[macos-26] installing imagemagick or graphicsmagick using homebrew fails

[mhyassin]

Summary

We’re seeing a new failure on GitHub-hosted macOS runners when installing ImageMagick via Homebrew.

This started for us on April 10, 2026. The same workflow previously passed, and the failure now reproduces on both:

• macos-26
• macos-26-xlarge

Why this looks like a runner-image regression

• libheif itself was not newly updated when this started happening for us.
• The failure began suddenly in CI on April 10, 2026.
• It reproduces across both macos-26 and macos-26-xlarge.
• Our workflow behavior did not materially change in the install step.

This suggests a change in the GitHub-hosted macOS runner image and/or bundled Homebrew environment.

Environment

• GitHub Actions hosted runner
• Runner labels tested:
  • macos-26
  • macos-26-xlarge
• Xcode version in our workflow: 26.3
• Homebrew installs libheif--1.21.2.arm64_tahoe.bottle.tar.gz

Workaround

We can work around it by tolerating that specific post-install warning if magick and gs are actually present afterward, but that is only a mitigation on our side.

Request

Can you confirm whether there is a known regression in the current macOS 26 runner image or Homebrew environment affecting libheif post-install / update-mime-database?

Platforms affected

• Azure DevOps
• GitHub Actions - Standard Runners
• GitHub Actions - Larger Runners

Runner images affected

• Ubuntu 22.04
• Ubuntu 24.04
• Ubuntu Slim
• macOS 14
• macOS 14 Arm64
• macOS 15
• macOS 15 Arm64
• macOS 26
• macOS 26 Arm64
• Windows Server 2022
• Windows Server 2025
• Windows Server 2025 with Visual Studio 2026

Image version and build link

Version: 20260408.0337.1

Last successful build was on April 9th using Version: 20260402.0322.1

Is it regression?

Version: 20260402.0322.1

Expected behavior

can install ImageMagick on GitHub runners

Actual behavior

brew install exits with code 1 during dependency installation, even though the packages appear to be mostly installed.

Relevant log section:

==> Installing imagemagick dependency: libheif
==> Pouring libheif--1.21.2.arm64_tahoe.bottle.tar.gz
==> /opt/homebrew/opt/shared-mime-info/bin/update-mime-database /opt/homebrew/share/mime
Last 15 lines from /Users/runner/Library/Logs/Homebrew/libheif/post_install.01.update-mime-database.log:
2026-04-10 21:42:21 +0000

/opt/homebrew/opt/shared-mime-info/bin/update-mime-database
/opt/homebrew/share/mime

Warning: The post-install step did not complete successfully
You can try again using:
  brew postinstall libheif
...
Error: Process completed with exit code 1.

The issue appears related to the libheif dependency post-install step, specifically update-mime-database.

Repro steps

The failing step is:

- name: Install Imagemagick
  run: |
    brew install imagemagick
    brew install ghostscript

We also reproduced it with:

brew install imagemagick ghostscript