Apple on Thursday released iOS 18.6.1 and watchOS 11.6.1, restoring blood-oxygen measurement to Apple Watch Series 9, Series 10 and Ultra 2 units sold in the United States. The company said U.S. Customs cleared a redesigned version of the feature, which had been absent from newer watches for more than 18 months. Under the workaround, the watch’s sensors collect pulse-oximetry data, but calculation and display now occur on the paired iPhone’s Health app rather than on the watch itself. The change lets Apple comply with a U.S. International Trade Commission order that barred imports of devices offering on-device readings. Apple originally disabled blood-oxygen tracking in January 2024 after the ITC ruled the technology infringed patents owned by medical-device maker Masimo Corp. The dispute had forced the company to pull or modify U.S. models, while versions sold abroad kept the capability. The software update restores a marquee health metric weeks before the expected debut of Apple Watch Series 11. Masimo shares fell roughly 5% after the announcement; Apple’s stock was little moved.