game-changer

A game-modding toolkit and a shared knowledge base for AI coding agents: Claude Code, Codex, Cursor, Gemini CLI, GitHub Copilot, OpenCode and anything else that reads AGENTS.md. When someone opens an agent in this repo, they almost always want to mod a game, or to learn how a game was modded.

Start here

1. Read skills/mod-any-game/SKILL.md and follow its loop: intake → recon → route → lab (backups) → source of truth → vertical slice → assets → verify in the real game → showcase → publish.
2. Search the knowledge base first: bin/fsgc kb search "<game or engine>". Other agents may already have written down the exact versions, routes and gotchas (knowledge/INDEX.md).
3. At the end, share what you learned: write a field note (bin/fsgc kb new ...) and, once your human agrees, open a PR (bin/fsgc kb pr <note> --yes). See knowledge/README.md and CONTRIBUTING.md.

Tools

• bin/fsgc is the Python CLI, and it sets itself up with uv.
  • Put it on PATH: export PATH="$PWD/bin:$PATH", or install it anywhere with uv tool install git+https://github.com/Fixed-Seed/game-changer.
  • Every group has --help:
    • scan: installed games, engine, anti-cheat, loaders, saves, routes
    • passthrough: two games at once. plan picks the host, each engine's hooks, the link and milestones; peer stands in for either side of the link
    • fixedseed (alias fs): sprites, textures, PBR, 3D, remeshes, rigs, motion, SVG, SFX, music, voice, video via the FixedSeed API (https://run.fixedseed.com, key in FIXEDSEED_KEY)
    • sprite / render3d: art → engine-ready frames
    • win: launch, screenshot, input, record on Windows (also from WSL)
    • video: contact sheets and EDL showcase edits
    • backup: snapshot and restore saves
    • publish: pre-release lint
    • kb: the knowledge base
• FixedSeed MCP server: ships in this repo as bin/fsgc fixedseed mcp (stdio, stdlib only; code in game_changer/fixedseed_mcp.py). It reads FIXEDSEED_KEY from the environment. It also has a passthrough tool and prompt (the same plan as fsgc passthrough plan), which need no key.
  • It's pre-configured per agent: .mcp.json (Claude Code), .codex/config.toml (Codex), .cursor/mcp.json (Cursor), .vscode/mcp.json (VS Code / Copilot), gemini-extension.json (Gemini CLI).
  • No MCP? fsgc fixedseed does the same from the shell.
• Skills (skills/*/SKILL.md, Agent Skills format) are also linked where each agent looks for them: .agents/skills (Codex and others), .claude/skills, .gemini/skills, .github/skills.
• Engine playbooks: skills/mod-any-game/references/engines/.
• Worked examples: examples/terraria-tmodloader, examples/aoe2-de-civ, examples/minecraft-gta5-passthrough.

Rules (full reasoning in skills/mod-any-game/references/safety.md)

• What you can mod: any game the user owns: single-player, multiplayer, or servers the user hosts.
  • Never touch online clients protected by anti-cheat.
  • Never write cheats against other players (aimbots, ESP, speed hacks).
  • Never bypass anti-cheat, DRM or ownership checks.
• Saves: fsgc backup saves before modded launches.
• Spending: price a plan first (fsgc fixedseed estimate, MCP estimate) and tell the user the range; ask before spending more than about $5. Suggest a separate, spend-limited FixedSeed key for the agent.
• What you ship: never commit or publish game files, extracted assets or decompiled code. Keep decompiles outside the repo.
• Processes: kill by exact PID (fsgc win kill), never by name pattern.
• Ask first before:
  • driving the user's mouse and keyboard, and never focus a game with an online mode while they're typing;
  • installing loaders into game folders or changing the registry;
  • publishing anything, PRs included.
• Keep a journal: a MODLOG.md in the mod's working folder. It becomes your field note at the end.

Working on the toolkit itself

• Python: 3.10+, deps Pillow, numpy and PyYAML (uv handles them via bin/fsgc). Code lives in game_changer/, one module per CLI group, each with register(sub) and a docstring that doubles as --help.
• Windows tools: game_changer/ps1/*.ps1 embed C# 5 (Windows PowerShell 5.1's compiler): no string interpolation, no out var, no expression-bodied members.
• Tests: uv run --with pytest pytest -q tests. CI also runs fsgc kb check --index and fsgc publish check ..
• Wording: keep skills and docs agent-neutral ("the agent", not a product name) except in sections about one specific agent.