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optimizing-lazy-layouts

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Use this skill to fix scroll jank, lost item state, and broken animateItem() animations in LazyColumn, LazyRow, LazyVerticalGrid, and LazyHorizontalGrid. Covers stable item keys, contentType for mixed-type feeds, Modifier.animateItem() requirements, hoisting modifier chains and painters out of the items lambda, and validating item composable stability. Use when the developer mentions LazyColumn jank, dropped frames while scrolling, items losing scroll state on insert/remove/reorder, mixed feeds of cards/headers/ads feeling sluggish, animateItem() not animating, RecyclerView view-type analog, key parameter, or contentType parameter. The prefetch-window tuning lives in a sibling skill.

lists/optimizing-lazy-layouts/SKILL.md

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Jun 16, 2026
License
Apache-2.0

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# Optimizing Lazy Layouts — Keys, contentType, and animateItem()

Lazy layouts compose only what's visible, but two things still cost: re-composition of items that should have been reused (missing `key`), and per-item allocation that compounds with scroll velocity (missing `contentType`, modifier chains created inside `items { }`). Both have a one-line fix. This skill teaches Claude how to apply that fix correctly and to validate that item composables are themselves skippable. Prefetch tuning is a separate concern — see `../configuring-lazy-prefetch/SKILL.md`.

## When to use this skill

- The developer reports scroll jank, dropped frames, or stutter on a `LazyColumn`, `LazyRow`, `LazyVerticalGrid`, or `LazyHorizontalGrid`.
- Items lose scroll position, focus, or composition state on insert, remove, or reorder.
- A mixed-type feed (cards + headers + ads + carousels) feels sluggish even though each individual row is lightweight.
- `Modifier.animateItem()` was added but no animation runs on inserts or removals.
- The compiler report shows item composables as `unstable`/non-skippable, or `@TraceRecomposition` shows item composables recomposing on every scroll tick.

## When NOT to use this skill
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