Cover, inner and half open: stock research in each iPhone Duo posture.

Three postures, three different screens

The Duo has a 5.4-inch cover screen and a 7.6-inch inner screen with the same aspect ratio, and it ships with iOS 27.1 (Apple Newsroom). Moving between them is a size change for the app, not a restart. How an app that was not updated looks depends on the SDK it was built with, and only apps built with the iOS 27.1 SDK get the full screen (9to5Mac).

So the same app can look right in one posture and wrong in the next. That is why it is worth checking each one on its own.

Cover screen: the quick look

Closed, the Duo is where you glance at a watchlist or a price alert. The common problem here is a dead strip: apps not updated for the device can leave a black column on the right of the cover screen. Owners also report that Safari wastes width with the phone closed (Macworld, day one, MacRumors forums). On a narrow screen, a column of lost width is a column of numbers you cannot see.

What to check: open your watchlist app closed and look at the right edge. Does the list reach it?

How Cala lays it out: on the cover screen Cala uses its phone layout with drawers. On narrow widths one pane shows at a time, so you get one readable view instead of three cramped ones. Opening one side panel closes the other.

Inner screen: the deep read

Open, the Duo is where you read a filing or compare notes with a chart. The common problem is black bars: apps not rebuilt for the device show a phone-sized layout centered on the big screen (Macworld review roundup, GadgetReview). You unfold for more room and get the same room with a frame around it.

The inner screen is also where Split View lives. It is fixed at 50/50 with no resizing, so a chart next to another app gets half the screen (MacRumors, MacStories). In landscape, the keyboard covers a large part of the open screen, which matters when you are typing notes or questions (MacRumors developer notes).

What to check: open your research apps on the inner screen in portrait and in landscape. Look for black bars, and try typing in landscape to see how much is left above the keyboard.

How Cala lays it out: with the inner screen flat in landscape, the Explorer and the Cala AI chat sit side by side, so you can browse and ask in the same view. In inner portrait, opening one side panel closes the other so nothing gets squeezed. On a Duo the side panels start open and are not collapsed for you. Cala runs as a single window and does not advertise Split View or multi-window support. Split View on the Duo is fixed at 50/50 for any two apps paired there.

Half open: the desk posture

Half open, the Duo stands on its own like a small laptop, with the hinge running across the middle of the inner screen. This is useful on a desk next to a bigger monitor, or for keeping an eye on something while you type on the lower half. The risk is content landing right on the hinge, or a form you need to type into sitting on the upper half.

What to check: stand the phone half open with each app and see what ends up on the fold line.

How Cala lays it out: the welcome screen splits around the hinge, and sign-in forms stay below it, on the half you type on. Side panels behave as in portrait, so opening one closes the other. Because Cala knows where the hinge and the corner cutouts are, and that updates on every posture change, the layout knows where not to put things.

Moving between postures

Changing posture should not cost you your work. In Cala, folding or unfolding resizes the same running session. The app is not reloaded and your open desk stays as it was. The longer version is in Fold and unfold the iPhone Duo without losing your research, and the full app checklist is in Trading apps on the iPhone Duo.

Cala is an AI research terminal, not a broker, and it does not give buy or sell advice. If you want to try it on the Duo, it is on the App Store: get Cala Terminal. It is also on Mac, Windows, iPad and the web. For how the research desk works, see Cursor for finance. Our sister site has a guide from the AI investing side: AI investing on the iPhone Duo.

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