Reviewing L2 Sequencer And Finality

---
name: reviewing-l2-sequencer-and-finality
description: "Review L2 assumptions: sequencer downtime, Chainlink sequencer uptime, address aliasing, delayed inbox, custom gas tokens, and optimistic finality windows. Use for OP/Arbitrum/Base/zk and any protocol that reads L1 state from L2."
---

# Reviewing L2 sequencer and finality

In-scope L2 deployments. Combine with `reviewing-oracles-and-pricing` and `reviewing-bridges-and-messaging`.

## Sequencer

- Chainlink L2 sequencer uptime feed + grace period after restart. Missing = stale prices during downtime (paid class).
- Protocol pause when sequencer is down if it liquidates.

## Aliasing / callers

- Optimism `l1Block` / aliasing: L1 sender != raw `msg.sender` on L2.
- Arbitrum retryable tickets: aliased aliased aliased. Confirm the exact alias the messenger uses.

## Finality

- Optimistic: challenge window. A bridge that credits on sequencer receipt without waiting is a bridge finding.
- zk: proof lag vs instant UI.

## Custom gas token / fee token

Accounting that assumes ETH is the gas token breaks on Orbit/OP-custom.

Tests: mock sequencer down (`updatedAt` stale) and assert liquidations revert.

## Paid bounty analogs

Full `$` table: `hunting-x-linked-bounties` `references/paid-payouts.md`.

| $ | Protocol | Pack | Whitehat |
|---|----------|------|----------|
| **$2M** | Optimism OVM SELFDESTRUCT ETH dup | T27 / O04 | saurik |
| ~400 ETH | Arbitrum delayed inbox | T28 | 0xriptide |
| $200k | zkSync Lite proof (LonelySloth; Ehsan 2026 X) | T31 | |
| $50k | zkSync Era soundness | T31 | ChainLight |
| $20k | Optimism censorship | T30 | iosiro |
| $50k total | Trust L1-L2 alias "permission denied" | T27 | Trust Security |
| $1k | Scroll Shabarkin | T31 | Pavel Shabarkin |

Wintermute Safe-on-L2 is a **hack** analog (uninitialized Safe), still this playbook plus `reviewing-upgradeable-proxies`.