Troubleshoot - Blank page opens when opening test tools via CMD+D

[vincdargento]

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Version Number: 9.3.41-0
Reproducible in staging?: Yes
Reproducible in production?: No
If this was caught during regression testing, add the test name, ID and link from BrowserStack: #79834
Email or phone of affected tester (no customers): sdjsdjosijnsodiosd@gmail.com
Issue reported by: Applause Internal Team
Bug source: Exploratory - Significant User Experience Deterioration
Device used: Mac 26.2 / Chrome
App Component: Other

Action Performed:

1. Go to staging.new.expensify.com
2. Open test tools via CMD+D.

Expected Result:

Test tools modal will open.

Actual Result:

A blank page opens.

Workaround:

Unknown

Platforms:

• Android: App
• Android: mWeb Chrome
• iOS: App
• iOS: mWeb Safari
• iOS: mWeb Chrome
• Windows: Chrome
• MacOS: Chrome / Safari

Screenshots/Videos

bug.mp4

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[melvin-bot]

You have been assigned to this deploy blocker because you recently merged this PR: #79834

[melvin-bot]

💬 A slack conversation has been started in #expensify-open-source

[github-actions]

👋 Friendly reminder that deploy blockers are time-sensitive ⏱ issues! Check out the open `StagingDeployCash` deploy checklist to see the list of PRs included in this release, then work quickly to do one of the following:

1. Identify the pull request that introduced this issue and revert it.
2. Find someone who can quickly fix the issue.
3. Fix the issue yourself.

[OSBotify]

🔍 Investigation Summary

Classification: Frontend bug
Causing PR: #79834 - "fix: [Web] Focus restoration mechanism on back navigation (#76921)" by @mavrickdeveloper (High confidence)
Related Issues: #76921

Recommendation: REVERT

PR #79834 introduced a new NavigationFocusManager system to handle keyboard focus restoration during back navigation. This appears to be interfering with the TestToolsModal rendering, causing a blank page instead of the modal content when opening test tools via CMD+D.

Labels: Keeping DeployBlockerCash (App deploy blocker - frontend fix required). DeployBlocker label is not present on this issue.

📋 Detailed Analysis

Evidence

• Issue only reproduces on staging (v9.3.41-0), not production
• PR fix: [Web] Focus restoration mechanism on back navigation (#76921) #79834 is included in staging deploy (position 55 in chronological order)
• PR fix: [Web] Focus restoration mechanism on back navigation (#76921) #79834 introduced NavigationFocusManager and modified FocusTrapForScreen
• TestToolsModalNavigator wraps content in FocusTrapForScreens which uses the modified component
• melvin-bot automatically assigned this to the PR fix: [Web] Focus restoration mechanism on back navigation (#76921) #79834 author

Verification

Files affected by the bug:

• src/libs/Navigation/AppNavigator/Navigators/TestToolsModalNavigator.tsx
• src/components/TestToolsModalPage.tsx

PR #79834 modifies:

• src/components/FocusTrap/FocusTrapForScreen/index.web.tsx (complete rewrite)
• src/libs/NavigationFocusManager/ (new module, 825 lines)
• src/App.tsx (initializes NavigationFocusManager)

Root Cause

The new FocusTrapForScreen adds complex focus capture/restoration logic. The test tools modal triggers edge case behavior:

1. CMD+D calls toggleTestToolsModal()
2. TestToolsModalNavigator mounts with FocusTrapForScreen wrapper
3. FocusTrapForScreen initialFocus function may return invalid element or cause bad focus trap state
4. This prevents modal content from rendering, showing blank page

Key suspicious code:

• routeKey guards for undefined (line 22)
• wasNavigatedTo/shouldRestoreFocusWithoutTrap conditional logic
• Fresh mount detection for non-persistent screens (lines 111-115)

[vincdargento]

This issue is reproducible on every snapshot build, no culprit PR was found.