We are right around the corner from NixCon 2026 . Another year where I sadly won’t be present. I looked at the lineup and saw quite a few talks on dynamic derivations, along with some recent other posts on the topic such as cargo-dyndrv which had me thinking about revisting the topic since my earlier posts on the subject. I wanted to better understand the implications of dynamic derivations and how they change the build graph. Originally, I was focused on how it could replace the lang2nix style of build graph generation, but I realized that the implications are much broader than that. The graph does not need to be known up front. It can be defined as the build progresses. 🧐 What do I mean? Traditionally, Nix requires you to ask it to build anything and it will tell you exactly the steps it will take ahead of time as the “derivations” that comprise the build graph. $ nix-store -q --requisites \ $ ( nix-instantiate '<nixpkgs>' -A hello ) | grep -c '\.drv$' 196 This is an important property of Nix.…