What causes "The env directive must not be empty" in kovidgoyal/kitty?

Remove empty entries from the env list

The env directive must not be empty

Error message

The env directive must not be empty

What it means

ParseEnvInstruction parses an env VAR=value or copy/delete directive; after building the EnvInstruction it verifies that the key is non-empty. An empty directive (or one that reduces to an empty variable name) triggers this error.

Source

Thrown at kittens/ssh/config.go:163

}

func ParseEnvInstruction(spec string) (ans []*EnvInstruction, err error) {
	const COPY_FROM_LOCAL string = "_kitty_copy_env_var_"
	ei := &EnvInstruction{}
	found := false
	ei.key, ei.val, found = strings.Cut(spec, "=")
	ei.key = strings.TrimSpace(ei.key)
	if found {
		ei.val = strings.TrimSpace(ei.val)
		if ei.val == COPY_FROM_LOCAL {
			ei.val = ""
			ei.copy_from_local = true
		}
	} else {
		ei.delete_on_remote = true
	}
	if ei.key == "" {
		err = fmt.Errorf("The env directive must not be empty")
	}
	ans = []*EnvInstruction{ei}
	return
}

var paths_ctx *paths.Ctx

func resolve_file_spec(spec string, is_glob bool) ([]string, error) {
	if paths_ctx == nil {
		paths_ctx = &paths.Ctx{}
	}
	ans := os.ExpandEnv(paths_ctx.ExpandHome(spec))
	if !filepath.IsAbs(ans) {
		ans = paths_ctx.AbspathFromHome(ans)
	}
	if is_glob {
		files, err := doublestar.FilepathGlob(ans)
		if err != nil {

View on GitHub (pinned to 6d5d0c4406)

Solutions

Remove empty entries from the env list
Guard generators: skip env entries where strings.TrimSpace(entry) == ""
Validate the variable name is present before the '='

Example fix

// before
env: ["PATH=/usr/bin", ""]
// after
env: ["PATH=/usr/bin"]

Defensive patterns

Strategy: validation

Validate before calling

entries := slices.DeleteFunc(entries, func(e string) bool { return strings.TrimSpace(e) == "" })

Type guard

func isNonEmptyEnvEntry(e string) bool { return strings.TrimSpace(e) != "" && strings.SplitN(e, "=", 2)[0] != "" }

Prevention

Filter empty entries when generating env lists
Validate VAR names exist before '='

When it happens

Trigger: Passing 'env ' with an empty string, a directive like '=' with no variable name, or whitespace-only content after the env keyword.

Common situations: Trailing empty env entries from templating/loops generating config lines, or trailing whitespace creating an empty final entry after splitting.

Related errors

AI-assisted analysis of kovidgoyal/kitty@6d5d0c4406 (2026-08-27). Data as JSON: /api/errors/c7859332b8297522. Report an issue: GitHub.