Founding Senior Full-Stack Engineer at stealth-stage AI coordination startup

Company: Jack & Jill
Apply for the Founding Senior Full-Stack Engineer at stealth-stage AI coordination startup
Location: London
Job Description:

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.

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Posted: June 1st, 2026