Good question! There's a couple reasons.

One is that I think it is simpler for the end user to not have to add their own keys. It allows them to start for free and is less friction overall.

Another reason is that it allows us to use whichever models we think are best. Right now we just use Anthropic and OpenAI, but we are in talks with another startup to use their rewriting model. Previously, we have used our own fine-tuned model for one step, and that would be hard to do with just API keys.

The last reason that might be unpopular is that keeping it closed source and not allowing you to bring your keys means we can charge more money. Charging money for your product is good because then we can invest more energy and effort to make it even better. This is actually beneficial to you, the end user, because we can invest in making the product good. Capitalism works, cheers.

Per your last question, I do advise you use git so that you can always revert to return to your old file state! Codebuff does have a native "undo" command as well.