fix: project new-chat keeps model spec; sidebar header + row polish

- newConversation: ignore a chatProjectId-only template when deciding to
  apply the default model spec, so starting a chat in a project no longer
  strips the conversation `spec`
- useSelectMention: the Model Selector and @ command now retain the active
  project across endpoint/spec/preset switches; other new-chat paths still
  clear it
- Chats header now matches the Projects header (inline chevron + a new-chat
  icon button) and starts a non-project chat
- Project rows: use the new-chat icon for the per-project add button, render
  at text-sm to match the chat list, and align the row actions + hover color
  with conversation rows

client/src/components/Conversations/Conversations.tsx

@@ -2,13 +2,21 @@ import { useMemo, memo, type FC, useCallback, useEffect, useRef } from 'react';
 import throttle from 'lodash/throttle';
 import { ChevronDown } from 'lucide-react';
 import { useRecoilValue } from 'recoil';
-import { Spinner, useMediaQuery } from '@librechat/client';
+import { useQueryClient } from '@tanstack/react-query';
+import { QueryKeys } from 'librechat-data-provider';
+import { Spinner, TooltipAnchor, NewChatIcon, useMediaQuery } from '@librechat/client';
 import { List, AutoSizer, CellMeasurer, CellMeasurerCache } from 'react-virtualized';
 import type { TConversation } from 'librechat-data-provider';
-import { useLocalize, TranslationKeys, useFavorites, useShowMarketplace } from '~/hooks';
+import {
+  useLocalize,
+  TranslationKeys,
+  useFavorites,
+  useShowMarketplace,
+  useNewConvo,
+} from '~/hooks';
 import FavoritesList from '~/components/Nav/Favorites/FavoritesList';
 import { useActiveJobs } from '~/data-provider';
-import { groupConversationsByDate, cn } from '~/utils';
+import { groupConversationsByDate, clearMessagesCache, cn } from '~/utils';
 import Convo from './Convo';
 import store from '~/store';
 
@@ -77,20 +85,53 @@ interface ChatsHeaderProps {
   onToggle: () => void;
 }
 
+const headerIconButtonClassName =
+  'flex h-7 w-7 shrink-0 items-center justify-center rounded-md text-text-secondary outline-none transition-colors hover:bg-surface-active-alt hover:text-text-primary focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-inset focus-visible:ring-black dark:focus-visible:ring-white';
+
 /** Collapsible header for the Chats section */
 const ChatsHeader: FC<ChatsHeaderProps> = memo(({ isExpanded, onToggle }) => {
   const localize = useLocalize();
+  const queryClient = useQueryClient();
+  const { newConversation } = useNewConvo();
+  const conversation = useRecoilValue(store.conversationByIndex(0));
+
+  const handleNewChat = useCallback(() => {
+    clearMessagesCache(queryClient, conversation?.conversationId);
+    queryClient.invalidateQueries([QueryKeys.messages]);
+    newConversation();
+  }, [conversation?.conversationId, newConversation, queryClient]);
+
   return (
-    <button
-      onClick={onToggle}
-      className="group flex w-full items-center justify-between rounded-lg px-1 py-2 text-xs font-bold text-text-secondary outline-none focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-inset focus-visible:ring-black dark:focus-visible:ring-white"
-      type="button"
-    >
-      <span className="select-none">{localize('com_ui_chats')}</span>
-      <ChevronDown
-        className={cn('h-3 w-3 transition-transform duration-200', isExpanded ? 'rotate-180' : '')}
+    <div className="flex h-8 w-full items-center gap-0.5">
+      <button
+        onClick={onToggle}
+        className="group flex min-w-0 flex-1 items-center gap-1 rounded-lg px-1 py-2 text-xs font-bold text-text-secondary outline-none focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-inset focus-visible:ring-black dark:focus-visible:ring-white"
+        type="button"
+        aria-expanded={isExpanded}
+      >
+        <span className="select-none truncate">{localize('com_ui_chats')}</span>
+        <ChevronDown
+          className={cn(
+            'h-3 w-3 shrink-0 transition-transform duration-200',
+            isExpanded ? '' : '-rotate-90',
+          )}
+          aria-hidden="true"
+        />
+      </button>
+      <TooltipAnchor
+        description={localize('com_ui_new_chat')}
+        render={
+          <button
+            type="button"
+            aria-label={localize('com_ui_new_chat')}
+            className={headerIconButtonClassName}
+            onClick={handleNewChat}
+          >
+            <NewChatIcon className="h-4 w-4" />
+          </button>
+        }
       />
-    </button>
+    </div>
   );
 });
 

client/src/components/Conversations/ProjectsSection.tsx

@@ -11,7 +11,6 @@ import {
   FolderPlus,
   LayoutGrid,
   Pencil,
-  Plus,
   Trash2,
 } from 'lucide-react';
 import { QueryKeys } from 'librechat-data-provider';
@@ -27,6 +26,7 @@ import {
   OGDialogContent,
   TooltipAnchor,
   DropdownPopup,
+  NewChatIcon,
   useToastContext,
 } from '@librechat/client';
 import type { MenuItemProps } from '~/common';
@@ -308,7 +308,7 @@ function ProjectItem({
 
   return (
     <li className="list-none">
-      <div className="group/project-row relative flex items-center rounded-lg text-sm text-text-primary transition-colors hover:bg-surface-hover">
+      <div className="group/project-row relative flex h-9 items-center rounded-lg text-sm text-text-primary transition-colors hover:bg-surface-active-alt">
         <button
           type="button"
           onClick={() => setExpanded((prev) => !prev)}
@@ -326,7 +326,7 @@ function ProjectItem({
           <Folder className="h-4 w-4 shrink-0 text-text-secondary" aria-hidden="true" />
           <span className="truncate">{project.name}</span>
         </button>
-        <div className="absolute right-1 top-1/2 flex -translate-y-1/2 items-center gap-0.5 rounded-md bg-surface-hover opacity-0 transition-opacity group-focus-within/project-row:opacity-100 group-hover/project-row:opacity-100 has-[[data-state=open]]:opacity-100">
+        <div className="absolute right-2 top-1/2 flex -translate-y-1/2 items-center gap-0.5 rounded-md bg-surface-active-alt opacity-0 transition-opacity group-focus-within/project-row:opacity-100 group-hover/project-row:opacity-100 has-[[data-state=open]]:opacity-100">
           <TooltipAnchor
             description={localize('com_ui_new_chat_in_project', { name: project.name })}
             render={
@@ -336,7 +336,7 @@ function ProjectItem({
                 className={iconButtonClassName}
                 onClick={startChat}
               >
-                <Plus className="h-4 w-4" aria-hidden="true" />
+                <NewChatIcon className="h-4 w-4" />
               </button>
             }
           />
@@ -451,7 +451,7 @@ const ProjectsSection = ({ toggleNav, isAuthenticated }: ProjectsSectionProps) =
   }
 
   return (
-    <div className="flex flex-col px-3">
+    <div className="flex flex-col px-3 text-sm">
       <div className="flex h-8 w-full items-center gap-0.5">
         <button
           onClick={() => setIsExpanded(!isExpanded)}

client/src/hooks/Input/useSelectMention.ts

@@ -107,7 +107,10 @@ export default function useSelectMention({
 
       logger.info('conversation', 'Switching conversation to new spec', conversation);
       newConversation({
-        template: { ...(template as Partial<TConversation>) },
+        template: {
+          ...(template as Partial<TConversation>),
+          chatProjectId: conversation?.chatProjectId ?? null,
+        },
         preset,
         keepAddedConvos: isModular,
       });
@@ -201,7 +204,10 @@ export default function useSelectMention({
 
       logger.info('conversation', 'Switching conversation to new endpoint/model', template);
       newConversation({
-        template: { ...(template as Partial<TConversation>) },
+        template: {
+          ...(template as Partial<TConversation>),
+          chatProjectId: conversation?.chatProjectId ?? null,
+        },
         preset: { ...kwargs, spec: null, iconURL: null, modelLabel: null, endpoint: newEndpoint },
         keepAddedConvos: isNewModular,
       });
@@ -264,6 +270,7 @@ export default function useSelectMention({
 
       logger.info('conversation', 'Switching conversation to new preset', template);
       newConversation({
+        template: { chatProjectId: conversation?.chatProjectId ?? null },
         preset: newPreset,
         keepAddedConvos: isModular,
         disableParams,

client/src/hooks/useNewConvo.ts

@@ -327,7 +327,8 @@ const useNewConvo = (index = 0) => {
         startupConfig &&
         (startupConfig.modelSpecs?.prioritize === true ||
           (startupConfig.interface?.modelSelect ?? true) !== true ||
-          (result?.last != null && Object.keys(_template).length === 0)) &&
+          (result?.last != null &&
+            Object.keys(_template).filter((key) => key !== 'chatProjectId').length === 0)) &&
         defaultModelSpec
       ) {
         preset = getModelSpecPreset(defaultModelSpec);