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fix(mobile): Duo feed scroll indicator stays left of the vertical bar while streaming - #36063
On an unfolded iPhone Duo, the thread feed's scroll indicator flickers during a streaming run. It jumps between its correct place, left of the vertical bar, and the screen edge under the bar.
T3ScrollEdgeBleedView widens the feed's scroll view under the bar and sets verticalScrollIndicatorInsets.right so the indicator stays clear of it. Fabric's RCTScrollViewComponentView (RN 0.88.1, updateProps) assigns the whole scrollIndicatorInsets (both axes, right = 0) whenever that prop changes. The bleed view only restored the inset on its own layoutSubviews, so for those frames the indicator sat under the bar.
That prop changes far more often than ThreadFeed's { top, bottom: 0 } suggests. KeyboardAwareLegendList renders react-native-keyboard-controller's ScrollViewWithBottomPadding, which sends scrollIndicatorInsets through Reanimated animatedProps with bottom = keyboard + anchored end space. That end space shrinks as a streaming reply grows, so the prop changes over and over during a run. Header show/hide also changes top.
Fix
While bleeding, the bleed view KVO-observes the scroll view's indicator insets and puts right back right away, in the same main-thread pass as React Native's write. Off the Duo, bleed is zero: no observation is installed and nothing is written, same as before. Observations are dropped when the bleed ends or the view detaches.
Verification
vp run check:changed: format and typecheck pass. No Swift toolchain on the Linux dev box, so this PR's iOS dev-client build and SwiftLint in CI are the compile check.
No before/after device capture. I leased an iPhone Duo (iOS 27.2) simulator from the device pool and ran the app unfolded against a Replay-provider thread. But every available dev client, including this repo's mobile-dev-client workflow on macos-26, is built with the iOS 26.5 SDK. On the Duo that runs letterboxed in compatibility mode, and the bleed view's vertical-bar code (#if canImport(UIKit, _version: 9127.0.85)) is compiled out. Reproducing needs an iOS 27.1-SDK build, and no machine I could use had Xcode 27.1. Someone with that build should check it on a Duo before merging.
Not verified: the header fading in and out in the original recording. Nothing here changes it. If it persists after this fix, it is a separate issue.
Model and harness: Claude Opus 5.5 in Claude Code (T3 Code).
… while streaming
React Native rewrites all of a scroll view's indicator insets whenever its
scrollIndicatorInsets prop changes. The keyboard-aware thread list animates
that prop's bottom inset as a reply streams, so each update reset the right
inset that the scroll-edge bleed view sets, and the indicator jumped under
the bar until the bleed view's next layout pass. While bleeding, observe the
indicator insets and put the right inset back immediately.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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📱 Native Change
Changes the native fingerprint; merging blocks production OTAs until a new store build ships.
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Nov 13, 2026
Macroscope's review found this PR approvable — Keeps the Duo scroll indicator clear of the vertical bar when streaming updates rewrite its insets. The change is limited to active scroll-edge presentation, with observations removed when that behavior ends.
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Walkthrough
The scroll edge bleed view now observes changes to both scroll-indicator inset properties while bleeding. It reapplies the right vertical indicator inset when either property changes and clears the observations when bleeding ends.
Changes: Scroll indicator inset observation
Layer / File(s)
Summary
Observe and apply indicator insets apps/mobile/modules/t3-native-controls/ios/T3ScrollEdgeBleedView.swift
While bleeding, the view observes changes to verticalScrollIndicatorInsets and scrollIndicatorInsets and reapplies the right vertical indicator inset. It clears the observations when bleeding ends.
pingdotgg/t3code#24732: Changes the same view's bleed behavior and its handling of the right-side vertical bar.
Suggested labels:bugfix
Suggested reviewers:macroscopeapp
Merge Risk: Minimal · up to 4310f
This change keeps the scroll indicator clear of the vertical bar on an unfolded Duo while a reply streams. No concrete defect was found. The author could not run a device check with the required SDK, so confirm on a Duo with the iOS 27.1 SDK before relying on the fix.
Pre-merge checks: 4
Check name
Status
Explanation
Title check
The title names the main change: a fix for the Duo thread feed scroll indicator staying left of the vertical bar while streaming. It follows the conventional commit format, and the raw summary shows t…
Description check
The description covers Problem, Change, and Verification with specific detail on the root cause (Fabric updateProps resetting scrollIndicatorInsets) and the fix (KVO observation while bleeding). It di…
Linked Issues check
Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check
Check skipped because no linked issues were found for this pull request.
Full details: Title check
Explanation
The title names the main change: a fix for the Duo thread feed scroll indicator staying left of the vertical bar while streaming. It follows the conventional commit format, and the raw summary shows the change in T3ScrollEdgeBleedView restores the right indicator inset while bleeding. The title is 85 characters, which is long but still specific.
Full details: Description check
Explanation
The description covers Problem, Change, and Verification with specific detail on the root cause (Fabric updateProps resetting scrollIndicatorInsets) and the fix (KVO observation while bleeding). It discloses that no before/after device capture exists and explains why. The Scope section is incomplete: it does not link an issue that shows the bug, and it does not explain why the fix needs no issue. The template asks for that link or justification. The model and harness line is present. Overall the description is mostly complete.
Resolution
Consider adding to the Scope section a link to the issue that shows the bug, or a short reason why no issue is needed. The Verification section also needs before/after screenshots or a recording, or a clear statement that none exist, which the author already provides.
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🚀 Mobile Continuous DeploymentTrigger Expo preview build📱 Native ChangeChanges the native fingerprint; merging blocks production OTAs until a new store build ships.size:S10-29 changed lines (additions + deletions).vouch:trustedAuthor is trusted by repo permissions or the VOUCHED list.
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🚀 Mobile Continuous Deployment
Problem
On an unfolded iPhone Duo, the thread feed's scroll indicator flickers during a streaming run. It jumps between its correct place, left of the vertical bar, and the screen edge under the bar.
T3ScrollEdgeBleedViewwidens the feed's scroll view under the bar and setsverticalScrollIndicatorInsets.rightso the indicator stays clear of it. Fabric'sRCTScrollViewComponentView(RN 0.88.1,updateProps) assigns the wholescrollIndicatorInsets(both axes,right= 0) whenever that prop changes. The bleed view only restored the inset on its ownlayoutSubviews, so for those frames the indicator sat under the bar.That prop changes far more often than
ThreadFeed's{ top, bottom: 0 }suggests.KeyboardAwareLegendListrenders react-native-keyboard-controller'sScrollViewWithBottomPadding, which sendsscrollIndicatorInsetsthrough ReanimatedanimatedPropswithbottom= keyboard + anchored end space. That end space shrinks as a streaming reply grows, so the prop changes over and over during a run. Header show/hide also changestop.Fix
While bleeding, the bleed view KVO-observes the scroll view's indicator insets and puts
rightback right away, in the same main-thread pass as React Native's write. Off the Duo, bleed is zero: no observation is installed and nothing is written, same as before. Observations are dropped when the bleed ends or the view detaches.Verification
vp run check:changed: format and typecheck pass. No Swift toolchain on the Linux dev box, so this PR's iOS dev-client build and SwiftLint in CI are the compile check.mobile-dev-clientworkflow onmacos-26, is built with the iOS 26.5 SDK. On the Duo that runs letterboxed in compatibility mode, and the bleed view's vertical-bar code (#if canImport(UIKit, _version: 9127.0.85)) is compiled out. Reproducing needs an iOS 27.1-SDK build, and no machine I could use had Xcode 27.1. Someone with that build should check it on a Duo before merging.Model and harness: Claude Opus 5.5 in Claude Code (T3 Code).
🤖 Generated with Claude Code