Senior Frontend Engineer (Los Altos)

Cheiron just raised an $8 million seed round led by Menlo Ventures to build the operating system for drug programs.     ■ Company Overview In July 2026, Cheiron announced an $8 million seed round led by Menlo Ventures, bringing total funding to $13 million to date, with the backing and strategic support of industry veterans including Moderna co-founder and MIT Institute Professor Robert Langer, former Pfizer Chief Medical Officer Freda Lewis-Hall, Chai Discovery co-founder and CEO Josh Meier, former Starbucks CEO Laxman Narasimhan, and former Apple AI chief John Giannandrea.   Cheiron is building the first AI-native operating system designed to represent an entire drug program as a single connected system. The company's platform helps biopharma teams represent, reason over, and stress-test the full state of a drug development program — including the claims, evidence, assumptions, risks, decisions, and commitments that determine whether a therapy advances.   At the center of the platform is Cheiron's proprietary Life Sciences Knowledge Graph (LKG), connecting the world's biomedical, clinical, regulatory, patent, and commercial knowledge into a single model built for the inferences drug developers make every day. In less than six months since launch, Cheiron has been adopted by tens of thousands of biopharma professionals and deployed by major drug developers, and is already used by 7 of Korea's top 10 biopharma companies.   Founded in 2024 by Stanford-trained AI researchers and biopharma operators, Cheiron is headquartered in Los Altos, California.   ■ About the Role We're looking for a Lead Frontend Engineer to own and drive Cheiron's frontend. Cheiron's value ultimately comes together in what users actually experience. How fast the product responds, how reliably it conveys AI results, and how clearly it makes sense of complex workflows all come down to the frontend experience. The frontend of an AI product faces a different class of problems than typical SaaS: streaming responses, source and citation display, multi-step task states, error and retry flows, and user feedback loops. You'll design and build the interfaces that let users trust AI agents and put them to work in real tasks. This isn't a role for just building UI components. You'll sit at the bridge between Product, Design, and Engineering, driving the quality and consistency of Cheiron's frontend. And like any seed-stage company, it's also a hands-on IC role where you'll build the core screens and interactions yourself. We're looking for an experienced builder who can quickly turn ambiguous requirements into product-quality interfaces. We care about strong frontend engineering skills, a feel for AI product UX, and the drive to operate at seed-stage startup speed.       ■ What You'll Do - Own the quality, standards, and consistency of Cheiron's frontend: architecture, component patterns, design system, coding conventions, review culture, and refactoring existing code - Bridge Product, Design, and Engineering so that design intent and product goals are faithfully reflected in the frontend - Build UX that makes AI agent results trustworthy: streaming responses, source and citation display, multi-step progress states, error and retry flows, and feedback loops - Own pre-launch design QA: polish responsiveness, interactions, and pixel details all the way through so the designer's intent doesn't get lost in implementation - Build core screens and interactions in React, TypeScript, and Tailwind CSS — a lead who still builds with their hands - Guide and review other engineers' frontend contributions (including full-stack engineers) and raise the team's frontend bar - Collaborate effectively in English with a distributed team across the US, Korea, and beyond       ■ 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 - Frontend ownership: you've personally raised the quality and standards of a product's frontend and reviewed and guided other engineers' frontend work, including full-stack engineers - The skill to turn designer specs into production-quality UI, with the persistence to carry responsiveness, accessibility, interaction states, and pixel details all the way through - Experience integrating AI/LLM products on the frontend: you've solved 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 - The drive to set your own priorities and ship quickly, even when specs are incomplete - English proficiency across docs, conversation, and code review (daily collaboration with a multi-region team)       ■ Nice to Have - Experience building and operating an in-house design system or component library from scratch — design and governance, not just usage - Data-heavy UI experience: complex tables, virtualization, large result rendering, or document- and form-centric interfaces - Experience with modern frontend tooling and test infrastructure such as Next.js, Vite, React Query, Zustand/Redux, Storybook, Playwright, and Vitest - Experience building enterprise SaaS, or pharma, biotech, or healthcare products - Experience at a seed or early-stage startup       ■ Benefits & Perks - 401(K) retirement plan - Health insurances (Medical/Dental/Vision) - Meal allowance (Lunch, Dinner) - Transportation support for early starts and late nights - In-office snack bar and additional commuting and work travel support       ■ Interview Process Screening ＞ Take-home Assignment ＞ Technical Interview ＞ Cultural Interview