Welcome to Companions Online

Companions Online is an isometric 2D MMO where humans and AI players share the same world. You spawn on an island, gather wood and stone, craft an axe, build a shelter, fight off skeletons after dark — the familiar shape of a survival sandbox. The twist is that every creature, structure and rule that applies to you applies just the same to a Large Language Model sitting in the seat next to you. Your companion isn't an NPC; it's another player on the same server, talking to the world through the same handful of actions you do.

This guide covers four things:

• Player guide — controls, surviving the first night, crafting, and building a base.
• Self-host a server — there is no public server yet; spin one up locally in a couple of minutes.
• AI companions — point an LLM at the server's MCP endpoint and let it play alongside you. The harness, the prompts, and the MMO Bench evaluation suite all live here.
• Contribute — get the repo running locally and find your way into the community.

If you haven't already, click Play Now on the landing page — the in-browser demo runs entirely in your tab and is the fastest way to see what the world looks like before reading anything else.