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Superchain interop is in active development. Some features may be experimental.
The following predeploys have been added to enable interoperability. Predeployed smart contracts exist at predetermined addresses, coming from the genesis state. They’re similar to precompiles but run directly in the EVM instead of running as native code.

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CrossL2Inbox

The CrossL2Inbox is the system predeploy for cross chain messaging. Anyone can trigger the execution or validation of cross chain messages, on behalf of any user.

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L2ToL2CrossDomainMessenger

The L2ToL2CrossDomainMessenger is a higher level abstraction on top of the CrossL2Inbox that provides general message passing. It’s utilized for secure ERC20 token transfers between L2 chains. Messages sent through the L2ToL2CrossDomainMessenger on the source chain receive both replay protection and domain binding (the executing transaction can only be valid on a single chain).

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SuperchainETHBridge

The SuperchainETHBridge is a predeploy contract that facilitates cross-chain ETH bridging within the Superchain interop cluster. It serves as an abstraction layer on top of the L2ToL2CrossDomainMessenger specifically designed for native ETH transfers between chains. The contract integrates with the ETHLiquidity contract to manage native ETH liquidity across chains, ensuring seamless cross-chain transfers of native ETH.

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ETHLiquidity

The ETHLiquidity contract is a predeploy that manages native ETH liquidity for cross-chain transfers within the Superchain interop set. It works in conjunction with the SuperchainETHBridge to facilitate the movement of ETH between chains without requiring modifications to the EVM to generate new ETH. The contract is initialized with a very large balance (type(uint248).max wei) to ensure it can handle all legitimate minting operations. This design allows the SuperchainETHBridge to have a guaranteed source of ETH liquidity on each chain, which is essential for the cross-chain ETH transfer mechanism.

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SuperchainTokenBridge

The SuperchainTokenBridge is an abstraction on top of the L2ToL2CrossDomainMessenger that facilitates token bridging using interop. It has mint and burn rights over SuperchainERC20 tokens, as described in the token bridging spec.

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