the prev line createContainer, root.current = new FiberNode(...), the fiber node will be freeze with preventExtensions api , markContainerAsRoot is not effect in here.

[jeryqwq]

react/packages/react-dom/src/client/ReactDOMRoot.js

Line 249 in 6bd53a5

markContainerAsRoot(root.current, container);

the prev line createContainer, root.current = new FiberNode(...), the fiber node will be freeze with preventExtensions api , this line is not effect in here.

  function markContainerAsRoot(hostRoot, node) {
    node[internalContainerInstanceKey] = hostRoot;
  }