Skip the allowlist queue. Five production-ready defensive AI tools — open weights, hosted APIs, and self-hostable stacks — that protect real apps today, with cost and integration notes.
The GPT-5.5-Cyber capability profile beyond OpenAI's marketing: Simon Willison's evals, the Trusted Access Program scope, and what the Five Eyes briefings actually covered.
Mythos and GPT-Cyber are locked. Open-source alternatives (CodeLlama Guard, Llama Guard 3, Cisco AI defense) are not. We compared both stacks on 4 defensive tasks—the honest results.
We compared what Anthropic Mythos and OpenAI GPT-5.5-Cyber actually do on offensive testing tasks. Capabilities, refusal patterns, evals, and where each model breaks down.
Anthropic's Mythos and OpenAI's GPT-5.5-Cyber both ship locked behind allowlists. Here's what's inside each model, who actually gets access, and what the rest of us can build today.