The chat add-to-session popover is anchored to viewport coordinates, so it can float over unrelated messages after the transcript scrolls. The shared selection-popover dismissal hook now treats captured scroll as a dismissal signal, matching the existing outside-click behavior and clearing the stale text selection.\n\nConstraint: Desktop selection popovers are owned by message/workspace child components, not by the transcript scroll container.\nRejected: Thread scroll state through every selectable message | would re-render message rows during scroll for a global dismissal concern.\nConfidence: high\nScope-risk: narrow\nDirective: Keep selection popover dismissal centralized unless a future menu needs scroll persistence explicitly.\nTested: bun run test -- src/components/chat/MessageList.test.tsx -t "dismisses the selected-message action when the message list scrolls"\nTested: bun run test -- src/components/chat/MessageList.test.tsx\nTested: bun run check:desktop
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