diff --git a/assets/test-setup.ts b/assets/test-setup.ts
new file mode 100644
index 00000000..b36c17f4
--- /dev/null
+++ b/assets/test-setup.ts
@@ -0,0 +1,15 @@
+// Node v25+ ships a built-in localStorage that lacks the Web Storage API
+// (getItem/setItem/removeItem). Replace it with a spec-compliant shim so
+// libraries like @vue/devtools-kit work correctly in tests.
+const store = new Map<string, string>();
+
+globalThis.localStorage = {
+  getItem: (key: string) => store.get(key) ?? null,
+  setItem: (key: string, value: string) => store.set(key, String(value)),
+  removeItem: (key: string) => store.delete(key),
+  clear: () => store.clear(),
+  get length() {
+    return store.size;
+  },
+  key: (index: number) => [...store.keys()][index] ?? null,
+} as Storage;
diff --git a/vite.config.ts b/vite.config.ts
index a7d176f8..4212d287 100644
--- a/vite.config.ts
+++ b/vite.config.ts
@@ -89,5 +89,6 @@ export default defineConfig(() => ({
   ],
   test: {
     include: ["assets/**/*.spec.ts"],
+    setupFiles: ["./assets/test-setup.ts"],
   },
 }));