Callosum raises $100M to match AI workloads to the right chip

Callosum, a London AI-infrastructure company, has raised $100M, about £79M, in what is being called one of the largest seed rounds ever raised in Europe. The round was led by Atomico, with Plural, DCVC, and the UK’s Sovereign AI fund taking part. The company was founded by Danyal Akarca and Jascha Achterberg, two neuroscientists who met during their PhDs at Cambridge and had collaborated with Google DeepMind.

What Callosum builds sits between an AI application and the hardware it runs on. Rather than sending a whole job to a single type of chip, its software breaks each workload into its component tasks and routes every one to the model and chip best suited to it. The pitch is an escape from what the founders call the “AI monoculture”, the heavy reliance on one company’s chips, and the payoff is meant to be lower cost and less energy. On financial-services workloads the company says it has run four times faster at around 70% lower cost, and it already works across the big clouds, AWS, Google, and Microsoft.

This is a company we have crossed paths with before. Callosum was the first equity investment made by the UK’s Sovereign AI programme, which is why the fund appears again here. It came out of stealth in February with a $10.25M round, so a $100M raise six months later is a striking vote of confidence, and a sign of how central the economics of running AI have become. It sits alongside a growing British cluster working on the physical layer of AI, from the data-centre firms Nscale and FluidStack to the chip designer OLIX.

The reason this matters goes back to cost. Training and running modern AI is enormously compute-hungry, and most of that compute happens on a single vendor’s chips, which keeps prices high. Software that spreads work across different chips and models, and sends each piece of inference to the cheapest option that can do the job well, is one of the clearer routes to bringing that bill down. Whether Callosum can deliver that at scale is the open question, but the size of this round shows how much investors want the answer to be yes.