# Gearlynx
[](https://github.com/drhelius/Gearlynx/actions/workflows/gearlynx.yml)
[](https://github.com/drhelius/Gearlynx/releases)
[](https://github.com/drhelius/Gearlynx/commits/main)
[](https://github.com/drhelius/Gearlynx/graphs/contributors)
[](https://github.com/sponsors/drhelius)
[](https://github.com/drhelius/Gearlynx/blob/main/LICENSE)
[](https://x.com/drhelius)
Gearlynx is a very accurate, cross-platform Atari Lynx 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](backers.md). If you find it useful, please consider [sponsoring](https://github.com/sponsors/drhelius).
Don't hesitate to report bugs or ask for new features by [opening an issue](https://github.com/drhelius/Gearlynx/issues).
<img src="http://www.geardome.com/files/gearlynx/gearlynx_debug_07.png">
## Downloads
<table>
<thead>
<tr>
<th>Platform</th>
<th>Architecture</th>
<th>Download Link</th>
</tr>
</thead>
<tbody>
<tr>
<td rowspan="2"><strong>Windows</strong></td>
<td>Desktop x64</td>
<td><a href="https://github.com/drhelius/Gearlynx/releases/download/1.2.37/Gearlynx-1.2.37-desktop-windows-x64.zip">Gearlynx-1.2.37-desktop-windows-x64.zip</a></td>
</tr>
<tr>
<td>Desktop ARM64</td>
<td><a href="https://github.com/drhelius/Gearlynx/releases/download/1.2.37/Gearlynx-1.2.37-desktop-windows-arm64.zip">Gearlynx-1.2.37-desktop-windows-arm64.zip</a></td>
</tr>
<tr>
<td rowspan="3"><strong>macOS</strong></td>
<td>Homebrew</td>
<td><code>brew install --cask drhelius/geardome/gearlynx</code></td>
</tr>
<tr>
<td>Desktop Apple Silicon</td>
<td><a href="https://github.com/drhelius/Gearlynx/releases/download/1.2.37/Gearlynx-1.2.37-desktop-macos-arm64.zip">Gearlynx-1.2.37-desktop-macos-arm64.zip</a></td>
</tr>
<tr>
<td>Desktop Intel</td>
<td><a href="https://github.com/drhelius/Gearlynx/releases/download/1.2.37/Gearlynx-1.2.37-desktop-macos-intel.zip">Gearlynx-1.2.37-desktop-macos-intel.zip</a></td>
</tr>
<tr>
<td rowspan="6"><strong>Linux</strong></td>
<td>Ubuntu PPA</td>
<td><a href="https://github.com/drhelius/ppa-geardome">drhelius/ppa-geardome</a></td>
</tr>
<tr>
<td>Fedora RPM</td>
<td><a href="https://github.com/drhelius/rpm-geardome">drhelius/rpm-geardome</a></td>
</tr>
<tr>
<td>Desktop Ubuntu 26.04 x64</td>
<td><a href="https://github.com/drhelius/Gearlynx/releases/download/1.2.37/Gearlynx-1.2.37-desktop-ubuntu26.04-x64.zip">Gearlynx-1.2.37-desktop-ubuntu26.04-x64.zip</a></td>
</tr>
<tr>
<td>Desktop Ubuntu 26.04 ARM64</td>
<td><a href="https://github.com/drhelius/Gearlynx/releases/download/1.2.37/Gearlynx-1.2.37-desktop-ubuntu26.04-arm64.zip">Gearlynx-1.2.37-desktop-ubuntu26.04-arm64.zip</a></td>
</tr>
<tr>
<td>Desktop Ubuntu 24.04 x64</td>
<td><a href="https://github.com/drhelius/Gearlynx/releases/download/1.2.37/Gearlynx-1.2.37-desktop-ubuntu24.04-x64.zip">Gearlynx-1.2.37-desktop-ubuntu24.04-x64.zip</a></td>
</tr>
<tr>
<td>Desktop Ubuntu 24.04 ARM64</td>
<td><a href="https://github.com/drhelius/Gearlynx/releases/download/1.2.37/Gearlynx-1.2.37-desktop-ubuntu24.04-arm64.zip">Gearlynx-1.2.37-desktop-ubuntu24.04-arm64.zip</a></td>
</tr>
<tr>
<td><strong>MCPB</strong></td>
<td>All platforms</td>
<td><a href="MCP_README.md">MCP Readme</a></td>
</tr>
<tr>
<td><strong>RetroArch</strong></td>
<td>All platforms</td>
<td><a href="https://docs.libretro.com/library/gearlynx/">Libretro core documentation</a></td>
</tr>
<tr>
<td><strong>Dev Builds</strong></td>
<td>All platforms</td>
<td><a href="https://github.com/drhelius/Gearlynx/actions/workflows/gearlynx.yml">GitHub Actions</a></td>
</tr>
</tbody>
</table>
**Notes:**
- **Windows**: May need [Visual C++ Redistributable](https://go.microsoft.com/fwlink/?LinkId=746572) and [OpenGL Compatibility Pack](https://apps.microsoft.com/detail/9nqpsl29bfff)
- **Homebrew**: If Homebrew asks you to trust the third-party tap, run `brew trust --tap drhelius/geardome`
- **Linux**: May need `libsdl3`
## Features
- Very accurate emulation supporting the entire commercial Atari Lynx catalog and most homebrew and demos.
- User selectable Lynx I or Lynx II emulation.
- Compressed and homebrew ROM support (lnx, lyx, o, bin, and zip).
- Save states with preview and rewind support.
- Run-ahead support to reduce input latency.
- Very accurate audio emulation with configurable low-pass filter (mimics original Lynx audio hardware).
- ComLynx multiplayer for up to eight emulator instances on the same machine.
- VGM recorder.
- Internal database for automatic ROM detection and hardware selection if `Auto` options are selected.
- Bank switching (BANK1 + AUDIN) and EEPROM.
- Save files (EEPROM and NVRAM).
- Cheat support for `AAAA:VV` codes.
- GameDrive and ElCheapoSD cartridge APIs.
- 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 run-ahead disassembler that can handle self-modifying code, CPU and memory breakpoints, code navigation (goto address, JP JR and JSR double clicking), debug symbols, automatic labels, memory editor, memory search, Suzy and Mikey register viewer, audio channels, UART, cartridge and video inspector.
- 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](platforms/shared/desktop/shaders/README.md).
- 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](https://github.com/mdqinc/SDL_GameControllerDB) file located in the same directory as the application binary.
## Tips
### Basic Usage
- **BIOS**: Gearlynx requires a BIOS to work. It is possible to load any BIOS but the original with md5 `fcd403db69f54290b51035d82f835e7b` is recommended.
- **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 `AAAA:VV` format with a RAM address, for example `0050:05` writes `$05` to RAM `$0050`. 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. For example, for `path_to_rom_file.rom` it tries to load `path_to_rom_file.sym`, `path_to_rom_file.elf`, the loaded-file sidecar `path_to_rom_file.rom.elf`, `path_to_rom_file.lbl` and `path_to_rom_file.noi`. You can also load symbol files using the GUI or the CLI. It supports *cc65* (VICE label file), *lyxass* (EQU), *mads* (lab and hea), *llvm-nm*, *llvm-mos* ELF and *vicelbl* label formats.
- **Sprite Bounding Box**: Homebrew and debug builds can draw colored ImGui outlines after Suzy finishes rendering sprites. It can draw all sprites or only SCBs with `SPRCOLL` bit 7 (`$80`) set. Real Lynx hardware ignores this bit, but production builds should clear it.
- **Debug Output**: Homebrew games can send debug text to the Trace Logger window using unused Mikey registers `$FDC0`–`$FDC4`. Enable *Debug Output* in the Trace Logger *Settings* menu and make sure the *Debug Messages* filter is active. See the register protocol below.
| Register | Write |
|----------|-------|
| `$FDC0` | Send buffer to Trace Logger (write any non-zero value) |
| `$FDC1` | Append byte as ASCII character |
| `$FDC2` | Append byte as two hex digits |
| `$FDC3` | Set string pointer low byte |
| `$FDC4` | Set string pointer high byte (writing this triggers the copy) |
### Command Line Usage
```
gearlynx [options] [game_file] [symbol_file]
Arguments:
[game_file] Game file: accepts ROMs (.lyx, .lnx, .o) 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)
--debug-monitor Start debug monitor TCP server (default port: 6502)
--debug-monitor-port N Debug monitor port, 1-65534 (default: 6502)
--comlynx-join N Join local ComLynx shared session 1-255
--headless Run without GUI (requires MCP, debug monitor, or ComLynx)
--portable Store configuration and user data beside the application
-v, --version Display version information
-h, --help Display this help message
```
### MCP Server
Gearlynx includes a [Model Context Protocol](https://modelcontextprotocol.io/introduction) (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](MCP_README.md).
### ComLynx Multiplayer
Choose the same session number in the `ComLynx` menu on every instance and select `Connect`, or start each process with `--comlynx-join N`. Sessions use local shared memory and support up to eight 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.
### VS Code Extension
A source-level debugger for VS Code lives in its own repository:
[BrianPeek/gearlynx-vscode](https://github.com/BrianPeek/gearlynx-vscode). It drives
Gearlynx over the debug-monitor protocol (`--debug-monitor`). The wire contract is
documented in [VSCODE_PROTOCOL_README.md](VSCODE_PROTOCOL_README.md).
### Agent Skills
Gearlynx provides [Agent Skills](https://agentskills.io/) that teach AI assistants how to effectively use the emulator for specific tasks:
- **[gearlynx-debugging](skills/gearlynx-debugging/SKILL.md)** — Game debugging, code tracing, breakpoint management, hardware inspection, and reverse engineering.
- **[gearlynx-romhacking](skills/gearlynx-romhacking/SKILL.md)** — Cheat creation, memory searching, ROM data modification, text translation, and game patching.
Install with `npx skills add drhelius/gearlynx`. See the [skills README](skills/README.md) for details.
## Hardware Accuracy
Gearlynx passes all tests from [Atari Lynx Hardware Test ROMs](https://github.com/drhelius/lynx-tests).
<img width="500" src="https://github.com/user-attachments/assets/7b009bdd-725d-4518-b2c1-79ed3bc20784" />
## Build Instructions
### Windows
- Install Microsoft Visual Studio Community 2026 or later.
- Download the latest SDL3 VC development libraries from [SDL3 Releases](https://github.com/libsdl-org/SDL/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 Gearlynx Visual Studio solution `platforms/windows/Gearlynx.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:
``` shell
brew install sdl3
cd platforms/macos
make 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:
``` shell
sudo apt install build-essential pkg-config libsdl3-dev libgl-dev
cd platforms/linux
make
```
For Ubuntu 24.04, you need to build SDL3 from source first. Use the following commands to build both SDL3 and Gearlynx:
``` shell
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-dev
SDL3_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/SDL3
cmake -S /tmp/SDL3 -B /tmp/SDL3/build -DCMAKE_INSTALL_PREFIX=/usr -DSDL_TESTS=OFF -DSDL_EXAMPLES=OFF
cmake --build /tmp/SDL3/build -j$(nproc)
sudo cmake --install /tmp/SDL3/build
cd platforms/linux
make
```
- Fedora:
``` shell
sudo dnf install @development-tools gcc-c++ SDL3-devel
cd platforms/linux
make
```
- Arch Linux:
``` shell
sudo pacman -S base-devel sdl3
cd platforms/linux
make
```
### BSD
- FreeBSD:
``` shell
su root -c "pkg install -y git gmake pkgconf sdl3"
cd platforms/bsd
USE_CLANG=1 gmake
```
- NetBSD:
``` shell
su root -c "pkgin install gmake pkgconf SDL3"
cd platforms/bsd
gmake
```
- OpenBSD
``` shell
doas pkg_add gmake sdl3
cd platforms/bsd
LDFLAGS=-L/usr/X11R6/lib/ USE_CLANG=1 gmake
```
### Libretro
- Ubuntu / Debian / Raspberry Pi (Raspbian):
``` shell
sudo apt install build-essential
cd platforms/libretro
make
```
- Fedora:
``` shell
sudo dnf install @development-tools gcc-c++
cd platforms/libretro
make
```
## Contributors
Thank you to all the people who have already contributed to Gearlynx!
[](https://github.com/drhelius/gearlynx/graphs/contributors)
## License
Gearlynx is licensed under the GNU General Public License v3.0 License, see [LICENSE](LICENSE) for more information.