Senior Software Engineer, Full Stack

About LMArena

LMArena is the open platform for evaluating how AI models perform in the real world. Created by researchers from UC Berkeley’s SkyLab, our mission is to measure and advance the frontier of AI for real-world use.

Millions of people use LMArena each month to explore how frontier systems perform — and we use our community’s feedback to build transparent, rigorous, and human-centered model evaluations. Leading enterprises and AI labs rely on our evaluations to understand real-world reliability, alignment, and impact. Our leaderboards are the gold standard for AI performance — trusted by leaders across the AI community and shaping the global conversation on model reliability and progress.

We’re a team of researchers, engineers, academics, and builders from places like UC Berkeley, Google, Stanford, DeepMind, and Discord. 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. Everyone on our team is a deep expert in their field — our office radiates excellence, energy, and focus.

About the Role

LMArena is seeking a Senior Full-Stack Product Engineer to lead the technical design and development of AI-focused products across our platform. You’ll be responsible for owning features end-to-end—from proposing technical approaches and implementing core product flows, to deploying new functionality and tracking its impact. This role is ideal for someone with proven experience building reliable business logic at scale who is excited to shape how people interact with cutting-edge AI models.

You’ll

• Expand data structures and business logic to support new features

• Visualize feature performance and usage metrics through internal tooling and dashboards

• Own the full feature lifecycle—from technical scoping to deployment and iteration based on insights

• Identify and advocate for process improvements in development, testing, and deployment.

• Experiment with new tools and frameworks to enhance productivity and product capabilities

You’ll have

• 5+ years of experience in software engineering, with a focus on full-stack or backend product development

• Deep knowledge in SQL and managing databases at scale

• Familiarity with testing practices and tools like Vitest (or similar testing frameworks)

• Clear communicator and strong collaborator across design, product, and engineering teams

• Bonus: PowerUser Experience with Supabase or Vercel's ai sdk

Our Tech Stack:

• NextJS

• Tailwind

• ShadCN

• HonoJS

• Postgres

• Vitest

What we offer

• We offer competitive compensation and equity aligned to the markets where our team members are based. The base salary range will depend on the candidate’s permanent work location.

• Comprehensive health and wellness benefits, including medical, dental, vision, and additional support programs.

• The opportunity to work on cutting-edge AI with a small, mission-driven team

• A culture that values transparency, trust, and community impact

Come help build the space where anyone can explore and help shape the future of AI.

LMArena provides equal employment opportunities (EEO) to all employees and applicants for employment without regard to race, color, religion, sex, national origin, age, disability, genetics, sexual orientation, gender identity, or gender expression. We are committed to a diverse and inclusive workforce and welcome people from all backgrounds, experiences, perspectives, and abilities.