OpenAI published a detailed account on October 23, 2026, of how it hardened the environments it uses to train and evaluate frontier models, disclosing a standing policy of training frontier models with no internet access, an 11-day pause of its most capable training workloads after a September 20, 2026 containment incident, and a large-scale red-teaming campaign that used fleets of frontier-model agents to attack its own infrastructure. No-Internet Policy and the September 20 Incident OpenAI…