Senior Fullstack Engineer, AI Observability & Evals Platform at LangChain (San Francisco, CA)
LangChain· San Francisco, CA· $175k–$225k·
Role details
Medical Coverage · Dental Coverage · Vision Coverage · Flexible Vacation · 401(K) Plan · Meals On In-Office Days
LangChain at a glance
The open-source frameworks (LangChain, LangGraph) and LangSmith platform developers use to build, observe, and ship AI agents.
LangChain builds the open source frameworks (LangChain, LangGraph) developers use to build AI agents, and sells LangSmith, a commercial platform to observe, evaluate, deploy, and improve those agents in production. It is framework-agnostic, working with any model or agent stack.
$160M raised · latest: Series B · $125M · Oct 2025 · $1.25B valuation · backed by IVP, Sequoia Capital, Benchmark, CapitalG
Summary
Lead the technical architecture and implementation of LangSmith, an observability and evaluations platform. Collaborate with product and design teams to iterate on features, mentor junior engineers, and ensure high engineering standards while shipping fast.
Job description
About Us
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.
About Us:
About the role
In person 5 days/week in San Francisco We're looking for a Senior Fullstack Engineer for our commercial product LangSmith, an observability and evals platform. In this role, you'll have the opportunity to shape the technical direction of our platform while working closely with enterprise customers, developer end-users and internal stakeholders.
What You Will Do
- Lead the technical architecture and implementation of key product features for LangSmith, working across our entire Go, Python, and Typescript stack.
- Collaborate closely with product and design teams to iterate on new features.
- Mentor and guide more junior members of the team. Drive aggressive project timelines while ensuring high engineering standards are being met.
- Lead by example in writing clean, maintainable, and well-tested code
What You Bring
- 5+ 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.
- Strong understanding of database systems, particularly Postgres and Redis
- Experience designing and scaling APIs, preferably in a high-performance, data-intensive application
- A “get stuff done” attitude - 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
- Strong ownership mindset
- Bonus: Experience with AI/LLM-powered applications, developer tools, or observability platforms
Compensation
- Annual salary range: $175,000-$240,000 USD
Compensation Philosophy: We offer competitive compensation that includes base salary, variable compensation for relevant roles, meaningful equity, benefits, and perks. Actual compensation and offerings will vary based on role, level, and location. Team members in the EU, UK, and APAC receive locally competitive benefits aligned with regional norms and regulations.
Benefits
Benefits include medical, dental, and vision coverage, flexible vacation, a 401(k) plan, meals on in-office days in the US and more.
Why work at LangChain
- Culture: Fast-moving, open source–first startup with a mission to shape how the world uses AI. Described as hiring “the best in the business” with a focus on engineering excellence.
- Work policy: Hybrid/office presence in San Francisco, New York, Boston, and Amsterdam. Remote roles may exist (not explicitly stated, but global hiring suggests flexibility).
- Notable perks/engineering culture:
- Work on cutting-edge agent technology used by millions of developers.
- High autonomy and impact – small team with big ambitions.
- Strong alumni network from top tech companies (AWS, Datadog, HashiCorp, GitLab, etc.).
- Recent departures include VP of Marketing (Diana Smith, Mar 2026) – indicates some churn, but overall rapid hiring.
- Active job postings across engineering, sales, product, and consulting – strong growth trajectory.