What causes "timeout waiting for target to be removed: {}" in karatelabs/karate?

Ignore if the tab is actually gone — this is a warning, not an error; verify with driver.getPages().

timeout waiting for target to be removed

Error message

timeout waiting for target to be removed: {}

What it means

After closing a tab, CdpDriver waits for Target.targetDestroyed (or the page list to shrink) and falls back to a direct getPages() check. If the target still appears present after the wait, this warning is logged — the target removal event never arrived. Usually benign if the target did go away but the event/page list lagged; concerning if the tab genuinely failed to close.

Solutions

Ignore if the tab is actually gone — this is a warning, not an error; verify with driver.getPages().
Remove beforeunload handlers in the page before closing tabs.
If targets genuinely leak, close the whole browser (quit) instead of individual tabs.
Check CDP/websocket health and browser version; upgrade if event delivery is chronically delayed.

Example fix

// before
driver.close(); // closes current tab, may warn
// after
driver.script("window", "window.onbeforeunload = null");
driver.close();

Defensive patterns

Strategy: fallback

Validate before calling

// remove beforeunload before closing tabs
driver.script("window", "window.onbeforeunload = null");

Try / catch

try {
    driver.close();
} catch (RuntimeException e) {
    // if the target genuinely leaked, tear down the whole browser
    if (!driver.isTerminated()) { driver.quit(); }
}

Prevention

Clear beforeunload handlers before tab close
Prefer quitting the whole browser when closing many tabs
Verify with getPages() whether the target truly leaked
Keep browser builds current to avoid event-delivery delays

When it happens

Trigger: close() of a tab where Target.targetDestroyed wasn't observed within the wait window, slow CDP event delivery under load, beforeunload handlers blocking close, or a hung renderer keeping the target alive.

Common situations: Closing tabs with beforeunload dialogs, heavily loaded CI machines delaying CDP events, pages with long-running JS blocking teardown, or browser builds with delayed target cleanup.

Understand the failure class

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

Related errors

AI-assisted analysis of karatelabs/karate@a22eb90246 (2026-09-12). Data as JSON: /api/errors/c37948f136a86855. Report an issue: GitHub.

Appendix: source

Thrown at karate-core/src/main/java/io/karatelabs/driver/cdp/CdpDriver.java:2802

    /**
     * Wait for a closed target to actually disappear, event-driven: the future is
     * completed by the Target.targetDestroyed handler. That event's delivery depends
     * on Target.setDiscoverTargets, which initialize() arms best-effort — so on
     * timeout, fall back to ONE page-list check before declaring a problem.
     */
    private void waitForTargetRemoved(String targetId, CompletableFuture<Void> removed) {
        try {
            removed.get(1000, TimeUnit.MILLISECONDS);
            logger.trace("target removal confirmed by event: {}", targetId);
            return;
        } catch (Exception e) {
            // fall through to the direct check
        }
        if (!getPages().contains(targetId)) {
            logger.trace("target removed from page list: {}", targetId);
            return;
        }
        logger.warn("timeout waiting for target to be removed: {}", targetId);
    }

    public boolean isTerminated() {
        return terminated;
    }

    @Override
    public boolean isReady() {
        CompletableFuture<Integer> f = mainContextReady;
        return f.isDone() && !f.isCompletedExceptionally();
    }

    @Override
    public void waitUntilReady() {
        // The main frame execution context being live is the authoritative readiness
        // signal (see mainContextReady). Block on it up to the configured timeout;
        // returns immediately when already ready.
        awaitMainContext(options.getTimeoutDuration().toMillis());

View on GitHub (pinned to a22eb90246)