# Compose Multiplatform

Compose Multiplatform / KMP patterns - expect/actual composables, platform-specific...

- Repository: https://github.com/AThevon/genjutsu (721 stars)
- Category: Mobile
- License: see repository
- Last updated: 2026-11-01
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add AThevon/genjutsu --skill compose-multiplatform -g -a claude-code -y`
Codex: `npx skills add AThevon/genjutsu --skill compose-multiplatform -g -a codex -y`
Cursor: `npx skills add AThevon/genjutsu --skill compose-multiplatform -g -a cursor -y`
Gemini CLI: `npx skills add AThevon/genjutsu --skill compose-multiplatform -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add AThevon/genjutsu`

## Description

Compose Multiplatform / KMP patterns - expect/actual composables, platform-specific code, density and font handling cross-target, iOS/Android/Desktop interop.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

> **Version-sensitive.** Every API name, SDK gate and browser-support claim below was
> verified on **2026-09-08** against primary sources. What against, and when, is in
> `_jutsu/VERSIONS.md`. If that date is old, re-verify before acting on a version number.

# Compose Multiplatform

> Compose Multiplatform (CMP) and Kotlin Multiplatform (KMP) patterns for cross-platform UI.
> Loaded for projects with `org.jetbrains.compose` plugin.
> Foundation: `../compose-motion/SKILL.md` for animation API; this file covers what's specific to writing one Compose codebase for Android + iOS + Desktop + Web.

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## KMP vs CMP - quick clarification

**KMP** (Kotlin Multiplatform) is the language and build infrastructure: shared Kotlin code compiled to JVM, Native (iOS, macOS, Linux, Windows), and Wasm. **CMP** (Compose Multiplatform) is the UI framework on top of KMP, built by JetBrains as a port of Jetpack Compose. You write a single Compose codebase in `commonMain` that runs on Android, iOS, Desktop (JVM), and Web (Wasm). Platform-specific code lives in `androidMain`, `iosMain`, `desktopMain`, `wasmJsMain` and is wired in via `expect`/`actual` declarations.

---

## Project structure

```
composeApp/
├── src/
│   ├── commonMain/        ← shared Compose code (most of the app)
│   │   └── kotlin/
│   ├── androidMain/       ← Android-specific (uses Activity, Context)
│   ├── iosMain/           ← iOS-specific (uses UIKit/UIView interop)
│   ├── desktopMain/       ← JVM desktop (uses java.awt/swing if needed)
│   └── wasmJsMain/        ← Wasm web target
├── build.gradle.kts
iosApp/                    ← Xcode project consuming the generated framework
androidApp/                ← Android Application module (often merged into composeApp)
```

The `commonMain` folder should hold 80-95% of your code in a well-architected CMP project. If `iosMain` or `androidMain` start growing past a few hundred lines, you're probably leaking platform concerns into UI logic that could stay shared.

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The rest: https://github.com/AThevon/genjutsu/blob/HEAD/skills/_jutsu/compose-multiplatform/SKILL.md