[Bug]: FluentProvider subtree permanently loses focus indicators #36809

Component

FluentProvider

Package version

 9.70.0

React version

18.3.1

Environment

System:
  OS: Windows 11 10.0.26200
Binaries:
  Node: 20.20.2
  Yarn: 1.22.22
  npm: 10.8.2
Browsers:
  Edge (Chromium): 153.0.4234.48
npmPackages:
  react: 16.14.0
  react-dom: 16.14.0
  @types/react: 17.0.43
  @types/react-dom: 16.9.24
  @fluentui/react-components: 9.70.0
  @fluentui/react-provider: 9.22.11
  @fluentui/react-tabster: 9.26.13
  @fluentui/react-link: 9.7.0
  @fluentui/react-button: 9.6.12
  keyborg: 2.6.0

Current Behavior

A FluentProvider can end up mounted with no focus-visible listener on its subtree at all. Every element inside it then takes real keyboard focus while keyborg is in keyboard-navigation mode, but never receives data-fui-focus-visible hence no focus indicator is ever drawn. It is permanent: no amount of tabbing restores it, and there is no warning.

In short, useFocusVisible binds the focus-visible polyfill once and never re-evaluates.

This occurs, when we are navigating from one service to another on redirect.

Potential cause here packages/react-components/react-tabster/src/hooks/useFocusVisible.ts.

Expected Behavior

Any element holding keyboard focus inside a mounted FluentProvider should receive data-fui-focus-visible and render a focus indicator, for the whole lifetime of that provider.

Reproduction

https://stackblitz.com/edit/qcbyxose-caieu9t2?file=src%2FApp.tsx

Steps to reproduce

1. Open the reproduction and click into the preview pane.
2. Tab through the "Control" row and the "Affected" row — both show focus rings, and the readout shows data-fui-focus-visible: YES.
3. Click "Remove outer provider".
4. Tab through the "Affected" row again.
5. The readout confirms focus really moves onto each Link and the Button, but data-fui-focus-visible is never set and no focus ring is drawn. No further tabbing, clicking, or key press ever restores it.

Are you reporting an Accessibility issue?

yes

Suggested severity

High - No workaround

Products/sites affected

Account.live.com

Are you willing to submit a PR to fix?

no

Validations

• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• The provided reproduction is a minimal reproducible example of the bug.