Microsoft announced Project Solara at Build today. They’ve got a couple prototypes, including a clever badge-style device, and thoughts on UI:

We are also investing in just-in-time UI: the ability for an agent experience to adapt across devices and modalities without requiring developers to redesign everything for every new form factor. Today, that means semi-structured approaches like adaptive cards and known content types. Over time, it moves toward more dynamic and generative interfaces.