AI app development agency
Fessburn is a product studio in Warsaw and Poznań. We take an app from the first screen in Figma to production code in the App Store and Play Store, and one team does the research, the design, and the build.
We've shipped our own app too. InvoiceRate is a KSeF invoicing app that we designed and built, and 3,000+ people use it.
Right now, with how capable AI tools have become, a founder can build a working MVP in a weekend. What a lot of people don't understand is that not all problems show up in the demo. Some only show up once you push to production and people start using it live, like sign-up flows that lose people, and data that any logged-in user can read.
An app with AI features adds its own problems on top of that. Real users paste in messy data, and the app needs a recovery path for each wrong answer the model returns. That's the part of an AI app we design first.
Each stage has its own project with a fixed price. Pick the one that matches where you are now.
You have an idea
We build the flow you're least sure about, about 5 to 8 screens, on a live URL, and test it with 5 to 8 people from your user group. At the end, you get a fixed price for the full build, or our recommendation to stop.
Your MVP has users
You built the MVP with a tool like Lovable or Cursor. We go through the app the way a new user and a senior engineer would, and give you a ranked fix list and our view on fixing it or rebuilding it.
Your AI feature is live
We run up to three AI flows with realistic and messy inputs, log every failure mode and disclosure gap, and show you the recovery path we'd design for each one.
You know the scope
We design and build the app in one team, with a design system connected to your production code, and we hand over the code, the documentation, and the accounts at launch.
Hosting and third-party service costs aren't included in the build price. Support after launch is our Keep plan, from €4,500 a month.
Our own app
Polish sole traders use InvoiceRate to send invoices, pull their purchase invoices from KSeF, and get their records ready for the accountant, all from their phone. 3,000+ people use it.
AI product
We designed the onboarding and the conversational guidance for an AI content platform that opened on a blank prompt box. Support requests from first-time users dropped by 90%.
Mobile app
We designed the mobile scanning flows surgical teams use to account for every instrument. Preparation became 75% faster, and overall operation time dropped by 40%.
Yes. The Build covers web and mobile apps for iOS and Android, including the AI integration, with the disclosure and recovery states designed in.
Yes. That's what the Product Readiness Review is for. We read the code and the app, and tell you if we'd fix it or rebuild it, with a ranked fix list either way.
You do. At launch, we hand over the code, the documentation, and the accounts.
No. We work asynchronously in the files and repository you already use, with agreed review points and a written update every week. If you want a call, you can always book one.
Send us the app idea or the link to your MVP, and the question you're stuck on. We'll reply with the project we'd recommend and its fixed price.