Founding Product Engineer (£70K – £120K + Equity) at cubic

Company: Jack & Jill
Apply for the Founding Product Engineer (£70K – £120K + Equity) at cubic
Location: London
Job Description:

Founding Product Engineer

Salary: £70K – £120K + 0.10% – 1.00% Equity

Company Description: cubic – VC-backed AI-native replacement to GitHub

Location: London, UK

Job Description: Join cubic as our first Founding Product Engineer to build the world’s first AI-native code review platform. Working alongside ex-Instagram and Tessian founders, you will own features end-to-end, from ideation to launch. You’ll help redefine how top-tier engineering teams like n8n and Resend collaborate when AI writes the code.

Why this role is remarkable:

  • Exceptional traction with 50% MoM ARR growth and a high-profile customer base including the Linux Foundation, n8n, and Granola.
  • Elite backing from Y-Combinator (X25) and top builders like PeakXV (Sequoia India), Vercel Ventures, and the founders of Resend and v0.
  • Opportunity to shape a new product category alongside a team of four repeat founders in a high-velocity, high-autonomy environment.

What you will do:

  • Architect and build core product features using a modern stack including Next.js, React, Prisma, Inngest, and the Vercel AI SDK.
  • Own the entire product lifecycle from initial user research and prototyping to production deployment and rapid iteration.
  • Collaborate directly with the founders to define the technical roadmap and the future of AI-native developer tools.

The ideal candidate:

  • At least 6 years of professional software engineering experience with a track record of building and shipping end-to-end products.
  • Deep technical proficiency in the React/Next.js ecosystem and a passion for crafting high-quality user experiences and product outcomes.
  • Proven self-starter mentality evidenced by significant side projects, open-source contributions, or previous experience in early-stage startups.

Next steps:

  1. Visit our website.
  2. Click ‘Talk to Jack’.
  3. Talk to Jack so he can understand your experience and ambitions.
  4. Jack will make sure Jill (the AI agent working for the company) considers you for this role.
  5. If Jill thinks you’re a great fit and her client wants to meet you, they will make the introduction.
  6. If not, Jack will find you excellent alternatives. All for free.

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Posted: June 20th, 2026