API stability

Estella is pre-1.0, and not all of its API is equally settled. Rather than ask you to guess which parts are, every exported symbol carries exactly one stability tier as a JSDoc tag on its declaration — so it ships in the .d.ts your project compiles against, and your editor shows it when you hover.

Tier	Tag	What it promises
Stable Candidate	`@public`	We expect 1.0 not to break it. Removing or changing one takes a deprecation release first.
Beta	`@beta`	Shipping and supported; the shape may still adjust before 1.0.
Experimental	`@experimental`	No compatibility claim. It may change or disappear in any release.
Internal	`@internal`	Not for you to depend on. It is a build error for one to be exported at all.

There is no stable-by-default. An untagged symbol is Experimental, so freezing an API is something we decide, never something we forget to prevent.

A symbol only reaches Stable Candidate once three things are true: it is documented, a test pins its behaviour, and one of the games we certify releases against actually calls it. That bar is a build gate, not a habit — and so is the promise itself, which is compared against the previous release tag on every push.

The full list below is generated from the same snapshots the guards read.

113Stable Candidate

73Beta

1562Experimental

1748 exported symbols in total. Experimental is the default: a symbol reaches a stronger tier only when someone decides it has, so this page grows one deliberate step at a time.

By subsystem

The same answer at the size you build in. Every verdict here is held against the tags its entry symbols carry, so this table cannot quietly disagree with them.

Subsystem	Tier	Why
ECS	Stable Candidate	Frozen — the bar it had to clear is below.
App lifecycle	Stable Candidate	Frozen — the bar it had to clear is below.
Transform & hierarchy	Stable Candidate	Frozen — the bar it had to clear is below.
Sprites & text	Stable Candidate	Frozen — the bar it had to clear is below.
Input actions	Stable Candidate	the action and binding vocabulary is frozen; the raw per-frame state under it is Beta — see InputState
Layout units	Stable Candidate	Frozen — the bar it had to clear is below.
Raw input state	Beta	per-frame touch state is reachable only as raw collections, with no accessor for started/ended and no write door — freezing it would freeze both gaps
UI	Beta	thirty-three of a hundred and fifteen UI symbols reach a certified game, and the newest part of the surface is the part a creator meets first — anchors, insets, theme tokens
Scenes	Beta	one certified project drives scenes at all, against twenty-six SceneManagerState signatures
Prefabs	Beta	instantiate has not moved, but its result and override shapes are the on-disk format's, so the names settled ahead of the shapes
Assets	Beta	one certified project takes Res(Assets), for four of its members, and the host wiring — resolvers, registries, the manifest, device-loss recovery — has to leave the game-facing surface first
Physics	Beta	the corpus reaches three of thirty-seven physics symbols
Camera	Beta	clearFlags is a bitmask whose C++ enum has no TypeScript spelling, and cullingMask names layers no exported constant identifies — two fields typed `number` for want of the vocabulary
Spine	Beta	one certified project plays a skeleton; the runtime is a side module a project opts into
Audio	Beta	a certified run drives a loop and reads the master bus analyser, so a break is noticed — but the corpus reaches a handful of twenty-three audio symbols
Animation & timeline	Beta	sprite-animation now certifies it end to end, but the corpus reaches two of eighty animation symbols and the timeline half of them is untouched
Tilemap	Experimental	certified end to end by two games, but the runtime surface has not been read for a tier yet
Particles	Experimental	as tilemap — exercised by a certified game, not yet read for a tier
Video	Experimental	the platform paths differ enough that the surface is still converging
AI — navigation, FSM, behaviour trees	Experimental	deliberately after the rest: 0.50 freezes what a game is built OUT of, and the layers built ON that come once those are settled
Networking & replication	Experimental	as AI — the high-level layer waits on the layers under it
Materials, lighting, post-processing	Experimental	as AI — and the render graph behind it is still moving

Stable Candidate

We expect 1.0 not to break these. Each one is documented, pinned by a test, and used by a game we certify releases against; changing or removing one takes a deprecation release first.

Symbol	Kind
`ActionDef`	interface
`ActionType`	type
`AddedWrapper`	interface
`AnyComponentDef`	type
`AssetFieldMeta`	interface
`AssetFieldType`	type
`AssetRef`	interface
`Axis1D`	const
`Axis2D`	const
`Binding`	type
`BuiltinComponentDef`	interface
`Button`	const
`ChangedWrapper`	interface
`Children`	const
`ChildrenData`	interface
`Color`	interface
`Commands`	function
`CommandsDescriptor`	interface
`CommandsInstance`	class
`ComponentData`	type
`ComponentDef`	interface
`ComponentMetadata`	interface
`ComponentsData`	type
`Dimension`	interface
`DimensionUnit`	type
`Entity`	type
`EntityCommands`	class
`EventDef`	interface
`EventReader`	function
`EventReaderDescriptor`	interface
`EventReaderInstance`	class
`EventWriter`	function
`EventWriterDescriptor`	interface
`EventWriterInstance`	class
`FieldMeta`	interface
`FilterExpr`	type
`GamepadAxis`	enum
`GamepadButton`	enum
`GetWorld`	function
`GetWorldDescriptor`	interface
`GpAxis`	const
`GpButton`	const
`InferParam`	type
`InferParams`	type
`InputMap`	class
`InputMapAsset`	interface
`Key`	const
`Keys1D`	const
`Keys2D`	const
`ListenOptions`	interface
`MouseButton`	const
`Mut`	function
`MutWrapper`	interface
`Name`	const
`NameData`	interface
`Parent`	const
`ParentData`	interface
`Quat`	interface
`Query`	function
`QueryArg`	type
`QueryBuilder`	interface
`QueryDescriptor`	interface
`QueryInstance`	class
`QueryResult`	type
`RemovedQueryDescriptor`	interface
`RemovedQueryInstance`	class
`Res`	function
`ResDescriptor`	interface
`ResMut`	function
`ResMutDescriptor`	interface
`ResMutInstance`	class
`ResourceDef`	interface
`RunCondition`	type
`RuntimeOnly`	const
`Schedule`	enum
`SkeletalFieldMeta`	interface
`Sprite`	const
`SpriteData`	interface
`Stick`	const
`SystemDef`	interface
`SystemOptions`	interface
`SystemParam`	type
`SystemSet`	interface
`SystemSetOptions`	interface
`SystemTouches`	interface
`Text`	const
`TextAlign`	type
`TextData`	interface
`TextOverflow`	type
`TextRenderMode`	type
`TextVerticalAlign`	type
`Time`	const
`TimeData`	interface
`Transform`	const
`TransformData`	interface
`UnwrapQueryArg`	type
`Vec2`	interface
`Vec3`	interface
`Vec4`	interface
`Virtual`	const
`World`	class
`addStartupSystem`	function
`addSystemSetToSchedule`	function
`addSystemToSchedule`	function
`defineComponent`	function
`defineEvent`	function
`defineInputMap`	function
`defineResource`	function
`defineSystem`	function
`defineSystemSet`	function
`defineTag`	function
`percent`	const
`px`	const

Beta

Shipping and supported, but the shape may still adjust before 1.0. Build on them; expect to read the changelog.

Symbol	Kind
`Animator`	const
`Assets`	const
`AssetsData`	type
`Audio`	const
`Camera`	const
`CameraData`	interface
`CameraFields`	interface
`CameraTransformFields`	interface
`CharacterController`	const
`CharacterController3D`	const
`ConvexCollider3D`	const
`DistanceJoint3D`	const
`FixedJoint3D`	const
`GraphNodeType`	type
`GraphType`	type
`HingeJoint3D`	const
`Input`	const
`InputState`	class
`InstantiatePrefabResult`	interface
`MaterialGraph`	interface
`MaterialGraphNode`	interface
`MeshCollider3D`	const
`NODE_SPECS`	const
`NativeBridge`	interface
`NativeFetchResult`	interface
`NativeInputListener`	interface
`NativePlatformAdapter`	class
`NodeParamSpec`	interface
`NodePort`	interface
`NodeSpec`	interface
`Physics`	const
`PhysicsEvents`	const
`PointJoint3D`	const
`PrefabOverride`	interface
`PrefabServer`	class
`Prefabs`	const
`SceneConfig`	interface
`SceneContext`	interface
`SceneLoadProgressCallback`	type
`SceneManager`	const
`SceneManagerState`	class
`SceneStatus`	type
`SliderJoint3D`	const
`SpawnOverride`	type
`Spine`	const
`SpineAnimation`	const
`SpriteAnimator`	const
`ThemeColors`	interface
`TouchPoint`	interface
`TransitionConfig`	interface
`TransitionOptions`	interface
`UICameraData`	interface
`UICameraInfo`	const
`UINode`	const
`UIVisual`	const
`acquireWebGPUDevice`	function
`addNode`	function
`cameraFrustumCorners`	function
`captureFramePixels`	function
`compileMaterialGraph`	function
`connect`	function
`createHeadlessApp`	function
`disconnect`	function
`installNativePlatform`	function
`loadEsengineModule`	function
`moveNode`	function
`newMaterialGraph`	function
`nodeAdapter`	const
`removeNode`	function
`runHeadless`	function
`spawnUIEntity`	function
`themeColors`	function
`transitionTo`	function

Experimental

Everything else, which is most of the surface. It works and it is what the editor itself is built on, but no compatibility claim is attached: it may change or disappear in any release. Your editor shows the tier on hover, and sdk/etc/*.api.md in the repository is the full inventory.

What this does not cover

The tiers above describe the TypeScript API. Estella’s 1.0 promise also covers the project and asset formats, the WASM runtime contract, and the documented build CLI — see Versioning Policy for what a breaking change means for each.