# Compose Expert

> Compose and Compose Multiplatform expert skill for UI development across Android, Desktop, iOS, and Web. Guides state management, view composition, animations, navigation, performance, design-to-code workflows, and production crash patterns. Backed by actual source code analysis from both androidx/androidx and JetBrains/compose-multiplatform-core. Use this skill whenever the user mentions Compose, @Composable, remember, LaunchedEffect, Scaffold, NavHost, MaterialTheme, LazyColumn, Modifier, recomposition, Style, styleable, MutableStyleState, Compose Multiplatform, CMP, KMP, commonMain, expect, actual, ComposeUIViewController, Window composable, UIKitView, ComposeViewport, Res.drawable, Res.string, or any Compose API. Also trigger when the user says "Android UI", "Kotlin UI", "compose layout", "compose navigation", "compose animation", "material3", "compose styles", "compose multiplatform", "desktop compose", "iOS compose", "compose web", "design to compose", "build this UI", "implement this design", "Android

- Skill: `pushpalroy/compose-expert` (Agent Skill, multi-file: 29 files)
- Install (CLI): `npx skillmds@latest add pushpalroy/compose-expert`
- Raw SKILL.md: https://api.skillmd.com/api/skills/pushpalroy/compose-expert/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Integrations & APIs
- Author: pushpalroy (https://skillmd.com/u/pushpalroy)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/pushpalroy/compose-expert

---


> **Installation notice:** This skill is now distributed as a plugin.
> If you copied files into `~/.claude/skills/` manually, you are on an
> unmaintained install path and will not receive updates. Migrate via:
>
>     /plugin marketplace add aldefy/compose-skill
>     /plugin install compose-expert
>
> See [MIGRATION.md](../docs/MIGRATION.md) for Codex and Copilot CLI instructions.
> This banner will remain through v2.x and escalate in v3.0.

# Compose Expert Skill

Non-opinionated, practical guidance for writing correct, performant Compose code —
across Android, Desktop, iOS, and Web. Covers Jetpack Compose and Compose Multiplatform.
Backed by analysis of actual source code from `androidx/androidx` and
`JetBrains/compose-multiplatform-core`.

## Review Mode

**Activate when** the input contains a GitHub PR URL (`github.com/.+/pull/\d+`) or
explicit review phrases: "review this PR", "review this diff", "check this code",
"what's wrong with this".

When Review Mode activates:
1. Do **not** follow the generation workflow below
2. Read `references/pr-review.md` and follow its workflow exclusively
3. Output a structured local review report — do not post to GitHub

## Workflow

When helping with Compose code, follow this checklist:

### 1. Understand the request
- What Compose layer is involved? (Runtime, UI, Foundation, Material3, Navigation)
- Is this a state problem, layout problem, performance problem, or architecture question?
- Is this Android-only or Compose Multiplatform (CMP)?

### 2. Analyze the design (if visual reference provided)
- If the user shares a Figma frame, screenshot, or design spec, consult `references/design-to-compose.md`
- Decompose the design into a composable tree using the 5-step methodology
- Map design tokens to MaterialTheme, spacing to CompositionLocals
- Identify animation needs and consult `references/animation.md` for recipes

### 3. Consult the right reference
Read the relevant reference file(s) from `references/` before answering:

| Topic | Reference File |
|-------|---------------|
| `@State`, `remember`, `mutableStateOf`, state hoisting, `derivedStateOf`, `snapshotFlow` | `references/state-management.md` |
| Structuring composables, slots, extraction, preview | `references/view-composition.md` — for design system structure, also see `references/atomic-design.md` |
| Modifier ordering, custom modifiers, `Modifier.Node` | `references/modifiers.md` |
| `LaunchedEffect`, `DisposableEffect`, `SideEffect`, `rememberCoroutineScope` | `references/side-effects.md` |
| `CompositionLocal`, `LocalContext`, `LocalDensity`, custom locals | `references/composition-locals.md` |
| `LazyColumn`, `LazyRow`, `LazyGrid`, `Pager`, keys, content types | `references/lists-scrolling.md` |
| `NavHost`, type-safe routes, deep links, shared element transitions | `references/navigation.md` |
| `animate*AsState`, `AnimatedVisibility`, `Crossfade`, transitions | `references/animation.md` — for M3 token selection, also see `references/material3-motion.md` |
| `MaterialTheme`, `ColorScheme`, dynamic color, `Typography`, shapes | `references/theming-material3.md` — for motion, see `references/material3-motion.md`; for design tokens, see `references/atomic-design.md` |
| Recomposition skipping, stability, baseline profiles, benchmarking | `references/performance.md` |
| Semantics, content descriptions, traversal order, testing | `references/accessibility.md` |
| Removed/replaced APIs, migration paths from older Compose versions | `references/deprecated-patterns.md` |
| **Styles API** (experimental): `Style {}`, `MutableStyleState`, `Modifier.styleable()` | `references/styles-experimental.md` |
| Figma/screenshot decomposition, design tokens, spacing, modifier ordering | `references/design-to-compose.md` |
| Production crash patterns, defensive coding, state/performance rules | `references/production-crash-playbook.md` |
| Compose Multiplatform, `expect`/`actual`, resources (`Res.*`), migration | `references/multiplatform.md` |
| Desktop (Window, Tray, MenuBar), iOS (UIKitView), Web (ComposeViewport) | `references/platform-specifics.md` |
| TV Compose: Surface, Carousel, NavigationDrawer, Cards, focus, D-pad | `references/tv-compose.md` |
| M3 motion tokens, `MotionTokens`, `MotionScheme`, animation duration, easing | `references/material3-motion.md` |
| PR URL, code review, "review this PR", "what's wrong with this" | `references/pr-review.md` |
| Session start, project detection | `references/auto-init.md` |
| Atomic design, design system, reusable component, component library, design tokens | `references/atomic-design.md` |

### 4. Apply and verify
- Write code that follows the patterns in the reference
- Flag any anti-patterns you see in the user's existing code
- Suggest the minimal correct solution — don't over-engineer

### 4a. Component building mode
When the request involves building a component (composable that renders UI):
- Consult `references/atomic-design.md`
- Classify the component level (atom, molecule, organism, template)
- Apply the "Ask" prompt from Section 5 before scaffolding code
- Ensure the component satisfies the atom contract (modifier, slots, tokens, defaults)

### 5. Cite the source
When referencing Compose internals, point to the exact source file:
```
// See: compose/runtime/runtime/src/commonMain/kotlin/androidx/compose/runtime/Composer.kt
```

## Key Principles

1. **Compose thinks in three phases**: Composition → Layout → Drawing. State reads in each
   phase only trigger work for that phase and later ones.

2. **Recomposition is frequent and cheap** — but only if you help the compiler skip unchanged
   scopes. Use stable types, avoid allocations in composable bodies.

3. **Modifier order matters**. `Modifier.padding(16.dp).background(Color.Red)` is visually
   different from `Modifier.background(Color.Red).padding(16.dp)`.

4. **State should live as low as possible** and be hoisted only as high as needed. Don't put
   everything in a ViewModel just because you can.

5. **Side effects exist to bridge Compose's declarative world with imperative APIs**. Use the
   right one for the job — misusing them causes bugs that are hard to trace.

6. **Compose Multiplatform shares the runtime but not the platform**. UI code in
   `commonMain` is portable. Platform-specific APIs (`LocalContext`, `BackHandler`,
   `Window`) require `expect`/`actual` or conditional source sets.

## Source Code Receipts

Beyond the guidance docs, this skill bundles the **actual source code** from
`androidx/androidx` (branch: `androidx-main`) and `JetBrains/compose-multiplatform-core`
(branch: `jb-main`). When you need to verify how something works internally, or the
user asks "show me the actual implementation", read the raw source from
`references/source-code/`:

| Module | Source Reference | Key Files Inside |
|--------|-----------------|------------------|
| Runtime | `references/source-code/runtime-source.md` | Composer.kt, Recomposer.kt, State.kt, Effects.kt, CompositionLocal.kt, Remember.kt, SlotTable.kt, Snapshot.kt |
| UI | `references/source-code/ui-source.md` | AndroidCompositionLocals.android.kt, Modifier.kt, Layout.kt, LayoutNode.kt, ModifierNodeElement.kt, DrawModifier.kt |
| Foundation | `references/source-code/foundation-source.md` | LazyList.kt, LazyGrid.kt, BasicTextField.kt, Clickable.kt, Scrollable.kt, Pager.kt |
| Material3 | `references/source-code/material3-source.md` | MaterialTheme.kt, ColorScheme.kt, Button.kt, Scaffold.kt, TextField.kt, NavigationBar.kt |
| Navigation | `references/source-code/navigation-source.md` | NavHost.kt, ComposeNavigator.kt, NavGraphBuilder.kt, DialogNavigator.kt |
| CMP | `references/source-code/cmp-source.md` | Window.kt, ComposeUIViewController.kt, UIKitView.kt, ComposeViewport.kt, ResourceReader.kt |

### Two-layer approach
1. **Start with guidance** — read the topic-specific reference (e.g., `references/state-management.md`)
2. **Go deeper with source** — if the user wants receipts or you need to verify, read from `references/source-code/`

### Source tree map
```
androidx/androidx (branch: androidx-main)
├── compose/runtime/runtime/src/commonMain/kotlin/androidx/compose/runtime/
├── compose/ui/ui/src/androidMain/kotlin/androidx/compose/ui/platform/
├── compose/ui/ui/src/commonMain/kotlin/androidx/compose/ui/
├── compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/
├── compose/material3/material3/src/commonMain/kotlin/androidx/compose/material3/
├── compose/navigation/navigation-compose/src/commonMain/kotlin/androidx/navigation/compose/
├── tv/tv-material/src/main/java/androidx/tv/material3/
└── tv/tv-foundation/src/main/java/androidx/tv/foundation/

compose-multiplatform-core (branch: jb-main)
├── compose/ui/ui/src/desktopMain/kotlin/androidx/compose/ui/window/
├── compose/ui/ui/src/iosMain/kotlin/androidx/compose/ui/window/
├── compose/ui/ui/src/webMain/kotlin/androidx/compose/ui/window/
├── compose/ui/ui/src/skikoMain/kotlin/androidx/compose/ui/
└── compose/foundation/foundation/src/skikoMain/kotlin/androidx/compose/foundation/

compose-multiplatform (resources library)
└── components/resources/library/src/commonMain/
```