GPT-5.5 Cybersecurity capabilities beat Claude Mythos! The White House green-lights it vs. gets it censored—two fates

OpenAI launches the latest cybersecurity model GPT-5.5-Cyber, surpassing Anthropic's Mythos 5 with an 85.6% success rate in UC Berkeley CyberGym benchmark tests, which was decommissioned by the U.S. government (83.8%). OpenAI's Daybreak project has collaborated with cybersecurity agencies from seven countries and the European Union, and partnered with 28 security vendors including CrowdStrike and Cisco to integrate products, charting a regulatory path vastly different from Anthropic.
(Background: OpenAI releases cybersecurity-specific model GPT-5.4-Cyber: fixed 3,000 high-risk vulnerabilities, competing with Claude Mythos)
(Additional context: Anthropic Fable 5 is under scrutiny by Trump, who is laughing behind the scenes? Media reveals three major beneficiaries)

Table of Contents

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• Same capability, two fates: Why does the White House approve OpenAI but ban Anthropic?
• Self-fulfilling prophecy? Anthropic’s honesty dilemma and policy costs
• From patching vulnerabilities to healing the planet: OpenAI’s defensive ecosystem takes shape

June 2026, a dramatic split emerges in the AI safety race. On June 22, OpenAI officially released GPT-5.5-Cyber, the latest flagship model of its Daybreak cybersecurity initiative. In the UC Berkeley CyberGym benchmark, which tests AI agents against 1,507 known software vulnerabilities across 188 open-source projects, GPT-5.5-Cyber achieved an 85.6% remediation rate.

The control group is intriguing: Anthropic’s Mythos 5 scored 83.8%, while Anthropic’s more widely available Claude Opus 4.7 only achieved 73.1%. Less than two percentage points might seem insignificant in typical benchmarks, but the regulatory circumstances behind them are worlds apart. Mythos 5 and Fable 5 were forcibly taken offline on June 12 by the Trump administration under an “Emergency Export Control Directive,” and remain offline to this day.

Same capability, two fates: Why does the White House approve OpenAI but ban Anthropic?

The direct trigger for Anthropic’s Mythos 5 being taken down was a jailbreak vulnerability—an exploit that bypasses AI safety restrictions, akin to a master key to a high-security lock. Because Anthropic couldn’t verify user nationalities at scale, they ultimately shut down these two models for all users worldwide. More than ten days have passed, and neither Anthropic nor the U.S. Commerce Department has provided a clear timeline for restoration.

But OpenAI’s GPT-5.5-Cyber remains operational and has received official backing. Before deployment, OpenAI completed pre-deployment testing with federal agencies, including the Center for AI Standards and Innovation and the Office of the National Cyber Director. In other words, OpenAI chose to get government approval before going live, rather than launching first and being shut down later like Anthropic.

This “pre-approval” strategy has proven effective. Daybreak has signed cybersecurity cooperation agreements with agencies in Australia, Canada, France, Germany, Japan, South Korea, and the EU (including ENISA, the EU Cybersecurity Agency). Twenty-eight security vendors, including CrowdStrike, Cisco, and Cloudflare, have joined its Cyber Partner Program, integrating GPT-5.5 into their products for certified clients.

Self-fulfilling prophecy? Anthropic’s honesty dilemma and policy costs

Part of the problem stems from Anthropic’s own actions. The company spent months describing Mythos as “one of the most powerful and dangerous AI models ever,” explicitly warning in its release documents that its cybersecurity capabilities could cause serious harm if not properly restricted. Co-founder Dario Amodei, in a lengthy post on June 10, compared cutting-edge AI models to airplanes, arguing that safety regulators should be able to ground them if they are unverified. A few days later, the government indeed grounded Anthropic’s “plane.”

Worse, in the same week, Anthropic was exposed for hiding censorship filters within Fable 5, which silently lowered output quality for users suspected of developing competing models. Anthropic was forced to apologize and withdraw the policy, but public trust was damaged.

This contrasts sharply with OpenAI’s approach. GPT-5.5-Cyber is similarly not open to the general public, only available to verified security professionals. The restrictions are comparable to Anthropic’s control over Mythos, but OpenAI preemptively engaged with regulators, rather than being forced to comply after the fact.

From patching vulnerabilities to healing the planet: OpenAI’s defensive ecosystem takes shape

According to OpenAI’s official blog, Codex Security tools have scanned over 30 million commits across 30k repositories since March, recording more than 500k patched vulnerabilities. OpenAI also launched the “Patch the Planet” initiative to help fix security flaws in widely used open-source projects, actively strengthening the global software supply chain, not just defending its own systems.

This AI safety race highlights a structural contradiction: when the most powerful models are also the most dangerous, honestly disclosing risks can backfire. Anthropic’s frank warnings about Mythos’s destructive potential led to a government ban; OpenAI’s similar restrictions, backed by official approval, allow it to continue operating.

As of June 23, Fable 5 and Mythos 5 remain offline, with Anthropic negotiating with the Commerce Department and suing the Trump administration. Meanwhile, OpenAI’s Daybreak project is expanding from cybersecurity to international cooperation. The strategic differences between the two companies are no longer just about technical routes but also about survival in the AI regulation era.