grafana/k6 · error

creating a new %s: %w

Error message

creating a new %s: %w

What it means

Returned by Browser.onAttachedToTarget when NewPage fails for an incoming target (the '%s' is the target type, e.g. 'page' or 'background_page') and the error is not an ignorable page-attachment failure (browser closing races are ignored separately). This error is delivered asynchronously: initEvents' event loop handles it via k6ext.Panicf('browser is attaching to target: ...'), which aborts the VU iteration. It usually means a page/iframe target appeared while the CDP session or context was in a bad state.

Source

Thrown at internal/js/modules/k6/browser/common/browser.go:330

	)
	// Opener is nil for the initial page.
	if isPage {
		b.pagesMu.RLock()
		if t, ok := b.pages[targetPage.OpenerID]; ok {
			opener = t
		}
		b.pagesMu.RUnlock()
	}
	p, err := NewPage(b.vuCtx, session, browserCtx, targetPage.TargetID, opener, isPage, b.logger)
	if err != nil && b.isPageAttachmentErrorIgnorable(ev, session, err) {
		if b.closing.Load() {
			b.logger.Debugf("Browser:onAttachedToTarget", "new page failed; browser is closing: sid:%v", ev.SessionID)
			detachSession(b.browserCtx, session)
		}
		return nil // Ignore this page.
	}
	if err != nil {
		return fmt.Errorf("creating a new %s: %w", targetPage.Type, err)
	}

	// This prevents a race where Close() sets closing and snapshots
	// pages, but a new page is inserted outside that snapshot.
	if err := b.attachNewPage(p, ev); err != nil {
		if !errors.Is(err, errBrowserClosing) {
			return fmt.Errorf("attaching new page: %w", err)
		}

		b.logger.Debugf(
			"Browser:onAttachedToTarget",
			"rejected page attachment; browser is closing: sid:%v tid:%v",
			ev.SessionID, ev.TargetInfo.TargetID,
		)
		if closeErr := p.Close(); closeErr != nil {
			b.logger.Debugf(
				"Browser:onAttachedToTarget",
				"closing rejected page: %v", closeErr,

View on GitHub (pinned to 93accf6570)

Solutions

1. Read the full chain ('browser is attaching to target: creating a new page: <cause>') to see whether it is a session/closed error or a CDP protocol error
2. Avoid triggering unhandled popups: block them via launch args or handle window.open targets explicitly in the test flow
3. If it happens under load, increase K6_BROWSER_TIMEOUT and reduce concurrent browser activity against the same Chrome instance
4. Ensure you are not closing pages/contexts concurrently while new targets appear (serialize close and open operations in the script)
5. Update k6 — attachment-error classification (isPageAttachmentErrorIgnorable) has been improved over releases; report reproductions to k6 issues

Example fix

// before
page.click('#open-popup');  // popup target arrives while script closes context
browser.close();

// after
const popupPromise = page.waitForEvent('popup');
page.click('#open-popup');
const popup = await popupPromise;
popup.close();
browser.close();

// The error surfaces as an iteration panic ('browser is attaching to target: creating a new page: ...').
// Guard the flows that spawn targets:
try {
  const popupPromise = page.waitForEvent('popup');
  await page.click('#open-popup');
  const popup = await popupPromise;
  await popup.close();
} catch (e) {
  if (String(e.message).includes('creating a new')) {
    console.error('A target attached while the session/context was unstable; serialize opens/closes:', e.message);
  }
  throw e;
}

When it happens

Trigger: A new page or popup attaching while the connection is degraded or the session was already detached; NewPage's internal setup CDP calls failing (e.g. target crashed concurrently); pages created by the site under test (window.open, popups, OAuth flows) arriving during teardown races that are not classified as ignorable; Chrome extensions spawning background pages with malformed targets.

Common situations: Tests clicking links that trigger popups/OAuth redirects while k6 is also navigating/closing; remote Chrome under heavy load dropping sessions; site under test spawning many targets; usually surfaces as an iteration abort with 'browser is attaching to target: creating a new page: ...'.

Related errors

• parent frame has been detached
• disposing browser context ID %s: %w
• attaching new page: %w
• adding init script to browser context: %w
• updating geo location in target ID %s: %w

AI-assisted analysis of grafana/k6@93accf6570 (2026-08-15). Data as JSON: /api/errors/e18f163ac632c3d7. Report an issue: GitHub.