GoogleChrome/lighthouse · error · Error

`lighthouse:default` is the only valid extension method.

Error message

`lighthouse:default` is the only valid extension method.

What it means

Thrown by resolveExtensions in config.js. A config may declare 'extends' to build on the default Lighthouse config, but the only accepted value is the string 'lighthouse:default'. Any other extends value is unsupported and throws. Lighthouse does not support arbitrary multi-config inheritance chains.

Source

Thrown at core/config/config.js:86

  // The directory of the config path, if one was provided.
  const configDir = configPath ? path.dirname(configPath) : undefined;

  return {
    configWorkingCopy: deepCloneConfigJson(config),
    configPath,
    configDir,
  };
}

/**
 * @param {LH.Config} config
 * @return {LH.Config}
 */
function resolveExtensions(config) {
  if (!config.extends) return config;

  if (config.extends !== 'lighthouse:default') {
    throw new Error('`lighthouse:default` is the only valid extension method.');
  }

  const {artifacts, ...extensionJSON} = config;
  const defaultClone = deepCloneConfigJson(defaultConfig);
  const mergedConfig = mergeConfigFragment(defaultClone, extensionJSON);

  mergedConfig.artifacts = mergeConfigFragmentArrayByKey(
    defaultClone.artifacts,
    artifacts,
    artifact => artifact.id
  );

  return mergedConfig;
}

/**
 * Looks up the required artifact IDs for each dependency, throwing if no earlier artifact satisfies the dependency.
 *

View on GitHub (pinned to 9515cd4e58)

Solutions

1. Set extends: 'lighthouse:default' (the only supported value) and override individual keys.
2. If you need another preset as a base, import that preset object and spread/merge it yourself instead of using extends.
3. Remove the extends key if you are providing a fully standalone config.

Example fix

// before
module.exports = {extends: 'lighthouse:full', audits: [...]};
// after
module.exports = {extends: 'lighthouse:default', audits: [...]};

if (config.extends !== undefined && config.extends !== 'lighthouse:default') {
  throw new Error("config.extends may only be 'lighthouse:default'");
}

function extendsIsValid(v) { return v === undefined || v === 'lighthouse:default'; }

try { const cfg = new Config(config, {configPath}); }
catch (e) { if (/only valid extension method/.test(e.message)) config.extends = 'lighthouse:default'; throw e; }

When it happens

Trigger: A custom config sets extends: 'lighthouse:full' or extends: './other-config.js' or extends: 'lighthouse:desktop'. resolveExtensions sees a non-matching value and config.js:86 throws.

Common situations: Assuming other preset names (e.g. 'lighthouse:full','lighthouse:perf') are valid extends targets. Trying to extend a local config file. Outdated docs suggesting extends values that were never supported.

Related errors

• ${pluginName} has an invalid category description.
• ${pluginName} has an invalid category manualDescription.
• ${pluginName} supportedModes must be an array, valid array v
• ${pluginName} groups json is not defined as an object.
• ${pluginName} has a group not defined as an object.

AI-assisted analysis of GoogleChrome/lighthouse@9515cd4e58 (2026-08-13). Data as JSON: /api/errors/6666374a513aa68c. Report an issue: GitHub.