Supervised vibe coding: how one developer built a booking platform in three months

Zagreb developer Ivan Babić is building Appointa, a Croatian online booking platform, on his own. An AI agent writes the code; he makes the decisions, sets the rules and reviews every change.

Ivan Babić opened an empty project folder on 14 May 2026. Three months later Appointa had a web app for businesses, public booking pages and two mobile apps, Appointa for clients and Appointa Pro for businesses, live on the App Store and Google Play. Fiscalised invoices and more than 200 video tutorials followed over the next two months. Behind all of it are one person and the AI agent Claude Code.

Vibe coding, with rules

Vibe coding usually means the AI writes the code and nobody reads it. Ivan works differently. He decides what gets built and why, sets the rules and reviews every change. The agent writes the code, the tests and the documentation, and depending on the type of task it uses different models: Fable, Opus or Sonnet.

The rules live in a file the agent reads before every task: write a failing test first, then the code; if a request is unclear, stop and ask; nothing goes into the repository without Ivan's approval. That is why there is almost as much test code as app code.

More than code

The AI didn't only write code. All the video tutorials, in Croatian and English, were recorded without a camera: a script drives the browser through the app and an AI voice (ElevenLabs) reads the narration. AI also helped produce the user manual, the blog articles in two languages and the interactive guided tours. Inside the app, an AI assistant helps users too.

Where AI doesn't help

Some steps no agent can speed up. Apple rejected the first version of Appointa Pro because it had the same icon as the client app. For personal developer accounts, Google requires at least 12 real people to test an app for 14 days before it can go live. Fiscalisation certificates, terms of service and GDPR still need a human.

"I write less code than ever and make more decisions than ever. The agent writes the code and the tests; I decide what we build, set the rules and review every change before it reaches users." — Ivan Babić

Booking without commission

Appointa is online booking software for salons, studios and practices across 29 industries, from hairdressers and beauticians to physiotherapists, dentists and personal trainers. Clients book on their own through a public page or the app, and the owner runs the calendar, clients and invoices from the web or a phone. Unlike the big platforms, Appointa takes no commission and never shows clients competing businesses. The interface is in Croatian and English, and data is stored on servers in the EU.

The Starter plan is free for up to 30 appointments a month. Pro costs €20 a month and Premium €40. Appointa can be tried at appointa.hr, and a demo salon is at appointa.hr/en/s/demo-salon-lara.
