Jetpack Compose Expert Skill
Non-opinionated, practical guidance for writing correct, performant Jetpack Compose code.
Focuses on real pitfalls developers encounter daily, backed by analysis of the actual
androidx/androidx source code (branch: androidx-main).
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?
2. 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 |
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 |
MaterialTheme, ColorScheme, dynamic color, Typography, shapes |
references/theming-material3.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 |
3. 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
4. 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.
Source Code Receipts
Beyond the guidance docs, this skill bundles the actual source code from
androidx/androidx (branch: androidx-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 |
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
compose/
├── runtime/runtime/src/commonMain/kotlin/androidx/compose/runtime/
├── ui/ui/src/androidMain/kotlin/androidx/compose/ui/platform/
├── ui/ui/src/commonMain/kotlin/androidx/compose/ui/
├── foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/
├── material3/material3/src/commonMain/kotlin/androidx/compose/material3/
└── navigation/navigation-compose/src/commonMain/kotlin/androidx/navigation/compose/
Source: akitikkx/upnext — distributed by TomeVault.
1---2name: akitikkx-upnext-upnext3description: Jetpack Compose Expert Skill4---56# Jetpack Compose Expert Skill78Non-opinionated, practical guidance for writing correct, performant Jetpack Compose code.9Focuses on real pitfalls developers encounter daily, backed by analysis of the actual10`androidx/androidx` source code (branch: `androidx-main`).1112## Workflow1314When helping with Compose code, follow this checklist:1516### 1. Understand the request17- What Compose layer is involved? (Runtime, UI, Foundation, Material3, Navigation)18- Is this a state problem, layout problem, performance problem, or architecture question?1920### 2. Consult the right reference21Read the relevant reference file(s) from `references/` before answering:2223| Topic | Reference File |24|-------|---------------|25| `@State`, `remember`, `mutableStateOf`, state hoisting, `derivedStateOf`, `snapshotFlow` | `references/state-management.md` |26| Structuring composables, slots, extraction, preview | `references/view-composition.md` |27| Modifier ordering, custom modifiers, `Modifier.Node` | `references/modifiers.md` |28| `LaunchedEffect`, `DisposableEffect`, `SideEffect`, `rememberCoroutineScope` | `references/side-effects.md` |29| `CompositionLocal`, `LocalContext`, `LocalDensity`, custom locals | `references/composition-locals.md` |30| `LazyColumn`, `LazyRow`, `LazyGrid`, `Pager`, keys, content types | `references/lists-scrolling.md` |31| `NavHost`, type-safe routes, deep links, shared element transitions | `references/navigation.md` |32| `animate*AsState`, `AnimatedVisibility`, `Crossfade`, transitions | `references/animation.md` |33| `MaterialTheme`, `ColorScheme`, dynamic color, `Typography`, shapes | `references/theming-material3.md` |34| Recomposition skipping, stability, baseline profiles, benchmarking | `references/performance.md` |35| Semantics, content descriptions, traversal order, testing | `references/accessibility.md` |36| Removed/replaced APIs, migration paths from older Compose versions | `references/deprecated-patterns.md` |37| **Styles API** (experimental): `Style {}`, `MutableStyleState`, `Modifier.styleable()` | `references/styles-experimental.md` |3839### 3. Apply and verify40- Write code that follows the patterns in the reference41- Flag any anti-patterns you see in the user's existing code42- Suggest the minimal correct solution — don't over-engineer4344### 4. Cite the source45When referencing Compose internals, point to the exact source file:46```47// See: compose/runtime/runtime/src/commonMain/kotlin/androidx/compose/runtime/Composer.kt48```4950## Key Principles51521. **Compose thinks in three phases**: Composition → Layout → Drawing. State reads in each53 phase only trigger work for that phase and later ones.54552. **Recomposition is frequent and cheap** — but only if you help the compiler skip unchanged56 scopes. Use stable types, avoid allocations in composable bodies.57583. **Modifier order matters**. `Modifier.padding(16.dp).background(Color.Red)` is visually59 different from `Modifier.background(Color.Red).padding(16.dp)`.60614. **State should live as low as possible** and be hoisted only as high as needed. Don't put62 everything in a ViewModel just because you can.63645. **Side effects exist to bridge Compose's declarative world with imperative APIs**. Use the65 right one for the job — misusing them causes bugs that are hard to trace.6667## Source Code Receipts6869Beyond the guidance docs, this skill bundles the **actual source code** from70`androidx/androidx` (branch: `androidx-main`). When you need to verify how something71works internally, or the user asks "show me the actual implementation", read72the raw source from `references/source-code/`:7374| Module | Source Reference | Key Files Inside |75|--------|-----------------|------------------|76| Runtime | `references/source-code/runtime-source.md` | Composer.kt, Recomposer.kt, State.kt, Effects.kt, CompositionLocal.kt, Remember.kt, SlotTable.kt, Snapshot.kt |77| UI | `references/source-code/ui-source.md` | AndroidCompositionLocals.android.kt, Modifier.kt, Layout.kt, LayoutNode.kt, ModifierNodeElement.kt, DrawModifier.kt |78| Foundation | `references/source-code/foundation-source.md` | LazyList.kt, LazyGrid.kt, BasicTextField.kt, Clickable.kt, Scrollable.kt, Pager.kt |79| Material3 | `references/source-code/material3-source.md` | MaterialTheme.kt, ColorScheme.kt, Button.kt, Scaffold.kt, TextField.kt, NavigationBar.kt |80| Navigation | `references/source-code/navigation-source.md` | NavHost.kt, ComposeNavigator.kt, NavGraphBuilder.kt, DialogNavigator.kt |8182### Two-layer approach831. **Start with guidance** — read the topic-specific reference (e.g., `references/state-management.md`)842. **Go deeper with source** — if the user wants receipts or you need to verify, read from `references/source-code/`8586### Source tree map87```88compose/89├── runtime/runtime/src/commonMain/kotlin/androidx/compose/runtime/90├── ui/ui/src/androidMain/kotlin/androidx/compose/ui/platform/91├── ui/ui/src/commonMain/kotlin/androidx/compose/ui/92├── foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/93├── material3/material3/src/commonMain/kotlin/androidx/compose/material3/94└── navigation/navigation-compose/src/commonMain/kotlin/androidx/navigation/compose/95```9697---98> Source: [akitikkx/upnext](https://github.com/akitikkx/upnext) — distributed by [TomeVault](https://tomevault.io).99<!-- tomevault:4.0:skill_md:2026-06-17 -->
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