London-based AI infrastructure startup Callosum has raised a $100m seed round led by Atomico, with backing from Plural and the UK Sovereign AI Fund. Founded in 2024 by Cambridge PhD graduates Danyal Akarca and Jascha Achterberg, Callosum offers a platform that routes AI workloads across multiple models and hardware providers instead of relying on single systems.

The company is the first recipient of funding from the UK Sovereign AI Fund, part of the government’s effort to boost domestic AI capabilities. Callosum has also been included in the UK’s £1.1bn AI hardware initiative aimed at supporting homegrown chip companies.

Alongside the funding, Callosum announced partnerships with AI hardware firms including US-based Cerebras and South Korean startup Rebellions. The startup also launched a new 'programmable heterogeneity' platform that splits AI workloads into smaller tasks and assigns them to the most suitable model and processor.

The raise is among the largest seed rounds for a European AI infrastructure startup, highlighting strong investor interest in foundational AI technologies.