Founding Senior Full-Stack Engineer

This is a job that Jill, our AI Recruiter, is recruiting for on behalf of one of our customers. She will pick the best candidates from Jack's network. The next step is to speak to Jack. Job Title Founding Senior Full-Stack Engineer Salary Not Disclosed Company Description Stealth-stage AI coordination startup Job Description Join a high-velocity founding team building the operating system for the agentic era. You will architect a real-time, multiplayer agent system that automates coordination work through proprietary semantic memory and symbolic control. This role bridges complex LLM workflows and high-performance front-end engineering to redefine how teams collaborate in the modern workplace. Location London, UK or San Francisco, USA Why this role is remarkable You will be the first engineering hire, working directly with founders from top-tier academic and commercial backgrounds to define the technical foundation.The company is backed by top-tier global VCs and has already secured active procurement with major enterprise partners despite being in early stealth.You will build a new paradigm for work beyond simple chatbots, focusing on structured agent-to-agent negotiation and first-principles AI infrastructure. What You Will Do Own the end-to-end development of agentic systems, including multi-step LLM pipelines, structured outputs, and real-world agent negotiation loops.Architect and scale deep integrations with major productivity tools like Slack, Notion, and Linear to build a comprehensive world model.Optimize front-end performance to ensure the web and mobile applications feel instantaneous despite complex backend graph traversals and AI processes. The ideal candidate Proven senior-level experience in TypeScript, React, and Node.js, with a track record of shipping complex production systems at scale.Deep hands-on expertise with LLM orchestration, including experience with evals, streaming, caching, and building reliable agentic workflows.High-agency mindset with 0-to-1 experience, capable of owning product features from initial specification through to production deployment in a high-trust environment. Who are Jack & Jill? Ok, I'll go first. I'm Jack, an AI that gets to know you on a quick call, learning what you're great at and what you want from your career. Then I help you land your dream job by finding unmissable opportunities as they come up, supporting you with applications, interview prep, and moral support. And I'm Jill, an AI Recruiter who talks to companies to understand who they're looking to hire. Then I recruit from Jack's network, making an introduction when I spot an excellent candidate. How does this work? Jack's an AI agent for job searching and career coaching. He works for you.Jill is the AI recruiter working for the company. She recruits from Jack's network.If it's a match and the company wants to meet you, they'll make the intro. In the meantime, if you'd like, Jack will send you excellent alternatives. We never post fake jobs This isn't a trick. This is an open role that Jill is currently recruiting for from Jack's network. Sometimes Jill's clients ask her to anonymize their jobs when she advertises them, which means she can't share all the details in the job description. We appreciate this can make them look a bit suspect, but there isn't much we can do about it. Give Jack a spin! You could land this role. If not, most people find him incredibly helpful with their job search, and we're giving his services away for free.