# Cross-Chain Finality and Validation (Tezos / Etherlink)

Finality rules for 138, Etherlink, and ALL Mainnet in DON and relay configs.

## Finality by chain

| Chain        | Finality rule        | Use in DON / relay      |
|-------------|----------------------|--------------------------|
| ChainID 138 | QBFT; ~1 confirmation | Commit DON: 1 block finality |
| Ethereum    | 12+ blocks           | Execute DON: wait 12 blocks after commit |
| ALL Mainnet | 12 blocks (default)  | Relay: 12 confirmations  |
| Etherlink   | TBD (e.g. 12)        | **Placeholder:** Set confirmation blocks in relay/DON config when decided; document here. See [TEZOS_CCIP_REMAINING_ITEMS.md](TEZOS_CCIP_REMAINING_ITEMS.md) §2. |

## Validation

- **Commit DON**: Observes source chain (138 or other) for finalized blocks; builds Merkle tree of messages; submits commit report. Use finality rule per source chain.
- **Execute DON**: Waits for commit; verifies Merkle proof; submits execution on destination. Only execute after commit finality.
- **Custom relay**: Wait for source chain confirmations (per table above) before submitting on destination; ensure idempotency (messageId / tx hash).

## Tests

- Confirm finality values in DON and relay configs; run tests that send a message and verify execution only after expected confirmations.