Hello. I am Stefan, a freelance software developer with more than 25 years of professional experience, based in Berlin.

Are you looking for help? I'm available for contract work with React.js, Node.js, TypeScript, and AI-based coding.

Experience

I have spent the last 9 years working with React.js, Node.js, and TypeScript for enterprise scale customers and startups. Before that, I have worked with C++, Java, and Ruby on Rails for many years.

I have more than 25 years of professional experience. I have co-founded two companies, worked as a CTO, team lead, and lead developer, and have written two books about Java. I have coached individuals and teams. I am also a Certified Scrum Master.

In recent projects I use agentic coding tools like Claude Code and Cursor to ship features faster.

Skills

TypeScript

React.js

Node.js

AI

Scrum

Testimonials

I have some customer testimonials on LinkedIn.

Portfolio

Billet

CLI tool · AI engineering

A terminal AI coding agent built from scratch on the raw Anthropic SDK — the agentic loop, tool use, and sandboxing, no framework. Built with TypeScript and Bun.

Recto

WEB APP · PRODUCT ENGINEERING

Every book designer who has built a page plan in InDesign knows the moment: you need to insert a page, and now every following page tile has to be moved by hand, every page number updated, one by one. On a 600-page book, that's not a small job — it's the kind of tedious, error-prone work that eats a full afternoon.

“Every time I had to insert a page, I felt like crying.”

Simona, book designer

Most designers skip the page plan entirely and just hold the structure in their head — even though clients want one. Recto exists so they don't have to choose between the two: insert or move a page, and everything downstream updates automatically.

A visual flat-plan tool for print designers that maps a publication the way books are actually made — pages, spreads, and print sheets — built with React, TypeScript, React Router 7, and Supabase.

Smart Rename

macOS app · AI engineering

An AI-powered macOS app that renames documents by reading their content, built with Tauri, React, TypeScript, Rust, and the Vercel AI SDK.

Code

See some of my code on GitHub.

Availability

From July 1, 2026 I will be available for React, Node.js, TypeScript, and AI-based coding work as a contractor, remotely or in Berlin.

Hire me or check out my CV or my GitHub account.