diff --git a/electron/main/ipc/library.ts b/electron/main/ipc/library.ts
index d10b1cd56..e6267e513 100644
--- a/electron/main/ipc/library.ts
+++ b/electron/main/ipc/library.ts
@@ -164,6 +164,17 @@ export const registerLibraryIpc = (): void => {
     if (dirs.includes(dir)) {
       return { success: false, error: ErrorCode.SCAN_DIR_EXISTS };
     }
+    // 嵌套目录在写入前拒绝：撤销流程若已落库，会连带删掉另一目录覆盖下的已入库曲目
+    const nested = dirs.some(
+      (d) =>
+        dir.startsWith(d + "\\") ||
+        dir.startsWith(d + "/") ||
+        d.startsWith(dir + "\\") ||
+        d.startsWith(dir + "/"),
+    );
+    if (nested) {
+      return { success: false, error: ErrorCode.SCAN_DIR_NESTED };
+    }
     dirs.push(dir);
     store.set("library.scanDirs", dirs);
     libraryLog.info(`添加扫描目录: ${dir}`);
diff --git a/shared/types/errors.ts b/shared/types/errors.ts
index 41ce5e0b3..430ded3cc 100644
--- a/shared/types/errors.ts
+++ b/shared/types/errors.ts
@@ -57,6 +57,8 @@ export enum ErrorCode {
   SCAN_DIR_NOT_FOUND = "SCAN_DIR_NOT_FOUND",
   /** 用户取消了目录选择 */
   SCAN_DIR_NOT_SELECTED = "SCAN_DIR_NOT_SELECTED",
+  /** 目录与已有扫描目录存在嵌套关系 */
+  SCAN_DIR_NESTED = "SCAN_DIR_NESTED",
 
   // 通用
   /** 当前账号没有执行操作所需的权限 */
diff --git a/src/components/library/FolderManager.vue b/src/components/library/FolderManager.vue
index 74e08fecb..ac063917f 100644
--- a/src/components/library/FolderManager.vue
+++ b/src/components/library/FolderManager.vue
@@ -1,5 +1,6 @@
 <script setup lang="ts">
 import { useLibraryStore } from "@/stores/library";
+import { ErrorCode } from "@shared/types/errors";
 import { toast } from "@/composables/useToast";
 import IconLucideFolder from "~icons/lucide/folder";
 import IconLucideFolderPlus from "~icons/lucide/folder-plus";
@@ -30,7 +31,7 @@ const handleAdd = async (): Promise<void> => {
     const res = await libraryStore.addScanDir();
     if (res.success) {
       emit("added");
-    } else if (res.error === "nested") {
+    } else if (res.error === ErrorCode.SCAN_DIR_NESTED) {
       toast.warning(t("library.nestedHint"));
     } else if (res.error) {
       toast.error(res.error);
diff --git a/src/stores/library.spec.ts b/src/stores/library.spec.ts
new file mode 100644
index 000000000..c665b9c8c
--- /dev/null
+++ b/src/stores/library.spec.ts
@@ -0,0 +1,48 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import { createPinia, setActivePinia } from "pinia";
+import { ErrorCode } from "@shared/types/errors";
+
+const mocks = vi.hoisted(() => ({
+  addScanDir: vi.fn(),
+  removeScanDir: vi.fn(),
+}));
+
+beforeEach(() => {
+  setActivePinia(createPinia());
+  vi.clearAllMocks();
+  Object.assign(window, {
+    api: {
+      library: {
+        addScanDir: mocks.addScanDir,
+        removeScanDir: mocks.removeScanDir,
+      },
+    },
+  });
+});
+
+describe("曲库扫描目录", () => {
+  it("添加成功时同步到本地列表且不触发移除", async () => {
+    mocks.addScanDir.mockResolvedValue({ success: true, data: "C:/music" });
+    const { useLibraryStore } = await import("./library");
+    const store = useLibraryStore();
+    const res = await store.addScanDir();
+    expect(res.success).toBe(true);
+    expect(store.scanDirs).toContain("C:/music");
+    expect(mocks.removeScanDir).not.toHaveBeenCalled();
+  });
+
+  it("嵌套目录被主进程拒绝时列表不变且不调用移除", async () => {
+    mocks.addScanDir.mockResolvedValue({
+      success: false,
+      error: ErrorCode.SCAN_DIR_NESTED,
+    });
+    const { useLibraryStore } = await import("./library");
+    const store = useLibraryStore();
+    store.scanDirs = ["C:/music"];
+    const res = await store.addScanDir();
+    expect(res.success).toBe(false);
+    expect(res.error).toBe(ErrorCode.SCAN_DIR_NESTED);
+    expect(store.scanDirs).toEqual(["C:/music"]);
+    expect(mocks.removeScanDir).not.toHaveBeenCalled();
+  });
+});
diff --git a/src/stores/library.ts b/src/stores/library.ts
index a9225935d..b2beffc11 100644
--- a/src/stores/library.ts
+++ b/src/stores/library.ts
@@ -157,20 +157,9 @@ export const useLibraryStore = defineStore("library", () => {
   /** 添加扫描目录 */
   const addScanDir = async (): Promise<{ success: boolean; error?: string }> => {
     const res = await window.api.library.addScanDir();
+    // 嵌套目录由主进程在写入前拒绝，成功才同步到本地列表
     if (res.success) {
-      const newDir = res.data as string;
-      const nested = scanDirs.value.some(
-        (d) =>
-          newDir.startsWith(d + "\\") ||
-          newDir.startsWith(d + "/") ||
-          d.startsWith(newDir + "\\") ||
-          d.startsWith(newDir + "/"),
-      );
-      if (nested) {
-        await window.api.library.removeScanDir(newDir);
-        return { success: false, error: "nested" };
-      }
-      scanDirs.value = [...scanDirs.value, newDir];
+      scanDirs.value = [...scanDirs.value, res.data as string];
     }
     return res;
   };