internal error while getting browser target info

Error message

internal error while getting browser target info: %w

What it means

Right after setAutoAttach, connect() issues a dummy Target.getTargetInfo call to work around a Chromium bug where setAutoAttach does not wait for pending target attachments (see the chromium-review link in the source). This error wraps that follow-up CDP call failing, i.e. the connection or browser died within milliseconds of the previous command, or the endpoint partially implements CDP.

Solutions

Check whether the browser process was killed (dmesg OOM lines, container exit code 137) and raise memory limits
Stabilize the remote endpoint / proxy between k6 and the browser
Match Chromium or headless-shell version to the k6 release notes
Capture K6_BROWSER_LOG=debug output and report if it persists on stock versions

Defensive patterns

Strategy: retry

Try / catch

try {
  const browser = chromium.launch();
} catch (e) {
  if (String(e).includes('getting browser target info')) {
    // connection dropped right after connect; check for OOM-killed browser
    // (exit 137, dmesg), stabilize environment, retry once
  }
}

Prevention

Watch for OOM kills on browser containers during startup
Give the browser a few seconds of warm-up before heavy load
Use stable network paths to remote browsers

When it happens

Trigger: Connection loss between setAutoAttach and GetTargetInfo; browser process killed (OOM, SIGKILL from CI timeouts) moments after startup; a CDP proxy dropping frames; protocol-level mismatch with an unsupported browser build.

Common situations: CI jobs killing the browser with strict timeouts; memory-constrained runners; flaky WS proxies in remote-browser setups.

Related errors

AI-assisted analysis of grafana/k6@3fcf5388d7 (2026-08-18). Data as JSON: /api/errors/bc8f7c0a774c2bc5. Report an issue: GitHub.

Appendix: source

Thrown at internal/js/modules/k6/browser/common/browser.go:260

				} else if event.typ == EventConnectionClose {
					b.logger.Debugf("Browser:initEvents:EventConnectionClose", "")
					return
				}
			}
		}
	}()

	action := target.SetAutoAttach(true, true).WithFlatten(true)
	if err := action.Do(cdp.WithExecutor(b.vuCtx, b.conn)); err != nil {
		return fmt.Errorf("internal error while auto-attaching to browser pages: %w", err)
	}

	// Target.setAutoAttach has a bug where it does not wait for new Targets being attached.
	// However making a dummy call afterwards fixes this.
	// This can be removed after https://chromium-review.googlesource.com/c/chromium/src/+/2885888 lands in stable.
	action2 := target.GetTargetInfo()
	if _, err := action2.Do(cdp.WithExecutor(b.vuCtx, b.conn)); err != nil {
		return fmt.Errorf("internal error while getting browser target info: %w", err)
	}

	return nil
}

// connectionOnAttachedToTarget is called when Connection receives an attachedToTarget
// event. Returning false makes the connection release the target instead of
// adopting it. Targets from the connection's own browser context and from
// the default browser context are accepted.
func (b *Browser) connectionOnAttachedToTarget(eva *target.EventAttachedToTarget) bool {
	b.contextMu.RLock()
	defer b.contextMu.RUnlock()
	if b.context != nil && b.context.id == eva.TargetInfo.BrowserContextID {
		return true
	}
	return b.defaultContext.id == eva.TargetInfo.BrowserContextID
}

View on GitHub (pinned to 3fcf5388d7)