Nothing in this repo ever evaluated the configurations except a manual rebuild of whichever host was in front of you. That is why a syntax error sat on main for a month and why server-arm has never evaluated: neither host gets rebuilt by hand. * flake: expose all four hosts under `checks`, so `nix flake check --all-systems` covers laptop, server, server-arm and macmini. With --no-build this is eval-only and needs no macOS runner -- evaluating a nix-darwin config on Linux works fine. * workflow: run that check plus a nixfmt check on every push and PR. * pre-commit: parse staged .nix files before handing them to nixfmt. nixfmt does reject unparseable input, but under `set -e` it aborts the hook with its own error rather than naming the offending file. This check reports the file and blocks the commit outright. * CLAUDE.md: document the check, and correct the flake input table -- catppuccin was listed but is not an input, while nixpkgs-unstable, pkgs-monorepo and tgirlpkgs were missing. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01CXcvSimqph8QSEZYX1gazi