hosts/Darwin/README.md

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+# macOS (nix-darwin) — `lyrathorpe-mac`
+
+Flake host: `lyrathorpe-mac` (`aarch64-darwin`). Apple Silicon Mac managed by
+**nix-darwin** from this same flake. Built via `mkDarwinHost` (single-user —
+macOS owns the account; identity still comes from the registry). Files:
+`configuration.nix`.
+
+## What this host is
+
+A macOS workstation. The interactive user environment (shell, git, editor,
+Claude) is the **shared `../../home` bundle** — the same modules the Linux hosts
+use — so the terminal experience matches. The Linux-only `desktop.nix`/`sway.nix`
+are intentionally left out. This host config covers the macOS-specific layer:
+system packages, Homebrew, and macOS UI defaults.
+
+## Package sourcing
+
+- **nixpkgs** (`environment.systemPackages`) for CLI tooling and libraries.
+- **Homebrew**, owned declaratively by `nix-homebrew` (Rosetta enabled for
+  x86_64 formulae). The `brews`/`casks` lists are **authoritative**:
+  `onActivation.cleanup = "zap"` uninstalls anything not declared. GUI apps are
+  casks (nixpkgs darwin GUI support is unreliable); a few version-pinned
+  toolchains and the PWA host stay on brew for continuity.
+- **Mac App Store** apps are **not** declarative: nix-darwin 26.05 runs
+  activation as root, and `mas` cannot reach the App Store session from root.
+  Install them by hand with `mas install <id>` from a GUI Terminal (the `mas`
+  CLI is in `environment.systemPackages`).
+
+## macOS integration
+
+- `security.pam.services.sudo_local` — **Touch ID for sudo** (and
+  `darwin-rebuild`'s sudo prompt), kept in `sudo_local` so it survives OS
+  updates. `reattach` pulls in `pam_reattach` so Touch ID works inside tmux
+  (which the terminals auto-start).
+- `system.defaults` — declarative dock / finder / global / trackpad preferences,
+  applied on activation and reversible. This is the main reason to run nix-darwin
+  beyond package management.
+- The JetBrainsMono Nerd Font is installed to `/Library/Fonts`; set it in
+  iTerm2 (Settings → Profiles → Text → Font) so the tmux statusline glyphs
+  render.
+
+## stateVersion
+
+`system.stateVersion = 5` (the nix-darwin state version, an integer — not a
+NixOS release string). Read `darwin-rebuild changelog` before changing it.
+
+## Apply
+
+```sh
+darwin-rebuild switch --flake .#lyrathorpe-mac
+```