Metal kernels 🤘

Instructions on this page assume that you installed Nix with the Determinate Nix installer.

Targeted macOS versions

Since new macOS versions get adopted quickly, we only support the latest major macOS version except for the first weeks after a release, when we also support the previous major version.

We currently support macOS 26.0 and later on ARM64 (Apple silicon).

Requirements

To build a Metal kernel, the following requirements must be met:

• Xcode 26.x must be available on the build machine.

• xcode-select -p must point to the Xcode 26 installation, typically /Applications/Xcode.app/Contents/Developer. If this is not the case, you can set the path with: sudo xcode-select -s /path/to/Xcode.app/Contents/Developer

• The Metal Toolchain must be installed. Starting with macOS 26, this is a separate download from Xcode. You can install it with: xcodebuild -downloadComponent MetalToolchain

• The Nix sandbox should be set to relaxed, because the Nix derivation that builds the kernel must have access to Xcode and the Metal Toolchain. You can verify this by checking that /etc/nix/nix.custom.conf contains the line:

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  sandbox = relaxed

  If you had to add the line, make sure to restart the Nix daemon:

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  sudo launchctl kickstart -k system/systems.determinate.nix-daemon

You can check these requirements as follows. First, you can check the Xcode version as follows:

$ xcodebuild -version
Xcode 26.1
Build version 17B55

The reported version must be 26.0 or newer. Then you can validate that the Metal Toolchain is installed with:

$ xcodebuild -showComponent metalToolchain
Asset Path: /System/Library/AssetsV2/com_apple_MobileAsset_MetalToolchain/68d8db6212b48d387d071ff7b905df796658e713.asset/AssetData
Build Version: 17B54
Status: installed
Toolchain Identifier: com.apple.dt.toolchain.Metal.32023
Toolchain Search Path: /private/var/run/com.apple.security.cryptexd/mnt/com.apple.MobileAsset.MetalToolchain-v17.2.54.0.mDxgz0