# Antoine Duvauchelle — Product Engineer

> I build design systems, polished UI, and the guardrails that let teams — and agents — ship them.

Ten years shipping production frontends, from startup studios to the booking funnel of Rail Europe. I care about the last 10% (interaction details, accessibility, perceived speed) and about making the right path the easy one for whoever builds next.

Before code, I was a journalist. I still write docs as if someone is actually going to read them.

## Case studies

- [Modernising a ten-year-old booking platform, one layer at a time](https://www.toyn.dev/work/rail-europe-migration/): Instead of a rewrite, a revamp — a legacy Rails monolith moved toward modern Rails and Hotwire, the mobile apps brought onto the same codebase, and booking pages made to feel faster.
- [A SvelteKit rebuild, stopped at 80% — and the team I helped hold together](https://www.toyn.dev/work/rail-europe-sveltekit/): First in-house engineer on a from-scratch rebuild of the B2C booking site, alongside a team of consultants. Developer, Scrum Master and facilitator — and, for months, a bit of the missing roles too.
- [dadama — an AI-built data-journalism engine, with guardrails](https://www.toyn.dev/work/dadama/): A framework-free static site generator for data stories, built with Claude Code in a few days. The interesting part isn't the speed — it's the frame that kept the agent honest.
- [Designing and building a calmer mental-health app](https://www.toyn.dev/work/holivia/): The whole frontend of a mental-health platform, designed and rebuilt — including a calming audio player and video calls with therapists, in vanilla JavaScript, CSS and HTML.

## Writing

- [The thing is, I love coding](https://www.toyn.dev/writing/the-thing-is-i-still-love-coding/): You can keep saying that the value isn’t in the code, and that this was true even before the age of AI; I still love it as a practice.
- [Framing the agent: how this site was built](https://www.toyn.dev/writing/framing-the-agent/): A walkthrough of the context, decisions and automatic checks that let a coding agent build this portfolio without making things up.

## Résumé

- [Résumé](https://www.toyn.dev/resume/): experience, projects, skills, languages and education, printable as a PDF.

## Design system

- [Design system](https://www.toyn.dev/system/): tokens, contrast checks and component contracts, generated from the code.
- [Design system as Markdown](https://www.toyn.dev/system.md): the same tokens and contracts, for agents. Follow it when changing the site.

## Optional

- [LinkedIn](https://www.linkedin.com/in/antoine-duvauchelle-333184433/)
- [Codeberg](https://codeberg.org/toyn)
- [GitHub](https://github.com/aduvau)