What causes "expected boolean found %T for %s" in cloudflare/cloudflared?

Edit the config file so the value is an unquoted YAML boolean: `flag: true`

expected boolean found %T for %s

Error message

expected boolean found %T for %s

What it means

configFileSettings.Bool reads a named setting from the YAML config file and expects a Go bool (YAML true/false). If the key exists but holds any other type (string "true", int 1, etc.), cloudflared returns `expected boolean found %T` naming the actual type. Boolean flags set in the config file must be real YAML booleans, not quoted strings.

Source

Thrown at config/configuration.go:370

		}
		if v, ok := raw.([]int); ok {
			return v, nil
		}
		return nil, fmt.Errorf("expected int slice found %T for %s", raw, name)
	}
	return nil, nil
}

func (c *configFileSettings) Generic(name string) (cli.Generic, error) {
	return nil, errors.New("option type Generic not supported")
}

func (c *configFileSettings) Bool(name string) (bool, error) {
	if raw, ok := c.Settings[name]; ok {
		if v, ok := raw.(bool); ok {
			return v, nil
		}
		return false, fmt.Errorf("expected boolean found %T for %s", raw, name)
	}
	return false, nil
}

var configuration configFileSettings

func GetConfiguration() *Configuration {
	return &configuration.Configuration
}

// ReadConfigFile returns InputSourceContext initialized from the configuration file.
// On repeat calls returns with the same file, returns without reading the file again; however,
// if value of "config" flag changes, will read the new config file
func ReadConfigFile(c *cli.Context, log *zerolog.Logger) (settings *configFileSettings, warnings string, err error) {
	configFile := c.String("config")
	if configuration.Source() == configFile || configFile == "" {
		if configuration.Source() == "" {
			return nil, "", ErrNoConfigFile

View on GitHub (pinned to 2253eeeb25)

Solutions

Edit the config file so the value is an unquoted YAML boolean: `flag: true`
Remove quotes around true/false values
If the value came from environment substitution, ensure the substituted text is bare true/false
Re-run cloudflared with the fixed config file

Example fix

# before (config.yml)
hello-world: "true"
# after
hello-world: true

Defensive patterns

Strategy: validation

Validate before calling

raw, ok := cfg["boolFlag"]
if ok { if _, isBool := raw.(bool); !isBool { return fmt.Errorf("boolFlag must be bare true/false, got %T", raw) } }

Type guard

func isYAMLBool(v interface{}) bool { _, ok := v.(bool); return ok }

Prevention

Use bare true/false (no quotes) for boolean flags in config.yml
Avoid injecting boolean values via env substitution that could quote them
Don't copy CLI --flag=true syntax into YAML

When it happens

Trigger: A boolean flag (e.g. `hello-world: true`, `url: ...` style toggles) is present in c.Settings but its value is a string like "true", a number, or a nested map, when the CLI bool accessor is called during config resolution.

Common situations: Writing `flag: "true"` (quoted) in config.yml, using `flag: yes` with a YAML parser configured oddly, or copying CLI-style `--flag=true` text into the config file.

Related errors

AI-assisted analysis of cloudflare/cloudflared@2253eeeb25 (2026-09-06). Data as JSON: /api/errors/ad8bccf636ec45cd. Report an issue: GitHub.