Sushitrain is a native iOS and macOS file synchronization client that embeds the Syncthing P2P sync engine via a Go core exposed through gomobile bindings. The application provides selective synchronization (per-file pick via .stignore), on-demand file streaming, media preview, photo backup from the device camera roll, encrypted folders, and full Apple platform integration including Shortcuts, Handoff, Quick Actions, and background tasks. The architecture separates a SwiftUI frontend from a Go backend that manages Syncthing instance lifecycle, folder/device configuration, block-level downloading (MiniPuller), and local HTTP streaming servers. The codebase demonstrates solid engineering with clean module boundaries, reusable patterns like a pluggable custom filesystem for Syncthing, archive abstraction for ZIP/ISO browsing, and an event-driven UI update mechanism. However, there are signs of technical drift: heavy reliance on a forked Syncthing version with a pre-release pseudo-version, use of older Go libraries, and some duplicated or fragile code paths in the Swift layer (e.g., migration logic, iOS 26 API workarounds). Overall, it is a well-crafted application that fulfills its purpose effectively, though some internal coupling to Syncthing internals limits reusability of the Go components without adaptation.