fix(messages): default topic message list to newest-first ordering

frontend/src/components/ai-elements/prompt-input.tsx

@@ -414,8 +414,8 @@ export const PromptInputActionAddAttachments = ({
   return (
     <DropdownMenuItem
       {...props}
-      onSelect={(e) => {
-        e.preventDefault();
+      closeOnClick={false}
+      onClick={() => {
         attachments.openFileDialog();
       }}
     >

frontend/src/components/pages/topics/Tab.Messages/index.tsx

@@ -89,7 +89,7 @@ import { isServerless } from '../../../../config';
 import { useQueryStateWithCallback } from '../../../../hooks/use-query-state-with-callback';
 import { PayloadEncoding } from '../../../../protogen/redpanda/api/console/v1alpha1/common_pb';
 import { appGlobal } from '../../../../state/app-global';
-import { useTopicSettingsStore } from '../../../../stores/topic-settings-store';
+import { DEFAULT_SORTING, useTopicSettingsStore } from '../../../../stores/topic-settings-store';
 import { IsDev } from '../../../../utils/env';
 import { sanitizeString, wrapFilterFragment } from '../../../../utils/filter-helper';
 import { trimSlidingWindow } from '../../../../utils/message-table-helpers';
@@ -472,7 +472,7 @@ export const TopicMessageView: FC<TopicMessageViewProps> = (props) => {
       getDefaultValue: () => getSorting(props.topic.topicName),
     },
     'sort',
-    sortingParser.withDefault([])
+    sortingParser.withDefault(DEFAULT_SORTING)
   );
 
   // Continuous pagination toggle state
@@ -572,11 +572,16 @@ export const TopicMessageView: FC<TopicMessageViewProps> = (props) => {
       })
     : messages;
 
-  // For continuous pagination, just use the filtered messages directly
-  // We don't use placeholders as they cause page content to shift
+  // Continuous pagination disables header sorting, so the table's sorted row
+  // model can't impose newest-first there. Force it for the "Newest" fetch only
+  // (timestamp desc, then offset desc as a cross-partition tiebreak). Other
+  // origins keep the streamed order.
+  // In the normal paginated view the table sorts client-side via the default
+  // `sorting` state (DEFAULT_SORTING = timestamp desc, offset desc), so we pass
+  // the rows through untouched here.
   const filteredMessages =
     continuousPaginationEnabled && startOffset === PartitionOffsetOrigin.EndMinusResults
-      ? [...baseFilteredMessages].sort((a, b) => b.timestamp - a.timestamp)
+      ? [...baseFilteredMessages].sort((a, b) => b.timestamp - a.timestamp || b.offset - a.offset)
       : baseFilteredMessages;
 
   // Convert @computed activePreviewTags to useMemo

frontend/src/components/redpanda-ui/components/dropdown-menu.tsx

@@ -236,6 +236,8 @@ function DropdownMenuContent({
 type DropdownMenuItemProps = React.ComponentProps<typeof DropdownMenuPrimitive.Item> & {
   inset?: boolean;
   variant?: 'default' | 'destructive';
+  /** @deprecated Base UI menu items have no `onSelect`. Use `onClick` (add `closeOnClick={false}` to keep the menu open). */
+  onSelect?: never;
 };
 
 function DropdownMenuItem({
@@ -276,6 +278,8 @@ function DropdownMenuItem({
 
 type DropdownMenuCheckboxItemProps = React.ComponentProps<typeof DropdownMenuPrimitive.CheckboxItem> & {
   inset?: boolean;
+  /** @deprecated Base UI menu items have no `onSelect`. Use `onClick` (add `closeOnClick={false}` to keep the menu open). */
+  onSelect?: never;
 };
 
 function DropdownMenuCheckboxItem({
@@ -313,6 +317,8 @@ function DropdownMenuCheckboxItem({
 
 type DropdownMenuRadioItemProps = React.ComponentProps<typeof DropdownMenuPrimitive.RadioItem> & {
   inset?: boolean;
+  /** @deprecated Base UI menu items have no `onSelect`. Use `onClick` (add `closeOnClick={false}` to keep the menu open). */
+  onSelect?: never;
 };
 
 function DropdownMenuRadioItem({ className, children, disabled, inset, ...props }: DropdownMenuRadioItemProps) {

frontend/src/stores/topic-settings-store.ts

@@ -111,7 +111,15 @@ export type TopicSettingsStore = {
   clearAllSettings: () => void;
 };
 
-const DEFAULT_SORTING: SortingState = [];
+// Default display order for the message list: newest-first by timestamp, with
+// offset descending as a cross-partition tiebreak (offset isn't global across
+// partitions, so timestamp is the primary key). The backend's listMessages
+// stream isn't globally timestamp-sorted across partitions, so this default
+// drives the table's client-side sort to give users a sensible newest-first view.
+export const DEFAULT_SORTING: SortingState = [
+  { id: 'timestamp', desc: true },
+  { id: 'offset', desc: true },
+];
 
 const DEFAULT_SEARCH_PARAMS: TopicSearchParams = {
   offsetOrigin: -1,
@@ -214,7 +222,11 @@ export const useTopicSettingsStore = create<TopicSettingsStore>()(
 
         getSorting: (topicName: string) => {
           const topic = get().perTopicSettings.find((t) => t.topicName === topicName);
-          return topic?.searchParams.sorting ?? DEFAULT_SORTING;
+          const sorting = topic?.searchParams.sorting;
+          // Treat an empty/unset sort as "use the newest-first default" so the
+          // default applies on every fresh load, including returning users whose
+          // persisted settings still hold the old empty sort.
+          return sorting && sorting.length > 0 ? sorting : DEFAULT_SORTING;
         },
 
         setSearchParams: (topicName: string, searchParams: Partial<TopicSearchParams>) => {