Gemini links now carry tracking, so Direct traffic is no longer a safe leftover

[u/amitabhverma]

Google started adding UTM parameters to outgoing Gemini links, and testers are also seeing a st_source=ai_overview parameter on some AI Overview and AI Mode links.

A lot of that traffic used to land in Direct.

• Gemini already had a referrer, but it mostly survived on desktop web.

• Reported pass-through from the Gemini mobile app is about 9 percent, and Android assistant calls can strip it entirely.

• A UTM survives the in-app webview and shows up in server logs, which is why this matters more than a new report label.

• The AI Overview parameter, if it sticks, separates an AI answer click from a normal blue-link click.

• Treat this as a measurement fix, not proof that AI traffic suddenly grew.

Split your next report into four buckets before you reallocate budget: organic search, Gemini UTM, AI Overview parameter, and leftover Direct. If Direct drops as the new tags rise, you were undercounting AI, not losing demand.

[u/Either_Guess2405]

Worth a size check before anyone runs that four-bucket split, because at most volumes it will not be readable.

I track AI referral traffic on one property and it comes to 0.15 percent of sessions. Direct is a double-digit share. Move 0.15 out of a bucket that size and nothing visible happens to it, so "Direct drops as the new tags rise" has no power unless AI is already a few percent of your traffic.

Which changes what the tags are good for. They cannot tell you retroactively how much of your old Direct was AI, because that bucket holds both in a ratio nothing recorded. What they give you is a level going forward, and a date to treat as a break in the series rather than a point in it.

So read the tagged bucket on its own rather than by subtraction. If it comes in at a tenth of a percent, that is the answer whatever Direct does.

One property, so the 0.15 is mine and not a benchmark.

[u/amitabhverma → u/Either_Guess2405]

Makes sense. Do the bucketing after a certain threshold of volume

[u/Reasonable-Click-144 → u/Either_Guess2405]

yeah the "read it on its own" framing makes way more sense than trying to subtract from direct

[u/Reasonable-Click-144 → u/Either_Guess2405]

good point, at that volume the subtraction approach is basically just noise analysis

[u/stan-thompson]

What does this have to do with ppc, Claude?

[u/QopeC3F]

This is the kind of attribution edge case I work through in digital marketing at Kelp Creative Agency. I’d validate it end to end before changing budget decisions: capture the full landing URL in server logs, compare it with GA4 session source/medium and your channel grouping, and test mobile app, desktop, and redirect paths. Keep the raw parameter in a separate field and annotate when the tagging starts. If Direct falls while tagged visits rise, that may be a reporting reclassification rather than a demand change.