I think it's probably easiest to just redownload the saved pages.

@bearND it's definitely easiest to redownload the saved pages, but the intent is to be able to upgrade the app without losing any of the pages that were saved for offline. So if a user downloads saved pages, upgrades the app, then reopens the app offline, their saved pages should still be there. Whether that means keeping the old version of the article viewer around to view the legacy format or being able to transform the older article format to work with the new article view is still up for discussion.

Keeping the old page loading code around for a while is another valid option. It does come with the burden of keeping a lot of old code around and added complexity. On second thought, that might be still needed for the MW API fallback until Parsoid and RESTBase handle language variants correctly. Maybe keep track of how many pages are stored in the old saved pages format and report that via event logging?

Another option could be to add a converter in the page library or similar.