London, United Kingdom
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£158K–£358K/yr
Estimate — the employer hasn't published pay.
Based on 11 similar staff/principal Software Engineering jobs in United Kingdom that show pay. The range is the middle half of their posted pay (25th to 75th percentile), not an offer — ask the employer for the real range.
Software Engineering salaries →About Us
We’re living through a Cambrian explosion of intelligence: new models and new chips, each specialised for different tasks, are arriving all at once. The result is a new era for AI, one of radical heterogeneity.
Callosum is the Intelligent Systems Company. We believe the next generation of AI won't be defined by any single model or chip, but by intelligent systems in which hardware and intelligence co-evolve. We are building the infrastructure that unifies heterogeneous compute across the full stack. This opens a new axis of scaling intelligence: a dynamic system that tailors itself to what each workload actually needs, whether that's speed, cost, precision, or whatever unit comes next.
The last era scaled on a different bet: one bigger model, more of the same chip, more data. That bet is running into structural limits. Frontier models offer extraordinary capability at unsustainable cost, one that today's monolithic infrastructure was never designed to serve.
Our founding principle is that intelligence comes from many specialised systems working together, not from any single component. We build the software orchestration layer that co-evolves models, workflows and silicon into one system, delivering inference tailored to every workload, and demonstrating orders-of-magnitude leaps in capability and cost.
Because our software spans the full stack, our engineering team works directly with heterogeneous accelerators and frontier silicon, including Cerebras, d-Matrix, Intel, NVIDIA, AMD, Normal Computing, Tenstorrent, GreatSky, and Mixx. We are not stopping at today's chips: each new generation of silicon unlocks algorithms that couldn't run before, and we intend to be first to them, every time. If we get it right, it will belong to everyone building on it - not to any single vendor.
In our latest funding round, we raised $100M, led by Atomico with participation from Plural, DCVC and the UK Sovereign AI Fund’s first investment. With this, we are building the infrastructure for the next era of intelligence.
We are engineers and scientists based in London, working 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.