I am experiencing the exact same issue. Thanks for posting here — at least it feels a little better knowing it's not just me. I also saw this behaviour in Xcode 15.0 Beta 8, but not one of the much earlier betas. Just trying Beta 7 now. Is there any kind of work-around?

Unfortunately I can't remember which previous beta I used which successfully notarised; now I'm wondering if I imagined it and my last notarisation was in Xcode 14. I have just spent the afternoon trying every successive earlier version back to beta 1 and all exhibit the same issue. I then went to 14.3.1 and it also failed! But at least it gave an obscure error, which led me to this. So I went to https://developer.apple.com/account and found a message: "The program license agreement has been updated." I clicked accept, and tada... now it notarises just fine, even in 15.0.0 RC. How utterly infuriating. Apple, where do I send the bill for an hour of my time? Ha.

Thanks Ziqiao, I'm not talking about the "Remove Downloaded" feature, but it's definitely something very similar. In the problem scenario, the files are stored in ~/Documents/x and if the users' hard drives get too full, macOS is moving those documents to iCloud automatically, thereby triggering the FileWatcher* to say they've been removed. I believe that behind-the-scenes "Optimise Mac Storage" almost certainly uses the same mechanism as the "Remove Downloaded" feature you mentioned (ie 'dataless files") which I'd never heard of till now. Your tech note link gave me some good keywords for further research. If it's true I'm dealing with a dataless file issue, when FileWatcher says a file was deleted can I simply ask fileExists(atPath:) to see if it's actually still there or not? I think a dataless file will still return true for a fileExists call, despite being offloaded? * FileWatcher is just using FSEvents, I believe. Pertinent code is here.