`nvidia-smi` shows that my driver version is 550.78. I ran `nixos-rebuild switch --upgrade` yesterday. My nixos channel is `nixos-unstable`.

Do you know something I don't? I'd love to be on the latest version.

I should have written my post better, it implies that 555 does not exist in nixpkgs, which I never meant. There's certainly a phrasing that captures what I'm seeing more accurately.

Are you using flakes? If you don't do `nix flake update` there won't be all that much to update.

I am! I forgot about this. Mental model check happening.

(Still on 550.)

I did not mean to chastise you or anything, just to suggest you could be able to have a newer driver if you had missed the possibility.

The thing is, AFAIU, NVIDIA has several release channels for their Linux driver[1] and 555 is not (yet?) the "production" one, which is what NixOS defaults to (550 is). If you want a different degree of freshness for your NVIDIA driver, you need to say so explicitly[2]. The necessary incantation should be

  hardware.nvidia.package = config.boot.kernelPackages.nvidiaPackages.latest;

This is somewhat similar to how you get a newer kernel by setting boot.kernelPackages to linuxPackages_latest, for example, if case you've ever done that.

[1] https://www.nvidia.com/en-us/drivers/unix/

[2] https://nixos.wiki/wiki/Nvidia

I had this configuration but was lacking a flake update to move my nixpkgs forward despite the channel, which I can understand much better looking back.

Thanks for the additional info, this HM thread has helped me quite a bit.