Senior Frontend Engineer

The future of AI — whether in training or evaluation, classical ML or agentic workflows — starts with high-quality data. At HumanSignal, we’re building the platform that powers the creation, curation, and evaluation of that data. From fine-tuning foundation models to validating agent behaviors in production, our tools are used by leading AI teams to ensure models are grounded in real-world signal, not noise. Our open-source product, Label Studio , has become the de facto standard for labeling and evaluating data across modalities — from text and images to time series and agents-in-environments. With over 250,000 users and hundreds of millions of labeled samples, it’s the most widely adopted OSS solution for teams working on building AI systems. Label Studio Enterprise builds on that traction with the security, collaboration, and scalability features needed to support mission-critical AI pipelines — powering everything from model training datasets to eval test sets to continuous feedback loops.We started before foundation models were mainstream, and we’re doubling down now that AI is eating the world. If you're excited to help leading AI teams build smarter, more accurate systems — we’d love to talk. This is a product-engineering role: not “build what you’re told,” but shape what we build —own the problem, propose solutions, and ship outcomes that matter to users and the business. About the role We’re hiring a Senior Frontend Engineer with product vision . You’ll lead with craft—shipping fast, accessible UX in React/TypeScript —and partner early with PM/Design to frame problems, prototype to learn, and make pragmatic scope calls. You care about clarity, performance, and simplicity in complex, data-heavy workflows—so the result feels simple , performant , and trustworthy . Responsibilities Build and maintain frontend components and views for labeling, review, and evaluation workflows with performance, accessibility, and scalability in mind. Own outcomes, not tasks: refine scope, suggest trade-offs, propose simpler approaches, and land increments that deliver value fast. Partner with Product Design from discovery to delivery: clarify user jobs, write lightweight RFCs/PRDs, and shape scope and milestones. Prototype to de-risk UX; use flags/gradual rollouts; gather feedback from users/support and iterate after releases. Raise the bar on FE standards: state management, testing, error boundaries, a11y, i18n, and developer ergonomics. Partner with Support to investigate production issues, reduce UX papercuts, and turn learnings into fixes. Engage with our open-source community (issues, discussions) to understand real-world needs and improve developer experience. Participate in architecture discussions and code reviews; mentor teammates and improve patterns across the codebase. What you’ll bring Senior-level experience shipping production React/TypeScript apps (HTML/CSS mastery; ES6+; a11y). Strong product sense : you’ve made scope/trade-off decisions and iterated based on real-world usage and feedback. Fluency with modern FE tooling (e.g., Vite/Webpack, Jest/Cypress) and state-management patterns. Comfort collaborating with APIs and occasionally touching backend code ( Django/REST familiarity is a plus). Excellent communication at a Senior IC level —you write clear RFCs/PRDs, give actionable reviews, and present trade-offs well. Nice to have Experience with data/ML tools, OSS, design systems, or performance profiling. Familiarity with feature flags/gradual rollouts and qualitative feedback loops (support forums, user sessions). Prior work on complex, data-heavy UIs (review tools, multi-step workflows, or IDE-like apps). Our stack Python/Django, JS/TS, React, OpenAI API, Spark, BigQuery, Kafka, Jest, Cypress, AWS, Kubernetes, Postgres, Redis. How we build Trunk-based development with small, reviewable PRs; feature flags for safe rollouts; strong code reviews; pragmatic testing; and ... (truncated, view full listing at source)