iOS 27: tab selection flickers on long-press release with the doc.text SF Symbol

The reproduction is in packages/example-shared/src/Examples/Roles.tsx; start by running the iOS 27 scenario with doc.text and compare it with document or document.fill. Then trace the native image/appearance update path implicated by the symbol-dependent behavior; done means the original doc.text case no longer flickers while Search selection settles once.

Summary

On iOS 27, the Roles example's tab bar visibly flickers after long-pressing and releasing a tab. Recordings show the selection highlight briefly moving back toward Albums before settling on Search as the destination content appears.

The smallest verified change is Article's SF Symbol: changing only doc.text to document or document.fill avoids the release flicker. Restoring doc.text brings it back. This establishes a symbol-dependent trigger in this configuration, not the underlying native cause.

Environment

• iOS 27.0, iPhone 18 Pro simulator
• Local development build of react-native-bottom-tabs
• Example: packages/example-shared/src/Examples/Roles.tsx
• Verified with agent-device 0.20.10 and recorded 1,200 ms long presses
• Reporter observes the issue only on iOS 27; earlier iOS versions were not independently retested during this isolation

Reproduction

1. Open Roles with the Search role selected and experimental baked tint colors off.
2. Start on Article.
3. Long-press Search for about 1.2 seconds, then release.
4. Observe the second highlight movement/flicker as Search content appears.
5. Change only Article's icon as shown below, reload, and repeat: the release flicker is no longer observed.
6. Restore doc.text, reload, and repeat: the flicker returns.

 {
   key: 'article',
   title: 'Article',
-  focusedIcon: { sfSymbol: 'doc.text' },
+  focusedIcon: { sfSymbol: 'document' },
 }

Expected: selection settles smoothly on Search without replaying the highlight movement on release.

Actual: with doc.text, the highlight briefly returns toward Albums before settling on Search.

Isolation results

Each change below was compared with the original Roles configuration on iOS 27.

Copying SFSymbols' routes also avoids the glitch. The one-line Article symbol substitution achieves that without changing Search's role, magnifying-glass icon, testID, route keys, or tint props. Earlier separate tests removing custom tint props or enabling sidebarAdaptable did not remove the flicker. Baked tint colors were off in these recordings.

The earlier testID/identifier hypothesis was ruled out. It remains unverified whether the underlying cause is in SwiftUI/UIKit or the library's native image/appearance updates. The recordings alone do not establish a React remount or rerender as the cause. All temporary source edits were restored after verification.

Videos

Original doc.text — flicker reproduces

https://github.com/user-attachments/assets/21d2ccdc-5590-4f04-9800-a5c12d99cf75

Only Article changed to document — no release flicker observed

https://github.com/user-attachments/assets/a7d5a853-af4e-481a-b432-d783ecae1ba8

Original reporter recording — Roles versus SFSymbols

https://github.com/user-attachments/assets/0e4d7971-360e-486a-9ecb-d3177b30ba13