Callosum vs Together AI
Side-by-side comparison of AI visibility scores, market position, and capabilities
Callosum (London) raised $10.25M for multi-vendor AI chip orchestration — unifying GPUs, TPUs, and custom silicon — founded by Cambridge neuroscientists. Feb 2026.
About
Callosum is a London-based AI infrastructure startup founded by Cambridge neuroscientists who applied their understanding of how the brain orchestrates computation across specialized regions to the problem of multi-vendor AI chip coordination. The company's name references the corpus callosum—the brain structure that connects and coordinates the two cerebral hemispheres—reflecting its technical mission: enabling different AI accelerators from different vendors to work together efficiently as a unified compute resource. Callosum addresses a real pain point for enterprises and cloud providers that now operate heterogeneous fleets of GPUs, TPUs, and custom silicon.\n\nCallosum's orchestration platform abstracts over hardware differences between AI chip vendors, allowing workloads to be scheduled and balanced across NVIDIA, AMD, Intel, and custom accelerators without manual optimization for each chip type. This is particularly valuable as enterprises seek to reduce vendor lock-in and optimize cost by mixing and matching hardware. The platform targets ML engineering teams and infrastructure operators at companies running large-scale AI training and inference workloads who need to maximize utilization across a diverse hardware estate.\n\nCallosum raised $10.25M in February 2026 in a seed or early-stage round, providing capital to build out its engineering team and deepen integrations with major chip platforms. While early in its journey, the company operates at a genuinely important intersection: as AI chip diversity grows and no single vendor dominates all workloads, the need for intelligent multi-vendor orchestration will only increase. Callosum's neuroscience-rooted technical vision and Cambridge pedigree give it a distinctive angle in the competitive AI infrastructure space.
Open-source AI cloud. $300M ARR (Sep 2025). $3.3B valuation. $533M total raised. Backed by Salesforce, NVIDIA, Kleiner Perkins. Founded by ex-Stanford AI researchers.
About
Together AI was founded in 2022 with a mission to build the leading open-source AI cloud—a platform where developers and enterprises can train, fine-tune, and run inference on open-weight models without the constraints and costs of proprietary AI APIs. The company recognized early that as powerful open-weight models like Llama, Mistral, and FLUX proliferated, there was a massive opportunity to provide optimized infrastructure for running and customizing them. Together AI built a multi-cloud GPU platform with custom inference kernels and distributed training optimizations specifically engineered for open-source models.\n\nTogether AI's platform offers fine-tuning, inference, and training services across a curated library of leading open-weight models, with performance-optimized endpoints that often outperform what users can achieve running models on general-purpose cloud infrastructure. The company targets AI engineers, ML researchers, and enterprises that want flexibility—either for cost reasons, privacy requirements, or the need to customize model behavior through fine-tuning. Together's API design closely mirrors OpenAI's, making migration straightforward. Its pricing is consistently below proprietary model APIs for comparable capability tiers.\n\nTogether AI has achieved $300M in annualized revenue as of September 2025, growing to a $3.3B valuation with $533M in total funding. Investors include NVIDIA, Salesforce, and Kleiner Perkins—a combination that provides both strategic GPU supply chain relationships and enterprise go-to-market leverage. The open-source AI cloud market is a significant and growing segment as enterprises prioritize model flexibility and cost control alongside the maturation of open-weight models that increasingly compete with frontier proprietary models.
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