A content management system may maintain a scene description that represents a 3D virtual environment and a publish/subscribe model in which clients subscribe to content items that correspond to respective portions of the shared scene description. When changes are made to content, the changes may be served to subscribing clients. Rather than transferring entire descriptions of assets to propagate changes, differences between versions of content may be exchanged, which may be used construct updated versions of the content. Portions of scene description may reference other content items and clients may determine whether to request and load these content items for lazy loading. Content items may be identified by Uniform Resource Identifiers (URIs) used to reference the content items. The content management system may maintain states for client connections including for authentication, for the set of subscriptions in the publish/subscribe model, and for their corresponding version identifiers.