Callosum develops system-level software that allows different AI chip architectures to interoperate, enabling flexible, sovereign AI infrastructure.
About Us The last era of AI scaled on a single bet: bigger models, more identical chips, more data. As problems grow more complex and the requirements of intelligence more diverse, that bet is breaking down. Real-world problems are heterogeneous: no single model or chip can solve them alone. The next era of AI requires heterogeneity at the infrastructure level - diverse models on diverse chips, each with distinct strengths, co-evolving into systems of capability that move the Pareto frontier of what is possible. That's what we are building. Callosum is the Intelligent Systems Company. We started from questioning what actually creates intelligence. We believe there is no single answer, but rather a system-level solution. We co-evolve models, workflows, and silicon together to show that intelligence does not come from a single component, but it emerges from the diversity of co-optimised mechanisms working together and aware of each other. Heterogeneity will define the next era of compute, and is a principle that holds in biological, neuronal, and economic systems alike. In early 2026 we launched with results showing orders of magnitude improvements in performance, and this is only the beginning. Agentic AI is the future of how intelligence is deployed: multi-step, long-horizon, and operating in changing environments. These systems are inherently heterogeneous, and can only be as powerful as the infrastructure that runs them. We are engineers and scientists based in London, working together across the full depth of the stack. We are curious, intellectually honest, and building what doesn't exist yet. If you thrive on uncharted territory and are energised by the scale of the challenge, we'd love to hear from you. About the Role Callosum believes that orders of magnitude improvements in AI systems will come through application-aware orchestration across heterogeneous hardware. We are building that vision: infrastructure that treats the full landscape of compute as a unified, co-evolving system. Callosum is purposefully placed to be the first place to access and deploy new chips, expanding beyond GPUs to enable a system that works in harmony, greater than the sum of its parts. This role sits at the foundation of Callosum’s stack, enabling the company to run AI workloads beyond the constraints of any single hardware vendor. You will build the low-level systems software - kernels, drivers, runtime tools - that make diverse and novel accelerators viable for real-world inference, surfacing the full strength of new silicon. This infrastructure is what enables us to turn a fragmented accelerator landscape into our platform; you will own the design decisions that directly influence performance and reliability. What You'll Build - Build and maintain kernels, device drivers, and firmware for heterogeneous accelerators - Design and implement accelerator scheduling at the execution level — kernel launches, dataflow optimisation, and resource management across diverse hardware - Optimise execution paths for latency, throughput, and resource utilisation across accelerator types - Work closely with internal teams and hardware vendors to onboard new accelerator platforms - Contribute to low-level runtime software that bridges our inference stack and the underlying hardware What Sets You Apart - Demonstrable interest in a variety of accelerator microarchitectures - Deep experience in kernel development, device driver authoring, or firmware engineering - Familiarity with accelerator programming models (CUDA, ROCm, or vendor-specific SDKs) - Experience with compiler infrastructure such as MLIR or LLVM - Strong debugging skills in environments with limited tooling and incomplete documentation 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.