Realtime example on local Next.js app not working

import { actor, setup } from "rivetkit";
import * as Y from "yjs";
import { applyUpdate, encodeStateAsUpdate } from "yjs";

export const yjsDocument = actor({
  // Persistent state that survives restarts.
  state: {
    docData: new Uint8Array(), // Raw Yjs document snapshot
    lastModified: 0,
  },

  createVars: () => ({
    doc: new Y.Doc(),
  }),

  onStart: (c) => {
    if (c.state.docData.length > 0) {
      applyUpdate(c.vars.doc, c.state.docData);
    }
  },

  // Handle client connections.
  onConnect: (c, conn) => {
    const update = encodeStateAsUpdate(c.vars.doc);
    conn.send("initialState", { update });
  },

  actions: {
    // Callable functions from clients.
    applyUpdate: (c, update: Uint8Array) => {
      applyUpdate(c.vars.doc, update);

      const fullState = encodeStateAsUpdate(
        c.vars.doc,
      ) as Uint8Array<ArrayBuffer>;
      // State changes are automatically persisted
      c.state.docData = fullState;
      c.state.lastModified = Date.now();

      // Send events to all connected clients.
      c.broadcast("update", { update });
    },

    getState: (c) => ({
      docData: c.state.docData,
      lastModified: c.state.lastModified,
    }),
  },
});

// Register actors for use.
export const registry = setup({
  use: { yjsDocument },
});