docs: add Upgrade 20 operator notice

[sbvegan]

What changed

• Added the Upgrade 20 operational notice, including its motivation, L1 smart contract scope, and the September execution expectation pending governance approval.
• Documented the move from Output Root to Super Root Dispute Games without an L2 hardfork.
• Added the required op-proposer, op-challenger, and op-dispute-mon configuration changes for permissioned and permissionless Fault Proof deployments.
• Added standard and custom-chain workflows for reproducing the reviewed kona-client Interop prestate.
• Documented the removal of SystemConfig.batchInbox() and setGasConfig(uint256,uint256), the retained deprecated overhead() getter, and the FEE_SCALARS event compatibility behavior.
• Added breaking-change guidance for chain operators, node operators, app developers and infrastructure integrators, and users.
• Documented viem 2.51.0 as the minimum release for Super Root withdrawal proving, including the required l2Timestamp and game call changes.
• Updated both L2-to-L1 viem tutorials with a transition-safe withdrawal prove flow that works before and after a chain moves to Super Root Dispute Games.
• Updated the application tooling support matrix and linked the notice from the notices landing page and navigation.

Why

Upgrade 20 prepares OP Stack Fault Proof infrastructure to use Super Root Dispute Games, which represent claims in the form needed for multi-chain Fault Proofs and the path to Interop. The notice gives operators and application integrators one place to understand the service cutover, the smaller L1 contract-interface changes included in the upgrade, persona-specific breaking changes, and compatibility behavior for disputes and withdrawals already in progress.

Upgrade 20 is an L1 smart contract upgrade. It does not include an L2 hardfork.

Tracks ethereum-optimism/solutions#1087.

Sources

• ethereum-optimism/solutions#1087: notice requirements
• ethereum-optimism/solutions#1137: Super Root Dispute Game scope and Kona Interop prestate requirement
• ethereum-optimism/solutions#1138 and L1 contracts upgrade to op-contracts/v7.0.0-rc.4 overrides SystemConfig.batchInbox value. #21614: SystemConfig cleanup scope, motivation, and third-party impact
• contracts-bedrock: remove SystemConfig batchInbox and setGasConfig #21641 and system-config: remove batchInbox getter and setGasConfig specs#922: SystemConfig implementation and specification changes
• docs/design/super-dispute-game-migration.md and the Interop Fault Proof specification: Super Root migration design and withdrawal compatibility
• feat(op-stack): Add support for super root games wevm/viem#4597 and viem@2.51.0: upstream Super Root withdrawal proving support and the required timestamp/game API flow
• docs/public-docs/chain-operators/tutorials/upgrade-chain-to-super-roots.mdx: existing migration and cutover runbook
• op-challenger/game/types/game_type.go: supported challenger game types
• op-proposer/flags/flags.go, op-challenger/flags/flags.go, and op-dispute-mon/flags/flags.go: operator-facing flags and environment variables
• rust/justfile: reproducible standard and custom Interop prestate build recipes

Verification

• Navigation validator
• Redirect validator
• Link-policy linter with the repository baseline
• JavaScript syntax checks for the updated viem withdrawal examples
• Shell syntax checks for the prestate commands
• git diff --check

Reviewer checklist

• Confirm the Upgrade 20 L1 smart contract scope, September expectation, and no-hardfork framing.
• Confirm the permissioned and permissionless Fault Proof service configuration changes.
• Confirm the standard and custom kona-client Interop prestate workflows.
• Confirm the SystemConfig removal and integration guidance.
• Confirm the breaking-change guidance for each affected persona.
• Confirm the viem minimum version and withdrawal call changes.

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