Job title: Applied ML Technical Lead, Defence

Location: London; full in-office working as default

Start date: ASAP

Reports to: CEO

Compensation: Salary and Equity options available for discussion

Clearance: Must be eligible to hold UK Security Vetting Clearance SC or above (no prior clearance required)

Application Deadline: 08/11/26 at 23:59 UK Time

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Help put frontier AI to work in Defence

Cosine is a UK AI lab building models, applications and training infrastructure for mission-critical organisations.

We build coding agents that work across real software systems, specialised Lumen models, AI-native security products and the infrastructure needed to deploy advanced AI in demanding environments. Our customers include some of the world's largest enterprises, including organisations operating behind strict security, regulatory and technical constraints.

We're also training Lumen Sovereign, the first frontier large language model trained in the UK, with the support of the UK Government.

We're now looking for an Applied ML Technical Lead to help develop and deploy advanced AI capabilities for organisations operating in UK Defence and national security.

This is a hands-on technical leadership role. You will work across machine learning development, deployment and customer-facing technical delivery. You may spend part of your time training and evaluating models on complex sensor data, and part of your time working with Defence stakeholders to understand operational needs, shape priorities and guide delivery.

You will not be expected to act as a traditional project manager. Instead, you will own the technical direction and day-to-day progress of applied ML work, coordinating the people and decisions needed to turn promising research into useful operational capability.

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What you'll do

• Build ML capabilities for real Defence problems

• Design, build, train and evaluate machine learning models for challenging applied Defence and national security use cases.

• Work on problems involving complex sensor data, signal processing, pattern recognition, classification and multimodal intelligence.

• Develop and improve model architectures, training pipelines, evaluation frameworks and inference systems.

• Work with real-world and synthetic datasets to improve model accuracy, robustness and generalisation.

• Translate research prototypes into reliable, deployable capabilities that operate within demanding technical and security constraints.

• Work closely with Cosine's ML research and engineering teams while taking direct ownership of technical outcomes.

Lead technical delivery from prototype to deployment

• Own the technical direction and day-to-day progress of applied ML projects.

• Turn operational objectives into concrete technical goals, experiments, milestones and success measures.

• Coordinate work across ML researchers, software engineers, infrastructure teams and external stakeholders.

• Identify technical dependencies, delivery risks and blockers, and help drive them to resolution.

• Establish clear evaluation criteria and demonstrate progress through measurable improvements and working capabilities.

• Balance hands-on engineering with the planning and coordination needed to keep complex technical work moving.

Work directly with Defence customers

• Engage with technical and operational stakeholders across the UK Defence and national security ecosystem.

• Understand operational challenges and identify where machine learning can make a meaningful difference.

• Translate customer requirements and constraints into technical objectives, datasets, experiments and delivery plans.

• Present technical progress, demonstrate working capabilities and communicate results clearly to technical and non-technical audiences.

• Build trusted relationships with Defence stakeholders and act as a credible technical counterpart.

• Help customers understand the practical considerations of integrating and deploying ML systems in their existing environments.

Turn research into operational capability

• Help deploy ML models into real-world environments, including secure, on-premise and resource-constrained systems.

• Work on model optimisation, inference performance, integration and reliability.

• Develop robust approaches to evaluation, validation and continuous model improvement.

• Understand data availability, access requirements, security restrictions and deployment constraints.

• Establish feedback loops between operational users and Cosine's engineering teams.

• Ensure that what we build is not only technically impressive, but genuinely useful to the people relying on it.

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What we’re looking for

You'll probably have a background in applied machine learning, ML engineering, research engineering or a similarly technical role, along with experience taking ownership of complex technical work.

You should be comfortable:

• Writing production-quality Python and working with modern ML frameworks such as PyTorch.

• Building, training, fine-tuning and evaluating machine learning models.

• Working with complex datasets, designing experiments and interpreting model performance.

• Understanding the trade-offs between model performance, compute requirements, latency and deployment constraints.

• Working with engineering infrastructure, including Git, containers, Linux and GPU compute.

• Taking technical ownership of projects with multiple stakeholders, uncertain requirements and evolving priorities.

• Communicating technical concepts clearly to researchers, engineers, senior stakeholders and operational users.

• Moving between model development, customer discussions and delivery planning without losing technical depth.

• Making sound technical judgements, prioritising effectively and finding practical solutions when the path forward is unclear.

• You don't need to have worked in Defence before. You do need to be excited by the opportunity to apply advanced ML to difficult, consequential real-world problems.

Nice to have

• Existing UK security clearance, such as SC or DV, or previous experience working in secure Defence environments.

• Experience with signal processing, time-series data, sensor fusion, representation learning or machine learning applied to complex real-world datasets.

• Experience with foundation models, multimodal learning or advanced model training and post-training techniques.

• Experience deploying ML models to edge devices or constrained compute environments.

• Familiarity with UK Defence procurement, technical assurance or the national security landscape.

• Experience leading technical workstreams or working as a technical lead on customer-facing ML projects.

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What success looks like

In your first three months, we would expect you to:

• Become the technical lead for a major applied Defence ML programme, with responsibility for its day-to-day technical progress.

• Build strong working relationships with Cosine's ML researchers, engineers and key Defence customer stakeholders.

• Develop a clear understanding of the existing models, datasets, technical architecture and operational objectives.

• Establish a focused delivery plan with clear priorities, milestones, ownership and success measures.

• Make meaningful hands-on contributions to model development, evaluation or deployment.

• Identify and begin addressing the most important technical and operational blockers.

• Demonstrate tangible progress to customer stakeholders and build confidence in Cosine's ability to deliver.

• Longer term, you'll help take advanced ML capabilities from promising prototypes into operational use, while shaping how Cosine builds and delivers applied AI for Defence and other mission-critical organisations.

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Why this role matters

Some of the most important applications of AI won't be found in consumer products. They'll be in environments where information is incomplete, systems are complex, security matters and the consequences of getting things wrong are significant.

Cosine is working to bring frontier machine learning into those environments.

Doing that requires more than good models. It requires people who can understand an operational problem, build something that works, make good technical decisions, coordinate the work needed to deliver it and stay close to the customer until it creates real value.

You'll have unusual proximity to cutting-edge ML research, senior Defence stakeholders and the operational challenges that will shape the next generation of AI capabilities.

This role will suit someone who is technically strong enough to build, organised enough to lead technical delivery and curious enough to engage directly with the people using the technology.

If you enjoy being close to the research, close to customers and personally accountable for turning ambitious technology into something real, come and work with us.

Come help make frontier AI useful where it matters most.

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Cosine is an equal opportunity employer.

We value diverse backgrounds, perspectives, and ways of thinking, and we’re committed to creating an inclusive and respectful workplace.

We encourage applications from anyone who meets the role requirements, even if you don’t meet every single qualification. If you need reasonable adjustments at any stage of the hiring process, we’re happy to discuss them.

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Compensation, Benefits & Ways of Working

We’re an in-office team, five days a week, by design. We believe the work we’re doing benefits from being together, collaborating closely, and building shared context.

What you can expect:

• Competitive salary, benchmarked to the market

• Equity / share options, so you share in the upside you help create

• 30 days’ holiday + bank holidays

• Work hard in the office, collaborate closely, and switch off properly

• Dog-friendly office — bring your dog to work

• Weekly team breakfast & lunch

• Monthly socials

• Pension

• High-quality equipment to do your best work

We care about focus, sustainability, and doing great work — not performative overwork. We value people who show up, contribute thoughtfully, collaborate well with their colleagues, and then go home.

This role won’t suit everyone. But if you’re looking for a fast-moving environment, close collaboration, and a team that takes both the work and work-life balance seriously, it’s a great place to be.

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Agency & Data Protection Notice

To comply with UK GDPR and our internal data-protection and equal-opportunity obligations, we only accept candidate applications and agency submissions via our Applicant Tracking System (ATS). This ensures appropriate privacy notices, lawful processing, audibility, and consistent retention controls.

Any CVs or candidate details received outside the ATS (including via email, Slack, or direct message) will be treated as unsolicited, will not be considered as part of the recruitment process, and will not give rise to any fee or payment obligation.