diff --git a/apps/web/src/components/chat/ChangedFilesTree.tsx b/apps/web/src/components/chat/ChangedFilesTree.tsx
index 6b49b81401f33..5638949650b16 100644
--- a/apps/web/src/components/chat/ChangedFilesTree.tsx
+++ b/apps/web/src/components/chat/ChangedFilesTree.tsx
@@ -48,7 +48,7 @@ export const ChangedFilesCard = memo(function ChangedFilesCard(props: {
   } = props;
   const syncTimelineLayout = useSyncLayout();
   const hiddenFileCount = totals.count - files.length;
-  const hasDirectories = files.some((file) => /[/\\]/.test(file.path));
+  const hasDirectories = files.some((file) => file.path.includes("/"));
 
   return (
     <div
diff --git a/apps/web/src/lib/turnDiffTree.test.ts b/apps/web/src/lib/turnDiffTree.test.ts
index 582dba9569a8a..4d2fa514ec05d 100644
--- a/apps/web/src/lib/turnDiffTree.test.ts
+++ b/apps/web/src/lib/turnDiffTree.test.ts
@@ -123,4 +123,34 @@ describe("buildTurnDiffTree", () => {
       },
     ]);
   });
+
+  it("keeps literal backslashes in file names apart from directory paths", () => {
+    const tree = buildTurnDiffTree([
+      { path: "back\\slash.txt", kind: "modified", additions: 1, deletions: 0 },
+      { path: "back/slash.txt", kind: "modified", additions: 2, deletions: 0 },
+    ]);
+
+    expect(tree).toEqual([
+      {
+        kind: "directory",
+        name: "back",
+        path: "back",
+        stat: { additions: 2, deletions: 0 },
+        children: [
+          {
+            kind: "file",
+            name: "slash.txt",
+            path: "back/slash.txt",
+            stat: { additions: 2, deletions: 0 },
+          },
+        ],
+      },
+      {
+        kind: "file",
+        name: "back\\slash.txt",
+        path: "back\\slash.txt",
+        stat: { additions: 1, deletions: 0 },
+      },
+    ]);
+  });
 });
diff --git a/apps/web/src/lib/turnDiffTree.ts b/apps/web/src/lib/turnDiffTree.ts
index e841e18ce24d2..05346f900cce3 100644
--- a/apps/web/src/lib/turnDiffTree.ts
+++ b/apps/web/src/lib/turnDiffTree.ts
@@ -32,11 +32,10 @@ interface MutableDirectoryNode {
 
 let sortCollator: Intl.Collator | undefined;
 
+// Checkpoint paths come from Git, which separates directories with "/" on every
+// platform. A backslash is part of a POSIX file name, not a separator.
 function normalizePathSegments(pathValue: string): string[] {
-  return pathValue
-    .replaceAll("\\", "/")
-    .split("/")
-    .filter((segment) => segment.length > 0);
+  return pathValue.split("/").filter((segment) => segment.length > 0);
 }
 
 function compareByName(a: { name: string }, b: { name: string }): number {