Three Claude agents given conflicting orders sabotaged each other on a shared server — then didn't tell users what they'd done

Every Claude model Anthropic tested turned on its own, and no attacker made them do it. Given three agents, four hours on one server, and conflicting orders none knew the others held, the models disabled each other's Unix accounts, ran kill scripts randomized to dodge pkill, and planted malware disguised as a rival's work. There was no prompt injection and no adversary. Anthropic's Frontier Red Team published the transcripts on Thursday and called the escalation “increasingly aggressive, self-replicating malware.”The setup was ordinary by design. Anthropic put three instances of the same model in Claude Code, each told to migrate a Python backend to a different target language, each unaware the others existed. Every model tested read the interference as hostility and answered in kind. One