I am seeing exactly the same. I have a 'LazyVStack' enclosed in a 'ScrollView', in which I can be displaying thousands of elements. Definite slow down. I've pulled my code apart and still can't get an improvement.

Hey, Thank you! Phil

Thank you! I have a few clarifying questions: When in kinematic mode is the ModelEntity ignored for collision detection? When I add an entity to RealityView's content, via .add() what Anchor does this attach it to? If I have an anchor with multiple ModelEntities attached, they each have to be added to the content to be picked up by the physics engine? But when I do this, they ignore the anchor's translation and default to the world view. And finally, when simulating something like a bullet/arrow, is it better to use a TriggerVolume component for efficiency?

I have worked out the issue. On iOS one needs to set up an NSMetadataQuery in addition to using a NSFilePresenter. Something like: let metadataQuery = NSMetadataQuery() metadataQuery.notificationBatchingInterval = 1 metadataQuery.searchScopes = [NSMetadataQueryUbiquitousDocumentsScope] metadataQuery.predicate = NSPredicate(format: "%K LIKE %@", NSMetadataItemFSNameKey, "*.txt") metadataQuery.start() And then establish a process to listen for changes. For example using Combine: NotificationCenter.default.publisher(for: .NSMetadataQueryDidUpdate) .receive(on: DispatchQueue.main) .sink { [weak self] notification in guard let self = self else { return } self.metadataQuery.stop() for resultSets in 0..<self.metadataQuery.resultCount { if let resultSet = self.metadataQuery.result(at: resultSets) as? NSMetadataItem { /// DO YOUR MAGIC HERE... } } self.metadataQuery.start() } .store(in: &backgroundProcesses)

OK - my bad! I set-up a separate project, away from my main code base that test running multiple FileManager enumerations in parallel (using Tasks) and it all worked...couldn't provoke it no matter how hard I prodded it. And then my eyes flicked back to my main code and a small dim light bulb in my head went on....four hours later I've tracked down a somewhat subtle bug in my code. thank you for your responses!