1. A computer-implemented method comprising: receiving a request for streaming media from a client device; detecting, in the request for streaming media, a flag from the client device specifying a supplemental content restriction mode for the client device; receiving, from a supplemental content application, a supplemental content item for inclusion in a stream of media items to be delivered to the client device; and based on the flag, creating a shell of the supplemental content item that identifies the supplemental content item, inserting the shell in the stream of media items to be delivered to the client device, and delivering the stream of media items to the client device including the shell, and wherein the shell is configured to cause the client device to report a presentation event of the supplemental content item when the shell is detected in the stream of media items during playback at the client device without interrupting playback of the stream of media items at the client device.