$100m · Seed · AI · London, UK
London AI infrastructure startup Callosum has raised $100m in seed funding led by Atomico, with significant participation from Plural, DCVC and the UK Sovereign AI Fund, according to the company announcement. DCVC says the capital will help Callosum expand its team, accelerate research and development, and buy compute resources.
Callosum is building a software layer for running complex AI applications across different models and processors. Its Tailored Inference product breaks a workflow into smaller tasks, then assigns each task to a model and chip configuration suited to its cost, speed and capability requirements. The company has announced integrations with Cerebras and Rebellions and says its APIs are already being used in cybersecurity, finance and enterprise applications.
Routing becomes part of the AI product
The commercial premise is that developers should not have to send every step of an AI workflow to the same frontier model on the same hardware. Callosum's published case studies describe systems that combine classical algorithms, smaller open models, frontier models, commodity GPUs and specialised accelerators. In one security workflow with HelmGuard, the company reports configurations designed either for lower cost or faster real-time decisions; with Round Treasury, it says document extraction time fell from 15.9 seconds to 2.1 seconds. These are company-reported results rather than independent benchmarks.
That flexibility matters commercially because increasingly agentic applications can multiply model calls inside a single customer workflow. If routing can cut the cost or latency of each step without reducing useful output, Callosum can sell against a measurable operating expense rather than a broad infrastructure promise. The same mechanism also gives chipmakers another route to customers: specialised processors can be selected for the parts of a workload where they outperform general-purpose hardware.
A large seed round raises the integration bar
Callosum emerged from stealth in February 2026 with a $10.25m pre-seed round led by Plural, making this seed a separate financing event. The founders, Jascha Achterberg and Danyal Akarca, are Cambridge-trained neuroscientists, and the company positions its cross-model, cross-chip orchestration as an alternative to dependence on a single supplier. DCVC's investment note says Callosum is deployed with token-heavy application platforms and is using cloud processors including AWS Trainium and Inferentia alongside direct hardware partnerships.
The round gives Callosum unusual resources for an early-stage company, but the product also carries an unusually broad integration burden. Models, accelerators and cloud services change independently, so the orchestration layer must keep proving that its routing decisions improve real customer workloads as the underlying stack evolves. Repeatable deployments, transparent benchmarks and durable supplier integrations will determine whether heterogeneous compute becomes a scalable platform rather than a collection of bespoke optimisations.
