Fix our GA4 / Shopify / Google Ads attribution disagreement — sGTM expert, US-based

Less than 1 month, Less than 30 hrs/week Only freelancers located in the United States may apply. We sell high AOV, highly considered products direct-to-consumer on Shopify. Google Ads, GA4 and Shopify disagree about the same traffic by an order of magnitude. We have already done the diagnosis. We know which defects we're chasing and we have a frozen baseline to measure against. We're hiring someone to fix it, not to audit us. If you're looking for a two-week discovery engagement, this isn't it. Stack: Shopify · Stape-hosted server-side GTM · GTM web container · GA4 · Google Ads · Microsoft · Meta · Klaviyo The work: parameter delivery between click and landing · a client-side / server-side double-fire · cookie-lifetime loss · GA4 channel groupings · UTM taxonomy unified at source · one verified end-to-end test order visible and correctly attributed in all three systems. Payment is gated on acceptance tests — specific pass/fail thresholds measured against our baseline. We'll share the numbers and the full brief with candidates we shortlist. Out of scope: manually-created orders and offline sales (no web session, handled internally) · dashboard rebuilds · retainers. This is bounded work.. Budget: tell us what you'd charge and how long you need. We're comparing on your scoping and your answers below, not on price alone. Answer all four in your proposal 1) A server-side GTM endpoint sits on a subdomain that CNAMEs to a third-party host. What does that do to cookie lifetimes in Safari, and how would you mitigate it? 2) A site runs client-side gtag and a server container at the same time. Name two distinct ways that produces a GA4 overcount, and how you'd determine which one is happening. 3) Shopify shows a large share of sessions with no UTM while the ad platforms show the clicks arriving. Name the first three things you'd check, in order, and what result would rule each one out. 4) Have you used customerJourneySummary in the Shopify Admin GraphQL API? What are its limits, and what would you use alongside it?