Portfolio

Built, not just planned.

A selection of my work: from first prototype to platform in continuous operation. Each project shows what I do — and how.

01 — Projects

Selected work

From a web shop with a point of sale to a platform built by an AI agent team: more than a decade of products, prototypes and client work.

Featured case · Client project

Built by AI agents

KeyHub

Key management with digital handovers

Built autonomously by AI agents — architecture and sign-off by me. The application runs in production, and the client is taking the agent team in-house.

The brief

A trades business manages a lot of keys — and every handover has to be traceable. KeyHub replaces lists and notes with key management and digital handovers.

How it was built

KeyHub was built autonomously by my AI agent team. I set the architecture, reviewed and signed off; the team handled implementation, tests and documentation. Every change passed automated checks — security scans, unit and browser tests — before it was merged. Only I take the step into production.

The result

KeyHub is running in production. The client is so convinced that they’re taking the agent team in-house — to keep developing KeyHub and further projects of their own with it.

Client projects

Client project · 2021–2025

SYNLAB Suisse

Medical appointment booking

From a few bullet points to the MVP of a medical appointment booking platform in about eight to ten weeks — followed by four years of development and support together with the client.

“No grand plan, no mockups — just delivered. And it held up.”

— Klaus Dobler, responsible for the booking system on the client side

Role: Freelance full-stack developer, sole developer
Status: Completed

Ruby on Rails
Nuxt/Vue
PostgreSQL
Sidekiq
Redis
PWA

Client project · 2024

Real-estate platform with AI back office

AI writes listings from bullet points

The best part is invisible, in the back office: agents enter just three or four bullet points — location, size, distance to the beach. The AI writes the description and fills around seven content fields automatically, in German and English.

Role: The entire development team
Status: Did not go into regular operation

Ruby on Rails
Nuxt/Vue
OpenAI API
PostgreSQL

Client project · 2024–2025

BS-Inventory

Inventory management with QR scanner

Inventory management with a QR code scanner for a supplier of elevator control panels — as an internal intranet application.

Role: The entire development team
Status: In the client's intranet

Ruby on Rails
Nuxt/Vue
PostgreSQL
Redis
Sidekiq
Vuetify

Client project · 2018–2019

Breakdown service fleet management

Tow fleet with digital on-site handover

Management for heavy tow trucks with digital on-site handover and map integration. Since the data source only offered a CSV download, a custom API was emulated on top — until the provider later shipped its own.

Role: The entire development team, as a subcontractor
Status: Pilot

Ruby on Rails
Vue
PWA

Own products

Own product · 2026

Built by AI agents

ValidSlots

Online appointment booking under your brand

ValidSlots bundles my years of experience with large-scale lab appointment booking — rethought and developed further by my agent team in about four weeks, in parallel with ValidLearn. Multiple locations, staff with skills, live calendar, four languages.

Role: Product owner · built by an AI agent team
Status: MVP — ready for its first pilot customer

Ruby on Rails
PostgreSQL
Redis
Sidekiq
Nuxt/Vue
Vuetify
Pinia

validslots.com

Own product · 2026

Built by AI agents

ValidLearn

Learning platform for mandatory training

A lean, auditable learning platform with a clear compliance focus: courses, exams, verifiable certificates and a complete audit trail. Built by my agent team in about four weeks, in parallel with ValidSlots.

Role: Product owner · built by an AI agent team
Status: MVP — design and navigation will be tailored with the first customer

Ruby on Rails
PostgreSQL
Redis
Sidekiq
Nuxt/Vue
Vuetify
Pinia, LDAP, Vitest, Playwright

validlearn.com

Own product · 2026

trendgegner.com — The Logbook

A terminal blog as a time capsule

A blog that looks like a terminal: a logbook of the first month with Claude Code — from the first command to the BobNet. Try a few commands and you'll find Easter eggs.

Role: Author and developer
Status: Time capsule, as of July 2026

trendgegner.com

Own product · 2023

FreakFunnels

AI funnel and website builder

An AI-powered builder — itself programmed largely without AI assistance. At its core: a custom AI playground, custom model training and voice-to-website — say a few sentences and the website appears.

Role: Founder and developer — solo, in two to three months
Status: Closed beta 2023

Ruby on Rails
Nuxt/Vue
Vuetify
PostgreSQL
Redis
Sidekiq
OpenAI API, Whisper

Own product · since 2023

clockNbill

Time tracking with invoices and quotes

Time tracking with lean invoicing and quoting — in productive daily use for years.

Role: Owner and the entire development team
Status: In own use

Ruby on Rails
Nuxt/Vue
PostgreSQL
Redis
Sidekiq
Vuetify

Own product · for about 10 years

My own tools

Monitoring, database, sports

Small tools built for my own needs: monitoring for my applications, a custom database manager and a sports app.

Role: Development
Status: In own use

Open source

Open source · since 2026

Built by AI agents

BobNet Engine

Open-source engine for AI agent teams

The engine behind my agent teams: fixed roles, separate responsibilities for building and reviewing, second review by models from different vendors, and human sign-off.

Role: Development, architecture and sign-off
Status: In daily use

Claude Code
OpenAI Codex
MCP

BobNet

Past roles

Role · 2014–2015

shyftplan

Shift planning with HR features

The first shift-planning MVP was built solo in about six weeks; afterwards the company raised funding. Later came work on the mobile apps and their APIs.

Role: Freelance developer — first MVP solo, later backend and mobile in the team
Status: Completed

Ruby on Rails
Meteor.js
REST API
iOS
Android

Role · 2016–2018

Smunch

Online canteen for offices

Built and evolved an online canteen for office orders, including custom integrations with payroll accounting.

Role: CTO — the entire development team for the first two years
Status: Completed

Ruby on Rails
Docker
DATEV
Sage

Role · 2014–2015

hellocare

Marketplace for caregivers

A marketplace for caregivers with geographic search and payments — developed further in the ProSiebenSat.1 accelerator.

Role: Co-founder and developer — the entire development team during the build-up
Status: Completed

Ruby on Rails
PostgreSQL
jQuery
Azure
Braintree

Role · 2013–2014

Orderlift

Web shop meets point of sale

Web shop and point-of-sale system in one, for smaller local stores. Onboarding worked via CSV import of existing product data.

Role: Founder and developer — the entire development team
Status: Completed

Ruby on Rails
PostgreSQL
AngularJS
jQuery
Sass

Role · 2018–2020

BesserWerker

Full-stack PWA

As co-founder and CTO, I was responsible for the complete full-stack development of a progressive web app.

Role: Co-founder and CTO
Status: Completed

Ruby on Rails
Vue
Nuxt
PWA

Role · 2015–2016

James UG

Event job placement

An application that matches students with trade-fair and event jobs.

Role: Developer — the entire development team
Status: Completed

Ruby on Rails

Your project could be the next one here.

A few bullet points are enough to start. I'll get back to you with questions and a first proposal.

Start a project