This paper introduces MonadBFT, a novel Byzantine Fault Tolerant (BFT) consensus protocol that advances both performance and robustness. MonadBFT is implemented as the consensus protocol in the Monad blockchain. As a HotStuff-family protocol, MonadBFT has linear message complexity in the common case and is optimistically responsive, operating as quickly as the network allows. A central feature of MonadBFT is its tail-forking resistance. In pipelined BFT protocols, when a leader goes offline, the previous proposal is abandoned. Malicious leaders can exploit this tail-forking behavior as a form of Maximal Extractable Value (MEV) attack by deliberately discarding their predecessor's block, depriving that proposer of rewards and enabling transaction reordering, censorship or theft. MonadBFT prevents such tail-forking attacks, preserving both fairness and integrity in transaction execution. Another related feature of MonadBFT is its notion of speculative finality, which enables parties to execute ordered transactions after a single round (i.e., a single view), with reverts occurring only in the rare case of provable leader equivocation. This mechanism reduces user-perceived latency. Additionally, we introduce the leader fault isolation property, which ensures that the protocol can quickly recover from a failure. To our knowledge, no prior pipelined, leader-based BFT consensus protocol combines all of these properties in a single design.

翻译：本文介绍了MonadBFT，一种新颖的拜占庭容错（BFT）共识协议，其在性能和鲁棒性方面均取得显著进展。MonadBFT已作为共识协议在Monad区块链中实现。作为HotStuff系列协议的一员，MonadBFT在常规情况下具有线性消息复杂度，且具备乐观响应性，能够以网络允许的最快速度运行。MonadBFT的核心特性是其尾部抗分叉能力。在流水线式BFT协议中，当领导者离线时，其先前提案将被废弃。恶意领导者可利用这种尾部分叉行为实施最大可提取价值（MEV）攻击，通过故意丢弃前序区块，剥夺该提案者的收益，并实现交易重排序、审查或窃取。MonadBFT能够防止此类尾部分叉攻击，从而保障交易执行的公平性与完整性。MonadBFT的另一相关特性是其推测性最终性机制，该机制允许参与方在单轮（即单一视图）后执行已排序交易，仅在极少数可证明领导者存在二义性行为的情况下才会发生回滚。这一机制有效降低了用户感知延迟。此外，我们引入了领导者故障隔离特性，确保协议能够从故障中快速恢复。据我们所知，此前尚无任何基于领导者的流水线式BFT共识协议能在单一设计中整合所有这些特性。