komaruworld/mocktail

What it does

Mocktail is an experimental compatibility runtime that runs the Android x86_64 Roblox client on Linux, with experimental aarch64 builds for the Android arm64-v8a client. It also works inside FreeBSD's Linuxulator with a Linux userspace, although it is not a native FreeBSD binary. The project is independent and does not distribute the Roblox client.

The runtime supplies the Android ABI and JNI pieces the client expects, then bridges them to SDL3 with Vulkan or OpenGL on the Linux side. Before any native code is loaded, the APK passes signature and ABI checks; the client is downloaded on first launch and the last working copy is retained if an update fails.

Install and run

The stable release is on Flathub:

flatpak install flathub space.bigrat.mocktail
flatpak run space.bigrat.mocktail

For nightly builds from main:

flatpak install --user https://mocktail.bigrat.space/mocktail.flatpakref
flatpak run space.bigrat.mocktail

Arch users can use mocktail-git via an AUR helper, mocktail for the pinned source release, or mocktail-bin for a prebuilt stable package. Fedora 44 has mocktail and mocktail-nightly packages through a DNF repository; Ubuntu 26.04 has equivalent APT packages and a signing key. Direct AppImage, DEB and RPM downloads are on the website and GitHub Releases.

Configuration

Runtime behavior can be tuned with FFlag overrides in $XDG_CONFIG_HOME/mocktail/fflags.json (usually ~/.config/mocktail/fflags.json). Mocktail applies the file on the next launch. PC profiles default to the legacy Charts page because the newer SDUI page produces a blank screen from Color3 errors; an explicit FFlagLuaAppChartsAppPage value overrides that default. The file takes a JSON object with string values, for example:

{
  "FFlagExample": "True",
  "DFIntExample": "120"
}

Build from source

Building requires CMake 3.20+, Git, pkg-config, LLD, binutils, a C++17 compiler, and a sizable dependency set including SDL 3.4+, SDL3_ttf, Vulkan, EGL, libplacebo, GTK4, libadwaita 1.6+, WebKitGTK 6.0 and more. The README lists package commands for Ubuntu 26.04+, Arch and Fedora 44+. After installing dependencies:

git clone --recurse-submodules https://github.com/komaruworld/mocktail.git
cd mocktail
make build
./build/mocktail

FreeBSD setup and launch steps are in the project's FreeBSD guide.

Constraints

aarch64 builds exist, but Roblox runtime validation on that architecture is still experimental. FreeBSD support is likewise experimental and has only been tested with an x86_64 Fedora 44 userspace inside Linuxulator. Mocktail does not work with hardened_malloc and may fail to start or crash at runtime when it is enabled, so run without it. The project is Apache-2.0 licensed, and third-party components keep their own licenses.

HotRepo's take

Mocktail entered the GitHub C++ daily list on 2026-11-07 at 15th place with 8 new stars that day, while sitting at 422 stars and 44 forks. That single snapshot shows a modest but visible presence on the C++ list; it does not establish a trend. The interesting technical bet is the layer itself: reusing the Android client's ABI through Bionic and JNI and connecting it to native SDL3, Vulkan and OpenGL rather than rebuilding the game for desktop. The README makes the experimental boundaries explicit for aarch64 and FreeBSD, which matters for anyone expecting stable play.