charmbracelet/crush · error

invalid value format: %s

Error message

invalid value format: %s

What it means

Thrown by shellVariableResolver.ResolveValue when the config value is exactly "$". This preserves a backward-compat contract: a lone "$" is treated as a malformed config value rather than a literal, even though the underlying shell parser would accept it, so configs relying on validation fail early.

Source

Thrown at internal/config/resolve.go:94

// ResolveValue resolves shell-style substitution anywhere in the string:
//
//   - $(command) for command substitution, with full quoting and nesting.
//   - $VAR and ${VAR} for environment variables.
//   - ${VAR:-default} / ${VAR:+alt} / ${VAR:?msg} for defaulting.
//
// Unset variables expand to the empty string by default, matching bash.
// Command-substitution failures are always a hard error. Required
// credentials should use ${VAR:?message} so a missing variable fails
// loudly at load time instead of quietly resolving to empty. Global
// strict mode is available via shell.NoUnset for callers that want the
// old nounset-on behaviour back.
func (r *shellVariableResolver) ResolveValue(value string) (string, error) {
	// Preserve the historical backward-compat contract: a lone "$" is a
	// malformed config value, not a legal literal. The underlying shell
	// parser would accept it as a literal; we reject it here so existing
	// configs that relied on this validation still fail early.
	if value == "$" {
		return "", fmt.Errorf("invalid value format: %s", value)
	}

	ctx, cancel := context.WithTimeout(context.Background(), resolveTimeout)
	defer cancel()

	out, err := r.expand(ctx, value, r.env.Env())
	if err != nil {
		return "", sanitizeResolveError(value, err)
	}
	return out, nil
}

// maxResolveErrBytes bounds the size of the inner error message surfaced
// from a resolution failure. Defense-in-depth on top of shell.ExpandValue's
// own stderr budget: a custom Expander injected via WithExpander, or any
// future non-shell error path, must still produce a user-safe message.
const maxResolveErrBytes = 512

View on GitHub (pinned to 7944b8e522)

Solutions

  1. Fix the config value to be a full variable reference, e.g. "${MY_API_KEY}" or "$MY_API_KEY" instead of "$".
  2. Remove the malformed value if it was unintentional.
  3. Set the intended environment variable so expansion succeeds after fixing the reference.
  4. If you truly need a literal dollar sign, escape/quote it per the shell config rules (e.g. "$$" or '\$' as supported).

Example fix

// before (crushrc)
api_key "$"
// after
api_key "${OPENAI_API_KEY}"
Defensive patterns

Strategy: validation

Validate before calling

func validValue(v string) error {
    if v == "$" { return errors.New("invalid value format: $") }
    return nil
}
// validate config values before writing them to crushrc

Try / catch

out, err := resolver.ResolveValue(val)
if err != nil && strings.HasPrefix(err.Error(), "invalid value format") {
    return fmt.Errorf("config value %q is malformed; use a full ${VAR} reference", val)
}

Prevention

When it happens

Trigger: Calling ResolveValue("$") — typically via ConfigStore.Resolve or during config value expansion — with a variable placeholder in crushrc/crush.json that is empty, e.g. `"${"`, `"$"`, or a truncated env var reference.

Common situations: Typo in a config variable reference ("$" with no name); a shell script generating the config produced an empty variable; copy-paste truncation of "${API_KEY}".

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

AI-assisted analysis of charmbracelet/crush@7944b8e522 (2026-08-29). Data as JSON: /api/errors/d392a47aa77f644f. Report an issue: GitHub.