grafana/k6 · error

evaluating JS in global context: %w

Error message

evaluating JS in global context: %w

What it means

Frame.EvaluateGlobal() executes raw JS via CDP runtime.Evaluate on the frame's session (not a page-function call). This error wraps the protocol-level Do() failure: the CDP session/target is closed or the execution context is gone — distinct from a JS exception, which is handled separately.

Source

Thrown at internal/js/modules/k6/browser/common/frame.go:892

}

// Evaluate will evaluate provided page function within an execution context.
func (f *Frame) Evaluate(pageFunc string, args ...any) (any, error) {
	f.log.Debugf("Frame:Evaluate", "fid:%s furl:%q", f.ID(), f.URL())

	return f.EvaluateWithContext(f.ctx, pageFunc, args...)
}

// EvaluateGlobal will evaluate the given JS code in the global object.
func (f *Frame) EvaluateGlobal(ctx context.Context, js string) error {
	action := runtime.Evaluate(js).WithAwaitPromise(true)

	var (
		exceptionDetails *runtime.ExceptionDetails
		err              error
	)
	if _, exceptionDetails, err = action.Do(cdp.WithExecutor(ctx, f.manager.session)); err != nil {
		return fmt.Errorf("evaluating JS in global context: %w", err)
	}
	if exceptionDetails != nil {
		return fmt.Errorf("%s", parseExceptionDetails(exceptionDetails))
	}

	return nil
}

// EvaluateHandle will evaluate provided page function within an execution context.
func (f *Frame) EvaluateHandle(pageFunc string, args ...any) (handle JSHandleAPI, _ error) {
	f.log.Debugf("Frame:EvaluateHandle", "fid:%s furl:%q", f.ID(), f.URL())

	evalHandle := func() (JSHandleAPI, error) {
		f.executionContextMu.RLock()
		defer f.executionContextMu.RUnlock()

		ec := f.executionContexts[mainWorld]
		if ec == nil {

View on GitHub (pinned to 93accf6570)

Solutions

1. Ensure a document exists first: waitForLoadState('domcontentloaded') before EvaluateGlobal.
2. Retry once after navigation settles.
3. Check that the page/browser is still open and earlier steps did not close it.

Example fix

// before
const page = await browser.newPage();
page.evaluateGlobal('window.__stub = true'); // too early / mid-nav

// after
const page = await browser.newPage();
await page.goto(url);
await page.waitForLoadState('domcontentloaded');
page.evaluateGlobal('window.__stub = true');

await page.goto(url);
await page.waitForLoadState('domcontentloaded');

for (let i = 0; i < 3; i++) {
  try { page.evaluateGlobal(js); return; } catch (e) { await sleep(500); }
}
throw new Error('evaluateGlobal failed after retries');

When it happens

Trigger: Calling EvaluateGlobal while the page is navigating or closing; the browser process crashed; the frame's session was detached (iframe swapped).

Common situations: Installing global stubs (window.fetch mocks) right at page creation before any document exists; evaluating during teardown after page.close(); crashed browser under memory pressure in CI.

Related errors

• errorText
• getting node in frame: %w
• no frame found for node: %w
• getting injected script: %w
• expected node but got %s

AI-assisted analysis of grafana/k6@93accf6570 (2026-08-15). Data as JSON: /api/errors/c2ec6eef7d81da1a. Report an issue: GitHub.