grafana/k6 · error

unpacking scroll offset

Error message

unpacking scroll offset: %w

What it means

Raised in screenshotElement after the window.scrollX/scrollY evaluation succeeded but its result could not be converted (via the convert helper) into the expected Position struct {X, Y float64}. This is a shape/type mismatch: the CDP Runtime.evaluate result came back in a form (e.g. not a remote object with numeric properties) that cannot be unmarshalled, indicating an unexpected or corrupted evaluation payload rather than a page-level problem.

Solutions

1. This is an internal conversion failure; report it as a k6 browser module bug with the page HTML and reproduction script
2. Update k6 to the latest version where conversion of CDP remote objects may have been fixed
3. Test with a simpler page to see if a specific page construct triggers the malformed payload

When it happens

Trigger: Thrown at internal/js/modules/k6/browser/common/screenshotter.go:329 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of grafana/k6@3fcf5388d7 (2026-08-18). Data as JSON: /api/errors/c5f29661924745ab. Report an issue: GitHub.

Appendix: source

Thrown at internal/js/modules/k6/browser/common/screenshotter.go:351

		if err != nil {
			return nil, fmt.Errorf("node is either not visible or not an HTMLElement: %w", err)
		}
		if bbox.Width <= 0 {
			return nil, fmt.Errorf("node has 0 width")
		}
		if bbox.Height <= 0 {
			return nil, fmt.Errorf("node has 0 height")
		}
	}

	scrollOffset, err := h.Evaluate(`() => { return {x: window.scrollX, y: window.scrollY};}`)
	if err != nil {
		return nil, fmt.Errorf("evaluating scroll offset: %w", err)
	}

	var returnVal Position
	if err := convert(scrollOffset, &returnVal); err != nil {
		return nil, fmt.Errorf("unpacking scroll offset: %w", err)
	}

	documentRect := bbox
	documentRect.X += returnVal.X
	documentRect.Y += returnVal.Y

	return s.screenshot(
		h.frame.page.session,
		documentRect.enclosingIntRect(),
		nil, // viewportRect
		format,
		opts.OmitBackground,
		opts.Quality,
		opts.Path,
	)
}

func (s *screenshotter) screenshotPage(p *Page, opts *PageScreenshotOptions) (buf []byte, err error) {

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