kotlin-footguns skills

Compose look-and-feel traps: theme and colour tokens, artwork palettes, gradients and scrims, shimmer, glass and particle effects, animation, image loading, charts and stats displays (percent changes, shares, buckets). Use when a visual bands, pops, freezes or misleads.

Kotlin Multiplatform structure and language traps: module splits, expect/actual, Koin and ViewModel scoping, layers, version catalogs, erased overloads, Char and string-resource formatting limits. Use when shaping modules or DI, when a format specifier renders verbatim, or code misbehaves on one platform.

WebView traps across device classes: startup that freezes low-RAM phones, a killed renderer that takes the app with it, devices with no usable provider, AndroidView lifecycle and cookies. Use when a web screen freezes, vanishes or crashes only on some devices.

Compose screen and interaction traps: navigation, adaptive layout, window insets, pagers, toolbars, sheets, list drag and selection, sliders, text fields, settings UI, one-shot effects. Use when layout, gestures or navigation misbehave.

Room/SQLite, DataStore and repository traps: migrations, NOT IN with NULLs, LIKE escaping, delete order, local-time bucketing, imports, caching, paging. Use before writing a query or migration, or when data comes back wrong.

Debugging-method traps: run the discriminating experiment first, read build logs bottom-up, treat an empty actual as unwritten, audit shared handles before removing a feature, read commit history critically. Use when a fix is not converging.

Scan a Kotlin or Compose Multiplatform diff for known footgun shapes and open the matching trap to confirm each hit. Use before committing, when reviewing a Kotlin change, or to audit a codebase.

Media player traps on Media3/ExoPlayer and desktop engines: crossfade, audio focus, fades, loudness, DSP, queues and shuffle, position restore, service lifecycle, group listening. Use when playback state, queue or audio levels go wrong.

Reactive state and background-work traps: StateFlow conflation, flatMapLatest, job lifecycles, ViewModel bases, WorkManager, backups, crash reporting, logging, Glance widgets. Use when state lags or flips, or work runs twice or never.

Desktop JVM and build traps: JNA natives, bundling, memory, packaging, code signing, R8, deep links, Gradle and CI releases. Use when a desktop build fails packaged, signed, on another OS or arch, or in CI.

Remote API traps in Kotlin Multiplatform: Ktor clients, defensive parsing, Resource envelopes, OK responses that dropped your data, auth callbacks, retry backoff, downloads, websockets, clock sync. Use when calls succeed but data never lands.