I rebuild it — module by module, while it keeps running. Every calculation is verified against your old system before it goes live. You don't have to trust me. You can check.
No lock-in. Each module works on its own — you can stop after any one.
A 15- or 20-year-old system still runs the business — but the vendor is gone, the one developer who understood it has retired, and every outage is a gamble. Replacing it wholesale is too risky. So it stays, and the risk grows.
No big-bang rewrite. One module at a time, each one proven to behave exactly like the system it replaces — before it touches production.
Orders, pricing, routing, invoicing — rebuilt one piece at a time. The old system keeps running until each new piece has earned its place. No downtime, no forced switch-over.
Before a rebuilt module goes live, it is run against the legacy system on real cases. If the numbers don't match to the cent, it doesn't ship. Your old software becomes the reference that proves the new one right.
I build with orchestrated AI systems working in parallel — one builds, a separate, independent one reviews before delivery. The speed of a team, with one person accountable for the result.
The point of all this is simple: you don't have to take my word for it. The verification is the deliverable as much as the code — you can see that the new system matches the old one, case by case.
I'm early. Rather than borrow credibility I don't have yet, here is exactly what's on the bench right now.
Ordering, pricing logic, delivery routing and invoicing are being rebuilt one module at a time and verified against the legacy system on real data, while day-to-day operations continue uninterrupted.
An installable web app (PWA): audio-guided sessions recorded by the coach, a daily log, progress view for the coach, GDPR export and deletion path. Built once, updates instantly, runs on EU servers.
Nothing on this page is embellished. Where something is in progress, it says so.
Often the new face of a rebuilt system is a small, focused app. Installable on any phone, updated instantly, hosted in the EU — from an internal tool to a customer-facing one.
A progressive web app installs straight from the browser. No app-store review, no waiting, no 30% cut. You push an update, everyone has it.
Not a bloated platform your team has to learn. A tool that does the one thing your business actually needs, in the words your business already uses.
Your data stays in the EU under GDPR — on request entirely without third-party cloud. Export and deletion paths are part of the build, not an afterthought.
Self-built prototypes run on your machine — and break with the first real user: data loss, no access control, no privacy compliance, no tests. I take it into production.
I read the code and deliver in writing: what holds, what breaks, what's missing (security, privacy, data, tests). Plus a fixed price for the rebuild. The audit is €490.
Separate build and review instances, tests against existing behavior, mobile and GDPR checks, deployment on a German server with backups. Fixed price after the audit.
Documented, no license fees. Hosting and maintenance from €79/month if you want it.
No project without an assessment, no assessment without a fixed price. You know what it costs — and whether it's worth it — before anything is built.
I map the legacy system and the workflows around it: what it does, where the risk sits, what can be rebuilt, what shouldn't be. You get a clear report with a path — with or without working together afterwards.
The report names what pays off, what doesn't, and what's solvable without AI at all.
Request an assessmentOne module after another, typically 2–6 weeks each. The price is fixed before work starts, based on the assessment — no change-order surprises. Each module works on its own; you can stop after any one.
Discuss a projectHosting on EU servers, maintenance, changes, support. Month-to-month, cancel any time. The people who built it are the people who keep it running.
Talk it throughThe biggest worry with AI is data protection — rightly so. Here it's part of the architecture, not a footnote: documented, checkable, on request entirely without cloud.
Anything with personal data is processed by a local AI model, on your hardware or on separate EU servers. It doesn't leave your system.
Complex tasks without personal data can use stronger AI services — but only on data that carries no personal reference. The line is drawn deliberately.
Hosting in the EU under GDPR. On request, a German instance for clients who need data physically in Germany.
Every build includes a clean export and a real deletion path from day one — not bolted on when someone finally asks.
I'm Thomas Siepmann. I rebuild ageing business software and build the focused apps that replace it. No account managers, no hand-offs to a team you never meet — the person who assesses your system is the person who rebuilds it and the person who keeps it running.
I work EU-based and remote, in English and German. For clients within reach, on-site is possible. The way I build — verified against your old system, independently reviewed before delivery — is the same whether you're next door or across a border.
A first conversation is free and commits you to nothing. If a fixed-price assessment makes sense, we set it up. If it doesn't, I'll tell you.
siepmann.t@protonmail.com