• •Use nix eval and nix build to experiment with your changes.
• •New files are not discoverable by Nix until you git add them.
• •Prefer lib functions over builtins when both exist (e.g. lib.map over builtins.map).
• •Don't guess hostnames or other configuration names. Use nix flake show or nix repl to discover them.

Exploring flake outputs

• •Use nix flake show to see what a flake exposes.
• •Pipe expressions to nix repl .# for deeper exploration. Flake outputs are loaded as top-level variables (e.g. echo 'builtins.attrNames nixosConfigurations' | nix repl .#).

Looking up documentation

• •Use man configuration.nix to explore available module options. This returns NixOS options on Linux and nix-darwin options on macOS.
• •Use man home-configuration.nix to explore home-manager module options.
• •Use echo ':doc lib.mkIf' | nix repl nixpkgs to check documentation on lib functions. Many include type signatures and examples.

Source-diving

• •Use EDITOR=cat nix edit nixpkgs#<package> to view a package's source. Does not work with modules.
• •Use nix flake metadata <flake> --json | jq -r '.path' to get a flake's store path, then read files directly from it to source-dive modules and other definitions.
• •Never search /nix/store broadly — it's massive and will take forever. Always resolve the specific store path you need first.