CLAUDE.md

@@ -50,6 +50,15 @@ The domain model (Host, Module, Skeleton, Auto-loader, Enable convention, overla
   **No forge CLI is installed on the NixOS build.** No `gitea-axi`, no `tea`, no `gh` on `PATH` — the flake names `gitea-axi` only as the claude-code module's `SessionStart` hook command and never packages it, so that hook invokes a binary that is not there.
   Credentials, however, do exist: `~/.config/tea/config.yml` holds a token-bearing login named `alexion` (not `axi`), so pull requests **can** be opened with `nix run nixpkgs#tea -- pr create --login alexion --repo alexion/dotfiles --base main --head <branch> ...`.
   The `--repo` flag is required on that path, since `tea` resolves `origin` only for a login whose SSH host matches.
+  The same token reads PR discussion, which `tea` itself does poorly: `tea pr <n> --comments` prints only the body, and `-f comments` returns no comments field at all.
+  Use the API instead, taking the token from `.logins[] | select(.name=="alexion") | .token`.
+  Review comments are **not** at `/issues/<n>/comments` — that endpoint holds only top-level discussion and is usually empty.
+  Inline comments need two calls: `/pulls/<n>/reviews` for the review ids, then `/pulls/<n>/reviews/<id>/comments` for the bodies, whose `path` and `diff_hunk` fields say what each one is attached to.
+  A review row with an empty `body` is the normal shape when the operator left only inline comments.
+- SSH **host** keys (`ssh_host_<type>_key`, served by the daemon from `/etc/ssh` or a secret) are not user authentication keys (`~/.ssh/id_ed25519`, offered to a remote server).
+  The `ssh_host_` prefix is OpenSSH's own name for the former, and the `root@<host>` trailing field in a `.pub` is a free-text comment stamped by `ssh-keygen` at generation time, not a claim about which account uses the key.
+  On this machine the two are provably distinct: the daemon presents `SHA256:2ysuBX0+Z6GbdCTujz5JHX6rqnJzIyWhYNrxdhhGwEM`, while pushes to `git.alexion.dev` authenticate with `SHA256:nEhHwtHDnLlsuFxyfp+cETgHUZ8xDMxaPVmYM5vuCkA`.
+  Renaming host keys after user keys, or vice versa, is therefore always wrong.
 - `~/.claude/skills` is generated by home-manager with `recursive = true`, so the directories are real and writable but every leaf file is a read-only symlink into the store.
   Editing a skill in place fails; its source is `modules/claude-code/skills/<name>/` here, applied by a rebuild.
   Creating a new file under `~/.claude/skills/` succeeds silently and is the trap — it stays outside the repo and reaches no other machine.

hosts/neogaia/default.nix

@@ -1,19 +1,6 @@
-{
-  config,
-  inputs,
-  pkgs,
-  ...
-}:
+{ inputs, pkgs, ... }:
 # neogaia — Dell XPS 13 9380 laptop.
 # Disk layout is in ./disk.nix; `fileSystems` are derived from it, none declared here.
-let
-  # Read by the daemon at startup, so a re-key has to restart it to take effect.
-  sshHostKey = {
-    sopsFile = ../../secrets/neogaia.yaml;
-    mode = "0400";
-    restartUnits = [ "sshd.service" ];
-  };
-in
 {
   imports = [
     inputs.nixos-hardware.nixosModules.dell-xps-13-9380
@@ -40,24 +27,10 @@ in
   networking.networkmanager.enable = true;
 
   # So setup can be driven over the network.
-  services.openssh.enable = true;
-
-  # This host's SSH identity is restored from secrets.
-  # Reimaging the machine therefore keeps its fingerprint, and every client's
-  # `known_hosts` entry stays valid.
-  # The matching public halves are committed in plaintext, since publishing
-  # them is their purpose.
-  sops.secrets = {
-    ssh-host-ed25519-key = sshHostKey;
-    ssh-host-rsa-key = sshHostKey;
-  };
-
-  # An empty list is what stops the daemon generating keys of its own.
-  services.openssh.hostKeys = [ ];
-  services.openssh.extraConfig = ''
-    HostKey ${config.sops.secrets.ssh-host-ed25519-key.path}
-    HostKey ${config.sops.secrets.ssh-host-rsa-key.path}
-  '';
+  # The matching host public keys sit beside this file in plaintext, since
+  # publishing them is their purpose.
+  modules.ssh.enable = true;
+  modules.ssh.hostKeys.sopsFile = ../../secrets/neogaia.yaml;
 
   # fish as the login shell.
   modules.fish.enable = true;

modules/ssh/ssh.nix

@@ -0,0 +1,61 @@
+{
+  config,
+  lib,
+  ...
+}:
+# The OpenSSH daemon, serving host keys restored from secrets.
+let
+  cfg = config.modules.ssh;
+
+  secretName = type: "ssh-host-${type}-key";
+in
+{
+  options.modules.ssh = {
+    enable = lib.mkEnableOption "the OpenSSH daemon, with host keys restored from secrets";
+
+    hostKeys.sopsFile = lib.mkOption {
+      type = lib.types.path;
+      description = ''
+        Encrypted file holding this host's SSH host private keys, one entry per
+        key type, named `ssh-host-<type>-key`.
+
+        These are the keys the daemon presents to identify itself to connecting
+        clients, not keys used to authenticate anyone to a remote server.
+        Restoring them from secrets rather than generating them keeps the host's
+        fingerprint across a reimage, so every client's `known_hosts` entry
+        stays valid.
+      '';
+    };
+
+    hostKeys.types = lib.mkOption {
+      type = lib.types.listOf lib.types.str;
+      default = [
+        "ed25519"
+        "rsa"
+      ];
+      description = ''
+        Key types to restore, naming both the entries read from the encrypted
+        file and the algorithms the daemon offers. Dropping a type a client has
+        already pinned makes the host unrecognisable to it.
+      '';
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    services.openssh.enable = true;
+
+    # The daemon reads its host keys once at startup, so a re-key has to restart
+    # it to take effect.
+    sops.secrets = lib.genAttrs (map secretName cfg.hostKeys.types) (_: {
+      inherit (cfg.hostKeys) sopsFile;
+      mode = "0400";
+      restartUnits = [ "sshd.service" ];
+    });
+
+    # An empty list is what stops the daemon generating keys of its own.
+    services.openssh.hostKeys = [ ];
+    services.openssh.extraConfig = lib.concatMapStrings (
+      type: "HostKey ${config.sops.secrets.${secretName type}.path}\n"
+    ) cfg.hostKeys.types;
+  };
+}