UK AI Startup Callosum Raises $100M, Pairs With Cerebras to Challenge NVIDIA

British AI startup Callosum has raised a $100 million seed round led by Atomico with participation from the UK's £500 million sovereign AI fund, and announced a partnership with chipmaker Cerebras. Founded by two Cambridge neuroscientists in 2025, Callosum builds software that routes specific AI tasks to the best-fit model and chip, lowering compute cost without relying on NVIDIA's most powerful GPUs. Cerebras CEO Andrew Feldman said integrating its CS-4 rack-scale system lets ultra-low-latency inference be applied exactly where it pays off. Callosum has also signed deals with Korea's Rebellions and the Netherlands' Axelera AI.