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?".