Solved: was running in private mode (doh)
I’m using the base accounts-ui and accounts-password packages. Just noticed with iOS 9 Safari, when I refresh the page, it’s now logging out the user. Haven’t tested in other browsers on iOS 9. And I didn’t change anything in my code between updating from iOS 8 (working) and iOS 9 (not working).
Anyone else experiencing this? Is it a known issue? Something to do with the new way iOS 9 Safari handles cookies? Any workarounds?