We are seeing a hard main-thread abort on iOS 26 during cold launch when VoiceOver (or another accessibility client) is active. about 1–7 seconds after process start. The crashing thread essentially shows only main from the app; the fatal path is entirely in system frameworks.
What happens is that UIAccessibility asks for an accessibility value, UIKit.axbundle handles it (on iOS 26.5 we exact-match-symbolicate this to -[_UITabButtonAccessibility accessibilityValue] + 120), then AXCoreUtilities safeSwiftValueForKey reflects a Swift object via Mirror / AttributeGraph. While copying an unowned field, the referent is already gone, so libswiftCore calls swift_abortRetainUnowned and the process dies. Not finding unowned in app source does not contradict this: the reflected object can live in system or SDK Swift state.
OS versions in the corpus: iOS 26.5 (23F77), 26.6 (23G71), and 26.6.1 (23G83). All reports load UIKit.axbundle. Launch-to-crash gaps range from roughly 1.4s to 7.3s. Most 26.6 samples share UIKit.axbundle binary UUID 387c6473…; we did not have matching Device Support for that build locally. One iOS 26.5 sample has UIKit.axbundle binary UUID dca69975… and AXCoreUtilities 78a7c163…, both exactly matching local Device Support, so atos on that sample is trustworthy.
On that iOS 26.5 sample (filename redacted), the symbolicated path is:
VoiceOver / AX
→ UIAccessibility (_iosAccessibilityAttributeValue → _accessibilityAXAttributedValue → _accessibilityPotentiallyAttributedValueForNonAttributedSelector)
→ UIKit.axbundle -[_UITabButtonAccessibility accessibilityValue] + 120
→ AXCoreUtilities (_AXSafeSwiftValueForKeyTm → safeSwiftValueForKey → _visitValueWithReflection)
→ AttributeGraph (AGTypeApplyFields2::Visitor::visit_field)
→ libswiftCore (swift_reflectionMirror_subscript → copyUnownedFieldContents → swift_unknownObjectUnownedLoadStrong → swift_abortRetainUnowned)
→ App: main only
Frame 32 math: runtime 0x2be49b130, slide base 0x2be3cf000, offset 0xCC130 → _UITabButtonAccessibility accessibilityValue + 120.
Questions for anyone hitting the same stack:
1.Is there already an Apple Feedback / radar for safeSwiftValueForKey + swift_abortRetainUnowned on iOS 26?
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