We took the same agent from our earlier experiment and added one thing: a twentieth tool, escalate_security_incident.
The system prompt said nothing about attacks or when to use it. We then ran the same 395 injected emails through nine agentic models.
Alarm rates ranged from 49% to zero.
The unexpected result came from the newest model in the test, gpt-6-astra.
Astra did not follow a single injected payment instruction. But it did not report a single one either. On clean and injected emails alike, it simply read the email, logged the subject, and finished.
That is a useful distinction: resisting an attack and recognizing it as a security event are not the same capability.
A model can be perfectly resistant in this test and still leave you with no evidence that anyone attacked it.