While trying to reproduce https://forum.unity.com/threads/0-2...not-pick-up-physicsvelocity-component.809211/ in a minimal case, I noticed that BuildPhysicsWorld processes two cubes when I put one in the Convert To Client Server Entity. The project is a fresh URP project with NetCode and Unity Physics installed. In the scene, there is a Networking (Convert To Client Server Entity), and a Cube and GhostCollection as children. The cube has a Ghost Authoring Component and the GhostCollection has it in its list. Here is the cube: I expected there to be only one cube in the Server World as a result, but: The first cube (2) is probably the cube that is sitting in the GhostPrefabBuffer. This one is also processed by the BuildPhysicsWorld system: I assume cube (2) should not be processed by the BuildPhysicsWorld system, and only the one that is actually "in the world" (not in the GhostPrefabBuffer) should be processed, e.g. falling down etc. By the looks of it, however, both are processed by the BuildPhysicsWorld system. One thing I am wondering about: Should the GhostPrefabBuffer etc. be in another world and only when prefabs are spawned into the Server World should it be used to spawn new entities into the Server World? Many thanks in advance!