GlieseOS

A simple Pixel Watch OS made with Cosmos.

https://github.com/user-attachments/assets/8584ebbb-62d6-49ec-b24a-c1fa0925c170

Boot chain

A concise sequence of what runs and who loads what when deploying and booting GlieseOS:

Android bootloader -> mu UEFI firmware (mu_seluna_platforms)
UEFI firmware -> Limine (BOOTAA64.EFI): the UEFI firmware on the device enumerates the EFI partition and finds BOOTAA64.EFI (the Limine EFI binary). The firmware executes that EFI application as the bootloader.
Limine -> GlieseOS.elf: Limine acts as a UEFI bootloader. It locates GlieseOS.elf on the EFI filesystem, loads the ELF image into memory, and transfers control to Cosmos.

Use the UEFI image from the mu_seluna_platforms custom fork.

Prerequisites

.NET 10 SDK
CosmosOS gen3
adb and fastboot
UEFI image for your watch from mu_seluna_platforms releases
- Use Selene for the Pixel Watch 3 41mm, Luna for the 45mm
Limine bootloader (BOOTAA64.EFI)
Pixel Watch 3 charging cradle (the one that shipped with the watch — required for USB connectivity)

Build

git clone https://github.com/valentinbreiz/GlieseOS
cd GlieseOS
dotnet build

Output:

ISO: bin/Debug/net10.0/linux-arm64/cosmos/GlieseOS.iso
Kernel ELF: bin/Debug/net10.0/linux-arm64/GlieseOS.elf

Deploy to Pixel Watch 3

1. Unlock the bootloader (one-time)

# On the watch: Settings > About > tap Build Number 7 times
# Then: Settings > For Developers > Enable ADB Debugging + Enable OEM Unlock
adb reboot bootloader
fastboot flashing unlock

Note: fastboot flashing unlock will wipe the watch. The watch will reboot into a fastboot menu showing options like Start, Recovery Mode, Reboot Bootloader, Power Off, etc. Press the digital crown to select Start and let the watch boot normally. Go through the initial setup, then go back into Settings and re-enable ADB USB Debugging. Once done, run adb reboot bootloader again before continuing.

2. Run the deploy script

Edit deploy.sh and set the two variables at the top:

UEFI_IMG="/path/to/uefi-selene.img"    # or uefi-luna.img for the 45mm
LIMINE_EFI="/path/to/BOOTAA64.EFI"

Then run:

./deploy.sh

The script will build GlieseOS, flash bootpkg.bin to the inactive modem slot, boot the UEFI, guide you through mass storage, copy Limine + the kernel to the EFI partition, and boot GlieseOS automatically.

The UEFI will find BOOTAA64.EFI (Limine), which loads GlieseOS.elf from the EFI partition. The watch face renders via the UEFI GOP framebuffer.

valentinbreiz/GlieseOS