Job title: Product Engineer Location: London; full in-office working as default Start date: ASAP Reports to: Head of Engineering Compensation: BASE : £70,000 - £90,000 EQUITY : £70,000 - £90,000 ___________________________________________________________________________ Cosine at a glance At Cosine, we’re building autonomous AI engineers that plan, write, and ship code inside real development workflows. Cosine is designed for on-premise and virtual private cloud (VPC) deployments, including fully air-gapped environments. We build our agent tooling entirely in-house and post-train open-source models to deliver reliable, enterprise-grade coding performance in security-critical settings. In 2024, Cosine achieved a 72% score on OpenAI’s SWE-Lancer benchmark, placing us among the strongest real-world software-engineering AI systems evaluated. YC-backed and well-funded, Cosine was founded by experienced operators focused on building dependable, production-grade AI. This role is based in our Hoxton office, five days a week, because close collaboration, fast feedback, and shared context matter for the problems we’re solving. ___________________________________________________________________________ The role A Product Engineer at Cosine works closely across research, engineering, product, and design to turn advanced AI capabilities into intuitive, reliable tools for developers. You will be responsible for building and evolving Cosine’s user-facing product surfaces, including IDE extensions or dedicated apps and web applications that expose the power of our models through well-designed workflows and interfaces. Your work sits at the intersection of product, platform, and research, translating emerging model capabilities into concrete experiences developers can use every day. We focus on rapid product iteration without compromising quality. This means building systems that are performant, observable, and robust, while remaining flexible enough to evolve alongside fast-moving research and user needs. You will help define how developers interact with Cosine, from first use through advanced, production-grade workflows. ___________________________________________________________________________ Your Mission Deliver a scalable, high-quality Cosine product experience by building IDE and web application interfaces and integrations that expose the power of our models in intuitive, reliable ways. Responsibilities Build end-user products (editor extensions and web applications and platform capabilities) that integrate with the Cosine platform APIs Enable developers to use advanced language models to augment their workflows and problem-solving capabilities Collaborate closely research to explore and validate new product experiences and capabilities Translate emerging model capabilities into concrete, user-facing features Maintain a high bar for performance, reliability, and usability across platforms Be opinionated about and bring your own ideas to the table, we’re building for engineers, as an engineer you have a say in what you want to use. ___________________________________________________________________________ Skills & Experience Frontend & Application Development Experience building reactive, highly interactive applications (React, Svelte, Vue) Experience with cli application development or local software development is a plus Backend & Systems Comfortable with backend development Experience designing and consuming REST APIs Developer Experience Experience working with developer tooling Familiarity with CI/CD pipelines Experience with containerization Programming Languages Strong experience with TypeScript and modern frontend frameworks Knowledge of Node.js, Python, and Go is a plus Tooling & Infrastructure Git, Docker, Webpack, npm Monitoring and alerting tools (e.g. Grafana, Datadog) Feature flagging systems ___________________________________________________________________________ You Might Thrive in This Role If You: Have 5 years of experience building production-grade software, with a strong emphasis on user-facing developer tools. Have shipped and maintained complex frontend or full-stack applications used by technical users. Are comfortable building highly interactive web or IDE-based experiences using modern frameworks (e.g. React, TypeScript). Have experience designing and consuming APIs, and understand how frontend and backend systems evolve together. Enjoy working close to the product surface, translating ambiguous ideas and model capabilities into intuitive developer workflows. Care deeply about developer experience, performance, and reliability—not just functionality. Are comfortable iterating quickly, running experiments, and refining products based on real user feedback. Can operate effectively in a fast-moving environment with evolving priorities and incomplete information. ___________________________________________________________________________ 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. ___________________________________________________________________________ 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 Genuine 9–5 working hours - we don’t expect late nights or weekend work 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 want structure, clarity, strong collaboration, and a team that takes both the work and work-life balance seriously, it’s a great place to be. ___________________________________________________________________________ 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, auditability, 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.