Goals
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Modularity. The frontend contains no emulation core and no system-specific knowledge. Cores are external, self-contained packages (.chimeraCore), each maintained in its own repository under its own license, loaded explicitly like a ROM. Chimera includes none and downloads none.
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Performance. All functional machinery (the sandbox host, movies, savestates, file formats, the running machine itself) lives in libchimera, a native C++ engine the GUI calls into.
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Stronger reproducibility guarantees. Every core runs inside the miniBox sandbox, so the same project and input files play the same movie on any machine.
Chimera is not designed for casual play. For that, use the original emulators directly, or a multi-emulation frontend such as RetroArch.
Cores
Chimera does not include cores and does not download them. To use a core, download its .chimeraCore package from the core's own project (linked below) or build it yourself, and put it in the cores folder beside Chimera.
Tools > Core Manager... lists the cores in that folder and lets you point Chimera at a different one (docs/core-manager.md).
Emulation cores
| Core | Systems |
|---|
| quickerNES | Nintendo Entertainment System / Famicom |
| QuickerNesHawk | Nintendo Entertainment System / Famicom, Famicom Disk System |
| ares | Nintendo Entertainment System / Famicom, Super Nintendo, Satellaview, Sufami Turbo, Nintendo 64, Nintendo 64DD, Game Boy / Game Boy Color, Game Boy Advance, Mega Drive / Genesis, Mega Drive 32X, Sega CD / Mega CD, Sega CD 32X, Master System, Game Gear, SG-1000, PlayStation, Atari 2600, Atari 5200, ColecoVision, MSX / MSX2, PC Engine / TurboGrafx-16 / SuperGrafx, PC Engine CD / TurboDuo, Neo Geo AES, Neo Geo Pocket / Color, WonderSwan / WonderSwan Color |
| Snes9x | Super Nintendo |
| Dolphin | GameCube, Wii |
| Azahar | Nintendo 3DS / New Nintendo 3DS |
| melonDS | Nintendo DS, Nintendo DSi |
| Gambatte | Game Boy / Game Boy Color, Super Game Boy, Game Boy Link (two to four Game Boys joined by cable) |
| Genesis Plus GX | Mega Drive / Genesis, Sega CD / Mega CD, Master System, Game Gear, SG-1000, Sega Pico |
| Flycast | Dreamcast, Sega NAOMI / NAOMI 2 (arcade), Sammy Atomiswave (arcade) |
| Mednafen | Sega Saturn, Sega ST-V (arcade), Virtual Boy, PC-FX, Atari Lynx |
| FBNeo | Capcom CPS-1 / CPS-2 / CPS-3 (arcade), Neo Geo MVS (arcade), Neo Geo CD, Sega System 16 (arcade) |
| MAME | Arcade (the arcade machines of MAME) |
| MAME Home Systems | Atari 7800, Intellivision, Vectrex, Odyssey 2 / Videopac, Channel F, Amstrad CPC / CPC+ / GX4000, TI-83, BBC Micro |
| DuckStation | PlayStation, Namco System 11 (arcade), Konami GQ (arcade) |
| PCSX2 | PlayStation 2 |
| PPSSPP | PlayStation Portable |
| Vita3K | PlayStation Vita |
| RPCS3 | PlayStation 3 |
| xemu | Xbox |
| Xenia | Xbox 360 |
| Opera | 3DO Interactive Multiplayer |
| Zeebx | Zeebo |
| Stella | Atari 2600 |
| Virtual Jaguar | Atari Jaguar, Atari Jaguar CD |
| Cadmium | CHIP-8, SUPER-CHIP, XO-CHIP and their relatives |
| TIC-80 | TIC-80 (fantasy computer) |
| Uzem | Uzebox |
| AppleWin | Apple II / II Plus / IIe (and the Pravets, TK3000 and Base64A clones) |
| PUAE | Commodore Amiga, Amiga CD32, Commodore CDTV |
| VICE | Commodore 64 |
| Fuse | ZX Spectrum 16K / 48K / 128K / +2 / +3, Timex, Pentagon, Scorpion |
| MAME X68000 | Sharp X68000 |
| DOSBox-X | MS-DOS, Windows 3.1 / 95 / 98 |
| PCem | MS-DOS, Windows 3.1 / 95 / 98, Windows XP, Linux (x86) |
| Ruffle | Flash |
| EKA2L1 | Symbian / Nokia N-Gage |
| touchHLE | iPhone OS 2.x-4.0 (iPhone, iPod touch and iPad apps) |
| FreeJ2ME-Plus | J2ME (Java games of 2000s phones) |
| Godot 4.7 | Godot 4.7 (games made with the Godot Engine) |
| Godot 4.6 | Godot 4.6 |
| Godot 4.5 | Godot 4.5 |
| Godot 4.4 | Godot 4.0 to 4.4 |
| OpenBOR | OpenBOR (2D beat 'em up games) |
| Ikemen GO | Ikemen GO (fighting games made with it, and M.U.G.E.N characters and stages) |
Game cores
One game each, run from the game's own files (docs/game-cores.md).
| Core | Games |
|---|
| SDLPoP | Prince of Persia (DOS) |
| SDLPoP2 | Prince of Persia 2: The Shadow and the Flame (DOS) |
| OpenSamurai | Sword of the Samurai (DOS) |
| SyndicatFX | Syndicate (DOS) |
| rawgl | Another World |
| RSDKv3 | Sonic CD (the 2011 remake) |
| RSDKv4 | Sonic the Hedgehog and Sonic the Hedgehog 2 (the 2013 remasters) |
| RSDKv5 | Sonic Mania |
| DSDA-Doom | Doom, Doom II, Final Doom, Heretic, Hexen, Chex Quest, Freedoom |
| Open4DBoxing | 4D Sports Boxing (DOS) |
| SRB2 | Sonic Robo Blast 2 |
SRB2 is published by its author, P-AS, from their own repository.
Getting a build
The frontend is built for Linux and Windows and published here:
- Latest development build - rebuilt on every change to
main that passes the gates, and replaced each time. Nothing is published that did not pass them. Not for submissions: a dev build is replaced on every change, so it may stop being downloadable and a movie made on it can stop being replayable. Do not use one to produce a TAS for submission to toolAssisted.run - use a nightly.
- Nightly builds - dated, immutable, and kept forever. Cite one of these in a bug report or beside a movie: a run is only reproducible while the build that recorded it still exists, and this is what a TAS submitted to toolAssisted.run should be made on.
A bundle carries no cores, and Chimera never reaches the network - it downloads
nothing, not a core and not a list of them. To set one up:
- Download a build above and unpack it.
- Download the
.chimeraCore package of each core you want from that core's
releases page (the Cores tables link them), or build it.
- Put the packages in the
cores folder beside Chimera (chimera.exe on
Windows, chimera on Linux), and start Chimera.
Each core publishes a dev build and nightly releases the same way, and its
nightlies are never deleted - which is what lets a movie name the exact package
that recorded it and still be replayable years later.
Every bundle carries BUILD.txt, naming the exact commit it was built from, and
LICENSES.md, stating its terms. Adding a core adds that core's terms,
and some of them (Genesis Plus GX, Opera, Snes9x) forbid commercial use, which
binds whatever they are installed into; Chimera shows a core's licence once it
is in the folder.
Core packages published before the split are kept in the
cores
release, named by SHA1. It no longer grows - each core archives its own now -
but movies recorded then still cite packages in it.
Working with an AI agent
An AI agent (Claude Code, or any program that speaks MCP) can look at the project you have open and, if you allow it, edit it. Start the server from Tools > MCP Server..., which also shows the command that sets the agent up; it is off until you start it, and nothing leaves your machine. An agent can also work with no window at all, on a machine of its own. See docs/mcp-server.md.
Building
The canonical build is Linux-hosted and meson-mediated, and produces Chimera for both operating systems: the engine, its libraries and the window (Qt 6.12), built with gcc for Linux and cross-built with mingw-w64 for Windows. Clone with --recursive; the repository contains no precompiled binaries, and
no cores - tools/fetch-cores.sh puts the published ones in build/Cores if
you want a working set without opening the frontend.
tools/ci-chimera.sh # Qt 6.12 for Linux into ~/qt (aqt), then the Linux build
or by hand, with Qt 6.12 for Linux at $QT:
PATH="$QT/libexec:$QT/bin:$PATH" PKG_CONFIG_PATH="$QT/lib/pkgconfig" \
meson setup build/meson-linux --prefix "$(pwd)/build" --libdir dll -Dqt_ui=enabled
meson compile -C build/meson-linux && meson install -C build/meson-linux
Linux requirements: meson, ninja, cmake, gcc, and Qt 6.12 (Core, Gui, Qml, Quick, QuickControls2); mingw-w64 for the Windows build. The release builds Qt itself, for both systems, without its network module (tools/build-qt-linux.sh, tools/build-qt-windows.sh), and tools/build-bundle.sh makes the two bundles from it.
The frontend ships no cores, so get at least one before running it - either the
published packages, or a core repository cloned wherever you like:
tools/fetch-cores.sh # every published core -> build/Cores
<core checkout>/waterbox/build-package.sh -r $PWD # or build one yourself
To run: build/meson-linux/source/ui/chimera (with CHIMERA_CORES_DIR=build/Cores
for the cores a checkout holds), then File > New Chimera Project... and pick a
core. --headless runs it with no window and no display, for a script or a test.
The witness gate runs with tests/synth/run-witness.sh. The engineering log (objectives, procedure, and the sharp edges found along the way) is in docs/design-principles.md. Building a new core, and joining it to this bundle, is docs/porting-a-core.md.
Reporting a problem
Open an issue on this repository, whichever core it concerns - one inbox,
and the issue template asks for what a fix needs. What settles most
reports before anybody opens a debugger:
- Help > Report an Issue shows the link to the report form and fills in
its first lines for you: build, core, system, processor and memory, files
and changed settings.
It can also save the files worth attaching as one zip.
- The build strings. Help > Copy Version Info puts the frontend's build
and the running core's version on the clipboard, in the template's words.
A frontend and a core from different days may not
understand each other's states, so before reporting a save/load problem,
match them.
- The project file. A
.chimeraProject is small and names every file
by hash, so attach it rather than describing it.
- The three crash files. When Chimera or a core dies it writes a crash
note and a minidump,
<date> pid<N>.txt and .dmp, into the Crashes
folder of the data directory (Config > Data Directory... opens it;
%LOCALAPPDATA%\Chimera by default on Windows), and the sandbox writes
minibox-diag.log next to Chimera's program. Attach all three: the note
carries the faulting instruction and the machine's last words, and two of
three crashes in one recent report were fixed off those files alone.
- The core's log. Help > Export Core Log... keeps everything the core
says in a file you choose; it is off until asked for, and reboots the core
so the log starts at boot. Use it again to turn it off, and attach the file.
Contributing
Pull requests are welcome, from people and from people working with AI assistants alike. A contribution is judged on its merits: it should build, pass the witness gate, and keep to the project's scope. The one firm requirement is legal cleanliness: you must have the right to submit the code under this repository's MIT license, and anything derived from other works must respect their licenses and carry the attribution they require.
Credits and license
Chimera began as a fork of BizHawk. It is provided under the MIT License, keeping the BizHawk team's copyright on the parts that come from BizHawk; see LICENSE for the terms and NOTICE for whose work it is and what the terms do not cover: the native libraries built from extern/, and why core packages carry their own licenses. The people behind Chimera itself are in CREDITS.md.
