jdx/mise · error

brew-cask:{}: only font-only casks without lifecycle hooks a

Error message

brew-cask:{}: only font-only casks without lifecycle hooks are supported on linux

What it means

On Linux, this implementation only supports brew casks that consist solely of font artifacts and declare no preflight/postflight lifecycle hooks (neither structured steps nor Ruby hooks). validate_platform_support bails for anything else, because installing app bundles or running brew's shell lifecycle scripts is not supported outside macOS.

Source

Thrown at src/system/packages/brew/cask/artifacts.rs:106

pub(super) fn validate_platform_support(cask: &Cask, artifacts: &CaskArtifacts) -> Result<()> {
    #[cfg(target_os = "linux")]
    {
        let font_only = !artifacts.fonts.is_empty()
            && artifacts.apps.is_empty()
            && artifacts.binaries.is_empty()
            && artifacts.command_wrappers.is_empty()
            && artifacts.pkgs.is_empty()
            && artifacts.installers.is_empty()
            && artifacts.generic.is_empty()
            && artifacts.completions.is_empty()
            && artifacts.generated_completions.is_empty()
            && artifacts.preflight_steps.is_empty()
            && artifacts.postflight_steps.is_empty()
            && !has_lifecycle_hook(cask, "preflight")
            && !has_lifecycle_hook(cask, "postflight");
        if !font_only {
            bail!(
                "brew-cask:{}: only font-only casks without lifecycle hooks are supported on linux",
                cask.token
            );
        }
    }
    #[cfg(not(target_os = "linux"))]
    let _ = (cask, artifacts);
    Ok(())
}

pub(super) fn platform_unavailable_state(
    cask: &Cask,
    artifacts: &CaskArtifacts,
) -> Option<PackageState> {
    validate_platform_support(cask, artifacts)
        .err()
        .map(|err| PackageState::unavailable(err.to_string()))
}

View on GitHub (pinned to afd2eddd3a)

Solutions

1. Install the software via a native Linux channel instead: the brew formula (not cask), apt/dnf package, or a mise-supported backend (aqua:, github:, etc.).
2. If the cask bundles fonts plus other artifacts, extract just the fonts manually or ask upstream for a fonts-only cask.
3. Run the installation on a macOS machine; this restriction only applies to target_os = "linux".
4. If it's your own cask, split fonts into a dedicated cask without preflight/postflight hooks so Linux installs succeed.

Example fix

// before: one cask mixing app + font with hooks
cask "myfont" do
  app "MyApp.app"
  font "MyFont.ttf"
  preflight do
    system_command "/usr/bin/touch", args: ["/tmp/x"]
  end
end
// after: fonts-only cask, no hooks
cask "myfont" do
  font "MyFont.ttf"
end

import platform
if platform.system() == "Linux" and not cask_is_font_only(cask_token):
    raise Skip(f"{cask_token}: non-font cask unsupported on linux")

match validate_platform_support(&cask, &artifacts) {
    Err(e) if e.to_string().contains("only font-only casks") => {
        eprintln!("{}: install via formula/apt/github backend instead", cask.token);
        fallback_native_install(&cask.token)?;
    }
    other => other?,
}

When it happens

Trigger: Calling install_one_with_ancestors or platform_unavailable_state on Linux for a cask that has any non-font install artifact (app, pkg, binary, generic, etc.) or defines preflight/postflight steps or Ruby lifecycle hooks — e.g. linux_supports_font_only_casks / linux_rejects_non_font_casks test cases.

Common situations: Trying to install a macOS application cask (browser, editor, CLI wrapped in .app) from a Linux machine using mise's brew backend; casks whose fonts are accompanied by installer scripts; CI on Linux runners attempting macOS cask installs.

Understand the failure class

Background: "unsupported platform" / "not supported on this platform" errors: what they mean and how to fix them — this error's family across 47 libraries.

Related errors

• brew-cask:{}: only font-only casks without lifecycle hooks a
• GitHub relay requires Linux or macOS
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• unsupported OS version: {os_ver}
• swift does not publish musl builds

AI-assisted analysis of jdx/mise@afd2eddd3a (2026-09-09). Data as JSON: /api/errors/60f2827de7a4e9a3. Report an issue: GitHub.