This is the final paper in the five-part series The Semantic Arrow of Time. Part I identified the FITO category mistake -- treating forward temporal flow as sufficient for establishing meaning. Part II presented the constructive alternative: the OAE link state machine with its mandatory reflecting phase. Part III showed the FITO fallacy operating at industrial scale in RDMA completion semantics. Part IV traced the same pattern through file synchronization, email, human memory, and language model hallucination. This paper closes the series by constructing the Leibniz Bridge: a unified framework that connects the philosophical foundations (Leibniz's Identity of Indiscernibles, as formalized by Spekkens), the protocol engineering (OAE's bilateral transaction structure), and the physical substrate (indefinite causal order in quantum mechanics). The bridge rests on a single principle: mutual information conservation -- the requirement that every causal exchange preserve the total information accessible to both endpoints, with the direction of time emerging not from axiom but from entropy production when a reversible exchange commits. We show that this principle dissolves the apparent impossibility of the FLP, Two Generals, and CAP theorems by revealing them as theorems about FITO systems, not about physics. We present the triangle network as the minimal topology for semantic consistency without centralized coordination. We conclude with open questions and a reflection on what distributed computing looks like when the FITO assumption is dropped.

翻译：本文是五部曲系列《语义时间之箭》的终篇。第一部分指出了FITO范畴错误——将前向时间流视为确立意义的充分条件。第二部分提出了建设性替代方案：具有强制性反射阶段的OAE链路状态机。第三部分展示了FITO谬误在RDMA完成语义中的工业级规模运作。第四部分通过文件同步、电子邮件、人类记忆和语言模型幻觉追溯了同一模式。本文通过构建“莱布尼茨之桥”来结束本系列：这是一个统一框架，连接了哲学基础（莱布尼茨的不可分辨者同一性原理，由Spekkens形式化）、协议工程（OAE的双边事务结构）和物理基础（量子力学中的不定因果序）。该桥梁基于单一原则：互信息守恒——要求每次因果交换必须保留两个端点均可访问的总信息，而时间方向并非源于公理，而是产生于可逆交换在确定时所产生的熵。我们证明，通过揭示FLP、两将军和CAP定理实为关于FITO系统的定理而非关于物理学的定理，该原则消解了这些定理表面上的不可能性。我们提出三角形网络作为无需集中协调即可实现语义一致性的最小拓扑结构。最后，我们提出开放性问题，并反思当摒弃FITO假设时，分布式计算将呈现何种面貌。