diff --git a/webui/src/tests/main-randomuuid.test.tsx b/webui/src/tests/main-randomuuid.test.tsx
new file mode 100644
index 000000000..a7660ac24
--- /dev/null
+++ b/webui/src/tests/main-randomuuid.test.tsx
@@ -0,0 +1,42 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+
+const render = vi.fn();
+const createRoot = vi.fn(() => ({ render }));
+
+vi.mock("react-dom/client", () => ({
+  default: { createRoot },
+}));
+
+vi.mock("@/App", () => ({
+  default: () => null,
+}));
+
+describe("main entry crypto shim", () => {
+  const originalRandomUUID = globalThis.crypto.randomUUID;
+
+  beforeEach(() => {
+    vi.resetModules();
+    createRoot.mockClear();
+    render.mockClear();
+    document.body.innerHTML = '<div id="root"></div>';
+    delete (globalThis.crypto as Crypto & { randomUUID?: Crypto["randomUUID"] }).randomUUID;
+  });
+
+  afterEach(() => {
+    Object.defineProperty(globalThis.crypto, "randomUUID", {
+      value: originalRandomUUID,
+      configurable: true,
+    });
+    document.body.innerHTML = "";
+  });
+
+  it("installs a randomUUID fallback when the browser omits it", async () => {
+    await import("../main");
+
+    expect(globalThis.crypto.randomUUID).toEqual(expect.any(Function));
+    expect(globalThis.crypto.randomUUID()).toMatch(
+      /^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/,
+    );
+    expect(createRoot).toHaveBeenCalledWith(document.getElementById("root"));
+  });
+});