It looks like in iOS 18, there is a new option in Files to "Keep Downloaded". I.e., mark a file to be downloaded and never evicted. Is there an API that would allow us to provide this feature in our app?
Our app stores files in a ubiquitous container and displays them in a custom UI (not a UIDocumentBrowserViewController). We've had a longstanding request from users that they be able to mark a file as always available locally, so that they can make sure they have access to it even if they go offline. We've done a hacky, best-effort implementation of this, but there is no truly reliable way to achieve this through the existing APIs.