Duo Field Guide
An agent skill that checks your iOS app still works when the screen folds, unfolds or resizes.
When the screen changes shape
Most iOS layouts quietly assume the screen will stay the size it started. Fold it, unfold it, open the keyboard or bump up the text size, and those assumptions show: controls end up out of reach, navigation resets and the thing you were working on vanishes.
What the skill gives an agent
Duo Field Guide packages that knowledge as a skill a coding agent can pick up. It has ten audit rules, each with the failure it catches, how to fix it and how to tell it's fixed. A transition matrix covers resizing, short heights, the keyboard, accessibility, localisation and keeping state. There are pointers to the fold-aware APIs for arrangements, reserved regions and the hinge.
You can ask an agent to audit an app without touching the code, to fix the highest-priority issues, or to check one journey, like editing a draft while resizing with the keyboard open.
A guide people can read too
The same material builds into a single HTML file with four original diagrams and a copyable agent brief. It works offline, with no tracking or external media. It is guidance, not a certification: agents are told to check APIs against the SDK they're targeting and to separate what they read in the source from what they actually tested.
Built with: Codex, Claude Code, Agent Skills (SKILL.md), SwiftUI, UIKit, Python, SVG
Part of the Rolling Waves work archive.