Duology: Claude Code skills for iPhone Duo foldable app development

Who it's for

• Developers building iPhone Duo foldable apps with Claude Code on a Mac (Apple silicon). The project positions Duology as a set of Claude Code skills for "designing, building, testing and shipping apps on iPhone Duo", distributed as the duology plugin and covering four areas: layout patterns, app recipes, a fold linter and pose checks. These materials serve that official design, build, test and ship workflow; if your job is adapting an interface to the iPhone Duo's foldable form factor, these skills aim exactly at that kind of work. It is a toolkit for the app development process, not a general-purpose text checker or writing assistant.
• Three environment prerequisites: a Mac with Apple silicon, Xcode 27.1 (27A9275 or later) and Claude Code. These three are the only requirements the project states; whether the skills can be used when any one is missing is not documented, so treat that as unconfirmed.
• For users whose main client is Cursor, Codex, Copilot, Gemini CLI or another client: the project labels these environments as skills only, meaning only the skills themselves are installed; slash commands and the lint hook are Claude Code features and follow a different install path. Which tasks the skills can complete in such clients is not documented, and if the checks cannot be triggered in your client, the project offers no alternative.
• The project does not state whether it applies to devices other than the iPhone Duo, nor how far support for natural-language or comment languages goes; do not assume either.

First attempt in 3 minutes

There is exactly one main path: install duology through Claude Code's plugin marketplace — the project names the marketplace as the primary install path — then run one foldable design check on your app.

Prerequisites: a Mac with Apple silicon, Xcode 27.1 (27A9275 or later) and Claude Code installed, plus an iPhone Duo app project ready to check.

1. In a Claude Code session, run the two official commands in order: /plugin marketplace add Kimeur/duology adds the marketplace, and /plugin install duology@duology installs the duology plugin. duology is the plugin the project recommends installing first.
2. Once installed, ask the agent in the same session to check your app's foldable design. The project's description of this check: it runs duo-lint and the 15-point checklist.
3. Watch for the success signal: the agent returns the issues to fix, "most serious first". If you only get an installation confirmation without a list of issues, the check did not actually run — start the task again.

Before you act: the project's description of the check stops at running duo-lint and the 15-point checklist and reporting what to fix; whether it also reads or writes files, executes commands or accesses the network is not stated. On the first run, watch what the agent actually does and confirm the output matches your expectations before continuing.

Use cases

Case 1: a health check for your foldable layout after a major round of changes. Scenario: your app has just gone through a round of iPhone Duo adaptation and you want to know the most serious problems and which one to fix first. How to start: ask the agent in Claude Code to check your app's foldable design; per the project, the thing being checked is your app. Workflow involved: the check runs duo-lint and the 15-point checklist. What to expect: a list of issues ordered from most to least serious that you can work through one by one. How many items it contains, its exact format and whether fixes are included are not documented, and the project offers no official process for the fixes that follow.

Case 2: bringing the skills into a non-Claude Code client. Scenario: you mainly work in Cursor, Codex, Copilot or Gemini CLI and want the skills available close at hand. How to start: run npx skills add Kimeur/duology in that environment. Workflow involved: the officially labeled skills-only install, i.e. the skills themselves only. What to expect: the CLI places the skills where the agent looks for them, per the project. Installation is the part you can confirm; which tasks the skills can then trigger, and whether results match Claude Code, you need to verify in your own client. If the skills do not behave as expected, go back to the Claude Code main path to confirm the functionality itself works.

Boundaries

• Keep the platforms apart: the plugin marketplace is the Claude Code install surface, and the two commands above run inside Claude Code as slash commands; Cursor, Codex, Copilot, Gemini CLI and others go through npx skills add Kimeur/duology, and that path is skills only. Do not treat the latter as a marketplace install, and do not assume the two paths have equal capabilities.
• Side effects and confirmation points: the project does not state whether the check modifies files, executes commands or accesses the network, and says nothing about confirmation points; both are unconfirmed, so follow the first-attempt precautions before acting.
• Dependencies: duology-recipes and duology-ship need duology, which provides /duo-doctor; duology-design and duology-features install on their own, but their skills point to duology's skills (duo-layout, duo-continuity, duo-scenes), so install duology first.
• Runtime: the skills target app development on the iPhone Duo foldable. The differences between simulator and physical device, and any requirements on specific Xcode project structures, are not documented.
• Version: the project specifies Xcode 27.1 (27A9275 or later), meaning 27A9275 is the minimum; check the official page for any later changes.
• Key unconfirmed information: what /duo-doctor actually does, the purpose and triggers of each skill and each companion plugin, whether devices beyond the iPhone Duo are covered, and the detailed format of the check output are all absent from the official page. Until the project fills these gaps, treat none of them as supported.