Does Jetpack Compose automatically clear lambda captures when a composable exits the composition tree?

Question

Memory Leak Risk from Lambda Captures in Jetpack Compose
In Compose, a composable can capture references in lambda parameters. When the composable is removed from the composition tree, the runtime does not expose a public mechanism to nullify these references, raising the possibility that objects referenced by the lambda remain reachable and cause a memory leak, especially in navigation scenarios where screens are frequently created and destroyed.
Current Compose releases (up to 1.5.x) provide no documented cleanup behavior for lambda captures, and the runtime does not expose an API to query retained composables. Developers must therefore rely on external profilers to detect leaks.
Given these constraints, the key open question is whether the Compose runtime will automatically clear references held by lambda captures when a composable exits the composition tree, and if not, what pattern should be used to guarantee timely cleanup.
Does the Compose runtime automatically nullify references captured in lambdas when a composable is removed from the composition tree? Which lifecycle integration pattern best ensures that ViewModel and lambda captures are released in complex navigation flows?

Tasadduq Burney · Answer

Answer: No automatic clearing
Jetpack Compose does not nullify or remove objects captured by a lambda when the composable that created the lambda leaves the composition tree.
Confirmed facts

The composable’s local scope ends, but any lambda that captured those variables remains alive as long as the lambda itself is reachable from a GC root (e.g., a ViewModel, coroutine, or static field).
If the lambda is stored elsewhere, the captured objects stay strongly referenced and can cause a memory leak.
Compose provides no runtime API to automatically break those captures.

Steps to avoid unintended retention

Keep lambdas that capture composable‑scoped state confined to the composable’s scope; do not expose them to ViewModels, coroutines, or singletons.
If you need to pass a lambda upward, use rememberUpdatedState or pass stable parameters instead of capturing mutable state.
When a lambda must be stored temporarily, explicitly set it to null or remove the reference when the composable is disposed (e.g., in DisposableEffect or LaunchedEffect with key‑change).

To give a precise recommendation, please clarify: Where is the lambda being stored or retained after the composable leaves the tree?

Does Jetpack Compose automatically clear lambda captures when a composable exits the composition tree?

Memory Leak Risk from Lambda Captures in Jetpack Compose

1 answer

Answer: No automatic clearing

Confirmed facts

Steps to avoid unintended retention

Your perspective belongs here.

1 question comment

Explicitly Cleaning Up Lambda Captures