Apple says Siri was rebuilt from scratch for iOS 27, causing delay
Apple explained that the new Siri in iOS 27 required a complete redesign and integration of advanced AI models, which extended its development timeline.
Apple disclosed that the Siri assistant in iOS 27 was reconstructed from the ground up, a process that contributed to the feature’s later-than-expected release. During a post-WWDC technical session, senior engineers Craig Federighi and Amar Subramanya, along with Siri lead Mike Rockwell, described the overhaul. Rockwell said an earlier incremental version that added tool-calling was built but did not meet the company’s vision, prompting a decision to pursue a more extensive redesign. The rebuilt Siri now runs on newer AI models, supports multimodal interactions, and is intended to provide a consistent experience across iPhone, iPad, Mac, Apple Watch, Vision Pro, CarPlay and AirPods. Apple emphasized that privacy and cross-platform availability were core goals of the new architecture.
"We rebuilt Siri from the ground up on top of the new models, making it natively multimodal and privacy-focused," Rockwell said.
The company’s approach indicates that the original roadmap would have delivered only modest AI enhancements, while the full revamp required the additional development time.