diff --git a/frontend/src/app/canvas/CanvasMenubar.tsx b/frontend/src/app/canvas/CanvasMenubar.tsx
index e3e9a6f..12cc300 100644
--- a/frontend/src/app/canvas/CanvasMenubar.tsx
+++ b/frontend/src/app/canvas/CanvasMenubar.tsx
@@ -3,6 +3,7 @@
  */
 
 import React, { useEffect } from 'react'
+import { Link } from 'react-router-dom'
 import {
   Menubar,
   MenubarContent,
@@ -17,7 +18,7 @@ import {
 } from '@/components/ui/menubar'
 import { Kbd, KbdGroup } from '@/components/ui/kbd'
 import { useTheme } from '@/lib/themeContext'
-import { Download, FolderOpen, Moon, Redo2, Sun, Undo2 } from 'lucide-react'
+import { ArrowLeft, Download, FolderOpen, Moon, Redo2, Sun, Undo2 } from 'lucide-react'
 
 export type CanvasMenubarProps = {
   onImport: () => void
@@ -72,6 +73,13 @@ export function CanvasMenubar({
 
   return (
     <Menubar className="shrink-0 rounded-none border-x-0 border-t-0 border-b-0">
+      <Link
+        to="/projects"
+        aria-label="Back to projects"
+        className="flex shrink-0 items-center rounded-sm px-2 py-1 text-sm outline-none focus:bg-accent focus:text-accent-foreground hover:bg-accent hover:text-accent-foreground"
+      >
+        <ArrowLeft className="size-4" />
+      </Link>
       <MenubarMenu>
         <MenubarTrigger className="font-medium">Project</MenubarTrigger>
         <MenubarContent>
diff --git a/frontend/src/app/platform/AppSidebar.tsx b/frontend/src/app/platform/AppSidebar.tsx
index 511afc7..e894f4a 100644
--- a/frontend/src/app/platform/AppSidebar.tsx
+++ b/frontend/src/app/platform/AppSidebar.tsx
@@ -36,6 +36,7 @@ import {
 import { Button } from '@/components/ui/button'
 import { Input } from '@/components/ui/input'
 import { MoreHorizontal, Plus, Trash2, Pencil, FolderOpen, ListTodo } from 'lucide-react'
+import { Tooltip, TooltipContent, TooltipTrigger } from '@/components/ui/tooltip'
 import { useSidebar } from '@/components/ui/sidebar'
 import { usePlatform } from './platformContext'
 import { getProjectIcon } from './icon-map'
@@ -43,7 +44,8 @@ import { NewProjectDialog } from './NewProjectDialog'
 import type { Project } from './types'
 
 export function AppSidebar() {
-  const { isMobile } = useSidebar()
+  const { isMobile, state, setOpen } = useSidebar()
+  const isCollapsed = state === 'collapsed'
   const { orderedProjects, createProject, deleteProject, renameProject, reorderProjects, projectOrder } = usePlatform()
   const navigate = useNavigate()
   const { projectId: selectedProjectId } = useParams<{ projectId: string }>()
@@ -121,36 +123,84 @@ export function AppSidebar() {
 
   return (
     <>
-      <Sidebar collapsible="icon">
-        <SidebarHeader>
-          <SidebarMenu>
+      <Sidebar collapsible="icon" className="relative">
+        {isCollapsed && (
+          <button
+            type="button"
+            className="absolute inset-0 z-0 cursor-pointer border-0 bg-transparent p-0 outline-none"
+            onClick={() => setOpen(true)}
+            aria-label="Expand sidebar"
+          />
+        )}
+        <SidebarHeader className="relative z-10 flex flex-row items-center gap-2">
+          <SidebarMenu className="flex-1 min-w-0">
             <SidebarMenuItem>
-              <SidebarMenuButton asChild size="lg" tooltip="Zoë" className="font-semibold font-serif">
-                <Link to="/projects">
-                  <span className="flex size-8 min-w-8 items-center justify-center rounded-lg bg-sidebar-primary text-sidebar-primary-foreground dark:bg-white dark:text-black">
-                    <span
-                      className="size-6 shrink-0 rounded-[2px] opacity-90"
-                      style={{
-                        maskImage: 'url(/app-icon.svg)',
-                        maskRepeat: 'no-repeat',
-                        maskPosition: 'center',
-                        maskSize: 'contain',
-                        WebkitMaskImage: 'url(/app-icon.svg)',
-                        WebkitMaskRepeat: 'no-repeat',
-                        WebkitMaskPosition: 'center',
-                        WebkitMaskSize: 'contain',
-                        backgroundColor: 'currentColor',
+              {isCollapsed ? (
+                <Tooltip>
+                  <TooltipTrigger asChild>
+                    <SidebarMenuButton
+                      size="lg"
+                      className="font-semibold font-serif"
+                      onClick={(e) => {
+                        e.preventDefault()
+                        e.stopPropagation()
+                        setOpen(true)
                       }}
-                      aria-hidden
-                    />
-                  </span>
-                  <span className="font-serif group-data-[collapsible=icon]:hidden uppercase tracking-wide">ZOË</span>
-                </Link>
-              </SidebarMenuButton>
+                    >
+                      <span className="flex size-8 min-w-8 items-center justify-center rounded-lg bg-sidebar-primary text-sidebar-primary-foreground dark:bg-white dark:text-black">
+                        <span
+                          className="size-6 shrink-0 rounded-[2px] opacity-90"
+                          style={{
+                            maskImage: 'url(/app-icon.svg)',
+                            maskRepeat: 'no-repeat',
+                            maskPosition: 'center',
+                            maskSize: 'contain',
+                            WebkitMaskImage: 'url(/app-icon.svg)',
+                            WebkitMaskRepeat: 'no-repeat',
+                            WebkitMaskPosition: 'center',
+                            WebkitMaskSize: 'contain',
+                            backgroundColor: 'currentColor',
+                          }}
+                          aria-hidden
+                        />
+                      </span>
+                      <span className="font-serif group-data-[collapsible=icon]:hidden uppercase tracking-wide">ZOË</span>
+                    </SidebarMenuButton>
+                  </TooltipTrigger>
+                  <TooltipContent side="right">Click to expand sidebar</TooltipContent>
+                </Tooltip>
+              ) : (
+                <SidebarMenuButton asChild size="lg" tooltip="Zoë" className="font-semibold font-serif">
+                  <Link to="/projects">
+                    <span className="flex size-8 min-w-8 items-center justify-center rounded-lg bg-sidebar-primary text-sidebar-primary-foreground dark:bg-white dark:text-black">
+                      <span
+                        className="size-6 shrink-0 rounded-[2px] opacity-90"
+                        style={{
+                          maskImage: 'url(/app-icon.svg)',
+                          maskRepeat: 'no-repeat',
+                          maskPosition: 'center',
+                          maskSize: 'contain',
+                          WebkitMaskImage: 'url(/app-icon.svg)',
+                          WebkitMaskRepeat: 'no-repeat',
+                          WebkitMaskPosition: 'center',
+                          WebkitMaskSize: 'contain',
+                          backgroundColor: 'currentColor',
+                        }}
+                        aria-hidden
+                      />
+                    </span>
+                    <span className="font-serif group-data-[collapsible=icon]:hidden uppercase tracking-wide">ZOË</span>
+                  </Link>
+                </SidebarMenuButton>
+              )}
             </SidebarMenuItem>
           </SidebarMenu>
+          {!isCollapsed && <SidebarTrigger className="ml-auto shrink-0" />}
         </SidebarHeader>
-        <SidebarContent>
+        <SidebarContent
+          className="relative z-10"
+          onClick={isCollapsed ? (e) => { if ((e.target as HTMLElement).closest('button') || (e.target as HTMLElement).closest('a')) return; setOpen(true) } : undefined}
+        >
           <SidebarGroup>
             <SidebarGroupLabel className="group-data-[collapsible=icon]:hidden">Projects</SidebarGroupLabel>
             <SidebarMenu>
@@ -250,8 +300,8 @@ export function AppSidebar() {
             </SidebarMenu>
           </SidebarGroup>
         </SidebarContent>
-        <SidebarFooter />
-        <SidebarRail />
+        <SidebarFooter className="relative z-10" />
+        <SidebarRail className="relative z-10" />
       </Sidebar>
 
       <Dialog open={!!renameTarget} onOpenChange={(open) => !open && setRenameTarget(null)}>
diff --git a/frontend/src/app/platform/PlatformPage.tsx b/frontend/src/app/platform/PlatformPage.tsx
index 466cd9b..60bc31e 100644
--- a/frontend/src/app/platform/PlatformPage.tsx
+++ b/frontend/src/app/platform/PlatformPage.tsx
@@ -2,65 +2,30 @@
  * Platform: main layout with sidebar and header. Renders child routes (projects list or canvas) via Outlet.
  */
 
-import React from 'react'
-import { Link, Outlet, useParams, useLocation } from 'react-router-dom'
-import {
-  Breadcrumb,
-  BreadcrumbItem,
-  BreadcrumbLink,
-  BreadcrumbList,
-  BreadcrumbPage,
-  BreadcrumbSeparator,
-} from '@/components/ui/breadcrumb'
-import { Separator } from '@/components/ui/separator'
-import { SidebarInset, SidebarProvider, SidebarTrigger } from '@/components/ui/sidebar'
+import React, { useEffect, useState } from 'react'
+import { Outlet, useParams } from 'react-router-dom'
+import { SidebarProvider } from '@/components/ui/sidebar'
 import { PlatformProvider, usePlatform } from './platformContext'
 import { AppSidebar } from './AppSidebar'
 
 function PlatformLayoutInner() {
   const { projectId } = useParams<{ projectId: string }>()
-  const location = useLocation()
   const { projects } = usePlatform()
-  const project = projectId ? projects.find((p) => p.id === projectId) : null
-  const isProjectsList = location.pathname === '/projects'
+  const [sidebarOpen, setSidebarOpen] = useState(true)
+
+  useEffect(() => {
+    if (projectId) setSidebarOpen(false)
+    else setSidebarOpen(true)
+  }, [projectId])
 
   return (
-    <SidebarProvider>
+    <SidebarProvider open={sidebarOpen} onOpenChange={setSidebarOpen}>
       <AppSidebar />
-      <SidebarInset className="flex min-h-0 flex-1 flex-col">
-        <header className="flex h-12 shrink-0 items-center gap-2 border-b border-border/40 px-1 transition-[width,height] ease-linear group-has-data-[collapsible=icon]/sidebar-wrapper:h-12">
-          <div className="flex items-center gap-2 px-2">
-            <SidebarTrigger className="-ml-1" />
-            <Separator orientation="vertical" className="mr-2 h-4" />
-            <Breadcrumb>
-              <BreadcrumbList>
-                {isProjectsList ? (
-                  <BreadcrumbItem>
-                    <BreadcrumbPage className="line-clamp-1">Projects</BreadcrumbPage>
-                  </BreadcrumbItem>
-                ) : (
-                  <>
-                    <BreadcrumbItem className="hidden md:block">
-                      <BreadcrumbLink asChild>
-                        <Link to="/projects">Projects</Link>
-                      </BreadcrumbLink>
-                    </BreadcrumbItem>
-                    <BreadcrumbSeparator className="hidden md:block" />
-                    <BreadcrumbItem>
-                      <BreadcrumbPage className="line-clamp-1">
-                        {project ? project.name : 'Project'}
-                      </BreadcrumbPage>
-                    </BreadcrumbItem>
-                  </>
-                )}
-              </BreadcrumbList>
-            </Breadcrumb>
-          </div>
-        </header>
+      <div className="relative flex min-h-0 w-full flex-1 flex-col bg-background">
         <div className="flex min-h-0 flex-1 flex-col">
           <Outlet />
         </div>
-      </SidebarInset>
+      </div>
     </SidebarProvider>
   )
 }