Turn any single player PC game into coop instantly

A GitHub project called Co-op Anything lets an AI coding agent such as Claude Code, Codex, Gemini CLI, Cursor or OpenCode add co-op multiplayer to single-player PC games by following the repo's AGENTS.md and skills. The project ships a Co-op Anything MCP server that lets agents search a co-op directory, detect a game's engine from its install folder, read the playbook and validate contributions, and it points users to the REA reverse-engineering MCP for binary work. Games listed as in progress or released include Deus Ex (released), Fallout: New Vegas, Zelda: Ocarina of Time (fully synced), Dungeon Keeper and S.T.A.L.K.E.R. Shadow of Chernobyl.

Any single-player game. Your friends. Your agent does the work. Quick start quick-start · How it works how-it-works · What you can co-op what-you-can-co-op · Games so far games-so-far · Contribute everyone-is-a-contributor · FAQ faq · Docs documentation Want to play a single-player game with your friends? Point your AI coding agent at this repo. It researches what exists, reverse engineers the game and its engine if it has to, builds or fixes the co-op, tests it with bots inside the game , and packages it so your friends install it in one click and join over Steam without port forwarding. The sky is the limit. Every game that runs on your PC is a candidate. Games being made co-op right now: Deus Ex https://github.com/cranebeaker/deus-ex-coop released · Fallout: New Vegas https://github.com/cranebeaker/fnv-coop · Zelda: Ocarina of Time https://github.com/cranebeaker/ocarina-coop fully synced · Dungeon Keeper https://github.com/cranebeaker/dungeon-keeper-coop · S.T.A.L.K.E.R. Shadow of Chernobyl https://github.com/cranebeaker/stalker-soc-coop-fixes From the community: Mega Man X https://github.com/mstan/MegaManXSNESRecomp and Mega Man X4 https://github.com/mstan/MegaManX4Recomp native PC with co-op netplay · Pilotwings 64 https://github.com/NoahVl/Birdman64 split-screen · Crab Champions https://github.com/Dudiebug/CrabMods/blob/main/crabsync/README.md · Stacklands https://github.com/Dudiebug/stacklands-coop · Half Sword https://github.com/Dudiebug/halfsword-multiplayer-mod · Enter the Gungeon https://thunderstore.io/c/enter-the-gungeon/p/GoTeamAlex/Gungeon Online/ · Clive Barker's Jericho https://github.com/dolbaras/jericho-coop · Poppy Playtime https://github.com/romannazarov057-spec/PoppyCoop · Divinity II https://github.com/cranebeaker/coop-anything/blob/main/games/divinity-2-developers-cut split-screen · Command & Conquer 3 https://github.com/cranebeaker/coop-anything/blob/main/games/command-and-conquer-3 campaign co-op · Far Cry 2 https://github.com/MortyRei/fc2-coop-probe · Gothic 3 https://github.com/GGM1k3y23/g3-together · Fear & Hunger https://github.com/glynn568-glitch/fear-and-hunger-together · yours next? 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 https://github.com/cranebeaker/coop-anything/blob/main/AGENTS.md and the skills in .agents/skills https://github.com/cranebeaker/coop-anything/blob/main/.agents/skills also in .claude/skills for Claude Code . 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 https://github.com/cranebeaker/coop-anything/blob/main/playbook/mcp.md . For the binary work, pair it with a reverse-engineering MCP such as REA https://github.com/morluto/rea npx rea-agents setup : Co-op Anything knows what to do, REA looks inside the game. Your agent takes one of two paths. | | Path 1: finish what exists | Path 2: build it from zero | |---|---|---| | When | A co-op mod exists but is buggy, stalled or abandoned. Most loved games are here. | Nothing usable exists. | | How | Find the last build, mine its bug reports issues, forums, Discord , audit the code, fix it as a separate package, test, ship. | Reverse engineer the game and engine, hook in, show the second player, sync enemies, world and story, handle level changes and saves, test, ship. | | Skills | coop-research , coop-revive , coop-qa | coop-reverse-engineer , coop-build-from-zero , coop-networking , coop-sync-testing , coop-qa | | Guide | Reviving abandoned mods https://github.com/cranebeaker/coop-anything/blob/main/playbook/reviving-abandoned-mods.md | How co-op mods work https://github.com/cranebeaker/coop-anything/blob/main/playbook/how-coop-mods-work.md | Both paths end the same way: automated tests with real game clients QA https://github.com/cranebeaker/coop-anything/blob/main/playbook/automated-qa.md , easy install, Steam relay networking networking https://github.com/cranebeaker/coop-anything/blob/main/playbook/networking.md , and a pull request back here. Ready-made, game-agnostic tools for building and testing co-op sync, in tools/ https://github.com/cranebeaker/coop-anything/blob/main/tools/README.md . Each has tests, mutation twins and one command that prints ALL OK python -I tools/test all.py runs them all . | Tool | What it does | |---|---| | chaos https://github.com/cranebeaker/coop-anything/blob/main/tools/chaos | UDP relay that adds lag, loss, reorder, duplicates and one-way cuts between real clients, with live control | | flight https://github.com/cranebeaker/coop-anything/blob/main/tools/flight | Flight recorder for your mod plus an analyzer: lines up 2 to 4 machines, finds the first desync, shrinks it and writes a regression test | | fuzz https://github.com/cranebeaker/coop-anything/blob/main/tools/fuzz | Seeded N-player co-op fuzzer with invariant oracles converge, no double apply, one owner, no dupes, nothing stale | | ownership https://github.com/cranebeaker/coop-anything/blob/main/tools/ownership | Small C++ library: one owner per NPC with epochs, handoff, and stale echo rejection | | fakeworld https://github.com/cranebeaker/coop-anything/blob/main/tools/fakeworld | Example in-memory game world for testing sync without launching the game | | gameslot https://github.com/cranebeaker/coop-anything/blob/main/tools/gameslot , gamepool https://github.com/cranebeaker/coop-anything/blob/main/tools/gamepool | Lock and warm pool for running several game copies on one PC safely | | scenarios https://github.com/cranebeaker/coop-anything/blob/main/tools/scenarios , bots https://github.com/cranebeaker/coop-anything/blob/main/tools/bots | JSON start states plus multi-bot co-op playbooks with a state diff after each step | | animcheck https://github.com/cranebeaker/coop-anything/blob/main/tools/animcheck | Compares animation and pose across machines and flags sliding, T-poses, floating and rubber-banding | They come from the fnv-coop https://github.com/cranebeaker/fnv-coop project. The coop-sync-testing skill tells your agent when to use which. | Your game is... | Typical approach | Tools your agent uses | |---|---|---| | On an engine with multiplayer already Unreal 1/2, Source, id Tech, X-Ray | Make the single-player logic run on the existing netcode with script mods | Script source, SDK compilers, mod packages | | Bethesda Gamebryo, Creation | Script extender plugin, host-authority sync, reuse Tilted Online style designs | SKSE / F4SE / xNVSE, Ghidra, REA | | Unity | Harmony patches through a mod loader, a networking library in C | BepInEx, MelonLoader, dnSpyEx, Il2CppDumper | | Unreal Engine 4/5 | Lua or C++ mods with an SDK dump of the game's classes | UE4SS, Dumper-7 | | RE Engine, FromSoftware, other proprietary | DLL hooks; extend the game's own online features where they exist | REFramework, MinHook, Ghidra, REA, x64dbg | | Decompiled or open source N64 decomps, KeeperFX, OpenMW, source ports | Add networking directly in the code | A compiler, the decomp, Docker cross builds | | Console only PS1, PS2, N64, Dreamcast, GameCube, Wii, GBA, ... | Decomp or recompiled PC port first; else emulator netplay, or a memory-sync mod between two emulators | Decomps and recompilers N64Recomp, XenonRecomp , PCSX2 PINE, Dolphin Memory Engine, BizHawk / mGBA Lua | | Closed binary, nothing else | Full reverse engineering of state, saves and levels; the hardest path | REA, GhidraMCP, ida-pro-mcp, Frida, Cheat Engine | Console games: emulator co-op https://github.com/cranebeaker/coop-anything/blob/main/playbook/console-emulators.md and decompiled or recompiled PC ports https://github.com/cranebeaker/coop-anything/blob/main/playbook/decomp-and-recomp.md , the route Ocarina of Time co-op took. Couch co-op on one PC? Split screen https://github.com/cranebeaker/coop-anything/blob/main/playbook/split-screen.md builds on Nucleus Co-op Windows and PartyDeck Linux and Steam Deck , both open source. Full tool list with install notes: playbook/tools.md https://github.com/cranebeaker/coop-anything/blob/main/playbook/tools.md . Which engine has co-op work you can reuse: playbook/engine-families.md https://github.com/cranebeaker/coop-anything/blob/main/playbook/engine-families.md . | Game | What was done | Release | Write-up | |---|---|---|---| | Deus Ex 2000 | Revived the HX co-op mod: fix package, Steam relay, automated test suite | deus-ex-coop https://github.com/cranebeaker/deus-ex-coop | games/deus-ex https://github.com/cranebeaker/coop-anything/blob/main/games/deus-ex/README.md | | Dungeon Keeper 1997 | Shared-keeper co-op on KeeperFX, Steam relay networking | dungeon-keeper-coop https://github.com/cranebeaker/dungeon-keeper-coop | games/dungeon-keeper https://github.com/cranebeaker/coop-anything/blob/main/games/dungeon-keeper/README.md | | S.T.A.L.K.E.R. Shadow of Chernobyl | Fix patch for Shadow of COOP true ending unlocked | stalker-soc-coop-fixes https://github.com/cranebeaker/stalker-soc-coop-fixes | games/stalker https://github.com/cranebeaker/coop-anything/blob/main/games/stalker/README.md | | Fallout: New Vegas | Story co-op: shared quests, dialogue results, karma and reputation | fnv-coop https://github.com/cranebeaker/fnv-coop | games/fallout-new-vegas https://github.com/cranebeaker/coop-anything/blob/main/games/fallout-new-vegas/README.md | | Zelda: Ocarina of Time | Fixes for a fully synced Ship of Harkinian co-op fork | ocarina-coop https://github.com/cranebeaker/ocarina-coop | games/ocarina-of-time https://github.com/cranebeaker/coop-anything/blob/main/games/ocarina-of-time/README.md | Plus a directory of 230+ co-op mods and gaps https://github.com/cranebeaker/coop-anything/blob/main/DIRECTORY.md for other games, each with what it really syncs and how well it was tested. 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 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 https://github.com/cranebeaker/coop-anything/blob/main/CONTRIBUTING.md has the details. Chat with other contributors on Discord https://discord.gg/EXGB49R82t . Do I need to know how to code? No. You need the game, a coding agent and some patience. The agent asks before installing anything or using your accounts. Does my friend need to buy anything? Everyone needs the game installed. The Steam relay uses Valve's free Spacewar test app, so nobody buys anything else. Is this legal? Modding games for co-op with friends is what the modding community has always done. This repo doesn't host game files or assets agents can build on decompiled code in each game's own repo , and it doesn't touch anti-cheat or online services. See the rules below. Will it work for my game? Yes. Some games need more agent hours than others, but it's definitely possible. Check the directory https://github.com/cranebeaker/coop-anything/blob/main/DIRECTORY.md first: if a co-op mod already exists path 1 , most projects take days at most. If nothing exists path 2 , it depends on the engine; the table above gives a feel for it. - AGENTS.md https://github.com/cranebeaker/coop-anything/blob/main/AGENTS.md : rules and phase map for agents · MCP server https://github.com/cranebeaker/coop-anything/blob/main/playbook/mcp.md · skills https://github.com/cranebeaker/coop-anything/blob/main/.agents/skills · sync test tools https://github.com/cranebeaker/coop-anything/blob/main/tools/README.md - Playbook: triage https://github.com/cranebeaker/coop-anything/blob/main/playbook/triage.md · research https://github.com/cranebeaker/coop-anything/blob/main/playbook/research.md · Discord bug mining https://github.com/cranebeaker/coop-anything/blob/main/playbook/discord-export.md · reverse engineering https://github.com/cranebeaker/coop-anything/blob/main/playbook/reverse-engineering.md · tools https://github.com/cranebeaker/coop-anything/blob/main/playbook/tools.md · how co-op mods work https://github.com/cranebeaker/coop-anything/blob/main/playbook/how-coop-mods-work.md · engine families https://github.com/cranebeaker/coop-anything/blob/main/playbook/engine-families.md · reviving mods https://github.com/cranebeaker/coop-anything/blob/main/playbook/reviving-abandoned-mods.md · networking https://github.com/cranebeaker/coop-anything/blob/main/playbook/networking.md · Steam Spacewar relay https://github.com/cranebeaker/coop-anything/blob/main/playbook/networking-steam-spacewar.md · split screen https://github.com/cranebeaker/coop-anything/blob/main/playbook/split-screen.md · console emulators https://github.com/cranebeaker/coop-anything/blob/main/playbook/console-emulators.md · Switch https://github.com/cranebeaker/coop-anything/blob/main/playbook/switch.md · decomp and recomp https://github.com/cranebeaker/coop-anything/blob/main/playbook/decomp-and-recomp.md · automated QA https://github.com/cranebeaker/coop-anything/blob/main/playbook/automated-qa.md · multi-agent workflows https://github.com/cranebeaker/coop-anything/blob/main/playbook/multi-agent-workflows.md · network chaos https://github.com/cranebeaker/coop-anything/blob/main/playbook/network-chaos-testing.md · desync hunting https://github.com/cranebeaker/coop-anything/blob/main/playbook/desync-hunting.md · fuzzing sync https://github.com/cranebeaker/coop-anything/blob/main/playbook/fuzzing-coop-sync.md · actor ownership https://github.com/cranebeaker/coop-anything/blob/main/playbook/actor-ownership.md · fake world testing https://github.com/cranebeaker/coop-anything/blob/main/playbook/fake-world-testing.md · several game copies https://github.com/cranebeaker/coop-anything/blob/main/playbook/multi-instance-testing.md · bots and playbooks https://github.com/cranebeaker/coop-anything/blob/main/playbook/bots-and-playbooks.md · animation sync https://github.com/cranebeaker/coop-anything/blob/main/playbook/animation-sync-checks.md · story sync by effects https://github.com/cranebeaker/coop-anything/blob/main/playbook/effect-capture-story-sync.md · methods https://github.com/cranebeaker/coop-anything/blob/main/playbook/methods.md · lessons https://github.com/cranebeaker/coop-anything/blob/main/playbook/lessons.md - DIRECTORY.md https://github.com/cranebeaker/coop-anything/blob/main/DIRECTORY.md and its schema https://github.com/cranebeaker/coop-anything/blob/main/data/SCHEMA.md 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.