What causes "brew-cask:{}: conflicts with installed cask {}" in jdx/mise?

Uninstall the conflicting cask named in the message — mise uninstall it if mise owns it, or brew uninstall --cask if brew does

jdx/mise · error

brew-cask: : conflicts with installed cask

Error message

brew-cask:{}: conflicts with installed cask {}

What it means

install_one_with_ancestors (src/system/packages/brew/cask.rs:451) honors the cask's conflicts_with.cask stanza from its API metadata: for each declared conflicting cask token it checks installed_versions, and if any is already installed the install aborts rather than overwrite an app the conflict declaration exists to protect.

Solutions

Uninstall the conflicting cask named in the message — mise uninstall it if mise owns it, or brew uninstall --cask <name> if brew does
Confirm the conflict by reading the cask's conflicts_with stanza in its api/cask/<token>.json
If the conflict is stale (the app was removed by hand), clean up leftover receipts so installed_versions stops detecting it, then retry

Defensive patterns

Strategy: validation

Validate before calling

# inspect the cask's declared conflicts before installing
curl -s "https://formulae.brew.sh/api/cask/firefox.json" | jq -r '.conflicts_with.cask[]?'

Prevention

Check a cask's conflicts_with stanza before requesting it on shared images
Remove the competing app before switching between conflicting casks
Keep install receipts clean so stale conflicts are not detected after manual removals

When it happens

Trigger: Installing a cask whose JSON declares conflicts_with.cask entries while one of those tokens is installed on the machine — typical for apps that install the same kernel extensions, privileged helpers, or system handlers (two VPN clients, two virtualization tools, competing browsers registering defaults).

Common situations: Switching between competing apps that hook the same OS integration; corporate images that pre-install one side of a conflicting pair; reinstalling after switching managers without removing the competitor first.

Related errors

AI-assisted analysis of jdx/mise@6f52dcdf99 (2026-08-22). Data as JSON: /api/errors/93ed5926fe1a9d28. Report an issue: GitHub.

Appendix: source

Thrown at src/system/packages/brew/cask.rs:451

        ancestors.insert(cask.token.clone());
        let artifacts = cask_artifacts(&cask)?;
        validate_platform_support(&cask, &artifacts)?;
        if homebrew_metadata_present(&cask.token) {
            bail!(
                "brew-cask:{}: Homebrew owns this cask; remove it with Homebrew before installing it with mise",
                cask.token
            );
        }
        let installed_version = installed_cask_version(&cask, &artifacts)?;
        if let Some(version) = installed_version.as_ref()
            && (cask.auto_updates || version == &cask.version)
        {
            info!("brew-cask:{}: already installed", cask.token);
            return Ok(version.clone());
        }
        for conflict in &cask.conflicts_with.cask {
            if !installed_versions(conflict).is_empty() {
                bail!(
                    "brew-cask:{}: conflicts with installed cask {}",
                    cask.token,
                    conflict
                );
            }
        }
        if !cask.depends_on.formula.is_empty() {
            let dependencies = cask
                .depends_on
                .formula
                .iter()
                .map(|name| PackageRequest {
                    name: name.clone(),
                    version: None,
                    tap_url: None,
                })
                .collect::<Vec<_>>();
            super::BrewManager::new()

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