bevyengine/bevy · error · RegisteredSystemError

System returned error: {0}

Error message

System returned error: {0}

What it means

RegisteredSystemError::SystemError: the stored system ran but returned an error from its In/Out pipe (e.g. an Infallible/Result-returning system propagated a failure), wrapping the original error.

Source

Thrown at crates/bevy_ecs/src/system/system_registry.rs:863

    #[error("System {0:?} was not registered")]
    SystemIdNotRegistered(SystemId<I, O>),
    /// A cached system was removed by value, but no system with its type was found.
    ///
    /// Did you forget to register it?
    #[error("Cached system was not found")]
    SystemNotCached,
    /// The `RegisteredSystem` component is missing.
    #[error("System {0:?} does not have a RegisteredSystem component. This only happens if app code removed the component.")]
    MissingRegisteredSystemComponent(SystemId<I, O>),
    /// A system tried to remove itself.
    #[error("System {0:?} tried to remove itself")]
    SelfRemove(SystemId<I, O>),
    /// System could not be run due to parameters that failed validation.
    /// This is not considered an error.
    #[error("System did not run due to failed parameter validation: {0}")]
    Skipped(SystemParamValidationError),
    /// System returned an error or failed required parameter validation.
    #[error("System returned error: {0}")]
    Failed(BevyError),
    /// [`SystemId`] had different input and/or output types than [`SystemIdMarker`]
    #[error("Could not get system from `{}`, entity was `SystemId<{}, {}>`", DebugName::type_name::<SystemId<I, O>>(), .1.input_type_id.name, .1.output_type_id.name)]
    IncorrectType(SystemId<I, O>, SystemIdMarker),
    /// System is not present in the `RegisteredSystem` component.
    // TODO: We should consider using catch_unwind to protect against the panic case.
    #[error("The system is not present in the RegisteredSystem component. This can happen if the system was called recursively or if the system panicked on the last run.")]
    SystemMissing(SystemId<I, O>),
}

impl<I: SystemInput, O> From<RunSystemError> for RegisteredSystemError<I, O> {
    fn from(value: RunSystemError) -> Self {
        match value {
            RunSystemError::Skipped(err) => Self::Skipped(err),
            RunSystemError::Failed(err) => Self::Failed(err),
        }
    }
}

View on GitHub (pinned to 396ca72708)

Solutions

1. Inspect the wrapped error to find the underlying cause
2. Handle the failure at the call site of run_system_with instead of letting the system return Err
3. Make the system itself handle or log the error before returning

When it happens

Trigger: Thrown at crates/bevy_ecs/src/system/system_registry.rs:863 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/01820c30eca5babb. Report an issue: GitHub.