ztOS Brings a Windows Phone 8.1-Style Linux OS to the Galaxy S9—But It’s Alpha Only

What ztOS actually is​

ztOS is a phone OS built around the ztMETRO shell, which mimics the look and motion of Windows Phone 8.1. It runs on Arch Linux ARM and mainline Linux, with its own apps, an updater and an SDK for apps in Python and Qt. The shell and its components are written in C and accelerated with OpenGL.

That makes ztOS a different thing from an Android launcher or skin. It is a separate Linux phone stack with a Metro-style front end. Windows Central framed it as a fan-made way to bring Windows Phone back to one specific Android device. Windows Central describes ztOS as designed to look and feel exactly like Windows Phone 8.1. The code is not Microsoft's, and Microsoft is not behind it.

The device boundary: one Galaxy S9 variant​

The project's own words are narrow. It is currently ported for a Samsung Galaxy S9 (starlte), and the author hopes to add more devices in future. The documented status page names the exact model: Galaxy S9 SM-G960N, starlte, Exynos 9810, running mainline Linux 7.1.

If you own a different Galaxy S9 variant, or any other Android phone, treat this as unsupported. Wider device support is only a stated hope.

What's in the box​

The repository lists several components:

• ztMETRO: the shell, covering Start, the app list, the action centre, the keyboard and the lock screen.
• ztOSCoreNetworking: the modem, calls, messages and mobile data, plus Wi-Fi joining.
• ztos-update: the updater, with an Updates app.
• ztOS installer: it builds ztOS and installs it in QEMU or on the phone.

One fork's notes also say the keyboard uses a Windows Phone layout, with an extra row of Esc, Tab, Ctrl, Alt and arrow keys for terminals. That is a nice touch for a phone that can run Linux terminal apps.

The alpha reality check​

This is where the nostalgia needs to cool down. The build is labelled ALPHA-2 for the Galaxy S9 (SM-G960N / starlte). The repository's status tables follow the style of postmarketOS device pages. They separate what was tried on the phone (tested) from what is written but not yet exercised in real use (untested).

Notes in one fork of the repository show how rough some edges still are:

• Rotation lock, flashlight, location and brightness only remember their state, because the kernel has nothing behind them yet. There is also no notification service. That fork may be older than the main repository, which has since moved on.
• At the time of that fork there was no lock-screen PIN.
• A separate set of notes warns: never take a core offline on this kernel, because it cannot be brought back without a reboot.

Treat these as snapshots of a fast-moving alpha. Check the current repository status before drawing conclusions about any one feature.

Installation and recovery: what the project says​

The project claims its installer is deliberately conservative. The notes say ztOS needs the stock Android partitions to stay on the phone. The modem's boot daemon and the sensor hub's daemon are Samsung programs that run from a read-only root assembled from the phone's SYSTEM and VENDOR partitions. The installer writes only BOOT and USERDATA, and the notes say not to wipe the others. The EFS partitions, which hold the IMEI and calibration data, are never touched.

There is a recovery path as well. One fork's notes say Arch lives on the BOOT partition and TWRP on RECOVERY. A normal power-on lands in Arch, and "reboot recovery" or Volume Up + Bixby + Power lands in TWRP. They add that the Galaxy S9 boot flow falls back to TWRP by itself after a crash or watchdog reset.

These are the project's own claims, not independent guarantees. Flashing any custom OS can brick a phone. Anyone considering it should check the exact model, read the current instructions, and back up everything first.

Is it "built by Claude"?​

Windows Central says the project is spearheaded by Claude. I could not verify how much of the code an AI system wrote, or what role it played. The repository material I reviewed doesn't establish that claim. I'd treat AI authorship as unconfirmed unless the maintainer says so.

Why Windows readers might care​

Windows Phone died years ago, but its Metro design still has fans. ztOS shows that a lone developer can now put together a full mobile Linux stack with a custom shell, SDK and updater. LinMob's weekly mobile Linux roundup also picked it up. LinMob describes it as a mobile Linux project based on Arch Linux ARM, with a Windows Phone 8.1-inspired interface and native Linux applications.

Still, the practical picture is simple:

• It is not Windows Phone and has no Microsoft support.
• It is not a drop-in Android replacement.
• It supports one Exynos Galaxy S9 model.
• It is a hobby-grade alpha for people comfortable with flashing phones and recovering them.

If you're one of those people and you have a spare SM-G960N, it's an interesting weekend project. For everyone else, it's a good reminder that Live Tiles still have fans, even if Microsoft doesn't.