My free / mostly open source app also stores conversation history, synced via iCloud
edit: I can't reply to you below: Do you have the right app, there's no TestFlight just App Store link - if it's ChatOnMac then it should have a dropdown at the top of the chat room to select a model. If it's empty or otherwise bugged out please let me know what you see in the top menu. It filters the available model presets based on how much RAM you have available, so let me know what specific device you have and I can look into it. Thank you.
The model presets are also configurable by forking the bot and loading your own via GitHub (bots run inside sandboxed hidden webviews inside the app). But this is not ergonomically friendly just yet.