2.18.5 is the newest stable version of nix.
2.19+ has regressions, notably in performance and security.
So if you use 2.24.x, know that you are intentionally using an unstable version that may have issues on your system.
If it eventually stabilises well enough for NixOS, you will get that newest version automatically when you upgrade to 24.11 or whatever release it shows up in.
2 Likes