Apple's second-generation iPhone Duo could gain Face ID , with prototypes already incorporating the technology beneath the outer display, according to Bloomberg 's Mark Gurman .

In the latest episode of his "Power On" podcast , Gurman described Apple's work on adding facial authentication technology to its foldable iPhone. The company is said to be testing the hardware for a successor expected next fall, but has not finalized whether the feature will ship.

The current, first-generation ‌iPhone Duo‌ relies on a fingerprint sensor embedded in its side button, just like the iPad . Its thin design leaves limited space for the depth-sensing components needed for ‌Face ID‌.

News of the prototype seems to represent a more concrete development of Gurman's earlier prediction about future ‌iPhone Duo‌ upgrades.…