Accelerator Systems Software
Callosum
Accelerator Systems Software
Callosum
Orchestrates AI workloads across specialized silicon
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.
Callosum believes that orders of magnitude improvements in AI systems will come through application-aware orchestration across heterogeneous hardware. We are building infrastructure that treats the full landscape of compute as a unified, co-evolving system. Realising this requires going beyond the software assumptions of conventional accelerators, exposing the capabilities of emerging silicon through performant, flexible execution primitives.
This role sits at the foundation of Callosum's stack, enabling AI workloads to run efficiently across diverse and novel accelerators. You will extend the low-level software, kernels, and runtime components needed to bring models onto new hardware, optimise their execution, and make accelerator capabilities accessible to the rest of our platform. Working across systems programming, compiler technologies, and hardware architecture, you will help turn emerging silicon into practical, high-performance compute resources.
Design, implement, and tune high-performance kernels and compute primitives that exploit the capabilities of new hardware.
Extend low-level runtime components, drivers, and execution interfaces that expose accelerator capabilities to our inference stack.
Work closely with hardware vendors to benchmark, integrate, and optimise emerging accelerator platforms.
Explore compiler technologies and code-generation techniques to optimise operations for different accelerator architectures.
Bring up AI models on new hardware, developing the software needed for efficient execution.
Deep experience in kernel development, accelerator programming, or low-level systems software.
Strong understanding of accelerator microarchitectures and the relationship between hardware capabilities and computational performance.
Experience optimising compute kernels or bringing up ML workloads on GPUs, ASICs, or other accelerators.
Familiarity with accelerator programming models, compiler infrastructure, or code-generation frameworks such as CUDA, ROCm, MLIR, or LLVM.
Strong debugging and performance engineering instincts, particularly when working with unfamiliar hardware and immature software stacks.
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.
Callosum builds AI infrastructure that unifies different AI models and hardware chips to run workloads on the best combination of model and chip for each task. Its Tailored Inference APIs route tasks to the optimal model–chip pair while honoring cost, energy, and latency constraints, using partners like Cerebras and Rebellions for specialized silicon. Unlike approaches that rely on one model and uniform hardware, Callosum orchestrates multiple models and chips to maximize efficiency. The company's goal is to enable scalable, cost-efficient AI inference across heterogeneous hardware by intelligently matching tasks to the right combination of model and accelerator.
Explore more opportunities at Callosum