diff --git a/packages/ui/src/components/chat/ChatInput.tsx b/packages/ui/src/components/chat/ChatInput.tsx
index 223c9add..a70fb054 100644
--- a/packages/ui/src/components/chat/ChatInput.tsx
+++ b/packages/ui/src/components/chat/ChatInput.tsx
@@ -2335,12 +2335,11 @@ const ChatInputComponent: React.FC<ChatInputProps> = ({ onOpenSettings, scrollTo
         }
 
         // Handle ArrowUp/ArrowDown for message history navigation
-        // ArrowUp: only when cursor at start (position 0) or input is empty
+        // ArrowUp: only when input is empty (so pressing Up at start of text just moves cursor)
         // ArrowDown: also works when cursor at end (to cycle forward through history)
         const isAnyAutocompleteOpen = showCommandAutocomplete || showSkillAutocomplete || showSnippetAutocomplete || showFileMention;
-        const cursorAtStart = textareaRef.current?.selectionStart === 0 && textareaRef.current?.selectionEnd === 0;
         const cursorAtEnd = textareaRef.current?.selectionStart === message.length && textareaRef.current?.selectionEnd === message.length;
-        const canNavigateHistoryUp = !isAnyAutocompleteOpen && (message.length === 0 || cursorAtStart);
+        const canNavigateHistoryUp = !isAnyAutocompleteOpen && message.length === 0;
         const canNavigateHistoryDown = !isAnyAutocompleteOpen && (message.length === 0 || cursorAtEnd);
 
         // Markdown-aware auto-pairing (source mode), normal input only.
diff --git a/packages/ui/src/components/chat/MessageList.tsx b/packages/ui/src/components/chat/MessageList.tsx
index 755a61fd..0ae15742 100644
--- a/packages/ui/src/components/chat/MessageList.tsx
+++ b/packages/ui/src/components/chat/MessageList.tsx
@@ -1372,7 +1372,7 @@ const MessageList = React.forwardRef<MessageListHandle, MessageListProps>(({
         scrollEl.scrollTop += prependedHeight;
     });
 
-    const [virtualVersion, bumpVirtualVersion] = React.useReducer((v: number) => v + 1, 0);
+    const [historyVirtualRows, setHistoryVirtualRows] = React.useState<VirtualItem[]>(EMPTY_VIRTUAL_ROWS);
 
     const historyVirtualizer = useVirtualizer({
         count: historyEntries.length,
@@ -1383,7 +1383,9 @@ const MessageList = React.forwardRef<MessageListHandle, MessageListProps>(({
         useAnimationFrameWithResizeObserver: true,
         overscan: MESSAGE_LIST_OVERSCAN,
         enabled: shouldVirtualizeHistory,
-        onChange: bumpVirtualVersion,
+        onChange: () => {
+            setHistoryVirtualRows(historyVirtualizer.getVirtualItems());
+        },
     });
 
     React.useLayoutEffect(() => {
@@ -1438,10 +1440,13 @@ const MessageList = React.forwardRef<MessageListHandle, MessageListProps>(({
         };
     }, []);
 
-    const historyVirtualRows = React.useMemo(
-        () => (shouldVirtualizeHistory ? historyVirtualizer.getVirtualItems() : EMPTY_VIRTUAL_ROWS),
-        [historyVirtualizer, shouldVirtualizeHistory, virtualVersion],
-    );
+    // Sync virtual rows on initial mount and when virtualization toggles.
+    // Ongoing updates are handled by the virtualizer's onChange callback.
+    React.useLayoutEffect(() => {
+        setHistoryVirtualRows(
+            shouldVirtualizeHistory ? historyVirtualizer.getVirtualItems() : EMPTY_VIRTUAL_ROWS,
+        );
+    }, [shouldVirtualizeHistory, historyVirtualizer]);
 
     const allEntries = React.useMemo(() => {
         return trailingStreamingEntry ? [...historyEntries, trailingStreamingEntry] : historyEntries;