I've literally read the code for Signal's double-ratchet protocol. It's extremely high quality cryptography, written in Rust, open source, with several independent audits.
The server code isn't open, but we know they (used to?) use Intel SGX enclaves so the contact metadata is sealed from even the Signal Foundation. Admittedly SGX fell prey to a number of speculative execution attacks, but Signal had no way of foreseeing that.
Also, Moxie hasn't been involved since 2022.
Lockpicks. One day the bathroom door somehow locked from the inside without anyone in there, and I really needed to pee. Really came in handy. ~~Turns out you could just use a flathead screwdriver, there wasn't an actual lock cylinder, but don't take this from me!~~