Both Mythos and GPT-5.5 Cyber are positioned to identify software vulnerabilities and aid defenders, with Mythos emphasizing elite access and claims of uncovering long-standing and new vulnerabilities, while GPT-5.5 Cyber stresses accessibility and rapid defender-oriented feedback.

Anthropic has restricted ultra-capable AI release by limiting access and highlights sharing learnings from Project Glasswing to help the broader industry.

Critics, including OpenAI's Sam Altman, question Mythos’ claimed capabilities and the marketing framing around its risks and exclusivity.

OpenAI released GPT-5.5 Cyber to meet cybersecurity needs through the Trusted Access for Cyber program, which allows verified individuals and organizations to apply for access with identity verification akin to KYC checks.

Mythos is described as more capable than GPT-5.5 Cyber, able to process larger data, retain context better, and perform more parallel analysis, though at a higher cost—roughly 10 to 12 times more expensive.

Anthropic announced Mythos, a Claude-family model with restricted access via an invite-only Project Glasswing, limited to about 40 cybersecurity-focused organizations.

The core difference lies in access strategy: Mythos is tightly controlled and exclusive, while GPT-5.5 Cyber aims for broader participation among cybersecurity professionals to drive defense and rapid feedback.

OpenAI argues that easier defender access accelerates vulnerability discovery and enables immediate, actionable security improvements while mitigating misuse.