<announcement> "I'm using the rebuild skill to apply configuration changes." </announcement> <context> Session-context hook provides User and OS at session start. Use this to determine rebuild strategy: - NixOS: Use nixosConfigurations with username from session - Non-NixOS: Use homeConfigurations with username@arch-linux format </context> <prerequisite> Nix reads from git index, not working tree. Stage all modified files before rebuilding: `git add specific-file.nix` for each changed file. Never use `git add -A` or `git add .` (may stage unrelated parallel work). </prerequisite>

<simple_rebuild> Primary method: ./bin/rebuild (or ~/bin/rebuild). Auto-detects platform and user dynamically. Sources nix-daemon.sh if needed. Handles backup naming.

NixOS: Runs sudo nixos-rebuild switch --flake ~/.dotfiles#$(whoami) Non-NixOS: Runs home-manager switch --flake ~/.dotfiles#$(whoami)@$(arch)-linux </simple_rebuild>

<nix_not_found> If nix: command not found: source the daemon profile first. . /nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh Then retry the rebuild command. </nix_not_found>

<dry_run> Validate configuration before applying. Substitute USER with actual username from session:

NixOS: nix build ~/.dotfiles#nixosConfigurations.USER.config.system.build.toplevel --dry-run Non-NixOS: home-manager build --flake ~/.dotfiles#USER@x86_64-linux --dry-run

Dry-run catches syntax errors, missing imports, and evaluation failures without modifying the system. </dry_run>

<platform_difference> NixOS: Full system rebuild with sudo nixos-rebuild switch --flake. Requires sudo. Affects system services, kernel, boot. Home-manager is integrated as a module.

Home-manager standalone: User-level only with home-manager switch --flake. No sudo needed. Affects user packages, dotfiles, services.

Detection: Check /etc/os-release for ID=nixos, or use OS from session-context. The bin/rebuild script handles this automatically. </platform_difference>

<workflow> 1. Make .nix file changes 2. Stage changed files: `git add path/to/changed.nix` 3. Dry-run to validate: use command from <dry_run> with correct username 4. If dry-run passes, apply: `./bin/rebuild` 5. Verify changes took effect

On NixOS: May need to ask user to run rebuild (requires sudo). On home-manager standalone: Execute directly, no sudo needed. </workflow>

<troubleshooting> Build fails with import error: Check file exists and is staged (`git status`). Attribute not found: Verify module is imported in appropriate home.nix or configuration.nix. Check flake has matching config for username. Unfree package error: Check NIXPKGS_ALLOW_UNFREE=1 is set (bin/rebuild does this). Rate limit errors: Install home-manager locally: `nix profile install nixpkgs#home-manager`. Wrong user config: Check session-context User field matches flake configuration name. </troubleshooting>

<post_rebuild> After rebuild, verify changes applied. Test it and check services are running, dotfiles updated, packages installed as expected. If issues arise, review rebuild output for errors. Re-run dry-run to catch config problems. </post_rebuild>