Julien Sebag

Available to hire

👨‍💻 After working two years as a Product Designer at Nielsen in Warsaw, and one year as Design Engineer / Front End Developer at wibas etarate in Hamburg, I decided to switch my career to become a UX engineer.

About

👨‍💻 After working two years as a Product Designer at Nielsen in Warsaw, and one year as Design Engineer / Front End Developer at wibas etarate in Hamburg, I decided to switch my career to become a UX engineer. Now, I have four years of experience in front end development.

💡 Currently, I am working as Senior Front End Developer @ GIE G5 Languedoc

💼 Through my studies, bootcamps in UX / UI Design, Web Development and AI Engineering, MSc in Creative Technology, and Masters in Marketing and Advertising, I have gained skills in user research, UI and UX design, development languages, AI and LLMs. My current position is Senior Front End Engineer @ GIE G5 Languedoc in Nîmes (FR), working on the website Parasanté online.

🗣 I am fluent in French and English.

🖥 I am technically proficient in: HTML | SCSS | JS | React | Liquid | Git | Github | Figma | Node.js | Express | MongoDB, and have knowledge in: Python | Flask | SQLite | Handlebars | Webflow | Adobe suite.

✉️ If my profile interests you, you can contact me here or by email at Email not available. Sign in: https://www.twine.net/signup

📓 Check my portfolio here: Website not available. Sign in: https://www.twine.net/signup

  • Joined September 2025

Languages

  • FrenchFluent
  • EnglishFluent
  • GermanBeginner
  • Spanish; CastilianBeginner

Industry experience

  • Software & Internet
  • Professional Services
  • Media & Entertainment
  • Education

More experts in Amsterdam, Netherlands

Projects · 2

Challenge

For this project, I had to create a chatbot. I built an AI-powered React component generation service that transforms text descriptions and UI mockup images into production-ready React code using OpenAI’s GPT-4 and Vision models.

Key Features Implemented

Smart Code Generation: Natural language to React/TypeScript components with Tailwind CSS styling by default.
Image Analysis: Upload UI mockups and get corresponding React code using OpenAI Vision API.
Contextual Learning: Vector similarity search via Pinecone database for relevant code examples.
Interactive Chat Interface: Real-time conversation-based development workflow with session management.
Automated Knowledge Base: Population from HuggingFace datasets and custom code snippets.

Technical Architecture

Backend: Flask API with OpenAI integration, MongoDB for storage, Pinecone for vector search, Cloudinary for image processing.
Frontend: React/TypeScript with Vite, featuring drag-drop image upload, real-time messaging, and code syntax highlighting.
AI Pipeline: LangChain orchestration with LangSmith monitoring, custom prompt engineering for React best practices.

Special Features

Automatic detection of boilerplate requests redirects users to my custom CLI tool (@julseb-lib/julseb-cli), showcasing a complete AI-powered development ecosystem.

See the full project here: [https://www.twine.net/signin
[See the project on Github](https://www.twine.net/signin

React generator chatbot
  • Developer

Tired of using Bootstrap and other heavy CSS frameworks, and reusing a lot of components at my job and in my personal projects, I decided to create my own React components library to save time on the development process. The idea of julseb-lib was to make a lightweight, complete, easy to use and to personalise components library. It is of course responsive. I decided to use TailwindCSS to ease the development process and personalisation.

Library

Design and development of the library in React and TailwindCSS.

Utils

Creation of an npm package with basic TypeScript functions.

CLI

Creation of a CLI to generate boilerplates using this library.

See the project here; [https://www.twine.net/signin
[See the project on Github](https://www.twine.net/signin

@julseb-lib
  • Developer

Work experience· 6 roles

Senior Front-End Developer · MarmaladeJul 2024 – Sep 2025 · 1 yr 3 mos

Built agency-owned products using React and Next.js. Contributed to client projects using Angular, delivering scalable front-end architectures, improving load performance by 25%.

Front-End Developer · NielsenJan 2024 – Sep 2025 · 1 yr 9 mos

Developed internal tools in React, TypeScript, and GraphQL.

Front-End Developer · Venture LeapJul 2022 – Sep 2025 · 3 yrs 3 mos

Front-end development for several clients of the agency, working mainly with Symfony.

Product DesignerSep 2021 – Sep 2025 · 4 yrs 1 mo
Product Designer · NielsenJan 2020 – Sep 2021 · 1 yr 9 mos
Design Engineer · wibas etarateOct 2018 – Dec 2019 · 1 yr 3 mos

Education· 5

AI Engineering Bootcamp · Ironhack, Remote2025

Bootcamp focused on Artificial Intelligence, Machine Learning, and data analysis.

Web Development Bootcamp (MERN stack) · Ironhack, Berlin2021 – 2025

Bootcamp focused on MERN stack. Projects: JavaScript game, event app, artists booking app

UX / UI Bootcamp · Ironhack, Paris2018 – 2025

Projects: design for iOS apps, UX and UI: design thinking, user research, personas, wireframing, prototyping on Sketch and Flinto.

MSc Creative Technology · Middlesex University, London2016 – 2017

Final project: Mobile application and website for real estate, helping people to find easily a place to live.

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