compose-expert

install

source · Clone the upstream repo

git clone https://github.com/aldefy/compose-skill

Claude Code · Install into ~/.claude/skills/

T=$(mktemp -d) && git clone --depth=1 https://github.com/aldefy/compose-skill "$T" && mkdir -p ~/.claude/skills && cp -r "$T/skills/compose-expert" ~/.claude/skills/aldefy-compose-skill-compose-expert && rm -rf "$T"

manifest: skills/compose-expert/SKILL.md

source content

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 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:

Do not follow the generation workflow below
Read
```
references/pr-review.md
```
and follow its workflow exclusively
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

Compose thinks in three phases: Composition → Layout → Drawing. State reads in each phase only trigger work for that phase and later ones.
Recomposition is frequent and cheap — but only if you help the compiler skip unchanged scopes. Use stable types, avoid allocations in composable bodies.

Modifier order matters.

Modifier.padding(16.dp).background(Color.Red)

is visually different from

Modifier.background(Color.Red).padding(16.dp)

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.
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.
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

Start with guidance — read the topic-specific reference (e.g.,
```
references/state-management.md
```
)
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/