Software Engineer, Product Security

ABOUT ARENA INTELLIGENCE Arena is the platform for evaluating how AI models perform in the real world. Founded by researchers from UC Berkeley's SkyLab, we're on a mission to measure and advance the frontier of AI for real-world use, and to build the foundation for everyone to understand, shape, and benefit from it. Tens of millions of people use Arena each month to evaluate how frontier systems handle the work they actually do. The preferences they share power the most transparent, rigorous, and human-centered evaluations in AI. Leading AI labs, enterprises, and independent researchers rely on our work and open datasets to understand how models behave in real workflows: agentic coding, creative generation, professional productivity, and beyond. We go beyond leaderboards and decompose what human experience reveals about AI, so models advance toward the work people actually do. We're a team of researchers, academics, builders, and creatives from UC Berkeley, Google, Stanford, and DeepMind. We seek truth, move fast, and value craftsmanship, curiosity, and impact over hierarchy. We're building a company where thoughtful, curious people from all backgrounds can do their best work together, in an office culture that radiates excellence, energy, and focus. ABOUT THE ROLE This is an engineering role. The work is in the product code: the authorization and identity layer, the API surfaces our users and partners depend on, and the libraries and patterns other engineers build on top of. You will design systems, write production code, and ship on the same cadence as the rest of engineering. Tens of millions of people use Arena every month to compare frontier models side by side. That makes our product surface an unusual one to defend: consumer scale, high-value partner data, frontier model integrations, and a user population that probes it constantly. You would define how product security works here, including the patterns, primitives, and defaults other engineers inherit. You'll work closely with product, infrastructure, and platform engineers. The work is zero-to-one in places and scale-it-up in others. We move fast and stay rigorous. WHAT YOU'LL DO Own authorization and identity in the product. Design and ship the authentication, authorization, and multi-tenant isolation code across our platform, along with the account, session, device, and credential lifecycle that other systems are built on: issuance, binding, expiry, and revocation. This is code you write, not findings you route. Solve AI security problems the industry has not settled. Untrusted model output crossing trust boundaries, tool-use and agentic surfaces including sandboxed code execution, isolation between model providers, and the authorization and handling controls around evaluation data. There is little prior art here and no off-the-shelf playbook. You will help write ours. Build privacy-preserving systems, and implement the data lifecycle in code. Pseudonymous identifiers, secret-backed derivation, and controlled re-identification, with the judgment to tell real pseudonymization from the appearance of it. Retention, deletion, and minimization as working product behavior across every store and pipeline that holds user data, including proving that what should be gone is actually gone. Make the product explain itself after the fact. Security-relevant events, including authentication, account changes, and privileged actions, need to be emitted from product code as durable, queryable records. You design what gets written, and you write it. Ship security-sensitive changes end to end. Request paths, partner integrations, data models, telemetry pipelines, and rollout controls that let you turn a change off without a deploy. That includes production migrations and backfills for sensitive data, throttled, resumable, observable, and reversible. It also includes the product integrations for third-party security and trust services, where you design the call paths and define conservative failure behavior. Own application security across the product, its APIs, and the browser. Content Security Policy and its reporting path, security headers, cookie and origin policy, and the third-party JavaScript running alongside user content. Ship the libraries, middleware, tests, and platform patterns engineers adopt because they are the easiest path. Lead threat modeling early enough to change a design, and own the fix in the codebase rather than the ticket. WHAT WE'RE LOOKING FOR We care most about two things: recent hands-on production engineering, and code-level application security judgment. 1. Production code you have personally written recently that you can walk through in depth: the architecture, how it changed over time, and which parts were yours. We hire software engineers for this role, and the engineering bar is the same as the rest of the team. 2. Application and API security: you apply it at the code level, not the checklist level.