Geargrafx MCP Server

Geargrafx

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Geargrafx is a very accurate, cross-platform TurboGrafx-16 / PC Engine / SuperGrafx / CD-ROM² / LD-ROM² emulator written in C++ that runs on Windows, macOS, Linux, BSD and RetroArch, with an embedded MCP server for AI debugging and development.

This is an open source project with its ongoing development made possible thanks to the support by these awesome backers. If you find it useful, please consider sponsoring.

Don't hesitate to report bugs or ask for new features by opening an issue.

Downloads

Notes:

• Windows: May need Visual C++ Redistributable and OpenGL Compatibility Pack
• Homebrew: If Homebrew asks you to trust the third-party tap, run brew trust --tap drhelius/geardome
• Linux: May need libsdl3

Features

• Accurate emulation supporting the entire HuCard PCE / SGX catalog.
• Support for CD-ROM², Super CD-ROM² and Arcade CD-ROM² systems.
• NEC LaserActive LD-ROM² support through MMI images.
• Save states with preview and rewind support.
• Run-ahead support to reduce input latency.
• Backup RAM and Memory Base 128 support.
• Cheat support for AAAAAA:VV codes, with RetroArch .cht import.
• TurboLink multiplayer for two emulator instances on the same machine.
• Multi Tap (up to 5 players).
• Standard Gamepad (2 buttons), Avenue Pad 3 (3 buttons, auto-configured based on game), Avenue Pad 6 (6 buttons) and Mouse.
• Adjustable scanline count (224p, 240p or manual).
• RGB or Composite color output with optional LPF filter.
• Compressed ROM and CD image support (pce, sgx, cue, zip, chd and mmi).
• Support for playing physical CD-ROM discs.
• Music ROM support: HES.
• VGM recorder.
• Internal database for automatic ROM detection and hardware selection if Auto options are selected.
• Supported platforms (standalone): Windows, Linux, BSD and macOS.
• Supported platforms (libretro): Windows, Linux, macOS, Raspberry Pi, Android, iOS, tvOS, webOS, PlayStation Vita, PlayStation 3, Nintendo 3DS, Nintendo GameCube, Nintendo Wii, Nintendo WiiU, Nintendo Switch, Emscripten, Classic Mini systems (NES, SNES, C64, ...), OpenDingux, RetroFW and QNX.
• Full debugger with just-in-time disassembler, CPU breakpoints, memory access breakpoints, code navigation (goto address, JP JR and JSR double clicking), debug symbols, automatic labels, memory editor, PSG inspector and video viewer including registers, tiles, sprites, backgrounds, CD-ROM sub-systems and both VDCs in SuperGrafx mode.
• MCP server for AI-assisted debugging with Claude Code, Codex and similar, exposing tools for execution control, memory inspection, hardware status, rewind and more.
• Windows, Linux and macOS Portable Mode.
• Programmable Shader Chain.
• ROM loading from the command line by adding the ROM path as an argument.
• ROM loading using drag & drop.
• Support for modern game controllers through gamecontrollerdb.txt file located in the same directory as the application binary.

Tips

Basic Usage

• BIOS: Geargrafx requires a BIOS to run CD-ROM games. It is possible to load any BIOS but the System Card 3.0 with md5 38179df8f4ac870017db21ebcbf53114 is recommended.
• CD-ROM Images: Geargrafx supports chd, zipped and unzipped cue/bin, cue/img and cue/iso images. CUE audio tracks can use raw BIN, compatible WAV (44100 Hz, 16-bit, stereo) or Ogg Vorbis (44100 Hz, stereo) files. MP3 audio tracks are not supported.
• LaserActive Images: Geargrafx supports NEC LD-ROM² .mmi images. A Japanese PAC-N1/PCE-LP1 or US PAC-N10 BIOS is required. Change disc sides through Geargrafx → MMI Media or libretro disk controls. Desktop rewind and run-ahead are disabled for LaserActive.
• Mouse Cursor: Automatically hides when hovering over the main output window or when Main Menu is disabled.
• Portable Mode: Run with --portable, or create an empty file named portable.ini in the same directory as the application binary. On macOS, place the file next to the .app bundle.
• Cheats: Open Emulator → Cheats... to enter codes or import a RetroArch .cht file. Codes use the AAAAAA:VV format with a physical address, for example 1F0DB1:09 writes $09 to work RAM $0DB1. Join several codes with +.

Debugging Features

• Docking Windows: In debug mode, you can dock windows together by pressing SHIFT and dragging a window onto another.
• Multi-viewport: In Windows or macOS, you can enable "multi-viewport" in the debug menu. You must restart the emulator for the change to take effect. Once enabled, you can drag debugger windows outside the main window.
• Single Instance: You can enable "Single Instance" in the Emulator menu. When enabled, opening a ROM while another instance is running will send the ROM to the running instance instead of starting a new one.
• Debug Symbols: The emulator automatically tries to load a symbol file when loading a ROM (.sym, .lbl, .noi). For example, for path_to_rom_file.rom it tries to load path_to_rom_file.sym. You can also load symbol files using the GUI or the CLI. It supports PCEAS (old and new format), wla-dx and vasm file formats.

Command Line Usage

geargrafx [options] [game_file] [symbol_file]
Arguments:  [game_file]                 Accepts ROMs (.pce, .sgx, .hes), CUE (.cue), CHD (.chd), MMI (.mmi) or ZIP (.zip)  [symbol_file]               Optional symbol file for debugging
Options:    -f, --fullscreen          Start in fullscreen mode    -w, --windowed            Start in windowed mode with menu visible      --load-state SLOT       Load save state slot 1-5, or a state file, once the media is loaded      --mcp-stdio             Auto-start MCP server with stdio transport      --mcp-http              Auto-start MCP server with HTTP transport      --mcp-router            Enable compact MCP tool routing      --mcp-http-address A    HTTP bind address (default: 127.0.0.1)      --mcp-http-port N       HTTP port for MCP server (default: 7777)      --turbolink-join N      Join local TurboLink shared session 1-255      --headless              Run without GUI (requires MCP or TurboLink)      --portable              Store configuration and user data beside the application    -v, --version             Display version information    -h, --help                Display this help message

MCP Server

Geargrafx includes a Model Context Protocol (MCP) server that enables AI-assisted debugging through AI agents like Claude Code, Codex and similar. The server provides tools for execution control, memory inspection, breakpoints, disassembly, hardware status, rewind and more. STDIO and HTTP transports are supported, with STDIO preferred.

For complete setup instructions and tool documentation, see MCP_README.md.

TurboLink Multiplayer

Choose the same session number in the TurboLink menu on both instances and select Connect, or start each process with --turbolink-join N. Sessions use local shared memory and support exactly two peers on one computer. Independent instances should use separate application copies or --portable data directories so configuration, saves, and single-instance handling do not conflict.

Agent Skills

Geargrafx provides Agent Skills that teach AI assistants how to effectively use the emulator for specific tasks:

• geargrafx-debugging — Game debugging, code tracing, breakpoint management, hardware inspection, and reverse engineering.
• geargrafx-romhacking — Cheat creation, memory searching, ROM data modification, text translation, and game patching.

Install with npx skills add drhelius/geargrafx. See the skills README for details.

Build Instructions

Windows

• Install Microsoft Visual Studio Community 2026 or later.
• Download the latest SDL3 VC development libraries from SDL3 Releases (the file named SDL3-devel-x.y.z-VC.zip).
• Extract the archive and rename the resulting folder (e.g. SDL3-x.y.z) to SDL3.
• Place the SDL3 folder inside platforms/windows/dependencies/ so that the include path is platforms/windows/dependencies/SDL3/include/SDL3/.
• Open the Geargrafx Visual Studio solution platforms/windows/Geargrafx.sln and build.

macOS

• Install Xcode and run xcode-select --install in the terminal for the compiler to be available on the command line.
• Run these commands to generate a Mac app bundle:

brew install sdl3cd platforms/macosmake dist

Linux

• Ubuntu / Debian / Raspberry Pi (Raspbian):

If you are using Ubuntu 26.04, you can install SDL3 directly. Use the following commands to build:

sudo apt install build-essential pkg-config libsdl3-dev libgl-devcd platforms/linuxmake

For Ubuntu 24.04, you need to build SDL3 from source first. Use the following commands to build both SDL3 and Geargrafx:

sudo apt install build-essential cmake git curl jq pkg-config \  libx11-dev libxext-dev libxrandr-dev libxcursor-dev libxfixes-dev \  libxi-dev libxss-dev libxkbcommon-dev libwayland-dev libdecor-0-dev \  libdrm-dev libgbm-dev libgl1-mesa-dev libegl1-mesa-dev libdbus-1-dev libudev-dev libxtst-devSDL3_TAG=$(curl -s https://api.github.com/repos/libsdl-org/SDL/releases/latest | jq -r '.tag_name')git clone --depth 1 --branch "$SDL3_TAG" https://github.com/libsdl-org/SDL.git /tmp/SDL3cmake -S /tmp/SDL3 -B /tmp/SDL3/build -DCMAKE_INSTALL_PREFIX=/usr -DSDL_TESTS=OFF -DSDL_EXAMPLES=OFFcmake --build /tmp/SDL3/build -j$(nproc)sudo cmake --install /tmp/SDL3/buildcd platforms/linuxmake

• Fedora:

sudo dnf install @development-tools gcc-c++ SDL3-develcd platforms/linuxmake

• Arch Linux:

sudo pacman -S base-devel sdl3cd platforms/linuxmake

BSD

• FreeBSD:

su root -c "pkg install -y git gmake pkgconf sdl3"cd platforms/bsdUSE_CLANG=1 gmake

• NetBSD:

su root -c "pkgin install gmake pkgconf SDL3"cd platforms/bsdgmake

• OpenBSD

doas pkg_add gmake sdl3cd platforms/bsdLDFLAGS=-L/usr/X11R6/lib/ USE_CLANG=1 gmake

Libretro

• Ubuntu / Debian / Raspberry Pi (Raspbian):

sudo apt install build-essentialcd platforms/libretromake

• Fedora:

sudo dnf install @development-tools gcc-c++cd platforms/libretromake

Contributors

Thank you to all the people who have already contributed to Geargrafx!

[Contributors]

License

Geargrafx is licensed under the GNU General Public License v3.0 License, see LICENSE for more information.