/compose-state-and-effects

name: compose-state-and-effects
description: Use when writing or reviewing Jetpack Compose state ownership, remember state, state hoisting, screen state holders, LaunchedEffect, DisposableEffect, SideEffect, Flow collection, navigation, snackbar, analytics, or focus requests.

Compose state and effects

Core principle

Give every piece of UI state one lowest responsible owner, then run imperative work through the effect whose lifecycle follows that owner. Composition renders; state and effects make rendering change safely.

A screen-ownership review is incomplete until it names the plain, previewable content composable that receives immutable state and event callbacks separately from app wiring and composition-owned runtime objects.

Procedure

1. Establish the requested scope and visible behavioral requirements. Treat an ownership change as a finding only when code or task evidence shows a lifecycle, testability, business, or coordination need. In a focused contract or correctness review, a missing provider, owner, or writer that the code never needs is at most a noted risk; do not recommend ownership, default-value, or API-surface changes for it, even as optional. 2. Inventory mutable UI state, app state, event streams, app dependencies, and imperative work in the affected screen or component. 3. Place each state value at its lowest necessary owner: local UI state, hoisted state, a plain UI state holder, or a screen state holder. 4. For a screen boundary, keep durable data and intents in the wiring owner, Compose runtime objects in composition or a plain UI state holder, and rendering in a previewable content composable that takes immutable state and callbacks. Read [State hoisting](references/state-hoisting.md) for the implementation shape; naming only state and intents is not that boundary. Keep this content callable with sample state and callbacks; an `@Preview` wrapper is optional and is not required for the state-driven boundary. Before adding it, confirm the module declares its tooling; do not assume Compose runtime or UI dependencies provide it. Respect the task's file scope: do not add tooling or change build files unless authorized. If Preview tooling is needed but unavailable within scope, omit the wrapper and report the setup gap. 5. Choose an effect API whose lifecycle matches the work, and key it by the semantic input that should restart or dispose it. 6. Load the focused reference for every material concern below. Do not use a reference merely because its topic is adjacent. 7. Route frame-rate reads, cross-phase back-writing, and `@ReadOnlyComposable` contracts to [Compose performance](../compose-performance/SKILL.md). For that contract, distinguish a read of snapshot `State.value` from an operation that changes the composer; the state read alone is not a violation. 8. Before responding to a screen-ownership review, verify all three screen seams in step 4 when visible code needs them. 9. Finish when every state value has one owner, every effect has a justified lifecycle and key, and the UI can be previewed and tested without app dependencies. For review-only work, report no change when no evidence-backed issue remains; do not invent product requirements.

Topic router

| Signal | Read | |---|---| | Bare local `var`, `remember { mutableStateOf(...) }`, state lists/maps, or reset state | [Local state](references/local-state.md) | | State shared by siblings, UI state holders, ViewModel/component wiring, or previewable screen boundaries | [State hoisting](references/state-hoisting.md) | | `LaunchedEffect`, `DisposableEffect`, `SideEffect`, `snapshotFlow`, `rememberCoroutineScope`, `rememberUpdatedState`, `produceState`, imperative `requestFocus`, callbacks, event Flow collection, snackbar, navigation, or analytics | [Side effects](references/side-effects.md) | | Focus ownership and keyboard/TV/D-pad behavior | [Compose focus navigation](../compose-focus-navigation/SKILL.md) | | Tests or previews for the resulting UI contract | [Compose UI testing patterns](../compose-ui-testing-patterns/SKILL.md) |