GA4 hides most LLM traffic inside Referral and Direct, so the fix is one custom channel group with a source regex, placed above Referral so it wins the match.
The direct answer is one setting: a custom channel group with a source regex. Here is the full setup, plus the traps.
First, know what Google now gives you for free. On May 13, 2026, GA4 added a native AI Assistant channel that tags referrals from tools like ChatGPT, Gemini, Copilot, DeepSeek and Grok. It needs no setup, but it is not retroactive, and it skips Perplexity, so that traffic still lands in plain Referral. Default channel groups cannot be edited, so you cannot patch the gap there.
So build your own. In GA4, open Admin, then Data display, then Channel groups, and create a new group. Add a channel named AI traffic. Set the condition to Source, matches regex, and use a pattern like this:
Then do the step most people miss. Drag your AI channel above Referral in the list, because GA4 checks rules top to bottom, and if Referral sits higher it claims the sessions first. Also note that regex matching is case sensitive, so add variants or an (?i) flag if your data shows mixed case.
The good news about this method: custom channel groups apply to your historical data, so the moment you save, you can compare AI sessions against organic going back months. Validate it in an Exploration with Session source as a dimension and the same regex as a filter.
Now the honest limits. Between 35 and 70 percent of AI sessions arrive with no referrer and fall into Direct, because people copy links or click from mobile apps. AI Overview and AI Mode clicks stay inside Organic Search. So your AI channel is a floor, not a total, and agent purchases can skip page tracking entirely.
Read the numbers with that in mind. AI referrals sit around 0.9 percent of web traffic, up five times year over year, with ChatGPT holding roughly three quarters of it. The sessions are few and they convert far above organic, so revenue per session is the metric that tells the truth, and pairing GA4 with your Shopify channel reports closes the rest of the gap.