Asahi Linux Survives Golden Gate on One APFS Flag

Asahi Linux traced a Golden Gate boot lockout to one APFS flag Apple ignored from macOS 12 to macOS 26. The Linux volume never left the disk. Apple’s picker simply stopped listing it.

The project’s June warning on dual-boot access told people to stay off the macOS 27 beta. Five days later the Asahi Installer was writing the missing bit itself, and that is still the repair Golden Gate users need as the first Apple-silicon-only macOS heads toward a public release.

The Linux Volume Vanished From Apple’s Boot Picker

Apple announced macOS 27 Golden Gate at WWDC on June 8, 2026, and shipped the first developer beta the same day. By the next morning the Asahi Linux project was telling every dual-boot user to refuse the upgrade.

“Do NOT upgrade to macOS 27 Golden Gate,” the team wrote. Apple had changed how the boot picker and the Startup Disk app detect a valid OS volume. Used from macOS 27, an Asahi partition no longer appeared. The team called it a bug and filed Feedback FB22994760.

If you have already upgraded to the beta and noticed that your Asahi partition has disappeared, do not stress. Your Asahi partition is still there, and you have not lost any data.

Asahi Linux project, Treehouse Mastodon, June 9, 2026

The Apple Silicon boot picker is a full macOS app that runs in the recovery environment of the default boot volume, so its rules follow whichever macOS you set as the default. Set an older copy as the Startup Disk and Asahi came back. Make Golden Gate the default and Linux dropped off the list.

The first installer patch was a hard block. Until the team knew what Apple had changed, the installer printed a version of that warning and quit if you launched it from the macOS 27 beta. Fedora Asahi Remix, the project’s flagship end-user distro, sat on the same boot path as every other Asahi install. There was no separate escape hatch.

Apple Began Enforcing a Flag It Had Ignored Since Monterey

James Calligeros, writing the project’s Linux 7.1 progress report on June 30, 2026, described what the blank picker actually was. The name in the boot list is not the Linux root. Apple’s tools will only treat a “valid” macOS install inside an APFS container as a boot target. The Asahi Installer therefore builds a small APFS container, 2.5 GB, with just enough macOS on it to pass that check, and it puts m1n1 in as the kernel.

That trick ran unchanged from macOS 12 to macOS 26. Apple even fixed bugs in its own tools that only showed up when the payload was a raw binary rather than a real XNU kernel. Then Golden Gate started hiding the volume.

diskutil still listed every Asahi partition. No data was gone. The same machine still booted Linux when the picker ran from a second install of macOS 26. chaos_princess, an Asahi developer, went back through Apple’s macOS Installer and old traces from the project’s first work on the boot tools. The installer writes APFS metadata before it reboots, and one of those bits marks the volume as bootable. Until macOS 27, the boot tooling ignored this flag entirely. Set it by hand on an Asahi container and the volume returned to the Golden Gate picker with no other change.

THE PICKER’S NEW RULE

The same check also hid some older macOS installs that lived on separate partitions. That is the behavior of a broader volume test, not a filter aimed at Linux. Early speculation treated the blank slot as a possible lock on third-party operating systems. The flag was already in Apple’s installer. Golden Gate started reading it.

Installer 0.8.3 Writes the Missing Boot Flag

chaos_princess had a fix pull request on the installer the day after the public warning. On June 13, 2026, five days after the first Golden Gate beta, the project tagged Asahi Installer v0.8.3. New installs set the bootable flag automatically. Existing volumes get a dedicated installer mode named “Fix macOS 27 boot picker compatibility.”

We have tagged and released v0.8.3 of the Asahi Installer, which includes a fix to make Asahi installations visible to the macOS 27 boot picker and Startup Disk applications. If you installed the macOS 27 beta and have been affected, please re-run the installer from macOS.

Asahi Linux project, Treehouse Mastodon, June 13, 2026

The Asahi Linux installer source is still the supported path for people who can boot macOS. For people already in Linux, chaos_princess also wrote asahi-fix27, a small tool that sets the same bit from the Linux side. Run it with sudo. If it finds partitions with the VolBootable flag unset, it lists them and asks you to run it again with –confirm. If it finds none, it exits with no output. The project wanted more test data before deploying that path automatically, because a bad write to APFS metadata is a filesystem event, not a cosmetic one.

Advice from the June 13 note did not change with the patch. Developer betas are still a bad idea on a machine you need. The team said it was unlikely those builds were tested with third-party operating systems installed.

The 2.5 GB Stub That Pretends to Be macOS

Asahi’s dual-boot design is a bet on Apple’s picker, not a second bootloader sitting beside iBoot. Hold the power button and the Mac loads the recoveryOS paired with the default volume, then shows a list. The boot picker under recoveryOS scans internal and external volumes for OS installs that look like Apple’s APFS layout. Linux never appears as Linux. It appears as that stub, with m1n1 standing in for XNU so iBoot will launch it.

Users never have to drop into Recovery and type bless commands on a good day because the stub satisfies Apple’s idea of a bootable install. The cost of that convenience is that a metadata check Apple ignored from macOS 12 to macOS 26 can blank the only supported way onto the Linux volume. The files are still there. The picker is the gate.

The project has lived with that gate on purpose. Calligeros wrote that Asahi bet early that Apple would not constantly break platform details that were expensive to change, and that the bet had mostly paid off on silicon blocks that stay still across chips. The boot picker is not one of those still blocks. It is a macOS app, rebuilt with the OS, and its detection rules moved in Golden Gate without a public document for third-party volumes.

Apple has not posted a public reply to FB22994760. The repair did not wait for one. Setting the flag the macOS Installer already writes was enough to put Linux back on the list.

What Dual-Boot Users Should Run Before Golden Gate

Re-run the Asahi Installer from macOS and choose “Fix macOS 27 boot picker compatibility,” or use the Linux-side tool if you can still boot Asahi. The volume is still on disk. Anyone who takes the public Golden Gate build without that bit set will see the same blank picker the first beta produced in June.

THE REPAIR PATHS THAT STILL WORK

• Installer option: Boot macOS, launch the current Asahi Installer, and choose “Fix macOS 27 boot picker compatibility” so it writes the bootable flag on the existing stub.
• Linux tool: From a running Asahi session, build and run the VolBootable repair from Linux, then pass –confirm after it lists partitions with the flag unset.
• Older macOS default: If Golden Gate already hid the volume and you still have macOS 26 or older, set that older install as the default Startup Disk so the picker runs from a build that still lists Asahi.
• Fresh Golden Gate tests: Put macOS 27 on a secondary volume and keep a stable macOS as the default if you want the beta without giving the picker to Golden Gate.

The June 9 note was blunt about support. The project said it would not support users who installed the macOS 27 beta without a rollback plan, such as keeping at least one stable macOS install. That line was about the first days, when the only way home was an older picker. The flag repair is now the durable fix. The rollback warning still applies to anyone who upgrades with no second macOS and no repaired stub.

If Golden Gate Is Already the Only macOS

A machine that has only macOS 27 and an unrepaired Asahi stub cannot use the “set macOS 26 as default” trick, because there is no older picker to run. The installer repair has to be launched from that Golden Gate volume, which is why v0.8.3 had to stop blocking macOS 27 and start writing the flag there. If you cannot reach the installer and cannot reach Linux, you are in the hole the June warning was written to prevent.

Battery Firmware Dropped to a Single Byte

Golden Gate did not stop at the picker. It also shipped firmware updates for peripherals with global firmware, including the SMC, the chip that handles battery data among other jobs. Asahi’s Linux power-supply driver talks to the SMC for charge state, voltage, time until empty, and battery health, and it sets charge start and stop thresholds to protect the pack.

macOS 27’s SMC firmware changed one of those battery interfaces from returning a 32-bit integer to returning a single byte. The old driver read that as a failed battery and, under some conditions, kicked an emergency shutdown to protect the machine. The project patched the downstream kernel. From version 7.0.12 the driver accepts both firmware ABIs.

Calligeros used that bug as a second warning. Global firmware updates are effectively permanent. Rolling them back means a DFU restore of the Mac. “Please refrain from installing developer betas going forward,” he wrote. The team keeps sacrificial machines for that work. A production laptop is a poor substitute.

Golden Gate Is Still Beta as Shipping Season Starts

macOS 27 was still a beta in early September. The public beta opened on July 13, 2026. Developer beta 8 landed on August 31. Apple has not posted a public Golden Gate date, and the OS has not shipped as a free upgrade through Software Update. New Mac desktops announced in late August have been described as arriving with macOS 27 already installed later in September, which is how a public build usually lands: on hardware first, then as the upgrade everyone else clicks.

FROM THE FIRST BETA TO THE FLAG FIX

1. June 8, 2026: Apple ships the macOS 27 Golden Gate developer beta after the WWDC keynote.
2. June 9, 2026: Asahi Linux posts the PSA, files FB22994760, and blocks the installer on macOS 27.
3. June 10, 2026: chaos_princess files the installer pull request that sets the bootable flag on old volumes.
4. June 13, 2026: Asahi Installer v0.8.3 ships with automatic flag writes and the repair option.
5. June 30, 2026: The Linux 7.1 progress report documents the flag, the SMC byte change, and the ask not to run developer betas on daily machines.

WHAT WE KNOW

• The cause: macOS 27 requires an APFS bootable-volume flag that the tools ignored from macOS 12 to macOS 26.
• The data: diskutil still showed every Asahi partition; the failure was visibility, not deletion.
• The fix: Installer 0.8.3 writes the flag on new installs and offers a repair mode for old ones.

WHAT IS UNCONFIRMED

• Apple’s reply: Feedback FB22994760 has no public response on the record.
• Public Golden Gate day: Apple has not posted the release date for the finished OS.
• asahi-fix27 as default: the Linux-side writer is still a test tool, not the automatic path.

Anyone who skipped the June betas and plans to take the finished Golden Gate build is in the same place the first testers were, minus the panic. The stub is still 2.5 GB of pretend macOS. The picker is still a macOS app. The flag still has to be set. Run the installer repair before the upgrade, or expect the Linux entry to vanish the first time Startup Disk runs under macOS 27.