OpenAI opens GPT-5.5 Cyber to British banks amid Mythos access battle
OpenAI has offered 9 major UK banks access to its cybersecurity-focused GPT-5.5 Cyber model, as lenders remain unable to test their systems using Anthropic’s rival Claude Mythos despite concerns about the security of aging banking code.
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OpenAI steps in: OpenAI is offering nine major UK banks access to its new GPT-5.5 Cyber model for security testing.
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Anthropic remains restricted: UK banks are still unable to access Anthropic’s rival bug-hunting AI, Claude Mythos, which is currently limited to select partners.
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Legacy code fears: The financial sector is urgently seeking these AI tools to uncover hidden vulnerabilities in their aging, complex software systems.
The development comes months after Anthropic unveiled Mythos, a bug hunting model designed to uncover hidden flaws in software.
The maker of Claude claimed that the system identified a vulnerability in a legacy system that was decades old – prompting concern among financial regulators and central bankers.
The banking sector is worried because some of the code which their systems run on is old and has had to be modified repeatedly over time, creating complex environments that can be difficult for security teams to review comprehensively.
Despite this concern, the Bank of England governor Andrew Bailey, who chairs the Financial Stability Board, said last week that UK banks could still not access Mythos, despite discussions with Anthropic.
So far, only selected partners participating in Anthropic’s Project Glasswing – mainly other big tech firms – have been using Mythos.
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However, as Anthropic is reported to be readying Mythos for an enterprise release, its rival OpenAI appears to be ramping up its relationships with the UK’s globally-renowned financial sector.
According to the BBC, HSBC, Lloyds Banking Group and Nationwide are among the lenders set to receive access to GPT 5.5 Cyber. NatWest and Santander already have access through existing agreements.
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