We work agent-first, so we would like to see how you work with coding agents. Run one command on your own machine: it reads names, counts and dates from your agent setup (never your code or the contents of your files) and keeps a copy of exactly what it sent. Use the same email you apply with, and we will match it to your application. It can only count in your favour. Full-Stack Product Engineer Own a product end to end — the users, the roadmap, the build and the release — with nobody standing between you and the people who use it. Mainloop is a new engineering team inside an established international group . We are in Barcelona, we are being built from scratch this year, and we have the backing, the customers and the product portfolio of a company that has been around for decades. You get the interesting part of a new team without the part where you check whether payroll clears. Two more things about where this comes from and where it goes. The group has been running a tech lab in Casablanca for more than eight years — Barcelona is its second, built to sit closer to the teams we build for, and AI-native from the first commit, because it starts from a blank page. And the plan does not stop at internal work: within about a year and a half we intend to externalise — external clients, our products sold on the market, products developed for it. You would arrive at the start of that curve, not after it. What we build is the software that automates professional-services work — across roughly fifteen countries, for businesses that are drowning in process. The other half — this half — takes what is proven and owns it for years. This is the seat where the product and the engineering are the same job. Not a slice of it, and not the tickets someone else wrote about it. You decide what it should do next,



you build it, you ship it, and you find out whether it worked. You talk to the people who use it. There is no one above you writing the roadmap for your product and no one below you writing the stories. You build it, front to back. The interface, the logic underneath, the data it keeps. You decide whether a feature makes sense on the screen and whether it holds up behind it, which is exactly the judgement that gets lost when those two calls belong to different people. You ship it and you measure it. A feature is not done when it merges; it is done when people use it and the number moves. You own that number — time saved, errors avoided, uptake — and you report it whether it flatters us or not. How this differs from the Full-Stack Engineer seat A Full-Stack Engineer works beside a Product Owner , who holds the business relationship and the roadmap, and owns the build, the architecture and the release. A Full-Stack Product Engineer holds both halves — on products small enough, and close enough to their users, that splitting them would only slow the product down. If you want to go deep on architecture and let someone else hold the room, the Full-Stack Engineer ad is the better fit. If you care as much about whether a feature should exist as about how to build it, this one is. Every change is reviewed by an agent before a person signs it off. Every build ships tests,



and the gate is 100% pass. Anything AI-powered ships with evals — a scored set of inputs, not "it looked right when I tried it". "In this seat the risk is not slow software, it is fast software nobody needed. Agent code compiles, passes the test it wrote for itself, and is subtly wrong in ways only someone who understands the product will catch. Something we are building alongside the team, and we think it is genuinely unusual. Over your first two to three years here you work through a defined body of knowledge — our architecture, the agentic build method, how to take a product from an idea to something a business depends on, and how to run it well. When you have covered it and can demonstrably run a project our way, you are awarded the Mainloop Barcelona certificate . It is yours. It goes on your CV, and we intend to make it mean something in this market — a signal that the person holding it knows how to build production software with AI agents to a standard, not just prompt their way to a demo. We are investing in making it prestigious , because a team whose alumni are sought after is a team good people want to join. No rota, no pager, no phone number. If something breaks at 3am on a Saturday it is fixed on Monday morning — deliberately. We protect against that with engineering, not with people's evenings: infrastructure as code, restores we have actually tested, one-click rollback. it is part of owning the thing, and it keeps you honest about quality. We are building the team this year, and you will shape how it works. You have shipped something people used, and you watched them use it. You are comfortable across the front and the back of a web application. Strong TypeScript if you have it;

📌 Full-Stack Product Engineer (España)
🏢 Leyton
📍 España