Senior Frontend Engineer, AI Observabilty Platform

At Lang Chain, our mission is to make intelligent agents ubiquitous. We build the foundation for agent engineering in the real world, helping developers move from prototypes to production-ready AI agents that teams can rely on. We began as widely adopted open-source tools and have grown to also offer a platform for building, evaluating, deploying, and operating agents at scale.

With $125M raised at Series B from IVP, Sequoia, Benchmark, CapitalG, and Sapphire Ventures, we’re at a stage where we’re continuing to develop new products, growth is accelerating, and all team members have meaningful impact on what we build and how we work together. Lang Chain is a place where your contributions can shape how this technology shows up in the real world.

Today, our platform includes Lang Smith (Observability, Evaluation, Deployment, Fleet, and Sandboxes), our open source frameworks (Lang Chain, Lang Graph, and Deep Agents), and the newly launched Lang Smith Engine for autonomous agent improvement. We have 100M+ monthly open source downloads, 6,000+ active Lang Smith customers, and 5 of the Fortune 10 use Lang Smith in production (+ 35% of the Fortune 500 overall), including teams at Klarna, Clay, Coinbase, Workday, Lyft, Cloudflare, Harvey, Rippling, Vanta, Linked In, , Nvidia, and Bridgewater.

The Lang Smith team owns and builds Lang Chain's core platform for observability, evaluation, and production reliability of AI systems. From tracing and annotation to run rules, evaluations, and beyond, this team owns Lang Smith end-to-end. If you want to define what great AI observability looks like at production scale, this is where that work gets done.

(Onsite in Boston)

We’re looking to bring on an experienced frontend engineer to develop and enhance new features on Lang Smith, our enterprise platform product for LLM application observability, testing, and debugging.

• Develop new user-facing features using React & Typescript

• Build reusable components and front-end libraries for future use

• Translate designs and wireframes into high-quality code

• Optimize components for maximum performance across a vast array of web-capable devices and browsers

• Collaborate with fullstack and backend developers and UX/UI designers, to enhance usability

• Extensive front-end engineering experience with strong proficiency in React, JavaScript and Type Script

• Hands-on experience with front-end development tools like Babel, Vite, Webpack, NPM, and Yarn

• Familiarity with REST APIs and experience working closely with fullstack and backend engineers

• Knowledge of modern authorization mechanisms, such as JWTs

• A passion for user experience, design and building clean, engaging, and intuitive interfaces

• Strong written and oral communication skills, with the ability to explain technical concepts clearly and concisely to both technical and non-technical stakeholders

• The DNA to thrive in a start-up, fast-paced environment. Views unstructured environments as an opportunity to figure out the most impactful work and help define the future success of the company

• An ownership mind-set. You are self-driven and look for opportunities to make an impact.

• Strong computer science fundamentals, ideally with a degree in computer science or related field

Annual salary range: $170,000-$235,000 USD

Compensation Philosophy:

We offer competitive compensation that includes base salary, variable compensation for relevant roles, meaningful equity, benefits, and perks.

We are hiring for this role across a range of scope, and the compensation band reflects that. Your offer depends on what we learn about your impact, craft, leadership, and communication during the interview process. We will tell you early where you’re tracking and talk comp with you before offer stage. Team members in the EU, UK, and APAC receive locally competitive benefits aligned with regional norms and regulations.

Benefits include medical, dental, and vision coverage, flexible vacation, a 401(k) plan, meals on in-office days in the US and more.