Anthropic has expanded its Glasswing partner programme fourfold, inducting 150 new organisations including the first non-US members, while UK banks have notably been excluded. OpenAI has moved to fill the gap by offering UK financial institutions access to GPT-5.5. The development highlights growing competitive dynamics in enterprise AI access and raises questions about supply chain concentration risk for financial sector security teams.

Architect’s Take: Cloud security architects in UK financial services should assess the security posture, data residency commitments, and compliance certifications of any AI provider they are offered as an alternative — do not treat OpenAI’s GPT-5.5 access as a like-for-like replacement for Anthropic without conducting due diligence on API security controls, data handling agreements, and regulatory alignment with FCA/PRA expectations.

Original advisory: UK banks offered access to OpenAI’s GPT-5.5 amid exclusion from Anthropic’s Glasswing expansion