Apple is testing prototypes of the second-generation iPhone Duo with Face ID built beneath the outer display, according to Mark Gurman on his "Power On" podcast.
The hardware is being tried out for a successor expected next fall. Gurman said Apple has not finalized whether the feature will make it into the product. He also said the company is considering an Action button for a future iPhone Duo, a feature the current model lacks.
The obstacle is physical. The foldable's thin design leaves little room for the depth-sensing components Face ID needs, which is why hiding them under the screen is the interesting part of the report.
The timing is the other detail worth noting. In September, Gurman suggested that smaller components and advances in artificial intelligence could help Apple add Face ID and a dedicated telephoto camera by the third generation. Prototypes with the technology now would put the first of those a generation sooner, if it survives testing.
That "if" matters. A prototype shows what engineers can build, not what Apple will charge for or ship, and this is a single-source account of work the company has not discussed. Gurman himself framed the feature as undecided.
The Action button is the smaller story, but it points the same direction. Both additions would close gaps between the Duo and the rest of the iPhone lineup. The open question is whether Apple can shrink the sensors enough to fit them without giving up the thinness that made the design hard in the first place.