tari-project / tari / 26450381733

61%

Build Type

push

github

Committed by web-flow

Commit Message

feat(sidechain)!: carry next-epoch hash in EndEpoch command (#7856)

## Description

Adds `EndEpochAtom { next_epoch_hash }` and changes `Command::EndEpoch`
to `Command::EndEpoch(EndEpochAtom)`.

The next epoch's base-layer boundary-block hash is now carried inside
the `EndEpoch` command, so it becomes part of the block's command merkle
root and is attested by the quorum that commits the end-of-epoch block.

## Motivation

Today each validator derives the next epoch's boundary hash from its own
base-layer oracle and locks it unilaterally when it stamps the next
epoch's genesis. When a base-layer reorg deeper than the confirmation
depth straddles an epoch boundary, the committee can split across two
different boundary-block hashes, after which nodes reject each other's
proposals (`InvalidEpochHash`) and consensus wedges with no automatic
recovery.

Carrying the hash in the command lets the committee **ratify the next
epoch's hash by quorum** instead: a validator only votes for the EOE
block if `next_epoch_hash` matches its own (lagged, reorg-stable) view,
so a hash can no longer be locked without agreement. The layer-2
consensus changes that consume this live in the tari-ootle repo.

## Notes

- The command still hashes via `command_hasher().chain(self)` (Borsh),
keeping the layer-2 command hash consistent with the consensus block's
command merkle root. The matching tari-ootle `Command` change preserves
byte-identical hashing so L1 inclusion-proof verification is unaffected.
- `EndEpoch` stays the last enum variant (Borsh index unchanged).

## How Has This Been Tested?

`cargo build` and `cargo test` for `tari_sidechain` pass.

Coverage Stats

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72082 of 117125 relevant lines covered (61.54%)

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