Unit 20 · Language valence: Kotlin under policy · q27b

**Gut Reaction:** This is a recipe for a maintenance nightmare. Kotlin is fantastic for backend and Android, but forcing it as the *sole* language for a high-performance 3D viewport and cross-platform UI (especially iOS) ignores the ecosystem realities. You’re fighting the grain on every layer. **Top 3 Technical Risks:** 1. **iOS UI & 3D Performance Bottleneck:** Kotlin/Native on iOS lacks mature, high-performance UI frameworks (Compose Multiplatform is still maturing for complex 3D integration). You’ll likely end up with a heavy JNI/FFI bridge to native iOS views or a suboptimal Compose renderer, leading to janky 60fps+ 3D rendering and poor native feel. *Risk: Unacceptable UX on half your target platforms.* 2. **Plugin System Complexity & Security:** End-user plugins in a single-language, cross-platform app require a robust sandboxing and reflection/serialization layer. Kotlin’s plugin ecosystem (e.g., KSP, custom classloaders) (greedy generation)

**Gut Reaction:** You are now asking for a Ferrari engine in a go-kart chassis. 120 FPS on mid-range Android with a Kotlin-only stack, async chaos, and user scripts is not just hard; it’s actively hostile to the JVM/Kotlin/Native runtime characteristics. The "cheap Linux CI" constraint is the least of your worries—it’s just a cost optimization. The real killer is the physics of the runtime. **What Breaks First:** **The Main Thread & GC Pauses.** Mid-range Android devices have limited CPU headroom and aggressive thermal throttling. Kotlin runs on the JVM (Android) or Native (iOS/Desktop). - **JVM GC:** Even with ZGC/Shenandoah (not fully supported/optimized on Android), stop-the-world pauses will cause frame drops. 120 FPS = ~8.3ms per frame. A 2ms GC pause is a 24% frame budget loss. - **Kotlin/Native Memory Management:** Reference counting has overhead. Frequent allocation/de (greedy generation)