Function base_code_sentinel_addresses 

pub fn base_code_sentinel_addresses(
    upgrade: BaseUpgrade,
) -> impl Iterator<Item = Address>

Base precompiles installed at upgrade that hold state but carry no bytecode.

Solidity emits an extcodesize check for high-level calls to functions without return data, so a code-less precompile makes the caller revert before the precompile ever runs. Base mainnet plants a one-byte sentinel on exactly these accounts, so mirroring it keeps local execution faithful to the chain.