Microsoft is trialing a tweaked Xbox Cloud Gaming model. For now, Xbox Insider participants can stream certain games from their digital library for free — no Xbox Game Pass Ultimate subscription needed — but the price is ads. Sessions are limited to 60 min; when the hour is up the session ends, although you can simply restart the game.
Microsoft stresses that ad breaks show up while you wait in the queue before launch, not during play (i.e., banners or video spots won't interrupt an active session). The free access applies to select purchased titles in your personal library and supported free-to-play games — e.g., it does not unlock the entire Game Pass catalog. Paid Game Pass Ultimate members won't see changes; their experience remains the same and without ad inserts.
This is a limited insider test. Microsoft hasn't given a timeline for a broader public release, so treat it as an experiment rather than a finished product.