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，在性能和鲁棒性方面均取得进展。MonadBFT被实现为Monad区块链的共识协议。作为HotStuff系列协议，MonadBFT在常见情况下具有线性消息复杂度，且具备乐观响应性，能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，之前的提案会被废弃。恶意领导者可利用这种尾部分叉行为作为最大可提取价值（MEV）攻击手段，通过故意丢弃其前任的区块，剥夺该提案者的奖励，并实现交易重排、审查或窃取。MonadBFT防止了此类尾部分叉攻击，维护了交易执行的公平性和完整性。MonadBFT的另一个相关特性是其推测性最终性概念，允许参与方在单轮（即单一视图）后执行已排序的交易，仅在极少数可证明领导者存在歧义的情况下发生回滚。该机制降低了用户感知的延迟。此外，我们引入了领导者故障隔离特性，确保协议能快速从故障中恢复。据我们所知，此前尚无流水线式、基于领导者的BFT共识协议能在单一设计中同时具备所有这些特性。