Timeout resolving WebSocket URL from ${versionUrl} (10s)

Error message

Timeout resolving WebSocket URL from ${versionUrl} (10s)

What it means

resolveCdpWebSocketUrl enforces a 10-second timeout on the CDP version fetch using AbortController. When fetch aborts (AbortError), the library rethrows it as this clearer timeout error. It means the CDP endpoint did not respond within 10 seconds.

Source

Thrown at browser/firecrawl/src/resolve-cdp.ts:39

    try {
      const response = await fetch(versionUrl, { signal: controller.signal });

      if (!response.ok) {
        throw new Error(
          `Failed to fetch CDP version info from ${versionUrl}: ${response.status} ${response.statusText}`,
        );
      }

      const data = (await response.json()) as { webSocketDebuggerUrl?: string };
      if (!data.webSocketDebuggerUrl) {
        throw new Error(`No webSocketDebuggerUrl found in CDP version response from ${versionUrl}`);
      }

      logger?.debug?.(`Resolved WebSocket URL: ${data.webSocketDebuggerUrl}`);
      return data.webSocketDebuggerUrl;
    } catch (error) {
      if (error instanceof Error && error.name === 'AbortError') {
        throw new Error(`Timeout resolving WebSocket URL from ${versionUrl} (10s)`);
      }
      throw error;
    } finally {
      clearTimeout(timeoutId);
    }
  }

  return url;
}

View on GitHub (pinned to 75dd419e61)

Solutions

Check network reachability of the versionUrl host/port (curl the URL)
Retry — transient latency or service slowness may resolve
Verify no firewall, VPN, or proxy is blocking the CDP endpoint
Check Firecrawl service status / recreate the browser session

Defensive patterns

Strategy: retry

Validate before calling

const ctrl = new AbortController();
const t = setTimeout(() => ctrl.abort(), 5000);
try { await fetch(versionUrl, { signal: ctrl.signal }); console.log('CDP reachable'); }
catch { console.error('CDP endpoint unreachable within 5s'); }
finally { clearTimeout(t); }

Try / catch

try {
  const browser = new FirecrawlBrowser(config);
} catch (e) {
  if (e instanceof Error && e.message.includes('Timeout resolving WebSocket URL')) {
    // bounded retry with backoff
    await retryWithBackoff(() => new FirecrawlBrowser(config), 3);
  } else throw e;
}

Prevention

Pre-flight the versionUrl with curl to confirm network reachability
Check firewall/VPN/proxy rules for the CDP host and port
Set alerts on Firecrawl service status if running in production
Fail fast with a clear startup error rather than hanging

When it happens

Trigger: Constructor or wsUrl call where the HTTP request to versionUrl hangs longer than 10 seconds — network black hole, unreachable host, TLS handshake stall, or overloaded remote browser service.

Common situations: Firewall/security group blocking the CDP port; DNS resolving but connection never completing; remote browser service outage; slow VPN or corporate proxy.

Understand the failure class

Timeouts: ETIMEDOUT, deadlines, and hung requests — what actually expires when a request times out.

Related errors

AI-assisted analysis of mastra-ai/mastra@75dd419e61 (2026-08-30). Data as JSON: /api/errors/4c01cc366b74e9c1. Report an issue: GitHub.