Bevy asset scenes

When to use

Load this when content comes from disk or a scene description should spawn entities. bevy::asset and bevy::scene on docs.rs latest (0.20.0) are the sources.

ECS shape

• Assets: AssetServer is the resource that loads from disk. AssetServer::load returns a Handle and does not reload while a strong handle still exists. Loaded data lives in Assets<T>. AssetServer::is_loaded_with_dependencies is true when the asset and its dependencies are ready. LoadState is the status type named on that page.
• Handles: strong handles are reference counted. Dropping the last strong handle removes the asset. Weak handles do not keep it alive. Assets::add inserts a procedural asset and does not deduplicate.
• Hot reload: the file_watcher Cargo feature, and AssetPlugin's watch_for_changes_override field, are the toggles named on the asset index.
• Scenes: bevy::scene describes a Scene (entity, components, children, assets), built with the bsn! macro. World::spawn_scene and Commands::spawn_scene spawn immediately and error if asset dependencies are not loaded. World::queue_spawn_scene and Commands::queue_spawn_scene wait, then spawn in the SpawnScene schedule between Update and PostUpdate.
• Hierarchy in a scene: Children [ ... ] inside bsn!. Separate sibling entities with --. #Name assigns a Name inside that macro's scope.

Coming from Godot

Godot idea	Bevy idiom
Load a file	AssetServer::load → Handle
Wait until ready	is_loaded_with_dependencies before a state change
Instance a packed scene	spawn_scene or queue_spawn_scene around a Scene
Child nodes in that scene	Children inside bsn!
Change one entity's mesh	Swap the Handle on the component that stores it

Scope

• .bsn asset files are described as future on the scene page. Do not invent a file loader for them.
• A DynamicScene type was not on docs.rs latest (the struct URL 404'd on 2026-10-11). Do not cite it.
• Scene change as "free the old level, then spawn the next" is a design note. No level-switch API was opened.
• Custom AssetLoader registration is named as App::register_asset_loader. Check the asset docs for a worked example before writing one.

Expert Knowledge Delta

Target: Bevy 0.20+.

Core ECS types: Component, Resource, Query, Commands, Startup, Update, Fixed / FixedMain (bevy::time), .chain(), Plugin, DefaultPlugins, MinimalPlugins. Messages and observers are an ownership slot. See bevy-events-messaging for their APIs. Systems run in parallel unless .chain() orders the ones that conflict.

Who owns state

Piece	Owner	Who may mutate	Schedule
Data on one entity	Component	One system via Query	Update or FixedMain
One value for the whole app	Resource	One system	Startup to insert, then the schedule that reads it
Spawn	Commands	The spawning system	Startup for the initial world; later schedules for runtime spawn
Order that must not race	.chain()	The chained systems only	Same schedule
Plugin boundary	Plugin	build registers systems and resources	Before the app runs

Borrow rule: two systems that both mutably query the same component must be ordered (.chain()) or split so only one writes. Unrelated systems stay parallel. That is the ECS page rule, not a guess at a system-set API.

Decision

If you need	Do this	Do not
Per-entity data	Component + Query	A Godot node script
App-wide config or clock	Resource	Copy the value onto every entity
Stable simulation step	FixedMain and the Fixed clock	Tie simulation to raw frame Update
Startup spawn	Commands in Startup	Spawn from a render system
Cross-system notice that is not shared state	Message or observer slot in bevy-events-messaging	A new event type invented in this file
An API outside the documented set	Check the official docs first	A made-up crate or API

Load references/ecs-ownership.md for the ownership table.

NEVER

• Do not pin /0.20.0/ in docs URLs. WHY: links stay on latest; the 0.20 target is stated once in prose.

• Do not mutably query the same component from two unordered systems. WHY: the schedule runs systems in parallel unless .chain() orders them.

• Do not invent a physics, navigation, networking, or XR crate here. WHY: this skill only names documented Bevy crates and modules.

• No Godot packed-scene, node, or resource-loader types. WHY: Bevy code stays idiomatic ECS and uses only documented Bevy APIs.

• No scene format this file did not open. WHY: Bevy code stays idiomatic ECS and uses only documented Bevy APIs.

• No third-party scene crates. WHY: Bevy code stays idiomatic ECS and uses only documented Bevy APIs.

Reference

docs.rs links use the unversioned latest permalink. The library pin on bevy-master stays 0.20.0.

Official Documentation

• Migration guides - Unversioned hop index.
• bevy crate - Unversioned API index.
• bevy::asset - AssetServer, Handle, Assets<T>, load state, hot reload.
• bevy::scene - Scene, bsn!, spawn_scene, queue_spawn_scene, SpawnScene.
• Assets - Official asset catalog.
• Examples - Example tree on the latest branch.

Related Skills

Prerequisites

• bevy-master - Who owns which piece of state.
• bevy-project-foundations - Cargo features, including asset watcher flags.
• bevy-state-machines - The asset page points at app states for load gates.

Complements

• bevy-audio-systems - Clips loaded through AssetServer.
• bevy-save-load - Player saves, separate from scene spawn.
• godot-scene-management - Equivalent Godot skill.

Downstream / consumers

• bevy-camera-systems - Camera entities a scene may spawn.

Master

• bevy-master - Bevy router.