What changes in the architecture before the layout changes?
The architecture must separate durable product state from its current presentation so the interface can recompose without restarting the user’s task.
- Keep navigation and domain state outside size-specific view trees.
- Represent window class and posture as explicit presentation inputs.
- Avoid duplicating business logic for compact and expanded compositions.
How should compact and expanded layouts share content?
Compact and expanded layouts should render the same underlying state while changing hierarchy, density and placement according to the active task.
- Define which content remains primary in every state.
- Move supporting tools without resetting selection or scroll position.
- Test accessibility order separately from visual placement.
What belongs in an iPhone Duo migration plan?
A migration plan should cover lifecycle events, layout contracts, state restoration, input behavior, performance budgets and a device-state test matrix.
- Begin with instrumentation and a baseline on the existing app.
- Adapt one complete user journey before broad rollout.
- TODO: Map the plan to verified Apple frameworks and deployment requirements.