On an afternoon in mid-May, dozens of Microsoft engineers and their managers gathered online and in a conference room at the company’s Redmond, Washington, headquarters to discuss Project Glasswing.

The tech giant was racing to fix weaknesses in its code that a new AI model known as Mythos was uncovering at an unprecedented clip. The AI behemoth Anthropic, which developed Mythos, had given access to select organizations that make software used by regular people, companies, and governments across the world. The goal was to find and fix the vulnerabilities before hackers and adversarial governments like China began using similar tools to find and exploit them for espionage and sabotage.

As the group settled in, one engineer asked the question that loomed over the meeting: Did Mythos “live up to the hype that Anthropic claimed it would have had?”

“Yes,” a manager responded, according to a recording of the meeting viewed by ProPublica.

The version being used by Microsoft, Claude Mythos Preview, was surfacing bugs faster than the tech giant could patch them, and engineers, the manager said, were now in “a mad dash” to close the gap.

One slide in that day’s presentation showed that in April alone, Mythos had uncovered 90 “critical” bugs and 141 “important” ones in SharePoint, Microsoft’s widely used collaboration software. In the first half of May it found even more.

“Please, please, please if your org has any April bugs, drive those down,” engineering manager Hans Andersen implored the group. They had roughly two weeks “to find as many things and do as much good as we can with this access.”

May 31, he explained, “is considered the day when the rest of the world will have caught up.”

The engineers on the call poked at that assertion, with one of them summing up the predicament: “So basically you’re saying if it’s released on June 1, then on June 2 the adversaries will have our bugs?”