Frontend Engineer in London

HASH's open-source platform helps firms integrate both structured and unstructured information into knowledge graphs that support simulating, optimizing and automating processes. Our mission is to solve information failure and help everybody make the right decisions. We prioritize speed and measure product delivery timelines in hours and days, not months and years. We value high-energy, high-expectations people who do what they say and say what they mean. We're committed to building a high-commitment, high-trust environment and believe that the best teams are most productive together, in-person. We're therefore currently hiring exclusively in both London (UK) and Berlin (Germany).

About the role: We’re a fast-growing deep-tech company crafting web-based tools that help people model, understand, and optimize real-world systems and processes using AI. As a senior Frontend Engineer, you’ll own end-to-end delivery of novel world modeling and AI native interface components, helping shape our frontend architecture. You’ll collaborate with technical product management, UX researchers and AI engineers from top labs, as well as our own developers and leadership.

What you'll work on:

• Design, build, and ship production-ready React/TypeScript components and app-wide features for complex data-driven UIs.
• Work with mathematical experts to convert world-modeling theory formalizations into software requirements, and writing tests which ensure implementation correctness.
• Convert novel UX/UI designs into performant, responsive and accessible experiences that work across devices.
• Establish project-wide standards for code quality, review and testing, and provide feedback on the work of other frontend engineers.
• Profile and optimize rendering performance for complex interactions and visualisations.
• Tell the story of best practices and lessons learned in developing and testing novel, complex world-modeling interfaces.
• Partner with backend/infra teams to identify and manage interdependencies, and to help define robust APIs that support excellent, feature-rich frontend performance.
• Stay on top of emerging browser capabilities and drive adoption of the ones that matter.

Requirements:

Must have:

• Expertise with React, TypeScript, modern HTML & CSS.
• Proven track record architecting and delivering rich web apps that involve complex user interactions.
• Rigorous approach to documenting and versioning components for external audiences.
• Experience profiling and debugging performance in devtools.
• Comfortable taking a visible technical leadership role, mediating discussions around standards and implementation approaches.
• Excellent written & verbal communication in English and comfort working async.

Nice to have:

• Familiarity with process/model-oriented UIs: BPMN, UML, systems-dynamics models, graphs, etc.
• Understanding of WCAG 2.2 and pragmatic accessibility techniques.
• Public record of maintaining a well-documented, semantically versioned library.
• Experience with CRDTs or other real-time collaboration solutions.
• Hands-on experience with WebAssembly pipelines.
• Canvas/WebGL experience for high-performance rendering.

Benefits: We offer leading equity-weighted total compensation, including competitive salaries and tax-advantaged options. We also offer employer pension contributions, at least 30 days holiday annually, and quarterly in-person team retreats around the world. This role pays £60,000-£110,000 base/bonus + meaningful equity.