Anthropic says Claude Mythos Preview helped derive an end-to-end key-recovery attack against HAWK-256 and a 200-to 800-fold speedup for an attack on seven-round AES-128.

The HAWK attack exploits a previously unused symmetry in the lattice behind the signature scheme. Anthropic’s released implementation gives an expected end-to-end runtime of about three hours and 42 minutes on a 96-core server. The AES result removes a 256-way guessing step from an existing meet-in-the-middle attack.

Anthropic said neither result affects production systems. HAWK remains a candidate in a National Institute of Standards and Technology (NIST) post-quantum standardization process, and the public recovery code only targets the smaller HAWK-256 parameter.