FullStack Engineer, AI Observability & Evals Platform (LangSmith)

San Francisco · Boston · New York, NY · USD 145,000-180,000 / year · 2+ years experience · Full-time · Onsite · Posted Oct 14, 2026

At a glance

At LangChain, 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. LangChain is a place where your contributions can shape how this technology shows up in the real world.
Today, our platform includes LangSmith (Observability, Evaluation, Deployment, Fleet, and Sandboxes), our open source frameworks (LangChain, LangGraph, and Deep Agents), and the newly launched LangSmith Engine for autonomous agent improvement. We have 100M+ monthly open source downloads, 6,000+ active LangSmith customers, and 5 of the Fortune 10 use LangSmith in production (+ 35% of the Fortune 500 overall), including teams at Klarna, Clay, Coinbase, Workday, Lyft, Cloudflare, Harvey, Rippling, Vanta, LinkedIn, Monday.com, Nvidia, and Bridgewater.

We're looking for a Fullstack Engineer to work on LangSmith, our commercial AI observability and evals platform product.
In this role, you'll have the opportunity to build new features and functionality for the platform while working close enterprise customers, developer end-users and internal stakeholders.

Develop and implement key product features working across our entire Go, Python, and Typescript stack
Collaborate closely with product and design teams to iterate on new features and enhance the product roadmap
Drive aggressive project timelines while ensuring high engineering standards are being met by writing clean, maintainable, and well-tested code

2+ years of experience in software engineering working on complex platform products
Fullstack engineering experience with Go or Python on the backend and React + Typescript on the frontend
Solid understanding of database systems, particularly Postgres and Redis
Experience designing and scaling APIs, preferably in high-performance, data-intensive applications
Strong ownership and a “get stuff done” mindset - comfortable shipping fast and iterating based on user feedback
Strong communicator with the ability to collaborate closely with various internal stakeholders and engage directly with our top-tier customers

Experience with AI/LLM-powered applications, developer tools, or observability platforms