What's the recommended way to detect that the app is running on an iPhone Duo?

When the inner camera is in use and the reserved region becomes active, what is the recommended way for apps to adapt their UI? Should content move out of the reserved region where possible, or is it generally acceptable to leave content behind it? More specifically, how should apps handle content that can’t easily move aside, such as a long navigation title directly behind the reserved region? Should it be truncated, moved below the region, or handled another way?

When the user transitions from an open to a partially folded state, the system detects this is the final state after some delay and un-blurs the left side. The UI should now adapt to this state. For example, split view controller enlarges the sidebar to occupy the full width of the left side. What’s the best trigger to use for a custom view controller that wants to achieve a similar result? Is it the folding region becoming active?

Can an iPhone-only app that fully supports iPhone Duo, but is not otherwise optimized for iPad (and is non-universal), opt out of free-form resizing on iPad?

I’m trying to understand what guarantees CSSearchableIndex batching provides. beginBatch() // submit changes to searchable items (add/update/delete) endBatch(withClientState: newState) Two questions: 1. Persistence before endBatch If the app crashes after submitting changes to searchable items, but before calling endBatch, are those changes guaranteed not to be persisted? If the answer is yes, then the follow-up question is: 2. Atomicity of endBatch When endBatch(withClientState:) succeeds, is the batch atomic with respect to all submitted item changes, and the new client state? In other words, is it guaranteed that: either all submitted item changes and the new client state are persisted, or neither is persisted? Or is there any internal failure scenario in which the batch is only partially persisted – for example, some or all of the item changes persisted, but without the corresponding client state?