SIGX601 · No root component to hydrate#

Dev message

[ssrClientPlugin] No root component found on app. Make sure you created the app with defineApp(<Component />).

What happened#

app.hydrate(container) found its container, but the app has no root component to hydrate into it.

defineApp() records the element it is given as the app's root. Hydration walks that root against the server's DOM, node for node. An app created without one has nothing to walk — there is no tree to reconcile against the markup — so the plugin throws rather than leaving a page of inert HTML.

In practice this means defineApp() was called with nothing:

TSX 
const app = defineApp();                      // no root
app.use(ssrClientPlugin).hydrate!('#app');    // SIGX601

Fix it#

Pass the root element to defineApp():

TSX 
import { defineApp } from 'sigx';
import { ssrClientPlugin } from '@sigx/server-renderer/client';
import { App } from './App';

const app = defineApp(<App />);
app.use(ssrClientPlugin).hydrate!('#app');

The client's root must be the same component the server rendered. If the server entry renders <App /> and the client hydrates <Root />, hydration mismatches even when this error doesn't fire — keep both entries importing the same root.