OpenAI offers EU preview access to GPT-5.5-Cyber model while Anthropic withholds Mythos

OpenAI announced Thursday that GPT-5.5-Cyber, a variation of its latest AI model, is rolling out in limited preview capacity to vetted cybersecurity teams. The company is now in discussions with the European Union about providing preview access to the model for security review.

"We welcome OpenAI's transparency and intent to give commission access to new model," Commission Spokesperson Thomas Regnier said at a press briefing Monday. He confirmed an exchange had taken place between OpenAI and the EU, with further discussions planned this week around access to the model.

Anthropic holds back on Mythos access

Anthropic released its Mythos model a month before OpenAI's GPT-5.5-Cyber announcement. According to Regnier, Mythos prompted "a wave of fears around cyberattacks on critical software." Despite this, Anthropic has not granted the EU preview access to review the model.

The EU is in discussions with Anthropic about access, but Regnier noted these talks are at a "different stage" than those with OpenAI. Neither OpenAI nor Anthropic has commented publicly on the matter.

Limited rollout for cybersecurity review

GPT-5.5-Cyber represents a specialized variant of OpenAI's latest model line, specifically designed or adapted for cybersecurity applications. The limited preview rollout restricts access to vetted cybersecurity teams, suggesting heightened concerns about potential misuse.

The European Commission's request for preview access reflects growing regulatory scrutiny of AI models with potential security implications. "This will allow us to follow deployment of the model very closely, and address security concerns," Regnier said.

What this means

The divergent approaches from OpenAI and Anthropic reveal different strategies for handling regulatory engagement on sensitive AI capabilities. OpenAI's proactive engagement with EU regulators contrasts with Anthropic's month-long delay in providing access, despite Mythos apparently raising more immediate security concerns. This dynamic could influence future AI regulation in Europe and set precedents for how AI labs coordinate with governments on models with dual-use potential. The EU's emphasis on preview access suggests regulators are moving toward more active oversight before models reach wide deployment.