bevyengine/bevy · error · QueryEntityError

The entity with ID {0} was requested mutably more than once

Error message

The entity with ID {0} was requested mutably more than once

What it means

thiserror Display for QueryEntityError::AliasedMutability: Query::get_many_mut (or similar batched mutable access) received the same Entity more than once in its list. Two &mut bindings to one entity would alias mutable borrows, so the API validates for duplicates and reports the offending id.

Source

Thrown at crates/bevy_ecs/src/query/error.rs:23

    entity::{Entity, EntityNotSpawnedError},
};

/// An error that occurs when retrieving a specific [`Entity`]'s query result from [`Query`](crate::system::Query) or [`QueryState`](crate::query::QueryState).
// TODO: return the type_name as part of this error
#[derive(thiserror::Error, Clone, Copy, Debug, PartialEq, Eq)]
pub enum QueryEntityError {
    /// The given [`Entity`]'s components do not match the query.
    ///
    /// Either it does not have a requested component, or it has a component which the query filters out.
    #[error("The query does not match entity {0}")]
    QueryDoesNotMatch(Entity, ArchetypeId),
    /// The given [`Entity`] is not spawned.
    #[error("{0}")]
    NotSpawned(#[from] EntityNotSpawnedError),
    /// The [`Entity`] was requested mutably more than once.
    ///
    /// See [`Query::get_many_mut`](crate::system::Query::get_many_mut) for an example.
    #[error("The entity with ID {0} was requested mutably more than once")]
    AliasedMutability(Entity),
}

/// An error that occurs when evaluating a [`Query`](crate::system::Query) or [`QueryState`](crate::query::QueryState) as a single expected result via
/// [`single`](crate::system::Query::single) or [`single_mut`](crate::system::Query::single_mut).
#[derive(Debug, thiserror::Error)]
pub enum QuerySingleError {
    /// No entity fits the query.
    #[error("No entities fit the query {0}")]
    NoEntities(DebugName),
    /// Multiple entities fit the query.
    #[error("Multiple entities fit the query {0}")]
    MultipleEntities(DebugName),
}

/// An error that occurs when creating a contiguous iterator from a non-dense [`Query`](crate::system::Query) or [`QueryState`](crate::query::QueryState) via
/// [`contiguous_iter`](crate::system::Query::contiguous_iter) or [`contiguous_iter_mut`](crate::system::Query::contiguous_iter_mut).
#[derive(Debug, thiserror::Error)]

View on GitHub (pinned to 396ca72708)

Solutions

  1. Deduplicate the entity list before calling get_many_mut
  2. Split overlapping entities into sequential get_mut calls
  3. Use a ParamSet or iter().find() pattern when the set of entities is not known disjoint
Defensive patterns

Strategy: validation

When it happens

Trigger: Thrown at crates/bevy_ecs/src/query/error.rs:23 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/c82328006b963f6f. Report an issue: GitHub.