Senior Software Engineer, Frontend

Software Engineer (Frontend) at LMArena

Location : SF Bay Area / Remote

Type : Full-Time

About the Role :

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 and 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.

Responsibilities :

• 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

Who is LMArena?

Created by researchers from UC Berkeley's SkyLab, LMArena is an open platform where everyone can 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 leaderboard, making AI progress more transparent, and grounded in real-world usage.

Why Join Us?

Trusted by organizations like Google, OpenAI, Meta, xAI, and more, LMArena is rapidly becoming essential infrastructure for transparent, human-centered AI evaluation at scale. With over one million monthly users and growing developer adoption, our impact is helping guide the next generation of safe, aligned AI systems-grounded in open access and collective feedback.

Our work is regularly referenced by industry leaders pushing the frontier of safe and reliable AI. Sundar Pichai, Jeff Dean, Elon Musk, and Sam Altman.

High Impact : Your work will be used daily by the world's most advanced AI labs.

Global Reach : Develop data infrastructure powering millions of real-world evaluations, influencing AI reliability across industries at the top-tier

Exceptional Team : We are a small team of top talent from Google, DeepMind, Discord, Vercel, UC Berkeley, and Stanford.

Requirements :

5+ years of experience in software engineering, with a focus 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 working 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 like 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

Our Tech Stack :

NextJS

Tailwind

ShadCN

HonoJS

Postgres

Vitest

What we offer :

210k - 231k + equity. Actual compensation will depend on job-related knowledge, skills, experience, and candidate location.

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

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