Hey @Lucas_Sena - thanks for reaching out. We had a related thread here that covers the same limitation around passing referral or campaign query parameters through an App Store installation:
The URL parameters won’t reliably carry through into the actual app session after installation, so relying on the ad_stamp cookie isn’t a dependable way to grant trial days.
For supported App Store funnel attribution, Shopify provides listing traffic tracking with Google Analytics or Facebook Pixel:
With this configured, Shopify can send events such as shopify_app_ad_click and shopify_app_install, including shop details on the installation event. This is intended for analytics attribution rather than passing a custom campaign token into your app.
For app-side trial handling, you’d likely need an explicit handoff you control, such as a short-lived referral token redeemed after installation or a referral/promo code. Once the app opens, I’d use the verified Shopify session to identify the shop and associate it with that referral.
If these are external ads rather than Shopify App Store ads, the App Store tracking events won’t include your external ad_stamp.
Let me know if I can help out further.