Rendering and layout took 47 percent of the tickets after Discord's iOS Fabric flip

Measurement is the contract that broke first. On the old architecture, asking a view where it was returned a position in the window: one origin, the top-left of the screen. Under Fabric, a view is measured relative to its Yoga root, and a modal is its own root ^[8]. Outside a modal, the root of the tree is the top of the window, so both answers are identical ^[9]. The code keeps working and the numbers keep looking right.

Discord's context menu is where the two spaces separate. It renders in a FullWindowOverlay that spans the whole window, positioned from coordinates measured on the row you long-pressed ^[10]. Opened from a normal screen, it lands correctly. Opened from inside a modal, the row reports its position relative to the modal, the overlay reads those numbers as window coordinates, and the menu appears offset ^[11]. That code was written years earlier and worked exactly as intended on the old renderer, and nobody touched it during the migration ^[19].

Software Mansion described the scope of its year as the stretch between an app that launches and an app as good as the one you are replacing, and put a few hundred small problems in that gap ^[12][7].

The percentages are shares of one ticket sample. Rendering and layout at 47 percent plus the migration proper at 14 percent leaves 39 percent spread across the remaining rows ^[15]. Discord's own teams had already spent months getting the app to build and run before Software Mansion joined ^[2], so the 14 percent covers the build-system, codegen and dependency work that survived into the parity phase, not the whole cost of getting there ^[18].

For the 47 percent to carry into your own planning, your app needs Discord's shape: a chat surface backed by a native-driven data model, custom rendering optimizations, a decade of accumulated business logic, and a user base that notices a one-frame glitch ^[16]. The categories are easier to reuse than the percentages. Software Mansion wrote that most of these were not bugs: "They were places where an implicit contract changed: where a view sits on screen, whether it exists in the native tree at all, and how the framework finds your native code." ^[13]

The rest of the long tail is harder to schedule. Software Mansion lists years-old bugs that had been hiding in plain sight, races that only show up under real production load, and other migrations running in parallel, each bringing its own New Architecture quirks ^[14]. The official docs cover turning the flag on, and Software Mansion says most apps and libraries have already moved ^[17].