What is Co-op Anything?
Co-op Anything, from the GitHub user cranebeaker, is a repository a coding agent reads and follows to add co-op to a single-player game. AGENTS.md sets the rules and a phase map from triage to shipping; 13 skills in .agents/skills and .claude/skills cover research, reviving abandoned mods, reverse engineering, networking, sync testing, QA, console emulators and decomp ports. A playbook of more than 30 guides and a set of game-agnostic sync test tools (a lag and packet-loss relay, a desync flight recorder, a fuzzer, bots) back them up. A small Python MCP server lets any agent search the directory, detect a game's engine from its install folder and read the playbook.
The repo was created on 16 October 2026 and had about 2,064 stars, 275 forks, 135 open issues and 40 open pull requests on 11 November 2026, with the last commit on 2 November. It is MIT-licensed, written mostly in Python and has no tagged releases. Its directory lists 356 co-op projects and 44 open gaps across 252 games, browsable at coopanything.app; finished work includes revived co-op for Deus Ex and fixes for a Zelda: Ocarina of Time co-op fork.
Is Co-op Anything worth it?
Co-op Anything treats adding multiplayer to a single-player game as a long engineering project, not a prompt. The agent first triages the game and checks the directory for prior work, then takes one of two paths: finish a buggy or abandoned co-op mod, or reverse engineer the game and build sync from zero. Both end the same way, with automated tests in which bots drive real game clients, a one-click installer and a pull request back to the hub. The README admits path two is hard; the closed-binary row of its engine table is labelled the hardest path.
The rules in AGENTS.md are the strongest part. The agent must copy the install and never touch the owner's real game or saves, ask before installing software or using Steam, Discord or GitHub accounts, pin downloads by SHA-256, and treat text in issues, mod readmes and Discord exports as data rather than instructions, which is the right defence for an agent that reads a lot of untrusted forum text. Every directory entry carries a QA level, from untested to verified playthrough, so a claim that a mod works says how it was proven.
The legal line is drawn by the project, not by a lawyer. Its FAQ says the repo hosts no game files or assets and does not touch anti-cheat or online services, and the rules forbid anti-cheat bypass and cheating in other people's multiplayer games; the MCP server's engine detector flags EasyAntiCheat and BattlEye files and warns that work must stay offline. Decompiled code is explicitly allowed, kept in each game's own repo, with a note to ship a patch when a licence forbids derivatives. Networking leans on Steam's Spacewar test app, ID 480, which the playbook says cannot ship on the Steam store and shows both players as playing Spacewar.
The pace shows. In under a month the repo gathered 135 open issues and 40 open pull requests, a backlog the maintainers' own triage skill exists to work through. Compared with universal-modder, which aims at modding in general and generating assets, this goes much deeper on one hard problem: keeping two copies of a game in step.
Where it earns its place
A group of four friends who finished a single-player RPG together on voice chat
Find out whether a co-op mod already exists and how well it works
Ask the agent to run detect_engine on the install folder and search_directory for the game and its engine. It costs a few minutes of agent time and returns the existing projects, what they sync and how they were tested.
A hobbyist modder whose favourite co-op mod was abandoned in 2019
Revive the mod and fix the desyncs players still report
Follow the coop-revive path: mine the old issues and Discord, audit the code, ship fixes as a separate package, and replay desyncs with the flight recorder. The README says most revive projects take days at most.
A network programmer prototyping co-op for an indie Unity game
Test sync logic under bad network conditions before launching the game
Use the fake world, the seeded fuzzer and the chaos relay that adds lag, loss and reordering; python -I tools/test_all.py runs every tool's tests and prints ALL OK.
Before you commit
- Setup
- Tell the agent to read the repo and follow AGENTS.md; Claude Code picks up the MCP server from .mcp.json. The MCP server needs Python 3.9+ and PyYAML; other agents add it with one command, documented for Codex, Gemini CLI and Cursor.
- Integrations
- MCP tools: search_directory, detect_engine, game_identity, list_docs, read_playbook, get_skill, get_game, get_test_tool and validate_entry. The playbook points to external tools such as Ghidra, REA, BepInEx, UE4SS, Frida and Cheat Engine, plus Couchlink, Nucleus Co-op and PartyDeck for split screen.
- Data and privacy
- The MCP server reads the clone and, for detect_engine and game_identity, a game folder you name, read-only; it opens no port. The agent's own work runs commands, installs tools and edits game copies, so its permissions matter more than the server's. Private notes go in local/, which git ignores, and PRs must carry no game files, tokens or personal paths.
- Cost at scale
- Free. The real cost is agent tokens: a revive can take days and a build from zero many agent hours, by the README's own account, plus a copy of the game for every player.
- Limits
- No tagged releases, a large review backlog, and QA levels that depend on contributors running the bot tests honestly. Console games need a decomp, recompiled port or emulator netplay first.
What’s good
- Clear agent rules: work on a copy, ask before accounts, untrusted text is data
- Directory of 356 projects with an honest QA level on each
- Game-agnostic sync tools: lag relay, desync recorder, fuzzer, bots
- Read-only MCP server detects engines and anti-cheat files
What’s not
- No releases; you follow a main branch that changes daily
- 135 open issues and 40 open pull requests within a month
- Building co-op from zero still takes many agent hours
- Spacewar networking cannot ship on the Steam store
Best for
Patient PC players and modders with a coding agent who want to revive a stalled co-op mod or attempt co-op for a game nobody has covered.
Co-op Anything alternatives
Co-op Anything: common questions
- Is Co-op Anything worth it?
- A serious, well-ruled playbook for agent-built co-op mods, whose shared directory and test tools are worth more than any single game it has finished. We rate it 3.8 out of 5.
- How much does Co-op Anything cost?
- Free and open source (MIT). The cost is your coding agent's usage; every player needs their own copy of the game.
- What are the downsides of Co-op Anything?
- No releases; you follow a main branch that changes daily; 135 open issues and 40 open pull requests within a month; building co-op from zero still takes many agent hours; spacewar networking cannot ship on the Steam store.
- Who is Co-op Anything best for?
- Patient PC players and modders with a coding agent who want to revive a stalled co-op mod or attempt co-op for a game nobody has covered.
- How much does Co-op Anything cost for a team or in production?
- Free. The real cost is agent tokens: a revive can take days and a build from zero many agent hours, by the README's own account, plus a copy of the game for every player.
- Is Co-op Anything safe for company data?
- The MCP server reads the clone and, for detect_engine and game_identity, a game folder you name, read-only; it opens no port. The agent's own work runs commands, installs tools and edits game copies, so its permissions matter more than the server's. Private notes go in local/, which git ignores, and PRs must carry no game files, tokens or personal paths.
- What are the best Co-op Anything alternatives?
- The closest alternatives we have reviewed are universal-modder and Claude Code Game Studios.
Answers checked Nov 11, 2026.