android-skills

Use this skill as the baseline for ALL Android and Kotlin Multiplatform (KMP) work — whenever the user mentions Android, Kotlin (in an Android context), KMP, CMP, commonMain, androidMain, iosMain, AndroidManifest, Gradle, build.gradle, Hilt, Dagger, Room, Retrofit, Ktor, ViewModel, LiveData, StateFlow, SharedFlow, Compose, Activity, Fragment, Intent, ADB, Logcat, MVVM, MVI, repository pattern, or any Android SDK / Jetpack / AndroidX API. Always load this skill alongside the more specific skills (android-skills:compose, android-skills:kotlin-flows, android-skills:kmp-ktor, android-skills:android-retrofit, etc.): it routes to them and adds the few baseline rules that are easy to get wrong. Casual mentions like "fix this bug in my Android app," "refactor this ViewModel," "my KMP project," or any work inside an Android project directory should trigger this skill.

Compose and Compose Multiplatform expert for UI development across Android, Desktop, iOS, and Web. Covers state management, composition, animations, navigation, performance, design-to-code workflows, and production crash patterns, backed by source analysis from androidx/androidx and JetBrains/compose-multiplatform-core. Use whenever the user mentions Compose, @Composable, remember, LaunchedEffect, Scaffold, NavHost, NavDisplay, MaterialTheme, LazyColumn, Modifier, recomposition, Compose Multiplatform/CMP, commonMain, expect/actual, ComposeUIViewController, UIKitView, ComposeViewport, Res.drawable/Res.string, or any Compose API. Also trigger on phrases like "design to compose", "build this UI", "implement this design", or any modern Kotlin UI question — including casual mentions like "my compose screen is slow". Plus focus topics: FocusRequester, focusProperties, onPreviewKeyEvent, D-pad, TV remote, ChromeOS, androidx.tv.material3.

Use when reading, adding, updating, or removing PDF annotations (highlight, free-text, stamp) or page objects (path/text/image) with Android's platform PDF APIs, or when saving those edits back to disk — the editing surface added in API 36.1 (PdfRenderer.Page) and SDK extension 18 (PdfRendererPreV.Page on API 31+), android.graphics.pdf.component. Covers the version gate, the open-edit-write workflow, and the id/render-flag/save contracts. Not for display-only PdfViewerFragment work, PdfDocument creation-from-scratch, form filling, or third-party PDF SDKs (iText, PDFBox, PSPDFKit).

Use when debugging Android or KMP issues — Android-specific techniques covering Logcat, ADB, ANR traces, R8 stack trace decoding, memory leaks, Gradle build failures, and Compose recomposition bugs, on a root-cause-first foundation.

Use when writing, fixing, or refactoring Android/KMP code in Kotlin — a test-first (RED-GREEN-REFACTOR) foundation plus the Android test traps: Compose-test dispatching (StandardTestDispatcher default, the two-schedulers trap), semantics-first selectors, choosing the smallest test shape, test-clock vs wall-clock, and animation/screenshot determinism.

Use when setting up or working with Ktor client in KMP or Android projects — HttpClient configuration, per-platform engine selection, kotlinx.serialization, bearer auth with refresh, MockEngine testing, and error mapping at the repository boundary.

Use when persisting key-value preferences or small typed settings on Android or KMP with Jetpack DataStore — Preferences vs Typed (Proto/JSON) vs Room selection, the IOException and corruption-recovery error traps, serializers with corruption handlers, and the KMP factory with per-platform file paths. Triggers on DataStore, Preferences, PreferenceDataStoreFactory, DataStoreFactory, preferencesDataStore, Serializer, SharedPreferences-to-DataStore migration, or persistent settings work.

Use when writing or changing any class, object, function, property, or constant in a multi-module Android/Kotlin project (settings.gradle(.kts) includes more than one module — :app, :core:*, :feature:*, :data, etc.). Symptoms — a top-level declaration left at Kotlin's default public visibility; an implementation class, mapper, helper, constant, or UI-state holder reachable from another module though only used within its own; reaching for public "because the caller needs it"; "should this be public or internal?".

Use when implementing the data layer in Android or KMP — the Repository pattern's layered error-propagation model (repository as the error boundary, sealed DataError, Result placement with and without a domain layer) and Room in commonMain (@ConstructedBy, BundledSQLiteDriver, per-target KSP).

Use when designing Kotlin Multiplatform boundaries — choosing between expect/actual, common interfaces with platform bindings, or separate platform screens. Covers platform services (clipboard, share, haptics, permissions, files, settings, sensors, biometrics), native SDKs, source-set hierarchies (commonMain, skikoMain, appleMain, androidMain), Compose Multiplatform interop, and capability granularity. Use whenever common code needs to reach a platform API and you're picking the boundary shape.

Use when writing, reviewing, or debugging coroutine code in Kotlin — including dispatcher selection, scope management, structured concurrency, cancellation, exception handling, or async patterns in Android or KMP projects.

Use when working with Flow, StateFlow, SharedFlow, or Channel in Kotlin — including cold vs hot stream decisions, operator chains, lifecycle-safe collection, UI state management, callback bridging, or Channel migration in Android or KMP projects.

Use when setting up or refactoring Android Gradle build logic — convention plugins, composite builds, version catalogs, and shared build configuration across modules.

Use when setting up or working with Retrofit in Android — service interface definitions, coroutines integration, OkHttp configuration, Hilt module setup, and error handling in the repository layer.

Use when designing or reviewing Android UI — applies Material Design 3 UX principles covering touch targets, spacing, navigation patterns, accessibility, animation timing, and platform conventions. Includes an M3 compliance audit that scores screens across 10 categories. Complements the compose skill with design-level decisions.

Use when loading images in Compose or Compose Multiplatform with Coil 3 — AsyncImage vs SubcomposeAsyncImage vs rememberAsyncImagePainter, ImageRequest configuration, placeholder/error states, performance in lists, and KMP setup with LocalPlatformContext.

Use when Android/Gradle builds are slow — diagnosing bottlenecks with build scans, enabling configuration cache, migrating kapt to KSP, fixing cache misses, and optimizing CI/CD build times.

Use when setting up or working with Koin in Android or KMP projects — module declarations with Classic DSL or KSP annotations, ViewModel injection in Compose, scopes, Nav 3 entry providers, application startup, and compile-time verification via `verify()`. Triggers on Koin, `single`, `factory`, `koinViewModel`, `koinInject`, `parametersOf`, `startKoin`, "KMP DI", "shared DI".

Use when implementing paginated lists in Android or Compose with Paging 3 — PagingSource, Pager and PagingConfig setup, RemoteMediator for offline-first lists, LazyPagingItems and itemKey integration in LazyColumn, dynamic filters via flatMapLatest, and unit tests with TestPager and asSnapshot. Triggers include Paging 3, infinite list, infinite scroll, paginated list, LazyPagingItems, collectAsLazyPagingItems, and cachedIn.

Use when needing to fetch Android source code — AOSP platform internals (@hide APIs, framework classes, system services) or AndroidX/Jetpack library source and samples. Also use when public docs are insufficient to complete a task and implementation details must be read directly from source.

Use only when the user explicitly requests migration from RxJava to Kotlin coroutines and/or flows.