Your API key is only stored client-side, on the server-side only a hash of it is stored. Your entire chat history is encrypted/decrypted on the client-side so there is no way someone else can read your history.

It's an Open Source project, if you want you can host it yourself. https://github.com/aminmarashi/gpt-api-companion/tree/main/c... I'll add a Github badge to build some trust.

Edit: you can read more in this page https://chat.lit.codes/privacy-and-security

It already mentions the GitHub repo, so I'm not adding the badge.