xb-netblocks - SKILL.md Agent Skill

name: xb-netblocks description: >- Add real-time multiplayer to an XR Blocks app with the netblocks addon — presence avatars (remote heads + hands), replicated `NetObject` transforms with cooperative ownership, typed pub/sub RPC events, and opt-in spatial WebRTC voice, over pluggable transports (BroadcastChannel for local dev, WebRTC/PeerJS for serverless P2P, WebSocket relay for scalable rooms). Use when building shared or co-located XR. Covers `enableNet()`, `joinRoom()`, `NetObject`, and `session.events`; the full reference (wire protocol, transports, threat model) is at src/addons/netblocks/.

xb-netblocks: multiplayer XR

A Transport moves bytes between peers; a NetSession layers presence, RPC, replicated objects, and voice on top. Swap transports without changing app code.

Full reference: ../../src/addons/netblocks/SKILL.md and ../../src/addons/netblocks/README.md.

When to use

Cooperative, trusted rooms (demos, classrooms, co-presence). It is prototype-grade — no peer authentication, cooperative ownership, no rate limiting. For adversarial workloads, put a server-authoritative arbiter on top.

Quick start

import * as xb from 'xrblocks';
import {
  enableNet,
  BroadcastChannelTransport,
} from 'xrblocks/addons/netblocks/src/index.js';

class MyApp extends xb.Script {
  async init() {
    const net = enableNet(); // ticks on the standard xb frame loop
    const session = await net.joinRoom('my-room', {
      transport: new BroadcastChannelTransport(), // two tabs see each other instantly
      displayName: 'Alice',
    });
    session.events.on('chat', (text, fromPeerId) =>
      console.log(`${fromPeerId}: ${text}`)
    );
  }
}
xb.add(new MyApp());
xb.init();

Share an object

import {
  NetObject,
  WebRTCTransport,
} from 'xrblocks/addons/netblocks/src/index.js';

const shared = new NetObject({id: 'cube', object: this.cube});
const net = enableNet();
await net.joinRoom('demo', {
  transport: new WebRTCTransport(),
  displayName: 'Alice',
});
net.session?.netObjects.add(shared);
// session.claim(obj) on grab, session.release(obj) on drop; owners broadcast, others interpolate.

Transports

BroadcastChannelTransport — local dev, two tabs, zero infra.
WebRTCTransport — serverless P2P via PeerJS (≤ ~12 peers); pass iceServers/signalingUrl.
WebSocketTransport — a small relay (server/relay.js) for scalable rooms.

Enable voice with joinRoom({voice: true}) or session.voice.enable().