Hi Quinn, I tested both locations with synthetic PNGs on macOS 26.6.2 (25G83), using Preview 11.0 (1113.5.3). A used FileManager.default.temporaryDirectory. B used FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: true). I confirmed that B resolved to the app container's Documents directory, not the user's ordinary Documents folder. Both cases used the same Apple Development-signed sandboxed app, identical initial PNG bytes, atomic writing, and the same NSWorkspace open call. The storage root, distinguishing A/B filename labels, and creation times differed. For each PNG, I selected Rotate Left once in Preview without pressing Command-S, waited at least 10 seconds, and inspected the original file. In both cases, Preview changed the document title to a copy. Both originals remained 640 × 360 pixels and 10,684 bytes, with unchanged SHA-256 and modification timestamps. When closing B, Preview asked whether to keep the new copy and stated that the original document would not be changed. I cancelled without saving a separate copy. The signed app has these three entitlements, all set to true: com.apple.security.app-sandbox com.apple.security.files.user-selected.read-write com.apple.security.files.bookmarks.app-scope Moving the PNG to the container's Documents directory did not change the observed behavior. What would you recommend checking next? Thank you!

Hi Quinn, Thank you for looking into this. It is A: FileManager.default.temporaryDirectory. The app creates a subdirectory beneath the URL returned by that API: FileManager.default.temporaryDirectory .appendingPathComponent("ShelfDragPoC/Captures", isDirectory: true)The captured image is saved as a PNG using Data.write(to:options: .atomic), and the resulting URL is passed to Preview via NSWorkspace.open(_:withApplicationAt:configuration:completionHandler:). The minimal reproduction project uses the same API and write method, with a different subdirectory (PreviewSandboxRepro/Captures) and a synthetic PNG. Neither implementation explicitly calls NSTemporaryDirectory() or uses a separately chosen temporary-directory root. Thank you!