Timeline brief pins three things the investigation settled: a third grid row rather than position: sticky (so useConversationScrollAnchor is not touched), fixed bar height as a correctness requirement, and a two-element sticky bar per the product's less-is-more call. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_016P5RoqzmUQEbeC2qjAkeGr