The sky is the limit. Every game that runs on your PC is a candidate.
Games being made co-op right now: Deus Ex (released) · Fallout: New Vegas · Zelda: Ocarina of Time (fully synced) · Dungeon Keeper · S.T.A.L.K.E.R. Shadow of Chernobyl
From the community: Mega Man X and Mega Man X4 (native PC with co-op netplay) · Pilotwings 64 (split-screen) · Crab Champions · Stacklands · Half Sword · Enter the Gungeon · Clive Barker's Jericho · Poppy Playtime · Divinity II (split-screen) · Command & Conquer 3 (campaign co-op) · Far Cry 2 · Gothic 3 · Fear & Hunger · Modern Warfare 2 (campaign co-op) · Little Nightmares (on our Discord) · yours next?
Quick start
Tell your agent (Claude Code, Codex, Gemini CLI, Cursor, OpenCode, ...):
Read https://github.com/cranebeaker/coop-anything and follow AGENTS.md.
I want to play <game> in co-op with my friends.
The agent follows AGENTS.md and the skills in .agents/skills
(also in .claude/skills for Claude Code).
Add the MCP server
The Co-op Anything MCP lets any agent search the co-op directory, detect a game's engine
from its install folder, read the playbook and skills, and validate contributions.
Claude Code picks it up from this repo's .mcp.json; for other agents:
claude mcp add coop-anything -- python <clone>/tools/mcp/coop_mcp.py
Codex, Gemini CLI and Cursor setup: playbook/mcp.md. For the binary work,
pair it with a reverse-engineering MCP such as REA
(npx rea-agents setup): Co-op Anything knows what to do, REA looks inside the game.
How it works
Your agent takes one of two paths.
Both paths end the same way: automated tests with real game clients (QA), easy install, Steam relay networking (networking), and a pull request back here.
Sync test tools
Ready-made, game-agnostic tools for building and testing co-op sync, in tools/.
Each has tests, mutation twins and one command that prints ALL OK
(python -I tools/test_all.py runs them all).
Fast iteration shows where the time in an in-game fix round goes and which tool removes each wait.
They come from the fnv-coop project. The
coop-sync-testing skill tells your agent when to use which.
What you can co-op
Console games: emulator co-op and decompiled or recompiled PC ports, the route Ocarina of Time co-op took.
Couch co-op on one PC? Split screen builds on Nucleus Co-op (Windows) and PartyDeck (Linux and Steam Deck), both open source.
Full tool list with install notes: playbook/tools.md. Which engine has co-op work you can reuse: playbook/engine-families.md.
Games so far
Plus a directory of 230+ co-op mods and gaps for other games (browse and search it at coopanything.app), each with what it really syncs and how well it was tested.
Everyone is a contributor
Every agent that works on a game sends what it learned back as a pull request: a fix, a bug list, a test, a failed attempt, a corrected directory entry. One person's agent gets a game halfway; the next one starts from there. Pooled together, that's enough compute to get even the biggest games over the line.
- Your agent opens the PR as a draft; you review the diff and publish it.
- Each game gets its own release repo, linked from Games so far.
- The QA level on every entry says how it was proven: untested, player reports, automated tests (bots drove real game clients) or verified playthrough.
CONTRIBUTING.md has the details. Chat with other contributors on Discord.
FAQ
Documentation
- AGENTS.md: rules and phase map for agents · MCP server · skills · sync test tools
- Playbook: triage · research · Discord bug mining · reverse engineering · tools · how co-op mods work · engine families · reviving mods · networking · Steam Spacewar relay · split screen · console emulators · Switch · decomp and recomp · automated QA · multi-agent workflows · network chaos · desync hunting · fuzzing sync · actor ownership · fake world testing · several game copies · bots and playbooks · animation sync · fast iteration · in-game bridge · hot reload · story sync by effects · methods · lessons
- DIRECTORY.md and its schema
Rules
Don't commit game files or assets here. Building on decomps is fine; a game's code lives in its own repo. No personal info. Credit the mods you build on and give fixes back to them. Co-op only: nothing that cheats in other people's multiplayer games or touches anti-cheat.
License: MIT.