diff --git a/ui/src/App.jsx b/ui/src/App.jsx
index e4f3025..65afbc5 100644
--- a/ui/src/App.jsx
+++ b/ui/src/App.jsx
@@ -1,7 +1,8 @@
 import { useState, useEffect } from 'react'
-import { BrowserRouter, Routes, Route, NavLink, Navigate } from 'react-router-dom'
+import { BrowserRouter, Routes, Route, Navigate } from 'react-router-dom'
 import { api, setCredentials, clearCredentials } from './api'
-import useTheme from './theme.jsx'
+import StatusBar from './components/StatusBar.jsx'
+import Sidebar from './components/Sidebar.jsx'
 import Login from './pages/Login'
 import Sources from './pages/Sources'
 import Import from './pages/Import'
@@ -13,25 +14,12 @@ import Pivot from './pages/Pivot'
 import Remap from './pages/Remap'
 import Stacks from './pages/Stacks'
 
-const NAV = [
-  { to: '/sources', label: 'Sources' },
-  { to: '/import', label: 'Import' },
-  { to: '/rules', label: 'Rules' },
-  { to: '/mappings', label: 'Mappings' },
-  { to: '/remap', label: 'Remap' },
-  { to: '/records', label: 'Records' },
-  { to: '/pivot', label: 'Pivot' },
-  { to: '/stacks', label: 'Stacks' },
-  { to: '/log', label: 'Log' },
-]
-
 export default function App() {
-  const { dark, setDark } = useTheme()
   const [authed, setAuthed] = useState(false)
   const [loginUser, setLoginUser] = useState('')
   const [sources, setSources] = useState([])
   const [source, setSource] = useState(() => localStorage.getItem('selectedSource') || '')
-  const [sidebarOpen, setSidebarOpen] = useState(false)
+  const [sidebarExpanded, setSidebarExpanded] = useState(() => localStorage.getItem('df_sidebar') !== 'collapsed')
   // Sets of names whose dfv view is out of sync with current definitions
   const [staleSources, setStaleSources] = useState(new Set())
   const [staleStacks, setStaleStacks] = useState(new Set())
@@ -121,108 +109,26 @@ export default function App() {
     if (source) localStorage.setItem('selectedSource', source)
   }, [source])
 
+  useEffect(() => {
+    localStorage.setItem('df_sidebar', sidebarExpanded ? 'expanded' : 'collapsed')
+  }, [sidebarExpanded])
+
   if (!authed) return <Login onLogin={handleLogin} />
 
-  const sidebar = (
-    <div className="flex flex-col h-full">
-      {/* Header */}
-      <div className="px-4 py-3 border-b border-gray-200">
-        <div className="flex items-center justify-between">
-          <span className="text-sm font-semibold text-gray-800 tracking-wide uppercase">Dataflow</span>
-          <div className="flex items-center gap-1 ml-auto">
-            <button
-              onClick={() => setDark(d => !d)}
-              className="w-6 h-6 flex items-center justify-center rounded hover:bg-gray-100 text-gray-400 hover:text-gray-600"
-              title={dark ? 'Switch to light mode' : 'Switch to dark mode'}
-            >
-              {dark ? (
-                <svg width="13" height="13" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round">
-                  <circle cx="12" cy="12" r="4"/>
-                  <line x1="12" y1="2" x2="12" y2="5"/>
-                  <line x1="12" y1="19" x2="12" y2="22"/>
-                  <line x1="4.93" y1="4.93" x2="7.05" y2="7.05"/>
-                  <line x1="16.95" y1="16.95" x2="19.07" y2="19.07"/>
-                  <line x1="2" y1="12" x2="5" y2="12"/>
-                  <line x1="19" y1="12" x2="22" y2="12"/>
-                  <line x1="4.93" y1="19.07" x2="7.05" y2="16.95"/>
-                  <line x1="16.95" y1="7.05" x2="19.07" y2="4.93"/>
-                </svg>
-              ) : (
-                <svg width="13" height="13" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round">
-                  <path d="M21 12.79A9 9 0 1 1 11.21 3 7 7 0 0 0 21 12.79z"/>
-                </svg>
-              )}
-            </button>
-            <button onClick={() => setSidebarOpen(false)} className="md:hidden text-gray-400 hover:text-gray-600 leading-none" title="Close">✕</button>
-          </div>
-        </div>
-        <div className="flex items-center justify-between mt-1">
-          <span className="text-xs text-gray-400">{loginUser}</span>
-          <button onClick={handleLogout} className="text-xs text-gray-400 hover:text-red-500" title="Sign out">Sign out</button>
-        </div>
-      </div>
-
-      {/* Source selector */}
-      <div className="px-3 py-3 border-b border-gray-200">
-        <div className="flex items-center justify-between mb-1">
-          <label className="text-xs text-gray-500">Source</label>
-          <NavLink to="/sources?new=1" className="text-xs text-blue-400 hover:text-blue-600 leading-none" title="New source" onClick={() => setSidebarOpen(false)}>+</NavLink>
-        </div>
-        <select
-          className="w-full text-sm border border-gray-200 rounded px-2 py-1 bg-white focus:outline-none focus:border-blue-400"
-          value={source}
-          onChange={e => setSource(e.target.value)}
-        >
-          {sources.length === 0 && <option value="">—</option>}
-          {sources.map(s => <option key={s.name} value={s.name}>{s.name}</option>)}
-        </select>
-      </div>
-
-      {/* Nav */}
-      <nav className="flex-1 py-2">
-        {NAV.map(({ to, label }) => (
-          <NavLink
-            key={to}
-            to={to}
-            onClick={() => setSidebarOpen(false)}
-            className={({ isActive }) =>
-              `block px-4 py-2 text-sm ${isActive
-                ? 'bg-blue-50 text-blue-700 font-medium'
-                : 'text-gray-600 hover:bg-gray-50'}`
-            }
-          >
-            {label}
-          </NavLink>
-        ))}
-      </nav>
-    </div>
-  )
-
   return (
     <BrowserRouter>
       <div className="flex h-screen">
 
-        {/* Mobile overlay */}
-        {sidebarOpen && (
-          <div className="fixed inset-0 z-20 bg-black/30 md:hidden" onClick={() => setSidebarOpen(false)} />
-        )}
-
-        {/* Sidebar — fixed on mobile, static on desktop */}
-        <div className={`
-          fixed inset-y-0 left-0 z-30 w-44 bg-white border-r border-gray-200 transform transition-transform duration-200
-          md:static md:translate-x-0 md:z-auto md:transition-none
-          ${sidebarOpen ? 'translate-x-0' : '-translate-x-full'}
-        `}>
-          {sidebar}
-        </div>
+        <Sidebar
+          expanded={sidebarExpanded}
+          setExpanded={setSidebarExpanded}
+          loginUser={loginUser}
+          onLogout={handleLogout}
+        />
 
         {/* Main */}
-        <div className="flex-1 overflow-auto flex flex-col min-w-0">
-          {/* Mobile top bar */}
-          <div className="md:hidden flex items-center px-3 py-2 bg-white border-b border-gray-200">
-            <button onClick={() => setSidebarOpen(true)} className="text-gray-500 hover:text-gray-700 mr-3 text-lg leading-none">☰</button>
-            <span className="text-sm font-semibold text-gray-800 tracking-wide uppercase">Dataflow</span>
-          </div>
+        <div className="flex-1 overflow-hidden flex flex-col min-w-0">
+          <StatusBar sources={sources} source={source} setSource={setSource} />
 
           {(staleSources.size > 0 || staleStacks.size > 0) && (
             <div className="bg-amber-50 border-b border-amber-200 px-4 py-1.5 text-xs text-amber-800 flex flex-wrap items-center gap-x-3 gap-y-1">
diff --git a/ui/src/components/Sidebar.jsx b/ui/src/components/Sidebar.jsx
new file mode 100644
index 0000000..1c5683f
--- /dev/null
+++ b/ui/src/components/Sidebar.jsx
@@ -0,0 +1,183 @@
+import { NavLink } from 'react-router-dom'
+
+const NAV = [
+  {
+    to: '/sources',
+    label: 'Sources',
+    icon: (
+      <svg width="18" height="18" viewBox="0 0 20 20" fill="none" stroke="currentColor" strokeWidth="1.6" strokeLinecap="round" strokeLinejoin="round">
+        <ellipse cx="10" cy="5.5" rx="7" ry="2.5"/>
+        <path d="M3 5.5v9c0 1.4 3.1 2.5 7 2.5s7-1.1 7-2.5v-9"/>
+        <path d="M3 10.5c0 1.4 3.1 2.5 7 2.5s7-1.1 7-2.5"/>
+      </svg>
+    ),
+  },
+  {
+    to: '/import',
+    label: 'Import',
+    icon: (
+      <svg width="18" height="18" viewBox="0 0 20 20" fill="none" stroke="currentColor" strokeWidth="1.6" strokeLinecap="round" strokeLinejoin="round">
+        <line x1="10" y1="3" x2="10" y2="14"/>
+        <polyline points="6,10 10,14 14,10"/>
+        <line x1="3" y1="18" x2="17" y2="18"/>
+      </svg>
+    ),
+  },
+  {
+    to: '/rules',
+    label: 'Rules',
+    icon: (
+      <svg width="18" height="18" viewBox="0 0 20 20" fill="none" stroke="currentColor" strokeWidth="1.6" strokeLinecap="round" strokeLinejoin="round">
+        <polyline points="6,7 2,10 6,13"/>
+        <polyline points="14,7 18,10 14,13"/>
+        <line x1="12" y1="4" x2="8" y2="16"/>
+      </svg>
+    ),
+  },
+  {
+    to: '/mappings',
+    label: 'Mappings',
+    icon: (
+      <svg width="18" height="18" viewBox="0 0 20 20" fill="none" stroke="currentColor" strokeWidth="1.6" strokeLinecap="round" strokeLinejoin="round">
+        <line x1="2" y1="7" x2="12" y2="7"/>
+        <polyline points="9,4 12,7 9,10"/>
+        <line x1="8" y1="13" x2="18" y2="13"/>
+        <polyline points="11,10 14,13 11,16"/>
+      </svg>
+    ),
+  },
+  {
+    to: '/remap',
+    label: 'Remap',
+    icon: (
+      <svg width="18" height="18" viewBox="0 0 20 20" fill="none" stroke="currentColor" strokeWidth="1.6" strokeLinecap="round" strokeLinejoin="round">
+        <polyline points="2,8 2,4 6,4"/>
+        <path d="M2 4a8 8 0 0 1 14 2"/>
+        <polyline points="18,12 18,16 14,16"/>
+        <path d="M18 16a8 8 0 0 1-14-2"/>
+      </svg>
+    ),
+  },
+  {
+    to: '/records',
+    label: 'Records',
+    icon: (
+      <svg width="18" height="18" viewBox="0 0 20 20" fill="none" stroke="currentColor" strokeWidth="1.6" strokeLinecap="round" strokeLinejoin="round">
+        <rect x="2" y="3" width="16" height="14" rx="1.5"/>
+        <line x1="2" y1="8" x2="18" y2="8"/>
+        <line x1="7" y1="8" x2="7" y2="17"/>
+      </svg>
+    ),
+  },
+  {
+    to: '/pivot',
+    label: 'Pivot',
+    icon: (
+      <svg width="18" height="18" viewBox="0 0 20 20" fill="none" stroke="currentColor" strokeWidth="1.6" strokeLinecap="round" strokeLinejoin="round">
+        <rect x="2" y="2" width="7" height="7" rx="1"/>
+        <rect x="11" y="2" width="7" height="7" rx="1"/>
+        <rect x="2" y="11" width="7" height="7" rx="1"/>
+        <rect x="11" y="11" width="7" height="7" rx="1"/>
+      </svg>
+    ),
+  },
+  {
+    to: '/stacks',
+    label: 'Stacks',
+    icon: (
+      <svg width="18" height="18" viewBox="0 0 20 20" fill="none" stroke="currentColor" strokeWidth="1.6" strokeLinecap="round" strokeLinejoin="round">
+        <polygon points="10,2 18,6 10,10 2,6"/>
+        <polyline points="2,10 10,14 18,10"/>
+        <polyline points="2,14 10,18 18,14"/>
+      </svg>
+    ),
+  },
+  {
+    to: '/log',
+    label: 'Log',
+    icon: (
+      <svg width="18" height="18" viewBox="0 0 20 20" fill="none" stroke="currentColor" strokeWidth="1.6" strokeLinecap="round" strokeLinejoin="round">
+        <circle cx="10" cy="10" r="8"/>
+        <polyline points="10,5 10,10 14,12"/>
+      </svg>
+    ),
+  },
+]
+
+export default function Sidebar({ expanded, setExpanded, loginUser, onLogout }) {
+  return (
+    <div
+      className="bg-white border-r border-gray-200 flex flex-col shrink-0 overflow-hidden transition-all duration-150"
+      style={{ width: expanded ? 200 : 48 }}
+    >
+      {/* Header */}
+      <div className="h-12 flex items-center px-3 border-b border-gray-100 gap-2 shrink-0">
+        <button
+          onClick={() => setExpanded(e => !e)}
+          className="w-8 h-8 flex items-center justify-center rounded hover:bg-gray-100 text-gray-400 shrink-0"
+          title="Toggle sidebar"
+        >
+          <svg width="16" height="16" viewBox="0 0 16 16" fill="none">
+            <rect x="1" y="3" width="14" height="1.5" rx="0.75" fill="currentColor"/>
+            <rect x="1" y="7.25" width="14" height="1.5" rx="0.75" fill="currentColor"/>
+            <rect x="1" y="11.5" width="14" height="1.5" rx="0.75" fill="currentColor"/>
+          </svg>
+        </button>
+        <span
+          className="text-xs font-semibold text-gray-600 tracking-wide uppercase whitespace-nowrap transition-opacity duration-100"
+          style={{ opacity: expanded ? 1 : 0, pointerEvents: expanded ? 'auto' : 'none' }}
+        >
+          Dataflow
+        </span>
+      </div>
+
+      {/* Nav */}
+      <nav className="flex flex-col gap-0.5 p-2 flex-1">
+        {NAV.map(({ to, label, icon }) => (
+          <NavLink
+            key={to}
+            to={to}
+            title={!expanded ? label : undefined}
+            className={({ isActive }) =>
+              `flex items-center gap-3 px-2 py-2 rounded w-full transition-colors ${
+                isActive
+                  ? 'bg-blue-50 text-blue-700'
+                  : 'text-gray-500 hover:bg-gray-100 hover:text-gray-800'
+              }`
+            }
+          >
+            <span className="shrink-0">{icon}</span>
+            <span
+              className="text-sm whitespace-nowrap transition-opacity duration-100"
+              style={{ opacity: expanded ? 1 : 0, pointerEvents: expanded ? 'auto' : 'none', width: expanded ? 'auto' : 0, overflow: 'hidden' }}
+            >
+              {label}
+            </span>
+          </NavLink>
+        ))}
+      </nav>
+
+      {/* User / logout */}
+      <div className="border-t border-gray-100 px-3 py-2.5 flex items-center gap-2 shrink-0 overflow-hidden">
+        <div
+          className="w-6 h-6 rounded-full bg-gray-200 text-gray-500 flex items-center justify-center shrink-0 text-xs font-medium"
+          title={!expanded ? loginUser : undefined}
+        >
+          {loginUser ? loginUser[0].toUpperCase() : '?'}
+        </div>
+        <div
+          className="flex-1 flex items-center justify-between min-w-0 transition-opacity duration-100"
+          style={{ opacity: expanded ? 1 : 0, pointerEvents: expanded ? 'auto' : 'none', width: expanded ? 'auto' : 0, overflow: 'hidden' }}
+        >
+          <span className="text-xs text-gray-400 truncate">{loginUser}</span>
+          <button
+            onClick={onLogout}
+            className="text-xs text-gray-400 hover:text-red-500 ml-2 shrink-0"
+          >
+            Sign out
+          </button>
+        </div>
+      </div>
+    </div>
+  )
+}
diff --git a/ui/src/components/StatusBar.jsx b/ui/src/components/StatusBar.jsx
new file mode 100644
index 0000000..f430104
--- /dev/null
+++ b/ui/src/components/StatusBar.jsx
@@ -0,0 +1,53 @@
+import { NavLink } from 'react-router-dom'
+import useTheme from '../theme.jsx'
+
+export default function StatusBar({ sources = [], source, setSource }) {
+  const { dark, setDark } = useTheme()
+
+  return (
+    <div className="bg-white border-b border-gray-200 px-3 h-9 flex items-center gap-3 shrink-0 text-xs">
+      <span className="text-gray-400">Source</span>
+      <select
+        value={source || ''}
+        onChange={e => setSource(e.target.value)}
+        disabled={sources.length === 0}
+        className="border border-gray-200 rounded px-2 py-0.5 bg-white focus:outline-none focus:border-blue-400"
+      >
+        {sources.length === 0
+          ? <option value="">— no sources —</option>
+          : sources.map(s => <option key={s.name} value={s.name}>{s.name}</option>)}
+      </select>
+      <NavLink
+        to="/sources?new=1"
+        className="text-blue-400 hover:text-blue-600 leading-none"
+        title="New source"
+      >+</NavLink>
+
+      <div className="ml-auto">
+        <button
+          onClick={() => setDark(d => !d)}
+          className="w-6 h-6 flex items-center justify-center rounded hover:bg-gray-100 text-gray-500"
+          title={dark ? 'Switch to light mode' : 'Switch to dark mode'}
+        >
+          {dark ? (
+            <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round">
+              <circle cx="12" cy="12" r="4"/>
+              <line x1="12" y1="2" x2="12" y2="5"/>
+              <line x1="12" y1="19" x2="12" y2="22"/>
+              <line x1="4.93" y1="4.93" x2="7.05" y2="7.05"/>
+              <line x1="16.95" y1="16.95" x2="19.07" y2="19.07"/>
+              <line x1="2" y1="12" x2="5" y2="12"/>
+              <line x1="19" y1="12" x2="22" y2="12"/>
+              <line x1="4.93" y1="19.07" x2="7.05" y2="16.95"/>
+              <line x1="16.95" y1="7.05" x2="19.07" y2="4.93"/>
+            </svg>
+          ) : (
+            <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round">
+              <path d="M21 12.79A9 9 0 1 1 11.21 3 7 7 0 0 0 21 12.79z"/>
+            </svg>
+          )}
+        </button>
+      </div>
+    </div>
+  )
+}
diff --git a/ui/src/pages/Pivot.jsx b/ui/src/pages/Pivot.jsx
index 9bb22a8..a85e956 100644
--- a/ui/src/pages/Pivot.jsx
+++ b/ui/src/pages/Pivot.jsx
@@ -253,7 +253,6 @@ export default function Pivot({ source }) {
         viewer.addEventListener('perspective-click', perspClickHandlerRef.current)
 
         await viewer.load(worker)
-        viewer.setAttribute('theme', dark ? 'Pro Dark' : 'Pro Light')
 
         const plugin = await viewer.getPlugin()
         const savedLayout = localStorage.getItem(LAYOUT_KEY(selectedView))
@@ -267,6 +266,7 @@ export default function Pivot({ source }) {
           await plugin.restore(DEFAULT_PLUGIN_CONFIG)
         }
         await viewer.flush()
+        viewer.setAttribute('theme', dark ? 'Pro Dark' : 'Pro Light')
 
         setStatus('ready')
       } catch (err) {