Senior UI Architect - AI SaaS Platform - London (Hybrid)

About the Role

Stax - Deep Tech Headhunters are partnering with a high-growth international Series A company on a mission to transform the way organisations harness AI for customer support and product operations.

They're looking for a Senior UI Architect who sits at the intersection of design excellence and engineering. This is a hands-on, systems-level leadership role for someone who doesn't just ship components-they craft cohesive, elegant, ultra-performant experiences.

You'll play a defining role in setting the architectural direction for all user-facing surfaces-from fast, reactive dashboards to rich collaborative tools-ensuring interfaces are not only beautiful and intuitive, but also scalable and lightning-fast.

What You'll Do

• Architect performant, low-latency UI systems that feel instantaneous and intuitive
• Elevate the design system with best-in-class standards for simplicity, extensibility, and polish
• Drive tight collaboration with product designers-translating vision into crisp, low-friction user flows
• Mentor and uplift engineers across teams on code quality, architecture, and UX craft
• Set and uphold benchmarks for UI performance (TTI, Lighthouse, bundle sizes, animation fluidity)
• Lead innovation across complex surfaces like search, timelines, real-time dashboards, and data-dense interfaces
• Define and enforce front-end best practices, including accessibility, interaction design, and motion principles
• Partner closely with backend and platform teams to influence API design for optimal UX

You Might Be a Fit If You Have

• 10-15+ years of experience building production-grade UIs using TypeScript, React, GraphQL, and modern CSS frameworks
• A strong track record architecting scalable frontend systems and leading large UI projects end-to-end
• Mastery of UI performance concepts (hydration, layout thrashing, render timing, etc.)
• Experience evolving design systems at scale-with an eye for consistency, structure, and documentation
• A design-sensitive approach to development, treating UX as a shared responsibility
• Bonus: Experience with real-time data, stream-based UIs, or visualization libraries like D3/WebGL
• Bonus: Familiarity with PLG principles and the UX nuances of high-growth B2B SaaS platforms

Why This Role?

You'll be joining a deeply design-led culture, where architecture is about crafting user delight-not just technical scalability. This is an opportunity to shape the front-end foundation of a new category-defining platform at the ground level, in an environment that values velocity, quality, and cross-disciplinary collaboration.

Architects here don't operate in silos. They lead from the front-building, mentoring, and pushing boundaries every day. Stax is proud to represent this opportunity. If you're a UI leader who's excited by scale, strategy, and AI-powered innovation, we'd love to hear from you. We welcome applicants from all backgrounds.