What causes "rustup show profile failed for {}: {}" in jdx/mise?

Run `rustup show profile` manually and fix the underlying rustup error reported in stderr.

rustup show profile failed for {}: {}

Error message

rustup show profile failed for {}: {}

What it means

Before reading the default rustup profile, mise runs `rustup show profile` with rustup-specific env and requires the command to exit successfully. If the process exits non-zero, the error propagates rustup's trimmed stderr so the user can see why rustup failed (missing toolchain, broken install, corrupted settings).

Source

Thrown at src/plugins/core/rust.rs:273

                .map(String::from)
                .collect(),
        ))
    }

    /// Returns the profile rustup applies when an install omits `--profile`.
    fn rustup_default_profile(&self, tv: &ToolVersion, runtime: &RustRuntime) -> Result<String> {
        let args = vec!["show".to_string(), "profile".to_string()];
        let mut cmd = cmd(runtime.bin_dir.join(RUSTUP_BIN), args)
            .env("PATH", rustup_path_env(runtime)?)
            .stdout_capture()
            .stderr_capture()
            .unchecked();
        for (key, value) in rustup_env(&runtime.homes, &tv.version) {
            cmd = cmd.env(key, value);
        }
        let output = cmd.run()?;
        if !output.status.success() {
            bail!(
                "rustup show profile failed for {}: {}",
                tv.style(),
                String::from_utf8_lossy(&output.stderr).trim()
            );
        }
        let profile = String::from_utf8_lossy(&output.stdout).trim().to_string();
        if profile.is_empty() {
            bail!(
                "rustup show profile returned an empty profile for {}",
                tv.style()
            );
        }
        Ok(profile)
    }

    fn missing_components(
        &self,
        requested: &[String],

View on GitHub (pinned to afd2eddd3a)

Solutions

Run `rustup show profile` manually and fix the underlying rustup error reported in stderr.
Reinstall or repair rustup (`rustup self update`, or reinstall from rustup.rs).
Verify RUSTUP_HOME/CARGO_HOME point to a valid, readable rustup installation; unset conflicting overrides in mise config.
Ensure a default toolchain exists (`rustup toolchain install stable && rustup default stable`).

Example fix

// before: broken RUSTUP_HOME override in mise.toml
[env]
RUSTUP_HOME = "/nonexistent"
// after: remove the override or point at the real rustup home
[env]
# RUSTUP_HOME removed — use system default

Defensive patterns

Strategy: try-catch

Validate before calling

let ok = std::process::Command::new("rustup").args(["show", "profile"]).output().map(|o| o.status.success());
if !ok.unwrap_or(false) { eprintln!("rustup is broken or missing; run `rustup show profile` to diagnose"); }

Try / catch

match result {
    Err(e) if e.to_string().contains("rustup show profile failed") => {
        eprintln!("repair rustup first: {}", e);
        // run `rustup show profile` manually / reinstall rustup
    }
    ...
}

Prevention

Keep rustup up to date with `rustup self update`.
Avoid overriding RUSTUP_HOME/CARGO_HOME in mise [env] unless intentional.
Ensure a default toolchain is installed before using mise's rust plugin.
In CI, install rustup before running mise install for rust.

When it happens

Trigger: Called from is_install_satisfied or install_version_ via rustup_default_profile when `rustup show profile` exits non-zero: rustup not properly installed, RUSTUP_HOME corrupted, toolchain config unreadable, or rustup env (homes/version) pointing at a broken install.

Common situations: rustup partially uninstalled or home directory moved; RUSTUP_HOME/CARGO_HOME env conflicts; running inside a sandbox/CI container where rustup's settings.toml is missing or unwritable; a rustup update in progress.

Related errors

AI-assisted analysis of jdx/mise@afd2eddd3a (2026-09-09). Data as JSON: /api/errors/e66124b9311cb218. Report an issue: GitHub.