fix(session-replay): Extend masking and focus masking on sensitive information

[philprime]

📜 Description

This PR fixes several session replay masking issues and adds comprehensive test coverage for the redaction builder to prevent regressions.

💡 Motivation and Context

Fixed Masking Issues

SwiftUI.List Background Clipping Issue (#6292)
One screen in the dogfooding app Flinky had significant masking problems where the entire top half of a screen with SwiftUI.List was unmasked. Analysis revealed that _UICollectionViewListLayoutSectionBackgroundColorDecorationView has an extremely large frame (-20 -1135.33; 442 2336) that extends far beyond the visible list bounds, causing incorrect clipping calculations.

Implementation Improvements

String-Based Class Comparison

• Introduced ExtendedClassIdentifier to compare view classes by string description instead of direct class references
• Prevents triggering Objective-C +initialize on private UIKit classes when running off the main thread
• Supports optional layer class filtering for multi-purpose views (e.g., SwiftUI._UIGraphicsView)

Rendering & Layer Improvements

• Fixed sublayer rendering order by sorting layers by zPosition (with insertion order as tie-breaker)
• Switched from view-based to layer-based traversal for accurate presentation state
• Properly handle presentation layers during animations vs model layers

Edge Case Handling

• UISwitch subtree ignoring to prevent internal UIImageView from being incorrectly redacted
• UITextField placeholder handling via UITextFieldLabel detection
• SwiftUI.List background decoration view treated as special case (direct redact, no clip-out)
• Axis-aligned transform detection to optimize opaque view clipping
• Custom anchor point support in transform calculations

Test Coverage

Added 49 new tests to systematically verify:

• ExtendedClassIdentifier matching with layer filtering
• UIImageView boundary conditions (nil, 9x9, 10x10, 11x11 pixels)
• Hidden views and zero opacity handling
• Transform calculations with custom anchor points
• Region ordering and SwiftUI region prioritization
• Nested clipping regions
• Class hierarchy inheritance patterns
• iOS version-specific behavior (iOS 26 UISlider visual element)

Note: SwiftUI-specific integration tests (Text, Image, List, Label, Button) will be added in a follow-up PR.

💚 How did you test it?

Manual Testing

• Verified fix in Flinky app - SwiftUI.List screens now mask correctly
• Tested across iOS 15.5, 16.4, 17.5, 18.6, and 26.0 simulators

Automated Testing

• 49 new test cases added
• All 118+ tests passing (0 failures)
• Tests follow Arrange-Act-Assert pattern
• Standardized snapshot naming (masked/unmasked)

Files Changed

• Sources/Swift/Core/Tools/ViewCapture/SentryUIRedactBuilder.swift - Core fixes
• Tests/SentryTests/ViewCapture/SentryUIRedactBuilderTests+EdgeCases.swift - New (32 tests)
• Tests/SentryTests/ViewCapture/SentryUIRedactBuilderTests+Common.swift - Enhanced (8 new tests)
• Tests/SentryTests/ViewCapture/SentryUIRedactBuilderTests+UIKit.swift - Enhanced (5 new tests, removed 2 duplicates)
• Tests/SentryTests/ViewCapture/SentryUIRedactBuilderTests+SpecialViews.swift - Updated naming

📝 Checklist

You have to check all boxes before merging:

• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• I updated the wizard if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.
• No breaking change for hybrid SDKs or communicated to hybrid SDKs.

[codecov]

Codecov Report

❌ Patch coverage is 89.78495% with 19 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.398%. Comparing base (24a1eec) to head (352a044).
⚠️ Report is 3 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...Core/Tools/ViewCapture/SentryUIRedactBuilder.swift	89.673%	19 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #6292       +/-   ##
=============================================
- Coverage   85.458%   85.398%   -0.061%     
=============================================
  Files          451       451               
  Lines        27328     27428      +100     
  Branches     11917     11936       +19     
=============================================
+ Hits         23354     23423       +69     
+ Misses        3929      3721      -208     
- Partials        45       284      +239     

Files with missing lines	Coverage Δ
...ft/Core/Tools/ViewCapture/SentryRedactRegion.swift	100.000% <ø> (ø)
...ore/Tools/ViewCapture/SentryViewPhotographer.swift	88.888% <100.000%> (+0.653%)	⬆️
...Core/Tools/ViewCapture/SentryUIRedactBuilder.swift	87.662% <89.673%> (-9.957%)	⬇️

... and 44 files with indirect coverage changes

---

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[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1217.75 ms	1258.41 ms	40.66 ms
Size	23.75 KiB	1.01 MiB	1016.21 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
9264ee8	1233.15 ms	1250.02 ms	16.87 ms
07d7e83	1211.71 ms	1240.08 ms	28.37 ms
119ab1c	1226.79 ms	1254.55 ms	27.76 ms
66147d5	1234.45 ms	1268.45 ms	34.00 ms
fa9a4bb	1217.91 ms	1248.72 ms	30.81 ms
be882e4	1199.35 ms	1231.20 ms	31.86 ms
d7461dc	1233.69 ms	1255.29 ms	21.60 ms
f97a070	1218.88 ms	1253.12 ms	34.24 ms
339539a	1219.58 ms	1254.63 ms	35.05 ms
26f7b17	1218.47 ms	1253.82 ms	35.35 ms

App size

Revision	Plain	With Sentry	Diff
9264ee8	23.75 KiB	913.09 KiB	889.34 KiB
07d7e83	23.75 KiB	913.27 KiB	889.52 KiB
119ab1c	23.75 KiB	993.70 KiB	969.95 KiB
66147d5	23.74 KiB	1.01 MiB	1008.77 KiB
fa9a4bb	23.75 KiB	986.91 KiB	963.16 KiB
be882e4	23.75 KiB	946.69 KiB	922.94 KiB
d7461dc	23.75 KiB	874.45 KiB	850.70 KiB
f97a070	23.75 KiB	858.68 KiB	834.93 KiB
339539a	23.75 KiB	968.24 KiB	944.50 KiB
26f7b17	23.75 KiB	960.93 KiB	937.19 KiB

Previous results on branch: philprime/fix-masking

Startup times

Revision	Plain	With Sentry	Diff
bb49b7a	1229.51 ms	1260.31 ms	30.80 ms
9919db5	1230.88 ms	1262.00 ms	31.12 ms
0f2e562	1225.90 ms	1257.69 ms	31.80 ms
d70d220	1238.80 ms	1262.08 ms	23.29 ms
a126606	1218.71 ms	1248.26 ms	29.55 ms
8d1f930	1241.27 ms	1263.71 ms	22.44 ms
5a94e38	1190.59 ms	1244.60 ms	54.01 ms
5a4767b	1206.00 ms	1238.21 ms	32.21 ms
8d12b30	1222.56 ms	1251.98 ms	29.42 ms

App size

Revision	Plain	With Sentry	Diff
bb49b7a	23.75 KiB	1014.06 KiB	990.32 KiB
9919db5	23.75 KiB	1.02 MiB	1017.54 KiB
0f2e562	23.75 KiB	1.02 MiB	1018.58 KiB
d70d220	23.75 KiB	994.81 KiB	971.06 KiB
a126606	23.75 KiB	1.02 MiB	1018.04 KiB
8d1f930	23.75 KiB	981.78 KiB	958.03 KiB
5a94e38	23.75 KiB	1.00 MiB	1006.18 KiB
5a4767b	23.75 KiB	1.01 MiB	1006.46 KiB
8d12b30	23.75 KiB	1.02 MiB	1019.75 KiB

[philipphofmann]

Thanks, this looks way better than before. I gave the tests just a quick pass; they look good, but I found a couple of minor things to improve. Thanks @philprime for cleaning this up.

[cursor]

Bug: Incorrect Transform Reference in Safari View Controller

In the assertSFSafariViewControllerRegions function for iOS 15/16, the assertion for placeholderRegion.transform incorrectly references toolbarRegion.transform.

 

[philipphofmann]

Thanks, LGTM

[philprime]

FYI @philipphofmann @itaybre @noahsmartin this PR is done, but the CI is failing because snapshot tests of standard components are flaky, especially as we are using a Beta of Xcode 26.1

[philipphofmann]

FYI @philipphofmann @itaybre @noahsmartin this PR is done, but the CI is failing because snapshot tests of standard components are flaky, especially as we are using a Beta of Xcode 26.1

@philprime what do you suggest to solve this problem?

[philprime]

I am going to split this up into a PR stack with a PR per test-file so we can merge them individually instead of keeping this open forever

[philprime]

• test(session-replay): Add masking tests for special views #6571
• test(session-replay): Add masking tests for UIKit views #6570
• test(session-replay): Add masking tests for edge cases #6569
• test(session-replay): Add masking tests for React Native views #6568
• test(session-replay): Add masking tests for common cases #6567
• fix(session-replay): Extend masking and focus masking on sensitive information #6292 👈 (View in Graphite)
• main

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