COTL MP Steam

COTL MP Steam adds online two-player co-op to Cult of the Lamb. It runs over Steam peer-to-peer networking, so there is no dedicated server and nothing to port forward: one player hosts on their own save and the other joins from the Steam friends list or a Discord invite.

How it works

The host is authoritative. Their save is loaded, streamed to the guest in memory, and it is the copy that keeps the progress. The guest plays inside that world as the vanilla goat, with their own camera, HUD, health and curses — and their own saves are never written to.

Requirements

• Cult of the Lamb on Steam, the same game version on both machines.
• BepInEx 5.4.21 and COTL_API.
• The same mods on both sides. The handshake compares the protocol version, the MP build and every installed plugin by file hash, and tells you exactly what does not match.
• Discord running, if you want Invite to Play and Ask to Join.

What is synced

Dungeons (room seeds, decoration, enemies, damage, knock-outs and revives), boss fights, base building, follower commands, altar rituals, the cult's inventory, conversations, the adventure map, and CultTweaker skins and content. Rewards are instanced, so both players take their own weapons, curses, relics and tarot cards from a room.

CultTweaker together

If both players run a matching CultTweaker build:

• custom follower and player skins follow all session long, including switching back to a vanilla skin;
• the host's CultTweaker content can be downloaded on join, after a consent prompt, on its own low-priority transfer lane so it does not spike your ping;
• the F4 room editor works over the link — the world freezes for both of you, edits appear live, the other player's selection is drawn in amber, and the host saves the file and ships it across.