failed to convert output from UTF16 when running command %v,

Error message

failed to convert output from UTF16 when running command %v, err: %w

What it means

RunUTF16leCommand runs a command (typically Windows wsl.exe, which emits UTF-16LE output) and converts the combined output from UTF-16LE to a Go string; this error wraps the conversion failure from strutil.FromUTF16leToString. It indicates the command's output was not valid UTF-16LE, so it cannot be decoded.

Source

Thrown at pkg/executil/command.go:49

	for _, f := range opts {
		if err := f(&o); err != nil {
			return "", err
		}
	}

	var cmd *exec.Cmd
	ctx := o.ctx
	if ctx == nil {
		ctx = context.Background()
	}
	cmd = exec.CommandContext(ctx, args[0], args[1:]...)

	outString := ""
	out, err := cmd.CombinedOutput()
	if out != nil {
		s, err := strutil.FromUTF16leToString(bytes.NewReader(out))
		if err != nil {
			return "", fmt.Errorf("failed to convert output from UTF16 when running command %v, err: %w", args, err)
		}
		outString = s
	}
	return outString, err
}

View on GitHub (pinned to dd909d0973)

Solutions

Inspect the wrapped conversion error to see the malformed byte issue
Run the underlying WSL command manually (e.g. `wsl.exe --status`) to inspect its raw output encoding
Ensure Windows console code page/locales are standard (chcp 65001) and wsl.exe is up to date (`wsl --update`)
Check that the command isn't failing and emitting non-UTF16 error text; handle err from cmd execution separately

Defensive patterns

Strategy: try-catch

Validate before calling

// verify wsl.exe is present and produces output before relying on it
if _, err := exec.LookPath("wsl.exe"); err != nil {
    return errors.New("wsl.exe not available")
}

Try / catch

out, err := executil.RunUTF16leCommand(ctx, args...)
if err != nil {
    if strings.Contains(err.Error(), "failed to convert output from UTF16") {
        // fall back to raw output / log for diagnosis
        log.Warnf("non-UTF16 output from wsl: %v", err)
    }
    return err
}

Prevention

Keep wsl.exe updated (wsl --update)
Avoid custom console code pages that alter output encoding
Handle command failures before decoding output
Test on target Windows locales

When it happens

Trigger: Calling RunUTF16leCommand (used by startVM, initVM, stopVM, unregisterVM, getWslStatus) when the executed command's output is not valid UTF-16LE — e.g. an odd byte count or malformed surrogate pairs in the combined output.

Common situations: wsl.exe emitting localized/odd-encoded output on some Windows configurations; the command writing binary or plain-ASCII error output instead of UTF-16; a corrupted or legacy code page in the Windows console.

Related errors

AI-assisted analysis of lima-vm/lima@dd909d0973 (2026-09-01). Data as JSON: /api/errors/b5f428226086fad9. Report an issue: GitHub.