> ## Documentation Index
> Fetch the complete documentation index at: https://docs.optimism.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Epilogue

The epilogue stage of the program is intended to perform the final validation on the outputs from the
[execution phase](/rust/kona/sdk/fpp-dev/execution). In most programs, this entails comparing the outputs of the execution phase
to portions of the bootstrap data made available during the [prologue phase](/rust/kona/sdk/fpp-dev/prologue).

Generally, this phase should consist almost entirely of validation steps.

## Example

In the `kona-client` program, the prologue phase only contains two directives:

1. Validate that the L2 safe chain could be produced at the claimed L2 block height.
2. The constructed output root is equivalent to the claimed [L2 output root][l2-output-root].

[l2-output-root]: https://specs.optimism.io/protocol/proposals.html#l2-output-commitment-construction