This version of GPT-5.4 lowers the refusal boundary for ‘legitimate’ cybersecurity work, OpenAI said.

OpenAI said it will only allow select verified users access to its latest AI model for cybersecurity operations, a week following the limited launch of Anthropic’s Mythos.

Purpose-built for security operations, the new GPT-5.4-Cyber will be accessible to users willing to work with OpenAI to authenticate themselves as cybersecurity defenders, the company said.

This version of GPT-5.4 lowers the refusal boundary for “legitimate” cybersecurity work. As a “more permissive” model, OpenAI said it is beginning by deploying GPT-5.4-Cyber to “vetted” security vendors, organisations and researchers.

The ChatGPT-maker only began integrating cyber-specific safeguards into its model deployments in 2025, and launched Codex Security⁠ to identify and fix vulnerabilities in March. In February, it introduced the Trusted Access for Cyber framework⁠ as a way to verify the identities of cybersecurity workers.

Anthropic’s new Mythos model showcases significant capabilities of detecting and generating security exploits. Concerned about bad actors, Anthropic made the choice to offer Mythos to a group of  more than 40 big businesses to boost their cyber defences.

Mythos’ reported capabilities have already raised concern with global leaders. Yesterday (14 April), the National Cyber Security Centre director told the Oireachtas Joint Committee on AI that more models such as Mythos should be expected at the hands of bad actors before the end of the year.

Anthropic’s co-founder and policy lead Jack Clark had similar beliefs. “There will be other systems just like this in a few months from other companies, and then a year to a year-and-a-half later, there’ll be open weight models from China that have these capabilities,” he told the audience at the Semafor World Economy event in Washington DC earlier this week.

OpenAI, which has plans for an initial public offering later this year, has been attempting to narrow focus into the enterprise market – a sector being quickly captured by Anthropic. According to data from payments group Ramp, nearly one in three US business paid for Anthropic’s tools in March.

The company has been shedding less lucrative projects, including “indefinitely” pausing plans for an erotic ChatGPT and putting Stargate UK on hold.

OpenAI’s biggest backer Microsoft, meanwhile, has agreed to rent data centre capacity at a site intended for the Stargate Norway project, as yet another one of OpenAI’s deals with UK AI infrastructure Nscale fails to take off.

Competition between the two companies has escalated, with the announcement of a new Anthropic-inspired ‘superapp’ by OpenAI, or a dedicated set of AI health tools by Claude launched just days after OpenAI released ChatGPT Health.

Despite pausing plans for a Stargate UK, OpenAI said it is opening its first permanent office in London in 2027 with a capacity of more than 500 people. The company plans to make London its largest research hub outside of US, it said.

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