Senior Frontend Engineer (Los Altos)

Cheiron•Los Altos, CA

5d•Onsite

About The Position

Cheiron is seeking a Lead Frontend Engineer to take ownership of and drive the company's frontend development. The value Cheiron provides is ultimately realized through the user experience, encompassing product responsiveness, clarity in conveying AI results, and the effective presentation of complex workflows. The frontend for an AI product presents unique challenges, including handling streaming responses, displaying sources and citations, managing multi-step task states, implementing error and retry mechanisms, and incorporating user feedback loops. This role involves designing and building interfaces that foster user trust in AI agents and enable their use in real-world tasks. Beyond just building UI components, the Lead Frontend Engineer will act as a crucial link between Product, Design, and Engineering, ensuring the quality and consistency of Cheiron's frontend. As a hands-on role in a seed-stage company, this position requires an experienced builder capable of rapidly transforming ambiguous requirements into product-quality interfaces. The ideal candidate possesses strong frontend engineering skills, an understanding of AI product UX, and the drive to work at a fast-paced startup pace.

Requirements

4+ years of frontend experience with React, TypeScript, Tailwind CSS, and modern JavaScript.
Deep understanding of component architecture, design system implementation, state management, API integration, and performance optimization.
Demonstrated frontend ownership: experience raising the quality and standards of a product's frontend, and reviewing/guiding other engineers' frontend work, including full-stack engineers.
Ability to translate designer specifications into production-quality UI, with a focus on responsiveness, accessibility, interaction states, and pixel-perfect details.
Experience integrating AI/LLM products on the frontend, including solving AI-specific UX challenges like streaming, non-deterministic results, long-running execution, and citation display.
Active use of AI coding tools such as Claude Code and Cursor.
Drive to set priorities and ship quickly, even with incomplete specifications.
English proficiency in documentation, conversation, and code reviews for daily collaboration with a multi-region team.

Nice To Haves

Experience building and operating an in-house design system or component library from scratch, including design and governance.
Data-heavy UI experience, such as complex tables, virtualization, large result rendering, or document- and form-centric interfaces.
Experience with modern frontend tooling and test infrastructure like Next.js, Vite, React Query, Zustand/Redux, Storybook, Playwright, and Vitest.
Experience building enterprise SaaS, or products for the pharma, biotech, or healthcare industries.
Experience at a seed or early-stage startup.

Responsibilities

Own the quality, standards, and consistency of Cheiron's frontend, including architecture, component patterns, design system, coding conventions, review culture, and refactoring existing code.
Bridge Product, Design, and Engineering to ensure design intent and product goals are accurately reflected in the frontend.
Build UX that makes AI agent results trustworthy, addressing challenges like streaming responses, source and citation display, multi-step progress states, error and retry flows, and feedback loops.
Own pre-launch design QA, ensuring responsiveness, interactions, and pixel-level details are meticulously handled to preserve the designer's vision.
Build core screens and interactions using React, TypeScript, and Tailwind CSS.
Guide and review frontend contributions from other engineers, including full-stack engineers, to elevate the team's overall frontend expertise.
Collaborate effectively in English with a distributed team across the US, Korea, and other regions.