From aeabb134fd1072428cea9114ecf5a2472626c368 Mon Sep 17 00:00:00 2001
From: LukeParkerDev <10430890+Hona@users.noreply.github.com>
Date: Sun, 14 Jun 2026 22:02:34 +0200
Subject: [PATCH] fix(app): preserve anchors across large row measurements

---
 packages/app/src/pages/session/message-timeline.tsx | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/packages/app/src/pages/session/message-timeline.tsx b/packages/app/src/pages/session/message-timeline.tsx
index 2d78cf747dd..db1e3d09713 100644
--- a/packages/app/src/pages/session/message-timeline.tsx
+++ b/packages/app/src/pages/session/message-timeline.tsx
@@ -16,7 +16,7 @@ import { createStore, produce } from "solid-js/store"
 import { Dynamic } from "solid-js/web"
 import { useNavigate } from "@solidjs/router"
 import { useMutation } from "@tanstack/solid-query"
-import { createVirtualizer, defaultRangeExtractor } from "@tanstack/solid-virtual"
+import { createVirtualizer, defaultRangeExtractor, elementScroll } from "@tanstack/solid-virtual"
 import { Accordion } from "@opencode-ai/ui/accordion"
 import { Button } from "@opencode-ai/ui/button"
 import { Card } from "@opencode-ai/ui/card"
@@ -468,12 +468,18 @@ export function MessageTimeline(props: {
     return reuseTimelineRows(previous, rows)
   })
   const [toolOpen, setToolOpen] = createStore<Record<string, boolean | undefined>>({})
+  let virtualContent: HTMLDivElement | undefined
   const virtualizer = createVirtualizer<HTMLDivElement, HTMLDivElement>({
     get count() {
       return timelineRows().length
     },
     getScrollElement: () => listRoot() ?? null,
     estimateSize: () => timelineFallbackItemSize,
+    scrollToFn: (offset, options, instance) => {
+      // Expose the computed range before core writes an anchor correction so the browser does not clamp it to the old height.
+      if (virtualContent) virtualContent.style.height = `${instance.getTotalSize()}px`
+      elementScroll(offset, options, instance)
+    },
     get getItemKey() {
       const rows = timelineRows()
       return (index: number) => {
@@ -1579,6 +1585,7 @@ export function MessageTimeline(props: {
         <div
           data-timeline-virtual-content
           ref={(element) => {
+            virtualContent = element
             props.setContentRef(element)
           }}
           style={{