Description

PSchmiedmayer

opened on Jun 26, 2026

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Description

Swift/iOS builds fail after github/codeql-action/init with Xcode 26 on macOS 26 GitHub-hosted runners when the build needs the Metal toolchain.

The failing build error is:

error: error: cannot execute tool 'metal' due to missing Metal Toolchain; use: xcodebuild -downloadComponent MetalToolchain
Command CompileMetalFile failed with a nonzero exit code

This was originally discussed in actions/runner-images:

• Runner-images issue: Metal Toolchain on macOS 26 Runners with Xcode 26 actions/runner-images#13014
• Maintainer repro: xcrun metal -v works after Xcode selection, then fails after codeql-action/init: Metal Toolchain on macOS 26 Runners with Xcode 26 actions/runner-images#13014 (comment)
• See comment by @v-sergei-pyshnoi , pointing to an issue here: Metal Toolchain on macOS 26 Runners with Xcode 26 actions/runner-images#13014 (comment)

Reproduction outline

jobs:
  codeql-metal-repro:
    runs-on: macos-26
    permissions:
      contents: read
      security-events: write
    steps:
      - uses: actions/checkout@v4
      - name: Select Xcode
        uses: maxim-lobanov/setup-xcode@v1
        with:
          xcode-version: latest-stable
      - name: Check Metal before CodeQL init
        run: |
          xcodebuild -version
          xcrun --find metal
          xcrun metal -v
      - name: Initialize CodeQL
        uses: github/codeql-action/init@v4
        with:
          languages: swift
          build-mode: manual
      - name: Check Metal after CodeQL init
        run: |
          xcrun --find metal
          xcrun metal -v
      - name: Build
        run: |
          # Run the normal xcodebuild command for an iOS app target that compiles Metal files.
          xcodebuild ...

Expected: xcrun metal -v and the xcodebuild invocation continue to find the selected Xcode’s Metal toolchain after CodeQL initialization.

Actual: after codeql-action/init, xcrun metal -v / CompileMetalFile can fail with “missing Metal Toolchain”, even though the runner image appears to have the toolchain available before CodeQL initialization.

Note: Xcode 26 changed Metal Toolchain distribution/visibility, and MacPorts documented extra steps sometimes needed to make the toolchain visible to all users:
https://trac.macports.org/wiki/TahoeProblems#MetaltoolchainisnolongerbundledinXcode

Reacted by Jozef Izso

Activity

1. mbg commented on Jun 26, 2026

   

   mbg

   on Jun 26, 2026

   Member

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   Hi @PSchmiedmayer 👋🏻

   Thanks for opening this issue. My first thought here is that this could be a Rosetta issue. One of the things that the codeql-action/init step does is to initialise the CodeQL tracer which injects itself into certain processes to observe how the project is built. This does not natively support ARM-based architectures, and so runs through Rosetta on macOS. Subsequently, all processes it intercepted then also run under Rosetta. My hypothesis would therefore be that in the example run, Metal is installed for the ARM-based host, but not for the Intel-based process tree that runs after the CodeQL tracer intercepted the command.

   I'll pass this on to the team that looks after Swift support in CodeQL who'll know best and whether there's anything we can do on our end to address this.

   Reacted by Paul Schmiedmayer
2. PSchmiedmayer commented on Jun 26, 2026

   

   PSchmiedmayer

   on Jun 26, 2026

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   Thank you @mbg for the quick response; greatly appreciated and thank you for looking into this!
3. jketema commented on Jun 29, 2026

   

   jketema

   on Jun 29, 2026

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   I investigated this in the context of actions/runner-images#13014, and this also failed on macOS Intel runners, so this is not Rosetta related.

   Currently this fails for me already in the "Check Metal before CodeQL init" step, so it looks like there a regression in the runner images which would need be be resolved first.
4. PSchmiedmayer commented on Jul 1, 2026

   

   PSchmiedmayer

   on Jul 1, 2026

   Author

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   Thanks @jketema; that's unfortunate, I will report that back to the main issue over in actions/runner-images#13014.
5. fzlzjerry

   added a commit that references this issue on Oct 31, 2026

   ci(codeql): leave the Metal sources out of the traced Swift build

   5a56062

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