OpenAI Launches GPT-5.5-Cyber, Taking Direct Aim at Anthropic Mythos

OpenAI announced GPT‑5.5-Cyber on May 7, 2026 — a specialized variation of its GPT‑5.5 model tuned for cybersecurity workflows. The company is clear that this isn't a major leap in raw cyber capability. Instead, the model is trained to be more permissive on security‑related tasks that the generally available GPT‑5.5 model restricts, according to CNBC.

OpenAI said in a blog post that "GPT‑5.5‑Cyber lets a smaller set of partners study advanced workflows where specialized access behavior may matter." The model is designed for vulnerability identification and triage, patch validation, and malware analysis.

GPT‑5.5-Cyber is not broadly available. Access is limited to participants in OpenAI's Trusted Access for Cyber (TAC) program — vetted cybersecurity professionals, especially those responsible for critical infrastructure, according to Politico. Approved users must install advanced account security for ChatGPT by June 1.

OpenAI previewed the model for the White House, the Commerce Department's Center for AI Standards and Innovation, select Congressional committees, and other "key agencies," per.²

The launch comes roughly one month after Anthropic released Claude Mythos Preview, which CEO Dario Amodei described as capable of finding tens of thousands of unpatched software vulnerabilities. Mythos sparked high‑level government attention — Federal Reserve Chairman Jerome Powell and Treasury Secretary Scott Bessent met with bank CEOs to discuss it, and Vice President JD Vance held calls with tech leaders ahead of its release, according to CNBC.

Anthropic restricted Mythos to a small group through its Project Glasswing initiative. Rob Bair, head of cyber policy at Anthropic, said the staged release was designed to create a "defender's advantage" window of months, not years, according to Politico.

The two approaches reveal a philosophical split. Anthropic has taken a dramatic, alarm‑ringing posture — warning that Mythos‑level capabilities could destabilize the global economy (the IMF agreed, issuing its own warning the same day), and keeping the model tightly locked down.

OpenAI is noticeably less alarmist. "We believe the class of safeguards in use today sufficiently reduce cyber risk enough to support broad deployment of current models," the company wrote, according to WIRED. OpenAI's cybersecurity strategy has three pillars: controlled access through know‑your‑customer validation, iterative deployment, and investment in software security.

For developers and security engineers, the GPT‑5.5-Cyber vs Mythos dynamic matters for two reasons. First, it signals that frontier AI models with specialized security capabilities are becoming a regular product category — not a one‑off experiment. Expect more cybersecurity‑specific models from both labs and from Google, Microsoft, and others.

Second, the access model matters. If you're doing vulnerability research or security tooling, you'll want to get into these trusted access programs. Both OpenAI and Anthropic are gating their most capable cyber models behind vetting processes — getting approved early could be a competitive advantage.

Katrina Mulligan, head of national security partnerships at OpenAI, captured the tension at the AI+Expo: "There is tension between the need to go fast and the need to be prudent," according to Politico.

The White House is reportedly weighing executive action that could require federal vetting of every advanced AI model before release, per.² Meanwhile, the International Monetary Fund warned that these models pose "financial stability risks" that could "trigger funding strains, raise solvency concerns, and disrupt broader markets" — a warning ¹ characterized as the IMF saying the models could destabilize the global economy.

Both companies are racing to establish themselves as the responsible partner for government cyber defense. Anthropic's Pentagon blacklisting — despite White House softening — adds another layer of complexity. OpenAI's more measured tone may be designed to position itself as the safer government partner.