# Cutefish is back and wants to run Mac apps on Linux without recompiling them: meet Reef - **Published on:** 2026-11-11 - **Category:** News - **Original page:** https://free-linux.com/articles/cutefish-mac-apps-on-linux-reef The former CutefishOS returns on Debian 13 under its original creator and shows Reef, an in-house layer that already opens TextMate, CotEditor, Ghostty and NetNewsWire exactly as they are downloaded for macOS. What works, what doesn't and why you can't try it yet. --- In 2021 **CutefishOS** got a lot of attention: a desktop with a global menu bar, a Dock and a macOS look, written from scratch in Qt. Its last release, 0.8, came out in January 2022, and by 2023 the code had stopped changing. Now it is back under a new name, **Cutefish**, on top of **Debian 13**, with a goal that until recently sounded like a joke: **running Mac apps without modifying or recompiling them**. The layer that does it is called **Reef**. It is an in-house project, it can't be downloaded yet and, for now, it is closed source. Even so, what the project has shown deserves a careful look. ## Who is behind it The same people as before. The `cutefishos` GitHub organisation is the one from 2021, its repositories (`cutefish-core`, `filemanager`, `cutefish-compositor`…) still carry the 0.1 to 0.8 tags, and the last commit before the pause dates from June 2023. Nearly all of the code, then and now, is by **Reion Wong**, who founded the project. The new domain, `cutefish.org`, was registered on 19 October 2026, the same day the repository that packages the distribution was created. Since then the blog has published four posts in two weeks: how the distro is built (20 October), a server that lets AI agents drive the desktop (20 October), the introduction of Reef (23 October) and its "first milestone" (2 November). ## What Cutefish is today The website sums it up as "a Linux distribution for people at home on a Mac". Underneath, a lot more has changed than it seems: - **Debian 13 "trixie" base.** The 8 November nightly ISO ships Debian's 6.12.116 kernel and the rest of its packages from the official archive. Cutefish adds its own in a separate APT repository, `trixie-nightly`. - **Its own desktop from top to bottom:** compositor (`cutefish-compositor`), session manager, installer, file manager, terminal, text editor, calendar, calculator, video player and system monitor. - **A new toolkit.** The apps are no longer QML as in 2021: they use `cutefish-toolkit`, a native C++ toolkit that draws with **Skia**, the graphics library behind Chrome and Android. Qt 6 is still installed so Qt apps blend in through `cutefish-qt-plugins`. - **Licences:** BSD-3-Clause for almost all the code (core, compositor, toolkit, settings, file manager) and GPL-3.0 for the terminal and the icons. There is no stable release. What exists are **Cutefish 1.0 nightly ISOs for amd64 (1.56 GB) and arm64 (1.61 GB)**, built every night, and the download page warns that "nothing here is an official release yet". You can check that an ISO came out of the project's build workflow and hasn't been changed since with `gh attestation verify`. If you already run Debian 13, you can add the repository and install just the desktop with `apt install cutefish-desktop`. ## Reef: Mac apps without an emulator A Mac app does very little on its own. To open a window, draw text or work out the date, it calls into macOS: AppKit for windows and controls, Foundation for text, dates and files, Core Graphics for drawing, SwiftUI for modern interfaces… None of that exists on Linux. Reef means writing its own version of those interfaces, one that behaves exactly like Apple's, because if the answer is even slightly off, the app lays out its window wrong, draws nothing or crashes. It is the same idea as Wine with Windows: **the processor isn't emulated**, the libraries are reimplemented. The app's code runs directly on the CPU, like a Linux program. To get there Reef includes: - a loader for the Mac binary format, **Mach-O** (Linux uses ELF); - an **Objective-C** runtime and **Swift** support; - a low-level system library; - and its own versions of AppKit, Foundation and the other frameworks, including a partial implementation of **SwiftUI**. The size gives an idea of the effort. On 23 October Reef had over 300,000 lines across more than 70 frameworks, with AppKit and Foundation above 70,000 lines each. Ten days later the project spoke of **about 460,000 lines of its own code across more than 80 frameworks**. Mac apps don't look like guests: they open in a normal window, put their menus in the Cutefish menu bar, show up in the Dock, and the compositor gives them the same shadows and animations as native apps. ### What already works In the 23 October introduction: - **Itsycal** (menu bar calendar): fully working, with its status icon, calendar, context menu and settings. - **TextMate** and **Hex Fiend**: open and edit files. - **CotEditor**: opens, edits and saves, with syntax highlighting, inspector, search and settings. - **Things 3**: works, though not finished. Part of its interface is drawn by Reef's SwiftUI. The 2 November "first milestone" added: - **NetNewsWire**, fully working, with the unread count on its Dock icon. It is the first app to use **WebKit**, Safari's web engine, ported by the project (the `cutefish-webkit` repository appeared on 5 November). - **Ghostty**, the terminal, with its **Metal** renderer, inspector and custom shaders. - **Keka**, which creates and extracts zip and tar.gz archives, and **Speedtest by Ookla**, with full tests and history. - **CotEditor** now remembers windows and unsaved documents, and supports tabs and full screen. All of them install from the same disk image a Mac user downloads. ### What it costs in performance The project compares CotEditor on Reef with Cutefish's native editor on the same laptop, and doesn't hide the gap: | Test | CotEditor on Reef | Cutefish editor | |---|---|---| | Launch to first frame | 235 ms | 115 ms | | Open a 20,000-line file | 0.50 s | 0.12 s | | CPU to type 80 characters | 1.4 s | 0.17 s | | Frame while scrolling | 4.4 ms → **3 ms** | 1.2 ms | The last row combines both posts: 4.4 ms on 23 October and 3 ms on 2 November. The second post also says CotEditor dropped from 245 to **146 MB of memory** with a 20,000-line file, that Ghostty resizes at 2.4 ms per frame (down from 6.7 ms), and that NetNewsWire, Ghostty and CotEditor open 10 to 40 ms sooner. ### What won't work The limit is set by Apple, not by Reef: **anything that goes through Apple's servers**. That rules out iCloud, Sign in with Apple, in-app purchases and App Store subscriptions. Apps sold **only** on the Mac App Store can't be installed at all. Apps that sell their own licences or sync with their own services are not affected. Nor is it a full macOS. Reef **only targets graphical apps, and only on Cutefish**: it relies on its toolkit, compositor and desktop, and doesn't try to run command-line tools. That is where it parts ways with **Darling**, the veteran project that aims to run macOS software on any Linux. Cutefish says it uses no code from either Darling or Wine. The blog doesn't say which architectures Reef supports. Since it doesn't emulate the CPU, you would expect an x86-64 PC to use the Intel half of each app and an arm64 machine the Apple Silicon half. Most Mac apps ship as universal binaries containing both. That is our inference, not something the project has stated. ## Where does the code come from? Reef is not open source "for now". What the project does list is the Apple open source pieces it uses, each under its own licence: **Core Foundation** (from `swift-corelibs-foundation`), **libdispatch** and **Swift**, all three Apache 2.0, and the **LZFSE** compressor (BSD-3-Clause). It also bundles libc++, libc++abi, libunwind, SQLite, curl and Tcl, and explains that it studies the code Apple publishes in `apple-oss-distributions` so its behaviour matches. So the "free software" label needs a footnote. The Cutefish desktop is free software. The piece that grabs the headlines, for now, is not. ## AI agents too The other new piece is **`cutefish-computer-use`**, an **MCP** server that ships with the desktop and lets agents such as Claude Code, Codex or Claude Desktop see the screen, click, type and move windows. Unlike other approaches, it doesn't record the screen or fake a keyboard: control goes through the compositor itself. The first time, Cutefish asks for permission, and the agent can't answer that dialog. While it acts, a stop button sits in the status bar, and any mouse movement or keypress from the user pauses it. It can't touch password dialogs, permission prompts or the lock screen either. Granted permissions are reviewed under Settings › Privacy. ## Our take If Reef delivers, Cutefish stops being "another distro that looks like macOS" and becomes the only one that runs part of its software. That matters a lot to anyone coming back to Linux who misses two or three specific apps. But read it calmly: the layer can't be tried, has no date ("Reef will ship in Cutefish as soon as possible") and its code is closed. On top of that, the project depends almost entirely on one person and has already been dormant for three years. And reimplementing Apple's interfaces is a huge job. Wine has spent more than thirty years doing it for Windows. What you can try today is the desktop, and a nightly ISO in a virtual machine is enough for that. We have added it to the catalogue in its [Cutefish page](/cutefish), with the 0.1 to 0.8 history and the 1.0 nightly branch. If you want Mac-like alternatives that are already stable, have a look at [elementary OS 8.1](/articles/elementary-8-1). For the base, there's [Debian 13](/articles/debian-13). And if what draws you in is running another system's software, our guide to [Linux gaming with Proton](/articles/linux-gaming-steam-deck-proton) explains how Wine does the same thing with Windows. **Sources:** Cutefish blog: [Running Mac apps on Cutefish](https://cutefish.org/blog/running-mac-apps/) (23 Oct 2026), [Mac apps on Cutefish: the first milestone](https://cutefish.org/blog/mac-apps-first-milestone) (2 Nov 2026), [How Cutefish is built](https://cutefish.org/blog/how-cutefish-is-built) and [Letting agents use the desktop](https://cutefish.org/blog/letting-agents-use-the-desktop/) (20 Oct 2026); [downloads and nightly ISO package list](https://download.cutefish.org/); [cutefishos organisation on GitHub](https://github.com/cutefishos); [Darling](https://www.darlinghq.org/) and [Wine](https://www.winehq.org/).