Nick
You're experiencing this with Actions Builder?
kkocel is correct there is no inherent user identifier but you can generate one and place it in [user storage](https://developers.google.com/assistant/conversational/storage-user).
It should appear in the `Authorization` request header.
Is there a strict need for the user to be unable to seek? Potentially you can use a livestream of an mp3 rather than a static media file, which would...
From my understanding sending a standard media file will always show seeking.
TuneIn to my knowledge actually streams radio live.
What developer support are you looking for?
I've filed a ticket internally.
I don't have an update to share.
Is it just in the simulator or does it happen on devices as well?