nix-darwin reference workflow

Use this skill for Darwin/macOS Nix work in this repo. Keep it out of the global agent rules: this is reference workflow, not behavior that belongs in every prompt.

First checks

• Verify the host before host-specific rebuilds or Darwin/NixOS decisions: hostname and uname -a.
• Edit repo sources, not generated targets. Runtime files under ~/.config, ~/.claude, ~/.pi, and similar paths are usually Nix-store symlinks.
• Prefer repo wrappers for validation: hey check for current Darwin host, hey re or full darwin-rebuild for local rebuilds.
• Avoid generic nix flake check on macOS in this repo because it evaluates NUC outputs and can hit known cross-system noise.

Primary references

Use the narrowest reference that answers the question:

Option lookup order

1. Use local docs first when available:
   • darwin-help for browser-based reference.
   • man 5 configuration.nix for terminal lookup.
2. Use the online nix-darwin reference when local docs are unavailable or stale.
3. Search this repo for existing patterns before adding a second convention.
4. Use source-level nix-darwin docs only when option reference docs are not enough.

Install notes

• nix-darwin requires a Nix implementation; Nix and Lix are both supported.
• The nix-darwin README recommends the Lix installer because the official Nix installer has no automated uninstaller, manual macOS uninstallation is complex, and Lix supports both flake-based and channel-based setups.
• The installer does not decide which Nix interpreter the system uses later: nix-darwin manages the Nix installation by default and defaults to upstream Nix. To keep Lix, set nix.package = pkgs.lix in configuration.
• Flake-based nix-darwin installs use darwin-rebuild switch; before darwin-rebuild is installed, bootstrap with sudo nix run nix-darwin/<branch>#darwin-rebuild -- switch.

nix-build notes

Use nix-build only when a legacy/channel workflow needs it. Prefer nix build or repo wrappers for normal flake work.

Important details from the Nix manual:

• nix-build is distinct from nix build; use man nix3-build or nix build --help for the modern command.
• Successful nix-build creates result symlinks by default, which become GC roots until removed.
• --no-out-link avoids creating the symlink and GC root.
• Common useful flags: -A/--attr, --arg, --argstr, --dry-run, --out-link.