iPhone Duo plugin for Claude Code and Codex

imageAgent Skills imageLicense: MIT

Adapt, audit and design-review iOS apps for iPhone Duo — Apple's foldable iPhone (announced 2026-09-09, ships on iOS 27.1). The Duo APIs are newer than any current model's training data, so an agent asked about them invents plausible symbol names. This plugin replaces that guesswork with references that carry a provenance tag on every symbol.

Three components:

Requirements

• Claude Code or Codex for a native plugin install (options 2 and 3). Codex packaging and skill discovery were checked with Codex CLI 0.157.1. The skills also work through the Agent Skills CLI in Claude Code, Cursor, Codex and other supported hosts — see option 1.
• macOS with Xcode Command Line Tools for the toolchain gate (xcodebuild -version, xcrun --sdk iphoneos --show-sdk-version). The grep audit itself runs anywhere; the toolchain gate is what decides whether iOS 27.1 APIs may be written yet. Xcode 27.1 (beta since 2026-09-18) is what ships the iOS 27.1 SDK, the iPhone Duo simulator and Apple's App Resizability agent skill; without it the skills do the resizability work and defer the Duo-only APIs.
• jq — reading Figma JSON and SDK dumps without loading them into context.
• python3 — a few reference snippets use it for plist and geometry math.
• Network access — the design review fetches HIG pages live (their JSON twins) rather than quoting them from memory.
• Figma MCP server for the Figma intake path only:

  # Claude Code
  claude mcp add figma -- npx -y mcp-figma mcp
  # Codex
  codex mcp add figma -- npx -y mcp-figma mcp
  

  Set a Figma personal access token as that server requires. The tool names in the references (mcp__figma__get_file, …) follow the server name you register — if you register it under a different name, the mcp__<server>__ prefix changes with it. Sketch / PNG / PDF exports need no MCP.

Install

1. Skills only, via the Agent Skills CLI (Claude Code, Cursor, Codex, …)

npx skills add anatoliykant/iphone-duo-plugin

This installs the two skills, including the complete read-only audit workflow; agents/ is ignored by that CLI. Select Codex when prompted to install for Codex. To get the Claude audit agent as well, copy agents/iphone-duo-audit.md into ~/.claude/agents/ or install the plugin (option 2) — not both: a user-scope agent overrides the plugin one, and you end up maintaining two copies.

2. As a Claude Code plugin (skills + agent, pinned versions)

claude plugin marketplace add anatoliykant/iphone-duo-plugin
claude plugin install iphone-duo@anatoliykant-plugins

Then /reload-plugins if Claude Code asks for it. Behind an SSH-less setup use the explicit URL:

claude plugin marketplace add https://github.com/anatoliykant/iphone-duo-plugin.git
# or: CLAUDE_CODE_PLUGIN_PREFER_HTTPS=1 claude plugin marketplace add anatoliykant/iphone-duo-plugin

Installed copies are pinned to the version in .claude-plugin/plugin.json, so a new release is a version bump plus a tag — run claude plugin update iphone-duo@anatoliykant-plugins to move to it. CHANGELOG.md lists what changed in each one.

3. As a Codex plugin (skills + shared audit workflow)

codex plugin marketplace add anatoliykant/iphone-duo-plugin
codex plugin add iphone-duo@anatoliykant-plugins

Start a new Codex session after installation. For a local checkout, including changes that have not been published yet, replace the first command with:

codex plugin marketplace add /absolute/path/to/iphone-duo-plugin
codex plugin add iphone-duo@anatoliykant-plugins

The portable root plugin.json declares the Agent Plugins format; Codex discovers both skills under skills/. .agents/plugins/marketplace.json points to this repository's root. The Claude manifest stays in .claude-plugin/, and both manifests carry the same version.

To refresh a Git-backed marketplace, run codex plugin marketplace upgrade anatoliykant-plugins, then codex plugin add iphone-duo@anatoliykant-plugins and start a new session. A local marketplace reads from its checkout; keep that directory available. Use codex plugin list --marketplace anatoliykant-plugins to inspect the plugin. Clients without codex plugin add can use the plugin directory UI described in the OpenAI plugin documentation or the skills-only install above.

4. From the Claude community marketplace

The public claude-community catalog did not list this plugin when checked on 2026-09-30. This does not indicate whether a submission was received; publication is managed by Anthropic. Once the entry is published:

/plugin marketplace add anthropics/claude-plugins-community
/plugin install iphone-duo@claude-community

5. By hand

Copy skills/iphone-duo and skills/hig-design-review into ~/.claude/skills/ (or a project's .claude/skills/), and agents/iphone-duo-audit.md into ~/.claude/agents/.

For Codex skills-only installation, copy the two whole skill directories, including their references/, into ~/.agents/skills/ (user scope) or .agents/skills/ in the app project (repo scope). Start a new session. No Claude agent file or Codex custom-role configuration is needed.

Usage

Both skills load on their own when a request matches. Typical triggers: "is this app ready for iPhone Duo", "what breaks on the foldable", "add vertical toolbar support", "reserved regions", "review this Figma against the HIG".

Invoke them explicitly in Claude Code with their scoped names:

/iphone-duo:iphone-duo           # adaptation work
/iphone-duo:hig-design-review    # mockup review

In Codex, select the installed skill from the $ picker, or use its full plugin name:

$iphone-duo:iphone-duo Audit this repository for iPhone Duo readiness. Do not change source files.
$iphone-duo:hig-design-review Review this Figma mockup against the HIG: <Figma URL>

Skills-only installs use $iphone-duo and $hig-design-review instead. Both skills accept --help and --version as standalone requests, for example $iphone-duo:iphone-duo --version.

Readiness audit

Ask for an audit in plain language. In Codex the iphone-duo skill runs the shared references/audit-workflow.md; it also works when subagents are unavailable. In Claude Code the skill delegates to the audit agent when installed, or runs the same workflow directly. You can also call the Claude agent explicitly:

Agent(subagent_type: "iphone-duo:iphone-duo-audit",
      prompt: "Repo root: /path/to/app. Scratch dir: /tmp/duo-audit. Write the report to /tmp/duo-audit/report.md. Skip Pods and the widget extension.")

The report comes back in a fixed shape:

# iPhone Duo readiness audit — <app> (<git rev>, <date>)

## Summary
<launches? resizes? adapts?> · Toolchain: <SDK> · Swift files scanned: N (production N, tests N)

## Findings
| # | Severity | Category | Sites | Example | Fix |
|---|---|---|---|---|---|

Severities run BLOCKER (will not launch on the iOS 27 SDK) → HIGH → MEDIUM → LOW → INFO, and every finding points at the reference section that fixes it. Audits leave the source code unchanged; only scratch output and a report you explicitly request may be written. These are workflow instructions; filesystem enforcement depends on the host's permissions and sandbox configuration.

Design review

Give it a Figma URL (…/design/<fileKey>/<name>?node-id=12-345), a file key, or Sketch/PNG/PDF exports. It returns findings with HIG citations, a severity per finding, and a verdict. It posts comments on Figma nodes only when you explicitly ask, and never edits a file.

What's inside

plugin.json                  portable Codex / Agent Plugins manifest
.agents/plugins/             Codex marketplace
.claude-plugin/              Claude Code manifest + marketplace
skills/iphone-duo/            SKILL.md + 8 references (includes the shared audit workflow)
skills/hig-design-review/     SKILL.md + 4 references
agents/iphone-duo-audit.md    Claude Code adapter for the shared audit workflow
scripts/validate-plugin.py   package and version checks used by CI

Status and freshness

Every new symbol in the references carries a provenance tag — where the name came from, and whether it has been confirmed against a real SDK:

Research date 2026-09-10; SDK-verified 2026-09-21 against the iOS 27.1 SDK in Xcode 27.1 beta 1 (27A9269). Every Duo symbol in the references now carries a real annotation. One capability the HIG describes — collapsing an overlay arrangement's secondary view — has no API in that SDK, and the references say so instead of guessing a name.

Also folded in on that date: Apple's developer article "Preparing your app for iPhone Duo", the camera articles for AVKit and AVFoundation, the September 2026 documentation/updates sections, the Xcode 27.1 beta release notes, and both iPhone Duo Group Labs (Meet with Apple 285 and 286). Labs are transcribed from Apple's own captions and are cited for guidance, never for API spellings.

Re-check after 2026-10-23 (ship date), or sooner if an iOS 27.1 RC appears: the availability annotations still read iOS 27.1 beta, so re-run the SDK symbol grep in skills/iphone-duo/references/testing-and-sources.md §Verify symbols and retag. That file's §Freshness lists the machine-checkable signals.

The plugin has no executable runtime, bundled MCP servers or hooks. The host runs its instructions using your configured tools and permissions. Design review fetches live sources and can use your Figma MCP connection; audits write scratch output and an explicitly requested report.

Development checks

python3 scripts/validate-plugin.py
claude plugin validate .
git diff --check

The validator checks both manifests and marketplaces, skill version answers, bundled references, and release tags. Run it before publishing a version. See CHANGELOG.md for changes.

Release destinations

Update both plugin manifests and both skill version literals together. Push main and a matching v<version> tag, wait for CI, then create the GitHub Release with notes from the changelog.

Credits

• Apple Inc. for the iPhone Duo tech talks (111461–111466), WWDC26 session 278 and the Human Interface Guidelines — quoted material stays © Apple, see NOTICE.md.
• FloWritesCode/fwc-swiftui-skills (MIT) for the tiered-migration and state-continuity framing.

License

MIT — see LICENSE. Apple material quoted in the references is excluded; see NOTICE.md.