feat(hosts): add the Raspberry Pi Zero 2 W Psion sidecar

A headless aarch64 companion for a Psion 5MX: PPP over RS232 with NAT out to
wifi and a telnet login, plus a cleartext POP3/SMTP proxy for the Psion's mail
client.

- hosts/PiZero2W/: host config, serial-ppp.nix, email-proxy.nix, an SD-image
  variant, and a hardware-configuration.nix placeholder.
- Host table entry on nixos-hardware's raspberry-pi-3 profile; the Zero 2 W is
  the Pi 3's BCM2837 SoC. nixpkgs' linuxPackages_rpi02w is deprecated and warns
  that the linux-rpi series is being removed in favour of nixos-hardware.
- The host owns its firmware partition (hardware.raspberry-pi.firmware), which
  is what puts the disable-bt and uart0/ctsrts overlays in config.txt so
  /dev/ttyAMA0 is the RS232 header rather than Bluetooth. uboot.enable keeps the
  U-Boot -> extlinux boot path the rewritten config.txt would otherwise lose.
- packages.aarch64-linux.zero2w-sd-image: the host's own configuration as an
  installable card. The board has no Ethernet and no free serial port, so a
  generic image would leave no way in.
- The mail proxy comes from the legacy-email-proxy flake, which provides the
  package and the NixOS module; nothing about it is vendored here.
- docs/hosts/pizero2w.md, plus README host table and shared-layer notes.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -42,6 +42,17 @@ prettier formats `*.md`, so **documentation edits must be run through `nix fmt`*
 exactly like code. prettier re-aligns Markdown tables in particular; hand-editing
 a table almost always leaves it non-conformant and fails the `formatting` check.
 
+Prose documentation lives in `docs/` and is **published** to
+<https://docs.lyrapup.pet/nixfiles/> by the separate `docs-site` repo, which
+clones this one at build time. Two consequences when editing docs:
+
+- A markdown file outside `docs/` (other than the root `README.md`) is not
+  synced and will never appear on the site. Put new prose in `docs/`.
+- Links must follow the rules in the README's "Documentation" section: absolute
+  Gitea URLs to source files, relative links between `docs/` pages, and
+  absolute `docs.lyrapup.pet` URLs from the root README into `docs/`. The site
+  builds non-strict, so a broken link is silent.
+
 The CI `formatting` step runs on **every** PR — including docs- and config-only
 changes — so a Markdown/YAML/JSON edit is format-checked before merge, not just
 after it lands on `main`. (The heavier `deadnix`/`statix`/`pre-commit` lints and

README.md

@@ -5,24 +5,25 @@ single flake.
 
 ## Hosts
 
-Defined in the host table in [`flake.nix`](./flake.nix):
+Defined in the host table in [`flake.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/flake.nix):
 
 | Configuration         | System           | Machine                                                                                                                                        |
-| --------------------- | ---------------- | ----------------------------------------------------------------------------------------------------------- |
+| --------------------- | ---------------- | ---------------------------------------------------------------------------------------------------------------------------------------------- |
 | `lyrathorpe-mbp`      | `aarch64-linux`  | MacBook Pro (Apple Silicon, Asahi)                                                                                                             |
-| `lyrathorpe-t400`     | `x86_64-linux`   | ThinkPad T400 — [install notes](./hosts/T400/README.md)                                                     |
+| `lyrathorpe-t400`     | `x86_64-linux`   | ThinkPad T400 — [install notes](https://docs.lyrapup.pet/nixfiles/hosts/t400/)                                                                 |
-| `lyrathorpe-macpro31` | `x86_64-linux`   | Mac Pro 3,1, desktop — [install notes](./hosts/MacPro31/README.md)                                          |
+| `lyrathorpe-macpro31` | `x86_64-linux`   | Mac Pro 3,1, desktop — [install notes](https://docs.lyrapup.pet/nixfiles/hosts/macpro31/)                                                      |
-| `emmathorpe-edaas`    | `x86_64-linux`   | Work WSL box (NixOS-WSL) — [notes](./hosts/EDaaS/README.md)                                                 |
+| `emmathorpe-edaas`    | `x86_64-linux`   | Work WSL box (NixOS-WSL) — [notes](https://docs.lyrapup.pet/nixfiles/hosts/edaas/)                                                             |
-| `lyrathorpe-rpi5`     | `aarch64-linux`  | Raspberry Pi 5 headless server: Docker host + nginx reverse proxy — [install notes](./hosts/RPi5/README.md) |
+| `lyrathorpe-rpi5`     | `aarch64-linux`  | Raspberry Pi 5 headless server: Docker host + nginx reverse proxy — [install notes](https://docs.lyrapup.pet/nixfiles/hosts/rpi5/)             |
-| `lyrathorpe-mac`      | `aarch64-darwin` | macOS (nix-darwin) — [notes](./hosts/Darwin/README.md)                                                      |
+| `lyrathorpe-zero2w`   | `aarch64-linux`  | Raspberry Pi Zero 2 W "Psion sidecar": PPP over RS232 + legacy mail proxy — [install notes](https://docs.lyrapup.pet/nixfiles/hosts/pizero2w/) |
+| `lyrathorpe-mac`      | `aarch64-darwin` | macOS (nix-darwin) — [notes](https://docs.lyrapup.pet/nixfiles/hosts/darwin/)                                                                  |
 
 Shared layers: `home` (home-manager: shell, git, editor),
 `modules/common-nixos.nix` (all NixOS hosts: fonts, nix-ld, caches),
 `modules/workstation.nix` (physical graphical hosts: audio, thermald,
 earlyoom, fwupd), `modules/laptop.nix` (laptops: Wi-Fi, Bluetooth, power,
 lid), `modules/desktop.nix` (wired desktops: NetworkManager), and
-`modules/ssh.nix` (key-only sshd). The x86 hosts also pull `nixos-hardware`
+`modules/ssh.nix` (key-only sshd). The x86 hosts and both Raspberry Pis also
-profiles. The full module catalogue is below.
+pull `nixos-hardware` profiles. The full module catalogue is below.
 
 ## Repository layout
 
@@ -31,6 +32,7 @@ flake.nix              # inputs, mkHost/mkDarwinHost, the host tables, dev shell
 flake.lock             # pinned input revisions (Renovate keeps this fresh)
 modules/               # reusable NixOS system modules (see "Module catalogue")
 home/                  # home-manager profile: shell, git, editor, claude, secret-service, desktop, sway
+docs/                  # all prose documentation; published to docs.lyrapup.pet (see "Documentation")
 users/                 # identity registry + per-user home extras (see "Users")
 hosts/<Name>/          # per-machine config: configuration.nix + hardware-configuration.nix
 lib/                   # small pure helpers (currently the Catppuccin Mocha palette)
@@ -50,21 +52,21 @@ host's table entry.
 
 ## Module catalogue
 
-Reusable NixOS modules under [`modules/`](./modules). "Imported by" says how a
+Reusable NixOS modules under [`modules/`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/modules). "Imported by" says how a
 module reaches a host: **baseModules** (every NixOS host, via `flake.nix`),
 **host table** (listed explicitly per host in `flake.nix`), or **transitively**
 (pulled in by another module's `imports`).
 
 | Module             | Imported by                          | What it does / when to use it                                                                                                                                                                                                                                                                                                 |
-| ------------------ | --------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| ------------------ | ------------------------------------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
-| `common-nixos.nix` | baseModules (all NixOS)           | Timezone/locale, store hygiene (auto-optimise, big download buffer, **no** auto-GC), the nix-community binary cache, `nix-ld`, base CLI (`git`, `fastfetch`), and the fleet-wide font stack.              |
+| `common-nixos.nix` | baseModules (all NixOS)              | Timezone/locale, store hygiene (auto-optimise, big download buffer, **no** auto-GC), the nix-community binary cache, `nix-ld`, **sudo-rs** in place of sudo, base CLI (`git`, `fastfetch`), and the fleet-wide font stack.                                                                                                    |
 | `users.nix`        | baseModules (all NixOS)              | Builds `users.users` from the registry for the host's `hostUsers`; enables zsh; enables Firefox + Thunderbird **only** when `features.swayDesktop.enable` is on. Applies per-user `linger`.                                                                                                                                   |
-| `features.nix`     | baseModules (all NixOS)           | Declares feature-flag options (currently `features.swayDesktop.enable`) so any host can read/set them without importing the heavy implementation module.                                                  |
+| `features.nix`     | baseModules (all NixOS)              | Declares the feature-flag options (`features.swayDesktop.enable`, `features.claudeCode.enable`) so any host can read/set them without importing the heavy implementation module, plus the CPU capability fact they derive from (`features.cpu.microarchLevel`) and the assertion that guards it. See "CPU capability gating". |
 | `workstation.nix`  | transitively (via laptop/desktop)    | Form-factor-agnostic base for physical graphical hosts: turns on `swayDesktop`, Dvorak console, PipeWire, firewall (default-deny), fstrim, earlyoom, fwupd, thermald (x86), redistributable fw.                                                                                                                               |
 | `laptop.nix`       | host table (MBP, T400)               | `imports` workstation.nix, then adds the portable bits: iwd Wi-Fi, lid suspend/lock, Bluetooth + blueman.                                                                                                                                                                                                                     |
 | `desktop.nix`      | host table (Mac Pro)                 | `imports` workstation.nix, then swaps Wi-Fi for wired NetworkManager. Pair with `portable = false` in the host table.                                                                                                                                                                                                         |
 | `sway.nix`         | host table (graphical hosts)         | Implementation of `features.swayDesktop`: the system Sway package, the greetd/ReGreet (cage) greeter forced to Dvorak, xdg-portal, Wayland utility packages. Home-side Sway config is in `home/sway.nix`.                                                                                                                     |
-| `ssh.nix`          | host table (T400, Mac Pro, RPi5)  | Enables sshd, opens port 22, enforces a key-only policy (no password / keyboard-interactive, no root). Authorized keys come from the registry via `users.nix`.                                            |
+| `ssh.nix`          | host table (T400, Mac Pro, both Pis) | Enables sshd, opens port 22, enforces a key-only policy (no password / keyboard-interactive, no root). Authorized keys come from the registry via `users.nix`.                                                                                                                                                                |
 | `firmware/`        | referenced by MBP host config        | Committed Apple peripheral firmware blobs for the Asahi MBP (see "MacBook (Asahi) firmware").                                                                                                                                                                                                                                 |
 
 Form-factor decision: a **laptop** imports `laptop.nix` (default
@@ -74,16 +76,39 @@ Form-factor decision: a **laptop** imports `laptop.nix` (default
 serves. `portable` is threaded through to `home/sway.nix`, which drops the
 battery block and brightness keys on desktops.
 
+## CPU capability gating
+
+Not every host can run everything the fleet installs. Nix cannot probe the CPU
+(evaluation is pure, and a host may be built elsewhere), so each machine
+declares what it is and the shared modules derive from that:
+
+- `features.cpu.microarchLevel` — the x86-64 psABI level the CPU implements
+  (1 = baseline, 2 = SSE4.2/POPCNT, 3 = AVX2, 4 = AVX-512). Defaults to **2**;
+  only a host older than that sets it (the Mac Pro 3,1's 2008 Harpertown Xeons
+  are level 1). Ignored on non-x86_64 hosts.
+- `features.claudeCode.enable` — derived: on unless the host is below
+  x86-64-v2, because Claude Code's Node runtime needs SSE4.2/POPCNT.
+  [`home/claude.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/home/claude.nix) reads it through home-manager's
+  `osConfig` and installs nothing (CLI, `CLAUDE.md`, output style, memory
+  symlink) when it is off. Hosts with no such option — the Darwin host and the
+  standalone `homeConfigurations` — fall back to enabled.
+- An assertion in `features.nix` fails evaluation if a host force-enables a
+  flag its declared CPU level cannot support, so the mistake surfaces in
+  `nix flake check`/CI rather than as an illegal-instruction crash on the box.
+
+Adding another CPU-sensitive tool means deriving one more flag there, not
+editing every host.
+
 ## Users
 
 Identity is data, kept separate from the reusable modules:
 
-- [`users/registry.nix`](./users/registry.nix) — one entry per user (display
+- [`users/registry.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/users/registry.nix) — one entry per user (display
   name, email, supplementary groups, authorized + signing keys). This is the
   single source of identity; no user data is hardcoded in the modules.
 - Each host's table entry declares a `users` set keyed by username; every entry
   lists that user's home-module composition (the shared `./home` bundle plus any
-  per-user modules, e.g. [`users/emmathorpe/work.nix`](./users/emmathorpe/work.nix))
+  per-user modules, e.g. [`users/emmathorpe/work.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/users/emmathorpe/work.nix))
   and optional per-host-user system bits such as `linger`.
 - `mkHost` builds each account from the registry and injects the matching
   identity into that user's home config as the `identity` module arg. A host can
@@ -91,13 +116,13 @@ Identity is data, kept separate from the reusable modules:
 
 Per-user home extras live under `users/<name>/`:
 
-- [`users/lyrathorpe/home.nix`](./users/lyrathorpe/home.nix) — personal extras
+- [`users/lyrathorpe/home.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/users/lyrathorpe/home.nix) — personal extras
   (an ssh host shortcut, gammastep coordinates); imported on Lyra's hosts.
-- [`users/emmathorpe/work.nix`](./users/emmathorpe/work.nix) — the work
+- [`users/emmathorpe/work.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/users/emmathorpe/work.nix) — the work
   toolchain (kubectl/helm/az/etc.), work-only LSP servers, the corporate ssh
   handling, and the headless Secret Service that gcx needs for its keychain
-  tokens (see [`home/secret-service.nix`](./home/secret-service.nix)); imports
+  tokens (see [`home/secret-service.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/home/secret-service.nix)); imports
-  [`users/emmathorpe/renovate-review.nix`](./users/emmathorpe/renovate-review.nix),
+  [`users/emmathorpe/renovate-review.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/users/emmathorpe/renovate-review.nix),
   the daily headless Renovate-PR review timer (EDaaS only).
 
 ### Portable home (off-NixOS / external consumers)
@@ -156,17 +181,20 @@ automatically.
 ## Shell environment & keybindings
 
 - Interactive shell features (zsh, tmux, git, ssh, CLI tools, auto-tmux):
-  [`home/README.md`](./home/README.md).
+  [`docs/shell.md`](https://docs.lyrapup.pet/nixfiles/shell/).
+- Which classic utilities are shadowed by modern replacements, and the flag
+  differences that will bite:
+  [`docs/shell.md` → "Replacing the classics"](https://docs.lyrapup.pet/nixfiles/shell/#replacing-the-classics).
 - All Sway / tmux / foot / zsh keyboard shortcuts:
-  [`home/KEYBINDINGS.md`](./home/KEYBINDINGS.md).
+  [`docs/keybindings.md`](https://docs.lyrapup.pet/nixfiles/keybindings/).
 
 ## Login / greeter
 
 Graphical (Sway) hosts log in through a Wayland greeter — `greetd` running
 ReGreet inside the `cage` kiosk compositor — implemented in
-[`modules/sway.nix`](./modules/sway.nix), gated on
+[`modules/sway.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/modules/sway.nix), gated on
 `features.swayDesktop.enable` (the option is declared in
-[`modules/features.nix`](./modules/features.nix), so headless hosts
+[`modules/features.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/modules/features.nix), so headless hosts
 can leave it off without importing `modules/sway.nix`). The greeter is forced to Dvorak
 to match the console and Sway session. Headless hosts (the WSL work box and the
 Raspberry Pi server) keep plain TTY login. The target account needs a password
@@ -186,6 +214,38 @@ To refresh them, copy the firmware extracted during the Asahi install (from
 [Asahi NixOS docs](https://github.com/tpwrules/nixos-apple-silicon)) into
 `modules/firmware/` and commit with `git add -f`.
 
+## Documentation
+
+All prose documentation lives in [`docs/`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/docs); this README is the overview. The pages are
+published to **<https://docs.lyrapup.pet/nixfiles/>** by the
+[`docs-site`](https://code.emmathe.dev/lyrathorpe/docs-site) repository, which clones this repo on
+every build (on its own push, nightly, or on demand) and assembles the tree:
+
+```
+README.md   ->  docs/nixfiles/index.md     # this file becomes the section landing page
+docs/       ->  docs/nixfiles/             # everything here, ordering from docs/.pages
+```
+
+Nothing is pushed from this side and there is no build step here — editing a
+page and merging is all that is required. Files outside `docs/` (bar this
+README) are **not** synced, so a doc kept next to the code it describes will
+never appear on the site.
+
+### Linking rules
+
+The site has no copy of the source tree, and this README is republished at a
+different depth from the rest of `docs/`. Both facts break naive relative
+links, so:
+
+| Link from         | To                      | Use                                                              |
+| ----------------- | ----------------------- | ---------------------------------------------------------------- |
+| anywhere          | a source file or dir    | absolute `https://code.emmathe.dev/.../src/branch/main/…`        |
+| a page in `docs/` | another page in `docs/` | relative (`./keybindings.md`) — correct in Gitea and on the site |
+| this README       | a page in `docs/`       | absolute `https://docs.lyrapup.pet/nixfiles/…`                   |
+
+`mkdocs build` runs non-strict on the docs-site side, so a broken link fails
+silently rather than failing the build. Check links by hand when moving a page.
+
 ## Development
 
 A dev shell and a formatting/lint gate are wired through the flake:
@@ -201,7 +261,7 @@ A dev shell and a formatting/lint gate are wired through the flake:
 
 ## CI
 
-[`.gitea/workflows/ci.yaml`](./.gitea/workflows/ci.yaml) runs `nix flake check`
+[`.gitea/workflows/ci.yaml`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/.gitea/workflows/ci.yaml) runs `nix flake check`
 (formatting, `deadnix`, `statix`, the pre-commit hooks) and evaluates every
 NixOS and Darwin host configuration on push/PR. It always runs (no `paths:`
 filter) so the required check never hangs pending; the heavy Nix steps are

docs/.pages

@@ -0,0 +1,16 @@
+# Section title and ordering for the MkDocs awesome-pages plugin on
+# docs.lyrapup.pet.
+#
+# The title is set explicitly: with no entry in the site's nav, MkDocs derives
+# the section name from the directory and renders it title-cased as "Nixfiles".
+title: nixfiles
+
+# `index.md` is this repository's root README, copied in by the docs-site build
+# before this directory is synced over the top. The trailing `...` picks up any
+# page added later, so a new file needs no edit here.
+nav:
+  - index.md
+  - shell.md
+  - keybindings.md
+  - hosts
+  - ...

docs/hosts/.pages

@@ -0,0 +1 @@
+title: Hosts

docs/hosts/edaas.md

@@ -11,7 +11,7 @@ The day-to-day work environment. It layers the corporate Kubernetes / Helm /
 Terraform / cloud toolchain and a couple of work-only editor language servers on
 top of the shared home profile. The system config here is thin — it is mostly
 WSL plumbing; the user-facing tooling lives in
-[`../../users/emmathorpe/work.nix`](../../users/emmathorpe/work.nix).
+[`../../users/emmathorpe/work.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/users/emmathorpe/work.nix).
 
 ## WSL specifics
 
@@ -34,7 +34,7 @@ WSL plumbing; the user-facing tooling lives in
 The host-table entry sets `users.emmathorpe.linger = true` so the user's
 `systemd --user` instance stays alive without an open login session. That keeps
 the daily headless **Renovate PR review** timer firing — defined in
-[`../../users/emmathorpe/renovate-review.nix`](../../users/emmathorpe/renovate-review.nix)
+[`../../users/emmathorpe/renovate-review.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/users/emmathorpe/renovate-review.nix)
 (imported only from `work.nix`, so it exists on this machine alone). See that
 file's header for the auth (Vertex AI ADC), triage policy, and caveats.
 
@@ -53,7 +53,7 @@ name is not activatable".
 Home-manager's own `services.gnome-keyring` does not work here: it is
 `WantedBy=graphical-session-pre.target`, which never activates on this headless
 box, and it cannot unlock the keyring. See
-[`../../home/secret-service.nix`](../../home/secret-service.nix) for the full
+[`../../home/secret-service.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/home/secret-service.nix) for the full
 rationale and the security trade-off of an auto-unlocked keyring.
 
 Only the `secrets` component is started. The `ssh` component is deliberately off

docs/hosts/macpro31.md

@@ -0,0 +1,138 @@
+# Mac Pro 3,1 (Early 2008) — install notes
+
+Flake host: `lyrathorpe-macpro31`. Desktop (`portable = false`, imports
+`../../modules/desktop.nix`). Files: `configuration.nix`, `nvidia.nix`,
+`hardware-configuration.nix`.
+
+## Hardware configuration
+
+`hardware-configuration.nix` here is the real config generated by
+`nixos-generate-config` on the machine. Root is an **LVM** logical volume
+(`/dev/mapper/MacPro-Root`, ext4); the ESP (vfat) and swap are referenced by
+UUID. The initrd carries `dm-snapshot` for the LVM root. Regenerate and commit
+if the disk layout changes.
+
+## Bootloader
+
+The Mac Pro 3,1 has **64-bit EFI**, so it uses **systemd-boot** (no GRUB/CSM
+shim). `canTouchEfiVariables = false` because Apple's firmware does not reliably
+accept `efibootmgr` NVRAM writes.
+
+Apple-EFI quirk: if the firmware boot picker does not show NixOS after install,
+either
+
+- uncomment `boot.loader.efi.efiInstallAsRemovable = true;` in
+  `configuration.nix` (installs the fallback `\EFI\BOOT\BOOTX64.EFI`), and/or
+- "bless" the ESP from macOS.
+
+Partition the disk GPT with an ESP (vfat).
+
+## Graphics — NVIDIA Quadro P400
+
+The stock card (**ATI Radeon HD 2600 XT** or **NVIDIA GeForce 8800 GT**,
+depending on the unit) has been replaced with an **NVIDIA Quadro P400** (Pascal,
+GP108). Everything driver-related lives in [`nvidia.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/hosts/MacPro31/nvidia.nix):
+
+- **Driver branch 580** (`nvidiaPackages.legacy_580`), _not_ the nixpkgs default
+  (`production`, currently 595.x). 580 is the last branch that supports
+  Maxwell/Pascal/Volta and is maintained as an LTS branch until Aug 2028; a
+  newer branch does not drive this card at all.
+- `modesetting.enable = true` — mandatory for Wayland (sets
+  `nvidia-drm.modeset=1`); without it wlroots gets no GBM device and both Sway
+  and the greeter fail to start.
+- `open = false` — the open kernel modules require Turing or later.
+- Sway runs with `--unsupported-gpu` (`programs.sway.extraOptions`); wlroots
+  refuses the proprietary driver otherwise. `cage`/ReGreet needs no such flag.
+- nouveau and `nvidiafb` are blacklisted automatically by the NVIDIA module.
+
+The driver is unfree, so it is **not in the binary cache**: the kernel module is
+compiled on the machine, which on these 2008 Xeons is slow — budget for a long
+first rebuild and again after every kernel bump. The package names are
+allowlisted in `unfreePackages` in [`flake.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/flake.nix).
+
+Note the Mac Pro shows no EFI boot screen with a stock PC card (no Apple EFI
+ROM): the machine boots blind until KMS brings the display up. That is expected,
+not a fault.
+
+Verify after a rebuild:
+
+```sh
+nvidia-smi
+```
+
+## Docker with CUDA
+
+`nvidia.nix` also enables Docker and gives containers GPU access via **CDI**
+(`hardware.nvidia-container-toolkit.enable`), which generates device specs from
+the host driver at boot (regenerated by a udev rule when the `nvidia` device
+appears) and turns on the daemon's CDI feature:
+
+```sh
+docker run --rm --device=nvidia.com/gpu=all nvidia/cuda:12.9.1-base-ubuntu24.04 nvidia-smi
+```
+
+- Use the `--device=nvidia.com/gpu=all` form. `--gpus all` is the legacy
+  runtime-wrapper path (`virtualisation.docker.enableNvidia`), which is
+  deprecated upstream and deliberately not enabled here.
+- **CUDA version matters.** The P400 is compute capability 6.1 (`sm_61`); CUDA
+  13 dropped Maxwell/Pascal/Volta, so container images must ship a **CUDA 12.x
+  or older** runtime. The 580 driver itself is happy with either.
+- 2 GB of VRAM, 256 CUDA cores — fine for encode/decode and small models, not
+  for training anything serious.
+- Docker socket is local-only (no TCP listener, unlike the Pi). Users need the
+  `docker` group; the registry already grants it.
+
+### "Driver Not Loaded" from the CDI generator
+
+`nvidia-container-toolkit-cdi-generator.service` fails with
+`failed to initialize NVML: Driver Not Loaded` whenever the `nvidia` kernel
+module is not loaded in the **running** kernel. After a kernel bump that is
+unavoidable — the rebuilt module cannot load until reboot — so the unit is
+guarded with `ConditionPathExists=/proc/driver/nvidia/version` and skips
+instead of failing. Without that guard it also takes `docker.service`
+(`requiredBy`) with it and makes `nixos-rebuild switch` exit non-zero.
+
+**Reboot after a rebuild that touches the driver or the kernel.** The toolkit's
+udev rule restarts the generator when the GPU device appears, so the CDI specs
+are written on the next boot. To check the state:
+
+```sh
+lsmod | grep nvidia            # nvidia, nvidia_modeset, nvidia_drm, nvidia_uvm
+cat /proc/driver/nvidia/version
+nvidia-smi
+systemctl status nvidia-container-toolkit-cdi-generator.service
+ls /var/run/cdi                # the generated spec
+```
+
+If the module is genuinely absent after a reboot, check `dmesg | grep -i
+nvidia` (build/version mismatch, or nouveau still bound — the module blacklists
+it, so that should not happen).
+
+## Claude Code — not installed here
+
+The dual Harpertown Xeons are **x86-64-v1** (SSE4.1, but no SSE4.2/POPCNT) and
+the Node runtime Claude Code ships on requires x86-64-v2. `configuration.nix`
+declares `features.cpu.microarchLevel = 1`, which switches the tool off through
+the fleet-wide gate in [`../../modules/features.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/modules/features.nix)
+— see the root README. Forcing `features.claudeCode.enable` on here is an
+evaluation error, not a broken install.
+
+## Networking
+
+Wired Ethernet via NetworkManager (from `desktop.nix`) — the Mac Pro has two
+gigabit ports.
+
+## Login
+
+Graphical login via a Wayland greeter — `greetd` running ReGreet inside the
+`cage` kiosk compositor — configured centrally in `../../modules/sway.nix` for
+every Sway host (gated on `features.swayDesktop.enable`). The greeter is forced
+to the Dvorak layout to match the console and Sway session. Set the user
+password (`passwd lyrathorpe`) after install, or the greeter cannot
+authenticate. Requires working KMS (NVIDIA modesetting — see Graphics).
+
+## Apply
+
+```sh
+sudo nixos-rebuild switch --flake .#lyrathorpe-macpro31
+```

docs/hosts/pizero2w.md

@@ -0,0 +1,205 @@
+# Raspberry Pi Zero 2 W (`lyrathorpe-zero2w`)
+
+Headless `aarch64-linux` "Psion sidecar": an RS232 companion for a Psion 5MX,
+after [Kian Ryan's PPP modem and terminal
+write-up](https://www.kianryan.co.uk/2022-11-28-psion-sidecar-ppp-modem-and-terminal/).
+Two roles, split into submodules:
+
+- **PPP link + telnet** (`serial-ppp.nix`) — `pppd` on `/dev/ttyAMA0`, the Psion
+  on the far end of a null-modem cable, NAT out to Wi-Fi, and a telnet login for
+  the Psion's terminal client.
+- **Legacy mail proxy** (`email-proxy.nix`) — cleartext POP3/SMTP for the
+  Psion's built-in mail client, forwarded to authenticated IMAPS/SMTPS by
+  [legacy-email-proxy](https://code.emmathe.dev/lyrathorpe/legacy-email-proxy).
+  That project ships its own package and NixOS module, so `email-proxy.nix`
+  here is only `services.legacy-email-proxy.enable` plus a path to the
+  credentials — nothing about the proxy is vendored into this flake.
+
+`sd-image.nix` in the same directory is not part of the running system: it is
+the one-shot install card, built as `packages.aarch64-linux.zero2w-sd-image`.
+See "Install".
+
+## Hardware and boot
+
+The Zero 2 W is a BCM2837 — the Pi 3's SoC — so the host table uses
+`nixos-hardware`'s `raspberry-pi-3` profile for the kernel, firmware and device
+tree. Boot is the same U-Boot + extlinux path as the other Pi.
+
+Unlike the Pi 5, this host owns the firmware partition declaratively
+(`hardware.raspberry-pi.firmware.enable`): every `switch` rewrites
+`/boot/firmware`, including `config.txt`. Two settings there matter:
+
+| `config.txt`             | Why                                                                                                                                                 |
+| ------------------------ | --------------------------------------------------------------------------------------------------------------------------------------------------- |
+| `dtoverlay=disable-bt`   | Moves the PL011 UART off Bluetooth onto GPIO 14/15, so `/dev/ttyAMA0` is the RS232 header. The mini UART (`ttyS0`) drifts at 115200.                |
+| `dtoverlay=uart0,ctsrts` | RTS/CTS on GPIO 16/17. Both `pppd` and the Psion's modem profile use hardware flow control.                                                         |
+| `kernel=u-boot.bin`      | `hardware.raspberry-pi.firmware.uboot.enable`. Without it the rewritten `config.txt` would have no `kernel=` line and the board would stop booting. |
+
+`gpu_mem=16`, `start_x=0`, `camera_auto_detect=0` and `display_auto_detect=0`
+hand the VideoCore the minimum: the board has 512 MB total and no display.
+
+## Never build on the Pi
+
+512 MB of RAM and an SD card. It cannot compile its own system, and there is
+deliberately no swap partition (SD cards wear out under swap writes) — zram
+takes its place. Build somewhere else and push the result:
+
+```sh
+# from a workstation, using another aarch64 machine as the builder
+nixos-rebuild switch --flake .#lyrathorpe-zero2w \
+  --build-host lyrathorpe@lyrathorpe-rpi5 \
+  --target-host lyrathorpe@<pi-address> --use-remote-sudo
+```
+
+The `raspberry-pi-3` profile builds the vendor kernel from source and it is not
+in the binary cache, so the first build is long (hours on the Pi 5, less on the
+MacBook). Later builds reuse it. The same applies to the SD image below: it
+contains that kernel, so it needs an `aarch64-linux` builder too. From an
+`x86_64` box or a Mac, that means a remote builder (`nix.buildMachines`) or, on
+Darwin, `nix.linux-builder.enable`.
+
+## Install
+
+The card is built from this flake, not downloaded. A generic NixOS image would
+boot, but there would be no way into the machine afterwards: it has no Ethernet,
+no wifi credentials, and this configuration hands the serial port to `pppd`, so
+there is no console either. Building the host's own image sidesteps all three —
+the first boot is already the real system, with the SSH key from the registry
+in place.
+
+1. **Set the SSID.** `networking.wireless.networks` in `configuration.nix` still
+   says `CHANGE-ME-SSID`. It is baked into the image at build time; only the PSK
+   is read at runtime.
+2. **Build and write the card.** On an `aarch64-linux` machine (or with one
+   configured as a builder):
+   ```sh
+   nix build .#packages.aarch64-linux.zero2w-sd-image
+   sudo dd if=result/sd-image/nixos-zero2w.img of=/dev/sdX bs=4M conv=fsync status=progress
+   ```
+   Check `/dev/sdX` twice. `dd` does not ask.
+3. **Seed the secrets before first boot.** They are not in the image. Mount the
+   card's second partition (the ext4 root) and write both files described under
+   "Secrets" below:
+   ```sh
+   sudo mount /dev/sdX2 /mnt
+   sudo mkdir -p /mnt/var/lib/wpa_supplicant /mnt/var/lib/legacy-email-proxy
+   printf 'psk_home=%s\n' 'the-pre-shared-key' \
+     | sudo tee /mnt/var/lib/wpa_supplicant/secrets.conf > /dev/null
+   sudo chmod 600 /mnt/var/lib/wpa_supplicant/secrets.conf
+   # ... and /mnt/var/lib/legacy-email-proxy/backend.env, same permissions
+   sudo umount /mnt
+   ```
+   Skip the PSK and the board boots with no network at all.
+4. **Boot it.** Give it a few minutes on first boot — it resizes the root
+   partition and generates host keys on a slow card. Then:
+   ```sh
+   ssh lyrathorpe@lyrathorpe-zero2w.local   # mDNS; services.avahi publishes it
+   ```
+5. **Give the login user a password** (`passwd lyrathorpe`) if you want console
+   or telnet login; the SSH key from
+   [`users/registry.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/users/registry.nix)
+   already works without one.
+6. Thereafter, rebuild from another machine as in the previous section.
+
+`hosts/PiZero2W/hardware-configuration.nix` is a **placeholder** — but its
+layout (`/` on label `NIXOS_SD`, `/boot/firmware` on label `FIRMWARE`) is
+exactly what the SD image produces, so there is nothing to regenerate for a card
+install. Run `nixos-generate-config` and replace it only if you deviate from
+that layout.
+
+If the board never appears on the network, it is almost always the PSK file.
+Re-mount the card and check it. Failing that, a mini-HDMI monitor and a
+micro-USB keyboard get you a console on `tty1` — the serial port will not,
+because `pppd` holds it.
+
+## Secrets (not in the Nix store)
+
+Both files are created on the device, owned by root, mode `0600`. Neither is
+managed by this flake; the units that read them fail loudly if they are absent.
+
+**Wi-Fi PSK** — `/var/lib/wpa_supplicant/secrets.conf`:
+
+```
+psk_home=<the pre-shared key>
+```
+
+The SSID itself _is_ in `configuration.nix` and is currently the placeholder
+`CHANGE-ME-SSID`; set it to the real network. `wpa_supplicant` resolves
+`pskRaw = "ext:psk_home"` against this file at runtime.
+
+**Mail backend** — `/var/lib/legacy-email-proxy/backend.env`, a systemd
+`EnvironmentFile`:
+
+```
+BACKEND_IMAP_HOST=imap.example.com
+BACKEND_IMAP_USER=someone@example.com
+BACKEND_IMAP_PASS=<app password>
+BACKEND_SMTP_HOST=smtp.example.com
+BACKEND_SMTP_USER=someone@example.com
+BACKEND_SMTP_PASS=<app password>
+```
+
+Ports and TLS default sensibly (IMAPS 993, SMTPS 465); the full variable list is
+in the proxy's README.
+
+### Why POP3 and not IMAP
+
+The Psion's built-in mail client speaks POP only, so POP3 is what the proxy
+exposes. If a third-party IMAP client is ever installed on the device, the
+answer is **not** to add an IMAP frontend to the proxy: the backend is already
+IMAP, so there is no protocol to translate, only TLS to remove. An `stunnel`
+client (plaintext 143 on the PPP link, IMAPS 993 outbound) does that in a few
+lines with no code, and credentials pass straight through — IMAP clients always
+authenticate.
+
+SMTP stays on the proxy either way. A client of this vintage cannot do SMTP
+AUTH, which is exactly why the proxy injects the backend credentials.
+
+## Psion configuration
+
+Matches the addressing in `serial-ppp.nix` (`10.0.0.1` the Pi, `10.0.0.2` the
+Psion):
+
+- **Modem** control panel, a "Direct Cable Connection" profile: 115200 baud,
+  Hardware (RTS/CTS) flow control; on the Advanced tab, Terminal Detect and
+  Carrier Detect both **off**.
+- **Internet** control panel, a new profile: Connection Type **Direct**, Manual
+  Login **True**. Addresses: get IP from server **False**, static **10.0.0.2**.
+  Get DNS from server **True** — `pppd` sends resolvers over the link
+  (`ms-dns`), so nothing is hard-coded on the Psion.
+- Advanced: PPP extensions **False**, plain-text authentication **True**.
+- Terminal client: telnet to **10.0.0.1 port 23**. It renders non-ANSI output
+  far better than the raw serial console does.
+- Mail client: POP3 and SMTP server **10.0.0.1**, no encryption, no
+  authentication.
+
+## Security
+
+Everything on this host that the Psion talks to is unauthenticated and
+unencrypted, because a 1999 palmtop speaks no TLS:
+
+- **telnet on 23** — cleartext login, including the password.
+- **POP3 on 110 / SMTP on 25** — full mailbox access and an open relay to anyone
+  who reaches them.
+
+The confinement is the firewall, and it is the only thing standing there:
+`ppp0` is a trusted interface, `wlan0` is not, and those ports are never opened
+on it. The proxy binds `0.0.0.0` rather than `10.0.0.1` on purpose — the PPP
+address only exists while the Psion is plugged in, and a bind-time dependency on
+a serial cable is a restart loop waiting to happen. Do not add these ports to
+`networking.firewall.allowedTCPPorts`, and do not put this board on an untrusted
+network.
+
+Only sshd (port 22, key-only, via
+[`modules/ssh.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/modules/ssh.nix))
+is reachable over Wi-Fi.
+
+## Troubleshooting
+
+| Symptom                                         | Check                                                                                                                                                                            |
+| ----------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| No PPP at all                                   | `systemctl status pppd-psion`, then `journalctl -u pppd-psion -f` while the Psion dials. `passive`/`persist` mean it waits, not fails.                                           |
+| PPP negotiates, then hangs                      | Flow control. Confirm `dtoverlay=uart0,ctsrts` is in `/boot/firmware/config.txt` and that the Psion's modem profile is set to Hardware.                                          |
+| `/dev/ttyAMA0` missing or is a Bluetooth device | `disable-bt` did not apply — the firmware partition was not rewritten. Confirm `/boot/firmware` is a mounted partition; the activation script skips with a warning if it is not. |
+| Something else holds the port                   | `systemctl status serial-getty@ttyAMA0` — it is disabled in `serial-ppp.nix`, and must stay that way.                                                                            |
+| Mail proxy dead                                 | `systemctl status legacy-email-proxy`. A missing `backend.env` fails the unit before it starts.                                                                                  |

docs/keybindings.md

@@ -5,11 +5,11 @@ Everything here is managed declaratively through Nix — edit the listed file an
 rebuild, never the generated dotfiles.
 
 | Area              | Defined in                                                                                                                                                                            |
-| ----------------- | --------------------------------------------------------------------------------------------------------------------- |
+| ----------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
-| Sway (compositor) | [`sway.nix`](./sway.nix) `config.keybindings` + `config.modes`, plus the home-manager Sway module's built-in defaults |
+| Sway (compositor) | [`sway.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/home/sway.nix) `config.keybindings` + `config.modes`, plus the home-manager Sway module's built-in defaults |
-| tmux              | [`shell.nix`](./shell.nix) `programs.tmux`                                                                            |
+| tmux              | [`shell.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/home/shell.nix) `programs.tmux`                                                                            |
-| zsh line editor   | [`shell.nix`](./shell.nix) `programs.zsh.historySubstringSearch`                                                      |
+| zsh line editor   | [`shell.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/home/shell.nix) `programs.zsh.historySubstringSearch`                                                      |
-| Neovim            | [`editor.nix`](./editor.nix) `programs.nixvim`                                                                        |
+| Neovim            | [`editor.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/home/editor.nix) `programs.nixvim`                                                                        |
 | foot (terminal)   | foot package defaults — only colours are themed (in `sway.nix`)                                                                                                                       |
 
 **Conventions**

docs/shell.md

@@ -0,0 +1,360 @@
+# Interactive shell environment
+
+Everything the shell, terminal multiplexer, git and ssh do beyond their defaults,
+and where each is defined. All of it is managed declaratively through
+home-manager — edit the listed file and rebuild, never the generated dotfiles.
+
+Keyboard shortcuts have their own reference: [`keybindings.md`](./keybindings.md).
+
+| Area                                   | Defined in                                                                                                            |
+| -------------------------------------- | --------------------------------------------------------------------------------------------------------------------- |
+| zsh, CLI tools, tmux, ssh, auto-tmux   | [`shell.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/home/shell.nix)                            |
+| git (+ delta, commitizen)              | [`git.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/home/git.nix)                                |
+| Neovim (nixvim) + LSP                  | [`editor.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/home/editor.nix)                          |
+| Claude Code (CLAUDE.md, style, memory) | [`claude.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/home/claude.nix)                          |
+| GUI apps, GTK/Firefox theming, cursor  | [`desktop.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/home/desktop.nix) (graphical hosts only) |
+
+Shared by every host via [`default.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/home/default.nix); the work box also layers
+[`work.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/users/emmathorpe/work.nix) on top (its own ssh config, extra
+packages, kubecolor, and the C#/Helm language servers). The committer identity (name, email,
+signing key) comes from the user registry
+([`../users/registry.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/users/registry.nix)), not this module.
+
+---
+
+## zsh
+
+| Feature                  | Notes                                                                                                                                          |
+| ------------------------ | ---------------------------------------------------------------------------------------------------------------------------------------------- |
+| oh-my-zsh                | plugins `git`, `man`, `sudo` (Esc-Esc to prepend sudo), `colored-man-pages`, `extract`; theme `robbyrussell`                                   |
+| Autosuggestion           | fish-style history suggestions as you type (→ to accept)                                                                                       |
+| Syntax highlighting      | commands coloured by validity as you type                                                                                                      |
+| Completion               | menu completion; the dump is rebuilt on every activation (see Maintenance)                                                                     |
+| History                  | 100k in-memory/on-disk, deduped, space-prefixed commands ignored, timestamped, **shared live across sessions**; file stays at `~/.zsh_history` |
+| Dotfiles location        | `dotDir` is `~/.config/zsh` (XDG) — `.zshrc`/`.zshenv`/`.zcompdump` live there; `~/.zshenv` only bootstraps `$ZDOTDIR`                         |
+| History substring search | type a fragment, then ↑/↓ cycles matching past commands — works in foot, iTerm2 and the Linux TTY (both CSI and SS3 arrow encodings bound)     |
+| Prompt                   | hostname is prefixed when over SSH                                                                                                             |
+
+**Aliases:** `ls`/`ll`/`la`/`lt` → `eza` (icons + git), `cls` → `clear`,
+`cat`/`du`/`df`/`ps` → their modern equivalents (see "Replacing the classics").
+git aliases live in git.nix (below).
+
+## CLI tools
+
+| Tool                     | What it gives you                                                                                                                                                                                                                   |
+| ------------------------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| `fzf`                    | `Ctrl-R` fuzzy history, `Ctrl-T` file picker, `Alt-C` fuzzy cd (Catppuccin-themed)                                                                                                                                                  |
+| `zoxide`                 | `z <fragment>` jumps to frecent directories                                                                                                                                                                                         |
+| `direnv` + `nix-direnv`  | per-project environments auto-loaded on `cd` (cached Nix dev shells)                                                                                                                                                                |
+| `eza`                    | modern `ls` (drives the ls aliases)                                                                                                                                                                                                 |
+| `bat`                    | syntax-highlighting pager (Catppuccin Mocha theme); behaves like `cat` when piped; also the `MANPAGER`                                                                                                                              |
+| `ripgrep` / `fd`         | fast search (`rg`) and find (`fd`); also back `fzf`                                                                                                                                                                                 |
+| `jq`                     | JSON processor                                                                                                                                                                                                                      |
+| `gh` / `tea`             | GitHub and Gitea (`code.emmathe.dev`) CLIs; `gh` uses SSH                                                                                                                                                                           |
+| `nix-index`              | `command-not-found`: an unknown command tells you which Nix package provides it (prebuilt DB, no manual indexing)                                                                                                                   |
+| `comma` (`,`)            | run an uninstalled program once: `, cowsay hi`                                                                                                                                                                                      |
+| `nh`                     | nicer `nixos-rebuild`/`home-manager` with diffs; `$NH_FLAKE` set to the repo. No scheduled GC (it could reap paths a running generation still references) — collect garbage manually with `nh clean all` / `nix-collect-garbage -d` |
+| `btop`                   | resource monitor, themed Catppuccin Mocha (vendored theme)                                                                                                                                                                          |
+| `lazygit`                | git TUI for staging/rebasing, themed to match (`git.nix`)                                                                                                                                                                           |
+| `hyperfine` / `sd`       | command-line benchmarking; saner find-and-replace than sed                                                                                                                                                                          |
+| `tldr` (tealdeer)        | worked examples for a command, alongside `man`; the page cache is refreshed by a `tldr-update` user timer                                                                                                                           |
+| `jnv` / `fq`             | interactive jq-filter builder for JSON; jq syntax over binary formats (ELF, PNG, gzip, mp4…)                                                                                                                                        |
+| `hexyl`                  | hex viewer, coloured by byte class                                                                                                                                                                                                  |
+| `ouch`                   | one command for every archive format (`ouch d`/`c`/`l`)                                                                                                                                                                             |
+| `dust` `dysk` `procs`    | `du` / `df` / `ps` replacements — aliased over the originals, see below                                                                                                                                                             |
+| `trash-cli` `doggo` `xh` | `rm` (to the XDG trash) / `dig` / `curl` replacements — **not** aliased, see below                                                                                                                                                  |
+
+**Theming:** `fzf`, `bat`, `btop`, `lazygit` and `git`'s `delta` pager are all
+Catppuccin Mocha, driven from the shared `../lib/catppuccin-mocha.nix` palette / the
+catppuccin upstream themes.
+
+**Env & defaults:** `xdg.enable` on; `PAGER`/`MANPAGER` (bat) set in `default.nix`
+(the editor owns `$EDITOR`/`$VISUAL`); `xdg.mimeApps` maps web→Firefox,
+directories→nemo (`desktop.nix`).
+
+## Replacing the classics
+
+Muscle memory is the expensive part of this, not the packages. Four commands are
+**shadowed** — the old name now runs a new tool. Everything else keeps a new
+name, so the original is never displaced.
+
+### Shadowed by an alias
+
+| You type | You now run          | The original is still `command <name>` / `\<name>` |
+| -------- | -------------------- | -------------------------------------------------- |
+| `cat`    | `bat --paging=never` | `command cat`                                      |
+| `du`     | `dust`               | `command du`                                       |
+| `df`     | `dysk`               | `command df`                                       |
+| `ps`     | `procs`              | `command ps`                                       |
+
+Only read-only commands are shadowed, so the worst case of a wrong flag is a
+retype rather than lost data. `rm`, `grep`, `curl` and `find` are deliberately
+left alone — see "Left alone on purpose" below.
+
+**Where the aliases apply.** They are written into `~/.config/zsh/.zshrc`, so
+they exist only in an **interactive zsh**:
+
+- shell scripts, `Makefile` recipes and anything another program `exec`s get the
+  real coreutils binary — nothing that parses output can break;
+- `sudo du -sh /var` runs the real `du`: zsh does not expand an alias after
+  `sudo`;
+- `KUBECONFIG=… kubectl …` **does** expand — zsh expands aliases after a
+  variable-assignment prefix. That is what makes the kubecolor alias on the work
+  box (below) useful rather than a special case you have to remember.
+
+### Flag gotchas
+
+These replacements are not drop-in. The two marked **silent** are the dangerous
+ones — they succeed and answer a different question than the one you asked.
+Everything else fails loudly.
+
+| Old habit           | What happens now                                                                                                      | Do this instead                                                     |
+| ------------------- | --------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------- |
+| `du -sh dir`        | dust prints its usage and exits non-zero — `-h` is not a dust flag                                                    | `dust dir` (units are human by default; the total is the last row)  |
+| `du -s dir`         | **silent**: dust's `-s` is `--apparent-size`, not `--summarize`                                                       | `dust -d 0 dir` for a single total line                             |
+| `du --max-depth=2`  | not recognised                                                                                                        | `dust -d 2`                                                         |
+| `df -h`             | dysk rejects `-h`                                                                                                     | `dysk` (SI units by default; `-u binary` for 1024-based)            |
+| `df -i`             | not recognised                                                                                                        | `dysk -c +inodes`                                                   |
+| `df -a`             | works, same meaning (all mount points)                                                                                | —                                                                   |
+| `df /some/path`     | works, same meaning (the device holding that path)                                                                    | —                                                                   |
+| `ps aux`            | **silent**: `aux` is read as a search keyword, so you get only processes whose command line contains the string "aux" | `procs` lists everything; `procs <pattern>` filters                 |
+| `ps -ef`            | `error: unexpected argument '-e'`                                                                                     | `procs`                                                             |
+| `ps -p 1234`        | not recognised                                                                                                        | `procs 1234`                                                        |
+| `procs -a`          | **silent**: `-a` is `--and` (combine search keywords), not "all"                                                      | drop it — `procs` already shows everything                          |
+| `cat -v` / `cat -e` | `error: unexpected argument`                                                                                          | `cat -A` does work (bat implements show-all); else `command cat -v` |
+| `cat -n`            | works, but bat's number column, not coreutils' layout                                                                 | fine to read; `command cat -n` when the exact layout matters        |
+| `cat <binary>`      | prints `<BINARY>` to a terminal instead of dumping the bytes                                                          | `hexyl <file>`, or `command cat` to dump                            |
+
+Useful new capabilities in the same tools: `procs --tree`, `procs --watch`,
+`dust -r` (largest at the top), `dysk -s size`, `dysk -f 'type=ext4'`.
+
+**Piping is safe for `cat`.** bat drops all decoration and colour when stdout is
+not a terminal, so `cat f | sha256sum` is byte-for-byte what coreutils `cat`
+would have given. The others are TUI-shaped tables with no stable format — if
+something needs to parse them, use `dysk --json`/`--csv`, `procs --json`, or the
+original binary.
+
+### Renamed, not shadowed
+
+| Instead of                  | Use     | Notes                                                                                                                                                                                                |
+| --------------------------- | ------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| `rm`                        | `trash` | Moves to the XDG trash. `trash-list`, `trash-restore` (interactive picker), `trash-empty [days]`. It never deletes in place: if it cannot create a trash directory on that filesystem it errors out. |
+| `dig` / `nslookup`          | `doggo` | `doggo example.com MX @1.1.1.1`; `--json` for scripting. Not aliased — `dig` (from the `bind` closure that other modules pull in) stays where scripts expect it.                                     |
+| `curl` (interactive poking) | `xh`    | HTTPie syntax: `xh POST api.example/x name=lyra`. `xhs` is `xh --https`. **curl stays installed and unaliased** — it is what scripts and CI use.                                                     |
+| `tar` / `unzip` / `7z`      | `ouch`  | `ouch d file.<anything>`, `ouch c out.tar.zst src/`, `ouch l archive`. Format is inferred from the extension. The oh-my-zsh `extract` function still works too.                                      |
+| `jq` (exploring a payload)  | `jnv`   | Interactive filter builder over a JSON file; it prints the jq expression you built. `jq` remains the scripting tool.                                                                                 |
+| `hexdump -C` / `xxd`        | `hexyl` | `hexyl -n 256 -s 0x40 file` for a window into a large file.                                                                                                                                          |
+| `strings` on a known format | `fq`    | jq syntax over binary formats: `fq -d elf '.sections[].name' ./bin`.                                                                                                                                 |
+| skimming a man page         | `tldr`  | Worked examples. `man` is untouched (and still rendered through bat).                                                                                                                                |
+
+### Left alone on purpose
+
+- **`grep`** is not aliased to `rg`. ripgrep is recursive by default, skips
+  gitignored and hidden files, and uses a different regex dialect (no
+  backreferences, no POSIX classes in the same form). A `grep` habit silently
+  producing fewer matches is a worse failure than typing three characters. Type
+  `rg`.
+- **`rm`** is not aliased to `trash-put`. Retraining `rm` to mean "recoverable"
+  is a habit that follows you onto every machine where it is not — remote hosts,
+  root shells, containers, CI. Type `trash`.
+- **`find`** is not aliased to `fd`; the `-exec`/`-print0` vocabulary has no
+  equivalent and scripts lean on it. Type `fd`.
+- **`sed`** is not aliased to `sd`; `sd` takes real regex and literal
+  replacements, not sed's expression language. Type `sd`.
+- **coreutils itself** is not swapped for `uutils-coreutils`. It is packaged and
+  tempting, but every Nix builder and shell script on these hosts is written
+  against GNU behaviour, including its forty-year-old edge cases.
+
+### Work box only: kubectl → kubecolor
+
+On EDaaS (`work.nix`) `kubectl` is aliased to **kubecolor**, which runs the real
+kubectl underneath and colourises what comes back. Nothing to relearn: every
+flag, subcommand and plugin passes straight through, unrecognised output is
+printed verbatim, and colour is dropped automatically when stdout is not a
+terminal — so `kubectl get -o json … | jq` is unchanged. The alias also applies
+to `KUBECONFIG=prodconfig kubectl …`, per the alias-expansion note above.
+Completions are kubectl's own (`compdef kubecolor=kubectl`). Escape hatch as
+ever: `command kubectl`.
+
+### sudo → sudo-rs
+
+Every NixOS host now uses **sudo-rs**, the memory-safe reimplementation, in
+place of `sudo` (`modules/common-nixos.nix`; the macOS host keeps Apple's sudo
+with Touch ID). Day to day there is nothing to learn — `sudo`, `sudo -i`,
+`sudo -u`, `sudo -l`, `sudoedit` and `visudo` all behave as before against this
+fleet's stock "wheel, with a password" policy. What it does **not** implement:
+host aliases, LDAP/SSSD sudoers, `sudoreplay`, and most `Defaults` settings.
+Needing any of those means reverting to `security.sudo`.
+
+If a host ever refuses to escalate, get a root shell that does not go through
+sudo (`wsl -u root -d NixOS` on the work box; the console or a serial/HDMI login
+elsewhere) and roll back with `nixos-rebuild switch --rollback`, or pick the
+previous generation from the boot menu.
+
+## tmux
+
+**Auto-start:** opening any interactive terminal — foot, iTerm2, the WSL shell, the
+Linux console — drops you straight into a tmux session named `main` (attach if it
+exists, else create). Panes run a plain non-login zsh. It deliberately does **not**
+fire for SSH sessions, VS Code's integrated terminal, already-inside-tmux, or
+non-interactive shells. Escape hatch: `NO_TMUX=1 <terminal>` opens a bare shell.
+
+| Setting                          | Value                                                                                                                                      |
+| -------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------ |
+| Mode keys                        | vi                                                                                                                                         |
+| Mouse                            | on                                                                                                                                         |
+| Scrollback                       | 500000 lines                                                                                                                               |
+| `escape-time`                    | 10ms (the 500ms default lagged vim's ESC)                                                                                                  |
+| `focus-events`                   | on (vim autoread)                                                                                                                          |
+| `base-index` / `pane-base-index` | 1                                                                                                                                          |
+| Splits                           | `prefix s` vertical, `prefix v` horizontal (stock `%`/`"` unbound)                                                                         |
+| Pane nav                         | `Alt`+arrows (no prefix)                                                                                                                   |
+| Terminal                         | `default-terminal tmux-256color`; truecolor advertised per outer terminal (`foot*`, `xterm-256color`/iTerm2) via `terminal-features … RGB` |
+| Clipboard                        | `set-clipboard on`; foot `terminal-features` advertise truecolor/sync/OSC52/title/cursor                                                   |
+
+**Plugins:** `sensible`, `vim-tmux-navigator` (Ctrl-h/j/k/l across vim ↔ tmux),
+`yank`, `extrakto` (`prefix`+`Tab`: fzf-grab paths/URLs/text from the pane into
+the prompt), `catppuccin` (Mocha statusline), `resurrect` + `continuum`
+(sessions auto-save and restore across reboots). The statusline draws Nerd-Font
+glyphs — see Fonts.
+
+## Fonts
+
+**JetBrainsMono Nerd Font**, **Noto Sans** and **Noto Color Emoji** are
+installed on every host (in `common-nixos.nix`, because tmux/terminals run
+everywhere; the Mac installs the Nerd Font to `/Library/Fonts` via the Darwin
+config). `fonts.fontconfig.defaultFonts` maps the generic families so anything
+asking for `monospace` gets the Nerd Font (with emoji fallback) — this also
+gives the WSL box emoji/sans coverage it otherwise lacked. foot uses the Nerd
+Font as its main font automatically. iTerm2's font is a GUI setting — set it to
+_JetBrainsMono Nerd Font_ (Settings → Profiles → Text → Font) so the tmux
+statusline glyphs render instead of `?`.
+
+## Editor (Neovim)
+
+`nvim` — aliased to `vi`/`vim`, and set as `$EDITOR`/`$VISUAL` — is configured
+declaratively with **nixvim**, so the same plugins and config are baked in on
+every host. Migrated from plain vim; the practical gain is a real LSP stack in
+place of the old (inert) ALE.
+
+| Feature        | Notes                                                                                     |
+| -------------- | ----------------------------------------------------------------------------------------- |
+| Colorscheme    | Catppuccin Mocha (matches the terminal and the rest of the desktop)                       |
+| File tree      | nvim-tree, toggled with `,,` (comma twice; was nerdtree)                                  |
+| Fuzzy finder   | telescope (+fzf-native): `<leader>ff` files, `<leader>fg` grep, `<leader>fb` buffers      |
+| Format on save | conform-nvim (nixfmt, stylua, ruff, shfmt, prettier, gofumpt; LSP fallback otherwise)     |
+| Git            | fugitive (`:Git …`) + gitsigns gutter signs/blame                                         |
+| Diagnostics    | inline + trouble list (`<leader>xx`)                                                      |
+| Completion     | nvim-cmp (LSP/buffer/path) with luasnip snippet expansion                                 |
+| Indent guides  | indent-blankline, on by default (was vim-indent-guides)                                   |
+| Statusline     | lualine (Catppuccin theme)                                                                |
+| Editing        | which-key hints, comment (`gc`/`gcc`), autopairs, treesitter textobjects                  |
+| Pane nav       | vim-tmux-navigator — `Ctrl`+`h/j/k/l` moves across vim splits and tmux panes              |
+| Syntax         | tree-sitter (nix, lua, bash, markdown, groovy, c#, python, terraform, yaml)               |
+| LSP            | nvim-cmp completion + servers `nil_ls` (Nix), `lua_ls`, `pyright` (Python), `terraformls` |
+| Indentation    | 2-wide hard tabs (`noexpandtab`, `tabstop`/`shiftwidth` = 2); line numbers on             |
+| Filetypes      | `*Jenkinsfile` → groovy                                                                   |
+
+Leader is `Space`. LSP keymaps (`gd`, `gr`, `K`, `<leader>rn`, `<leader>ca`) and
+the file-tree toggle are listed in
+[`keybindings.md`](./keybindings.md#neovim). Add a universal language server by
+enabling it under `programs.nixvim.plugins.lsp.servers` in `editor.nix`;
+host-specific ones go in that host's module — the work box (`work.nix`) adds
+`omnisharp` (C#) and `helm_ls` (Helm), kept off the personal machines.
+
+## git
+
+Pager is **delta**. **commitizen** is installed on every host; `cz` defaults to
+Conventional Commits. **lazygit** (themed) is the TUI. The commit-graph is kept
+current (`gc`/`fetch.writeCommitGraph`) so `lg` stays fast.
+
+| Aliases                  |                                                                           |
+| ------------------------ | ------------------------------------------------------------------------- |
+| `st` `co` `sw` `br` `ci` | status / checkout / switch / branch / commit                              |
+| `last` `unstage`         | last commit / unstage                                                     |
+| `amend` `fixup` `undo`   | amend-no-edit / `commit --fixup` / soft-reset HEAD~1 (keep staged)        |
+| `lg`                     | graph log, all branches                                                   |
+| `cz` `cc`                | `git cz <sub>` (e.g. `git cz c`) and `git cc` → commitizen prompt         |
+| `dft`                    | structural (syntax-aware) diff via difftastic; takes `git diff` arguments |
+
+**`git dft` vs `git diff`.** delta stays the default renderer for everything;
+`diff.external` is deliberately **not** set, so `git diff`, `git show` and
+anything parsing their output are unchanged. Reach for `dft` when a refactor
+moved code around and a line-based diff is noise. One wrinkle: `dft` is a
+`!`-shell alias, and git runs those from the repository root — pass pathspecs
+relative to the root, not to your current directory.
+
+| Behaviour      |                                                                                                                                                                                                                |
+| -------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| Pulls          | rebase, with autostash + autosquash                                                                                                                                                                            |
+| Fetch          | prune deleted remote branches                                                                                                                                                                                  |
+| Conflicts      | `zdiff3` (shows the common ancestor)                                                                                                                                                                           |
+| Diffs          | histogram algorithm, colour-moved                                                                                                                                                                              |
+| `rerere`       | remembers + replays conflict resolutions                                                                                                                                                                       |
+| Commit editor  | full diff shown (`commit.verbose`)                                                                                                                                                                             |
+| Misc           | branches sorted by date, `column.ui = auto`, `help.autocorrect = prompt`, `push.autoSetupRemote`                                                                                                               |
+| Global ignores | `result`, `result-*`, `.direnv`, `*.swp`, `.DS_Store`                                                                                                                                                          |
+| Signing        | SSH commit + tag signing (`mkDefault`, so a host without the key in its agent can disable it). Name, email and signing key all come from the per-user `identity` (the user registry, `../users/registry.nix`). |
+
+## ssh
+
+| Feature      | Notes                                                                                                                                                |
+| ------------ | ---------------------------------------------------------------------------------------------------------------------------------------------------- |
+| ssh-agent    | runs on Linux (launchd on macOS); keys added on **first use** so the passphrase is typed once per login session — this also feeds git commit signing |
+| macOS        | `UseKeychain` caches the passphrase in the login keychain (guarded by `IgnoreUnknown`, so a non-Apple `ssh` skips it instead of erroring)            |
+| Gitea remote | `code.emmathe.dev` → `HostName 10.187.1.76` (DNS-override), `Port 30009`, user `git`, dedicated key, `identitiesOnly`                                |
+| Defaults     | the module's deprecated default block is opted out; equivalents kept under `settings."*"`                                                            |
+
+The **work box keeps its own `~/.ssh/config`** (home-manager's `programs.ssh` is
+forced off there) but still runs the agent.
+
+## Claude Code
+
+Managed declaratively by [`claude.nix`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/home/claude.nix) on every host whose CPU
+can run it (the CLI is `pkgs.claude-code`, tracked to unstable via the flake
+overlay).
+
+**Capability gate.** The module installs nothing — CLI or files — when
+`osConfig.features.claudeCode.enable` is off. That flag is derived fleet-wide
+from the host's declared CPU level (see "CPU capability gating" in the root
+README): the Node runtime needs SSE4.2/POPCNT, so anything below x86-64-v2 (the
+Mac Pro 3,1) is excluded. Hosts that do not define the option — the Darwin host
+and the standalone `homeConfigurations` — keep it enabled.
+
+| Managed (static, from Nix)                          | Left mutable (runtime state)                           |
+| --------------------------------------------------- | ------------------------------------------------------ |
+| `~/.claude/CLAUDE.md` (persona + memory workflow)   | `settings.json` (permissions, model, theme, `/config`) |
+| `~/.claude/output-styles/soviet-engineer.md`        | `.credentials.json`, history, caches                   |
+| `~/.claude/memory/` (read-only symlink to the repo) |                                                        |
+
+`settings.json` is intentionally **not** managed: Claude rewrites it at runtime
+(interactive permission grants, `/config`), which a read-only store symlink would
+break.
+
+**Memory is sourced from this repo.** The files in
+[`claude/memory/`](https://code.emmathe.dev/lyrathorpe/nixfiles/src/branch/main/home/claude/memory) are the source of truth; they are symlinked
+read-only into `~/.claude/memory`, so recall works but the runtime "save a
+memory" path does not. To add/change/remove a memory, edit `claude/memory/`
+(one file per memory + the `MEMORY.md` index) and rebuild — `CLAUDE.md` tells
+Claude to route new memories there.
+
+## Maintenance behaviours
+
+- **zcompdump reset** — `~/.config/zsh/.zcompdump*` (plus legacy `~/.zcompdump*`
+  and the cache copy) is removed on every activation, so a stale
+  dump (pointing at `/nix/store` paths a rebuild or a manual GC removed) can't
+  break completion with `_git: function definition file not found`.
+- **GC** — no scheduled timer; collect garbage deliberately (`nh clean all` /
+  `nix-collect-garbage -d`) when no important session is running.
+
+## Per-host differences
+
+|                             | Personal Linux (sway) | macOS                 | Work WSL (EDaaS)            |
+| --------------------------- | --------------------- | --------------------- | --------------------------- |
+| Auto-tmux                   | yes (foot/TTY)        | yes (iTerm2)          | yes (WSL shell)             |
+| `kubectl` → kubecolor       | no (no kubectl)       | no                    | yes (work module)           |
+| `sudo` implementation       | sudo-rs               | Apple sudo + Touch ID | sudo-rs                     |
+| git email                   | `iam@emmathe.dev`     | `iam@emmathe.dev`     | `…@citrix.com` (work)       |
+| ssh config managed          | yes                   | yes                   | no (keeps corporate config) |
+| ssh-agent                   | yes                   | launchd               | yes (work module)           |
+| GUI / theming (desktop.nix) | yes                   | no                    | no                          |

flake.lock

@@ -3,16 +3,16 @@
     "brew-src": {
       "flake": false,
       "locked": {
-        "lastModified": 1785710351,
+        "lastModified": 1786348930,
-        "narHash": "sha256-DTL5T9+HlblsnXCEdxRpEo/2NBHD3t48BS7r+PTf090=",
+        "narHash": "sha256-bCQJkbgsAMDp5HQystZLCq11UHiyEuoWbxKulAPYrh8=",
         "owner": "Homebrew",
         "repo": "brew",
-        "rev": "7b0f22a4ab77567edef114c8dfc423fb96e2fbaa",
+        "rev": "3ecc9eff23feebf1bc73846d74e14a122c93b66f",
         "type": "github"
       },
       "original": {
         "owner": "Homebrew",
-        "ref": "6.0.15",
+        "ref": "6.0.16",
         "repo": "brew",
         "type": "github"
       }
@@ -25,11 +25,11 @@
       },
       "locked": {
         "dir": "pkgs/firefox-addons",
-        "lastModified": 1786248171,
+        "lastModified": 1786853140,
-        "narHash": "sha256-ALbtZKFam+O2ONRk7XhYsXmXxmhR0Y3Bj+qZkTA8zCg=",
+        "narHash": "sha256-O880FlUav75Q5aNlg9znyg/avf1X/W7o/cAtZFLtpWc=",
         "owner": "rycee",
         "repo": "nur-expressions",
-        "rev": "2e85abc79236d031845a0e2be3ebbd1759cea715",
+        "rev": "ba9568c9c0df6290dc2f34b032ab4cb575e73788",
         "type": "gitlab"
       },
       "original": {
@@ -114,11 +114,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1778716662,
+        "lastModified": 1785627969,
-        "narHash": "sha256-m1Yf0wZ8j1OHjTc2UwHwyQRSnNeSgLJOd7q5Y45hzi4=",
+        "narHash": "sha256-4dtXQk/NMePegK/nWp5NSeuZKLATItOq61lpEvmXqGw=",
         "owner": "hercules-ci",
         "repo": "flake-parts",
-        "rev": "f7c1a2d347e4c52d5fb8d10cb4d94b5884e546fb",
+        "rev": "427bf4bd9435fdf21321c8cc628c24efc14c0f7a",
         "type": "github"
       },
       "original": {
@@ -155,11 +155,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1785119570,
+        "lastModified": 1786924861,
-        "narHash": "sha256-Rgs2xKnGLFWQscxUaXX07oyZeuMDOHEbqDOsgliLFGM=",
+        "narHash": "sha256-hftabkb+73OcGzvwFAjCiQorAhprs9TnU1+FkGO5CIw=",
         "owner": "nix-community",
         "repo": "home-manager",
-        "rev": "d4fd24667c8cbef124bb70a20380cab75ec8474d",
+        "rev": "09ae1b85a6db412d841d60f924b23f881f0d0a38",
         "type": "github"
       },
       "original": {
@@ -185,6 +185,26 @@
         "type": "github"
       }
     },
+    "legacy-email-proxy": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1787315211,
+        "narHash": "sha256-FuZ9nXMRtnMPO/wbjYkpsKn6K/FFc64P5XDmCyfyxGs=",
+        "ref": "refs/heads/main",
+        "rev": "f1e1373fd350fd77f1848eddfa67ed9e00724c25",
+        "revCount": 13,
+        "type": "git",
+        "url": "https://code.emmathe.dev/lyrathorpe/legacy-email-proxy"
+      },
+      "original": {
+        "type": "git",
+        "url": "https://code.emmathe.dev/lyrathorpe/legacy-email-proxy"
+      }
+    },
     "nix-darwin": {
       "inputs": {
         "nixpkgs": [
@@ -211,11 +231,11 @@
         "brew-src": "brew-src"
       },
       "locked": {
-        "lastModified": 1786217209,
+        "lastModified": 1786686423,
-        "narHash": "sha256-rusAj5QBnbSwXG6csns6dwxTeCOGRcj08VmlnhUQ6ZY=",
+        "narHash": "sha256-8q3WdB8o3VUI7rOz1OXfioXIaaWbFTAxRJAkWLlfc0s=",
         "owner": "zhaofengli",
         "repo": "nix-homebrew",
-        "rev": "486357ea434dc0061ea52121ff99b1d33096c811",
+        "rev": "ccabf79a6b9845eb72b51ea1d9c7ce3446350df3",
         "type": "github"
       },
       "original": {
@@ -231,11 +251,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1786249295,
+        "lastModified": 1786852476,
-        "narHash": "sha256-Y2mSr+HLKYoOsjiackgilxkHXe8gkJ3z4hFFekjQX3I=",
+        "narHash": "sha256-IM5CYtf86W4w8eUPpKcY/LpdHElmVBtJhaKnoTKxZEA=",
         "owner": "nix-community",
         "repo": "nix-index-database",
-        "rev": "14d55b8069119e3b88da7aa2f6c97f86a2cd3cd6",
+        "rev": "c7962dc97b45129df8d751bedaf37beb5a17706e",
         "type": "github"
       },
       "original": {
@@ -252,11 +272,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1785426242,
+        "lastModified": 1786862401,
-        "narHash": "sha256-QHAP8KsJQmI+dpNS/wfWAtEBQ0Zby+B0Ty+qZIO/U2w=",
+        "narHash": "sha256-zRPYCn5RJWxr9uyUwNIQjPsTFcIFRwuRnI91dqvGA0k=",
         "owner": "nix-community",
         "repo": "nixos-apple-silicon",
-        "rev": "66d8dd2c27f99bd5420c99938b60695aac1785c4",
+        "rev": "53798a0eb0fa4c8cfaeca7bdc5b4ad22ed210c95",
         "type": "github"
       },
       "original": {
@@ -272,11 +292,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1785232496,
+        "lastModified": 1786867632,
-        "narHash": "sha256-65EQYIRRpTdpH8lUiB6Mvo5uBkG60aBIzAJuALfx+O0=",
+        "narHash": "sha256-ez+ubZlA1RtdjCB18a6zJ9M4u8qoPDy08EcnsW5M3Xw=",
         "owner": "NixOS",
         "repo": "nixos-hardware",
-        "rev": "2e790b0a6be8ec2b76174ac0931b8ff11919ec98",
+        "rev": "ff17823245ab9ff7bcae6acf950bd89cba82c38c",
         "type": "github"
       },
       "original": {
@@ -308,11 +328,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1786201459,
+        "lastModified": 1786711500,
-        "narHash": "sha256-CiOTEjmwAmG2AWnaIno9YaCJJmpca2FXPhMAsnrolCg=",
+        "narHash": "sha256-QvnceIGTBeDvDd9oCn+GvdsnkquliuwbVgpiRH68qaQ=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "8b8c811c7c2541c30382c5de7ed26be055569c60",
+        "rev": "02e08985a27c65ffd33d434eeb2e660a2e4dc84d",
         "type": "github"
       },
       "original": {
@@ -324,11 +344,11 @@
     },
     "nixpkgs-unstable": {
       "locked": {
-        "lastModified": 1786106723,
+        "lastModified": 1786862985,
-        "narHash": "sha256-zDSUbpoeo/9ZmD2+wXnzxoo1+uhL8vxc0b8yuYMKYq0=",
+        "narHash": "sha256-FBJRXmbGXiSUDvYEbfLYRkckayyZ6SK1UEqhCrIZ2Cs=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "f13ff45afd1bb73e640eaa08a7066dbed07e3238",
+        "rev": "e5bdc4a41d4c072fe1e3787eaa0320a384741d44",
         "type": "github"
       },
       "original": {
@@ -347,11 +367,11 @@
         "systems": "systems"
       },
       "locked": {
-        "lastModified": 1782919967,
+        "lastModified": 1786873773,
-        "narHash": "sha256-pRwjfB5HQJ3m8J8bOR43pPHtHI7VUJSqwLA3P06cOY0=",
+        "narHash": "sha256-Hj/nkhKDv0aJly1PAUstrhrgEYn1mVSkLIYMh90r/Pc=",
         "owner": "nix-community",
         "repo": "nixvim",
-        "rev": "667c8471f4a0fb24d702d1a61af8609f1a5f1ba6",
+        "rev": "b397fb9f6950d57355d62bb92457d223464e0115",
         "type": "github"
       },
       "original": {
@@ -368,6 +388,7 @@
         "git-hooks": "git-hooks",
         "home-manager": "home-manager",
         "kube-tmux": "kube-tmux",
+        "legacy-email-proxy": "legacy-email-proxy",
         "nix-darwin": "nix-darwin",
         "nix-homebrew": "nix-homebrew",
         "nix-index-database": "nix-index-database",
@@ -402,11 +423,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1785945821,
+        "lastModified": 1786901030,
-        "narHash": "sha256-NLSyTCW4K4ofhNBllt3omPasm6QpralXH1DBZOc91Dw=",
+        "narHash": "sha256-WSFCsDSE5ffgD2MqzkM2CYjeFiKhRF/dJUN8uedb6YE=",
         "owner": "numtide",
         "repo": "treefmt-nix",
-        "rev": "ae7910970dddc408fe6ab1c8e4b277bb21d72dc0",
+        "rev": "27b3b12a8e6375f28ebe122f07d230ca5459bbfa",
         "type": "github"
       },
       "original": {

flake.nix

@@ -67,6 +67,13 @@
       url = "github:jonmosco/kube-tmux";
       flake = false;
     };
+    # legacy-email-proxy: cleartext POP3/SMTP front end for the Psion's mail
+    # client, proxied to authenticated IMAPS/SMTPS. Ships its own package and
+    # NixOS module; the Pi Zero 2 W host just enables the service.
+    legacy-email-proxy = {
+      url = "git+https://code.emmathe.dev/lyrathorpe/legacy-email-proxy";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
   };
 
   outputs =
@@ -111,8 +118,14 @@
         ];
 
         # Unfree packages permitted to be built (replaces blanket allowUnfree).
+        # The NVIDIA entries are for the Mac Pro's Quadro P400 (hosts/MacPro31/
+        # nvidia.nix); unfree packages are not in the binary cache, so the
+        # kernel module is compiled on the host.
         unfreePackages = [
           "claude-code"
+          "nvidia-x11"
+          "nvidia-kernel-modules"
+          "nvidia-settings"
         ];
 
         # Per-user identity, keyed by username. See README "Users".
@@ -321,6 +334,26 @@
               ./users/lyrathorpe/home.nix
             ];
           };
+
+          lyrathorpe-zero2w = {
+            system = "aarch64-linux";
+            portable = false;
+            # Headless "Psion sidecar": PPP over RS232 plus a legacy mail proxy
+            # (hosts/PiZero2W/). No sway.nix; the raspberry-pi-3 profile carries
+            # the kernel/firmware/device tree (the Zero 2 W is the Pi 3's
+            # BCM2837 SoC) and ssh.nix adds key-only sshd. This board has 512 MB
+            # of RAM and never builds its own system -- see
+            # docs/hosts/pizero2w.md.
+            modules = [
+              ./hosts/PiZero2W/configuration.nix
+              inputs.nixos-hardware.nixosModules.raspberry-pi-3
+              ./modules/ssh.nix
+            ];
+            users.lyrathorpe.homeModules = [
+              ./home
+              ./users/lyrathorpe/home.nix
+            ];
+          };
         };
 
         # Darwin host table — macOS machines built via mkDarwinHost. The shared
@@ -359,8 +392,24 @@
         # nixpkgs instance for that system. Outputs here become per-system
         # attrsets automatically (e.g. devShells.<system>.default).
         perSystem =
-          { config, pkgs, ... }:
           {
+            config,
+            pkgs,
+            system,
+            ...
+          }:
+          {
+            # One-shot SD card for bringing the Pi Zero 2 W up: that host's own
+            # configuration plus the sd-image module, so the first boot is
+            # already the real system. aarch64-linux only -- building it needs
+            # an aarch64 Linux builder. See docs/hosts/pizero2w.md.
+            packages = lib.optionalAttrs (system == "aarch64-linux") {
+              zero2w-sd-image =
+                ((mkHost hosts.lyrathorpe-zero2w).extendModules {
+                  modules = [ ./hosts/PiZero2W/sd-image.nix ];
+                }).config.system.build.sdImage;
+            };
+
             # treefmt drives `nix fmt` and the formatting check below. nixfmt
             # stays the .nix formatter (the tree is already nixfmt-formatted);
             # shfmt covers shell and prettier covers markdown/yaml/json.

home/README.md

@@ -1,215 +0,0 @@
-# Interactive shell environment
-
-Everything the shell, terminal multiplexer, git and ssh do beyond their defaults,
-and where each is defined. All of it is managed declaratively through
-home-manager — edit the listed file and rebuild, never the generated dotfiles.
-
-Keyboard shortcuts have their own reference: [`KEYBINDINGS.md`](./KEYBINDINGS.md).
-
-| Area                                   | Defined in                                            |
-| -------------------------------------- | ----------------------------------------------------- |
-| zsh, CLI tools, tmux, ssh, auto-tmux   | [`shell.nix`](./shell.nix)                            |
-| git (+ delta, commitizen)              | [`git.nix`](./git.nix)                                |
-| Neovim (nixvim) + LSP                  | [`editor.nix`](./editor.nix)                          |
-| Claude Code (CLAUDE.md, style, memory) | [`claude.nix`](./claude.nix)                          |
-| GUI apps, GTK/Firefox theming, cursor  | [`desktop.nix`](./desktop.nix) (graphical hosts only) |
-
-Shared by every host via [`default.nix`](./default.nix); the work box also layers
-[`work.nix`](../users/emmathorpe/work.nix) on top (its own ssh config, extra
-packages, and the C#/Helm language servers). The committer identity (name, email,
-signing key) comes from the user registry
-([`../users/registry.nix`](../users/registry.nix)), not this module.
-
----
-
-## zsh
-
-| Feature                  | Notes                                                                                                                                          |
-| ------------------------ | ---------------------------------------------------------------------------------------------------------------------------------------------- |
-| oh-my-zsh                | plugins `git`, `man`, `sudo` (Esc-Esc to prepend sudo), `colored-man-pages`, `extract`; theme `robbyrussell`                                   |
-| Autosuggestion           | fish-style history suggestions as you type (→ to accept)                                                                                       |
-| Syntax highlighting      | commands coloured by validity as you type                                                                                                      |
-| Completion               | menu completion; the dump is rebuilt on every activation (see Maintenance)                                                                     |
-| History                  | 100k in-memory/on-disk, deduped, space-prefixed commands ignored, timestamped, **shared live across sessions**; file stays at `~/.zsh_history` |
-| Dotfiles location        | `dotDir` is `~/.config/zsh` (XDG) — `.zshrc`/`.zshenv`/`.zcompdump` live there; `~/.zshenv` only bootstraps `$ZDOTDIR`                         |
-| History substring search | type a fragment, then ↑/↓ cycles matching past commands — works in foot, iTerm2 and the Linux TTY (both CSI and SS3 arrow encodings bound)     |
-| Prompt                   | hostname is prefixed when over SSH                                                                                                             |
-
-**Aliases:** `ls`/`ll`/`la`/`lt` → `eza` (icons + git), `cls` → `clear`. git aliases live in git.nix (below).
-
-## CLI tools
-
-| Tool                    | What it gives you                                                                                                                                                                                                                   |
-| ----------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
-| `fzf`                   | `Ctrl-R` fuzzy history, `Ctrl-T` file picker, `Alt-C` fuzzy cd (Catppuccin-themed)                                                                                                                                                  |
-| `zoxide`                | `z <fragment>` jumps to frecent directories                                                                                                                                                                                         |
-| `direnv` + `nix-direnv` | per-project environments auto-loaded on `cd` (cached Nix dev shells)                                                                                                                                                                |
-| `eza`                   | modern `ls` (drives the ls aliases)                                                                                                                                                                                                 |
-| `bat`                   | syntax-highlighting pager (Catppuccin Mocha theme); behaves like `cat` when piped; also the `MANPAGER`                                                                                                                              |
-| `ripgrep` / `fd`        | fast search (`rg`) and find (`fd`); also back `fzf`                                                                                                                                                                                 |
-| `jq`                    | JSON processor                                                                                                                                                                                                                      |
-| `gh` / `tea`            | GitHub and Gitea (`code.emmathe.dev`) CLIs; `gh` uses SSH                                                                                                                                                                           |
-| `nix-index`             | `command-not-found`: an unknown command tells you which Nix package provides it (prebuilt DB, no manual indexing)                                                                                                                   |
-| `comma` (`,`)           | run an uninstalled program once: `, cowsay hi`                                                                                                                                                                                      |
-| `nh`                    | nicer `nixos-rebuild`/`home-manager` with diffs; `$NH_FLAKE` set to the repo. No scheduled GC (it could reap paths a running generation still references) — collect garbage manually with `nh clean all` / `nix-collect-garbage -d` |
-| `btop`                  | resource monitor, themed Catppuccin Mocha (vendored theme)                                                                                                                                                                          |
-| `lazygit`               | git TUI for staging/rebasing, themed to match (`git.nix`)                                                                                                                                                                           |
-| `hyperfine` / `sd`      | command-line benchmarking; saner find-and-replace than sed                                                                                                                                                                          |
-
-**Theming:** `fzf`, `bat`, `btop`, `lazygit` and `git`'s `delta` pager are all
-Catppuccin Mocha, driven from the shared `../lib/catppuccin-mocha.nix` palette / the
-catppuccin upstream themes.
-
-**Env & defaults:** `xdg.enable` on; `PAGER`/`MANPAGER` (bat) set in `default.nix`
-(the editor owns `$EDITOR`/`$VISUAL`); `xdg.mimeApps` maps web→Firefox,
-directories→nemo (`desktop.nix`).
-
-## tmux
-
-**Auto-start:** opening any interactive terminal — foot, iTerm2, the WSL shell, the
-Linux console — drops you straight into a tmux session named `main` (attach if it
-exists, else create). Panes run a plain non-login zsh. It deliberately does **not**
-fire for SSH sessions, VS Code's integrated terminal, already-inside-tmux, or
-non-interactive shells. Escape hatch: `NO_TMUX=1 <terminal>` opens a bare shell.
-
-| Setting                          | Value                                                                                                                                      |
-| -------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------ |
-| Mode keys                        | vi                                                                                                                                         |
-| Mouse                            | on                                                                                                                                         |
-| Scrollback                       | 500000 lines                                                                                                                               |
-| `escape-time`                    | 10ms (the 500ms default lagged vim's ESC)                                                                                                  |
-| `focus-events`                   | on (vim autoread)                                                                                                                          |
-| `base-index` / `pane-base-index` | 1                                                                                                                                          |
-| Splits                           | `prefix s` vertical, `prefix v` horizontal (stock `%`/`"` unbound)                                                                         |
-| Pane nav                         | `Alt`+arrows (no prefix)                                                                                                                   |
-| Terminal                         | `default-terminal tmux-256color`; truecolor advertised per outer terminal (`foot*`, `xterm-256color`/iTerm2) via `terminal-features … RGB` |
-| Clipboard                        | `set-clipboard on`; foot `terminal-features` advertise truecolor/sync/OSC52/title/cursor                                                   |
-
-**Plugins:** `sensible`, `vim-tmux-navigator` (Ctrl-h/j/k/l across vim ↔ tmux),
-`yank`, `extrakto` (`prefix`+`Tab`: fzf-grab paths/URLs/text from the pane into
-the prompt), `catppuccin` (Mocha statusline), `resurrect` + `continuum`
-(sessions auto-save and restore across reboots). The statusline draws Nerd-Font
-glyphs — see Fonts.
-
-## Fonts
-
-**JetBrainsMono Nerd Font**, **Noto Sans** and **Noto Color Emoji** are
-installed on every host (in `common-nixos.nix`, because tmux/terminals run
-everywhere; the Mac installs the Nerd Font to `/Library/Fonts` via the Darwin
-config). `fonts.fontconfig.defaultFonts` maps the generic families so anything
-asking for `monospace` gets the Nerd Font (with emoji fallback) — this also
-gives the WSL box emoji/sans coverage it otherwise lacked. foot uses the Nerd
-Font as its main font automatically. iTerm2's font is a GUI setting — set it to
-_JetBrainsMono Nerd Font_ (Settings → Profiles → Text → Font) so the tmux
-statusline glyphs render instead of `?`.
-
-## Editor (Neovim)
-
-`nvim` — aliased to `vi`/`vim`, and set as `$EDITOR`/`$VISUAL` — is configured
-declaratively with **nixvim**, so the same plugins and config are baked in on
-every host. Migrated from plain vim; the practical gain is a real LSP stack in
-place of the old (inert) ALE.
-
-| Feature        | Notes                                                                                     |
-| -------------- | ----------------------------------------------------------------------------------------- |
-| Colorscheme    | Catppuccin Mocha (matches the terminal and the rest of the desktop)                       |
-| File tree      | nvim-tree, toggled with `,,` (comma twice; was nerdtree)                                  |
-| Fuzzy finder   | telescope (+fzf-native): `<leader>ff` files, `<leader>fg` grep, `<leader>fb` buffers      |
-| Format on save | conform-nvim (nixfmt, stylua, ruff, shfmt, prettier, gofumpt; LSP fallback otherwise)     |
-| Git            | fugitive (`:Git …`) + gitsigns gutter signs/blame                                         |
-| Diagnostics    | inline + trouble list (`<leader>xx`)                                                      |
-| Completion     | nvim-cmp (LSP/buffer/path) with luasnip snippet expansion                                 |
-| Indent guides  | indent-blankline, on by default (was vim-indent-guides)                                   |
-| Statusline     | lualine (Catppuccin theme)                                                                |
-| Editing        | which-key hints, comment (`gc`/`gcc`), autopairs, treesitter textobjects                  |
-| Pane nav       | vim-tmux-navigator — `Ctrl`+`h/j/k/l` moves across vim splits and tmux panes              |
-| Syntax         | tree-sitter (nix, lua, bash, markdown, groovy, c#, python, terraform, yaml)               |
-| LSP            | nvim-cmp completion + servers `nil_ls` (Nix), `lua_ls`, `pyright` (Python), `terraformls` |
-| Indentation    | 2-wide hard tabs (`noexpandtab`, `tabstop`/`shiftwidth` = 2); line numbers on             |
-| Filetypes      | `*Jenkinsfile` → groovy                                                                   |
-
-Leader is `Space`. LSP keymaps (`gd`, `gr`, `K`, `<leader>rn`, `<leader>ca`) and
-the file-tree toggle are listed in
-[`KEYBINDINGS.md`](./KEYBINDINGS.md#neovim). Add a universal language server by
-enabling it under `programs.nixvim.plugins.lsp.servers` in `editor.nix`;
-host-specific ones go in that host's module — the work box (`work.nix`) adds
-`omnisharp` (C#) and `helm_ls` (Helm), kept off the personal machines.
-
-## git
-
-Pager is **delta**. **commitizen** is installed on every host; `cz` defaults to
-Conventional Commits. **lazygit** (themed) is the TUI. The commit-graph is kept
-current (`gc`/`fetch.writeCommitGraph`) so `lg` stays fast.
-
-| Aliases                  |                                                                    |
-| ------------------------ | ------------------------------------------------------------------ |
-| `st` `co` `sw` `br` `ci` | status / checkout / switch / branch / commit                       |
-| `last` `unstage`         | last commit / unstage                                              |
-| `amend` `fixup` `undo`   | amend-no-edit / `commit --fixup` / soft-reset HEAD~1 (keep staged) |
-| `lg`                     | graph log, all branches                                            |
-| `cz` `cc`                | `git cz <sub>` (e.g. `git cz c`) and `git cc` → commitizen prompt  |
-
-| Behaviour      |                                                                                                                                                                                                                |
-| -------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
-| Pulls          | rebase, with autostash + autosquash                                                                                                                                                                            |
-| Fetch          | prune deleted remote branches                                                                                                                                                                                  |
-| Conflicts      | `zdiff3` (shows the common ancestor)                                                                                                                                                                           |
-| Diffs          | histogram algorithm, colour-moved                                                                                                                                                                              |
-| `rerere`       | remembers + replays conflict resolutions                                                                                                                                                                       |
-| Commit editor  | full diff shown (`commit.verbose`)                                                                                                                                                                             |
-| Misc           | branches sorted by date, `column.ui = auto`, `help.autocorrect = prompt`, `push.autoSetupRemote`                                                                                                               |
-| Global ignores | `result`, `result-*`, `.direnv`, `*.swp`, `.DS_Store`                                                                                                                                                          |
-| Signing        | SSH commit + tag signing (`mkDefault`, so a host without the key in its agent can disable it). Name, email and signing key all come from the per-user `identity` (the user registry, `../users/registry.nix`). |
-
-## ssh
-
-| Feature      | Notes                                                                                                                                                |
-| ------------ | ---------------------------------------------------------------------------------------------------------------------------------------------------- |
-| ssh-agent    | runs on Linux (launchd on macOS); keys added on **first use** so the passphrase is typed once per login session — this also feeds git commit signing |
-| macOS        | `UseKeychain` caches the passphrase in the login keychain (guarded by `IgnoreUnknown`, so a non-Apple `ssh` skips it instead of erroring)            |
-| Gitea remote | `code.emmathe.dev` → `HostName 10.187.1.76` (DNS-override), `Port 30009`, user `git`, dedicated key, `identitiesOnly`                                |
-| Defaults     | the module's deprecated default block is opted out; equivalents kept under `settings."*"`                                                            |
-
-The **work box keeps its own `~/.ssh/config`** (home-manager's `programs.ssh` is
-forced off there) but still runs the agent.
-
-## Claude Code
-
-Managed declaratively by [`claude.nix`](./claude.nix) on every host (the CLI is
-`pkgs.claude-code`, tracked to unstable via the flake overlay).
-
-| Managed (static, from Nix)                          | Left mutable (runtime state)                           |
-| --------------------------------------------------- | ------------------------------------------------------ |
-| `~/.claude/CLAUDE.md` (persona + memory workflow)   | `settings.json` (permissions, model, theme, `/config`) |
-| `~/.claude/output-styles/soviet-engineer.md`        | `.credentials.json`, history, caches                   |
-| `~/.claude/memory/` (read-only symlink to the repo) |                                                        |
-
-`settings.json` is intentionally **not** managed: Claude rewrites it at runtime
-(interactive permission grants, `/config`), which a read-only store symlink would
-break.
-
-**Memory is sourced from this repo.** The files in
-[`claude/memory/`](./claude/memory) are the source of truth; they are symlinked
-read-only into `~/.claude/memory`, so recall works but the runtime "save a
-memory" path does not. To add/change/remove a memory, edit `claude/memory/`
-(one file per memory + the `MEMORY.md` index) and rebuild — `CLAUDE.md` tells
-Claude to route new memories there.
-
-## Maintenance behaviours
-
-- **zcompdump reset** — `~/.config/zsh/.zcompdump*` (plus legacy `~/.zcompdump*`
-  and the cache copy) is removed on every activation, so a stale
-  dump (pointing at `/nix/store` paths a rebuild or a manual GC removed) can't
-  break completion with `_git: function definition file not found`.
-- **GC** — no scheduled timer; collect garbage deliberately (`nh clean all` /
-  `nix-collect-garbage -d`) when no important session is running.
-
-## Per-host differences
-
-|                             | Personal Linux (sway) | macOS             | Work WSL (EDaaS)            |
-| --------------------------- | --------------------- | ----------------- | --------------------------- |
-| Auto-tmux                   | yes (foot/TTY)        | yes (iTerm2)      | yes (WSL shell)             |
-| git email                   | `iam@emmathe.dev`     | `iam@emmathe.dev` | `…@citrix.com` (work)       |
-| ssh config managed          | yes                   | yes               | no (keeps corporate config) |
-| ssh-agent                   | yes                   | launchd           | yes (work module)           |
-| GUI / theming (desktop.nix) | yes                   | no                | no                          |

home/claude.nix

@@ -1,4 +1,5 @@
-# Claude Code, configured declaratively via home-manager. Wanted on every host.
+# Claude Code, configured declaratively via home-manager. Wanted on every host
+# whose CPU can run it -- see the gate below.
 #
 # The STATIC config is managed here: the global CLAUDE.md (persona/context), the
 # custom output style, and the auto-memory directory. settings.json is
@@ -10,18 +11,33 @@
 # read-only into ~/.claude/memory, so the runtime "save a memory" path no longer
 # writes there -- recall still works, but new/changed memories must be added to
 # this repo and rebuilt. CLAUDE.md instructs Claude to do exactly that.
-{ ... }:
+{
+  lib,
+  # Set by the NixOS/Darwin home-manager module; absent for the standalone
+  # homeConfigurations, hence the default.
+  osConfig ? { },
+  ...
+}:
+let
+  # Capability gate, declared once for the whole fleet in modules/features.nix
+  # (default: on; off on CPUs below x86-64-v2, which cannot run the Node
+  # runtime Claude Code ships on). Hosts without that option -- the Darwin host
+  # and the portable standalone profile -- fall back to enabled.
+  enable = osConfig.features.claudeCode.enable or true;
+in
 {
   programs.claude-code = {
-    enable = true;
+    inherit enable;
     # package defaults to pkgs.claude-code (tracked to unstable via the flake
-    # overlay); installs the CLI on every host.
+    # overlay).
 
     # ~/.claude/CLAUDE.md -- global instructions / persona / memory workflow.
     context = ./claude/CLAUDE.md;
   };
 
-  home.file = {
+  # Nothing to place when the CLI is not installed: a ~/.claude/memory symlink
+  # with no Claude Code to read it is just dead state.
+  home.file = lib.mkIf enable {
     # Custom output style. The module has no option for output-styles/, so place
     # it directly; selection (settings.json `outputStyle`) stays mutable.
     ".claude/output-styles/soviet-engineer.md".source = ./claude/output-styles/soviet-engineer.md;

home/git.nix

@@ -74,6 +74,11 @@ in
         # `cz commit`, `git cz bump`, etc. `git cc` is a shortcut for the prompt.
         cz = "!cz";
         cc = "!cz commit";
+        # Structural (syntax-aware) diff, on demand. Set per-invocation via the
+        # environment rather than `diff.external`, which would also change what
+        # `git show` and `git log -p --ext-diff` emit for every caller.
+        # Takes the same arguments as `git diff`: `git dft HEAD~3 -- file`.
+        dft = "!GIT_EXTERNAL_DIFF=difft git diff";
       };
 
       # SSH signing, key from the registry. mkDefault so a host lacking the key
@@ -99,6 +104,14 @@ in
     enableGitIntegration = true;
   };
 
+  # difftastic backs the `dft` alias above. git.enable stays off on purpose:
+  # the module's git integration sets `diff.external`, which would displace
+  # delta as the diff renderer everywhere instead of only where asked.
+  programs.difftastic = {
+    enable = true;
+    git.enable = false;
+  };
+
   # lazygit: TUI for staging/rebasing, themed to Catppuccin Mocha to match.
   programs.lazygit = {
     enable = true;

home/shell.nix

@@ -26,8 +26,32 @@ in
     pkgs.tea
     pkgs.hyperfine # command-line benchmarking
     pkgs.sd # saner find-and-replace than sed
+
+    # Replacements for the classic coreutils/BSD tools. Only the read-only ones
+    # are aliased over the original name (see shellAliases below); the rest keep
+    # their own name so nothing changes shape under a script's feet. The alias
+    # map and the flag-compatibility differences are documented in
+    # ../docs/shell.md, "Replacing the classics".
+    pkgs.dust # du: tree-shaped, size-sorted disk usage
+    pkgs.dysk # df: mounted filesystems (duf is unmaintained upstream)
+    pkgs.procs # ps: process list with tree, ports and container columns
+    pkgs.trash-cli # rm: XDG trash; `trash` / `trash-list` / `trash-restore`
+    pkgs.doggo # dig: DNS lookups
+    pkgs.xh # curl, for interactive HTTP poking (curl stays for scripts)
+    pkgs.ouch # tar/unzip/7z/zstd: one command for every archive format
+    pkgs.jnv # interactive jq filter builder (jq itself stays for scripts)
+    pkgs.hexyl # hex viewer
+    pkgs.fq # jq for binary formats
   ];
 
+  # tldr pages: worked examples for a command, next to (not instead of) man.
+  # enableAutoUpdates defaults on and installs a tldr-update user timer, which
+  # keeps the page cache fresh -- without it `tldr` fails until first `--update`.
+  programs.tealdeer = {
+    enable = true;
+    settings.display.compact = true;
+  };
+
   # Resource monitor, themed Catppuccin Mocha to match the rest of the desktop.
   # btop does not bundle the theme, so vendor it from catppuccin/btop (pinned).
   programs.btop = {
@@ -137,6 +161,26 @@ in
       la = "eza --icons --git -la";
       lt = "eza --icons --git --tree";
       cls = "clear";
+
+      # Shadow the classics with their modern equivalents. Only read-only
+      # commands are shadowed: a wrong flag costs a retype, never data. The
+      # flag vocabularies are NOT compatible (`du -sh`, `df -h`, `ps aux` all
+      # fail here) -- see ../docs/shell.md, "Replacing the classics".
+      #
+      # Blast radius is bounded by where these live: shellAliases lands in
+      # .zshrc, so only interactive zsh sees them. Scripts, `sudo <cmd>` and
+      # anything exec'd by another program still get the real binary. To reach
+      # the original in an interactive shell: `command du` or `\du`.
+      cat = "bat --paging=never"; # bat is already the PAGER/MANPAGER
+      du = "dust";
+      df = "dysk";
+      ps = "procs";
+
+      # `rm` is deliberately NOT aliased to trash-put. Retraining `rm` to mean
+      # "recoverable" is a habit that follows you onto machines where it does
+      # not (every remote host, every root shell, every container), and trash
+      # semantics break down anyway on a different filesystem or on
+      # root-owned paths. Type `trash` when you want a trash can.
     };
   };
 

hosts/MacPro31/README.md

@@ -1,61 +0,0 @@
-# Mac Pro 3,1 (Early 2008) — install notes
-
-Flake host: `lyrathorpe-macpro31`. Desktop (`portable = false`, imports
-`../../modules/desktop.nix`). Files: `configuration.nix`,
-`hardware-configuration.nix`.
-
-## Hardware configuration
-
-`hardware-configuration.nix` here is the real config generated by
-`nixos-generate-config` on the machine. Root is an **LVM** logical volume
-(`/dev/mapper/MacPro-Root`, ext4); the ESP (vfat) and swap are referenced by
-UUID. The initrd carries `dm-snapshot` for the LVM root. Regenerate and commit
-if the disk layout changes.
-
-## Bootloader
-
-The Mac Pro 3,1 has **64-bit EFI**, so it uses **systemd-boot** (no GRUB/CSM
-shim). `canTouchEfiVariables = false` because Apple's firmware does not reliably
-accept `efibootmgr` NVRAM writes.
-
-Apple-EFI quirk: if the firmware boot picker does not show NixOS after install,
-either
-
-- uncomment `boot.loader.efi.efiInstallAsRemovable = true;` in
-  `configuration.nix` (installs the fallback `\EFI\BOOT\BOOTX64.EFI`), and/or
-- "bless" the ESP from macOS.
-
-Partition the disk GPT with an ESP (vfat).
-
-## Graphics
-
-The stock card varies between units — **ATI Radeon HD 2600 XT** or **NVIDIA
-GeForce 8800 GT**. No proprietary driver is hardcoded; Sway relies on in-tree KMS:
-
-- ATI Radeon HD 2600 XT → `radeon` (or `amdgpu`) KMS
-- NVIDIA GeForce 8800 GT → `nouveau` KMS
-
-These come up automatically. If a card needs forcing, set
-`services.xserver.videoDrivers` and/or add the module to
-`boot.initrd.kernelModules` for early KMS (see the comment in
-`configuration.nix`).
-
-## Networking
-
-Wired Ethernet via NetworkManager (from `desktop.nix`) — the Mac Pro has two
-gigabit ports.
-
-## Login
-
-Graphical login via a Wayland greeter — `greetd` running ReGreet inside the
-`cage` kiosk compositor — configured centrally in `../../modules/sway.nix` for
-every Sway host (gated on `features.swayDesktop.enable`). The greeter is forced
-to the Dvorak layout to match the console and Sway session. Set the user
-password (`passwd lyrathorpe`) after install, or the greeter cannot
-authenticate. Requires working KMS (radeon/nouveau — see Graphics).
-
-## Apply
-
-```sh
-sudo nixos-rebuild switch --flake .#lyrathorpe-macpro31
-```

hosts/MacPro31/configuration.nix

@@ -1,14 +1,20 @@
 # Apple Mac Pro 3,1 (Early 2008, dual Xeon Harpertown, x86_64). Desktop host:
 # shared graphical/wired options live in ../../modules/desktop.nix; only
 # host-specific settings are here. Install notes (EFI booting, GPU, partitions):
-# see ./README.md.
+# see ../../docs/hosts/macpro31.md.
 { ... }:
 
 {
   imports = [
     ./hardware-configuration.nix
+    ./nvidia.nix
   ];
 
+  # Dual quad-core Xeon (Harpertown/Penryn): SSE4.1 but no SSE4.2 or POPCNT,
+  # i.e. x86-64-v1. Declaring it here switches off the fleet flags that need a
+  # newer CPU -- currently features.claudeCode (see ../../modules/features.nix).
+  features.cpu.microarchLevel = 1;
+
   # The Mac Pro 3,1 has 64-bit EFI (confirmed by the owner), so boot via
   # systemd-boot like the MBP -- no GRUB/BIOS shim needed.
   boot.loader.systemd-boot.enable = true;
@@ -33,17 +39,9 @@
   # enabled in workstation.nix.
   hardware.cpu.intel.updateMicrocode = true;
 
-  # GPU note: the stock card varies between units -- ATI Radeon HD 2600 XT or
+  # GPU: the stock card (ATI Radeon HD 2600 XT / NVIDIA GeForce 8800 GT) has
-  # NVIDIA GeForce 8800 GT. Sway needs a working KMS/modesetting driver; do NOT
+  # been replaced with an NVIDIA Quadro P400. Driver, Wayland quirks and
-  # install a proprietary blob here. Depending on the installed card, rely on
+  # GPU-enabled Docker live in ./nvidia.nix.
-  # the open kernel driver:
-  #   - ATI Radeon HD 2600 XT -> "radeon" (older) or "amdgpu" KMS
-  #   - NVIDIA GeForce 8800 GT -> "nouveau" KMS
-  # These come up automatically via the in-tree drivers + KMS, and the graphics
-  # stack itself is enabled by modules/sway.nix. If a card needs to be forced, add it
-  # here, e.g. `services.xserver.videoDrivers = [ "radeon" ];` (or "nouveau"),
-  # and/or `boot.initrd.kernelModules = [ "radeon" ];` in
-  # hardware-configuration.nix for early KMS.
 
   # See `man configuration.nix` / the stateVersion docs before changing.
   system.stateVersion = "26.05";

hosts/MacPro31/nvidia.nix

@@ -0,0 +1,66 @@
+# NVIDIA Quadro P400 (Pascal, GP108) on the Mac Pro 3,1: proprietary driver for
+# the Sway desktop, plus Docker with GPU/CUDA access for containers.
+#
+# Driver branch: 580 (nvidiaPackages.legacy_580), NOT the nixpkgs default
+# (`production`, currently 595.x). 580 is the last branch that supports
+# Maxwell/Pascal/Volta -- NVIDIA keeps it as an LTS branch to Aug 2028 -- and a
+# newer branch simply will not drive this card.
+#
+# The driver is unfree, so it is not in the binary cache: the kernel module is
+# compiled locally. On this machine's 2008 Xeons expect the first rebuild after
+# a kernel bump to take a long while.
+{ config, ... }:
+
+{
+  # Selects the proprietary driver; the module blacklists nouveau/nvidiafb and
+  # loads nvidia-uvm (needed by CUDA) via modprobe softdep. Naming is historical
+  # -- this option drives the kernel/driver choice on Wayland hosts too, which
+  # is why it is set on a machine that runs no X server.
+  services.xserver.videoDrivers = [ "nvidia" ];
+
+  hardware.nvidia = {
+    package = config.boot.kernelPackages.nvidiaPackages.legacy_580;
+    # Required for Wayland: sets nvidia-drm.modeset=1 (and fbdev=1), without
+    # which wlroots gets no GBM device and Sway/cage fail to start.
+    modesetting.enable = true;
+    # The open kernel modules need Turing or later; Pascal must use the closed
+    # ones. Explicit because the option has no default on driver >= 560.
+    open = false;
+  };
+
+  # The NVIDIA module only puts these in boot.kernelModules when
+  # services.xserver.enable is true, which is false on this Wayland-only host --
+  # so load them explicitly rather than relying on udev modalias autoloading.
+  # nvidia_uvm (needed by CUDA) is deliberately absent: the module's modprobe
+  # softdep pulls it in after the GPU device exists, which is the supported
+  # ordering.
+  boot.kernelModules = [
+    "nvidia"
+    "nvidia_modeset"
+    "nvidia_drm"
+  ];
+
+  # wlroots refuses the proprietary NVIDIA driver unless told to proceed. The
+  # greeter's compositor (cage) has no such check; only Sway needs the flag,
+  # which the module bakes into the wrapper the session's .desktop file runs.
+  programs.sway.extraOptions = [ "--unsupported-gpu" ];
+
+  virtualisation.docker.enable = true;
+
+  # CDI-based GPU access for containers: generates /var/run/cdi specs from the
+  # host driver at boot and turns on Docker's CDI feature. Run GPU workloads
+  # with `docker run --device=nvidia.com/gpu=all ...`. The deprecated
+  # virtualisation.docker.enableNvidia runtime wrapper is deliberately not used.
+  hardware.nvidia-container-toolkit.enable = true;
+
+  # The generator needs a loaded kernel module: without one it aborts with
+  # "failed to initialize NVML: Driver Not Loaded". That is guaranteed after a
+  # kernel bump, where the rebuilt module cannot load until reboot -- and since
+  # the unit is requiredBy docker.service and wantedBy multi-user.target, the
+  # failure takes Docker down and makes `nixos-rebuild switch` exit non-zero.
+  # Skip the run instead when no driver is loaded; the toolkit's udev rule
+  # restarts the unit as soon as the nvidia device appears, so the CDI specs are
+  # still generated on the next boot.
+  systemd.services.nvidia-container-toolkit-cdi-generator.unitConfig.ConditionPathExists =
+    "/proc/driver/nvidia/version";
+}

hosts/PiZero2W/configuration.nix

@@ -0,0 +1,111 @@
+# Raspberry Pi Zero 2 W (aarch64) "Psion sidecar": an RS232 companion for a
+# Psion 5MX. Two roles, split into submodules: ./serial-ppp.nix (PPP over the
+# serial line, NAT out to wifi, telnet login) and ./email-proxy.nix (cleartext
+# POP3/SMTP front end for the Psion's mail client). The raspberry-pi-3
+# nixos-hardware profile (the Zero 2 W is the same BCM2837 SoC as the Pi 3) and
+# key-only sshd (../../modules/ssh.nix) are layered on in the flake host table.
+# Install notes: see ../../docs/hosts/pizero2w.md.
+{ lib, ... }:
+{
+  imports = [
+    ./hardware-configuration.nix
+    ./serial-ppp.nix
+    ./email-proxy.nix
+  ];
+
+  # Match the flake's nixosConfigurations attribute name so `nh os switch`
+  # (which selects by the local hostname) resolves without an explicit -H flag.
+  networking.hostName = "lyrathorpe-zero2w";
+
+  # Headless server: modules/sway.nix is not imported and
+  # features.swayDesktop.enable defaults to false, so this host keeps plain
+  # TTY/SSH login.
+
+  # Claude Code is a Node application. It runs on aarch64, but not usefully in
+  # 512 MB of RAM, and its closure is unwelcome on an SD card.
+  features.claudeCode.enable = false;
+
+  # 512 MB total and no swap partition -- SD cards wear out under swap writes.
+  # Compressed RAM swap instead; zstd is the best ratio-per-cycle the SoC can
+  # sustain.
+  zramSwap = {
+    enable = true;
+    algorithm = "zstd";
+  };
+
+  # The NixOS manual and man page index cost build time and a chunk of the card
+  # for a box that is administered over SSH from elsewhere.
+  documentation.nixos.enable = false;
+
+  # Own the firmware partition declaratively: every switch rewrites config.txt,
+  # the vendor device trees and the overlays below. Without this the card keeps
+  # whatever config.txt the flashed image wrote and the UART overlays never
+  # load. uboot.enable keeps the GPU firmware chainloading U-Boot -> extlinux,
+  # which is how the NixOS aarch64 SD image boots; leaving it off would rewrite
+  # config.txt without a `kernel=` line and the board would stop booting.
+  hardware.raspberry-pi.firmware = {
+    enable = true;
+    uboot.enable = true;
+  };
+
+  hardware.raspberry-pi.configtxt = {
+    settings.all = {
+      # Headless: hand the VideoCore the minimum and leave the rest to Linux.
+      # start_x/camera_auto_detect otherwise reserve VRAM for a camera stack
+      # this board does not have.
+      gpu_mem = 16;
+      start_x = 0;
+      camera_auto_detect = false;
+      # Left on, the firmware auto-loads the KMS display overlay, which wants
+      # more VRAM than this board can spare for a monitor it will never have.
+      display_auto_detect = false;
+    };
+
+    # Replaces the profile's default (vc4-kms-v3d), which is display hardware
+    # this host never uses.
+    deviceTreeOverlays.all = [
+      # Move the PL011 UART off Bluetooth and onto GPIO 14/15, so /dev/ttyAMA0
+      # is the RS232 header. The mini UART (ttyS0) derives its baud rate from
+      # the core clock and drifts at 115200.
+      { disable-bt = { }; }
+      # RTS/CTS on GPIO 16/17: the Psion's modem profile uses hardware flow
+      # control, and so does pppd in ./serial-ppp.nix.
+      { uart0.ctsrts = true; }
+    ];
+  };
+
+  # Wifi is the Pi's uplink and the route the Psion reaches the internet over
+  # (./serial-ppp.nix masquerades onto it).
+  networking.interfaces.wlan0.useDHCP = true;
+  networking.wireless = {
+    enable = true;
+    interfaces = [ "wlan0" ];
+    # PSKs stay out of the Nix store: wpa_supplicant reads them at runtime from
+    # this file, which is created on the device (root-owned, 0600) and contains
+    #   psk_home=<the pre-shared key>
+    # See ../../docs/hosts/pizero2w.md.
+    secretsFile = "/var/lib/wpa_supplicant/secrets.conf";
+    networks."CHANGE-ME-SSID".pskRaw = "ext:psk_home";
+  };
+
+  # The board takes a DHCP lease over wifi, so its address moves. mDNS makes it
+  # findable as lyrathorpe-zero2w.local instead of hunting through the router's
+  # lease table -- which matters most on first boot, when it is the only way in.
+  services.avahi = {
+    enable = true;
+    openFirewall = true;
+    publish = {
+      enable = true;
+      addresses = true;
+      workstation = true;
+    };
+  };
+
+  # Default-deny inbound. sshd opens 22 (../../modules/ssh.nix); everything the
+  # Psion talks to is reached over the PPP link, which ./serial-ppp.nix marks
+  # trusted.
+  networking.firewall.enable = true;
+
+  # See `man configuration.nix` / the stateVersion docs before changing.
+  system.stateVersion = "26.05";
+}

hosts/PiZero2W/email-proxy.nix

@@ -0,0 +1,25 @@
+# legacy-email-proxy: a cleartext POP3 (110) and SMTP (25) front end for the
+# Psion's built-in mail client, forwarded to authenticated IMAPS/SMTPS.
+#
+# The package, the systemd unit and its hardening all live upstream
+# (https://code.emmathe.dev/lyrathorpe/legacy-email-proxy); this host only
+# enables the service and points it at the credentials.
+{ inputs, ... }:
+{
+  imports = [ inputs.legacy-email-proxy.nixosModules.default ];
+
+  services.legacy-email-proxy = {
+    enable = true;
+
+    # The listeners are unauthenticated and unencrypted by design, so the
+    # firewall is what confines them: ppp0 is trusted, wlan0 is not, and 110/25
+    # are never opened there (./serial-ppp.nix). They stay on the default
+    # 0.0.0.0 rather than the PPP address because 10.0.0.1 exists only while
+    # the Psion is plugged in, and a bind-time dependency on a serial cable is
+    # a restart loop waiting to happen.
+
+    # Backend hostnames and credentials. Kept out of the Nix store: created on
+    # the device, root-owned 0600. See ../../docs/hosts/pizero2w.md.
+    environmentFile = "/var/lib/legacy-email-proxy/backend.env";
+  };
+}

hosts/PiZero2W/hardware-configuration.nix

@@ -0,0 +1,33 @@
+# PLACEHOLDER hardware configuration for the Raspberry Pi Zero 2 W.
+#
+# This file is NOT the real generated config -- it exists only so the host
+# evaluates in CI before the Pi is provisioned. The machine will not boot from
+# it as-is. On first install, regenerate this file on the device with
+#   nixos-generate-config --root /mnt
+# and replace this placeholder with the output (commit it). See ../../docs/hosts/pizero2w.md.
+#
+# Like every hardware-configuration.nix in this repo, this file is excluded from
+# the formatter and linters (see the pre-commit/treefmt excludes in flake.nix).
+{ modulesPath, ... }:
+{
+  imports = [ (modulesPath + "/installer/scan/not-detected.nix") ];
+
+  nixpkgs.hostPlatform = "aarch64-linux";
+
+  # The Zero 2 W boots from an SD card with a FAT firmware partition and an ext4
+  # root. Labels match the conventional sd-image layout; the real generated
+  # config will use by-uuid device paths instead.
+  fileSystems."/" = {
+    device = "/dev/disk/by-label/NIXOS_SD";
+    fsType = "ext4";
+  };
+
+  fileSystems."/boot/firmware" = {
+    device = "/dev/disk/by-label/FIRMWARE";
+    fsType = "vfat";
+  };
+
+  # 512 MB of RAM and an SD card: no swap partition (SD cards wear out under
+  # swap writes). zram takes its place; see ../../hosts/PiZero2W/configuration.nix.
+  swapDevices = [ ];
+}

hosts/PiZero2W/sd-image.nix

@@ -0,0 +1,44 @@
+# SD-card image of this host, used exactly once: to bring the board up.
+#
+# Deliberately NOT imported by ./configuration.nix. The flake extends the host
+# with it (see packages.aarch64-linux.zero2w-sd-image in ../../flake.nix), so
+# the card carries the host's own kernel, config.txt and SSH keys rather than a
+# generic installer that then has to be reconfigured over a console this host
+# does not have -- pppd owns the serial port (./serial-ppp.nix).
+#
+# It does not carry the runtime secrets. Seed those into the card's root
+# partition before first boot; see ../../docs/hosts/pizero2w.md.
+{
+  config,
+  lib,
+  modulesPath,
+  ...
+}:
+{
+  imports = [ "${modulesPath}/installer/sd-card/sd-image.nix" ];
+
+  # sd-image.nix pulls in profiles/all-hardware.nix, which is every driver and
+  # firmware blob NixOS knows about. The raspberry-pi-3 profile already carries
+  # what this board has, and the card is small.
+  hardware.enableAllHardware = lib.mkForce false;
+
+  image.baseName = "nixos-zero2w";
+
+  sdImage = {
+    # Compressing costs a long single-threaded pass and buys nothing: the image
+    # is written straight to a card with dd.
+    compressImage = false;
+
+    # The default 30 MiB does not hold the vendor GPU firmware, U-Boot and the
+    # BCM2837 device trees and overlays that nixos-hardware installs here.
+    firmwareSize = 128;
+
+    # The firmware partition is populated by nixos-hardware's firmware module
+    # (it takes over sdImage.populateFirmwareCommands); the root side is the
+    # stock extlinux install, which no longer arrives with it.
+    populateRootCommands = ''
+      mkdir -p ./files/boot
+      ${config.boot.loader.generic-extlinux-compatible.populateCmd} -c ${config.system.build.toplevel} -d ./files/boot
+    '';
+  };
+}

hosts/PiZero2W/serial-ppp.nix

@@ -0,0 +1,89 @@
+# The serial half of the Psion sidecar: a PPP link to a Psion 5MX over
+# /dev/ttyAMA0 (RS232 level shifter on the GPIO header, 115200 8N1 with
+# RTS/CTS), masqueraded out of wifi, plus a telnet login for the Psion's
+# terminal client.
+#
+# Cleartext telnet and unauthenticated PPP are safe *only* because the link is
+# a two-node cable: the peer is a machine from 1999 that speaks no TLS. Nothing
+# here is exposed to wlan0.
+{ pkgs, ... }:
+let
+  # Point-to-point addresses for the serial link; nothing else routes here.
+  piAddress = "10.0.0.1";
+  psionAddress = "10.0.0.2";
+in
+{
+  # pppd needs exclusive use of the port. NixOS starts a getty on any serial
+  # console named in boot.kernelParams; ttyAMA0 is not one today, but disable it
+  # explicitly so a later kernel-param change cannot silently steal the line.
+  systemd.services."serial-getty@ttyAMA0".enable = false;
+
+  services.pppd = {
+    enable = true;
+    peers.psion.config = ''
+      /dev/ttyAMA0
+      115200
+      ${piAddress}:${psionAddress}
+
+      # Hardware flow control, matching the Psion's modem profile.
+      crtscts
+
+      # A null-modem cable has no carrier detect and no peer to authenticate.
+      local
+      noauth
+
+      # The systemd unit is Type=notify, so pppd must stay in the foreground.
+      nodetach
+      lock
+
+      # Wait for the Psion rather than failing when it is unplugged, and keep
+      # waiting for the next time it is plugged back in.
+      passive
+      persist
+      maxfail 0
+      holdoff 1
+
+      # Hand the Psion resolvers over the link, so its Internet profile can set
+      # "get DNS from server = True" instead of hard-coding them.
+      ms-dns 1.1.1.1
+      ms-dns 8.8.8.8
+    '';
+  };
+
+  # The Psion's route to the internet. The original write-up used pppd's
+  # proxyarp instead; NAT keeps the Psion out of the LAN broadcast domain and
+  # does not depend on what the wifi router tolerates.
+  networking.nat = {
+    enable = true;
+    externalInterface = "wlan0";
+    internalIPs = [ "${psionAddress}/32" ];
+  };
+
+  # Everything the Psion connects to (telnet here, POP3/SMTP in
+  # ./email-proxy.nix) is reachable over the PPP link and nowhere else.
+  networking.firewall.trustedInterfaces = [ "ppp0" ];
+
+  # The Psion's terminal client speaks telnet over TCP, which it renders far
+  # better than the raw serial console. Socket-activated, one process per
+  # connection; busybox's telnetd in inetd mode hands straight over to login.
+  systemd.sockets.telnetd = {
+    description = "Telnet login socket for the Psion";
+    wantedBy = [ "sockets.target" ];
+    listenStreams = [ "${piAddress}:23" ];
+    socketConfig = {
+      Accept = true;
+      # ppp0 (and with it 10.0.0.1) only exists while the Psion is connected;
+      # FreeBind lets the socket be listening before that.
+      FreeBind = true;
+    };
+  };
+
+  systemd.services."telnetd@" = {
+    description = "Telnet login for the Psion";
+    serviceConfig = {
+      ExecStart = "-${pkgs.busybox}/bin/busybox telnetd -i -l ${pkgs.shadow}/bin/login";
+      StandardInput = "socket";
+      StandardError = "journal";
+    };
+  };
+}

hosts/RPi5/configuration.nix

@@ -2,7 +2,7 @@
 # ./docker.nix (Docker host with a network socket) and ./reverse-proxy.nix
 # (native nginx). The raspberry-pi-5 nixos-hardware profile (kernel, firmware,
 # device tree) and key-only sshd (../../modules/ssh.nix) are layered on in the
-# flake host table. Install notes: see ./README.md.
+# flake host table. Install notes: see ../../docs/hosts/rpi5.md.
 { ... }:
 {
   imports = [

hosts/RPi5/hardware-configuration.nix

@@ -4,7 +4,7 @@
 # evaluates in CI before the Pi is provisioned. The machine will not boot from
 # it as-is. On first install, regenerate this file on the device with
 #   nixos-generate-config --root /mnt
-# and replace this placeholder with the output (commit it). See ./README.md.
+# and replace this placeholder with the output (commit it). See ../../docs/hosts/rpi5.md.
 #
 # Like every hardware-configuration.nix in this repo, this file is excluded from
 # the formatter and linters (see the pre-commit/treefmt excludes in flake.nix).

hosts/T400/configuration.nix

@@ -1,6 +1,6 @@
 # ThinkPad T400 (NixOS). Shared laptop options live in ../../modules/laptop.nix;
 # only host-specific settings are here. Install notes (boot variants, GPU,
-# partitions): see ./README.md.
+# partitions): see ../../docs/hosts/t400.md.
 { config, ... }:
 
 {

modules/common-nixos.nix

@@ -25,6 +25,22 @@
   # toolchains, language-server downloads) on every NixOS host, not just WSL.
   programs.nix-ld.enable = true;
 
+  # Memory-safe sudo. The two modules assert against being enabled together;
+  # this one sets `security.sudo.enable = false` via mkDefault, so it is a
+  # straight swap and not an addition.
+  #
+  # Safe here because this fleet only ever uses the stock policy -- wheel may
+  # run anything, with a password -- which sudo-rs implements completely. It
+  # does not cover the more exotic sudoers surface (host aliases, LDAP/SSSD
+  # sudoers, most `Defaults` settings, `sudoreplay`); adding any of those means
+  # going back to `security.sudo`.
+  #
+  # Recovery if a host ever refuses to escalate: get a root shell without sudo
+  # (`wsl -u root -d NixOS` on the WSL box, the console or a serial/HDMI login
+  # elsewhere) and roll back -- `nixos-rebuild switch --rollback`, or pick the
+  # previous generation from the boot menu.
+  security.sudo-rs.enable = true;
+
   # Minimal system-level CLI available before the home-manager profile loads
   # (e.g. early boot / rescue). User-level tooling lives in home-manager.
   environment.systemPackages = with pkgs; [

modules/features.nix

@@ -6,7 +6,72 @@
 # headless host (e.g. the Pi) must be able to leave it at its default without
 # pulling in modules/sway.nix. The implementation lives in modules/sway.nix,
 # gated on this flag.
-{ lib, ... }:
+#
+# The file also carries the host capability facts those flags derive from
+# (features.cpu.*). features.claudeCode.enable is such a derived flag: it is
+# computed from the declared CPU level here and read by home/claude.nix through
+# home-manager's osConfig, so a machine that cannot run the tool never installs
+# it, on any host, without per-host opt-outs.
 {
-  options.features.swayDesktop.enable = lib.mkEnableOption "the Sway desktop";
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+let
+  cfg = config.features;
+
+  # Claude Code runs on Node, whose V8 build requires SSE4.2 and POPCNT -- the
+  # x86-64-v2 feature set. On an older x86_64 CPU it does not run (illegal
+  # instruction), so it must not be installed there.
+  claudeCodeMinLevel = 2;
+  claudeCodeSupported =
+    !pkgs.stdenv.hostPlatform.isx86_64 || cfg.cpu.microarchLevel >= claudeCodeMinLevel;
+in
+{
+  options.features = {
+    swayDesktop.enable = lib.mkEnableOption "the Sway desktop";
+
+    cpu.microarchLevel = lib.mkOption {
+      type = lib.types.ints.between 1 4;
+      default = 2;
+      example = 1;
+      description = ''
+        The x86-64 psABI microarchitecture level the host CPU implements:
+        1 = the original baseline, 2 = SSE4.2/POPCNT (Nehalem, 2008+),
+        3 = AVX2, 4 = AVX-512.
+
+        Nix cannot detect this (evaluation is pure and hosts are often built
+        elsewhere), so a machine older than the default declares its own level
+        and the flags below derive from it. Ignored on non-x86_64 hosts.
+      '';
+    };
+
+    claudeCode.enable = lib.mkOption {
+      type = lib.types.bool;
+      default = claudeCodeSupported;
+      defaultText = lib.literalMD ''
+        `true`, unless the host declares an x86-64 microarchitecture level
+        below ${toString claudeCodeMinLevel}
+      '';
+      description = ''
+        Whether to install Claude Code in this host's home-manager profiles
+        (implemented in home/claude.nix). Defaults off on CPUs below
+        x86-64-v${toString claudeCodeMinLevel}, which cannot run it; forcing it
+        on such a host is an evaluation error.
+      '';
+    };
+  };
+
+  config.assertions = [
+    {
+      assertion = cfg.claudeCode.enable -> claudeCodeSupported;
+      message = ''
+        features.claudeCode.enable is on, but this host declares
+        features.cpu.microarchLevel = ${toString cfg.cpu.microarchLevel}.
+        Claude Code needs x86-64-v${toString claudeCodeMinLevel}
+        (SSE4.2/POPCNT) and will not run on an older CPU.
+      '';
+    }
+  ];
 }

users/emmathorpe/work.nix

@@ -50,6 +50,19 @@
   ];
   services.ssh-agent.enable = true;
 
+  # Colourised kubectl. enableAlias points `kubectl` at kubecolor, which parses
+  # the output of the real kubectl underneath and passes anything it does not
+  # recognise straight through, so every flag and subcommand still works. It
+  # drops colour automatically when stdout is not a terminal, leaving pipes into
+  # grep/jq/yq byte-identical. zsh integration reuses kubectl's own completions.
+  # Note the alias does apply to `KUBECONFIG=... kubectl ...`: zsh expands
+  # aliases after a variable-assignment prefix.
+  programs.kubecolor = {
+    enable = true;
+    enableAlias = true;
+    enableZshIntegration = true;
+  };
+
   # gcx (above) keeps its OAuth tokens in the system keychain and has no
   # plaintext fallback, so this WSL box needs something owning
   # org.freedesktop.secrets. See home/secret-service.nix for why