XLab Private Engine Runtime

Private compiler, registry, lifecycle, motion-reference, and runtime bridge implementation used by task packages and native simulator backends. Public declarations live in the separately published xlab-api distribution. Importing xlab_engine does not import Isaac Sim, Isaac Lab, MJLab, MuJoCo, or Warp.

Native backend implementations are installed separately. Task declarations should import schemas from xlab_api; executable task code may depend on this private runtime rather than importing a simulator SDK.

External packages extend the boundary through Python entry points:

• xlab.engines registers an independently installed backend.
• xlab.assets registers an engine-neutral asset package resolver.
• xlab.asset_catalogs registers all asset packages owned by one application.
• xlab.actuators registers engine-scoped native actuator models and optional SDK-free asset layout compilers.
• xlab.engine_terms registers native term lowering under an <engine>.<extension> name.
• xlab.terrains registers whole-terrain and generated-tile builders.

The XLab application wheel publishes stable aggregate entry points: one asset catalog, one terrain registrar, and one actuator registrar per engine. Its setup.py obtains this fixed metadata from the dependency-free application_entry_points() helper. Concrete application assets are discovered by the catalog, terrain kinds belong to the terrain aggregate registrar, and actuator models belong to ACTUATOR_DECLARATIONS; adding any of them does not change setup.py. Independently distributed wheels may continue to publish the family entry points above directly.

New assets describe motor facts with ActuationSpec, ActuatorProfile, and ActuatorBinding. The selected model's layout compiler maps those facts to backend-native topology and returns CompiledActuatorGroup; SDK construction remains a later step. state_group denotes shared actuator state, not required native grouping. NativeActuatorGroup remains the compatibility surface for existing native asset API 0.1 providers and is not the preferred authoring API.