Optimism has approved Upgrade 20, moving its fault-proof system (challenges that verify incorrect blockchain state) from Output Root Dispute Games to Super Root Dispute Games. Governance voting concluded on Sept. 16, putting OP Sepolia, Ink Sepolia, Soneium Minato and Unichain Sepolia on course for a targeted Sept. 17 contract upgrade. Mainnet execution, including OP Mainnet and other participating chains, is scheduled for Sept. 24 if the revised system completes a healthy seven-day testnet soak. Super Root games use timestamps rather than L2 block numbers, creating the shared time reference required for eventual multi-chain disputes. Upgrade 20 does not yet make the chains interoperable: each chain retains separate dispute infrastructure, and each game still contains one chain's Output Root. The release also updates Optimism's contracts manager and SystemConfig, adding upgrade-sequencing safeguards and removing legacy configuration functions after issues identified during Upgrade 19. Chain operators must update fault-proof tooling, while withdrawal integrations using viem/op-stack need version 2.51.0 or later and must pass the initiating transaction's L2 timestamp. Ordinary users need no action, existing withdrawal proofs remain valid, and OptimismPortal will accept both dispute-game formats during the transition.