The iPhone that folds. Apps that think.

Muum designs, builds, and ships native iOS apps for iPhone Duo and Apple Intelligence.

Start a project

First, the plan. Every pose, from the outer display to the inner one, is drawn to iPhone Duo's real measurements.

Then, design. Controls to the side, content up front. The new language iOS 27 brings to Duo, in your brand's colors.

Unfold. Uninterrupted. Folded, the app lives on the outer display. Opened, it continues right where it left off on 7.6 inches. One column becomes two.

Intelligence inside. The on-device model summarizes the trip offline, and Siri AI (beta) answers from inside the app through App Intents.

And launch. Every pose is tested in Xcode 27.1 and Device Hub, so it ships to the App Store ready for Duo.

One app. Every pose.

iPhone Duo goes on sale October 23. 5.4 inches folded, 7.6 inches open; it stands upright on a table and sets up like a tent. Your app should feel at home in every one.

On the 7.6-inch inner display, the list sits left and details right. A natural extension of the iPad layout.

Is your current app ready for Duo?

Apps built with the iOS 27 SDK resize as Duo folds and unfolds. Hardcoded screen sizes and device assumptions break layouts. We work through Apple's readiness list with you.

Get my app ready for Duo
  1. We size from the window, not the screen.View and window bounds instead of UIScreen.main; onGeometryChange in SwiftUI.
  2. We re-lay out when it folds.Size can change mid-session, so layout is rebuilt on every change.
  3. We don't mistake size classes for devices.Regular width no longer means iPad; layout follows the space available.
  4. We keep the image's focal point.Full-bleed images and video aren't cropped at the important part on wider displays.
  5. We test every pose.Closed, open, and every orientation, with Device Hub in Xcode 27.1.

Apple Intelligence, inside the app.

With iOS 27, intelligence moved inside apps. We build every layer for your brand, from the on-device model to Siri.

Siri AI (beta) and App Intents

With App Schemas, Siri reaches your app's content and acts on people's behalf. No phrases to memorize.

On-device model

With the Foundation Models framework, Apple's on-device model runs right inside your app.

Onscreen context

With View Annotations, Siri understands what's on screen and knows what “this” means.

Visual intelligence

With image prompts and Vision tools, the model reads a photo, and the fruit on the counter becomes a basket.

The right model for every job.

In iOS 27, Foundation Models works with Apple's models and providers like Claude and Gemini through the same Swift API. We choose per task.

Privacy

Device first. Private Cloud Compute when a larger model is needed. Privacy is part of the design from the start.

Siri AI is rolling out in beta with iOS 27, in English to start; some Apple Intelligence features may not be available in all languages or regions.

Concept work.

Apps that show how we approach Duo and Apple Intelligence. Not real brands, but real care.

Pruva

Airline · Concept

Open it: your trip on the left, an on-device summary on the right. Close it: the boarding pass on the outer display.

iPhone Duo · Foundation Models · Live Activities

Kiler

Grocery chain · Concept

Snap the counter and the basket is ready. Visual intelligence recognizes the fruit, and Apple Pay checks you out.

Visual intelligence · App Clips · Apple Pay

Kasa

Banking · Concept

Ask “Where did I spend the most this month?” and Siri answers from inside Kasa.

Siri AI (beta) · App Intents · Touch ID

How we work together.

Four stages, one team from start to finish.

  1. Discovery

    We clarify the Duo and AI opportunities, the users, and the constraints together.

    You getScope, AI scenarios, and technical plan

  2. Design

    Screens for closed, open, and every pose, in your hand before a line of code is written.

    You getInteractive prototype and design system

  3. Development

    Native development in SwiftUI and Foundation Models, with regular builds along the way.

    You getTestFlight builds in your team's pockets

  4. Launch and beyond

    Every pose tested in Device Hub; App Store review, launch, and ongoing care.

    You getA live, up-to-date app

Make the next great iPhone app yours.

Getting ready for Duo, AI features, or a new app. Tell us in a few sentences, and we'll come back with a discovery call.

Write to us directly
[email protected]

Project type
muumdevAn app studio for iPhone Duo and Apple Intelligence.

Pruva, Kiler, and Kasa are concept apps designed to show Muum's approach and do not represent real brands. Photography from Unsplash. iPhone Duo details are based on Apple's September 9, 2026 announcement and developer documentation.

Apple, iPhone, iPhone Duo, iOS, Apple Intelligence, Siri, Swift, SwiftUI, Xcode, Apple Pay, App Store, TestFlight, and Dynamic Island are trademarks of Apple Inc. Claude is a trademark of Anthropic; Gemini is a trademark of Google. Muum is not affiliated with these companies.

© 2026 Muum. All rights reserved.[email protected]