Start checkout with attribution IDs ready

Start checkout with visitor and session IDs ready, even when someone clicks immediately after landing on your site. The new Stripe and Polar examples wait briefly for XPmetric's first tracking response before passing those IDs into checkout.

If the payment reaches XPmetric before its pageview is available for attribution, XPmetric retries the match for up to 24 hours. Your existing checkout integration keeps working.

Default cookieless attribution remains scoped to each visitor ID's UTC day. The revenue guides now explain that limit and when cookie mode provides cross-day first-touch.