This is the failure this news log exists to catch, and it still got through.
Project Mariner was listed here as a Research preview, available to AI Ultra subscribers in the US, with a citation pointing at DeepMind's model index. That page no longer mentions Project Mariner at all. Reporting dates the shutdown to 4 May 2026, with the capability folded into Gemini Spark and Chrome's auto browse. The entry was wrong before this site was ever built, and stayed wrong through two verification passes.
The reason it survived is worth stating plainly, because it is a flaw in the method rather than bad luck. Both previous passes checked entries against their sources and then swept for agents that were missing. Neither asked the opposite question: which listed agents no longer exist? A dead product does not announce itself. Its page quietly stops mentioning it, and a checker reading that page for a licence or a stage sees nothing that contradicts what is already recorded.
So the sweep now runs both ways, and the entry is marked superseded and unconfirmed rather than quietly deleted — partly because Google published no retirement notice we could find, and at least one secondary source still described Mariner as available after the reported shutdown date. We would rather show the disagreement than pick a side.