"Entity does not exist" warning triggered by `DespawnOnExitState` for all child components

[will-hart]

Bevy version

bevy = { git = "https://github.com/bevyengine/bevy", branch = "main" } (commit c6ae964)

What you did

Created a basic application that spawns an entity + child and immediately switches state.

What went wrong

• 0.16.0 no warning in logs
• Warning in logs about trying to despawn an entity that was already despawned.

Additional information

This is a minor annoyance for a minimal example, but makes logs very noisy when running with anything beyond a simple application e.g. a minimal bevy_new_2d app with the demo app deleted emits about 15 warnings to get to the gameplay state.

Related discussion #5617

Minimal repro

use bevy::prelude::*;

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .init_state::<AppState>() // Alternatively we could use .insert_state(AppState::Menu)
        .add_systems(Startup, setup)
        .add_systems(OnEnter(AppState::Menu), change_state)
        .run();
}

#[derive(Debug, Clone, Copy, Default, Eq, PartialEq, Hash, States)]
enum AppState {
    #[default]
    Menu,
    InGame,
}

fn setup(mut commands: Commands) {
    commands.spawn((
        Name::new("ME"),
        DespawnOnExitState(AppState::Menu),
        // StateScoped(AppState::Menu),
        children![Name::new("MY KID")],
    ));
}

fn change_state(mut next_state: ResMut<NextState<AppState>>) {
    info!("Going to game state");
    next_state.set(AppState::InGame);
}

Log With `0.16.1`

~/src/bevytest   main  cargo run
   Compiling bevytest v0.1.0 (/Users/will/src/bevytest)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 2.21s
     Running `target/debug/bevytest`
2025-06-22T06:05:34.794353Z  INFO bevy_diagnostic::system_information_diagnostics_plugin::internal: SystemInfo { os: "macOS 15.5 Sequoia", kernel: "24.5.0", cpu: "Apple M1", core_count: "8", memory: "8.0 GiB" }
2025-06-22T06:05:34.896192Z  INFO bevy_render::renderer: AdapterInfo { name: "Apple M1", vendor: 0, device: 0, device_type: IntegratedGpu, driver: "", driver_info: "", backend: Metal }
2025-06-22T06:05:35.403381Z  INFO bevy_render::batching::gpu_preprocessing: GPU preprocessing is fully supported on this device.
2025-06-22T06:05:35.441436Z  INFO bevy_winit::system: Creating new window App (0v1)
2025-06-22T06:05:37.125189Z  INFO bevytest: Going to game state

With c6ae964:

 ~/src/bevytest   main  cargo run
   Compiling bevytest v0.1.0 (/Users/will/src/bevytest)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 2.84s
     Running `target/debug/bevytest`
2025-06-22T06:11:17.177839Z  INFO bevy_diagnostic::system_information_diagnostics_plugin::internal: SystemInfo { os: "macOS 15.5 Sequoia", kernel: "24.5.0", cpu: "Apple M1", core_count: "8", memory: "8.0 GiB" }
2025-06-22T06:11:17.278648Z  INFO bevy_render::renderer: AdapterInfo { name: "Apple M1", vendor: 0, device: 0, device_type: IntegratedGpu, driver: "", driver_info: "", backend: Metal }
2025-06-22T06:11:17.630157Z  INFO bevy_render::batching::gpu_preprocessing: GPU preprocessing is fully supported on this device.
2025-06-22T06:11:17.673485Z  INFO bevy_winit::system: Creating new window bevytest (0v0)
2025-06-22T06:11:19.007887Z  INFO bevytest: Going to game state
2025-06-22T06:11:19.008034Z  WARN bevy_ecs::error::handler: Encountered an error in command `<bevy_ecs::system::commands::entity_command::remove<bevy_ecs::hierarchy::ChildOf>::{{closure}} as bevy_ecs::error::command_handling::CommandWithEntity<core::result::Result<(), bevy_ecs::world::error::EntityMutableFetchError>>>::with_entity::{{closure}}`: The entity with ID 15v0 does not exist (enable `track_location` feature for more details)

[Greatness7]

I've been seeing similar warning spams with just regular despawn() usage. These warnings only happen on current main and do not occur in the 0.16 release. In our app the millions of warnings is so extreme that the vscode terminal can't even handle it and the editor becomes unresponsive.

[brianreavis]

I also got hit by these noisy log messages and put up a fix here: #19718. Though, someone with more ECS knowledge should chime in on if this warning should be silenced – or if there's some broken/unexpected relations state that should fundamentally be fixed.