You should read the docs. It's impressive.

I get where you're coming from, but after readinhow badly security is implemented in iMessage frankly I trust the Beeper devs more than Apple.

Get this, iMessage delivers the AES encrypted message in a package with the AES key, that package is encrypted with your RSA key.

iMessage lacks forward secrecy. So if anyone ever got your RSA key, they could read all your messages, including past messages, because your RSA key never changes!

I assume you're not using iMessage anyway then because Apple's Messages stack isn't open source. If you're not using iMessage anyway, it shouldn't matter to you what Beeper Mini is doing. This app isn't for the ultra paranoid. Neither is Google's RCS in Google Messages. This is where Signal and Matrix would be better choices. If you are using iMessage on an Apple device, you're choosing to trust Apple despite their app being closed source and you're not choosing to trust Beeper, which is fine and I don't judge you at all for that stance. But at that point, your qualms aren't simply about Beeper Mini being closed source, the implication is that you don't trust Beeper as a company and/or its developers which, again, is a valid stance even if it's one I don't share.

But I am personally pretty sure I can trust Beeper and Apple enough with my relatively meaningless conversations.