Staff Product Security Engineer - AI Systems

ABOUT FIRSTPRINCIPLES FirstPrinciples is building AI to accelerate scientific discovery. Our core product is the Theo Platform, a research environment built to help researchers iterate faster, validate rigorously, and reach verified results they can trust. We're a fast-growing, remote-first team of builders, researchers, engineers, and thinkers working across Canada, the US, the UK, and expanding globally. What brings us together is a shared curiosity about how the universe works, and a belief that we can build systems that help us explore it more effectively. We spend our time working on questions that don't have clear answers, like how to design AI that can reason through scientific problems, and how the scientific process as a whole might evolve. This is work that sits somewhere between creativity and rigorous thinking, and often requires comfort with ambiguity and iteration. If you're someone who enjoys tackling big, abstract problems and exploring ideas that don't yet have a defined path forward, you'll likely find the work here interesting. WHY THIS ROLE EXISTS: We are looking for a Staff Product Security Engineer to define and build the security architecture for Theo and the cloud platform surrounding it. Theo combines our own AI models, agentic workflows, tool use, code execution, scientific data, model serving, and multi-tenant SaaS infrastructure. These systems create new trust boundaries—and new ways for powerful software to fail, be misused, or be attacked. This is a hands-on software engineering and architecture role embedded within Engineering. It is not an IT, help-desk, security-operations, or policy-only position. You will review designs and code, build security-critical systems, test our platform adversarially, and help engineers make security a foundational property of the product. As a senior technical owner, you will have substantial influence over our architecture, engineering practices, and security roadmap. Your goal will not simply be to identify risk or prevent releases.

It will be to create secure defaults, reusable controls, and engineering systems that allow us to move quickly without compromising trust. WHAT YOU'LL DO: - Define the security architecture for Theo. Design security across our SaaS application, APIs, cloud infrastructure, model-serving systems, agent runtimes, data platforms, research environments, and deployment pipelines. - Secure agent identity and authority. Build robust authentication and authorization for users, services, and AI agents, including scoped credentials, delegated permissions, least-privilege tool access, approval boundaries, tenant isolation, and auditable agent actions. - Secure tool and code execution. Help design hardened execution environments for agent-generated and user-provided code, with strong isolation, resource limits, filesystem and network controls, provenance, monitoring, and escape testing. - Lead threat modelling and secure design. Work with Engineering, Research, Product, and Infrastructure from early architecture through production. Identify trust boundaries, abuse cases, attack paths, and practical mitigations before systems ship. - Address AI- and agent-specific threats. Defend against prompt and goal injection, unsafe tool use, confused-deputy behaviour, context or memory poisoning, insecure output handling, model and data exfiltration, model extraction, privilege escalation, resource abuse, and attacks across multi-agent workflows. - Build security-critical software. Implement secure-by-default services, libraries, policies, test harnesses, and platform controls for identity, secrets, encryption, policy enforcement, auditability, abuse prevention, and vulnerability management. - Embed security into development.