Margelo

Design, implement, and review Swift APIs and Apple-platform code. Use when working on .swift files, Swift types, Foundation or AVFoundation APIs, DispatchQueue, async/await, Task, actors, MainActor, thread-affine state, or Swift-backed React Native Nitro Module implementations.

Design and review production-grade low-latency VisionCamera v5 pipelines. Use for real-time GPU, ML, CV, Skia or WebGPU overlays, Nitro frame plugins, zero-copy interop, frame budgets, and latency profiling. Use the general react-native-vision-camera skill for setup, capture, controls, basic frame outputs, or v4 migration.

Best-practices guide for React Native VisionCamera v5 setup, migration, capture, controls, outputs, and basic frame processing. Use the separate react-native-vision-camera-realtime skill for production low-latency GPU, ML, CV, Skia or WebGPU pipelines and frame-coupled overlays.

Fast synchronous key-value storage for React Native via react-native-mmkv (Nitro-backed). Covers creating and configuring MMKV instances, reading/writing all value types (string, number, boolean, buffer), React hooks for reactive UI, value-change listeners, encryption, AsyncStorage migration, and state-management integrations (zustand, redux-persist, jotai, react-query). Also covers storage limits, multi-process mode, and the V4 upgrade from the class-based API.

Fast native networking primitives for React Native built on Nitro Modules — react-native-nitro-fetch, react-native-nitro-websockets, and react-native-nitro-text-decoder. Covers the fetch API, global replacement, prefetching and cold-start cache warming, the NitroWebSocket class and pre-warming, migrating from React Native's built-in WebSocket, the in-process NetworkInspector, native Perfetto / Instruments tracing, the native TextDecoder, and plugging nitro-fetch into axios via a custom adapter.

Design, implement, and review Kotlin and Android APIs. Use when working on .kt files, Kotlin nullability, sealed classes/interfaces, coroutines, Android threading, Java interop, or Kotlin-backed React Native Nitro Module implementations.

Design, implement, and review modern C++ APIs and native implementation code. Use when working on .cpp, .hpp, CMake, RAII ownership, std::variant, callbacks, async work, platform bridges, or C++-backed React Native Nitro Module implementations.

Builds and designs React Native Nitro Modules with Nitrogen, HybridObject TypeScript specs, Nitro View components, generated native implementations, zero-copy and native-state APIs, Swift/Kotlin/C++ bindings, example apps, and testing. Use when creating a Nitro Module, adding or reviewing HybridObjects, building a Nitro View (HybridView) component, designing Nitro-specific public APIs, implementing native functionality, or setting up the nitrogen codegen pipeline. Pair with api-design for general library API shape.

Design and review predictable public APIs for TypeScript, JavaScript, React, and React Native libraries. Use when shaping exported functions, classes, hooks, options objects, event and listener APIs, error behavior, naming, cross-platform abstractions, or JS-only packages. Pair with build-nitro-modules when the library is backed by Nitro.