diff --git a/apps/desktop/index.html b/apps/desktop/index.html
index 107925a..25c9b76 100644
--- a/apps/desktop/index.html
+++ b/apps/desktop/index.html
@@ -5,8 +5,12 @@
     <link rel="icon" type="image/svg+xml" href="/vite.svg" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <link rel="preconnect" href="https://fonts.bunny.net" crossorigin />
+    <!-- Variable-axis weight range lets us use 450/550 (mid-weights) used in
+         a few UI components. Without the axis syntax Bunny Fonts serves only
+         the discrete weights listed, and browsers would round 450/550 to the
+         nearest defined weight. -->
     <link
-      href="https://fonts.bunny.net/css?family=instrument-serif:400,400i|plus-jakarta-sans:400,500,600,700|geist-mono:400,500&display=swap"
+      href="https://fonts.bunny.net/css?family=instrument-serif:400,400i|plus-jakarta-sans:wght@200..800|geist-mono:wght@100..900&display=swap"
       rel="stylesheet"
     />
     <title>Notebook LM</title>
diff --git a/apps/desktop/src/components/chat/ChatView.tsx b/apps/desktop/src/components/chat/ChatView.tsx
index 722c5b0..35088e3 100644
--- a/apps/desktop/src/components/chat/ChatView.tsx
+++ b/apps/desktop/src/components/chat/ChatView.tsx
@@ -37,6 +37,8 @@ export function ChatView({ pendingSuggest, onSuggestConsumed, onCitationClick, o
   const setCrossNotebookMode = useAppStore((s) => s.setCrossNotebookMode);
 
   const activeNotebook = notebooks.find((nb) => nb.notebook_id === activeNotebookId) ?? null;
+  const documents = useAppStore((s) => s.documents);
+  const hasDocuments = documents.length > 0 || crossNotebookMode;
 
   const [input, setInput] = useState('');
   const [isScrolledUp, setIsScrolledUp] = useState(false);
@@ -125,9 +127,16 @@ export function ChatView({ pendingSuggest, onSuggestConsumed, onCitationClick, o
     }
   };
 
+  // BibTeX is available whenever the visible conversation has at least one
+  // message with sources. Sticking to activeSources alone hid the action
+  // after any context reset, even when the persisted messages still had
+  // sources we could export.
+  const hasExportableSources =
+    activeSources.length > 0 || messages.some((m) => m.role === 'assistant');
+
   const overflowItems = [
     { label: 'Export conversation', onClick: handleExport, disabled: messages.length === 0 },
-    { label: 'Export BibTeX', onClick: handleExportBibtex, disabled: activeSources.length === 0 },
+    { label: 'Export BibTeX', onClick: handleExportBibtex, disabled: !hasExportableSources },
     { label: 'Toggle sources', onClick: toggleSourcePanel },
     { label: 'Clear chat', onClick: clearChat, disabled: messages.length === 0 },
   ];
@@ -175,8 +184,19 @@ export function ChatView({ pendingSuggest, onSuggestConsumed, onCitationClick, o
       <div className="chat-messages">
         {messages.length === 0 && (
           <div className="chat-empty">
-            <p>What would you like to know?</p>
-            <QuickChips chips={EMPTY_CHIPS} onSelect={handleSend} />
+            {hasDocuments ? (
+              <>
+                <p>What would you like to know?</p>
+                <QuickChips chips={EMPTY_CHIPS} onSelect={handleSend} />
+              </>
+            ) : (
+              <>
+                <p>No documents here yet.</p>
+                <p className="chat-empty-hint">
+                  Drop a PDF, DOCX, or Markdown file anywhere on this window — or use the <strong>+ Add</strong> button in the sidebar.
+                </p>
+              </>
+            )}
           </div>
         )}
         {messages.map((msg, i) => (
diff --git a/apps/desktop/src/components/documents/DropZone.tsx b/apps/desktop/src/components/documents/DropZone.tsx
deleted file mode 100644
index be3f6f6..0000000
--- a/apps/desktop/src/components/documents/DropZone.tsx
+++ /dev/null
@@ -1,66 +0,0 @@
-import { useRef, useState } from 'react';
-import './documents.css';
-
-interface DropZoneProps {
-  onDrop: (files: FileList) => void;
-  isUploading: boolean;
-}
-
-export function DropZone({ onDrop, isUploading }: DropZoneProps) {
-  const [isDragging, setIsDragging] = useState(false);
-  const fileInputRef = useRef<HTMLInputElement>(null);
-
-  const handleDragOver = (e: React.DragEvent) => {
-    e.preventDefault();
-    setIsDragging(true);
-  };
-
-  const handleDragLeave = () => setIsDragging(false);
-
-  const handleDrop = (e: React.DragEvent) => {
-    e.preventDefault();
-    setIsDragging(false);
-    if (e.dataTransfer.files.length > 0) {
-      onDrop(e.dataTransfer.files);
-    }
-  };
-
-  const handleClick = () => fileInputRef.current?.click();
-
-  const handleChange = (e: React.ChangeEvent<HTMLInputElement>) => {
-    if (e.target.files && e.target.files.length > 0) {
-      onDrop(e.target.files);
-      e.target.value = '';
-    }
-  };
-
-  const className = [
-    'drop-zone',
-    isDragging && 'drop-zone-active',
-    isUploading && 'drop-zone-uploading',
-  ]
-    .filter(Boolean)
-    .join(' ');
-
-  return (
-    <div
-      className={className}
-      onDragOver={handleDragOver}
-      onDragLeave={handleDragLeave}
-      onDrop={handleDrop}
-      onClick={handleClick}
-      role="button"
-      tabIndex={0}
-    >
-      <input
-        ref={fileInputRef}
-        type="file"
-        accept=".pdf,.docx,.pptx,.txt,.md,.py"
-        multiple
-        onChange={handleChange}
-        style={{ display: 'none' }}
-      />
-      {isUploading ? 'Processing...' : 'Drop files here or click to upload'}
-    </div>
-  );
-}
diff --git a/apps/desktop/src/components/layout/AppShell.tsx b/apps/desktop/src/components/layout/AppShell.tsx
index 8863919..c145b77 100644
--- a/apps/desktop/src/components/layout/AppShell.tsx
+++ b/apps/desktop/src/components/layout/AppShell.tsx
@@ -16,6 +16,7 @@ import { KeyboardShortcutsOverlay } from '../ui/KeyboardShortcuts';
 import { ZoteroImportDialog } from '../ui/ZoteroImport';
 import type { SourceChunk } from '../../types';
 import { humanizeError } from '../../utils/errorMessages';
+import { usePaneResize } from '../../hooks/usePaneResize';
 import './layout.css';
 
 function isWizardComplete(): boolean {
@@ -41,6 +42,21 @@ export function AppShell() {
   // the two-way link between a sentence and its source card is visible.
   const [hoveredSourceIndex, setHoveredSourceIndex] = useState<number | null>(null);
 
+  const sidebarResize = usePaneResize({
+    storageKey: 'notebook-lm-sidebar-width',
+    min: 200,
+    max: 420,
+    from: 'left',
+    initial: 240,
+  });
+  const sourcePanelResize = usePaneResize({
+    storageKey: 'notebook-lm-source-panel-width',
+    min: 240,
+    max: 520,
+    from: 'right',
+    initial: 280,
+  });
+
   // Global keyboard shortcuts
   useEffect(() => {
     const handler = (e: KeyboardEvent) => {
@@ -71,8 +87,17 @@ export function AppShell() {
         useAppStore.getState().newChat();
         return;
       }
-      // ? — keyboard shortcuts (only when not typing in an input)
-      if (e.key === '?' && !paletteOpen) {
+      // ⌘-Shift-/ — keyboard shortcuts overlay. The bare `?` form used to
+      // be blocked whenever the chat textarea had focus (which is almost
+      // always), so the shortcut was effectively unreachable. A modifier
+      // shortcut is always reachable. The bare ? still works when no text
+      // input is focused.
+      if (e.metaKey && e.shiftKey && e.key === '?') {
+        e.preventDefault();
+        setShortcutsOpen((v) => !v);
+        return;
+      }
+      if (e.key === '?' && !paletteOpen && !e.metaKey && !e.ctrlKey) {
         const tag = (e.target as HTMLElement)?.tagName;
         if (tag !== 'INPUT' && tag !== 'TEXTAREA') {
           e.preventDefault();
@@ -238,8 +263,15 @@ export function AppShell() {
 
   return (
     <>
-      <div className="app-shell">
+      <div
+        className="app-shell"
+        style={{
+          ['--sidebar-width' as string]: `${sidebarResize.width}px`,
+          ['--source-panel-width' as string]: `${sourcePanelResize.width}px`,
+        }}
+      >
         <Sidebar onOpenZotero={() => setZoteroOpen(true)} />
+        <div className="pane-resizer" aria-label="Resize sidebar" {...sidebarResize.handleProps} />
         <ChatView
           pendingSuggest={pendingSuggest}
           onSuggestConsumed={() => setPendingSuggest(null)}
@@ -249,6 +281,11 @@ export function AppShell() {
           }}
           onCitationHover={setHoveredSourceIndex}
         />
+        <div
+          className="pane-resizer"
+          aria-label="Resize sources panel"
+          {...sourcePanelResize.handleProps}
+        />
         <SourcePanel
           onSourceClick={(source) => openSource(source)}
           hoveredIndex={hoveredSourceIndex}
diff --git a/apps/desktop/src/components/layout/layout.css b/apps/desktop/src/components/layout/layout.css
index ff4d865..be7f835 100644
--- a/apps/desktop/src/components/layout/layout.css
+++ b/apps/desktop/src/components/layout/layout.css
@@ -7,6 +7,31 @@
   background: var(--color-bg-primary);
 }
 
+/* Drag handle between panes. Invisible until hover so the default look
+ * matches the pre-resize app. Expands to 3px with a sage tint on hover so
+ * the affordance is obvious once the user moves the cursor there. */
+.pane-resizer {
+  flex-shrink: 0;
+  width: 3px;
+  margin: 0 -1px;
+  cursor: col-resize;
+  background: transparent;
+  -webkit-app-region: no-drag;
+  transition: background var(--duration-fast) var(--ease-out);
+  position: relative;
+  z-index: 1;
+}
+
+.pane-resizer:hover,
+.pane-resizer:focus-visible {
+  background: var(--color-accent-subtle);
+}
+
+.pane-resizer:focus-visible {
+  outline: none;
+  box-shadow: 0 0 0 1px var(--color-accent);
+}
+
 /* ---- Sidebar ---- */
 
 .sidebar {
@@ -755,7 +780,7 @@
   z-index: 1000;
   background: var(--color-bg-elevated);
   border: 1px solid var(--color-border);
-  border-radius: var(--radius-card);
+  border-radius: var(--radius-modal);
   box-shadow: var(--shadow-lg);
   padding: var(--space-1);
   min-width: 160px;
diff --git a/apps/desktop/src/components/ui/CommandPalette.tsx b/apps/desktop/src/components/ui/CommandPalette.tsx
index 53698a5..d8ec14a 100644
--- a/apps/desktop/src/components/ui/CommandPalette.tsx
+++ b/apps/desktop/src/components/ui/CommandPalette.tsx
@@ -7,21 +7,47 @@ interface PaletteItem {
   id: string;
   label: string;
   section: 'Notebooks' | 'Documents' | 'Actions';
+  /** Optional keyboard shortcut hint rendered on the right side of the row. */
+  shortcut?: string;
   onSelect: () => void;
 }
 
+/**
+ * Tokenized fuzzy-ish scorer. Splits the query on whitespace and requires
+ * every token to be present in the label (case-insensitive). Rewards token
+ * prefix matches and contiguous runs. `"note sum"` → matches "Summarize
+ * this notebook" and "Notebook — Summary".
+ */
 function matchScore(query: string, label: string): number {
-  const q = query.toLowerCase();
+  const q = query.toLowerCase().trim();
+  if (!q) return 1;
   const l = label.toLowerCase();
-  if (l.startsWith(q)) return 2; // prefix match
-  if (l.includes(q)) return 1;   // substring match
-  return 0;
+  const tokens = q.split(/\s+/);
+  let score = 0;
+  for (const t of tokens) {
+    if (!l.includes(t)) return 0;
+    // Prefix at the start of the label is the strongest signal.
+    if (l.startsWith(t)) score += 3;
+    // Prefix of any word inside the label is next.
+    else if (new RegExp(`\\b${t}`).test(l)) score += 2;
+    else score += 1;
+  }
+  return score;
 }
 
-export function CommandPalette({ open, onClose, onZoteroImport }: { open: boolean; onClose: () => void; onZoteroImport?: () => void }) {
+export function CommandPalette({
+  open,
+  onClose,
+  onZoteroImport,
+}: {
+  open: boolean;
+  onClose: () => void;
+  onZoteroImport?: () => void;
+}) {
   const [query, setQuery] = useState('');
   const [selectedIndex, setSelectedIndex] = useState(0);
   const inputRef = useRef<HTMLInputElement>(null);
+  const containerRef = useRef<HTMLDivElement>(null);
   const notebooks = useAppStore((s) => s.notebooks);
   const documents = useAppStore((s) => s.documents);
   const messages = useAppStore((s) => s.messages);
@@ -43,6 +69,25 @@ export function CommandPalette({ open, onClose, onZoteroImport }: { open: boolea
       if (e.key === 'Escape') {
         e.preventDefault();
         onClose();
+        return;
+      }
+      // Minimal focus trap: keep Tab inside the palette container.
+      if (e.key === 'Tab') {
+        const root = containerRef.current;
+        if (!root) return;
+        const focusables = root.querySelectorAll<HTMLElement>(
+          'input, button, [tabindex]:not([tabindex="-1"])',
+        );
+        if (focusables.length === 0) return;
+        const first = focusables[0];
+        const last = focusables[focusables.length - 1];
+        if (e.shiftKey && document.activeElement === first) {
+          e.preventDefault();
+          last.focus();
+        } else if (!e.shiftKey && document.activeElement === last) {
+          e.preventDefault();
+          first.focus();
+        }
       }
     };
     window.addEventListener('keydown', handler);
@@ -60,30 +105,45 @@ export function CommandPalette({ open, onClose, onZoteroImport }: { open: boolea
       id: `nb-${nb.notebook_id}`,
       label: nb.title,
       section: 'Notebooks' as const,
-      onSelect: () => { setActiveNotebookId(nb.notebook_id); onClose(); },
+      onSelect: () => {
+        setActiveNotebookId(nb.notebook_id);
+        onClose();
+      },
     })),
     ...documents.map((doc) => ({
       id: `doc-${doc.source_path}`,
       label: doc.filename,
       section: 'Documents' as const,
-      onSelect: () => { setPreviewDocument(doc); onClose(); },
+      onSelect: () => {
+        setPreviewDocument(doc);
+        onClose();
+      },
     })),
     {
       id: 'action-new-chat',
       label: 'New chat',
       section: 'Actions',
-      onSelect: () => { newChat(); onClose(); },
+      shortcut: '⌘N',
+      onSelect: () => {
+        newChat();
+        onClose();
+      },
     },
     {
       id: 'action-toggle-sources',
       label: 'Toggle source panel',
       section: 'Actions',
-      onSelect: () => { toggleSourcePanel(); onClose(); },
+      shortcut: '⌘/',
+      onSelect: () => {
+        toggleSourcePanel();
+        onClose();
+      },
     },
     {
       id: 'action-export',
       label: 'Export conversation',
       section: 'Actions',
+      shortcut: '⌘⇧E',
       onSelect: () => {
         if (messages.length > 0) {
           exportConversation('Notebook LM Conversation', messages);
@@ -91,12 +151,19 @@ export function CommandPalette({ open, onClose, onZoteroImport }: { open: boolea
         onClose();
       },
     },
-    ...(onZoteroImport ? [{
-      id: 'action-zotero',
-      label: 'Import from Zotero',
-      section: 'Actions' as const,
-      onSelect: () => { onZoteroImport(); onClose(); },
-    }] : []),
+    ...(onZoteroImport
+      ? [
+          {
+            id: 'action-zotero',
+            label: 'Import from Zotero',
+            section: 'Actions' as const,
+            onSelect: () => {
+              onZoteroImport();
+              onClose();
+            },
+          },
+        ]
+      : []),
   ];
 
   const filtered = query
@@ -136,7 +203,14 @@ export function CommandPalette({ open, onClose, onZoteroImport }: { open: boolea
 
   return (
     <div className="palette-backdrop" onClick={onClose}>
-      <div className="palette-container" onClick={(e) => e.stopPropagation()}>
+      <div
+        ref={containerRef}
+        className="palette-container"
+        role="dialog"
+        aria-modal="true"
+        aria-label="Command palette"
+        onClick={(e) => e.stopPropagation()}
+      >
         <input
           ref={inputRef}
           className="palette-input"
@@ -144,11 +218,10 @@ export function CommandPalette({ open, onClose, onZoteroImport }: { open: boolea
           onChange={(e) => setQuery(e.target.value)}
           onKeyDown={handleKeyDown}
           placeholder="Search notebooks, documents, actions..."
+          aria-label="Command palette input"
         />
         <div className="palette-results">
-          {sections.length === 0 && (
-            <div className="palette-empty">No results</div>
-          )}
+          {sections.length === 0 && <div className="palette-empty">No results</div>}
           {sections.map((section) => (
             <div key={section.name} className="palette-section">
               <div className="palette-section-title">{section.name}</div>
@@ -162,7 +235,10 @@ export function CommandPalette({ open, onClose, onZoteroImport }: { open: boolea
                     onClick={item.onSelect}
                     onMouseEnter={() => setSelectedIndex(idx)}
                   >
-                    {item.label}
+                    <span className="palette-item-label">{item.label}</span>
+                    {item.shortcut && (
+                      <kbd className="palette-item-shortcut">{item.shortcut}</kbd>
+                    )}
                   </button>
                 );
               })}
diff --git a/apps/desktop/src/components/ui/command-palette.css b/apps/desktop/src/components/ui/command-palette.css
index 874a1f4..ca731f8 100644
--- a/apps/desktop/src/components/ui/command-palette.css
+++ b/apps/desktop/src/components/ui/command-palette.css
@@ -62,21 +62,50 @@
 }
 
 .palette-item {
-  display: block;
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: var(--space-3);
   width: 100%;
   padding: var(--space-2) var(--space-4);
   background: transparent;
   border: none;
+  border-left: 2px solid transparent;
   font-family: var(--font-sans);
   font-size: var(--text-sm);
   color: var(--color-text-secondary);
   text-align: left;
   cursor: pointer;
-  transition: background 80ms ease;
+  transition: background 80ms ease, border-color 80ms ease, color 80ms ease;
 }
 
-.palette-item:hover,
-.palette-item.selected {
+.palette-item:hover {
   background: var(--color-bg-hover);
   color: var(--color-text-primary);
 }
+
+.palette-item.selected {
+  background: var(--color-bg-active);
+  color: var(--color-text-primary);
+  border-left-color: var(--color-accent);
+}
+
+.palette-item-label {
+  flex: 1;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.palette-item-shortcut {
+  font-family: var(--font-mono);
+  font-variant-numeric: tabular-nums;
+  font-size: 11px;
+  letter-spacing: 0.02em;
+  color: var(--color-text-muted);
+  padding: 2px 8px;
+  background: var(--color-bg-primary);
+  border: 1px solid var(--color-border);
+  border-radius: var(--radius-xs);
+  flex-shrink: 0;
+}
diff --git a/apps/desktop/src/components/ui/setup-wizard.css b/apps/desktop/src/components/ui/setup-wizard.css
index 3d22186..2dd4543 100644
--- a/apps/desktop/src/components/ui/setup-wizard.css
+++ b/apps/desktop/src/components/ui/setup-wizard.css
@@ -15,6 +15,10 @@
   display: flex;
   flex-direction: column;
   gap: var(--space-6);
+  background: var(--color-bg-secondary);
+  border: 1px solid var(--color-border);
+  border-radius: var(--radius-modal);
+  box-shadow: var(--shadow-lg);
 }
 
 .wizard-progress {
@@ -28,7 +32,7 @@
   width: 10px;
   height: 10px;
   border-radius: 50%;
-  background: var(--color-border);
+  background: var(--color-border-hover);
   transition: background 200ms ease;
 }
 
@@ -240,7 +244,7 @@
 .wizard-btn-primary {
   padding: 10px 32px;
   background: var(--color-accent);
-  color: #fff;
+  color: #0c0a09;
 }
 
 .wizard-btn-primary:hover:not(:disabled) {
diff --git a/apps/desktop/src/components/ui/zotero-import.css b/apps/desktop/src/components/ui/zotero-import.css
index 5b293ed..07e6c78 100644
--- a/apps/desktop/src/components/ui/zotero-import.css
+++ b/apps/desktop/src/components/ui/zotero-import.css
@@ -148,7 +148,7 @@
 .zotero-btn-primary {
   padding: 10px 24px;
   background: var(--color-accent);
-  color: #fff;
+  color: #0c0a09;
 }
 
 .zotero-btn-primary:hover:not(:disabled) {
diff --git a/apps/desktop/src/design-system/tokens.css b/apps/desktop/src/design-system/tokens.css
index 00a4eb9..7d4d268 100644
--- a/apps/desktop/src/design-system/tokens.css
+++ b/apps/desktop/src/design-system/tokens.css
@@ -217,13 +217,17 @@
   border-radius: 0 var(--radius-xs) var(--radius-xs) 0;
 }
 
-/* ===== Reduced motion ===== */
+/* ===== Reduced motion =====
+   Stop animations entirely rather than playing them at 0.01ms — the prior
+   rule caused shimmer/pulse keyframes to flicker at near-seizure speed
+   instead of ceasing. Transitions collapse to an imperceptible fade so
+   state changes still register without visible motion.
+*/
 @media (prefers-reduced-motion: reduce) {
   *,
   *::before,
   *::after {
-    animation-duration: 0.01ms !important;
-    animation-iteration-count: 1 !important;
+    animation: none !important;
     transition-duration: 0.01ms !important;
     scroll-behavior: auto !important;
   }
diff --git a/apps/desktop/src/hooks/usePaneResize.ts b/apps/desktop/src/hooks/usePaneResize.ts
new file mode 100644
index 0000000..8daada5
--- /dev/null
+++ b/apps/desktop/src/hooks/usePaneResize.ts
@@ -0,0 +1,126 @@
+import { useCallback, useEffect, useRef, useState } from 'react';
+
+interface Options {
+  /** localStorage key — width persists across launches. */
+  storageKey: string;
+  /** Clamp range — prevents a panel from being dragged off-screen. */
+  min: number;
+  max: number;
+  /** Drag direction: `from-left` means dragging left shrinks, drag right grows.
+   *  `from-right` flips it for the right-side panel. */
+  from: 'left' | 'right';
+  /** Initial width if localStorage has nothing saved. */
+  initial: number;
+}
+
+interface Result {
+  width: number;
+  setWidth: (w: number) => void;
+  handleProps: {
+    onMouseDown: (e: React.MouseEvent) => void;
+    onKeyDown: (e: React.KeyboardEvent) => void;
+    role: 'separator';
+    tabIndex: 0;
+    'aria-valuenow': number;
+    'aria-valuemin': number;
+    'aria-valuemax': number;
+    'aria-orientation': 'vertical';
+  };
+}
+
+export function usePaneResize({ storageKey, min, max, from, initial }: Options): Result {
+  const [width, setWidthState] = useState<number>(() => {
+    const saved = typeof window !== 'undefined' ? localStorage.getItem(storageKey) : null;
+    const parsed = saved ? parseInt(saved, 10) : NaN;
+    return Number.isFinite(parsed) ? clamp(parsed, min, max) : initial;
+  });
+
+  const setWidth = useCallback(
+    (w: number) => {
+      const clamped = clamp(w, min, max);
+      setWidthState(clamped);
+      try {
+        localStorage.setItem(storageKey, String(clamped));
+      } catch {
+        // localStorage may be disabled in some contexts (private window);
+        // resize still works in-session, just won't persist.
+      }
+    },
+    [storageKey, min, max],
+  );
+
+  const dragStartRef = useRef<{ startX: number; startWidth: number } | null>(null);
+
+  const onMouseMove = useCallback(
+    (e: MouseEvent) => {
+      const state = dragStartRef.current;
+      if (!state) return;
+      const delta = e.clientX - state.startX;
+      const next = from === 'left' ? state.startWidth + delta : state.startWidth - delta;
+      setWidth(next);
+    },
+    [from, setWidth],
+  );
+
+  const onMouseUp = useCallback(() => {
+    dragStartRef.current = null;
+    document.removeEventListener('mousemove', onMouseMove);
+    document.removeEventListener('mouseup', onMouseUp);
+    document.body.style.cursor = '';
+    document.body.style.userSelect = '';
+  }, [onMouseMove]);
+
+  useEffect(() => {
+    return () => {
+      document.removeEventListener('mousemove', onMouseMove);
+      document.removeEventListener('mouseup', onMouseUp);
+    };
+  }, [onMouseMove, onMouseUp]);
+
+  const onMouseDown = useCallback(
+    (e: React.MouseEvent) => {
+      e.preventDefault();
+      dragStartRef.current = { startX: e.clientX, startWidth: width };
+      document.addEventListener('mousemove', onMouseMove);
+      document.addEventListener('mouseup', onMouseUp);
+      // Prevent text selection while dragging and show resize cursor everywhere.
+      document.body.style.cursor = 'col-resize';
+      document.body.style.userSelect = 'none';
+    },
+    [width, onMouseMove, onMouseUp],
+  );
+
+  const onKeyDown = useCallback(
+    (e: React.KeyboardEvent) => {
+      // Arrow-key resize keeps the handle keyboard-accessible.
+      const step = e.shiftKey ? 40 : 10;
+      if (e.key === 'ArrowLeft') {
+        e.preventDefault();
+        setWidth(width + (from === 'left' ? -step : step));
+      } else if (e.key === 'ArrowRight') {
+        e.preventDefault();
+        setWidth(width + (from === 'left' ? step : -step));
+      }
+    },
+    [width, from, setWidth],
+  );
+
+  return {
+    width,
+    setWidth,
+    handleProps: {
+      onMouseDown,
+      onKeyDown,
+      role: 'separator',
+      tabIndex: 0,
+      'aria-valuenow': width,
+      'aria-valuemin': min,
+      'aria-valuemax': max,
+      'aria-orientation': 'vertical',
+    },
+  };
+}
+
+function clamp(n: number, min: number, max: number): number {
+  return Math.max(min, Math.min(max, n));
+}
diff --git a/backend/notebooklm_backend/services/chat.py b/backend/notebooklm_backend/services/chat.py
index 4e71a4e..7180576 100644
--- a/backend/notebooklm_backend/services/chat.py
+++ b/backend/notebooklm_backend/services/chat.py
@@ -203,7 +203,6 @@ async def stream_reply(
         metrics["llm_ms"] = (time.perf_counter() - llm_start) * 1000
         metrics["total_ms"] = metrics.get("total_ms", 0.0) + metrics["llm_ms"]
         final_reply = "".join(aggregated).strip()
-        final_reply = "".join(aggregated).strip()
         source_count = len(rag_context.sources) if rag_context else None
         self._record_metrics(prompt, notebook_id, metrics, source_count=source_count)
         yield {