Originally published on NextFuture

Anthropic's Mythos and OpenAI's GPT-5.5-Cyber both shipped in April–May 2026 as purpose-built cybersecurity models, and both landed behind strict allowlists within days of each other. For AI engineers evaluating them honestly, the core problem is the same: most practitioners can't get direct API access, so any comparison relies on third-party evals, CTF leaderboard data, and structured capability disclosures from partner briefings. This piece pulls those threads together and gives you the clearest signal available as of May 4, 2026.…