---
title: Deferred commands
description: Record structural changes inside systems and play them back at schedule barriers.
sidebar:
  order: 8
---

`scoped Commands` records structural operations in a system's private command buffer.

| Command | Behavior at playback |
| --- | --- |
| `Spawn<TBundle>(in bundle)` | Materializes the returned reserved entity handle with its bundle. |
| `Insert<T>(entity, in value)` | Adds or replaces one component. |
| `InsertBundle<TBundle>(entity, in bundle)` | Adds or replaces bundle members. |
| `Remove<T>(entity)` / `Despawn(entity)` | Performs a strict removal. Missing targets or components are errors. |
| `TryRemove<T>(entity)` / `TryDespawn(entity)` | Allows an absent target or component without an error. |

## Reserved handles

`Spawn` returns a reserved handle that can appear in later commands. It remains absent from queries until playback. Discarding an unmaterialized spawn invalidates its reservation.

## When commands become visible

Planner barriers join active workers, play buffers in stable plan order and local recording order, and refresh query caches. A dependent consumer observes its producer's commands, including transitive dependencies and skipped conditions. The schedule also flushes at completion.

## Failure

Playback stops at the first failure. Earlier effects remain. The unapplied suffix is discarded, and unmaterialized reservations are cancelled.

`CommandPlaybackException` identifies `Producer` and `CommandIndex`. Playback does not roll back or retry.