bevyengine/bevy · error

Error adding plugin {plugin_name}: : plugin was already adde

Error message

Error adding plugin {plugin_name}: : plugin was already added in application

What it means

Panics in the Plugins::add_to_app implementation for a single Plugin when App::add_boxed_plugin returns AppError::DuplicatePlugin: the exact plugin type has already been added to this App before. Bevy refuses to add the same plugin type twice to keep build logic idempotent.

Source

Thrown at crates/bevy_app/src/plugin.rs:150

    use variadics_please::all_tuples;

    use crate::{App, AppError, Plugin, PluginGroup};

    pub trait Plugins<Marker> {
        fn add_to_app(self, app: &mut App);
    }

    pub struct PluginMarker;
    pub struct PluginGroupMarker;
    pub struct PluginsTupleMarker;

    impl<P: Plugin> Plugins<PluginMarker> for P {
        #[track_caller]
        fn add_to_app(self, app: &mut App) {
            if let Err(AppError::DuplicatePlugin { plugin_name }) =
                app.add_boxed_plugin(Box::new(self))
            {
                panic!(
                    "Error adding plugin {plugin_name}: : plugin was already added in application"
                )
            }
        }
    }

    impl<P: PluginGroup> Plugins<PluginGroupMarker> for P {
        #[track_caller]
        fn add_to_app(self, app: &mut App) {
            self.build().finish(app);
        }
    }

    macro_rules! impl_plugins_tuples {
        ($(#[$meta:meta])* $(($param: ident, $plugins: ident)),*) => {
            $(#[$meta])*
            impl<$($param, $plugins),*> Plugins<(PluginsTupleMarker, $($param,)*)> for ($($plugins,)*)
            where

View on GitHub (pinned to 396ca72708)

Solutions

1. Remove the duplicate app.add_plugin(...) / app.add_plugins(...) call for the same plugin type
2. Check whether the plugin is already included via a PluginGroup (e.g. DefaultPlugins) before adding it manually
3. If conditional, guard the addition with a check of the plugin registry or use feature gates to avoid double registration

When it happens

Trigger: Thrown at crates/bevy_app/src/plugin.rs:150 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of bevyengine/bevy@396ca72708 (2026-08-20). Data as JSON: /api/errors/aeb31434e613b37b. Report an issue: GitHub.