Hi. I've noticed on both iOS 17 and iPadOS 16 that when an user opens a website in a WKWebview (e.g from Gmail), then requests it to be opened in the external Safari app (through the "compass" icon), their localStorage data is not transferred to the Safari tab.
This behaviour breaks web experiences that rely on data being locally stored, e.g auth tokens or user identification data. It effectively stops users from being able to use some websites outside of an in-app context.
I am aware of Webkit's tracking prevention mechanisms such as https://webkit.org/tracking-prevention/#partitioned-third-party-localstorage, but I don't think this should apply to this case. Here the user is navigating between two Safari tabs (one internal and one external) on the same domain, exact same URL, by pressing a native Safari webview icon. There is no third-party cross-domain tracking happening.
Is this a bug or intended behaviour?