Fullstack Software Engineer
US$175,000 – US$240,000 / yr base salary
Posted 8 Oct 2026
Advertised as “Senior Fullstack Software Engineer, AI Observability & Evals Platform (NY)”
BranchFactor Summary
The original posting with the fluff stripped out
- Expected experience
- 5+ yrs
- Management level
- People management
- Employment
- On-Site
- Contract
- Full-time
| Base salary | US$175,000 – US$240,000 / yr |
|---|
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 the role:
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:
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Lead the technical architecture and implementation of key product features for LangSmith, working across our entire Go, Python, and Typescript stack.
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Collaborate closely with product and design teams to iterate on new features.
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Mentor and guide more junior members of the team. Drive aggressive project timelines while ensuring high engineering standards are being met.
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Lead by example in writing clean, maintainable, and well-tested code
What You Bring:
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5+ years of experience in software engineering working on complex platform products
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Fullstack engineering experience with Go or Python on the backend and React + Typescript on the frontend.
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Strong understanding of database systems, particularly Postgres and Redis