Atomico led the round, with participation from Plural, DCVC and the U.K. Sovereign AI Fund. The company previously raised $10.25 million in February. Callosum’s Tailored Inference service helps developers increase AI efficiency by breaking tasks into blocks and routing them to the best model.
The platform claims to complete inference tasks 3.7 times faster than GPT-5.6 Luna while reducing infrastructure costs. Callosum also announced a partnership with Cerebras Systems Inc., which will integrate its WSE-3 Turbo wafer-size accelerators into the service.