Callosum Raises $100M for AI Workload Optimization

London-based AI startup Callosum has raised $100 million in funding led by Atomico, with participation from Plural, DCVC, and the U.K. Sovereign AI Fund. The round follows a $10.25 million raise in February. Callosum's cloud service, Tailored Inference, breaks AI tasks into modular steps and routes each to the most suitable model and chip, claiming speeds 3.7 times faster than GPT-5.6 Luna at lower infrastructure costs. Chipmaker Cerebras Systems also announced a partnership with Callosum, integrating its WSE accelerators into the platform.