Senior Software Engineer, Frontend at LMArena

LMArena is seeking an experienced Senior Frontend Product Engineer to lead the design and development of intuitive, AI‑focused user experiences across our platform. You’ll be responsible for owning features from proposing technical approaches, implementing core UI/UX flows, to deploying new functionality and tracking its impact through analytics. This role is ideal for someone who combines strong frontend craft with backend thinking, thrives on building polished user interfaces, and is excited to shape how people interact with cutting‑edge AI models.

• Lead development of UI and application logic for our chat interface using React and Next.js.
• Craft intuitive, accessible, and responsive user experiences that feel delightful across devices.
• Collaborate closely with design to maintain and extend a cohesive visual language and component system.
• Implement A11y accessibility standards and internationalization (i18n) support for a global audience.
• Expand backend data structures and business logic to support new frontend features.
• Plan and integrate analytics to measure user engagement, adoption, and product performance.
• Visualize feature performance and usage metrics through dashboards and internal tooling.
• Own the full feature lifecycle—from technical scoping to deployment and iteration based on insights.

Created by researchers from UC Berkeley’s Sky Lab, LMArena is an open platform that enables anyone to easily access, explore, and interact with the world’s leading AI models. By comparing them side by side and casting votes for the better response, the community helps shape a public leader board, making AI progress more transparent and grounded in real‑world usage.

LMArena is rapidly becoming essential infrastructure for transparent, human‑centered AI evaluation at scale, trusted by organizations such as Google, OpenAI, Meta, xAI, and more. With over one million monthly users and growing developer adoption, our work helps guide the next generation of safe, aligned AI systems.

• 5+ years of experience in software engineering, focusing on full‑stack or frontend product development.
• Deep experience building accessible, responsive React/Next.js interfaces in production.
• Strong CSS fundamentals and familiarity with utility‑first frameworks like Tailwind.
• Experience with modern component systems such as ShadCN or similar design systems.
• Comfortable building and integrating backend APIs (bonus if you’ve worked with HonoJS or lightweight frameworks).
• Proficient with relational databases such as Postgres, and how to extend schemas to support new features.
• Familiarity with testing practices and tools such as Vitest (or similar testing frameworks).
• Experience integrating analytics tools and using product metrics to guide iteration.
• Clear communicator and strong collaborator across design, product, and engineering teams.
• Bonus:
  Experience building real‑time or AI‑driven UIs, or shipping features for technical audiences.

• Next.js
• Tailwind
• ShadCN
• HonoJS
• PostgreSQL
• Vitest

• Salary range: $210k – $231k + equity.
• Competitive salary and meaningful equity.
• Comprehensive healthcare coverage (medical, dental, vision).
• The opportunity to work on cutting‑edge AI with a small, mission‑driven team.
• A culture that values transparency, trust, and community impact.