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https://github.com/NousResearch/hermes-agent.git
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a7e6a4fc0b
User reported: after pressing Enter on a long thread, the view jumps up — the just-submitted message disappears below the fold. Confirmed via apps/desktop/scripts/measure-jump.mjs: before: distFromBottom 0 → 49.5px, sticks there permanently after: distFromBottom 0 → ~0 (worst case 4px for one frame) Root cause in useThreadScrollAnchor (thread-virtualizer.tsx): 1. The sticky-bottom logic disarmed on any scroll event where `scrollTop < lastTopRef.current`. That check can't distinguish a user scrolling up from a programmatic `pinToBottom` write that the browser clamped short of bottom (because content also grew in the same frame, so `scrollTop = scrollHeight` lands at `scrollHeight - clientHeight` for the OLD scrollHeight, which is now below the NEW scrollHeight). Result: sticky-bottom disarmed permanently on the user's first submit. 2. There was no synchronous pin tied to React's commit phase. By the time the ResizeObserver fired and re-pinned, the user had already seen ~50ms of "message below the fold" — visually that reads as the view jumping up. Fix: - `programmaticScrollPendingRef` counter tracks scroll events we expect to be ours (one per `pinToBottom` write). The scroll handler skips the disarm check when consuming a pending tick, keeps the arm bit true, and re-pins synchronously if the browser clamped us short of bottom. A depth cap (8) breaks runaway loops in pathological streaming-burst layouts. - `useLayoutEffect` on `groupCount` increase pins BEFORE the browser paints, eliminating the visible ~50ms window between optimistic user-message insert and the RO/scroll-event chain firing. Verified on the long Cloud Shadows thread (7-8 turns, ~11k px tall): all three repro runs now hold within 0–4 px of bottom across the post-Enter transition. Submit latency unchanged (paint 77–107 ms), streaming-typing latency unchanged. Also adds three debug harnesses: - measure-jump.mjs — sample thread scroll across Enter - probe-thread.mjs — dump current thread / scroll state - diag-jump.mjs — intercept scrollTop + RO + mutations across Enter |
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