MessagePipe is a high-performance C# library for in-process and distributed messaging, implementing pub/sub, mediator/CQRS, and request/response patterns with a flexible filter pipeline. It supports both synchronous and asynchronous operations, keyed and keyless subscriptions, and buffered/observable adapters. The library is DI-container agnostic, with first-class integrations for Microsoft.Extensions.DependencyInjection, Unity (Zenject, VContainer), and a built-in lightweight container. Distributed transports include TCP, UDP, Named Pipes, Unix Domain Sockets, Redis, and NATS, with MessagePack binary serialization. A Roslyn analyzer (MPA001) detects forgotten subscription disposal. The codebase is well-structured and performance-optimized (lock-free data structures, pooling, custom awaiters), but suffers from significant code duplication between .NET and Unity variants and embeds large third-party libraries (Zenject, MessagePack) directly in the Unity project, increasing maintenance burden.