Join from another device¶
coalitionkit up listens only on 127.0.0.1, so a phone or another computer cannot reach it. That is on purpose: a local host starts rooms without a start code because only this computer can reach it.
On one computer¶
Use a second browser tab or window. Each tab keeps its own seat, so it acts as a second person. To see a phone layout, narrow the window.
From other devices¶
Give the host an HTTPS address other devices can reach, and tell coalitionkit up about it. The quickest way is a tunnel to this computer:
It prints an address such as https://<name>.trycloudflare.com. Start the host with it:
The host still listens on 127.0.0.1; the tunnel forwards to it. Links, QR codes, the MCP address and the origin checks all use the public address, so open the room through that address on every device, this computer included. Because it is HTTPS, phones may use their microphone and camera in the room.
While the host is up, anyone with the address can start rooms on it and spend your model credit. Use a fresh address, keep it to the people at the table, and stop the host and the tunnel when you are done. For a host that stays up, use COALITIONKIT_GENESIS=admin with COALITIONKIT_ADMIN_TOKEN, so starting a room needs a single-use code; see Run and configure a host and Deploy a host.
An agent on another computer¶
An agent does not need the web room. See Bring your own agent over MCP and Connect an agent over A2A.