When Apple unveils its Apple Watch Series 12, only minor improvements are expected. Newly discovered code suggests that the surprises will be in watchOS 27 instead of the hardware. Apple Watch Series 11 health sensors won't change much in the Series 12, but watchOS will hold the surprises.

Apple has been steadily releasing new betas since WWDC, and they have included over 50 improvements in watchOS 27. Now, however, it appears that the most significant updates have remained hidden. In hardware, there may be a ceramic Apple Watch Series 12, but otherwise a redesign is some years away.

For now, though, according to user "pdfu" in the MacRumors forum, the code fragments found include references to a "Readiness" health app, revised workouts with multiple sets and durations, and potential new heart-sensing hardware. Of those, the heart-sensing feature is the most interesting but it's also hardware dependent. There is no guarantee that it will launch with the Apple Watch Series 12.

User "pdfu," though, says that the code shows Apple improving how it measures heart rate. In place of the previous measurement implementation called Sunstone3p75plus., watchOS 27 includes an optical-sensing family called Sunstone4p0. Apple Watch measures heart rate optically, shining a light into the skin and detecting changes when that light is reflected back.

The difference with Sunstone4p0 is reportedly in an improvement in how the Apple Watch's own hardware makes it harder to measure a weak pulse signal. Readiness and workout changes: Perhaps the most visible feature that may be announced at the September 9, 2026 launch is this new Readiness app. Previously code-named Cobalt, it's not clear what it does, except that it is health-related and separate from the existing Vitals app.

The Readiness app itself has not been included in the beta. Code references to it, though, suggest that it's related to the Workout app. That Workout app is itself getting an update.

Specifically, strength workouts in watchOS 27 will now get more granularity, coping with more sets of exercises and storing data about them such as duration, repetition, and equipment used.