different-ai/openwork · error · Error

Could not resolve built-in browser CDP target.

Error message

Could not resolve built-in browser CDP target.

What it means

resolveBrowserCdpTargetId polls the app's CDP target list for a target whose URL contains the built-in browser tab's marker URL, up to a fixed timeout. If no matching target appears before the polling loop exhausts, it throws this error, meaning the automation layer cannot attach to the built-in browser view via Chrome DevTools Protocol.

Source

Thrown at apps/desktop/electron/browser-panel.mjs:147

    const targets = await response.json();
    return Array.isArray(targets) ? targets : [];
  }

  async function resolveBrowserCdpTargetId(tabId) {
    const marker = encodeURIComponent(`openwork-browser-tab:${tabId}`);
    const deadline = Date.now() + BROWSER_TARGET_RESOLVE_TIMEOUT_MS;
    while (Date.now() < deadline) {
      const targets = await listCdpTargets().catch(() => []);
      const target = targets.find((candidate) => (
        candidate?.type === "page" &&
        typeof candidate.id === "string" &&
        typeof candidate.url === "string" &&
        candidate.url.includes(marker)
      ));
      if (target?.id) return target.id;
      await new Promise((resolve) => setTimeout(resolve, BROWSER_TARGET_RESOLVE_INTERVAL_MS));
    }
    throw new Error("Could not resolve built-in browser CDP target.");
  }

  async function openBrowserUrlForAutomation(rawUrl, provider = "auto") {
    const requestedProvider = String(provider || "auto").trim().toLowerCase();
    if (requestedProvider && requestedProvider !== "auto" && requestedProvider !== "builtin") {
      throw new Error(`Browser provider is not available yet: ${requestedProvider}`);
    }
    const url = normalizeBrowserUrl(rawUrl);
    const tab = createBrowserTab("about:blank", { select: true });
    await tab.view.webContents.loadURL(browserTargetMarkerUrl(tab.tabId));
    const targetId = await resolveBrowserCdpTargetId(tab.tabId);
    await tab.view.webContents.loadURL(url);
    return {
      provider: "builtin",
      browser_url: cdpBrowserUrl(),
      target_id: targetId,
      tab_id: tab.tabId,
      url,

View on GitHub (pinned to 2b7df46e8a)

Solutions

1. Retry the automation call — the target may register shortly after the timeout
2. Check that the built-in browser tab still exists and its webContents loaded the marker URL successfully
3. Ensure CDP/debugging is available for the Electron session (no flags disabling remote debugging)
4. Increase BROWSER_TARGET_RESOLVE_INTERVAL_MS / poll attempts if targets register slowly on the target hardware

Example fix

// before
const targetId = await resolveBrowserCdpTargetId(tab.tabId);
// after
let targetId;
try { targetId = await resolveBrowserCdpTargetId(tab.tabId); }
catch { await tab.view.webContents.loadURL(browserTargetMarkerUrl(tab.tabId)); targetId = await resolveBrowserCdpTargetId(tab.tabId); }

const tabs = listBrowserTabs();
if (!tabs.some(t => String(t.tabId) === String(tabId))) throw new Error(`tab ${tabId} is not open`);

function isResolvedTargetId(v) { return typeof v === 'string' && v.length > 0; }

try {
  const targetId = await resolveBrowserCdpTargetId(tabId);
} catch (e) {
  if (e.message.includes('Could not resolve built-in browser CDP target')) {
    // wait and retry once, or surface a 'browser not ready' state
  } else throw e;
}

When it happens

Trigger: Calling openBrowserUrlForAutomation (or resolveBrowserCdpTargetId directly) when the WebContentsView for the tab has not finished creating/registered a CDP target with the marker URL in browserTargetMarkerUrl(tabId), or the polling interval x attempts elapses before the target appears.

Common situations: Slow machine or heavy load delaying target registration; the built-in browser view failed to attach to CDP; Electron/CDP debugging not enabled for that session; navigating away from the marker page before the target resolves; a race where the tab was closed mid-resolution.

Related errors

• CDP target list failed: HTTP ${response.status}
• Agent context diagnostics timeout must be between 1 ms and 3
• Electron desktop helper is unavailable: ${command}
• Electron desktop helper is unavailable: ${prop}
• Failed to open browser

AI-assisted analysis of different-ai/openwork@2b7df46e8a (2026-09-01). Data as JSON: /api/errors/50922cd2329e91c1. Report an issue: GitHub.