A three-day, largely unsupervised model run produced a new attack technique on round-reduced AES

In the same 28 July 2026 post, Anthropic described Claude working for roughly three days and about one billion output tokens through a scaffolded research process with substantially less direct human guidance, producing a technique its researchers named the "Möbius Bridge". It speeds up a known class of meet-in-the-middle attack against a 7-round version of AES by 200 to 800 times, by removing a step that previously required checking 2^56 possibilities. The cipher actually protecting live traffic is untouched: full AES runs 10 rounds, and the 7-round variant exists only as a research target. Anthropic's researchers spent several hundred hours validating the result before it was published.

What it means The reusable part is the shape of the work rather than the cipher: a multi-day, lightly-steered run produced a novel named technique, and several hundred hours of expert verification came afterwards — the verification is what made it trustworthy, not the autonomy.