fix: avoid scene initialization after Strict Mode cleanup

src/__tests__/useUnicornScene.test.ts

@@ -1,5 +1,6 @@
 import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
 import { renderHook, act } from "@testing-library/react";
+import { StrictMode } from "react";
 import { useUnicornScene } from "../shared/hooks";
 import type { UnicornStudioScene } from "../shared/types";
 import { MockResizeObserver } from "./setup";
@@ -85,6 +86,20 @@ describe("useUnicornScene", () => {
     expect(result.current.error).toBeNull();
   });
 
+  it("initializes once in Strict Mode", async () => {
+    const scene = createMockScene();
+    addSceneMock.mockResolvedValue(scene);
+
+    renderHook(() => useUnicornScene(defaultProps(elementRef)), {
+      wrapper: StrictMode,
+    });
+
+    await act(async () => {});
+
+    expect(addSceneMock).toHaveBeenCalledTimes(1);
+    expect(scene.destroy).not.toHaveBeenCalled();
+  });
+
   it("does not initialize when isScriptLoaded is false", async () => {
     const { result } = renderHook(() =>
       useUnicornScene({ ...defaultProps(elementRef), isScriptLoaded: false }),
@@ -487,6 +502,8 @@ describe("useUnicornScene", () => {
       },
     });
 
+    await act(async () => {});
+
     // Props change while addScene() is still in flight, so the scene config was
     // already built with the previous values.
     rerender({

src/shared/hooks.ts

@@ -409,6 +409,10 @@ export function useUnicornScene({
     async function initializeScene() {
       if (!elementRef.current || !isScriptLoaded || validationError) return;
 
+      // Let Strict Mode clean up its discarded effect before starting the SDK.
+      await Promise.resolve();
+      if (ignore) return;
+
       // Prevent multiple concurrent initializations
       if (isInitializingRef.current) return;