diff --git a/frontend/src/components/DiffCard.tsx b/frontend/src/components/DiffCard.tsx
index c224363b..2a776475 100644
--- a/frontend/src/components/DiffCard.tsx
+++ b/frontend/src/components/DiffCard.tsx
@@ -24,6 +24,7 @@ import type { TaskAttempt } from 'shared/types';
 import { useReview, type ReviewDraft } from '@/contexts/ReviewProvider';
 import { CommentWidgetLine } from '@/components/diff/CommentWidgetLine';
 import { ReviewCommentRenderer } from '@/components/diff/ReviewCommentRenderer';
+import { useDiffViewMode } from '@/stores/useDiffViewStore';
 
 type Props = {
   diff: Diff;
@@ -53,6 +54,7 @@ export default function DiffCard({
   const { config } = useUserSystem();
   const theme = getActualTheme(config?.theme);
   const { comments, drafts, setDraft } = useReview();
+  const globalMode = useDiffViewMode();
 
   const oldName = diff.oldPath || undefined;
   const newName = diff.newPath || oldName || 'unknown';
@@ -247,7 +249,9 @@ export default function DiffCard({
             diffViewWrap={false}
             diffViewTheme={theme}
             diffViewHighlight
-            diffViewMode={DiffModeEnum.Unified}
+            diffViewMode={
+              globalMode === 'split' ? DiffModeEnum.Split : DiffModeEnum.Unified
+            }
             diffViewFontSize={12}
             diffViewAddWidget
             onAddWidgetClick={handleAddWidgetClick}
diff --git a/frontend/src/components/NormalizedConversation/EditDiffRenderer.tsx b/frontend/src/components/NormalizedConversation/EditDiffRenderer.tsx
index def0aa2e..ca44542f 100644
--- a/frontend/src/components/NormalizedConversation/EditDiffRenderer.tsx
+++ b/frontend/src/components/NormalizedConversation/EditDiffRenderer.tsx
@@ -11,6 +11,8 @@ import { getHighLightLanguageFromPath } from '@/utils/extToLanguage';
 import { getActualTheme } from '@/utils/theme';
 import '@/styles/diff-style-overrides.css';
 import '@/styles/edit-diff-overrides.css';
+import { useDiffViewMode } from '@/stores/useDiffViewStore';
+import DiffViewSwitch from '@/components/diff-view-switch';
 
 type Props = {
   path: string;
@@ -67,6 +69,7 @@ function EditDiffRenderer({
   const [expanded, setExpanded] = useExpandable(expansionKey, false);
 
   const theme = getActualTheme(config?.theme);
+  const globalMode = useDiffViewMode();
 
   const { hunks, hideLineNumbers, additions, deletions, isValidDiff } = useMemo(
     () => processUnifiedDiff(unifiedDiff, hasLineNumbers),
@@ -104,13 +107,20 @@ function EditDiffRenderer({
 
       {expanded && (
         <div className={'mt-2 border ' + hideLineNumbersClass}>
+          <div className="flex items-center justify-end border-b px-2 py-1">
+            <DiffViewSwitch />
+          </div>
           {isValidDiff ? (
             <DiffView
               data={diffData}
               diffViewWrap={false}
               diffViewTheme={theme}
               diffViewHighlight
-              diffViewMode={DiffModeEnum.Unified}
+              diffViewMode={
+                globalMode === 'split'
+                  ? DiffModeEnum.Split
+                  : DiffModeEnum.Unified
+              }
               diffViewFontSize={12}
             />
           ) : (
diff --git a/frontend/src/components/diff-view-switch.tsx b/frontend/src/components/diff-view-switch.tsx
new file mode 100644
index 00000000..9500a1cc
--- /dev/null
+++ b/frontend/src/components/diff-view-switch.tsx
@@ -0,0 +1,66 @@
+import { Columns, FileText } from 'lucide-react';
+import { Button } from '@/components/ui/button';
+import { cn } from '@/lib/utils';
+import { useDiffViewMode, useDiffViewStore } from '@/stores/useDiffViewStore';
+
+type Props = {
+  className?: string;
+  size?: 'xs' | 'sm';
+};
+
+/**
+ * Segmented switch for Inline vs Split diff modes.
+ * - Left segment: Inline (Unified)
+ * - Right segment: Split
+ * Uses global Zustand store so changing here updates all diffs.
+ */
+export default function DiffViewSwitch({ className, size = 'xs' }: Props) {
+  const mode = useDiffViewMode();
+  const setMode = useDiffViewStore((s) => s.setMode);
+
+  const isUnified = mode === 'unified';
+
+  return (
+    <div
+      className={cn(
+        'inline-flex rounded-md border border-input overflow-hidden',
+        className
+      )}
+      role="group"
+      aria-label="Diff view mode"
+    >
+      <Button
+        variant={isUnified ? 'default' : 'outline'}
+        size={size}
+        className={cn(
+          'rounded-none rounded-l-md h-6',
+          !isUnified && 'bg-background',
+          'gap-1',
+          // Highlight the inner divider when right side is active
+          !isUnified && 'border-r-foreground'
+        )}
+        aria-pressed={isUnified}
+        onClick={() => setMode('unified')}
+      >
+        <FileText className="h-3 w-3" />
+        <span className="text-[11px]">Inline</span>
+      </Button>
+      <Button
+        variant={!isUnified ? 'default' : 'outline'}
+        size={size}
+        className={cn(
+          'rounded-none rounded-r-md -ml-px h-6',
+          isUnified && 'bg-background',
+          'gap-1',
+          // Ensure inner divider reflects active left side
+          isUnified && 'border-l-foreground'
+        )}
+        aria-pressed={!isUnified}
+        onClick={() => setMode('split')}
+      >
+        <Columns className="h-3 w-3" />
+        <span className="text-[11px]">Split</span>
+      </Button>
+    </div>
+  );
+}
diff --git a/frontend/src/components/tasks/TaskDetails/DiffTab.tsx b/frontend/src/components/tasks/TaskDetails/DiffTab.tsx
index a87783ee..2f0cdd7f 100644
--- a/frontend/src/components/tasks/TaskDetails/DiffTab.tsx
+++ b/frontend/src/components/tasks/TaskDetails/DiffTab.tsx
@@ -2,6 +2,7 @@ import { useDiffEntries } from '@/hooks/useDiffEntries';
 import { useMemo, useCallback, useState, useEffect } from 'react';
 import { Loader } from '@/components/ui/loader';
 import { Button } from '@/components/ui/button';
+import DiffViewSwitch from '@/components/diff-view-switch';
 import DiffCard from '@/components/DiffCard';
 import { useDiffSummary } from '@/hooks/useDiffSummary';
 import type { TaskAttempt } from 'shared/types';
@@ -131,14 +132,17 @@ function DiffTabContent({
                 -{deleted}
               </span>
             </span>
-            <Button
-              variant="outline"
-              size="xs"
-              onClick={handleCollapseAll}
-              className="shrink-0"
-            >
-              {allCollapsed ? 'Expand All' : 'Collapse All'}
-            </Button>
+            <div className="flex items-center gap-2">
+              <DiffViewSwitch />
+              <Button
+                variant="outline"
+                size="xs"
+                onClick={handleCollapseAll}
+                className="shrink-0"
+              >
+                {allCollapsed ? 'Expand All' : 'Collapse All'}
+              </Button>
+            </div>
           </div>
         </div>
       )}
diff --git a/frontend/src/stores/useDiffViewStore.ts b/frontend/src/stores/useDiffViewStore.ts
new file mode 100644
index 00000000..31cf54c2
--- /dev/null
+++ b/frontend/src/stores/useDiffViewStore.ts
@@ -0,0 +1,19 @@
+import { create } from 'zustand';
+
+export type DiffViewMode = 'unified' | 'split';
+
+type State = {
+  mode: DiffViewMode;
+  setMode: (mode: DiffViewMode) => void;
+  toggle: () => void;
+};
+
+export const useDiffViewStore = create<State>((set) => ({
+  mode: 'unified',
+  setMode: (mode) => set({ mode }),
+  toggle: () =>
+    set((s) => ({ mode: s.mode === 'unified' ? 'split' : 'unified' })),
+}));
+
+export const useDiffViewMode = () => useDiffViewStore((s) => s.mode);
+export const useToggleDiffViewMode = () => useDiffViewStore((s) => s.toggle);