diff --git a/kb-viz/frontend/src/components/AppShell.tsx b/kb-viz/frontend/src/components/AppShell.tsx
index 7dc7869..bdf8531 100644
--- a/kb-viz/frontend/src/components/AppShell.tsx
+++ b/kb-viz/frontend/src/components/AppShell.tsx
@@ -1,9 +1,9 @@
 import { useCallback } from 'react';
-import { Mosaic, MosaicWindow, type MosaicNode } from 'react-mosaic-component';
+import { Mosaic, MosaicWindow, type MosaicNode, type MosaicPath, updateTree, createRemoveUpdate } from 'react-mosaic-component';
 import 'react-mosaic-component/react-mosaic-component.css';
 
 import { useStore } from '../lib/use-store';
-import { layoutStore, type FrameType } from '../state/layout-store';
+import { layoutStore, type FrameType, type PaneNode } from '../state/layout-store';
 import { getFrame } from '../frames/registry';
 import { NodeTooltip } from './NodeTooltip';
 
@@ -34,15 +34,16 @@ export function AppShell() {
       <Mosaic<FrameType>
         renderTile={(type, path) => {
           const Frame = getFrame(type);
+          const paneId = path.length > 0 ? path.join(':') : type;
           return (
             <MosaicWindow<FrameType>
               path={path}
               title={FRAME_LABELS[type] ?? type}
-              toolbarControls={<FrameControls type={type} />}
+              toolbarControls={<FrameControls type={type} path={path} />}
               createNode={() => 'text' as FrameType}
             >
               {/* Width/height passed as 0 — frames that use them fall back to el.clientWidth */}
-              <Frame paneId={type} width={0} height={0} />
+              <Frame paneId={paneId} width={0} height={0} />
             </MosaicWindow>
           );
         }}
@@ -55,7 +56,7 @@ export function AppShell() {
   );
 }
 
-function FrameControls({ type }: { type: FrameType }) {
+function FrameControls({ type, path }: { type: FrameType; path: MosaicPath }) {
   return (
     <div style={{ display: 'flex', gap: 4, alignItems: 'center' }}>
       <button
@@ -71,7 +72,11 @@ function FrameControls({ type }: { type: FrameType }) {
       <button
         className="btn-ghost"
         title="Close frame"
-        onClick={() => layoutStore.getState().removeFrame(type)}
+        onClick={() => {
+          const root = layoutStore.getState().root as MosaicNode<FrameType>;
+          const next = updateTree(root, [createRemoveUpdate(root, path)]);
+          layoutStore.getState().setRoot((next ?? 'semantic') as PaneNode);
+        }}
       >
         ✕
       </button>
diff --git a/kb-viz/frontend/src/frames/TextFrame.tsx b/kb-viz/frontend/src/frames/TextFrame.tsx
index a59263e..6d71730 100644
--- a/kb-viz/frontend/src/frames/TextFrame.tsx
+++ b/kb-viz/frontend/src/frames/TextFrame.tsx
@@ -1,4 +1,4 @@
-import type { ReactNode } from 'react';
+import { type ReactNode, useEffect, useRef } from 'react';
 import { useStore } from '../lib/use-store';
 import { dataStore, getAncestors } from '../state/data-store';
 import { selectionStore } from '../state/selection-store';
@@ -10,36 +10,78 @@ import {
   isTemporal,
   type Annotation,
   type Node,
+  type NodeId,
   type PropertyValue,
 } from '../types/manifest';
 
 import { deriveLabel } from '../lib/derive-label';
 import type { FrameProps } from './registry';
-export function TextFrame(_props: FrameProps) {
-  const nodesById = useStore(dataStore, (s) => s.nodes);
-  const focused = useStore(selectionStore, (s) => s.focused);
+
+export function TextFrame({ paneId }: FrameProps) {
+  const nodesById   = useStore(dataStore, (s) => s.nodes);
+  const focused     = useStore(selectionStore, (s) => s.focused);
+  const pinnedDocId = useStore(viewStore, (s) => s.textPinned[paneId] ?? null);
+
+  if (pinnedDocId) {
+    return <PinnedDocView docId={pinnedDocId} paneId={paneId} />;
+  }
+
+  return (
+    <UnpinnedView
+      paneId={paneId}
+      nodesById={nodesById}
+      focused={focused}
+    />
+  );
+}
+
+// ---------------------------------------------------------------------------
+// Unpinned (follow-selection) mode
+// ---------------------------------------------------------------------------
+
+function UnpinnedView({
+  paneId,
+  nodesById,
+  focused,
+}: {
+  paneId: string;
+  nodesById: Map<string, Node>;
+  focused: string | null;
+}) {
+  const containerRef = useRef<HTMLDivElement>(null);
+
+  // #41: scroll focused node into view when selection changes externally
+  useEffect(() => {
+    if (!focused || !containerRef.current) return;
+    const el = containerRef.current.querySelector(`[data-node-id="${CSS.escape(focused)}"]`);
+    el?.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
+  }, [focused]);
 
   if (!focused) {
     return (
-      <div className="text-frame">
+      <div className="text-frame" ref={containerRef}>
+        <PinBar paneId={paneId} />
         <div className="frame-empty">
           Select a node from any frame to see its text and annotations
         </div>
       </div>
     );
   }
+
   const node = nodesById.get(focused);
   if (!node) {
     return (
-      <div className="text-frame">
+      <div className="text-frame" ref={containerRef}>
+        <PinBar paneId={paneId} />
         <div className="frame-empty">Node not found: {focused}</div>
       </div>
     );
   }
 
   return (
-    <div className="text-frame">
-      <h3 title={node.id}>{deriveLabel(node)}</h3>
+    <div className="text-frame" ref={containerRef}>
+      <PinBar paneId={paneId} />
+      <h3 data-node-id={node.id} title={node.id}>{deriveLabel(node)}</h3>
       <div className="meta">
         <span style={{ fontFamily: 'ui-monospace, monospace', fontSize: 10, color: 'var(--text-muted)', userSelect: 'all' }}>{node.id}</span>
         {' · '}type: <strong>{node.type}</strong>
@@ -57,6 +99,131 @@ export function TextFrame(_props: FrameProps) {
   );
 }
 
+// ---------------------------------------------------------------------------
+// Pinned (comparison) mode — shows all chunks of a fixed document
+// ---------------------------------------------------------------------------
+
+function PinnedDocView({ docId, paneId }: { docId: NodeId; paneId: string }) {
+  const nodesById = useStore(dataStore, (s) => s.nodes);
+  const focused   = useStore(selectionStore, (s) => s.focused);
+  const containerRef = useRef<HTMLDivElement>(null);
+
+  const doc    = nodesById.get(docId);
+  const chunks = (doc?.child_ids ?? [])
+    .map((id) => nodesById.get(id))
+    .filter((n): n is Node => n != null);
+
+  // #41: scroll to focused chunk within the pinned panel
+  useEffect(() => {
+    if (!focused || !containerRef.current) return;
+    const el = containerRef.current.querySelector(`[data-node-id="${CSS.escape(focused)}"]`);
+    el?.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
+  }, [focused]);
+
+  if (!doc) {
+    return (
+      <div className="text-frame">
+        <PinBar paneId={paneId} />
+        <div className="frame-empty">Pinned document not found</div>
+      </div>
+    );
+  }
+
+  return (
+    <div className="text-frame text-frame-pinned" ref={containerRef}>
+      <PinBar paneId={paneId} docLabel={deriveLabel(doc)} />
+
+      <div className="text-frame-pin-doc-header" data-node-id={doc.id}>
+        <span className="type-badge">{doc.type}</span>
+        <h3 style={{ margin: 0 }} title={doc.id}>{deriveLabel(doc)}</h3>
+      </div>
+
+      {chunks.length === 0 && (
+        <div className="frame-empty" style={{ height: 'auto', padding: '16px 0' }}>
+          No child nodes
+        </div>
+      )}
+
+      {chunks.map((chunk) => {
+        const isFocused = focused === chunk.id;
+        return (
+          <div
+            key={chunk.id}
+            data-node-id={chunk.id}
+            className={`text-frame-chunk${isFocused ? ' text-frame-chunk-focused' : ''}`}
+            onClick={() => selectionStore.getState().selectOnly(chunk.id)}
+            role="button"
+            tabIndex={0}
+            onKeyDown={(e) => e.key === 'Enter' && selectionStore.getState().selectOnly(chunk.id)}
+          >
+            <div className="text-frame-chunk-id">{chunk.id}</div>
+            {chunk.text ? (
+              <div className="body">{renderHighlighted(chunk)}</div>
+            ) : (
+              <div className="body" style={{ color: '#6b7280' }}>(no text)</div>
+            )}
+          </div>
+        );
+      })}
+    </div>
+  );
+}
+
+// ---------------------------------------------------------------------------
+// Pin toolbar — document picker + unpin
+// ---------------------------------------------------------------------------
+
+function PinBar({ paneId, docLabel }: { paneId: string; docLabel?: string }) {
+  const byType    = useStore(dataStore, (s) => s.byType);
+  const nodesById = useStore(dataStore, (s) => s.nodes);
+  const pinned    = useStore(viewStore, (s) => s.textPinned[paneId] ?? null);
+
+  const docIds = byType.get('document') ?? [];
+  const docs = (docIds
+    .map((id) => nodesById.get(id))
+    .filter((n): n is Node => n != null) as Node[])
+    .map((n) => ({ node: n, key: deriveLabel(n).replace(/^[^a-zA-Z0-9]+/, '').toLowerCase() }))
+    .sort((a, b) => (a.key < b.key ? -1 : a.key > b.key ? 1 : 0))
+    .map(({ node }) => node);
+
+  const handleChange = (e: React.ChangeEvent<HTMLSelectElement>) => {
+    viewStore.getState().setPinnedDoc(paneId, e.target.value || null);
+  };
+
+  return (
+    <div className="text-frame-pin-bar">
+      <select
+        className="ctrl-select"
+        style={{ flex: 1, fontSize: 11 }}
+        value={pinned ?? ''}
+        onChange={handleChange}
+        title="Pin this panel to a document"
+      >
+        <option value="">pin document to text frame…</option>
+        {docs.map((doc) => (
+          <option key={doc.id} value={doc.id}>
+            {docLabel && doc.id === pinned ? `📌 ${docLabel}` : deriveLabel(doc)}
+          </option>
+        ))}
+      </select>
+      {pinned && (
+        <button
+          className="btn-ghost"
+          style={{ fontSize: 11, padding: '2px 6px' }}
+          title="Unpin"
+          onClick={() => viewStore.getState().setPinnedDoc(paneId, null)}
+        >
+          ✕
+        </button>
+      )}
+    </div>
+  );
+}
+
+// ---------------------------------------------------------------------------
+// Shared sub-components
+// ---------------------------------------------------------------------------
+
 function NodeNav({ node, nodesById }: { node: Node; nodesById: Map<string, Node> }) {
   const manifest = useStore(dataStore, (s) => s.manifest);
 
diff --git a/kb-viz/frontend/src/state/layout-store.ts b/kb-viz/frontend/src/state/layout-store.ts
index e9b354a..efa4627 100644
--- a/kb-viz/frontend/src/state/layout-store.ts
+++ b/kb-viz/frontend/src/state/layout-store.ts
@@ -63,6 +63,12 @@ const PRESETS: Record<string, PaneNode> = {
     second: { direction: 'column', first: 'semantic', second: 'map' },
     splitPercentage: 55,
   },
+  'comparison': {
+    direction: 'row',
+    first: 'text',
+    second: 'text',
+    splitPercentage: 50,
+  },
   single: 'semantic',
 };
 
diff --git a/kb-viz/frontend/src/state/view-store.ts b/kb-viz/frontend/src/state/view-store.ts
index de28fe3..5a0e923 100644
--- a/kb-viz/frontend/src/state/view-store.ts
+++ b/kb-viz/frontend/src/state/view-store.ts
@@ -34,6 +34,10 @@ export interface PaneViewState {
   rotationOrbit?: number;
 }
 
+export interface TextFrameConfig {
+  pinnedDocId: NodeId | null;
+}
+
 export interface ViewState {
   level: Level;
   colorBy: ColorBy;
@@ -45,12 +49,16 @@ export interface ViewState {
   // Per-frame type config
   frameConfigs: Partial<Record<FrameType, FrameConfig>>;
 
+  // Per-pane text frame pinned document (keyed by mosaic path joined with ':')
+  textPinned: Record<string, NodeId | null>;
+
   setLevel: (l: Level) => void;
   setColorBy: (c: ColorBy) => void;
   drillInto: (id: NodeId, childLevel: Level) => void;
   drillOut: () => void;
   setPaneViewState: (frame: FrameType, state: PaneViewState) => void;
   setFrameConfig: (frame: FrameType, config: Partial<FrameConfig>) => void;
+  setPinnedDoc: (paneId: string, docId: NodeId | null) => void;
 }
 
 const LEVEL_ORDER: Record<Level, number> = { document: 0, chunk: 1, expression: 2 };
@@ -68,6 +76,7 @@ export const viewStore = createStore<ViewState>()(
       scope: 'global',
       paneViewStates: {},
       frameConfigs: { ...DEFAULT_FRAME_CONFIGS },
+      textPinned: {},
 
       setLevel: (newLevel) => {
         const currentLevel = get().level;
@@ -124,6 +133,11 @@ export const viewStore = createStore<ViewState>()(
             [frame]: { ...(s.frameConfigs[frame] ?? {}), ...config },
           },
         })),
+
+      setPinnedDoc: (paneId, docId) =>
+        set((s) => ({
+          textPinned: { ...s.textPinned, [paneId]: docId },
+        })),
     }),
     {
       name: 'kb-viz:view',
@@ -132,6 +146,7 @@ export const viewStore = createStore<ViewState>()(
         colorBy: s.colorBy,
         paneViewStates: s.paneViewStates,
         frameConfigs: s.frameConfigs,
+        textPinned: s.textPinned,
       }),
     },
   ),
diff --git a/kb-viz/frontend/src/styles.css b/kb-viz/frontend/src/styles.css
index 1d868e4..0cbca3f 100644
--- a/kb-viz/frontend/src/styles.css
+++ b/kb-viz/frontend/src/styles.css
@@ -211,10 +211,12 @@ body {
 .text-frame {
   border-left: var(--border-width) solid var(--border);
   padding: 14px;
+  height: 100%;
   overflow-y: auto;
   background: var(--surface);
   display: flex;
   flex-direction: column;
+  box-sizing: border-box;
 }
 .text-frame h3 {
   margin: 0 0 4px;
@@ -247,6 +249,47 @@ body {
   font-weight: 600;
 }
 
+/* ── TextFrame pin bar & comparison mode ─────────────────────────────────── */
+.text-frame-pin-bar {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  margin-bottom: 10px;
+}
+
+.text-frame-pin-doc-header {
+  display: flex;
+  align-items: baseline;
+  gap: 8px;
+  margin-bottom: 12px;
+  padding-bottom: 8px;
+  border-bottom: var(--border-width) solid var(--border);
+}
+
+.text-frame-chunk {
+  padding: 10px 12px;
+  margin-bottom: 6px;
+  border: var(--border-width) solid var(--border);
+  border-radius: var(--radius);
+  cursor: pointer;
+  transition: border-color 120ms, background 120ms;
+}
+.text-frame-chunk:hover {
+  border-color: var(--border-light);
+  background: var(--accent-dim);
+}
+.text-frame-chunk-focused {
+  border-color: var(--selected);
+  background: rgba(240, 80, 40, 0.07);
+}
+.text-frame-chunk-id {
+  font-size: 9px;
+  color: var(--text-muted);
+  font-family: ui-monospace, monospace;
+  margin-bottom: 5px;
+  user-select: all;
+}
+
 /* ── Annotation span highlights ───────────────────────────────────────────── */
 .span-geo     { background: var(--loc-bg);    color: var(--loc);    border-radius: 3px; padding: 0 3px; }
 .span-time    { background: var(--time-bg);   color: var(--time);   border-radius: 3px; padding: 0 3px; }