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fix(scroll): round 11 — MessageThread native scroll listener (WebKit E2E flake) #97

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Merged
TortoiseWolfe merged 1 commit into from
May 19, 2026
Merged

fix(scroll): round 11 — MessageThread native scroll listener (WebKit E2E flake) #97

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15 changes: 14 additions & 1 deletion src/components/molecular/MessageThread/MessageThread.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -211,6 +211,20 @@ export default function MessageThread({
}
}, [hasMore, loading, onLoadMore]);

// Bind handleScroll as a native DOM event listener instead of via React's
// `onScroll` JSX prop. Reason: React's synthetic onScroll does not reliably
// fire on WebKit when test code dispatches a programmatic
// `dispatchEvent(new Event('scroll', { bubbles: true }))` after assigning
// `scrollTop`. Native `addEventListener('scroll', ...)` does fire
// deterministically across chromium, firefox, and webkit. See the round-10
// E2E flake mitigation in CLAUDE.md "CI & E2E Stability" section.
useEffect(() => {
const parent = parentRef.current;
if (!parent) return;
parent.addEventListener('scroll', handleScroll, { passive: true });
return () => parent.removeEventListener('scroll', handleScroll);
}, [handleScroll]);

// Scroll to bottom with smooth animation
const scrollToBottom = useCallback(
(smooth = false) => {
Expand Down Expand Up @@ -350,7 +364,6 @@ export default function MessageThread({
<div className={`relative h-full${className ? ` ${className}` : ''}`}>
<div
ref={parentRef}
onScroll={handleScroll}
className="absolute inset-0 overflow-y-auto"
data-testid="message-thread"
style={{ overscrollBehavior: 'contain' }}
Expand Down
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