Bevy asset scenes (docs-first stub)
Not a full port. Levels are assets plus a Scene you spawn. They are not a packed Godot scene tree.
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:
AssetServeris the resource that loads from disk.AssetServer::loadreturns aHandleand does not reload while a strong handle still exists. Loaded data lives inAssets<T>.AssetServer::is_loaded_with_dependenciesis true when the asset and its dependencies are ready.LoadStateis 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::addinserts a procedural asset and does not deduplicate. - Hot reload: the
file_watcherCargo feature, andAssetPlugin'swatch_for_changes_overridefield, are the toggles named on the asset index. - Scenes:
bevy::scenedescribes aScene(entity, components, children, assets), built with thebsn!macro.World::spawn_sceneandCommands::spawn_scenespawn immediately and error if asset dependencies are not loaded.World::queue_spawn_sceneandCommands::queue_spawn_scenewait, then spawn in theSpawnSceneschedule betweenUpdateandPostUpdate. - Hierarchy in a scene:
Children [ ... ]insidebsn!. Separate sibling entities with--.#Nameassigns aNameinside that macro's scope.
Godot idea to Bevy idiom
| Idea | Bevy idiom (idea only) |
|---|---|
| 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 |
Gaps
.bsnasset files are described as future on the scene page. Do not invent a file loader for them.- A
DynamicScenetype was not on docs.rslatest(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 Do not cite it.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
AssetLoaderregistration (App::register_asset_loader) was named, not opened as a worked example.
Expert Knowledge Delta
Library target in prose: Bevy 0.20.0. Lattice URLs stay unversioned.
Opened canon only: Component, Resource, Query, Commands, Startup, Update, Fixed / FixedMain (bevy::time), .chain(), Plugin, DefaultPlugins, MinimalPlugins. Messages and observers are an ownership slot. This file does not invent their struct 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 this skill did not open | A Gaps row | A fabricated crate (solver, navmesh module, net, XR) |
Load references/a-gate-notes.md for the same table plus the gap rule.
NEVER
-
Do not put
/0.20.0/in lattice URLs. WHY: permalinks stay onlatest. The 0.20.0 pin belongs in prose once. -
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: those rows are gaps, blocked, or revisit.
-
No Godot packed-scene, node, or resource-loader types. WHY: a Godot port, an unopened API, or a public lie fails the docs-first bar.
-
No scene format this file did not open. WHY: a Godot port, an unopened API, or a public lie fails the docs-first bar.
-
No third-party scene crates. WHY: a Godot port, an unopened API, or a public lie fails the docs-first bar.
-
No Creation Station content. WHY: a Godot port, an unopened API, or a public lie fails the docs-first bar.
-
No umbrella skill over Godot and Bevy. WHY: a Godot port, an unopened API, or a public lie fails the docs-first bar.
-
Do not mark this row
ported. It isdocs_mapped. WHY: a Godot port, an unopened API, or a public lie fails the docs-first bar.
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
latestbranch.
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 are a separate gap from scene spawn.
- godot-scene-management - Godot counterpart. Source idea only.
Downstream / consumers
- bevy-camera-systems - Camera entities a scene may spawn.
Master
- bevy-master - Bevy router.


