I used AI, namely Claude Opus 4.8, to create native client for Mattermost using Slint with Rust bindings. To create such application you don't need AI, it's GUI and cross-platform and for exercise purposes it was perfect.

I manage to create functionally correct application but it fall very short in performance and required constant logic validation. GUI components also required constant oversight and manual fixing since AI was simply unable to fix it and gone in circles doing exactly the same thing 2 steps back. Sometimes it even broke perfectly correct component for no apparent reason

Lastly it tends to load data from server in very suboptimal way, ex. for each comment it loaded user profile often repeating request.

After a week I had GUI app which lacks in UI and no-one would use.

The same application to develop manually would take considerable longer but application would be useable and fixing above issues most likely would take longer due to accumulated tech debt