Gearsystem MCP Server

Gearsystem

Gearsystem is a very accurate, cross-platform Sega Master System / Game Gear / SG-1000 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

Platform Architecture Download Link

Windows Desktop x64 Gearsystem-3.9.24-desktop-windows-x64.zip

Desktop ARM64 Gearsystem-3.9.24-desktop-windows-arm64.zip

macOS Homebrew brew install --cask drhelius/geardome/gearsystem

Desktop Apple Silicon Gearsystem-3.9.24-desktop-macos-arm64.zip

Desktop Intel Gearsystem-3.9.24-desktop-macos-intel.zip

Linux Ubuntu PPA drhelius/ppa-geardome

Fedora RPM drhelius/rpm-geardome

Desktop Ubuntu 26.04 x64 Gearsystem-3.9.24-desktop-ubuntu26.04-x64.zip

Desktop Ubuntu 26.04 ARM64 Gearsystem-3.9.24-desktop-ubuntu26.04-arm64.zip

Desktop Ubuntu 24.04 x64 Gearsystem-3.9.24-desktop-ubuntu24.04-x64.zip

Desktop Ubuntu 24.04 ARM64 Gearsystem-3.9.24-desktop-ubuntu24.04-arm64.zip

MCPB All platforms MCP Readme

RetroArch All platforms Libretro core documentation

Dev Builds All platforms GitHub Actions

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

Supported Machines

• Sega Mark III
• Sega Master System
• Sega Game Gear
• Sega Game 1000 (SG-1000)
• Othello Multivision

Features

• Very accurate Z80, VDP, PSG and FM emulation.
• Supported cartridges: ROM, ROM + RAM, SEGA, Codemasters, Korean, MSX + Nemesis, Janggun, SG-1000, and many Korean multi-carts.
• Automatic region detection: NTSC-JAP, NTSC-USA, PAL-EUR.
• Support for YM2413 (OPLL) FM sound chip.
• Gear-to-Gear cable support for two local desktop processes, including serial and parallel communication.
• Mark III Joy-Joy cable support for two local desktop processes.
• Light Phaser and Paddle Control support.
• Internal database for ROM detection.
• Battery powered RAM save support.
• Save states with preview and rewind support.
• Run-ahead support to reduce input latency.
• Compressed ROM support (ZIP).
• *Game Genie* and *Pro Action Replay* cheat support, with RetroArch .cht import.
• VGM recorder.
• 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 CALL double clicking), debug symbols, automatic labels, memory editor, trace logger, IO inspector and VRAM viewer including tiles, sprites, backgrounds and palettes.
• 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: Gearsystem can run with or without a BIOS. You can optionally load a BIOS and enable it. It's possible to run the title included in the BIOS by setting Media Slot to None in the Emulator menu. This emulates a machine without any media plugged in.
• Overscan: For a precise representation of the original image, select Overscan Top+Bottom and Aspect Ratio Standard (4:3 DAR) in the Video menu. Game Gear will ignore any overscan settings.
• 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.
• Gear-to-Gear and Mark III Link Cable:

Open Link Cable in two desktop instances, select the same session, and connect both, or start each process with --link-session N. Select Auto, Gear-to-Gear, or Mark III under Protocol; the session is independent of this selection. Auto uses Gear-to-Gear for native Game Gear software and Mark III Joy-Joy for F-16 Fighting Falcon (Japan). For Mark III, Return, 1, 2, and Space are mapped to the SK-1100 keyboard. Reset the console if Mark III hardware is attached after startup. Independent instances should use separate application copies or --portable data directories so configuration, saves, and single-instance handling do not conflict.

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, .noi). For example, for path_to_rom_file.sms it tries to load path_to_rom_file.sym. You can also load a symbol file using the GUI or the CLI. It supports sjasmplus/Pasmo (EQU), SDCC/NoICE (.noi), wla-dx and vasm/generic file formats.

Command Line Usage

gearsystem [options] [rom_file] [symbol_file]

Arguments: [rom_file] ROM file: accepts ROMs (.sms, .gg, .sg, .mv) 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) --headless Run without GUI (requires MCP or Link Cable) --link-session N Connect to link cable session 1-255 --link-stall-us N Override barrier stall threshold (0=default) --portable Store configuration and user data beside the application -v, --version Display version information -h, --help Display this help message

MCP Server

Gearsystem 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, and more. STDIO and HTTP transports are supported, with STDIO preferred.

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

Agent Skills

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

• [gearsystem-debugging](skills/gearsystem-debugging/SKILL.md) — Game debugging, code tracing, breakpoint management, hardware inspection, and reverse engineering.
• [gearsystem-romhacking](skills/gearsystem-romhacking/SKILL.md) — Cheat creation, memory searching, ROM data modification, text translation, and game patching.

Install with npx skills add drhelius/gearsystem. S