According to Apple, the watchOS 27.0.1 update fixes an issue causing Apple Watch Series 12 and Apple Watch Ultra 4 models to restart unexpectedly. Released on Wednesday, just over a week after watchOS 27.0 reached the public, the software addresses spontaneous reboots that occurred during everyday tasks like editing watch faces, making calls, using Siri AI, opening Apple Maps or the App Store, recording workouts, or even when the device was sitting idle, as reported by affected users on forums.
Neural Engine Timeout Identified as Root Cause
An Apple forums post outlined a Neural Engine timeout on affected Apple Watch models as the underlying cause of the bug, according to available documentation. Specifically, a Neural Engine command waited 2,020 milliseconds, exceeding the strict 2,000-millisecond limit, which forced the device to reboot. While watchOS 27.0.1 resolved these spontaneous reboots, Apple did not formally disclose the technical trigger in its official release notes. According to Apple’s website, there are no Common Vulnerabilities and Exposures (CVE) entries associated with watchOS 27.0.1, indicating the release lacks major security patches or significant vulnerability fixes.
Device Compatibility and Exclusive Focus
The watchOS 27.0.1 update is available exclusively for the Apple Watch Ultra 4 and Apple Watch Series 12, serving strictly as a targeted bug-fix update for the 2026 hardware lineup, according to Apple’s release documentation.
Did You Know?
Some users upgrading to the Apple Watch Series 12 or Ultra 4 may temporarily miss out on hypertension notifications because regulatory clearances are still in process, according to Apple’s feature availability page.
How to Install the watchOS Update
To update directly on the watch, users must ensure the battery is charged to at least 50% and connected to Wi-Fi, open the Settings app, tap General, select Software Update, and follow the on-screen instructions. Alternatively, users can open the Apple Watch app on a paired iPhone, navigate to General and Software Update, and download the software once available.
Frequently Asked Questions
What devices are compatible with watchOS 27.0.1?
According to Apple, the update is available exclusively for the Apple Watch Ultra 4 and Apple Watch Series 12.
Does watchOS 27.0.1 contain security fixes?
No. Apple’s website confirms there are no CVE entries associated with watchOS 27.0.1, indicating it is a bug-fix release without major security patches.
What caused the Apple Watch reboot issue?
An Apple forums post indicated a Neural Engine timeout where a command exceeded the 2,000-millisecond limit, though Apple did not officially disclose the cause in its release notes.
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