Chief of Staff, CTO in London

About Us

We’re living through a Cambrian explosion of intelligence: new models and new chips, each specialised for different tasks, are arriving all at once. The result is a new era for AI, one of radical heterogeneity. Callosum is the Intelligent Systems Company. We believe the next generation of AI won't be defined by any single model or chip, but by intelligent systems in which hardware and intelligence co-evolve. We are building the infrastructure that unifies heterogeneous compute across the full stack. This opens a new axis of scaling intelligence: a dynamic system that tailors itself to what each workload actually needs, whether that's speed, cost, precision, or whatever unit comes next.

The last era scaled on a different bet: one bigger model, more of the same chip, more data. That bet is running into structural limits. Frontier models offer extraordinary capability at unsustainable cost, one that today's monolithic infrastructure was never designed to serve.

Our founding principle is that intelligence comes from many specialised systems working together, not from any single component. We build the software orchestration layer that co-evolves models, workflows and silicon into one system, delivering inference tailored to every workload, and demonstrating orders-of-magnitude leaps in capability and cost.

Because our software spans the full stack, our engineering team works directly with heterogeneous accelerators and frontier silicon, including Cerebras, d-Matrix, Intel, NVIDIA, AMD, Normal Computing, Tenstorrent, GreatSky, and Mixx. We are not stopping at today's chips: each new generation of silicon unlocks algorithms that couldn't run before, and we intend to be first to them, every time. If we get it right, it will belong to everyone building on it - not to any single vendor.

In our latest funding round, we raised $100M, led by Atomico with participation from Plural, DCVC and the UK Sovereign AI Fund’s first investment. With this, we are building the infrastructure for the next era of intelligence.

We are engineers and scientists based in London, working across the full depth of the stack. We are curious, intellectually honest, and building what doesn't exist yet. If you thrive on uncharted territory and are energised by the scale of the challenge, we'd love to hear from you.

About the Role

Callosum works with a global network of partners - chip makers, OEMs, neoclouds, hyperscalers - and integrates them into our infrastructure with the technical and commercial insight to make each partnership genuinely additive, not just another vendor relationship. The CTO and Head of Heterogeneous Infrastructure lead that work directly: partner engagement, technical delivery, roadmapping. For it to hold together, every technical vertical needs visibility into what the others are doing.

This role sits operationally between those teams. You'll have visibility into the partnerships and the technical roadmap, and the job is translation: surfacing what matters, at the right level of abstraction, so team leads can act on it directly - then building the tools and cadence that let that translation scale as the organisation grows.

This is an early hire into a function that doesn't yet exist. A meaningful share of the initial work is close support - staying near enough to the technical and commercial detail that nothing falls through, and turning what the CTO and Head of Infrastructure are already doing into operating infrastructure. From there, the role has real room to grow: spotting where the partner network creates genuine new commercial opportunity versus noise, and increasingly owning the commercial strategy behind the infrastructure org.

What You'll Own

• Sit operationally between the technical teams and the partnerships network, translating insight at the abstraction level team leads can act on
• Turn the CTO's priorities into clear, measurable company goals, and drive cross-functional roadmap execution
• Build and run the operating cadence for the infrastructure org - OKRs, ownership mapping, meeting cadence, how information moves
• Provide close day-to-day support to project leads, representing them in select internal and external meetings and following decisions through to close
• Own reporting across the executive team on what the partnership network is surfacing
• Act as a primary point of contact for the CTO, internally and externally, ensuring alignment holds after the meeting ends

What You'll Bring

• Compute infrastructure literacy - you know what information actually matters and needs to move between team leads
• Technical-commercial fluency, with a track record operating between engineering and the commercial or capital side - dated milestones, acceptance criteria, a roadmap that holds
• Experience through a genuine high-growth phase at a larger organisation, and the judgment to apply those lessons to Callosum's current inflection point
• Comfort with a broad, foundational remit - setting things up from nothing, supporting other executives, and going wherever the company needs you

What Sets You Apart

• Prior experience as chief of staff, GM, or similar to a technical leader specifically, not a generalist executive-support role
• Background in semiconductor, hardware, or infrastructure partnerships
• Experience building this kind of function from the first hire, at a company operating at a similar stage or velocity

What We Offer

• Competitive Salary, determined by skills and experience
• Equity & Ownership
• Private healthcare
• We offer Visa sponsorship and relocation benefits to hire the best in the world
• We work in person at our London office. You'll have the tools, space and setup to do your best work, and if you have specific needs, just tell us
• We're committed to building an inclusive workplace where everyone feels welcome, and believe in equal opportunities for all.