It’s no secret that Apple’s been quietly trying to build an augmented reality headset. Over the past several years, Apple has hired, acquired, attempted to patent and repeatedly talked up the idea — Apple CEO Tim Cook called AR as big an idea as the smartphone, and reportedly had 1,000 engineers working on the tech in 2017.

But despite repeated rumors that Apple is getting ready to produce such a headset — Bloomberg, CNET and reliable Apple analyst Ming-Chi Kuo have all suggested Apple’s aiming to produce it in 2019 and ship it in 2020 — it’s only today that we’re seeing what appears to be implicit confirmation from Apple itself that an AR headset is being tested inside the company.

It comes to us in the form of this screenshot from iOS developer and reliable leak-finder Steve Troughton-Smith:

The iOS 13 GM also comes with a readme file (!) for how employees can run Stereo AR apps on an iPhone when you don't have access to Apple's headset pic.twitter.com/SeZEHW8p0S — Steve Troughton-Smith (@stroughtonsmith) September 10, 2019

StarBoard. Garta. If you’ve been following Apple AR headset rumors closely, you’ve heard these codenames before — perhaps alongside Luck, Franc, and HoloKit, all of which have recently appeared in internal builds of iOS 13, according to reports from 9to5Mac and MacRumors. But now, Troughton-Smith and 9to5Mac’s Guilherme Rambo say they’ve somehow made their way to semi-public, developer-facing betas and masters of iOS 13, too.

Compelling evidence it’s in testing — but not necessarily more

The screenshot pretty much says it all: Apple is testing an internal device known as “Garta,” and if you want to test your stereo AR apps with that device, you’ll want to set them to “worn” mode so that it can apply different “distortions” than if the app is being “held” instead.

Which implies that Garta is a stereoscopic AR headset — because that’s the kind of device you would wear, and which would adjust the way an augmented reality app would look to match lenses in front of your eyes. (AR and VR headsets typically adjust their computer graphics “projections” to properly stretch across your field of view while using as little processing power as possible.)

Troughton-Smith says the iOS 13 code also seems to have references to a game controller that might be used alongside these apps, too:

The GameController framework in iOS 13 also has a gamepad profile for a device meant to be used while using stereo AR apps. The controller profile has a clicky trackpad, a trigger button, and a system (home?) button. Handheld controller for Apple's headset? — Steve Troughton-Smith (@stroughtonsmith) September 10, 2019

But it’s not clear what the scope of Apple ambitions are right now — whether we’re talking about the fabled Apple Glasses, the 8K-resolution standalone AR+VR headset that CNET spoke about in 2018, or perhaps something less interesting. More recently, Apple analyst Ming-Chi Kuo predicted that the first product would be more of an iPhone accessory, which might line up with the idea of apps having both “worn” and “held” modes, and happens to be what Rambo recently reported as well.

That report suggested these codenames might refer to something more akin to Samsung Gear VR or Google’s Cardboard: a nifty viewer you might sometimes pull out when you want to slot in a phone. And that might suggest Apple may not try to put these tester devices on shelves, because Tim Cook has publicly said Apple won’t ship an AR product until it can deliver “a great experience,” something he didn’t believe was possible with existing concepts.

For now, it’s merely the most explicit sign yet (though still implicit) that Apple is indeed working on an AR headset.