About Us

Artificial intelligence scaled on a bet - that bigger models, more identical chips, and more data would keep delivering. As problems grow more complex and the requirements of intelligence more diverse, that bet is breaking down. The next era belongs to heterogeneous intelligence: diverse models on diverse chips, each with distinct strengths, co-evolving into systems of capability unreachable by any single model or accelerator.

Callosum is the Intelligent Systems company. We built the infrastructure to make that possible. Our co-evolution engine optimises simultaneously across workflows, agents, and silicon. We launched in early 2026 showing orders of magnitude improvements in performance and a shift in the cost-performance frontier that no single chip or model provider can provide.

We believe intelligence comes from the system, not the model.

We are scientists and engineers solving what others consider impossible. If you thrive on hard problems, and are passionate and energised by the scale of the challenge, we'd love to hear from you.

About the role

Our customers run some of the most demanding inference workloads in the world. Their hardest problems are the ones that justify the existence of heterogeneous intelligence in the first place - workloads where frontier monolithic models are too slow, too expensive, or too imprecise to be the right answer. Finding those problems, understanding them deeply, and turning them into systems we can build is the work of this role.

You will sit close to a small number of enterprise customers and become the engineer who understands their workloads better than anyone else at Callosum. You will translate what you learn into precise architectural problems for the team that designs new intelligent systems, prototype against real customer data and traffic, and stay with each system through the arc of integration, validation, and production rollout.

The role is engineering-led, you will employ technical judgment to recognise what kind of system a problem needs, the rigour to prototype it well, and the experience to know when a solution generalises beyond the customer that asked for it.

You will work closely with the engineers designing new intelligent systems, with the platform team that serves them, and directly with senior technical stakeholders on the customer side.

Who we are looking for

We're looking for engineers who do their best work close to real problems, with real users, under real constraints.

• Strong production engineering

• Substantial hands-on experience with modern LLMs - e.g., you have built non-trivial systems on top of them

• Strong communication skills to be the technical face of Callosum to a sophisticated customer.

• Comfort moving fast in unfamiliar domains: every customer is a new problem

What Stands Out

• Direct experience as a forward-deployed, solutions, or applied engineer at a company shipping serious technical product into enterprise environments.

• A track record of building things that started as one customer's problem and became part of a product.

• Domain depth in any vertical with heavy inference workloads - finance, code, search, healthcare, agentic platforms.

• Open-source work, research publications, or production systems whose scale and complexity you can speak to in detail.

What We Offer

• Competitive Salary, determined by skills and experience

• Equity & Ownership

• Private healthcare

• We offer Visa sponsorship and relocation benefits to hire the best in the world

• We work in person at our London office. You'll have the tools, space and setup to do your best work, and if you have specific needs, just tell us

We're committed to building an inclusive workplace where everyone feels welcome, and believe in equal opportunities for all.