bevyengine/bevy · error · RegisteredSystemError

Could not get system from `{}`, entity was `SystemId<{}, {}>

Error message

Could not get system from `{}`, entity was `SystemId<{}, {}>`

What it means

RegisteredSystemError (get_system-style lookup failure): the given SystemId entity exists but a system of the expected type could not be retrieved from it — typically the entity is not a registered system entity or holds a differently-typed system.

Source

Thrown at crates/bevy_ecs/src/system/system_registry.rs:866

    ///
    /// 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),
        }
    }
}

impl<I: SystemInput, O> core::fmt::Debug for RegisteredSystemError<I, O> {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {

View on GitHub (pinned to 396ca72708)

Solutions

1. Verify the SystemId was produced by registering a system with matching input/output types
2. Do not reuse arbitrary entities as SystemIds
3. Re-register the system with the correct I/O types and use the new id

When it happens

Trigger: Thrown at crates/bevy_ecs/src/system/system_registry.rs:866 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/4e8384580f9ba1ef. Report an issue: GitHub.