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# Full-Stack Engineer - Mainloop

- **Company:** LEYTON ET ASSOCIES
- **Location:** Barcelona, Spain
- **Contract:** Permanent contract
- **Skills:** Artificial Intelligence, Strategies of Testing, TypeScript, Backend, Front End Software Development
- **Published:** September 15, 2026
- **Apply:** https://www.buscojobs.com.es/full-stack-engineer-mainloop-en-barcelona-ID-371727295

## About the Role

You'll operate in an AI-native, agent-driven environment, translating business needs into well-architected solutions.
You'll frequently move between projects, influencing architecture, quality, and releases.
This is a hands-on, strategic engineering role with a clear path to growing influence and a prestigious internal certificate upon demonstrated mastery.
Compensaciones / Beneficios * Own the build, architecture, quality and release of a product * Take over and own a product end-to-end after documentation and handoff * Decide what to build next in collaboration with the Product Owner * Work across a portfolio of platforms, agent-native products and internal tooling * Review merges via agent-assisted loop and ensure 100% passing tests * Design with AI agents to balance quality and speed, and judge outputs critically * Mentor teammates and contribute to evolving engineering processes and standards * Contribute to defining the standard stack and participate in architectural governance Responsabilidades * Ownership of production software experience * Front-end and back-end working proficiency * Strong TypeScript or equivalent language proficiency * Experience with tests (unit, end-to-end) and test strategy * Familiarity with coding agents and evaluating agent output * Ability to understand unfamiliar codebases and explain their
purpose * Fluent English; Spanish useful * Willingness to work in Barcelona and participate in a team-building environment Requisitos principales * Mainloop Barcelona certificate * no on-call policy * opportunity to work with AI agents and tooling * growth through cross-project ownership * international exposure * clear ownership of product incidents during work hours

## Description

Experteer Overview In this role you will own production-grade software across a varied portfolio, partnering with a Product Owner to shape robust, scalable products.You'll operate in an AI-native, agent-driven environment, translating business needs into well-architected solutions.You'll frequently move between projects, influencing architecture, quality, and releases.This is a hands-on, strategic engineering role with a clear path to growing influence and a prestigious internal certificate upon demonstrated mastery.Compensaciones / Beneficios * Own the build, architecture, quality and release of a product * Take over and own a product end-to-end after documentation and handoff * Decide what to build next in collaboration with the Product Owner * Work across a portfolio of platforms, agent-native products and internal tooling * Review merges via agent-assisted loop and ensure 100% passing tests * Design with AI agents to balance quality and speed, and judge outputs critically * Mentor teammates and contribute to evolving engineering processes and standards * Contribute to defining the standard stack and participate in architectural governance Responsabilidades * Ownership of production software experience * Front-end and back-end working proficiency * Strong TypeScript or equivalent language proficiency * Experience with tests (unit, end-to-end) and test strategy * Familiarity with coding agents and evaluating agent output * Ability to understand unfamiliar codebases and explain their purpose * Fluent English; Spanish useful * Willingness to work in Barcelona and participate in a team-building environment Requisitos principales * Mainloop Barcelona certificate * no on-call policy * opportunity to work with AI agents and tooling * growth through cross-project ownership * international exposure * clear ownership of product incidents during work hours