Apple unveiled Siri AI as part of watchOS 27 at WWDC 2026, but the feature runs only on select models. Support begins with the Apple Watch Series 9 and extends to the Series 10, Series 11, Ultra 2, Ultra 3, and the third‑generation SE. Older watches, including Series 6‑8 and the original Ultra, are excluded despite needing an Apple‑Intelligence‑enabled iPhone nearby. Nearby iPhone does the heavy AI work, not the watch.

Marketing manager Cait Dooley told TechRadar the cutoff reflects hardware limits. The Series 9 introduced the S9 chip with a four‑core Neural Engine, roughly twice the speed of the S8’s two‑core engine found in earlier models. Faster on‑device processing enables Siri’s double‑tap gesture and local inference, which Apple says delivers the best user experience. This performance boost is essential for real‑time voice commands.

The lack of a detailed technical explanation leaves consumers guessing why devices like the Series 8 or original Ultra cannot run Siri AI. With the feature relying on both a supported watch and a paired iPhone, owners of older hardware face a functional gap that may pressure upgrades. Apple’s compatibility list now clearly separates supported and unsupported models.