[Application Development] How can a smart contract programmatically bridge ETH from an Optimism L2 to Ethereum L1 using the Optimism bridge?

[Zodomo]

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Issue Description

I want to programmatically bridge ETH from an Optimism L2 to Ethereum L1 via a smart contract. Based on what superchain bridge interfaces prompt wallets with, they're calling the bridgeETHTo function on the L2StandardBridge contract. However, after one of these transactions is included in an L1 state root, you need to prove that it is by calling proveWithdrawalTransaction on the OptimismPortal contract on Ethereum L1. How can I produce the inclusion proofs for proveWithdrawalTransaction for a transaction I did not submit and did not prepare via the Optimism SDK (as the smart contract is what initiated it)?

Additional Information

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Feedback

I cannot find any documentation for how to interact with the superchain bridge via smart contracts. Only offchain via your SDK.

[hash1go]

Hello!

If not using the Optimism SDK, you will need to manually create a Merkle proof to prove that the withdrawal transaction is included in the L2 state. This process will require off-chain resources.
Please refer to the relevant specifications for more details.

[sbvegan]

You can also utilize viem: https://viem.sh/op-stack/guides/withdrawals