Overview
- Apple released a test update labeled iOS 26.3 (a) with equivalent macOS Tahoe 26.3 builds for developers and public beta testers to validate the delivery system.
- The release notes state the update is for testing only and contains no security fixes.
- Testers manage these updates in Settings > Privacy & Security > Background Security Improvements, with an option to remove an installed update that triggers a device restart.
- Background Security Improvements are designed to replace Rapid Security Response by enabling targeted protections outside regular software updates.
- Apple cautions that rare compatibility issues may occur and says problematic updates can be temporarily pulled and refined for reissue, with observers suggesting broader deployment could follow this test.