tracing-recompositions-at-runtime
Tracing Recompositions at Runtime — @TraceRecomposition, logcat, and the live heatmap
Layout Inspector counts recompositions and surfaces Argument Change Reasons, but it works only in debug, where Live Literals and the interpreted Compose runtime inflate counts. @TraceRecomposition from skydoves/compose-stability-analyzer instruments a composable at compile time and emits per-recomposition diffs (which state changed, what value transition) to logcat under the Recomposition tag. The instrumentation works in any build the developer enables it for — including release-with-debug-symbols — and feeds the IntelliJ / Android Studio plugin's live recomposition heatmap.
This skill is the release-mode complement to ../../recomposition/debugging-recompositions/SKILL.md. Layout Inspector is debug-only, fast to set up, and good for the first triage. @TraceRecomposition is the ground-truth confirmation: instrument the suspect composable, ship a release+R8 build of the dev APK, run the user journey, and read the per-recomposition log lines.
When to use this skill
- A composable recomposes more than expected and Layout Inspector counts are inconclusive (the count differs between debug and release, or the suspect is an inline composable not covered by Layout Inspector).
- A stability or strong-skipping fix needs to be confirmed against a release-equivalent build before merging.
- A developer wants per-state-and-per-parameter change diffs printed inline rather than clicking through the Layout Inspector tree.
- A team wants to baseline a composable's recomposition count for an SLO ("PriceTicker recomposes ≤ once per price update; never per parent tick").
- The user mentions
@TraceRecomposition, "trace recomposition", "compose-stability-analyzer", "recomposition logcat", "recomposition heatmap", or "release-mode recomposition".
When NOT to use this skill
More from skydoves/compose-performance-skills
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10deferring-state-reads
Use this skill to push frequently-changing Jetpack Compose state reads (scroll position, animation values, drag offsets) out of the Composition phase and down into Layout or Draw using lambda-based modifiers like Modifier.offset { }, Modifier.layout { }, Modifier.graphicsLayer { }, Modifier.drawBehind { }, and Modifier.drawWithCache { }. Covers the three-phase model (Composition, Layout, Draw), why a state read at phase N invalidates phase N and every phase below, the modifier-phase cheat sheet, and lambda providers (() -> T) for hoisting hot values across composables. Use when the developer mentions every-frame work, scroll jank, animation jank, dropped frames, animated alpha or offset, "the whole subtree recomposes on scroll", Modifier.alpha(state.value), Modifier.offset(x.dp), or graphicsLayer.
9collecting-flows-safely
Use this skill to migrate Compose UI from `collectAsState()` to `collectAsStateWithLifecycle()`, hoist `Flow<T>` parameters out of composables, and apply `.conflate()` / `.distinctUntilChanged()` / `snapshotFlow` so background CPU and battery stop draining and chatty flows stop invalidating the UI per emission. Covers ViewModel `StateFlow`/`SharedFlow` consumers, sensor and location streams, and the "Flow as composable parameter" antipattern. Trigger when the user mentions `collectAsState`, `collectAsStateWithLifecycle`, lifecycle-aware flow collection, `Lifecycle.State.STARTED`, background battery drain from a Compose screen, `snapshotFlow`, `Flow` parameter on a composable, conflate, or distinctUntilChanged.
9debugging-recompositions
Use this skill to find which Jetpack Compose composables are recomposing and why, using Android Studio Layout Inspector recomposition counts and skip counts, the per-parameter Argument Change Reasons (Changed / Unchanged / Uncertain / Static / Unknown) introduced in Android Studio Hedgehog and later, and runtime `@TraceRecomposition` from `compose-stability-analyzer` for production-like measurement. Walks through enabling counts, mapping each Argument Change Reason to a fix, and confirming the result in a release build. Use when the developer says "this should be skipping but isn't", "I want to see recomposition counts", asks what "Uncertain" or "Unknown" means in the inspector, or needs to confirm a stability or strong-skipping fix actually worked end-to-end.
9configuring-lazy-prefetch
Use this skill to tune Jetpack Compose lazy-layout prefetch with LazyLayoutCacheWindow (Compose Foundation 1.9+, @ExperimentalFoundationApi) and pausable composition in prefetch (Compose Foundation 1.10+, default on). Covers configurable Dp-based ahead/behind cache windows plumbed through rememberLazyListState(cacheWindow = ...), NestedPrefetchScope for items containing inner lazy layouts (HorizontalPager inside a LazyColumn row), version requirements, and the trade-off between memory pressure and idle-frame work. Use when the developer mentions dropped frames at high scroll velocity, prefetch window, ahead/behind extents, LazyLayoutCacheWindow, NestedPrefetchScope, pausable composition for prefetch, or wants composition retained for items briefly scrolled past. Item-level fixes (keys, contentType) live in a sibling skill.
9diagnosing-compose-stability
Use this skill to diagnose Jetpack Compose stability problems by enabling and reading the Compose Compiler Reports (classes.txt, composables.txt, composables.csv, module.json). Covers the Gradle DSL, the release-only build requirement, and how to interpret per-class and per-composable stability annotations including stable, unstable, runtime, restartable, skippable, readonly, @static, and @dynamic markers. Use when the developer asks "why does this recompose", reports jank, dropped frames, slow scroll, high recomposition count, suspects an unstable parameter, mentions Compose Compiler Reports, classes.txt, composables.txt, module.json, or wants to know which composables are non-skippable. The fix lives in a sibling skill — this one only diagnoses.
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