Senior Frontend Developer

Senior React Frontend Developer (AI Platform)

Industry:

Software Development / AI

Location:

USA – Fully Remote

Salary:

$140,000–$190,000 Base Salary

X4 Engineering are proud to be partnering with an innovative, venture-backed start-up at the forefront of the rapidly evolving AI agent ecosystem.

The organization are building a cutting-edge platform that enables seamless interaction between AI agents, developers, and enterprise systems.

As part of their continued growth, they’re looking for a Senior React Front-End Engineer to take ownership of the user-facing platform experience. You’ll be responsible for building intuitive, high-performance interfaces that expose complex AI agent behaviour in a clear and actionable way. This includes real-time streaming UIs, workflow visualisation, and developer-focused tooling that enhances how users interact with the platform.

Key Requirements:

• Bachelor’s or Master’s degree in Computer Science, Engineering, or a related field.
• 5\+ years of experience building modern front-end applications using React.
• Strong proficiency in TypeScript and modern JavaScript (ES6\+).
• Experience building real-time, data-intensive UIs (WebSockets, streaming, live updates).
• Familiarity with state management libraries (e.g. Redux, Zustand, or similar).
• Experience designing clean, intuitive developer-facing interfaces and tools.
• Strong understanding of REST APIs and experience integrating with backend services.
• Experience working in fast-paced, startup environments with evolving requirements.

Nice to Have:

• Experience with AI/LLM-powered applications or agent-based systems.
• Familiarity with visualising workflows, graphs, or state machines.
• Experience with design systems and component libraries.
• Exposure to backend technologies (Node.js, Python) and full-stack collaboration.

If you’re interested in the role please apply via the job advert or get in touch with a.koivio@x4engineering.