Principal Frontend Engineer

Harnham; Oakland (CA); On-site; USD 140,000 - 190,000; Full time

Job summary

Harnham is seeking a hands-on Principal or Senior Frontend Engineer to help build the next generation of AI-powered product experiences on top of large-scale knowledge systems and domain-specific datasets. This role blends frontend engineering with AI-driven UX, product development, and platform architecture.

You will design, build, deploy, and iterate on intelligent applications that leverage LLMs, retrieval, search, and AI copilots, owning the full user experience.

Qualifications

• Experience building AI-powered frontend apps with React/TypeScript.
• Strong understanding of design systems and accessibility.
• Ability to own end-to-end frontend features from concept to production.

Responsibilities

• Design and build AI-native frontend experiences that help users discover, consume, and interact with information.
• Develop frontend applications integrating LLMs, semantic search, recommendations, and AI copilots.
• Create highly performant React and TypeScript applications used by large audiences.
• Build rich interfaces that surface AI-generated insights, recommendations, summaries, and workflows.
• Partner with design, product, data, and engineering to validate concepts and ship capabilities.
• Architect reusable frontend systems, design patterns, and shared component libraries.
• Influence frontend strategy, technical direction, and product architecture.
• Improve performance, reliability, accessibility, observability, and UX across the platform.

Skills

React

TypeScript

Next.js

HTML5/CSS3

Frontend testing

Design systems

Tools

REST APIs

GraphQL

CI/CD

Job description

We are seeking a hands-on Principal or Senior Frontend Engineer to help build the next generation of AI-powered product experiences on top of large-scale knowledge systems and domain-specific datasets.

This role is ideal for someone who enjoys operating at the intersection of frontend engineering, AI-powered user experiences, product development, and platform architecture. You'll work closely with technical leadership to design, build, deploy, and iterate on intelligent applications that leverage large language models, retrieval systems, recommendations, search, and AI-assisted workflows.

This is not a pure UI implementation role. We are looking for builders who can take ideas from concept to production, own the full user experience, and thrive in a fast-moving, high-ownership environment.

What You'll Do

• Design and build AI-native user experiences that help users discover, consume, and interact with information more effectively.
• Develop frontend applications integrating LLMs, semantic search, recommendations, and AI copilots.
• Create highly performant React and TypeScript applications used by large audiences.
• Build rich interfaces that surface AI-generated insights, recommendations, summaries, and workflows.
• Partner closely with design, product, data, and engineering teams to rapidly validate concepts and ship new capabilities.
• Architect reusable frontend systems, design patterns, and shared component libraries.
• Influence frontend strategy, technical direction, and product architecture.
• Continuously improve performance, reliability, accessibility, observability, and user experience across the platform.

Key Responsibilities

AI-Powered Product Experiences

• AI copilots and assistants
• LLM-powered user interfaces
• Conversational experiences
• AI-assisted workflows
• Search and discovery experiences
• Recommendations and personalization
• AI evaluation and user feedback loops
• Prompt and interaction design

Frontend Architecture

• React and TypeScript application architecture
• Component systems and design systems
• Micro-frontends (where appropriate)
• Performance optimization
• Accessibility and responsive design
• Testing and frontend quality frameworks
• Frontend observability and monitoring
• Rapid prototyping and experimentation
• A/B testing frameworks
• Collaboration with product and design
• End-to-end feature ownership

Desired Technical Experience

Frontend

• React
• TypeScript
• Next.js
• HTML5 / CSS3
• Frontend testing frameworks
• Design systems and component libraries

AI / ML Integration

• OpenAI, Anthropic, Gemini, or similar models
• AI-powered applications
• RAG-powered user experiences
• Semantic search systems
• Recommendations and retrieval systems
• AI copilots and assistants
• Prompt engineering and AI workflow design
• AI evaluation and feedback systems
• Python, Node.js, or similar backend technologies
• Django, FastAPI, Express, or related frameworks
• REST APIs
• GraphQL
• Data integrations

Infrastructure

• AWS
• Docker
• CI/CD
• Frontend deployment pipelines
• Monitoring and observability platforms

Data

• Redis
• Search platforms
• Analytics platforms
• Event tracking and experimentation systems