What causes "${key} expects a "${defaultType}" value!" in withastro/astro?

Look up the key and its expected type: `astro preferences list` shows keys and defaults

withastro/astro · error · Error

expects a " " value!

Error message

${key} expects a "${defaultType}" value!

What it means

`astro preferences set <key> <value>` type-checks the coerced value against the type of the key's default in DEFAULT_PREFERENCES. CLI arguments arrive as strings; `coerce(key, value)` converts them (e.g. 'true' -> true for boolean keys). If the coerced result's typeof still does not match the default's typeof, the set is rejected before anything is persisted.

Solutions

Look up the key and its expected type: `astro preferences list` shows keys and defaults
Pass a value of the matching type: `astro preferences set devToolbar.enabled true` (booleans) or `astro preferences set telemetry.enabled false`
Quote multi-word values properly and make sure you are not accidentally passing a flag as the value

Example fix

# before
astro preferences set devToolbar.enabled maybe   # devToolbar.enabled expects a "boolean" value!

# after
astro preferences set devToolbar.enabled true

Defensive patterns

Strategy: validation

Validate before calling

// inspect the key's default type before setting it
import { execSync } from 'node:child_process';

function expectedType(key) {
  const listing = execSync('astro preferences list', { encoding: 'utf8' });
  const row = listing.split('\n').find((l) => l.includes(key));
  return /true|false/.test(row) ? 'boolean' : 'string';
}

if (typeof value !== expectedType(key)) {
  // coerce or reject before calling `astro preferences set`
}

Prevention

Run `astro preferences list` once to learn each key's type before scripting `set` commands
Pass booleans as the literals true/false and numbers unparsed — never free text
Quote shell arguments so values with spaces are not split into extra positionals

When it happens

Trigger: `astro preferences set devToolbar.enabled maybe` (boolean key, uncoercible string); setting a numeric key to non-numeric text; passing extra positional tokens so the wrong value lands in `value`.

Common situations: Passing free-text where a boolean/number is expected, quoting mistakes that empty the value, wrong key names whose defaults have a different type than assumed, scripted calls forwarding flags as values.

Related errors

AI-assisted analysis of withastro/astro@e294953aa8 (2026-08-18). Data as JSON: /api/errors/1ac00b4412786c65. Report an issue: GitHub.

Appendix: source

Thrown at packages/astro/src/cli/preferences/index.ts:168

			return 0;
		}
		logger.info('SKIP_FORMAT', msg.preferenceGet(key, value));
		return 0;
	} catch {}
	return 1;
}

async function setPreference(
	settings: AstroSettings,
	logger: AstroLogger,
	key: PreferenceKey,
	value: unknown,
	{ location }: SubcommandOptions,
) {
	try {
		const defaultType = typeof dlv(DEFAULT_PREFERENCES, key);
		if (typeof coerce(key, value) !== defaultType) {
			throw new Error(`${key} expects a "${defaultType}" value!`);
		}

		await settings.preferences.set(key, coerce(key, value), { location });
		logger.info('SKIP_FORMAT', msg.preferenceSet(key, value));
		return 0;
	} catch (e) {
		if (e instanceof Error) {
			logger.error('preferences', msg.formatErrorMessage(collectErrorMetadata(e), true));
			return 1;
		}
		throw e;
	}
}

async function enablePreference(
	settings: AstroSettings,
	logger: AstroLogger,
	key: PreferenceKey,

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