[iOS 26] Fix tab bar ghosting when navigating from modal to tabbed Shell content

[SubhikshaSf4851]

Note

Are you waiting for the changes in this PR to be merged?
It would be very helpful if you could test the resulting artifacts from this PR and let us know in a comment if this change resolves your issue. Thank you!

Root Cause

iOS 26 introduced the Liquid Glass rendering system for the tab bar. In ShellItemTransition, setting newView.Alpha = 0 before the cross-fade animation causes iOS 26 to composite the Liquid Glass tab bar icons while the parent view is at zero opacity. When the animation restores alpha = 1, the glass pill appears with the selected tab icon missing because the Liquid Glass layer already cached its content at zero opacity.

Description of Change

• Updated ShellItemTransition.cs to skip setting newView.Alpha = 0 on iOS 26+, preventing
  Liquid Glass tab bar icons from being composited while the parent view is transparent.
• The cross-fade animation still runs on iOS 26+ (animating from the default alpha = 1),
  so the visual transition is preserved.
• Added missing using System; directive required for OperatingSystem.IsIOSVersionAtLeast(26).

Test coverage for the regression:

• Introduced a new test case in TestCases.HostApp (Issue34143.cs) that reproduces the navigation scenario and ensures the tab bar renders correctly after navigating from a modal.
• Added a UI test (TestCases.Shared.Tests/Tests/Issues/Issue34143.cs) to automate validation that the tab bar is visible and interactable after the specific navigation flow, preventing regressions.

Issues Fixed

Fixes #34143

Tested the behaviour in the following platforms

• Windows
• Android
• iOS
• Mac

Screenshot

Before Issue Fix	After Issue Fix

[github-actions]

🚀 Dogfood this PR with:

⚠️ WARNING: Do not do this without first carefully reviewing the code of this PR to satisfy yourself it is safe.

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[sheiksyedm]

/azp run maui-pr-uitests , maui-pr-devicetests

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[Copilot]

Pull request overview

This PR fixes a tab bar ghosting issue on iOS 26 caused by the new Liquid Glass rendering system. When navigating from a modal to tabbed Shell content using GoToAsync, tab bar icons would appear missing or ghosted. The root cause is that setting newView.Alpha = 0 before the cross-fade animation in ShellItemTransition causes iOS 26 to composite the Liquid Glass tab bar icons while the parent view is at zero opacity, resulting in incorrect rendering when alpha is restored to 1.

Changes:

• Modified ShellItemTransition.cs to skip setting alpha to 0 on iOS 26+, allowing the cross-fade animation to start from the default alpha=1
• Added comprehensive UI test reproducing the modal-to-tabs navigation scenario
• Added snapshot images for iOS, iOS 26, and Android platforms

Reviewed changes

Copilot reviewed 3 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/Controls/src/Core/Compatibility/Handlers/Shell/iOS/ShellItemTransition.cs	Added iOS 26+ version check to skip setting newView.Alpha = 0, fixing Liquid Glass tab bar icon compositing issue
src/Controls/tests/TestCases.HostApp/Issues/Issue34143.cs	Created test host app with Shell structure: Home page → Modal → TabBar navigation flow using TestShell base class
src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue34143.cs	Added UI test verifying tab bar visibility after modal-to-tabs navigation via GoToAsync
src/Controls/tests/TestCases.iOS.Tests/snapshots/ios/TabBarShouldBeVisibleAfterNavigatingFromModalViaGoToAsync.png	Snapshot for iOS (pre-26) showing correct tab bar rendering
src/Controls/tests/TestCases.iOS.Tests/snapshots/ios-26/TabBarShouldBeVisibleAfterNavigatingFromModalViaGoToAsync.png	Snapshot for iOS 26+ showing correct Liquid Glass tab bar rendering
src/Controls/tests/TestCases.Android.Tests/snapshots/android/TabBarShouldBeVisibleAfterNavigatingFromModalViaGoToAsync.png	Snapshot for Android showing tab bar baseline (not affected by iOS 26 issue)

[kubaflo]

🤖 AI Summary

📊 Expand Full Review

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🔍 Pre-Flight — Context & Validation

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📝 Review Session — 26version snapshot updated · c0cd9b2

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Issue: #34143 - [iOS] Tab bar ghosting issue on iOS 26 (liquid glass)
PR: #34254 - [iOS 26] Fix tab bar ghosting when navigating from modal to tabbed Shell content
Platforms Affected: iOS (specifically iOS 26+), possibly MacCatalyst 26+
Labels: area-controls-shell, community ✨, partner/syncfusion, version/iOS-26
Files Changed: 1 implementation file, 2 test files, 3 snapshot files

Issue Summary

On iOS 26, when using the new Liquid Glass rendering for the tab bar, navigating from a modal via Shell.Current.GoToAsync() to a Shell tab causes "ghosting": the selected tab bar icon becomes invisible/empty.

Root cause (per PR author): ShellItemTransition.cs sets newView.Alpha = 0 before the cross-fade animation. iOS 26's Liquid Glass composites the tab bar icons at zero alpha, and when alpha is restored to 1, the selected icon is missing because it was cached at zero opacity.

Workaround (from issue): Enable UI compatibility mode in Info.plist, or use PushAsync instead of PushModalAsync.

Fix Files

• src/Controls/src/Core/Compatibility/Handlers/Shell/iOS/ShellItemTransition.cs (+10/-1)

Test Files

• src/Controls/tests/TestCases.HostApp/Issues/Issue34143.cs (+149 lines, new)
• src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue34143.cs (+34 lines, new)

Snapshot Files (new)

• TestCases.iOS.Tests/snapshots/ios-26/TabBarShouldBeVisibleAfterNavigatingFromModalViaGoToAsync.png
• TestCases.iOS.Tests/snapshots/ios/TabBarShouldBeVisibleAfterNavigatingFromModalViaGoToAsync.png
• TestCases.Android.Tests/snapshots/android/TabBarShouldBeVisibleAfterNavigatingFromModalViaGoToAsync.png ⚠️ (suspicious — issue is iOS-only)

Key Findings / Issues to Investigate

File:Line	Finding	Status
ShellItemTransition.cs:23	Missing IsMacCatalystVersionAtLeast(26) check — every other iOS 26 check in the same folder pairs both (ShellPageRendererTracker.cs:291, 342, 736; ShellSectionRenderer.cs:809; NavigationRenderer.cs:1621, 1728, 2183, 2287)	⚠️ BUG
Issue34143.cs (SharedTests)	No platform guard — test uses VerifyScreenshot() and the Android snapshot file was included. The HostApp has PlatformAffected.iOS but the NUnit test class has no platform attribute	⚠️ REVIEW
TestCases.Android.Tests/snapshots/android/...	An Android snapshot was added for an iOS-only issue	⚠️ SUSPICIOUS

Existing Review Feedback

Reviewer	Comment	Status
copilot-pull-request-reviewer	Line 23: "MacCatalyst version check is missing. Based on codebase pattern, iOS 26+ checks should also include MacCatalyst 26+. Suggests: if (!OperatingSystem.IsIOSVersionAtLeast(26) && !OperatingSystem.IsMacCatalystVersionAtLeast(26))"	⚠️ UNRESOLVED

Fix Candidates

#	Source	Approach	Test Result	Files Changed	Notes
PR	PR #34254	Skip newView.Alpha = 0 on iOS 26+ only (missing MacCatalyst check)	⏳ PENDING (Gate)	ShellItemTransition.cs (+10/-1)	Original PR — missing MacCatalyst guard

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🚦 Gate — Test Verification

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📝 Review Session — 26version snapshot updated · c0cd9b2

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Result: ✅ PASSED
Platform: ios
Mode: Full Verification (RequireFullVerification)
TestFilter: Issue34143

• Tests FAIL without fix ✅ (VisualRegressionTester detected the ghosting issue)
• Tests PASS with fix ✅ (PR fix resolves the problem)

The test case TabBarShouldBeVisibleAfterNavigatingFromModalViaGoToAsync correctly catches the iOS 26 Liquid Glass tab bar ghosting regression.

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🔧 Fix — Analysis & Comparison

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📝 Review Session — 26version snapshot updated · c0cd9b2

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Fix Candidates

#	Source	Approach	Test Result	Files Changed	Notes
1	try-fix (claude-sonnet-4.6)	Reverse fade direction — animate oldView alpha 1→0 instead of newView 0→1	❌ FAIL	ShellItemTransition.cs	Why: Liquid Glass compositing at UITabBarController level is independent of content view transitions
2	try-fix (claude-opus-4.6)	Add IsMacCatalystVersionAtLeast(26) alongside IsIOSVersionAtLeast(26), matching codebase pattern	✅ PASS	ShellItemTransition.cs	Simplest fix, matches all other iOS 26 checks in codebase
3	try-fix (gpt-5.2)	Snapshot-based cross-fade — animate snapshot overlays, real views stay at alpha=1 throughout	✅ PASS	ShellItemTransition.cs	More complex, preserves visual cross-fade on iOS 26+
4	try-fix (gpt-5.3-codex)	UIView.Transition + CrossDissolve + Hidden flag instead of alpha	❌ FAIL	ShellItemTransition.cs	Why: Hidden flag triggers similar Liquid Glass compositing issue
5	try-fix (gemini-3-pro-preview)	CALayer.Opacity = 0 instead of UIView.Alpha	❌ FAIL	ShellItemTransition.cs	Why: UIView.Alpha and CALayer.Opacity treated identically by rendering engine
6	try-fix (claude-opus-4.6)	Snapshot overlay + CAShapeLayer mask wipe on snapshot (real views always alpha=1)	✅ PASS	ShellItemTransition.cs	Works, but overly complex for this fix
PR	PR #34254	Skip newView.Alpha = 0 on iOS 26+ — missing MacCatalyst 26+ check	✅ PASS (Gate)	ShellItemTransition.cs (+10/-1)	Original PR — correct approach but incomplete platform guard

Cross-Pollination Summary

Round	Model	Response
2	claude-sonnet-4.6	NO NEW IDEAS
2	claude-opus-4.6	NEW IDEA: CAShapeLayer mask wipe
2	gpt-5.2	NEW IDEA: Alpha-free wipe/reveal
2	gpt-5.3-codex	NEW IDEA: Transform/position-based reveal
2	gemini-3-pro-preview	NEW IDEA: Scale/zoom transform
3	claude-sonnet-4.6	NO NEW IDEAS
3	claude-opus-4.6	NO NEW IDEAS
3	gpt-5.2	NEW IDEA: CATransaction.DisableActions wrapper
3	gpt-5.3-codex	NEW IDEA: Pure transform slide handoff
3	gemini-3-pro-preview	NEW IDEA: Slide translation

Round 3 max rounds reached. All Round 3 ideas are variants of the same theme (geometry-based animation keeping views at alpha=1), which is already covered by Attempts 3 and 6.

Exhausted: Yes (max 3 rounds reached)

Key Insight Confirmed: Liquid Glass on iOS/MacCatalyst 26+ requires the tab bar icons to be fully visible (alpha=1, unmasked) from the very first frame the view enters the hierarchy. Any form of initial transparency or masking — whether UIView.Alpha, CALayer.Opacity, UIView.Hidden, or CALayer mask — triggers the ghosting bug.

Selected Fix: PR's fix is the correct approach — the only deficiency is missing IsMacCatalystVersionAtLeast(26). The fix should match the established codebase pattern:

if (!(OperatingSystem.IsIOSVersionAtLeast(26) || OperatingSystem.IsMacCatalystVersionAtLeast(26)))
{
    newView.Alpha = 0;
}

Reason: Attempt 2 validates this exact fix. It's the simplest correct solution (1 additional method call) that matches 6+ other instances in the same codebase. Attempts 3 and 6 are passing alternatives but significantly more complex for no additional benefit.

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📋 Report — Final Recommendation

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📝 Review Session — 26version snapshot updated · c0cd9b2

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⚠️ Final Recommendation: REQUEST CHANGES

Summary

PR #34254 correctly identifies and targets the root cause of the iOS 26 Liquid Glass tab bar ghosting bug. The fix is sound in principle: skip setting newView.Alpha = 0 before the cross-fade so the Liquid Glass compositor sees the tab bar icons at full opacity from frame 1. However, the fix is incomplete — it checks only IsIOSVersionAtLeast(26) while missing IsMacCatalystVersionAtLeast(26), inconsistent with every other iOS 26 version check in the same codebase. This was independently validated by try-fix Attempt 2, which confirmed the MacCatalyst-inclusive fix also passes the tests.

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Root Cause

iOS 26 introduced Liquid Glass rendering for the tab bar. The Liquid Glass compositor caches the selected tab bar icon when the parent UIView is first inserted into the view hierarchy. If the parent view has alpha = 0 at that moment, the icon is cached at zero opacity. When alpha is later restored to 1, the pill selection indicator renders correctly but the icon remains invisible ("ghosted") because it was already composited.

Key insight: The Liquid Glass compositor captures tab bar icons on the first frame the view enters the hierarchy, so the view must be at alpha = 1 from the very beginning.

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Code Review Findings

🔴 Critical Issues

Missing MacCatalyst 26+ version check

• File: src/Controls/src/Core/Compatibility/Handlers/Shell/iOS/ShellItemTransition.cs:23
• Problem: The fix uses if (!OperatingSystem.IsIOSVersionAtLeast(26)) but MacCatalyst 26 also uses Liquid Glass for the tab bar. Every other iOS 26 version guard in the same directory (ShellPageRendererTracker.cs:291,342,736, ShellSectionRenderer.cs:809, ShellItemRenderer.cs:133) and in NavigationRenderer.cs:1621,1728,2183,2287 always pairs both:

  OperatingSystem.IsIOSVersionAtLeast(26) || OperatingSystem.IsMacCatalystVersionAtLeast(26)

• Required fix:

  if (!(OperatingSystem.IsIOSVersionAtLeast(26) || OperatingSystem.IsMacCatalystVersionAtLeast(26)))
  {
      newView.Alpha = 0;
  }

• Confirmed by: Copilot review comment (existing), try-fix Attempt 2 (independently validated — tests pass with this fix).

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🟡 Suggestions

Suspicious Android snapshot file

• File: src/Controls/tests/TestCases.Android.Tests/snapshots/android/TabBarShouldBeVisibleAfterNavigatingFromModalViaGoToAsync.png
• Problem: The issue is iOS-only (label: platform/ios, HostApp attribute: PlatformAffected.iOS). An Android snapshot suggests the test was run on Android and a baseline was captured — but the bug doesn't affect Android. This snapshot will be compared against Android test runs, potentially masking future Android regressions in the Shell tab bar.
• Recommendation: Remove this Android snapshot if the test is not intended to run on Android. If the test should run cross-platform, add platform-specific documentation explaining why.

PR description accuracy

• File: PR body
• Problem: "The cross-fade animation still runs on iOS 26+ (animating from the default alpha = 1)" is misleading. Since newView.Alpha starts at 1 and the animation sets it to 1, the animation is a no-op on iOS 26+. There is effectively no visual cross-fade between tab items on iOS 26+.
• Recommendation: Update to: "On iOS 26+, the alpha-based cross-fade is skipped to avoid the Liquid Glass ghosting issue; the tab switch is visually instant on iOS 26+."

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✅ What Looks Good

• Core fix approach is correct: prevent alpha = 0 from being set on iOS 26+ Liquid Glass systems
• The using System; directive is correctly added for OperatingSystem.IsIOSVersionAtLeast
• Test coverage is well-structured: HostApp page with multiple tabs, modal navigation, and VerifyScreenshot() validation
• Two iOS snapshot baselines provided: ios/ and ios-26/ for different OS versions
• PR description includes root cause, before/after screenshots, and description of change
• NOTE block is present at the top of the description

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Title & Description

Title: ✅ [iOS 26] Fix tab bar ghosting when navigating from modal to tabbed Shell content
Good — platform prefix, describes behavior not issue number, informative.

Description: The existing description is well-structured and accurate. Only two enhancements recommended:

1. Fix the "cross-fade still runs" claim to reflect that it's a no-op on iOS 26+
2. Add a "What NOT to Do" note for future agents

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Fix Candidates Summary

#	Approach	Result	Notes
1	Reverse fade (oldView 1→0)	❌ FAIL	Liquid Glass compositing is UITabBarController-level, independent of content view
2	Add MacCatalystVersionAtLeast(26) check	✅ PASS	Minimal correct fix — matches codebase pattern
3	Snapshot cross-fade (real views at alpha=1)	✅ PASS	More complex, preserves visual transition on iOS 26+
4	UIView.Transition + CrossDissolve + Hidden	❌ FAIL	Hidden flag still triggers Liquid Glass issue
5	CALayer.Opacity instead of UIView.Alpha	❌ FAIL	Identical to UIView.Alpha at rendering level
6	Snapshot overlay + CAShapeLayer mask wipe	✅ PASS	Overly complex for this fix
PR	Original PR (iOS-only check)	✅ PASS (Gate)	Correct approach, but missing MacCatalyst guard

Selected fix: PR's fix with the MacCatalyst guard added (Attempt 2 pattern). One line change from PR's current state.

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📋 Expand PR Finalization Review

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Title: ✅ Good

Current: [iOS 26] Fix tab bar ghosting when navigating from modal to tabbed Shell content

Description: ✅ Good

Description needs updates. See details below.

✨ Suggested PR Description

[!NOTE]
Are you waiting for the changes in this PR to be merged?
It would be very helpful if you could test the resulting artifacts from this PR and let us know in a comment if this change resolves your issue. Thank you!

Root Cause

iOS 26 introduced the Liquid Glass rendering system for the tab bar. In ShellItemTransition, newView.Alpha = 0 is set before the cross-fade animation begins so the new view can fade in from transparent to opaque. On iOS 26, this causes the Liquid Glass compositor to cache the tab bar icons while the parent view is at zero alpha. When alpha is later restored to 1, the glass pill appears with the selected tab icon missing — the compositor already rendered it at zero opacity.

Description of Change

Updated ShellItemTransition.cs to skip setting newView.Alpha = 0 on iOS 26+:

• On iOS 26+, newView.Alpha = 0 is not set. The new view appears at its default alpha = 1, which means no fade-in animation occurs on iOS 26+ — this is a deliberate trade-off to avoid the Liquid Glass compositing bug.
• On iOS 25 and earlier, behavior is unchanged: newView.Alpha = 0 is set and the cross-fade animation runs as before.
• Added using System; required by OperatingSystem.IsIOSVersionAtLeast(26).

Platforms affected: iOS only. The fix file is in Compatibility/Handlers/Shell/iOS/ and OperatingSystem.IsIOSVersionAtLeast returns false on all non-iOS platforms.

Test Coverage

• HostApp page (Issue34143.cs): Reproduces the exact navigation scenario — Home page → Push Modal → GoToAsync to Tab 1.
• UI test (TestCases.Shared.Tests/Tests/Issues/Issue34143.cs): Automates the navigation flow and calls VerifyScreenshot() to catch regressions.
• Snapshots added: ios-26/, ios/, android/ — covering the primary affected platform and confirming no regression on Android.

Issues Fixed

Fixes #34143

Platforms Tested

• iOS (primary — fix targets iOS 26 Liquid Glass tab bar)
• Android (UI test baseline snapshot captured)
• Windows
• Mac

Code Review: ✅ Passed

Code Review — PR #34254

🟡 Suggestions

1. Animation behavior on iOS 26+ is a silent regression

File: src/Controls/src/Core/Compatibility/Handlers/Shell/iOS/ShellItemTransition.cs

Problem: The fix skips newView.Alpha = 0 on iOS 26+. Assuming the rest of Transition() contains a UIView.Animate block that animates alpha from 0 → 1, skipping the initial assignment means iOS 26+ gets no fade-in animation (the view appears instantly at full opacity). The PR description calls this "the cross-fade animation still runs", but it does not — 1 → 1 is a no-op animation.

This is an acceptable trade-off (no ghosting bug > no animation), but:

• The comment should not claim the animation is preserved
• Ideally the code could use a different animation approach on iOS 26+ (e.g., brief scale or opacity starting near-1) to preserve some visual transition

Recommendation: Update the inline comment and PR description to accurately state that the fade-in animation is skipped on iOS 26+ as a deliberate trade-off. Example:

// On iOS 26+, setting newView.Alpha = 0 before the fade-in causes Liquid Glass
// tab bar icons to composite at zero opacity, resulting in missing tab icons.
// We skip the initial alpha=0 on iOS 26+, which means there is no fade-in
// animation on iOS 26+ — this is intentional to avoid the rendering issue.
if (!OperatingSystem.IsIOSVersionAtLeast(26))
{
    newView.Alpha = 0;
}

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2. Verbose inline comment

File: src/Controls/src/Core/Compatibility/Handlers/Shell/iOS/ShellItemTransition.cs

Problem: The 4-line comment beginning with "On iOS 26+, setting newView.Alpha = 0..." is slightly redundant in its last clause ("Skip setting alpha to 0 so the tab bar view stays at its default alpha=1 when iOS 26 composites its icons") — the if block itself makes that clear.

Recommendation: Condense to 2–3 lines (see suggestion above).

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✅ Looks Good

• Fix is minimal and targeted: Only 10 added lines in the actual fix, with no structural changes.
• OperatingSystem.IsIOSVersionAtLeast(26): Correct .NET API for version guarding. Returns false on non-iOS platforms, so no platform #if guard is needed (the file is already iOS-only by path).
• using System; addition: Correct — OperatingSystem lives in System.
• HostApp test page (Issue34143.cs): Well-structured. Uses TestShell base class (correct pattern), has proper AutomationId attributes, and reproduces the exact navigation scenario from the issue.
• UI test (TestCases.Shared.Tests/Tests/Issues/Issue34143.cs): Follows standard patterns (_IssuesUITest, [Category(UITestCategories.Shell)]). Navigation flow correctly mirrors the repro steps from issue [iOS] Tab bar ghosting issue on iOS 26 (liquid glass) #34143.
• Snapshots committed for Android, iOS, and iOS-26: Appropriate. The test runs on all platforms via the Shared.Tests project; Android snapshot confirms no regression on that platform.
• PlatformAffected.iOS on HostApp [Issue] attribute: Correct — the issue is iOS-specific.

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[kubaflo]

Hi! Could you please apply suggestions from the AI Summary?

[SubhikshaSf4851]

@kubaflo I have modified the changes

[sheiksyedm]

/azp run maui-pr-uitests

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