Callosum

AI Infrastructure · Semiconductors · Cloud Computing

Funding

Callosum raises $100M seed led by Atomico for AI compute routing

Inference workloads increasingly span mismatched chip architectures, turning smart routing into a scarce competitive advantage.

• Callosum, a London-based AI infrastructure startup, raised a $100M seed round led by Atomico, with Plural, DCVC and the UK Sovereign AI Fund also participating.
• Founded by Cambridge-trained researchers Danyal Akarca and Jascha Achterberg, Callosum builds software that routes AI workloads across different models and chip architectures instead of locking developers into one system.
• The seed follows a $10.25M pre-seed led by Plural in February 2026, backed by the UK's Advanced Research + Invention Agency, bringing Callosum's total funding to roughly $110M within about a year of founding.
• Callosum unveiled 'programmable heterogeneity,' a platform that breaks AI workloads into smaller tasks and assigns each to whichever model and processor suits it best.
• Callosum became the first company funded by the UK's Sovereign AI initiative and was named in Britain's £1.1bn plan to strengthen domestic AI chip capability.
• Alongside the raise, Callosum announced partnerships with US chipmaker Cerebras and South Korean semiconductor startup Rebellions to widen the hardware its routing platform can support.
• The size of the round signals growing investor conviction that as AI shifts from training to inference, squeezing efficiency from scarce, varied chip supply is as valuable as building models themselves.