My question is a bit unique. Here's some background:
My team started off with designs that were dropped into our lap. We didn't get any journeys, no stories and no annotations on the design. We barely got a working prototype of how the app should flow.
Now, I'm responsible for writing the user stories and journeys. We're halfway through the project - i only got involved a short while ago. A lot has been developed already (from mocks on zeplin).
During planning, there were things that got updated (tech functionalities aren't allowing for some of the design proposals).
My question is, what should the single source of truth for an app be? Should it be the mockups (that are updated to reflect the outcome of these plannings?), or should it be the stories/journeys? Do you still maintain that stories & journeys should be the SSOT even if the stories didn't cover what was already developed?
Additionally, WHEN it is expected that the designs need to be updated? Keep in mind, that the design was dropped into our laps by a designer that left the company.