Anthropic Denies EU Access to Claude Mythos, ChatGPT 5.5 Comes to Rescue

Why It Matters

EU access to a high‑performing AI cyber‑defense tool mitigates the risk gap created by Anthropic’s refusal, while also influencing regulatory and geopolitical dynamics in the AI market.

Key Takeaways

• Anthropic's Claude Mythos remains unavailable to EU regulators
• ChatGPT 5.5 achieved 71.4% pass on AISI expert cyber tasks
• EU firms like Deutsche Telekom and BBVA now use GPT‑5.5
• OpenAI for Countries, led by George Osborne, democratizes AI defense
• EU may classify ChatGPT as a Very Large Online Search Engine

Pulse Analysis

Artificial intelligence has become a double‑edged sword in cybersecurity, with vendors racing to embed threat‑hunting capabilities into large language models. Anthropic’s Claude Mythos, unveiled in April, boasted the discovery of thousands of high‑severity vulnerabilities, positioning it as a potential defensive asset for European institutions. Yet despite multiple meetings, Anthropic has not granted the EU direct access, fueling anxiety among regulators who fear a capability gap as adversaries weaponize similar technology. The stalemate underscores how quickly AI breakthroughs can outpace diplomatic negotiations.

OpenAI’s response arrived in the form of ChatGPT 5.5, a model that the UK‑based AI Security Institute (AISI) evaluated as matching—or slightly surpassing—Mythos on expert‑level cyber tasks. The model posted a 71.4 % pass rate on AISI’s advanced suite, edging out Claude Mythos’s 68.6 % score. Leveraging the OpenAI for Countries program, the company has already provisioned GPT‑5.5 to European heavyweights such as Deutsche Telekom, BBVA, Telefónica, Sophos and Scalable Capital. For EU banks and critical‑infrastructure operators, the rollout offers an immediate defensive toolkit while the Mythos debate continues.

The EU’s pending decision on whether to label ChatGPT a Very Large Online Search Engine adds a regulatory layer that could shape market access and data‑privacy obligations. OpenAI’s partnership with former UK treasury minister George Osborne signals a strategic push to embed the firm within European policy circles, blending product rollout with lobbying. As AI‑driven cyber tools become integral to national security, the contest between Anthropic and OpenAI illustrates how technical performance, geopolitical positioning, and regulatory frameworks will jointly dictate the next generation of defensive AI services.