diff --git a/frontend/src/components/assistant/ChatSidebar.tsx b/frontend/src/components/assistant/ChatSidebar.tsx
index d474e5e9..133f0a60 100644
--- a/frontend/src/components/assistant/ChatSidebar.tsx
+++ b/frontend/src/components/assistant/ChatSidebar.tsx
@@ -1,4 +1,4 @@
-import { Plus, Pin, Trash2, MessageSquare } from 'lucide-react'
+import { Plus, Pin, Trash2, MessageSquare, History, X } from 'lucide-react'
 import { cn } from '@/lib/utils'
 import type { ChatListItem } from '@/types/assistant-chat'
 
@@ -11,6 +11,8 @@ interface ChatSidebarProps {
   onTogglePin: (id: string, pinned: boolean) => void
   mobileOpen?: boolean
   onMobileClose?: () => void
+  collapsed?: boolean
+  onToggleCollapse?: () => void
 }
 
 export function ChatSidebar({
@@ -22,6 +24,8 @@ export function ChatSidebar({
   onTogglePin,
   mobileOpen = false,
   onMobileClose,
+  collapsed = false,
+  onToggleCollapse,
 }: ChatSidebarProps) {
   const pinnedChats = chats.filter(c => c.pinned)
   const unpinnedChats = chats.filter(c => !c.pinned)
@@ -36,6 +40,11 @@ export function ChatSidebar({
     onMobileClose?.()
   }
 
+  // When collapsed on desktop, render nothing — parent renders the top bar
+  if (collapsed && !mobileOpen) {
+    return null
+  }
+
   return (
     <>
       {/* Mobile overlay */}
@@ -52,14 +61,23 @@ export function ChatSidebar({
         style={{ background: 'var(--color-bg-sidebar)' }}
       >
       {/* Header */}
-      <div className="px-4 py-3 border-b shrink-0" style={{ borderColor: 'var(--color-border-default)' }}>
+      <div className="px-3 py-3 border-b shrink-0 flex items-center gap-2" style={{ borderColor: 'var(--color-border-default)' }}>
         <button
           onClick={handleNewChat}
-          className="w-full flex items-center justify-center gap-2 bg-primary text-white font-semibold text-sm rounded-lg px-4 py-2.5 hover:brightness-110 active:scale-[0.98] transition-all"
+          className="flex-1 flex items-center justify-center gap-2 bg-primary text-white font-semibold text-sm rounded-lg px-4 py-2.5 hover:brightness-110 active:scale-[0.98] transition-all"
         >
           <Plus size={16} />
           New Chat
         </button>
+        {onToggleCollapse && (
+          <button
+            onClick={onToggleCollapse}
+            className="hidden sm:flex p-1.5 rounded-lg text-muted-foreground hover:text-heading hover:bg-elevated transition-colors"
+            title="Collapse to top bar"
+          >
+            <X size={16} />
+          </button>
+        )}
       </div>
 
       {/* Chat list */}
@@ -108,6 +126,51 @@ export function ChatSidebar({
   )
 }
 
+/** Collapsed top bar — rendered by the parent page above the chat area */
+export function ChatSidebarCollapsedBar({
+  chats,
+  activeChatId,
+  onNewChat,
+  onExpand,
+}: {
+  chats: ChatListItem[]
+  activeChatId: string | null
+  onNewChat: () => void
+  onExpand: () => void
+}) {
+  return (
+    <div
+      className="flex items-center gap-2 px-3 py-2 border-b shrink-0"
+      style={{ background: 'var(--color-bg-sidebar)', borderColor: 'var(--color-border-default)' }}
+    >
+      <button
+        onClick={onNewChat}
+        className="flex items-center gap-1.5 bg-primary text-white font-semibold text-xs rounded-md px-3 py-1.5 hover:brightness-110 active:scale-[0.98] transition-all"
+      >
+        <Plus size={14} />
+        New
+      </button>
+      <button
+        onClick={onExpand}
+        className="flex items-center gap-1.5 rounded-md px-2.5 py-1.5 text-xs text-muted-foreground hover:text-heading hover:bg-elevated transition-colors"
+        title="Show chat history"
+      >
+        <History size={14} />
+        <span>History</span>
+        {chats.length > 0 && (
+          <span className="text-[10px] bg-elevated rounded-full px-1.5 py-0.5 font-medium">{chats.length}</span>
+        )}
+      </button>
+      <div className="flex-1" />
+      {activeChatId && (
+        <span className="text-xs text-muted-foreground truncate max-w-[300px]">
+          {chats.find(c => c.id === activeChatId)?.title}
+        </span>
+      )}
+    </div>
+  )
+}
+
 function ChatItem({
   chat,
   isActive,
diff --git a/frontend/src/pages/AssistantChatPage.tsx b/frontend/src/pages/AssistantChatPage.tsx
index 05747412..c8de1740 100644
--- a/frontend/src/pages/AssistantChatPage.tsx
+++ b/frontend/src/pages/AssistantChatPage.tsx
@@ -10,7 +10,7 @@ import { aiSessionsApi } from '@/api/aiSessions'
 import { useBranching } from '@/hooks/useBranching'
 import { analytics } from '@/lib/analytics'
 import { toast } from '@/lib/toast'
-import { ChatSidebar } from '@/components/assistant/ChatSidebar'
+import { ChatSidebar, ChatSidebarCollapsedBar } from '@/components/assistant/ChatSidebar'
 import { ChatMessage } from '@/components/assistant/ChatMessage'
 import { TaskLane } from '@/components/assistant/TaskLane'
 import { ConcludeSessionModal } from '@/components/assistant/ConcludeSessionModal'
@@ -45,6 +45,14 @@ export default function AssistantChatPage() {
   const [activeQuestions, setActiveQuestions] = useState<QuestionItem[]>([])
   const [activeActions, setActiveActions] = useState<ActionItem[]>([])
   const [showTaskLane, setShowTaskLane] = useState(false)
+  const [sidebarCollapsed, setSidebarCollapsed] = useState(() =>
+    localStorage.getItem('rf-chat-sidebar-collapsed') === 'true'
+  )
+  const toggleSidebarCollapse = () => {
+    const next = !sidebarCollapsed
+    setSidebarCollapsed(next)
+    localStorage.setItem('rf-chat-sidebar-collapsed', String(next))
+  }
   const messagesEndRef = useRef<HTMLDivElement>(null)
   const inputRef = useRef<HTMLTextAreaElement>(null)
   const fileInputRef = useRef<HTMLInputElement>(null)
@@ -470,17 +478,20 @@ export default function AssistantChatPage() {
     <>
     <PageMeta title="AI Assistant" />
     <div className="flex h-[calc(100vh-3.5rem)]">
-      {/* Sidebar — hidden on mobile, slide-out via toggle */}
-      <div className="hidden sm:block">
-        <ChatSidebar
-          chats={chats}
-          activeChatId={activeChatId}
-          onSelectChat={selectChat}
-          onNewChat={handleNewChat}
-          onDeleteChat={handleDeleteChat}
-          onTogglePin={handleTogglePin}
-        />
-      </div>
+      {/* Sidebar — hidden on mobile, collapsed to top bar or full sidebar on desktop */}
+      {!sidebarCollapsed && (
+        <div className="hidden sm:block">
+          <ChatSidebar
+            chats={chats}
+            activeChatId={activeChatId}
+            onSelectChat={selectChat}
+            onNewChat={handleNewChat}
+            onDeleteChat={handleDeleteChat}
+            onTogglePin={handleTogglePin}
+            onToggleCollapse={toggleSidebarCollapse}
+          />
+        </div>
+      )}
       <div className="sm:hidden">
         <ChatSidebar
           chats={chats}
@@ -495,7 +506,22 @@ export default function AssistantChatPage() {
       </div>
 
       {/* Main chat area + optional branch sidebar */}
-      <div className="flex-1 flex min-w-0">
+      <div className="flex-1 flex flex-col min-w-0">
+
+      {/* Collapsed sidebar top bar — desktop only */}
+      {sidebarCollapsed && (
+        <div className="hidden sm:block">
+          <ChatSidebarCollapsedBar
+            chats={chats}
+            activeChatId={activeChatId}
+            onNewChat={handleNewChat}
+            onExpand={toggleSidebarCollapse}
+          />
+        </div>
+      )}
+
+      {/* Chat content row: chat column + TaskLane side by side */}
+      <div className="flex-1 flex min-w-0 min-h-0">
       <div className="flex-1 flex flex-col min-w-0">
         {/* Mobile header with chat history toggle */}
         <div className="sm:hidden flex items-center gap-2 px-3 py-2 border-b border-border shrink-0">
@@ -555,7 +581,7 @@ export default function AssistantChatPage() {
             </div>
 
             {/* Rich Input */}
-            <div className={cn("px-3 sm:px-6 py-3 shrink-0", !showTaskLane && "border-t border-border")}>
+            <div className="px-3 sm:px-6 py-3 shrink-0">
               <div
                 className="max-w-3xl mx-auto"
                 onDragOver={handleDragOver}
@@ -710,7 +736,8 @@ export default function AssistantChatPage() {
       {/* Branch map hidden — branching is now silent/background only.
           Branches are tracked in the DB but not shown to the user.
           The AI manages branch context internally. */}
-      </div>
+      </div>{/* close chat content row */}
+      </div>{/* close outer flex-col */}
 
       {/* Conclude Session Modal */}
       <ConcludeSessionModal