept. 16, clearing the way for Upgrade 20 to be deployed on the OP Sepolia testnet. The upgrade targets a mainnet rollout on Sept. 24, contingent on a successful seven-day testnet period. The change shifts fault-proof mechanisms from Output Root Dispute Games to Super Root Dispute Games, altering how chains challenge incorrect state before withdrawals finalize on Ethereum. This transition establishes a shared timestamp reference that will later support multi-chain dispute resolution across the Superchain. Each OP Stack chain will retain its own dispute infrastructure, with new game types introduced for permissioned and permissionless deployments. Chain operators must adjust fault-proof systems to align with the updated contracts manager and SystemConfig, particularly around upgrade sequencing and legacy function removal. Applications relying on direct dispute game inspection will need to recognize the new game types and retrieve chain-specific roots from the Super Root structure. Withdrawal proof integrations require version 2.51.0 or later of viem/op-stack and must incorporate the L2 timestamp into the proving flow. Ordinary users face no required action, as existing withdrawal proofs remain valid and the OptimismPortal continues to accept both legacy and upgraded dispute formats. The upgrade completes without an L2 hardfork, though operators involved in fault proofs and withdrawals carry the primary migration responsibilities. A smooth seven-day testnet phase will determine whether the Sept. 24 mainnet execution proceeds as scheduled.