unexpected status code ${wptResponse.statusCode} ${wptRespon

Error message

unexpected status code ${wptResponse.statusCode} ${wptResponse.statusText}

What it means

Thrown by startWptTest() after parsing the WPT API JSON response when `statusCode` is not 200. WPT wraps its own status inside the JSON body (separate from HTTP status), so this fires when WPT itself rejects the test request — e.g. invalid key, quota exceeded, or bad parameters.

Source

Thrown at core/scripts/lantern/collect/collect.js:77

  const apiUrl = new URL('/runtest.php', WPT_URL);
  apiUrl.search = new URLSearchParams({
    k: WPT_KEY,
    f: 'json',
    url,
    location: 'gce-us-east4-linux:Chrome.3GFast',
    runs: '1',
    lighthouse: '1',
    mobile: '1',
    // Make the trace file available over /getgzip.php.
    lighthouseTrace: '1',
    lighthouseScreenshots: '1',
    // Disable some things that WPT does, such as a "repeat view" analysis.
    type: 'lighthouse',
  }).toString();
  const wptResponseJson = await fetchString(apiUrl.href);
  const wptResponse = JSON.parse(wptResponseJson);
  if (wptResponse.statusCode !== 200) {
    throw new Error(`unexpected status code ${wptResponse.statusCode} ${wptResponse.statusText}`);
  }

  return {
    testId: wptResponse.data.testId,
    jsonUrl: wptResponse.data.jsonUrl,
  };
}

/**
 * @param {string} url
 * @return {Promise<Result>}
 */
async function runUnthrottledLocally(url) {
  const artifactsFolder = `${LH_ROOT}/.tmp/collect-traces-artifacts`;
  const {stdout} = await execFileAsync('node', [
    `${LH_ROOT}/cli`,
    url,
    '--throttling-method=provided',

View on GitHub (pinned to 9515cd4e58)

Solutions

Check the wptResponse.statusText and statusCode in the error for WPT's specific rejection reason.
Verify WPT_KEY is valid and has remaining quota at webpagetest.org.
Confirm the location string (`gce-us-east4-linux:Chrome.3GFast`) and other params are still supported by the current WPT API.

Defensive patterns

Strategy: try-catch

Validate before calling

function assertWptStatus(wptResponse) {
  if (wptResponse.statusCode !== 200) {
    throw new Error(`WPT rejected test: ${wptResponse.statusCode} ${wptResponse.statusText}`);
  }
}

Try / catch

try {
  return await startWptTest(url);
} catch (e) {
  if (/unexpected status code/.test(e.message)) {
    console.error(`WPT test start failed: ${e.message}. Check WPT_KEY and quota.`);
  }
  throw e;
}

Prevention

Verify WPT_KEY is valid and has quota before starting tests.
Check WPT statusText for specific rejection reasons.
Keep the location string and parameters in sync with the current WPT API.

When it happens

Trigger: Calling the WPT `/runtest.php` endpoint with an invalid/expired WPT_KEY, exceeded test quota, unsupported location, or malformed test parameters.

Common situations: Expired WPT key; daily/monthly test quota exhausted; WPT location string changed; parameter format changed in a WPT API update.

Related errors

AI-assisted analysis of GoogleChrome/lighthouse@9515cd4e58 (2026-08-13). Data as JSON: /api/errors/51944abac7e7d257. Report an issue: GitHub.