London-based AI infrastructure startup Callosum has raised $100 million in a seed round led by Atomico with participation from Plural, DCVC and the UK government’s Sovereign AI Fund, which took its first direct equity stake. The round, bringing total funding to approximately $110 million, is accompanied by the launch of the company’s first generally available product — a family of APIs that let enterprise developers run AI workloads across multiple competing chip vendors without rewriting application code. The platform operates through a two-path architecture that analyzes incoming workloads, decomposes them into subtasks and routes each to the optimal chip combination based on latency, accuracy and budget requirements. Available hardware includes Nvidia GPUs, AMD processors, Amazon Trainium and Inferentia, Cerebras, Rebellions, Axelera, d-Matrix and Lumai chips, integrated with partners Supermicro and HPE across AWS, Google Cloud and Microsoft Azure. Benchmarks show 4x faster performance, 70% lower compute costs and 10% higher task success on complex financial-services agentic workloads compared with homogeneous GPU setups. The company was founded in 2025 by Cambridge-trained neuroscientists Danyal Akarca and Jascha Achterberg, whose research examined brain-inspired heterogeneous computing. Plans include scaling the London team, expanding to the US and developing photonics-based interconnects for data centers.