In our game app, we have screens before/after game levels which are transparent wk webviews. This works great. We have interesting, complex css-based animations. We recently added some Lottie animations, which use a javascript fetch() on a .json file, and that throws a CORS error since you can't normally fetch file:// urls from the app bundle.  The error is eliminated if we set allowFileAccessFromFileURLs to true, but it's an undocumented preference of webkit (not a secret iOS method). It's clearly included in the public WebKit github (in WKPreferences.mm). We have other ideas for workaround, such as JS injection.  Is allowFileAccessFromFileURLs OK to set to TRUE?  Is it a risk of app rejection, and/or a significant risk of being removed int he future, and/or and otherwise bad idea? Do you have any other tips about loading data into web views in-app?

After combing the forums and release nodes, here are some extra notes to help other developers using Apple-Hosted Background Assets. I don't promise I got this perfect, but it may help direct you. AssetPack.Status is an OptionSet (not an enum!) - Critical API detail missing from guide It's a bitmask where values can be combined 2⁰ (1) = available to download 2¹ (2) = update available 2² (4) = up to date 2⁶ (64) = downloaded Example: status value 69 = 0b1000101 = available + up to date + downloaded Use .contains() method to check specific flags AssetPack.version property - Undocumented feature Auto-assigned by App Store Connect for Apple-hosted packs Increments with each upload of same asset pack ID No file deduplication across asset packs Same file in two packs = counts twice toward 200GB limit Best practice: create separate pack for shared files Shared namespace path requirements Asset pack ID is NOT part of file path Each file must have unique relative path across ALL app's asset packs Example: Foo/10/239/414.png and Bar/10/239/414.png are distinct and won't collide Additional url(for:) bugs beyond iOS 26.1 fix iOS 26 Beta 5: "item with same name already exists" error Workaround: Request URL for directory, then manually append filename TestFlight-only availability - Major limitation not mentioned! Apple-hosted packs currently ONLY work for internal testers on TestFlight or from App Store. Won't work from Xcode until "later this year" HTTP 400 errors expected for non-TestFlight installs ba-serve port workaround URL override port bug exists on multiple device types Use ba-serve -p 443 instead of custom ports