Individual skill
choosing-derivedstateof
Use this skill to decide when Jetpack Compose derivedStateOf is the right tool and when it is pure overhead. Covers the "input frequency must exceed output frequency" rule, the mandatory remember { derivedStateOf { } } wrapper, the canonical pitfall of capturing non-state variables by initial value (and the remember(key) fix), and the snapshotFlow alternative for fire-and-forget side effects on derived values. Use when the developer mentions derivedStateOf, scroll-position-driven booleans, threshold checks, firstVisibleItemIndex, "show FAB on scroll", recomposition counts that don't drop after wrapping a value, or asks whether a computed string concatenation should use derivedStateOf.
recomposition/choosing-derivedstateof/SKILL.md
Source commit 1b32f81724c0d71fe9ef093ca44697f559fdab6e
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- Observed behavior
- Instructions only
- Last checked
- Nov 6, 2026
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- Repository last updated
- Jun 16, 2026
- License
- Apache-2.0
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- agent-skills Repository topic
- android Repository topic
- claude Repository topic
- claude-code Repository topic
- compose Repository topic
- jetpack-compose Repository topic
- kotlin Repository topic
- llm-tools Repository topic
- recomposition Repository topic
- skydoves Repository topic
- engineering Derived category
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SKILL.mdcore · 11,828 bytes
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# Choosing derivedStateOf — Filter Hot Inputs into Cold Outputs
`derivedStateOf` produces a `State` whose readers only invalidate when the **derived result** changes, even if the input states change far more often. Use it when input frequency exceeds output frequency. Use it for any other shape and it is pure overhead — an extra snapshot subscription with no filtering benefit. This skill teaches Claude when to reach for it, when to refuse, and how to avoid the canonical capture-by-initial-value pitfall.
## When to use this skill
- The developer asks whether a value should be wrapped in `derivedStateOf`.
- A scroll position drives a boolean (`firstVisibleItemIndex == 0`, `scrollState.value > threshold`, "show FAB on scroll").
- A high-frequency input (drag delta, animation progress) feeds a low-frequency output (boolean threshold, bucketed integer).
- A `derivedStateOf` exists in the code but recomposition counts didn't drop, or the value never updates after the first composition (the capture-by-initial-value bug).
- The developer wants a one-shot side effect (analytics, logging, snackbar) when a derived value flips.
## When NOT to use this skill
