Quentin Guislain
Product Design Lead · Munich
I design for trust between buyers and sellers who have never met.
Since March 2023, I have led product design for all of buycycle, a European marketplace for pre-owned bikes, components and sports equipment. Since January 2026, I have done that work directly in code, in Claude Code, using a framework I built and made readable for AI.
Projects
- buycycle Case study · App and web · 2024 – 2026 Bringing questions and offers into one private chat Public comments and a separate offers tool became one private chat between buyer and seller. After purchase, each sale runs through that same thread until delivery. I was the only designer on web and in the app, except for the claims flow, which I scoped and then handed over to our second designer. 3 in 4 bike sales follow a conversation between buyer and seller, and 6 in 10 follow an offer.
- buycycle Case study · Shipping · 2025 – 2026 Guiding buyers and sellers through shipping, inside the chat Order tracking used to sit in a separate section. Shipping now happens inside the conversation, across two shipping flows and five teams. As the only designer, working with a PM who coordinated the teams, I turned the requirements of five teams into clear next steps for buyers and sellers. Since June 2025, every shipped order has been tracked in the conversation.
Across the product
- buycycle Short case · Product page · Web and app Redesigning the product page to help buyers decide Seller contact requests rose 19.5% and favorites rose 20.3%.
- buycycle Short case · Search · App Redesigning search for a multisport catalogue From 9 to more than 200 sub-categories, in one search structure.
- buycycle Short case · Chat · App and web One inbox for buying and selling On small screens, separate sections made it easier to miss a conversation.
Ways of working
-
January 2026
Designing in code
I made working prototypes in Claude Code a core part of our design process. I built a framework that combined buycycle’s design system with a model of its eleven core marketplace objects, their states and the actions available in each. That let me design at production fidelity, using buycycle’s own components and keeping new interactions consistent with how the marketplace already worked.
In September 2026, I started opening my own merge requests in the web and app repositories. I also began integrating the framework with the design system in code so Claude could draw on the same components and product rules when working directly in the codebase.
The only designer on the whole product: more than 50 initiatives, almost all of them live.
- Claude Code
- buycycle database MCP
- Linear
- Notion
- GitLab
-
2023 – 2025
Building the design function
I built buycycle’s design function from scratch and managed two designers, an intern and a UX writer. I set out how we worked: adapt the process to the project, share rough drafts early and test assumptions before committing to a solution.
The designers owned key product flows. I set up critiques so they could develop their work with peers and regular sessions with Product and Engineering. In stakeholder reviews, I backed the designers when they needed support or when a decision affected other parts of the product.
- Figma
- Notion
- Linear
- Mixpanel
About
Before design, I spent ten years in marketing, from performance marketing to Head of Marketing and then CMO, working alongside founders. That experience taught me to ask what a design decision needs to achieve for the business.
- Based in
- Munich
- Languages
- French (native), English and Italian (bilingual), German (B2), Spanish (intermediate)
- Contact
- quentin.guislain@gmail.com · LinkedIn