--- title: iPhone Duo dev tools are already here, sort of | daily.dev description: Ahead of Apple's official iPhone Duo SDK (version 27.1), a third-party simulator from Bitrig is already letting developers test folding-slider hinge... canonical: https://daily.dev/posts/iphone-duo-dev-tools-are-already-here-sort-of-dvktjfd7w twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: iPhone Duo dev tools are already here, sort of | daily.dev og:description: Ahead of Apple's official iPhone Duo SDK (version 27.1), a third-party simulator from Bitrig is already letting developers test folding-slider hinge... og:url: https://daily.dev/posts/iphone-duo-dev-tools-are-already-here-sort-of-dvktjfd7w og:image: https://api.daily.dev/og/posts/DVKTJFd7W.png og:image:alt: iPhone Duo dev tools are already here, sort of og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # iPhone Duo dev tools are already here, sort of **[Trends](https://daily.dev/sources/trends)** · 2 min read · 1 upvotes · 0 comments ## Summary Ahead of Apple's official iPhone Duo SDK (version 27.1), a third-party simulator from Bitrig is already letting developers test folding-slider hinge interactions, complete with a live hinge-angle readout. Developers acknowledge the tool is a stopgap that will be obsolete once Apple ships its real SDK. Apple has scheduled online group labs and Q&As covering Duo development, with a heavy emphasis on SwiftUI, leaving UIKit developers watching closely. Separately, Framer has demoed AI-assisted prototyping of Duo UI, with someone recreating a folding slider interaction using a few prompts in the Framer Agent, highlighting how design tooling is moving faster than the native SDK. ## Content The iPhone Duo simulator shipped with Xcode 27.1 beta, and the iOS dev community immediately dove in. The reaction is mostly enthusiastic, occasionally humbling. The short version of what's new: two new size class combinations (compact-compact and regular-regular), a vertical toolbar bar system with APIs like `axisBehavior` and `toolbarVerticalCompressionBehavior`, `ArrangementView` for fold-aware split/overlay layouts, `reservedRegions` to avoid the fold and camera occlusions, and `onHingeChange` for responding to fold angle. Apps targeting iOS 27 SDK get the adapted look; anything built against older SDKs gets a compatibility mode that mostly works but misses the point. The simulator itself is getting genuinely good reviews. Donny Wals, Sean Allen, and Paul Hudson (twostraws) are all publicly poking at their own apps. The 3D interactive model — drag, tent, rotate — is the feature everyone's excited about. "Once you try it, you won't want to go back," one developer wrote. A third-party CLI called `hinge` lets you script fold angles for automated testing, which is a nice touch. But the surprises are real. Donny Wals ran into the front camera obscuring a close button he'd placed top-right. Sean Allen got burned by an AI agent putting `ignoresSafeArea` on the wrong view and not catching it. The consensus forming fast: if you've been using `UIScreen.main.bounds` or checking `userInterfaceIdiom` instead of size classes, the Duo will find you out. The web side is less rosy. Wes Bos noted that Safari on the folded Duo adds toolbars to both the bottom *and* the right of the viewport, leaving very little room for actual content. No sign of the viewport segment or device posture API either. There's also a thoughtful critique of `ArrangementView` making the rounds: the API conflates two genuinely different layout logics (split and overlay) into one container, with confusing primary/secondary semantics and no centralized state for child views. The argument is that it's purpose-built for fold-aware relationships and becomes a liability if you reach for it as a general two-view container. Expo SDK 58 beta already has iPhone Duo support. Bitrig, the AI Swift dev tool built by former Apple SwiftUI engineers, added an interactive 3D simulator before Apple's own shipped. The ecosystem is moving fast. The device costs around $2,000. The simulator is free. Most developers seem to agree that's the right order to do things. ## Questions this post answers ### Is there a way to test iPhone Duo folding UI interactions before Apple releases its official SDK? Yes, a third-party simulator from Bitrig is circulating in pre-release that lets developers test folding-slider interactions, including a live hinge-angle readout that updates as the device folds. It is explicitly a stopgap tool expected to become obsolete once Apple ships its official 27.1 SDK for the iPhone Duo. _daily.dev surfaces early tooling like this for developers prototyping foldable UI ahead of official support._ ### Will SwiftUI or UIKit be the primary framework for building iPhone Duo folding UI? SwiftUI appears to be Apple's primary path for Duo UI adaptation, based on the heavy presence of SwiftUI sessions among Apple's announced iPhone Duo group labs and Q&As. UIKit developers are watching closely since it is unclear how much UIKit support will be covered in these official sessions. _Developers choosing between SwiftUI and UIKit for foldable support can track framework signals on daily.dev._ ## Community take How the wider developer community reacted, aggregated from 2 discussions and 9 comments across x (as of 2026-09-24). **TL;DR:** Developers experimenting with the Duo simulator find early API and documentation coverage thin, leading to guesswork about how to properly adapt apps, with some suspecting Apple is deliberately withholding examples ahead of launch. **Sentiment:** 10% positive · 60% mixed · 30% skeptical **The case for** - Some developers are excited to see how Apple's own apps get redesigned for the Duo as inspiration for their own layouts. - A workaround exists to force certain beta apps to open on the simulator despite limited official support. **The pushback** - The lack of more complete API examples makes it harder, especially for independent developers, to figure out good adaptation patterns. - Safari's multi-window support is oddly limited to only two windows. - Running the Duo simulator reportedly puts heavy strain on the host Mac. **By community** - x (mixed): Developers share frustration over sparse tooling and documentation while remaining curious and proactive about adapting their apps ahead of launch. **Open questions** - Why does Apple appear to be withholding more complete Duo API examples and app designs before launch? - Will performance issues with running the Duo simulator be addressed soon? **Highlights** > @josesaezmerino I guess so, but it does make it harder for (especially independent) developers to figure out a good way to adapt apps and make sure they feel at home on the Duo. > — [DonnyWals on x · 1 points, 1 comments](https://x.com/DonnyWals/status/2102714445159977056) > @DonnyWals Agree, Safari is the only multi-window (multi scene app) and it is limited to 2 windows for some reason. > — [malhal on x](https://x.com/malhal/status/2102747644871446957) > @DonnyWals hopefully in the next build. also is it just me or when running the duo simulator it destroys the mac? other devices seem to work fine, hopefully this will also be addressed soon > — [mariusfanu on x](https://x.com/mariusfanu/status/2102776240277241971) > @DonnyWals That says a lot about where Apple is with their own apps. I bet they're not sleeping for the next 20 days > — [afterxleep on x](https://x.com/afterxleep/status/2102792870121836668) **Source threads** - [x](https://x.com/Baconbrix/status/2102798276852674762) · 0 points · 0 comments - [x](https://x.com/DonnyWals/status/2102708256447569967) · 0 points · 9 comments --- Tags: [#mobile](https://daily.dev/tags/mobile), [#apple](https://daily.dev/tags/apple), [#ios](https://daily.dev/tags/ios), [#swiftui](https://daily.dev/tags/swiftui) [View this post on daily.dev](https://daily.dev/posts/iphone-duo-dev-tools-are-already-here-sort-of-dvktjfd7w) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"iPhone Duo dev tools are already here, sort of","url":"https://daily.dev/posts/iphone-duo-dev-tools-are-already-here-sort-of-dvktjfd7w","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/iphone-duo-dev-tools-are-already-here-sort-of-dvktjfd7w"},"datePublished":"2026-09-17T21:19:14.334Z","dateModified":"2026-09-24T19:04:15.389Z","description":"Ahead of Apple's official iPhone Duo SDK (version 27.1), a third-party simulator from Bitrig is already letting developers test folding-slider hinge...","isAccessibleForFree":true,"articleSection":"Trends","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"Trends","logo":"https://media.daily.dev/image/upload/s--ZfSp3asX--/f_auto,q_auto/v1780996004/logos/trends?_a=BAMAMiWQ0","url":"https://daily.dev/sources/trends"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/iphone-duo-dev-tools-are-already-here-sort-of-dvktjfd7w","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":1},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"mobile,apple,ios,swiftui","timeRequired":"PT2M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Trends","item":"https://daily.dev/sources/trends"},{"@type":"ListItem","position":3,"name":"iPhone Duo dev tools are already here, sort of"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/iphone-duo-dev-tools-are-already-here-sort-of-dvktjfd7w#faq","mainEntity":[{"@type":"Question","name":"Is there a way to test iPhone Duo folding UI interactions before Apple releases its official SDK?","acceptedAnswer":{"@type":"Answer","text":"Yes, a third-party simulator from Bitrig is circulating in pre-release that lets developers test folding-slider interactions, including a live hinge-angle readout that updates as the device folds. 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