What causes "exec command failed: {}" in jdx/mise?

Run the failing command manually and fix why it exits non-zero (the stderr in the error shows the cause)

exec command failed: {}

Error message

exec command failed: {}

What it means

The Tera v1 template `exec` function runs a shell command as a subprocess and requires it to exit successfully; on a non-zero status mise bails with the command's stderr as the message. Template rendering thus fails whenever an embedded exec command fails.

Source

Thrown at src/tera.rs:1466

            .collect::<Vec<String>>();
        let mut env_no_shims = env.clone();
        if let Some(path_val) = env_no_shims.get(&*env::PATH_KEY).cloned() {
            env_no_shims.insert(env::PATH_KEY.to_string(), strip_shims_from_path(&path_val));
        }
        let run_once = || -> eyre::Result<String> {
            #[cfg(windows)]
            {
                if let Some(mut c) =
                    crate::path::cmd_verbatim_command(&shell[0], &shell[1..], command)
                {
                    c.env_clear();
                    c.envs(env_no_shims.iter());
                    if let Some(dir) = &dir {
                        c.current_dir(dir);
                    }
                    let out = c.output()?;
                    if !out.status.success() {
                        eyre::bail!(
                            "exec command failed: {}",
                            String::from_utf8_lossy(&out.stderr)
                        );
                    }
                    let mut s = String::from_utf8(out.stdout)?;
                    while s.ends_with('\n') || s.ends_with('\r') {
                        s.pop();
                    }
                    return Ok(s);
                }
            }
            let mut expr: duct::Expression = cmd(&shell[0], &shell_args).full_env(&env_no_shims);
            if let Some(dir) = &dir {
                expr = expr.dir(dir);
            }
            Ok(crate::inline_command::optimize_expression(
                expr,
                command,

View on GitHub (pinned to afd2eddd3a)

Solutions

Run the failing command manually and fix why it exits non-zero (the stderr in the error shows the cause)
Ensure the command is installed/on PATH for the mise environment (shims are stripped from exec env)
Check the `dir` argument of the exec call points to the intended working directory

Example fix

// before (template)
{{ exec(command="git rev-parse --verify HEAD^9") }}

// after
{{ exec(command="git rev-parse --verify HEAD~9 || echo unknown") }}

Defensive patterns

Strategy: try-catch

Validate before calling

// pre-check a command before embedding it in a template
const { status } = Bun.spawnSync(['git', 'rev-parse', 'HEAD']);
if (status !== 0) throw new Error('git not usable in mise exec environment');

Try / catch

// wrap template rendering that uses exec()
match render() {
    Err(e) if e.to_string().contains("exec command failed") => {
        eprintln!("template exec failed: {e:#}; check PATH/dir of embedded command");
    }
    Err(e) => return Err(e),
    Ok(v) => v,
}

Prevention

Remember exec strips mise shims from the environment — only real PATH tools run
Test template commands in a bare shell first
Give exec an explicit dir argument when the command depends on cwd
Make embedded commands defensive (|| echo fallback) when failure is tolerable

When it happens

Trigger: A mise.toml template uses `{{ exec(command="...") }}` (or parse_template/get_tera_v1 evaluates a template containing it) and the command exits non-zero — e.g. missing binary, failing script, or wrong cwd/dir argument.

Common situations: Referencing a command not installed in the environment the task runs in; a script that depends on files in the wrong working directory; environment differences (env_no_shims) hiding tools normally available via shims.

Related errors

AI-assisted analysis of jdx/mise@afd2eddd3a (2026-09-09). Data as JSON: /api/errors/a595903a8a319817. Report an issue: GitHub.