Cosine has formed a coalition with leading UK institutions to build Lumen Sovereign: Britain's first fully sovereign frontier AI for critical sectors.
Today, Cosine announces the formation of a landmark industry coalition to co-design Lumen Sovereign, Britain’s first fully sovereign frontier AI model.
With input from some of the UK’s largest and most critical institutions – including BAE Systems, Babcock International Group, BT, Era4, HSBC, Leonardo, Lloyds Banking Group, LSEG, NatWest Group, PwC, Telefónica Tech UK&I, Thales UK, and The Alan Turing Institute – Cosine is building an AI capability that operates with zero dependence on foreign infrastructure.
Backed by the UK Government’s £500m Sovereign AI programme, Lumen Sovereign will be trained entirely on UK soil using Isambard-AI, one of Europe’s most powerful supercomputers.
Breaking the dependency risk in AI
For regulated sectors, AI has evolved from a productivity tool into a critical strategic dependency. Until now, the UK’s defence, financial, and public sector institutions have faced a difficult choice: either fall behind in AI adoption or rely on models trained and operated overseas, which can ultimately create unacceptable operational and sovereignty risks.
A sovereign LLM provides strategic advantages beyond avoiding dependency, including the ability to operate in high-security, air-gapped environments for complete domestic data control. This assurance-by-design is often non-negotiable in regulated sectors, ensuring alignment with specific governance standards and UK/Europe-specific regulatory requirements. Furthermore, it offers a competitive advantage by providing crucial cost protection against vendor lock-in and price escalations from expensive foreign-built APIs.
By signing a memorandum of understanding, Cosine and the coalition of industry leaders are taking an active role in establishing a foundational framework for the co-definition of Lumen Sovereign's use-case parameters, rigorous security protocols, and necessary governance standards. This collaborative effort ensures the delivery of a sovereign frontier capability architected from inception to satisfy the stringent assurance requirements of regulated industries.
Technical architecture overview
To deliver Lumen Sovereign by our target of late 2026, Cosine is leveraging its allocation of UK sovereign compute to take a known-good Mixtue-of-Experts (MoE) architecture and upcycle it to a larger overall parameter and active parameter count, and proceed with the main stages of training (pre, mid, and post). Cosine’s engineering focus is on rapid, high-impact capability scaling:
- Applying continual pre-training and expert expansion to the 256k-context sparse MoE architecture, targeting a long-horizon agentic coding model within a 500,000 GH200 GPU-hour compute budget
- Enhancing the MoE architecture for highly specialised, domain-specific reasoning
- Implementing lightweight instruction recovery so the model maintains state-of-the-art proficiency in coding, tool use, and complex agentic workflows
Purpose-built for high-stakes workflows, Lumen Sovereign will be designed to tackle workflows where the combination of sensitivity and complexity has historically made AI adoption impossible.
The training regimen is strategically allocated, dedicating approximately one-third of the total compute time to optimising performance on complex software engineering problems, with the remaining two-thirds focused on broader, mission-critical use cases such as cybersecurity adversarial testing, KYC and AML alert investigations, and clinical trial coordination.
When complete, Lumen Sovereign will be capable of deployment entirely within a customer’s own infrastructure – including fully air-gapped environments – with absolutely no external data transfer required.
Perspectives from the coalition
Alistair Pullen, CEO & Co-Founder, Cosine
"AI is the single most important technology of our generation. Enterprises are increasingly waking up to the risk of being wholly dependent on foreign providers for this technology. Vendor lock in creates security risk, dependency risk and cost escalation risks. Cosine is addressing those risks by building a model that is fully trained on UK soil and available into air gapped environments at a far more efficient price point than OpenAI and Anthropic alternatives.”
Chris Keon, Director of Group Innovation, BT Group
"As AI becomes a foundational technology for the UK economy, our customers need confidence that the systems they depend on are secure, trusted and aligned with their requirements. As the UK’s leading connectivity provider, BT is excited to contribute its expertise in digital infrastructure and cyber-security to help shape the next generation of sovereign AI capabilities. This collaboration reflects our belief that innovation is strongest when industry, government and technology partners come together to build the foundations for future."
Dr. Peter Passaro, Global Director AI & Data, Babcock International Group
“As we ramp up our AI and Data Centre of Excellence (AIDEX), we are proactively looking to source sovereign AI tooling. Cosine has offered us a path to a completely UK native and highly customisable AI stack. Together, we can co-create and design AI models that are highly specific for the very complex defence environments we operate in. We are building an ecosystem of UK AI startups that can support our own in house capabilities, which together will play a critical role in supporting our national digital infrastructure. Cosine is a key part of that ecosystem.”
Emily Prince, Group Head of AI, LSEG
“AI adoption in regulated industries depends on trusted data, strong governance and secure deployment in the environments where institutions operate. This initiative aligns with LSEG’s AI strategy, making trusted AI available responsibly and at scale across the workflows our customers use every day.”
Graham Smith, Head of AI, NatWest Group
“The UK has strong foundations in AI, and this is an opportunity for us to help shape its future in a way that is responsible and focused on real customer needs. We’re prioritising using AI to improve how we serve customers and enhance how our colleagues work, and by collaborating with partners in the UK and overseas we can help develop AI that makes a real difference for customers and businesses across the UK.”
Robert Merryweather, Group Technology Director, BAE Systems
"Lumen Sovereign provides an encouraging example of innovation in practice - applying cutting-edge technology to critical sectors while strengthening the UK’s sovereign AI capability. Working with start-ups such as Cosine presents an important opportunity to support innovation across the defence ecosystem, while positioning BAE Systems at the forefront of adoption. This collaborative approach helps to nurture a more dynamic and resilient UK industrial base."
Making Britain an AI maker
By bringing together the backbone of UK critical infrastructure to co-design Lumen Sovereign, we are taking a massive step towards technological independence, ensuring that Britain remains an AI maker, not just an AI taker.