Visa used Mythos to hunt for bugs in its own payment network, then open-sourced the harness that made it possible

Visa aimed Anthropic’s Claude Mythos at the infrastructure behind billions of daily transactions, a network that spans more than 200 countries and territories, moves money in roughly 160 currencies, and connects nearly 5 billion payment credentials to more than 175 million merchant locations. The model stitched minor weaknesses deep in the stack into working exploit chains that would traditionally have surfaced only late in penetration testing. Rajat Taneja, Visa’s president of technology, walked the VB Transform 2026 audience through what came next, including why Visa released the harness tha