ScreenSafe: A Technical Chronicle of On-Device AI and Privacy-First Architecture

The Problem: Cloud-based moderation violates privacy, but on-device AI hits hostile OS limits—specifically the iOS Share Extension memory ceiling (120MB) and Android's Binder IPC limit (1MB). The Solution: We architected the "Courier Pattern" (using App Groups and Deep Links) to bypass iOS memory kills and implemented URI streaming to circumvent Android transaction limits. The Result: ScreenSafe achieves 100% offline, privacy-first redaction with real-time latency (30-100ms) by integrating the C++ Cactus framework directly into React Native.