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The prologue stage of the program is commonly responsible for bootstrapping the program with inputs from an external source, pulled in through the Host-Client communication implementation. As a rule of thumb, the prologue implementation should be kept minimal, and should not do much more than establish the inputs for the execution phase.

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Example

As an example, the prologue stage of the kona-client program runs through several steps:
  1. Pull in the boot information over the Preimage Oracle ABI, containing:
    • The L1 head hash containing all data required to reproduce the L2 safe chain at the claimed block height.
    • The latest finalized L2 output root.
    • The L2 output root claim.
    • The block number of the L2 output root claim.
    • The L2 chain ID.
  2. Pull in the RollupConfig and L2ChainConfig corresponding to the passed L2 chain ID.
  3. Validate these values.
  4. Pass the boot information to the execution phase.