diff --git a/apps/desktop/src/composables/__tests__/useDiffScrollSync.spec.ts b/apps/desktop/src/composables/__tests__/useDiffScrollSync.spec.ts
new file mode 100644
index 0000000000..ca5cbf1227
--- /dev/null
+++ b/apps/desktop/src/composables/__tests__/useDiffScrollSync.spec.ts
@@ -0,0 +1,41 @@
+import { ref } from "vue";
+import { describe, expect, it } from "vitest";
+import type { DiffHunk } from "@/components/diff/DiffHunkBuilder";
+import { useDiffScrollSync } from "@/composables/useDiffScrollSync";
+
+function createPane(scrollTop: number, scrollLeft: number): HTMLElement {
+  return { scrollTop, scrollLeft } as HTMLElement;
+}
+
+function createScrollSync(leftPane: HTMLElement, rightPane: HTMLElement) {
+  return useDiffScrollSync({
+    container: ref<HTMLElement>(),
+    leftPane: ref<HTMLElement | undefined>(leftPane),
+    rightPane: ref<HTMLElement | undefined>(rightPane),
+    hunks: ref<DiffHunk[]>([]),
+  });
+}
+
+describe("useDiffScrollSync", () => {
+  it("syncs vertical and horizontal scroll from left to right", () => {
+    const leftPane = createPane(100, 240);
+    const rightPane = createPane(0, 0);
+    const { syncScroll } = createScrollSync(leftPane, rightPane);
+
+    syncScroll("left");
+
+    expect(rightPane.scrollTop).toBe(100);
+    expect(rightPane.scrollLeft).toBe(240);
+  });
+
+  it("syncs vertical and horizontal scroll from right to left", () => {
+    const leftPane = createPane(0, 0);
+    const rightPane = createPane(80, 160);
+    const { syncScroll } = createScrollSync(leftPane, rightPane);
+
+    syncScroll("right");
+
+    expect(leftPane.scrollTop).toBe(80);
+    expect(leftPane.scrollLeft).toBe(160);
+  });
+});
diff --git a/apps/desktop/src/composables/useDiffScrollSync.ts b/apps/desktop/src/composables/useDiffScrollSync.ts
index 48cc79e24b..5a63ab9bb7 100644
--- a/apps/desktop/src/composables/useDiffScrollSync.ts
+++ b/apps/desktop/src/composables/useDiffScrollSync.ts
@@ -18,6 +18,7 @@ export function useDiffScrollSync({ container, leftPane, rightPane, hunks }: Use
     if (!source || !target) return;
     isSyncingScroll.value = true;
     target.scrollTop = source.scrollTop;
+    target.scrollLeft = source.scrollLeft;
     isSyncingScroll.value = false;
   }