> For the complete documentation index, see [llms.txt](https://zumo.fusion.ac/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://zumo.fusion.ac/api-reference/websocket/ws.md).

# Overview

**URL:** `https://zed.fusion.ac`\
**Path:** Engine.IO `/socket.io/` (WebSocket transport)\
**Protocol:** Socket.IO v5 / Engine.IO v4\
**Namespace:** `/` (consumers only in this reference)

## Auth

```js
io('https://zed.fusion.ac', { auth: { key: 'zk_...' } });
```

Optional: `query: { mode: 'duels' }` to filter by envelope mode.

## Message model

Socket.IO **event name** = type string. Subscribe with `socket.on('playerJoined', ...)`.

Emit (consumer → hub): [`replayRequest`](/api-reference/websocket/emit-replay-request.md). Requires **provide** ACL.

## Sections

* [Envelope](/api-reference/websocket/envelope.md)
* [Event index](/api-reference/websocket/event-index.md)
* Lobby / Replay / Zumo-published event pages in the sidebar