bootstrap_command returned an unsafe mise path

Error message

bootstrap_command returned an unsafe mise path: {command:?}

What it means

mise runs a bootstrap command on a remote host to locate where mise was installed. Before using the returned string, `validated_remote_command` requires it to be an absolute path containing no NUL, newline, or carriage-return bytes; otherwise this error is thrown to prevent injecting arbitrary shell content or relative/truncated paths into remote shell commands.

Solutions

Fix the remote bootstrap_command so it prints exactly one absolute path and nothing else (e.g. suppress rc-file output, use `command -v mise` with stderr redirected)
Ensure mise is installed on the remote at a real absolute path (not an alias or shell function)
Check for a broken remote helper/ssh wrapper emitting CR/LF or NUL bytes and fix its output encoding

Example fix

// before
bootstrap_command = "mise which mise"  // prints relative or extra lines
// after
bootstrap_command = "command -v mise 2>/dev/null"  // single absolute path, stderr silenced

Defensive patterns

Strategy: validation

Validate before calling

function isSafeRemotePath(s) {
  return typeof s === 'string' && s.startsWith('/') && !/[\0\n\r]/.test(s);
}
if (!isSafeRemotePath(output)) throw new Error('bootstrap output is not a safe absolute path');

Type guard

const isSafeRemotePath = (s: unknown): s is string =>
  typeof s === 'string' && s.startsWith('/') && !/[\0\n\r]/.test(s);

Try / catch

try {
  let path = validated_remote_command(output);
} catch (e) {
  if (String(e).includes('unsafe mise path')) {
    // inspect raw remote output, fix bootstrap_command, then retry
  } else throw e;
}

Prevention

Make bootstrap_command print exactly one absolute path to stdout and nothing else
Send all diagnostics to stderr, never stdout
Test the bootstrap command over plain ssh before wiring it into config
Avoid relying on shell aliases/functions; use `command -v mise`

When it happens

Trigger: The remote `bootstrap_command` (e.g. `which mise`, `command -v mise`, or a custom script) prints a relative path, a multiline/annotated string (shell init output, MOTD text, aliases), or a path containing NUL/CR/LF.

Common situations: Custom bootstrap_command in remote.toml that echoes extra lines; remote shell rc-files printing banners before `which`; mise installed via an alias rather than a real path; NUL-corrupted output from a broken remote helper.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

AI-assisted analysis of jdx/mise@533346cc37 (2026-09-17). Data as JSON: /api/errors/befd664e7e1095aa. Report an issue: GitHub.

Appendix: source

Thrown at src/system/remote.rs:2196

    if value.is_empty() || value.contains('\0') {
        bail!("remote {kind} cannot be empty or contain NUL");
    }
    Ok(())
}

fn validate_staging_path(path: &str) -> Result<()> {
    if !path.starts_with("/tmp/mise-bootstrap.")
        || path["/tmp/mise-bootstrap.".len()..].is_empty()
        || path.chars().any(char::is_whitespace)
    {
        bail!("remote mktemp returned an unsafe staging path: {path:?}");
    }
    Ok(())
}

fn validated_remote_command(command: &str) -> Result<String> {
    if !command.starts_with('/') || command.contains(['\0', '\n', '\r']) {
        bail!("bootstrap_command returned an unsafe mise path: {command:?}");
    }
    Ok(command.to_string())
}

fn validated_remote_command_output(output: &str) -> Result<String> {
    validated_remote_command(output.strip_suffix('\n').unwrap_or(output))
}

fn validated_absolute_remote_path_output(output: &str, kind: &str) -> Result<String> {
    let path = output.strip_suffix('\n').unwrap_or(output);
    if !path.starts_with('/') || path.contains(['\0', '\n', '\r']) {
        bail!("{kind} returned an unsafe absolute path: {path:?}");
    }
    Ok(path.to_string())
}

fn validate_install_mise_path(path: &str) -> Result<()> {
    validate_value("mise install path", path)?;

View on GitHub (pinned to 533346cc37)